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On-Board Electronic Control Systems of Future Automated Heavy

1. Analogue Pulse On off Hi Figure 13 Proposed utilization of data transfer solutions 4 Device related design aspects In this chapter the design challenges related to typical devices in the electronic control systems of automated mobile machinery are presented and discussed 4 1 Electrical power supply The electric power to an electronic control system is usually supplied by the same battery and alternator that supply power to the starter and lights of the machine at a minimum As the electrical system in a typical manually operated machine has become more complex more performance is also required of the batteries and alternators Nevertheless even the electric power supply of a modern manually operated machine may not be directly suitable for a control system that enables automated functionality 4 1 1 Alternator The control system of an automated machine has typically more electrical loads than its manually operated equivalent Therefore the maximum output power of a specific alternator will be reached more easily This typically occurs after the electrical system has been operated without the engine running discharging the battery With an automated machine this can be very common The control system may wait for communication from fleet management for example In research and development machines this is even more common due to firmware updates data logging sensor system calibration diagnostic
2. July 2 2004 Fluid Power Net International pp 587 598 C Walls Selecting an Operating System for Embedded Applications Mentor Graphics 2014 8 p W Whittaker Red Team DARPA Grand Challenge 2005 Technical Paper Defense Advanced Research Projects Agency August 2005 15p Available http archive darpa mil grandchallenge05 TechPapers RedTeam pdf 148 126 L Zhang T Okamawari amp T Fujii Experimental Analysis of TCP and UDP during LTE Handover Proceedings of the IEEE 75 Vehicular Technology Conference VTC Spring Yokohama Japan May 6 9 2012 Institute of Electrical and Electronics Engineers 5 p
3. Caywood et al filed an application as early as 1965 describing a hydraulic mechanical solution 18 Singh has conducted surveys on research over the recent decades Singh discusses the development of automation in earthmoving considering sensing modelling planning and control The focus in sensing is mainly on lidars Actuator and soil tool interface modelling are discussed Dig and dump planning are considered Free space motion control as well as digging control is covered 102 Hemami and Hassani have prepared an overview of autonomous loading A typical truck loading scenario is considered and the functional requirements are listed Although navigation and obstacle avoidance are mentioned the main focus is on excavation The challenges related to soil tool interface are debated and relevant previous research is summarized 48 Cannon describes an automated excavator that is developed for truck loading The excavator is able to observe the shape of the surrounding soil to decide where to dig Furthermore the trucks to be loaded are detected and the dump position on a truck is automatically chosen The excavator is able to move in case the dig and dump locations are different The excavator reaches roughly the operating speed of an expert human operator Although human assistance is needed the excavator may operate several hours independently The original machine is modified to support electrical control of the hydraulic system Therefo
4. Guide Mini box com 12 p Available http resources mini box com online PWR OpenUPS PWR OpenUPS hardware manual pdf K Peterson Red Team Too DARPA Grand Challenge 2005 Technical Paper Defense Advanced Research Projects Agency August 2005 15 p 86 87 88 89 90 91 92 93 143 Available http archive darpa mil grandchallenge05 TechPapers RedTeamToo pdf T Peynot J Underwood amp S Scheding Towards reliable perception for Unmanned Ground Vehicles in challenging conditions Proceedings of the IEEE RSJ International Conference on Intelligent Robots and Systems IROS St Louis MO October 10 15 2009 Institute of Electrical and Electronics Engineers pp 1170 1176 Available http db acfr usyd edu au content php 237 html publicationid 857 O Pfeiffer A Ayre amp C Keydel Embedded Networking with CAN and CANopen Copperhill Technologies Corporation Greenfield MA 2008 535 p P Pickel N Tarasinski O Peters amp C Schrank RT Ethernet communication between tractor and implement Networking and Communication for Automation in Agricultural Engineering Kaiserslautern Germany April 6 2011 VDI Max Eyth Gesellschaft Agrartechnik amp John Deere European Technology Innovation Center 36p Available https www vdi de fileadmin vdi_de redakteur_dateien meq_ _dateien Expertenforum JohnDeere 2011 04 06 03 Vortrag Pickel_RT Ethernet Communication between Tractor and Implement pdf P
5. J Ziglar H Bae T Brown D Demitrish B Litkouhi J Nickolaou V Sadekar W Zhang J Struble M Taylor M Darms amp D Ferguson Autonomous Driving in Urban Environments Boss and the Urban Challenge Journal of Field Robotics Vol 25 Iss 8 2008 pp 425 466 Available http www fieldrobotics org users alonzo pubs papers JEFR 08 Boss pdf User Datagram Protocol Internet Engineering Task Force RFC 768 1980 Available https www ietf org rfc ric768 txt User Guide for the PowerStream DC UPS 1212 5A DC DC UPS Controller PowerStream Technology 1 p Available http www powerstream com p 5 amp ups users pdf J Uusisalo A Case Study on Effects of Remote Control and Control System Distribution in Hydraulic Mobile Machines dissertation Tampere University of Technology Publication 960 2011 111 p S Vernersson E Kalpaxidou D Rylander Evaluation of Wireless Short Range Communication Performance in a Quarry Environment Proceedings of the International Conference on Connected Vehicles and Expo ICCVE Las Vegas NV December 2 6 2013 Institute of Electrical and Electronics Engineers pp 308 313 Available http www es mdh se publications 3419 Evaluation of Wireless Short Range Communication Performance in a Quarry Environment J Vilenius A Raneda amp K Huhtala Characteristics of teleoperated skid steered mobile machine Proceedings of the 3 FPNI PhD Symposium on Fluid Power Terrassa Spain June 30
6. The pressure controller of the variable displacement pump of the working hydraulic circuit was also replaced to achieve straightforward displacement control A fast proportional directional control valve was installed instead to control the displacement of the pump The valve was connected to a current controlled PWM output at the main PLC Eventually the performance of the Pentium M based LittleBoard 800 computer was considered to prevent testing of the most advanced controllers Moreover multicore support of the xPC Target real time kernel had been improved Therefore the LittleBoard 800 was replaced with a Core i7 based dual core Hurricane QM57 with a core clock frequency of 2 53 GHz The computer complies with EPIC Express specification 84 having smaller dimensions than the EBX compliant 29 LittleBoard 800 However the Hurricane QM57 requires an ATX style power supply with multiple regulated voltages and has horizontal 8P8C connectors for Ethernet Therefore a slightly larger enclosure had to be selected The conduction cooled EPIC Express board is equipped with a board sized heat spreader which was used for mounting the board Both computers can be expanded with PCI 104 boards but PC 104 support is not included in EPIC Express 84 Therefore a quad channel PCI 104 version of the CAN expansion board was installed Fortunately it was straightforward to also modify the previously developed xPC Target driver to support this version
7. V 24 V 28 serial Figure 20 Reference hardware architecture O module Wheel odometry I O module EE E On off valve Pressure sensor Wheel sensor 86 In this reference hardware architecture it is assumed that it is safe and sufficient to stall the diesel engine at emergency stop The status of the emergency stop is however also signalled via CANopen Joysticks sensors and hydraulic components with CANopen interface are applied However there are some exceptions If a group of pressure sensors is installed into a manifold it is feasible to choose sensors with analogue output and measure the signals with a CANopen I O module located next to the manifold The change in wire harness complexity is not significant The communication becomes more efficient as several signals are transmitted in a single CAN message The more sensors there are the more cost efficient this solution becomes since an analogue pressure sensor has lower cost than one with a CANopen interface Because the CANopen interface generally increases the size of a pressure sensor utilizing an analogue sensor is also feasible if the installation space for the pressure sensors is limited Hydraulic on off valves are also controlled by an I O module because on off valves with CANopen interface are not widely available A wheel odometry module and an IMU are placed in the low level control system although they are pose estimation sensors fo
8. an Intel Pentium M based computer at 1 5 GHz was used On both machines two horizontally scanning lidars were installed one for each travel direction The lidars have RS 485 interface which is not available in either of the embedded computers RS 485 Universal Serial Bus USB adapters are therefore used The AFS angle is measured with an encoder that has a CANopen interface Another encoder consisting of a toothed wheel and inductive sensors is mounted on the drive shaft One of the machines with the extra sensors is presented in Figure 4 76 Bucket Drive shaft encoder Figure 4 An automated mining machine with additional sensors 76 1 3 4 Electronic control systems in automated agriculture Automated functions in agricultural applications are a common research topic Commercial systems for farm tractors are also available Recent research has aimed at improving the performance of automated steering when the tractor is towing an implement that affects the yaw 24 dynamics of the tractor Derrick developed adaptive algorithms for automated steering control The algorithms were tested with a farm tractor which has hydraulic power steering The steering valve can be commanded over CAN Furthermore the tractor has a differential GNSS receiver that is designed for agricultural use supplied by the tractor manufacturer In addition automotive inertial sensors are installed to measure yaw rate and a linear potentiometer is installed to
9. differential GNSS receiver with integrated IMU wheel odometry input and data fusion is installed for coarse pose estimation Devices for low level actuator control are supplied by the original 12 V system of the vehicle For sensors and computing an auxiliary 24 V alternator battery pack and several voltage converters with power management functionality are installed An interface for external power supply is included Circuit protection and power distribution are arranged to ensure that no single protective device opening its circuit will produce a complete gap in the coverage area of the perception system The original cooling system of the vehicle is used for thermal control Computing is performed by ten Core2Duo based computers at 2 16 Ghz with 2 GB of random access memory RAM a 4 GB flash drive and a dual Ethernet interface supporting 1000BASE T Two 500 GB hard disk drives are included for data logging The computers are CompactPCl modules installed in a common chassis The computers are synchronized with a customized PPS adaptor board and communicate using the internet protocol suite 117 118 34 1 3 8 Summary The publications presented above describe several electronic control systems of automated machines and vehicles The level of automation ranges from automated steering to machines capable of operating independently several hours A typical system has lidars and cameras for perception a GNSS receiver and an IMU for pose estimatio
10. experienced mainly related to file system errors due to unexpected switch off of the embedded computers Therefore one of the methods presented in subchapter 4 1 4 has to be applied Comparing the control system presented above to the systems presented in Chapter 1 the key difference is the utilization of CANopen in the low level control system The generic CANopen devices and the well defined system management process improve life cycle manageability The smaller number of expansion boards in the embedded computers also has a positive effect 131 8 Conclusions Considering the first research question there are several possible solutions for on board networking of a machine The applicability of any communication technology however has limitations USB and IEEE 1394 are not widely available in robust sensors actuators and I O modules have short segment length and physical topologies that require switches or hubs Moreover developing software for USB or IEEE 1394 devices is not as straightforward as with the other networks and buses discussed There are no well established industrial connectors LIN and V 24 V 28 serial communication have a low network throughput and limited availability of devices Although the network throughput of CAN is not sufficient for all advanced sensors a CAN based general purpose protocol is a good choice for most devices of an electronic control system of a mobile machine for cost and availability reasons More
11. is a likely successor having the same application layer protocol 36 If minimal cycle time and 54 maximum protocol efficiency are required EtherCAT may be preferred Pickel et al experimented on both POWERLINK and EtherCAT and successfully demonstrated EtherCAT communication between a tractor and an implement 88 3 2 3 V 24 based serial link V 24 and V 28 recommendations specify a serial link that was originally designed to interface a teletypewriter with a modem The interface is often referred to as RS 232 according to the American national standard For compatibility reasons a V 24 V 28 compatible serial port was included in practically every personal computer till it was replaced by USB The V 24 V 28 interface is light to process and the hardware is low cost Therefore it is still common in embedded devices The serial interface is controlled by a universal asynchronous receiver transmitter UART UARTs do not have addressing or error detection apart from rarely used simple bit parity check Therefore proprietary serial protocols are common There are also several well established protocol specifications for certain applications A V 24 V 28 serial link has a point to point topology Therefore a computer typically has a separate serial port for each V 24 V 28 device in the system Maximum cable length depends mainly on the total capacitance of the cable V 28 specifies single ended signalling which is sensitive to interferenc
12. or communication protocols are often needed which results in more complex verification Whether the system is customized or off the shelf using a dedicated radio channel is critical If this aspect is neglected other radio signals may block the emergency communication If this occurs the emergency stop system has to stop the monitored machines These unintentional stops have to be minimized as they decrease productivity and in extreme cases may result in unauthorized bypassing of the emergency stop system Considering modularity emergency stop systems have the benefit of being independent of the rest of the control system This simplifies life cycle manageability in particular with solutions where the emergency stop system is implemented on a dedicated physical platform I O of the on board unit has to be considered The simpler interface the unit has the more likely an off the shelf replacement system will be available Nevertheless when designing the on board emergency stop circuit with commercial equipment it has to be considered whether the control system needs to distinguish the emergency stop from an intentional shutdown 4 9 Reference hardware architecture A reference hardware architecture is presented in Figure 20 integrating the device types discussed in this chapter by utilizing the data transfer solutions presented in Figure 13 The low level control system is distributed over CAN with CANopen protocol CAN is preferred to
13. protective enclosure often targeted at automotive applications Since automotive applications of MEMS IMUs are often related to drive stability control the sensor configuration may be insufficient for pose estimation While integrated mixed signal circuitry makes these devices accurate and easy to calibrate there are limitations in supported communication protocols and available output signals Unless an IMU has sufficiently configurable real time data processing external processing is required If the IMU has analogue outputs a mobile I O module or PLC can be used to measure the signals In many cases however there are limitations related to conversion frequency digital filtering or real time performance of networking For optimal pose estimation performance the inertial measurements must be accurately synchronized with other data 4 5 Measuring configuration state A machine typically has several controlled mechanisms often actuated by hydraulic cylinders The positions of these mechanisms need to be measured if closed loop position control is required Furthermore the measurements may be needed to improve the accuracy of other sensors In the case of a steering joint the measurement can be used to improve pose estimation performance 80 41 In applications where sensors are mounted on a suspended rig it may be feasible to measure the pose of the rig in relation to the machine frame Many mechanisms have a controlled joint angle S
14. sight to the machine Taking into account the operating conditions of a wheel loader two robust cameras targeted at machinery applications were selected One of the cameras was mounted high on the wheel loader to view the working area of the excavator The other was mounted on the stick boom of the excavator showing the bucket The installed cameras are shown in Figure 31 the one viewing the working area is on the left under the large plastic enclosure the one on the stick boom on the right The bucket camera was installed to give a detailed view for the remote operator but also to test the functionality and durability of the camera at an extremely demanding mounting location Both cameras are supplied directly from the battery system Because one of the cameras was mounted on the excavator an extra connector was added in the camera cable to be disconnected when removing the excavator Figure 31 Cameras on wheel loader and excavator stick boom Since the cameras output an analogue video signal and IEEE 802 11 wireless networking was considered most feasible for video transfer a 4 channel Ethernet video server with internet 122 protocol suite was installed on the wheel loader The server was located inside a compartment for protection against dust and rain The video server was configured to use Motion JPEG compression for minimal processing delay The first tests and demonstrations were carried out when the embedded computers shown in Fig
15. the AP Furthermore GNU Linux enables flexible routing and encryption of the data On the other hand more system maintenance is required Therefore applying an embedded computer running GNU Linux for wireless networking alone is not feasible The stereoscopic system was designed at the Department of Automation and Systems Technology at Aalto University The system was aimed to be easy to move between different machines and other research installations Since both cameras and the image processing computer are installed inside the enclosure all communication with the system is conducted via Ethernet In addition power supply from the battery system had to be connected The stereoscopic system was successfully changed between machines during the research However the DC DC converter that had been originally installed inside the enclosure had to be replaced because it did not have a wide supply voltage range and was compatible only with 24 V battery systems 7 11 2 Meeting requirements The CANopen based system with distributed I O proved to be a flexible platform for adding automated functionality the wheel loader and the excavator are fully controllable by the 129 LittleBoard 800 embedded computer over CAN In addition to communicating with the DM586 the LittleBoard 800 is also able to read sensor data directly from the messages sent by the I O modules Moreover with the CAN based system installing the excavator attachment requires connecti
16. 1 Life cycle manageability Applying any microcontroller to mobile machine applications has challenges regarding different life cycles The microcontroller ICs available at present are different from the ones that will be available one mobile machine life cycle later The software development tools for obsolete microcontrollers will not be supported The compatibility of these legacy development tools with new operating systems which also have shorter life cycles than mobile machinery is therefore uncertain Since the life cycles in mobile machinery can be a lot longer than those of an operating system of a computer the development tools must be actively supported and upgraded by the manufacturer Considering the development tool support alone it is important to assess the production prospects of different microcontroller models Some development tools or development frameworks are available for several microcontroller models of different manufacturers In this case the possible future transition to another microcontroller model will be more straightforward considering software development and maintenance 90 As stated above the chosen microcontroller model will eventually become obsolete Therefore it has to be possible to re design a pin compatible microcontroller board using a new microcontroller Most likely it will not be a problem to find a microcontroller with similar or better computing performance It is even possible to utilize a fi
17. 108 6 12 1 Control system modifications 0 eee eeeeeee cette ee eeeeetaeeeeeeeeeeteeeeaaees 109 6 12 2 Meeting requirement c cccccceeeeeeeeeeecceeeeeeeeeeeeeesaaaeeeeeeeeeeeeenaaaes 111 CASE 2 AUTOMATED EXCAVATION ccccccceeeeeeeeeeeeeeneeeeeseeneeeeeeeeneeeeeee 115 7 1 Functional objectives 1215s eect iehcaeitencestichonateietnnatliahconel eenadlie adaslatona ey 115 7 2 Construction of wheel loader ss c2 ccceccsasecheeesseteeeeisaceieassteeneeaveseeeesidieneeseneees 116 7 3 Construction of excavator scetesinrscncsscusti een cdeeeiartenedeesapietentreetstedenincteresd 117 7 4 Control system of wheel loade cccccceeeeeeeeeeeceeeeeeeeeeeeeeeeaeeeeeeeeeeteneas 117 7 5 Excavator control module 12 02 26 teil iactaneaenllawstesen eatnwdenidadan 119 7 6 Joint angle measurement ssssssseeseeesseererrrnrttsserrrrrrnnressrrrrnnrnnreeserrrnnnn nne 120 Lik a Ao Eo E EE E E Sena eed aa waa dda ead ees den aaa eae 121 7 8 Electrical power supply cericescen cataract ceaetiamnebeemiacenntrdertstedaremctyietsnegiaeiale 122 7 9 Automated excavation functions ssssseerereessererrrrrrressrrrrrrrnresserrrrrn n 123 7 10 Tests of automated ExcavatiOn ccceeeessssscceeeeeeeeeeessneeeeeeeeeeteeeesaaees 125 PAO Testsetupoei donina a let A tae A EE ANR 125 PAQ22 RESUS 228 VA ee a ee a EEE se a ee 126 7 11 PYISGUIS SIMs 3 Fcc AEE EEA TAEA E erat eae E SASE ETE 128 7 11 1 Control system modificat
18. 2 mm of the DIP specification 19 A mating socket can be made of two separate 20 pin single inline package SIP sockets For single prototype applications it is also possible to split a 40 pin DIP socket 2 5 mm holes were added to the corners of the board for additional fastening The outline of the board was designed to be 30mm by 60mm An assembled industrially produced board is shown in Figure 22 fet 71 4 Figure 22 An assembled microcontroller board 92 A block diagram of the microcontroller board is presented in Figure 23 Since the microcontroller operates from a power supply of 3 3 V but other circuitry on the board requires 5 V the power supply of the microcontroller is generated with a linear regulator A voltage supervisory circuit holds the microcontroller in reset state if the regulated voltage drops below normal range Voltage regulator 3 3 V Supply filtering Voltage supervisory circuit CAN transceiver Microcontroller Dual V 24 V 28 transceiver Ceramic resonator Figure 23 Block diagram of microcontroller board CAN and V 24 V 28 communication were considered essential in several applications Therefore transceivers for these interfaces were included in the microcontroller board The 56F8323 includes an on chip relaxation oscillator which can be used to generate the system clock The accuracy of the internal relaxation oscillator however does not meet the requirements of CAN proto
19. All the computers have an operating system based on Fedora Linux kernel and communicate over the internet protocol suite The communication with microcontroller modules that control steering and velocity is realized with CAN The hardware architecture is presented in Figure 9 85 116 125 em PC 104 Gigabit switch PC 104 i e 1 PLC 1 PC 104 l F PLC 2 INS GPS l l t PLC 3 Pentium M Pentium M Short range LIDAR 1 3 i Short range LIDAR 4 6 Pentium M Pentium M Velocity control Ethernet RS 232 Steering control RS 485 RS 422 Pentium M Parallel CAN Figure 9 Hardware architecture of Sandstorm adapted from 125 33 In 2007 DARPA organized the Urban Challenge which is the most recent DARPA competition where hardware architectures of control systems were developed for autonomous vehicles The most obvious update in control system hardware compared to the Grand Challenges is probably in the perception equipment for detecting other vehicles pedestrians road markings etc The sensors are generally the same as in the Grand Challenges but there are more of them As a result more software development and higher computing performance are required Furthermore all the networking and hardware architectures of the Grand Challenge vehicles are not flexible enough for adding this new equipment Leonard et al equipped
20. Association July 2012 8p Available http www nmea org Assets nmea_ introduces onenet pdf J Jansons amp T Dorins Analyzing IEEE 802 11n standard outdoor performance Proceedings of 2 International Conference on Digital Information Processing and Communications ICDIPC Klaip da Lithuania July 10 12 2012 Klaip da University pp 26 30 O Karhu J Vilenius J Uusisalo amp K Huhtala Developing intelligent hydraulic excavator Proceedings of Power Transmission and Motion Control Symposium PTMC Bath UK September 13 15 2006 University of Bath pp 265 274 Available http www bath ac uk mech eng files ptmc 2006 PTMC proceedings pdf O Karhu J Moya J Uusisalo amp K Huhtala Enabling autonomous functions on hydraulic excavator attachment Proceedings of the 10 Scandinavian International Conference on Fluid Power SICFP Vol 2 Tampere Finland May 21 23 2007 Tampere University of Technology pp 35 45 Available htto urn fi URN ISBN 978 952 15 3272 6 O Karhu J Uusisalo J Honkakorpi amp K Huhtala Autonomous Excavation Using Hydraulic Mobile Machine Retrofitted with Electronic Control System Proceedings of the 7 JFPS International Symposium on Fluid Power Vol 2 Toyama Japan September 15 18 2008 The Japan Fluid Power System Society pp 359 362 Available http jfps jp proceedings toyama2008 pdf p1 19 pdf A Kelly A Stentz O Amidi M Bode D Bradley A Diaz Calderon M H
21. Contribution of this thesis in relation to previous research 35 Example bus layout of CAN sinc cteerngionaieiteain gonad tatiautn oem etude 49 Adapters between M12 and 8P8C for panel installation 103 p 94 52 Proposed utilization of data transfer solutions ccccccececeeceeeeeeeeeeeeeeees 62 Two arrangements for deep discharge protection eeceeeeeeeeeeeeeeeeee 65 Workflow for specifying battery system voltage cc cceeeeeeetteeeeeeeeeeeees 67 Example of power cistributlon seta ctonccierteranencn teeter asad 68 Three solutions to protect sensitive devices from sudden loss of power 70 Arrangement with power management module without low power state 71 Challenges in obstacle detection with fixed single plane lidar 0 81 Reference hardware architecture ccceeeeeseseeceeeeeeeeeeeeeseneeeeeeeeeeeeneee 85 Features of a 56F8323 microcontroller 3 ecceeeeeeeeeeeeeeeeeeeeeeeeeeeee 91 An assembled microcontroller board ccceeeeeeeeeeeeeeeeenneeeeeeeeeeeeeeenaaees 91 Block diagram of microcontroller board eeeceeeeeeeeeeee eee eeeeteeeeeeeeeeeeeeee 92 A typical arrangement with an application specific board 0 0 00 93 Automated wheel loader ccccceceeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeees 98 COMIOISYSLSM AV OU sone oo cretat ea crc at ta a ear cet cater aad 99 Control system layout a
22. Device 2 Device 3 power status switch Device 1 12V unprotected power status Device 2 12V stand by Device 1 Device 3 Device 2 Device 3 Figure 17 Three solutions to protect sensitive devices from sudden loss of power The top diagram in Figure 17 shows power distribution with a UPS In this case the UPS is a separate device that has an external battery The power status is a digital bus that communicates at least three states main battery connected running on UPS battery and UPS battery almost fully discharged In the middle diagram a delayed main relay is utilized The power management module which is either a separate device or one of the PLCs of the control system monitors the position of the main switch The module outputs a power status signal that typically has two 71 states normal operation and initiate shutdown The latter becomes active when the main switch is opened After a set time the main relay is opened In this case the stand by power consumption of the power management module has to be extremely low as the module is never disconnected from the battery Moreover the module has to recover from its low power state when the main switch is closed again The bottom diagram is simple but sets special requirements for sensitive devices in this case the sensitive devices themsel
23. The modules need to tolerate the power supply from the 24 V system have CAN or Ethernet communication and support the emergency stop functionality when applicable To map the terrain for path planning tests Green uses a module that consists of three horizontally scanning lidars 42 Kelly et al research the performance of an autonomous vehicle in different challenging test environments Two generations of automated off road vehicles are developed The vehicles are 27 based on human operated all terrain vehicles that are modified to be electrically controlled The second generation of vehicles included an auxiliary generator for supplying the sensors and computers Pose estimation is performed based on encoders measuring steering angle and angular velocity of the engine a differential RTK GNSS receiver ground speed radar linear potentiometer measuring suspension travel and an IMU The perception system consists of several single plane lidars two stereo camera systems and several separate cameras some of them thermal In addition the vehicle has a pressure sensitive bumper Some of the lidars are rotated by an electric motor With slip rings for power and communication they are able to rotate continuously One of the rotated lidars is mounted on a controlled mast enabling negative obstacles to be detected from a distance In addition to the colour and thermal cameras used for terrain classification there are several cameras for direct teleop
24. University of Technology 2012 57 p in Finnish Transmission Control Protocol Internet Engineering Task Force RFC 793 1981 Available https www ietf org rfc ric793 txt Transputer Databook INMOS Literature number 72 TRN 203 02 3 ed 1992 515p Available http www transputer net ibooks 72 trn 203 02 tdata3rd pdf 146 111 112 113 114 115 116 117 118 UJA1023 LIN I O slave with automatic bit rate detection Application note NXP Semiconductors Literature number AN10704 April 2009 36 p Available http www nxp com documents application_note AN10704 pdf UJA1023 LIN I O slave Product data sheet NXP Semiconductors Literature number UJA1023 August 2010 49p Available http www nxp com documents data_sheet UJA1023 paf Universal Serial Bus 3 1 Specification 2013 Hewlett Packard Intel Microsoft Renesas ST Ericsson amp Texas Instruments 631 p Available http www usb org developers docs usb 31 102015 zip Universal Serial Bus Specification 2000 Compaq Hewlett Packard Intel Lucent Microsoft NEC amp Philips 622 p Available http www usb org developers docs usb20 docs usb 20 0702115 zip UPS25 Uninterruptible power supply and Ni Mh Ni Cd charger unit User s Manual RTD Embedded Technologies December 2012 45 p Available http www rtd com NEW_manuals hardware utilitymodules UPS25 BDM610020008E pdf C Urmson C Ragusa D Ray J Anhalt D Bartz T G
25. Wheel encoders 6 DGPS receiver 5 Ntrip module 4 Embedded odometry module 4 Remote control module with modem 3 AFS resolver 2 Joystick 1 Total 360 6 12 Discussion Since the machine was built in 2009 it has been utilized in several research projects and technology demonstrations Ahopelto et al have used the machine in power management research experimenting with operation at minimal rotation speed of the engine 7 Huova et al 109 have developed energy efficient multi actuator control with digital working hydraulic circuit 52 Tikkanen has experimented with the energy efficiency of displacement controlled working hydraulics 108 In addition automated path following short range remote control and digital working hydraulics have been demonstrated with the wheel loader at several industrial and academic events Since the first demonstrations several hardware changes have been made to the original control system as required by various research projects It is therefore possible to assess the actual flexibility of the control system 6 12 1 Control system modifications To measure the volume flow of the working hydraulic circuit for closed loop displacement control a volume counter was installed 108 The sensor outputs incremental signals that enable detecting of the direction of the volume flow The controller development was done utilizing the MicroAutoBox Therefore the sensor was connected to spare inputs on the MicroAutoBox
26. a specification for CAN with flexible data rate CAN FD has been released recently CAN FD networks can be built using the same cabling as CAN Messages are sent using the same arbitration phase as CAN with the same data signalling rates of up to 1 Mb s For data phase however the data rate can be higher up to 8 Mb s and the number of data bytes can be as high as 64 With these measures it is possible to achieve a much higher actual throughput Moreover as the length of the CAN FD bus trunk is only limited by the data signalling rate of the arbitration phase it is possible to choose the two data rates so that both the actual throughput and the bus length are increased If the flexible data rate is not used CAN FD hardware is compatible with CAN 32 46 Because CAN FD specification is rather new and there are new challenges regarding the physical implementation 47 there are no commercial transceivers supporting the highest flexible data rates yet 32 Since classic CAN controllers would reject messages with flexible data rate these controllers need to be disabled during flexible data rate communication Therefore systems with both classic CAN and CAN FD devices can have faster and more advanced firmware updates testing and debugging features etc but there is no improvement in throughput during normal operation It is however likely that standardization will change the behaviour of new classic CAN devices in the near future CAN FD mess
27. a subchapter below Wheel odometry can be implemented cost efficiently and accurately especially if the effect of wheel slippage can be taken into account in data fusion Simple Hall effect sensors can be applied Depending on the construction of the drive train and performance and reliability requirements several sensors may be needed If a toothed wheel and discrete Hall effect sensors are used two sensors need to be mounted at a proper distance from each other to generate incremental signals for direction indication In addition to using a separate toothed wheel it is possible to choose various components of the drive train with internal sensors for measuring the angular velocity The signal may be available over CAN but typically the electrical interface is similar to having one or two discrete Hall effect sensors The number of pulses per wheel revolution depends on the accuracy requirement For example if one pulse per 2 cm of travel is generated the frequency of the pulses is 500 Hz when travelling at 10 m s If the signal is measured with a conventional on off input and processed in software the input state has to be read at more than 1 kHz to detect every pulse With a typical mobile PLC it is not possible to run user application at sub millisecond intervals A dedicated pulse frequency input 79 is therefore required also available in I O modules A quadrature input for incremental signals however is not as common as a simple freq
28. and soldered Probably due to the industrial production the microcontroller board has proven to be reliable 95 Although all the applications of the microcontroller board have been related to academic research a similar approach could also make commercial control system development more efficient A similar microcontroller board could be used in prototyping new sensors for example The microcontroller family chosen in this case is also quite popular in commercial machine control and measurement modules Many of the research applications where the microcontroller board has been applied could have been implemented with small commercial microcontroller modules Most of these modules do not however include a CAN controller An Arduino module with the CAN shield 40 would have been a possible solution although larger more expensive and possibly mechanically less reliable On the other hand the variety of expansion boards shields makes the Arduino a good option In some of the applications a product like the CANopen Chip F40 17 could have been used but for most cases the fixed software would have been a problem 6 Case 1 Automated wheel loader An automated wheel loader with a flexible electronic control system was developed to be used as a generic research platform In this chapter the design and implementation of the electronic control system are presented Research applications utilizing the machine and meeting the requirements of m
29. art sensors and computers in mobile machine applications is not straightforward How to realize the electrical power supply for devices that cannot be supplied directly from the battery system of a mobile machine Which device types require extra protection against environmental conditions Which communication technologies to utilize when communicating with different device types taking life cycle manageability into account 35 How to interface devices that cannot be connected directly to mobile PLCs or I O modules Research and development projects involve interfacing new devices into existing control systems These devices have interfaces that are not present in the control system at all or not in a sensible location regarding the architecture of the control system In addition utilizing these devices may require harder real time calculation than possible in the control system How to interface a device like this into the control system of a mobile machine How to minimize the prototyping work when utilizing Customised microcontroller based devices as interfaces 1 5 Scientific contribution The scientific contribution of this thesis in relation to previously conducted research on mobile machinery is presented in Figure 10 The previous research on life cycle manageability of control systems is partially applicable to automated mobile machinery but does not cover the extra sensors and computers required for automated operation The published re
30. automated machinery It is likely that one communication channel has to be shared between the machines Therefore the available data rate of wireless communication is divided Moreover with communication protocols the overall ratio between payload and overhead data gets worse as the number of transceivers is increased A common communication channel is also required if the machines have to communicate directly with each other A fleet of automated machines may perform coordinated tasks or missions For this an automated machine has to have wireless communication and embedded computing that are compatible with the fleet management system This compatibility may for example require an on board embedded computer to have a specific operating system When a single automated machine operates in a closed environment with no dynamic obstacles collision prevention is straightforward to implement In a multi machine environment however the situation is more difficult One solution is that all the machines receive subtasks from a fleet management system that makes sure no two machines go too near each other When machines perform longer tasks automatically this is no longer feasible Instead the machines need to communicate their position to other nearby machines and adapt their operation accordingly This means that also manually operated machines need to have positioning and communication equipment Working sites also have dynamic obstacles like manual
31. automotive applications These lidars have signal processing optimized for tolerating undesirable reflections from rain snow and fog for example Furthermore they often have an internal heater for operation at low ambient temperatures There are however extra challenges when utilizing lidars in mobile machinery applications When the heater is active the power consumption of a lidar is increased heavily The light emitted by a lidar is reflected by dense dust and smoke It is however possible to decrease the effect by signal processing 86 Nevertheless a lidar should be mounted so that these obstructions are minimized during operation In mobile machinery applications on board lidar measurements are distorted by the movement of the machine especially without accurate pose estimation Even if the distortion can be cancelled the movement of the machine makes a fixed single plane lidar scan unintentional directions entering or exiting a slope for example results in scanning too high or too low for reliable obstacle detection as presented in Figure 19 There are several solutions to this problem however Several single plane lidars may be aligned for improved coverage 42 72 105 In this case the measurements of each lidar should be synchronized or have accurate time stamps A more integrated approach is to use a quad plane lidar 12 A single plane lidar may be actively aimed by a controlled pod 15 or a more advanced gimbal with activ
32. cable to the JTAG header of the board Because the devices are sometimes installed in hard to reach locations software updates via CAN would be useful This would require programming a small CAN bootloader firmware in all the microcontrollers The extra effort would however make updating more comfortable and save time in the long run On the other hand efficient in circuit debugging would probably not be possible over CAN It is also possible to update the software by replacing the entire microcontroller board with one containing the new software The dimensions of the microcontroller board have been small enough for all the applications The minimum enclosure size is typically limited by the panel connectors required to maintain the minimum degree of protection specified in Chapter 2 Therefore there has been no need to choose a larger enclosure because of the microcontroller board A compatible board can be designed using future microcontrollers New microcontrollers tend to require less and less board area On the other hand for pin compatibility it may become necessary to re design the board also for a larger device However by using four layer board and surface mount pin rows the microcontroller IC can cover a much larger area than the 56F 8323 Because the board suits diverse applications it was feasible to have a batch of them industrially produced Therefore the electronic components on the microcontroller boards are correctly placed
33. coarse satellite based augmentation systems SBAS can be utilized free of charge and are supported by most GNSS receivers while sub metre and more accurate services typically require a paid subscription and a receiver compatible with the particular service 4 4 2 Odometry Velocity measurements are often an essential part of pose estimation producing uninterrupted high bandwidth data There are several sensor types for measuring either actual ground velocity or the angular velocities of the wheels A ground speed radar can be used to measure the actual speed reliably in most conditions A radar communicates over CAN or a V 24 based serial link but pulse signal outputs are also common being compatible with traditional wheel odometry sensors A ground speed radar is however more expensive than wheel odometry sensors Furthermore a radar has to be mounted so that the conical beam towards the ground is entirely unobstructed In some applications this is not possible considering the mechanical construction of the machines and protection of the radar The simplest radar interfaces also output only the magnitude of the speed without indication of whether the machine is moving forwards or backwards Visual odometry on the other hand may be used to estimate the velocity in six degrees of freedom 6DOF The performance however depends on the texture of the site Other aspects of implementing machine vision in mobile machinery applications are covered by
34. enables remote access This is possible over a network or by plugging in an external system drive To enable this the boot sequence of the basic input output system BIOS has to be set up accordingly On some operating systems remote access is possible through a V 24 V 28 serial link Because of the modest data rate it is appropriate to use a simple text based terminal and transfer only sub megabyte files In this case it may be feasible to transfer larger files with removable mass storage typically a USB flash disk If there is a need to change the BIOS settings the V 24 V 28 serial link 76 may be the only option in addition to keyboard and display especially if the operating system does not start or permit remote access In research applications it is likely that remote access is needed frequently Depending on the installation location of a computer some of the physical interfaces discussed above should be made easily accessible even if they are not used in normal operation If the enclosure of the computer has to be opened to reach the connectors it also limits the environmental conditions where maintenance can be done Panel connectors with a sufficient degree of protection are therefore reasonable although they are often bulky and sometimes lead to choosing a larger enclosure Furthermore the panel connectors typically need a dust cap to maintain protection when they are not mated 4 4 Pose estimation Regardless of the appl
35. frame is not very steadily supported the controller gains have to be quite small to prevent the wheel loader from moving on the ground 7 10 2 Results The system was tested by first doing an excavation cycle manually and storing the required trajectory points Figure 36 shows the joint angle signals during the manual excavation cycle The vertical dash lines show the three trajectory points that were stored Between the stored points 1 and 2 the bucket is first filled using the bucket and stick cylinders and then moved over the emptying position using the boom and slew cylinders Between the stored points 2 and 3 the bucket is emptied using the stick and bucket cylinders Target 1 Target 2 Target 3 120 Angle 1 Time s Figure 36 Manual excavation cycle 127 Figure 37 shows an excavation cycle that includes the automatic emptying and return of the bucket The grey background indicates manual control The vertical dash lines indicate the instant when a move to target command is sent and the fixed lines indicate when the target is reached Target number 3 is actually not reached at all because the operator sends the command move to target 1 as soon as the bucket has emptied at 19 5 s Move to 1 Move to 2 Move to 3 Move to 1 I bucket 120 J ry D Cc lt 0 120 0 5 10 15 20 Time s Figure 37 Excavation cycle with automatic emptying In this case the control system
36. hardware architectures however are different and do not meet the requirements presented in Chapter 2 The systems that do meet the data rates listed in Table 1 do not tolerate the specified operating conditions or have poor life cycle manageability This is due to proprietary communication over internet protocol suite even in the low level control system and utilization of various expansion boards in embedded computers 7 Case 2 Automated excavation A small commercial skid steered wheel loader was modified for short range remote control in previous research 123 Three similar machines were built for various research projects and technology demonstrations The electronic control system was implemented with a robust commercial embedded computer with display and distributed I O modules The control system of two of the machines was then extended to support multi machine operation lidar based path following and stereoscopic real time video for remote operation Moreover a commercial backhoe excavator attachment was modified and interfaced with the control system In this chapter the functional requirements for the control system are listed and the implemented control system of the wheel loader and the excavator attachment is described The research applications of the machines are discussed and automated emptying of the excavator bucket presented in detail Meeting the functional requirements as well as the general requirements of modularity flex
37. have the same digital interface for all devices Due to application specific optimization many devices only have the interface that best suits the device type Therefore actual mobile machines with advanced automation include several digital buses and networks 3 2 1 ISO 11898 Controller Area Network CAN was originally developed for automotive applications Since the control systems and operating conditions of cars and mobile machines are alike in many ways CAN is nowadays the most common network in the distributed control of mobile machinery CAN cabling can be implemented at low cost as the only key parameter is a characteristic impedance of 120 Q 96 For most operating environments unshielded twisted pair copper cable is sufficient Care has to be taken however to minimize mismatches in characteristic impedance all over the network Typical mismatch problems are related to connectors and termination CAN controller ICs implement the data link layer of the OSI model according to 96 Most CAN controller ICs have a configurable data signalling rate up to 1 Mb s However not all devices can take full advantage of this feature An application layer protocol or the functionality of the device may require a certain rate Moreover the device may have a limited message processing capacity which either restricts the maximum data signalling rate or tolerates only low bus loads at high data signalling rates Because all the devices of a CAN nee
38. higher in class A Average much higher in class A Specify 12 V gt C Specify dual voltage p Specify 24 V D Figure 15 Workflow for specifying battery system voltage 68 Dual voltage in Figure 15 refers to a battery system that has two separate power supplies This can be implemented with two alternators one supplying a 12 V system the other supplying a 24 V system It is also feasible to have one alternator one battery and a heavy duty DC DC converter instead if the total power consumption is sufficiently low In this case the converter can be a simple voltage doubling or dividing power supply without voltage regulation unless most power is consumed by devices that require a regulated power supply Dual alternator systems are not common in commercial machines as these systems require more maintenance and more space However the solution is reasonable in a machine utilized as a research platform where various devices need to be tested and the delivery time or price of a high power device with an optimal supply voltage is not acceptable In most cases it is possible to concentrate the electrical load to a single battery For example if the result is a 12 V battery system the devices of class B are likely to have a low combined maximum and average power A power distribution system like this is presented in Figure 16 In this case the voltage regulating DC DC converter can be spec
39. loop controller for slew movement was used The operator was able to store the desired trajectory points and command the slew cylinder to follow them 64 The concept was then extended to all four cylinders which enables automatic emptying and return of the bucket for example 65 A block diagram of the excavator controller is shown in Figure 33 The presented controller software is run by the excavator control module of Figure 29 The joystick positions and commands for closed loop control are received from the DM586 embedded computer of the wheel loader in CANopen Process Data Objects PDO In addition the angular position PDOs transmitted by the inclinometers are received The valve control signals are produced with PWM outputs of the excavator control module In addition to closed loop control the valves can be open loop controlled according to the joystick positions The signals are processed according to parameters that can be set using the CANopen interface The excavator control module was programmed to estimate the required volume flow and request it from the DM586 embedded computer of the wheel loader in a PDO Furthermore the load sensing pressure of the proportional valve is transmitted to the DM586 embedded computer in another PDO To make the slew cylinder position available to the entire control system the excavator control module may also transmit the cylinder position in a PDO Because the inclinometers measure the angle relative
40. m although longer cables are possible in simple network layouts 49 A short haul IEEE 1394 network with more than two devices has to be daisy chained or branched using devices that have more than one port In addition since the cable shielding specification is quite complex the hardware cost of a network easily becomes high 49 The IEEE 1394 specification is targeted at indoor applications There is no well established industrial connector outside the specification either Therefore protected and robust plugs and receptacles no not mate in general unless they are of the same product series If data signalling rates above 393 216 Mb s are used a 9 pin Beta or bilingual connector is required Unfortunately there are no protected variants of these connectors commercially available In mobile machinery applications this means that both ends of a commercial Beta cable are likely to be routed through a sealed cable gland Since the 9 pin connectors are rather bulky diagonal typically 14 15 mm in relation to typical Beta cable diameter less than 7 mm 49 most cable gland manufacturers do not have a gland with a suitable clamping range It is also possible to choose the cable glands according to cable diameter and install one or both of the connectors after routing the cable Unfortunately installing the 9 pin connectors requires soldering or crimping A solution like this is not flexible or convenient considering assembly or maintenance Ano
41. machine was built spare parts can be manufactured according to original drawings by a number of subcontractors As the level of automation is increased electronic devices are required The machines are typically still designed to have life cycles of decades Because electronic components typically have much shorter life cycles there are new challenges in design production maintenance and spare parts service These challenges are even greater when the control system has devices that are not widely used in heavy machinery have neither standardized nor well established interfaces and may be available from only one manufacturer These devices may have originally been developed for the office environment service robotics factory automation or land surveying for example 18 Regardless of the level of automation it is common that several machines are operated at the same working site These machines can perform individual tasks or co operate In either case multi machine environments set new requirements for control systems of automated heavy machinery to maintain efficiency and safety In this thesis the design perspectives and challenges concerning control systems of automated heavy machinery are examined The applicability of various devices and communication technology related to automated functionality is discussed considering modularity and robustness The challenges related to different bus and network technologies and different types of
42. machines with a high level of autonomy communicate with a supervisor exchanging mission or task information The requirements for wireless data transfer depend heavily on the application In direct teleoperation control signals are transmitted in real time Therefore the delay of wireless communication has to be minimal In this thesis the maximum acceptable delay including the transmission of a control command and reception of a visual feedback is 100 ms If a video stream is not transmitted from the machine to the operator the required data rate of the wireless communication is low This can be the case if the operator is able to see the machine directly or the working site has a low latency camera system for direct teleoperation A wheel loader for example can be operated with four 5 bit control values transmitted every 100 ms requiring simplex communication with a throughput of 200 b s It is also possible that instead of a real time video stream the machine transmits sensor data and the machine and its environment are visualised to the operator with computer generated graphics It is however often safer and more convenient to use on board cameras The minimum acceptable video quality in this thesis is considered to be 320 by 240 pixels at 10 frames per second Utilizing H 264 compliant video compression a video stream of the minimum quality has a data rate of 192 kb s maximum 5 In direct teleoperation lost data does not need to be retra
43. master s thesis Tampere University of Technology 2007 47 p in Finnish J Honkakorpi MEMS based Motion State Estimation and Control of Hydraulic Manipulators dissertation Tampere University of Technology Publication 1219 2014 91 p Available http urn fi URN ISBN 978 952 15 3327 3 M Huova M Karvonen V Ahola M Linjama amp M Vilenius Energy efficient control of multiactuator digital hydraulic mobile machine Proceedings of the 7 International Fluid Power Conference IFK Vol 1 Aachen Germany March 22 24 2010 RWTH Aachen University pp 25 36 A H ltt J Saarinen A Maula amp A Halme A User Interface Framework for the Control of Component Based Multi Robot Systems Proceedings of GlIMnet 2010 Espoo Finland June 16 2010 Aalto University pp 19 24 54 55 56 57 58 59 60 139 Information technology Generic cabling Industrial premises International Organization for Standardization ISO IEC 24702 Geneva Switzerland 2006 79 p Information technology Open Systems Interconnection Basic Reference Model The Basic Model International Organization for Standardization ISO IEC 7498 1 Geneva Switzerland 1994 59 p Available http standards iso org ittf PubliclyAvailableStandards s020269 ISO IEC 7498 1 1994 E zip Information technology Telecommunications and information exchange between systems Local and metropolitan area networks Specific requir
44. measure steering angle 25 An embedded computer with PC 104 based modular hardware and a QNX real time operating system is used for implementing the controllers in real time The computer has two expansion boards one for CAN communication with the steering valve the other for measuring analogue signals from the IMUs and the linear potentiometer The embedded computer is located in an enclosure that protects against mechanical shocks and vibration The GNSS receiver is connected to the computer with a V 24 V 28 serial link 25 The CAN based communication between a tractor and an implement is specified in a well established standard ISO 11783 Backman studied how a decentralized and generic combined navigation system of a tractor and an implement can be realized using standardized communication A system for combined navigation was developed and tested The hardware architecture of the navigation system is presented in Figure 5 A combined seed drill was used as an implement The system was tested in two field tests with two different tractors towing the seed drill Both tractors accept steering curvature commands according to ISO 11783 and one of them also supports speed control 10 The drawbar of the seed drill is modified by adding an articulated joint that can be hydraulically steered The steering cylinder is controlled by an auxiliary valve of the tractor An inductive non contact sensor has been added to measure the angle of the contro
45. model and software development tools have become obsolete Although the presented microcontroller board is especially targeted at mobile machinery applications some of the benefits can also be achieved with commercial microcontroller modules 133 References 1 56F8300 Peripheral User Manual Freescale Semiconductor Literature number MC56F8300UM October 2007 620 p Available http cache freescale com files dsp doc user_quide MC56F8300UM padf 2 56F8323 56F8123 Technical Data Sheet Freescale Semiconductor Literature number MC56F8323 April 2007 140p Available http cache freescale com files dsp doc data_sheet MC56F8323 pdf 3 56F8323 Fact Sheet Freescale Semiconductor Literature number 56F8323FS May 2005 2 p Available http cache freescale com files dsp doc fact_sheet 56F8323FS pdf 4 ADIS16385 Six Degrees of Freedom Inertial Sensor Data Sheet Analog Devices Literature number ADIS16385 December 2011 20 p Available http www analog com static imported files data_sheets ADIS16385 paf 5 Advanced video coding for generic audiovisual services International Telecommunication Union H 264 Geneva Switzerland 2014 766 p Available https www itu int rec T REC H 264 201402 l en 6 M Ahopelto J Uusisalo amp K Huhtala Low level control system architecture for autonomous wheel loader Proceedings of the 12 Scandinavian International Conference on Fluid Power Tampere Finland May 18 20 2011 Ta
46. of 57 The eight position eight contact 8P8C modular connector that is used in these specifications has limited strain relief and poor protection against dust and water 20 Although many manufacturers refer to this connector as registered jack 45 RJ45 actual RJ45S and RJ45M specifications contain wiring configuration for telecommunication using a keyed version of the 8P8C connector 82 For 10BASE T and 100BASE TX there is an optional properly protected industrial connector a 4 pole M12 with D coding Coding refers to mechanical keying that prevents the common A coded 4 pole M12 sensor connectors from being accidentally mated with the D coded M12 Ethernet connectors for example The 8 pole A coded version of the same connector is used for 1000BASE T Even 10 Gigabit Ethernet is supported by several manufacturers with X coded 8 pole M12 connectors that are actually not included in the M12 specification of the International Electrotechnical Commission IEC Because of this some manufacturers prefer to call these CAT6A M12 connectors instead 21 51 pp 216 21 7 104 pp 78 80 These connectors are not specified for Ethernet by IEEE but especially the 4 pole version is strongly supported by several manufacturers of high protection rating Ethernet devices The 8P8C modular connector is however often the only option in an industrial device probably due to strong standardization and low cost With devices like this an extra enclosu
47. orientation and obstacle detection is done with two horizontally scanning radars one mounted on each end of the AGV The steering angles and angular velocities of the wheels are measured with encoders The computing platform is presented in Figure 1 27 20 The platform is modular at IC level consisting of 11 transputers 110 Furthermore there is a digital signal processor DSP for both radars and an on board computer for hosting the transputer network monitoring the vehicle and accessing the wireless link The transputers that are labelled T420 only perform integer arithmetic in the hardware while the T805s have floating point units FPU A special purpose interface card with 42 measurement channels is used to measure hydraulic pressures oil temperature bumper limit switches top deck load and diesel speed for safety and condition monitoring This functionality is independent of the rest of the control system Moreover every transputer has a separate status output that triggers an emergency stop if a software or hardware fault occurs Transputer technology is chosen because it enables flexible input output 1 0 configurations and there is software support for parallel processing on single and multiple processors Durrant Whyte states that the chosen transputer architecture makes both hardware and software development very efficient Unfortunately the project also demonstrates the short and unpredictable production life cycles of ICs tran
48. point is set earlier which results in maximum bus lengths shorter than specified 95 In general this is not good procedure because all the devices of the bus would have to be able to resynchronize to these inaccurately timed transmissions and compatibility with most application layer protocols is thereby lost The number of devices has a considerable effect on the bus length as well devices need to be spaced sparsely enough to keep the mismatch of the bus characteristic impedance low 22 If minor extra delays can be tolerated some of the limitations can be avoided by grouping devices into separate buses and using CAN switches 99 Figure 11 Example bus layout of CAN There are several application layer protocols that cannot usually be used in the same physical network SAE J1939 is the only CAN protocol generally supported by heavy duty diesel engine manufacturers Because J1939 was originally developed for trucks it does not cover the communication of a machine in general Therefore machines with such an engine often have one CAN for J1939 devices and another for controlling the hydraulic system for example 50 Some of the application layer protocols are designed to be more flexible CANopen and Common Industrial Protocol CIP are the most common general purpose CAN protocols CANopen specifications are maintained by CAN in Automation CiA In addition to general protocol specification CiA has defined profiles for several device ty
49. requires extra arrangements The wireless module includes a 2 port Ethernet switch with M12 connectors Therefore no additional switch is required with the current equipment The ports were connected to the embedded computer and the DGPS receiver as presented in Figure 26 The networking configuration was performed via a web browser interface quickly and easily The wireless module was configured to act as a wireless client establishing an encrypted connection to the on site wireless network The network has no Internet access simplifying security issues Instead of a wireless client the wireless module can be configured to operate as an AP This removes the need for fixed on site wireless infrastructure in simple applications 106 6 10 Emergency stop Automated travel tests were planned to be conducted without an operator on board Therefore a system with a dedicated wireless link was designed for independent emergency stop functionality The system was designed utilizing the generic embedded module to make the devices small and convenient to update The generic embedded module is used in two different modules a relay module and a button module The relay module is installed on the machine controlling the emergency stop signal that disables the outputs of the main PLC stalls the engine and activates the brakes The handheld button module consists of the microcontroller board an application specific board with button inputs a battery pack
50. single battery with either nominal voltage 67 Combined maximum power refers to the peak power consumption of all the devices of a class This is not equal to the sum of the device specific peak power consumptions unless the devices may actually operate simultaneously at full power Combined average power on the other hand is the average power consumption of all the devices of a class which is equal to the sum of the device specific average power consumptions Classify devices A 12 V from battery 24 V regulated B 24 V from battery 12 V regulated Estimate combined Estimate combined Estimate combined maximum power of maximum power of average power of class A and class B class A and class B class A and class B maximizing number maximizing number maximizing number of devices in class B of devices in class A of devices in class B Maximum much higher in class B Maximum much higher in class A Average much higher in class B Estimate combined Estimate combined C Specify 24 V gt average power of average power of class A and class B class A and class B maximizing number maximizing number Estimate combined of devices in class B of devices in class A average power of class A and class B maximizing number of devices in class A Average much higher in class B Average much
51. supported by the equipment to be installed in future projects than a 12 V system Since the electrical system of a research machine is frequently operated without the engine running a starter battery type that tolerates deep discharge was selected Two 12 V batteries were connected in series resulting ina 24 V system with a capacity of 75 Ah sufficient to power the electrical system for several hours without the engine running A 28 V alternator with a nominal output current of 60 A at 6000 rom had been mounted on the engine for prior tests The transmission ratio between the alternator and the engine is 2 6 Therefore the alternator is rotating at 2600 rom when the engine is idling at 1000 rom The maximum output current of the alternator at 2600 rpm is approximately 38 A The maximum continuous consumption of the electrical loads without actuating any hydraulic valves is estimated in Table 3 assuming the alternator output voltage is 28 V Therefore the total of 360 W corresponds to 13 A This indicates that at least 66 of the alternator output is always available for charging the batteries when the engine is idling It has to be noted however that unlike a typical machine the wheel loader has no lights A commercial equivalent of the machine has work lights and headlights rated at 330 W in total Only the embedded module used as the Ntrip client requires a 12 V power supply Since no optional devices were easily available a small DC DC conv
52. the control system is intended for short proof of concept demonstrations in gentle environmental conditions the hardware architecture containing several real time sensors with high data rates makes the project relevant to this study The forklift is modified from a commercial manually operated machine A photograph of the forklift is 22 presented in Figure 3 Although the original forklift has many of its functions electrically controlled mechanisms with electrical servo motors had to be designed and built for steering and braking The computation required for automated functionality is performed on four networked quad core laptop computers three on them located on top of the machine 105 a e J Figure 3 Proof of concept of an automated forklift 105 A GNSS receiver with an integrated IMU is included and wheel encoders are installed into the front wheels A sensor with CAN interface is added for measuring the tilt angle of the fork Encoders are used to measure the height and lateral position of the fork A total of 15 scanning lidars are used to measure objects around the forklift Six of them are mounted low angled 5 downward one facing forward under the chassis Five lidars are located on top of the forklift scanning more steeply downward Two of the lidars are installed on the fork for pallet detection and another two scanning vertically forward on the sides of the forklift 105 Four beamforming microphones are used
53. to 125 C due to the heat generated inside the enclosure On the other hand extreme winter applications may require operating temperatures as low as 40 C Mobile machines are used for diverse tasks Excavators and wheel loaders for example have several optional tool attachments Machines are operated in closed environments but also driven in public traffic The control system must not limit this flexibility even if automated functionality is added If a machine is designed to be fully automated or remotely operated the operator s seat and cabin can be left out However the option to drive or operate an automated machine manually from the operator s seat is often desired This is the case for example if a machine is driven on public roads between closed working sites or automated functionality is forbidden on some sites Manual driving may also be needed for maintenance 2 2 Automated functions and remote operation Manually operated machines have diesel engines working hydraulics and steering and braking systems that can be used to implement automated functionality They also have several sensors that can be used All requirements for actuators sensors and data transfer are however usually not met in manually operated machines 2 2 1 Requirements for actuation and sensing To enable remote and automated control an automated machine needs to have electrically controlled functionality Depending on which functions are automated
54. to gravity vector the controller calculates the difference between two inclinometers over a joint to obtain the joint angle according to 3 and 4 Obucket 93 02 3 stick 92 81 4 Since there are only three inclinometers the angle of the base boom is obtained directly from the signal of the inclinometer 1 As stated above this may cause an offset However if the wheel loader keeps steady the offset is not a problem considering this controller because the trajectory points have the same offset when they are stored 124 CANopen JOYSTICK POSITIONS _ Open loop processing CANopen command MOVE TO TARGET optional sign reversal volume PDO STORE POSITION input signal neutral zone flow PDO receive input signal rate of change transmit control curve shaping i dead band Sai alculate ONT ANGLES Target positions Ss total w SLEW CYL up to 15 Calculate joint BOSTON up volume PWM CONTROL flow angles VALUES ADC outputs TTT EOSTIONS OPEN LOOP CONTROL 123 CONTROL VALUES t SLEW CYL VALUES POSITION Scale L CANopen calculate control Choose inclinometer error signal cLosep Open loop PDO JOINT signals dead band _ Loop or closed receive ANGLES saturation SONUR loop control Figure 33 Excavator controller block diagram Because the inclinom
55. voltage range of the control system during glowing and starting the engine This is most likely to be a problem in 12 V systems where traditional applications have permitted the range of battery voltage to reach quite low For example the lowest voltage of a 12 V starter battery in a standardized cold cranking test is specified to be 8 4 V 69 Through reasons of size and cost it is possible that the desired cranking performance or tolerance of deep discharge is not met If the battery is not chosen according to these aspects the characteristics of the chosen battery have to be taken into account when designing the control system Both problems can be solved at system level or by choosing every component according to the characteristics of the battery At system level deep discharge can be prevented by using a protective device that triggers an alarm when the battery voltage drops too low If the alarm is ignored power is eventually switched off Likewise the drop in the battery voltage due to starting can be tolerated by using a separate battery or capacitor that supplies power during cranking or until the voltage of the main battery circuit has returned to an acceptable level The two arrangements for deep discharge protection are presented in Figure 14 The upper diagram shows a system with an external protector that can be a separate standalone device It is also possible to implement this functionality with a PLC that has suitable I O The sa
56. www can newsletter org engineering engineering miscellaneous 140528 can newsletter print_june 2014 EPEC 2024 Control Module Technical Document EPEC December 2009 36 p EPIC amp EPIC Express Specification PC 104 Embedded Consortium June 2008 18p Available http oc104 org wp content uploads 2015 02 EPIC Spec 3 0 pdf An Ethernet Address Resolution Protocol Internet Engineering Task Force RFC 826 1982 Available https www ietf org rfc ric826 txt Ethernet POWERLINK Communication Profile Specification Ethernet POWERLINK Standardization Group EPSG DS 301 Fredersdorf Germany 2013 356p Available http www ethernet powerlink org en downloads technical documents action open download download epsq ds 301 v120 communication profile specification no_cache 1 M Felser Real Time Ethernet Industry Prospective Proceedings of the IEEE Vol 93 Iss 6 2005 pp 1118 1129 38 39 40 41 42 43 44 137 M Felser Real Time Ethernet Standardization and Implementations Proceedings of the IEEE International Symposium on Industrial Electronics ISIE Bari Italy July 4 7 2010 Institute of Electrical and Electronics Engineers pp 3766 3771 P Ferrari A Flammini D Marioli amp A Taroni IEEE 1588 Based Synchronization System for a Displacement Sensor Network IEEE Transactions on Instrumentation and Measurement Vol 57 Iss 2 2008 pp 254 260 For a few dollars more CAN shi
57. 1 728 p Available _http cache freescale com files dsp doc ref_ manual DSP56800ERM pdf H F Durrant Whyte An Autonomous Guided Vehicle for Cargo Handling Applications The International Journal of Robotics Research Vol 15 Iss 5 1996 pp 407 440 Available http db acfr usyd edu au content php 237 html publicationid 549 136 28 29 30 31 32 33 34 35 36 37 H Durrant Whyte D Pagac B Rogers M Stevens amp G Nelmes An Autonomous Straddle Carrier for Movement of Shipping Containers IEEE Robotics amp Automation Magazine Vol 14 Iss 3 2007 pp 12 23 Available http db acfr usyd edu au content php 237 html publicationid 449 EBX and EBX Express Specification PC 104 Embedded Consortium June 2012 23p Available http oc104 org wp content uploads 2015 02 EBX EBX Express Specification v3 01 pdf Electrical characteristics for balanced double current interchange circuits operating at data signalling rates up to 10 Mbit s International Telecommunication Union V 11 Geneva Switzerland 1996 18 p Available https www itu int rec T REC V 11 199610 I en Electrical characteristics for unbalanced double current interchange circuits International Telecommunication Union V 28 Helsinki Finland 1993 10 p Available https www itu int rec T REC V 28 199303 I en B Elend CAN FD Impact on system design CAN Newsletter No 2 2014 pp 44 47 Available http
58. AE J1939 interface for control over CAN There is also a dedicated on off input for enabling and stalling the engine The engine complies with Stage III A and Tier 3 emission requirements A variable displacement pump from A4VG series by Bosch Rexroth was selected The pump has an internal proportional valve for displacement control The control valve is electrically actuated and controlled by integrated electronics There is a CANopen compatible interface for setting the target displacement and other parameters as well as reading diagnostic data including signals of internal sensors A dedicated on off input can be used to set the pump at zero displacement in case of emergency 101 Hub motors from MCR5 series by Bosch Rexroth were selected The motors have a parking brake a reduced displacement mode and two Hall effect sensors generating an incremental output for measuring angular velocity The parking brake and reduced displacement mode are hydraulically actuated and controlled by external on off valves These valves are controlled by the main PLC A sandwich type mobile proportional valve from M4 series by Bosch Rexroth was selected for steering and auxiliary hydraulics control Both spools of the valve have integrated control electronics with a CANopen interface In addition there are on off safety valves for enabling the main spools The coils of the safety valves are directly controlled by the main PLC A pin shaped angular resolver was fitted i
59. AN expansion board of the embedded computer in Figure 27 This solution is smaller has a lower hardware cost and minimal communication delays However replacing the embedded computer its operating system or the expansion board are challenges considering life cycle manageability due to driver support and expansion board availability The modifications that have been carried out Figure 26 and Figure 27 have not required any heavy redesign Having several CANopen compliant busses enables flexible I O sensor and actuator extensions utilizing vendor independent devices with uniform methods for configuration management Furthermore it is possible to add multiple mobile PLCs to distribute computation over CANopen Where the size real time performance or I O interfaces of commercial CANopen devices are not sufficient utilizing the generic embedded module presented in Chapter 5 is an efficient method New embedded computers and advanced sensor and actuator systems can be connected to the on board Ethernet An external switch however is required since there are no spare Ethernet ports There are commercially available replacements for most of the devices utilizing the generic embedded module Some devices however need more than one commercial device for replacement For example the valve drivers of digital hydraulics could be replaced with CANopen I O modules or mobile PLCs with 20 on off outputs An external output stage would be required however
60. E 802 3 compliant network controllers and achieve synchronization accuracy of 20 us for example 39 Some of the specifications that are implemented with standard Ethernet hardware are based on UDP but most of them replace the entire internet protocol suite with a real time protocol stack Conventional internet protocols are however supported as the real time protocol stacks have separate time slots for non real time communication 37 38 45 Many automation devices nevertheless still have only a standard Ethernet interface and support only the regular internet protocol suite Therefore it should be easy to add standard Ethernet devices into an industrial Ethernet system Unfortunately this is usually not the case The networks that use non standard hardware require a special bridge between the industrial and standard parts of the network A bridge is also needed with an IEEE 802 3 compliant industrial Ethernet if the firmware of the standard Ethernet devices in the system cannot be updated Most industrial Ethernet devices are not designed to tolerate the operating conditions of mobile machines However as the level of automation is increasing industrial Ethernet may well replace CAN in mobile machinery applications Due to relatively long machine lifecycles and small production volumes the industrial Ethernet protocols that are based on standard Ethernet hardware seem most applicable For example in CANopen dominated applications POWERLINK
61. EREEN TEKNILLINEN YLIOPISTO UNIVERSITY OF TECHNOLOGY 2 L Karhu oard Electronic Control Systems of Future a oe Julkaisu 1352 Publication 1352 Tampere 2015 Tampereen teknillinen yliopisto Julkaisu 1352 Tampere University of Technology Publication 1352 Otso Karhu On Board Electronic Control Systems of Future Automated Heavy Machinery Thesis for the degree of Doctor of Science in Technology to be presented with due permission for public examination and criticism in Sahkdtalo Building Auditorium S2 at Tampere University of Technology on the 4 of December 2015 at 12 noon Tampereen teknillinen yliopisto Tampere University of Technology Tampere 2015 ISBN 978 952 15 3636 6 printed ISBN 978 952 15 3649 6 PDF ISSN 1459 2045 Abstract The level of automation and wireless communication has increased in heavy machinery recently This requires utilizing new devices and communication solutions in heavy machinery applications which involve demanding operating conditions and challenging life cycle management Therefore the applied devices have to be robust and hardware architectures flexible consisting of generic modules In research and development projects devices that have various communication interfaces and insufficient mechanical and electrical robustness need to be applied Although this thesis has its main focus on machines utilized as research platforms many of the challenges are similar with commerci
62. Ethernet for better device availability in mobile machinery applications CANopen in particular is chosen for flexibility device availability and standardized configuration management process The data signalling rate of 1 Mb s meets the data rate requirements listed in Table 1 since the cameras and lidars with high data rate are not part of the low level control system Another CAN is reserved for J1939 communication which is the industry standard interface in heavy duty diesel engines High level control system GNSS receiver Monitoring camera Machine vision Lidar camera Ethernet switch s o Wireless IEEE 802 11 Embedded computer CAN Ethernet bridge Proportional valve Linear angular position sensor Joystick CANI CAN2 Low level control system Wireless radio modem Diesel engine Emergency stop PLC Pressure sensor 1 Mb s CANopen 250 kb s J1939 Ethernet 1 Gb s internet protocol suite Analogue signal On off or incremental signal
63. MEA 0183 interface has a rather low data signalling rate and inefficient message format GNSS receiver manufacturers have developed proprietary binary protocols especially for RTK use Receivers also have faster and more reliable interfaces for communication A SAE J1939 based NMEA 2000 interface is a well established way of implementing CAN communication into a GNSS receiver Several protocols mainly proprietary also exist for Ethernet 77 communication NMEA has released plans to extend NMEA 2000 with an NMEA OneNet specification which could become the universal protocol for GNSS communication over the internet protocol suite 61 In addition to outputting position data differential GNSS receivers are also able to receive the data for differential corrections The correction data is typically transmitted over a V 24 V 28 serial link with a protocol specified by the Radio Technical Commission for Maritime Services RTCM There are different versions of the RTCM protocol and a typical GNSS receiver firmware only supports some of them The required protocol version typically depends on whether the GNSS receiver is an RTK device or a code differential receiver If the correction service is provided via the Internet the data is usually transmitted as Networked Transport of RTCM via Internet Protocol Ntrip A differential GNSS receiver with an Ethernet interface therefore often has Ntrip client functionality Due to satellite orbit and clock error
64. Magazine Vol 9 Iss 1 2002 pp 20 28 Available http services eng uts edu au quangha Pdf papers IEEE RAM paf 138 45 46 47 48 49 50 51 52 53 Hardware Assisted IEEE 1588 Implementation in the Intel IXP46X Product Line Intel Literature Number 305068 March 2005 18 p Available http www intel com content dam www public us en documents white papers ixp46x product line hardware assisted ieee 1588 implementation paper pdf F Hartwich CAN with flexible data rate CAN Newsletter No 2 2012 pp 10 19 Available http www can newsletter org engineering engineering miscellaneous 140528 can newsletter print_june 2012 M M Hell The physical layer in the CAN FD world CAN Newsletter No 1 2014 pp 16 19 Available http www can newsletter org engineering engineering miscellaneous 140527_can newsletter print_march 2014 A Hemami amp F Hassani An Overview of Autonomous Loading of Bulk Material Proceedings of the 26 International Symposium on Automation and Robotics in Construction ISARC Austin TX June 24 27 2009 International Association for Automation and Robotics in Construction pp 405 411 Available http www iaarc org publications fulltext An Overview_of Autonomous Loading of Bulk Material pdf High Performance Serial Bus Institute of Electrical and Electronics Engineers IEEE 1394 New York NY 2008 906 p J Honkakorpi CAN bus based embedded inclinometer
65. Serial port was left out because it had been minimally utilized and would have required an expansion board or a USB adapter Since the dSPACE MicroAutoBox is relatively expensive it was removed from the machine to be applied to another research platform after the most intense development of the digital hydraulic controller was completed Because of the upgraded performance of the embedded computer the digital hydraulic controller was implemented utilizing it The angular potentiometers were connected to spare I O of the main PLC CAN 4 was connected to the embedded computer for communicating with the valve drivers CAN 3 was connected to the spare CAN of the embedded computer improving data logging capability Moreover having all the CANs available enables 110 computation to be more flexibly divided between the main PLC and the embedded computer if required in future It is for example possible to use the main PLC only as I O extension to the embedded computer However having the digital hydraulic controller implemented on the embedded computer has its drawbacks other software development utilizing the embedded computer may prevent the working hydraulics from being operated Removing the embedded computer for maintenance naturally disables the working hydraulics as well It has been planned therefore that a simplified controller would be implemented on the main PLC to be used as a backup This would however require CAN 4 to be also conne
66. a Gateaen eaceme 35 1 67 COMING OL MCS ISS ata cts sae cee ceate eae ek a ca al Ge ah nate E aaa gitanbl eta 36 2 APPLICATION RELATED REQUIREMENTS FOR ELECTRONIC CONTROL YO PEM See ten ian teers elt ee tte eles meio sa ete ee ean elke EO 39 2 1 SMOBIE IMACHINGEY eene e aa E eve dames S 39 2 2 Automated functions and remote operation c ccceeeeeeeeeeeeetteeeeeeeeeeeeee 40 2 2 1 Requirements for actuation and SENSING ccceeeeeeeeeeeeeeeeeeeeeeeeeeeaeees 40 2 2 2 Requirements for on board data transfer 2 0 0 0 cceeeeceseeeeeeeeeeeeeeeeeeeeees 41 2 2 3 Requirements for wireless data transfer cccececeeseeeeeeeeeeeeeeeeeeeaees 42 2 3 Multi machine environment ascccecceeieasiteen seleceen encod ennai aes 43 3 FEASIBILITY OF TYPICAL DATA TRANSFER SOLUTIONS sasoien 45 3 1 Non digital interfaces cccccccceeeeeeeeeecceeeeeeeeeeeeeeeeeeeeeeeeeeeeeneseeaeeeeeeeeeenea 45 3 1 1 Continuous analogue Signals cccceeeeeececeeeeeeeeeeeeesseeeeeeeeeeeeeenenaeaes 46 Sele PUISOSIQNAlS otenn aa a oils eed aa tes rere 47 3 2 Digital buses and networks siiecccceneee catiiue ctareureceed aaceiebecetelias ahnatedwenleeue 47 3 2 1 ISO 11898 Controller Area Network c cccceeeeeeeeeeseneeeeeeeeeeeeeesenaaees 48 3 2 2 IEEE 802 3 EINGriaet ac o20 cen bee iaceieigeeceiatgeci td opdous blaring tied erariecsteenins 51 3 2 3 W 24 based Serial JAK nrerin EE E EREKE 54 3 2 4 Local Interco
67. a vehicle with a perception system of 12 single plane lidars 15 automotive radars 5 cameras and a 64 plane lidar The aim was that all sensors communicate over Ethernet preferably with user datagram protocol UDP multicast to minimize network load Unfortunately most of the sensors do not have an Ethernet interface A serial server is used to collect the serial data from the single plane lidars and transmit it over Ethernet using the internet protocol suite The radars have a fixed automotive firmware and each requires a dedicated CAN Several adapters are used to interface these 15 CANs into Ethernet The cameras are connected to a computer that transmits compressed image data over Ethernet to other computers The computing is realized with a modular blade server system Considering the overall power consumption of the control system there is no suitable alternator with sufficient power rating Therefore a separate engine generator unit and uninterruptible power supplies UPS are used 72 Urmson et al developed a perception system with six single plane lidars a 64 plane lidar two automotive lidars two quad plane lidars five automotive radars and two cameras with a high dynamic range Most of the sensors have a fixed mounting Some of the lidars are pointed down for detecting lane markings as road paint is generally more reflective than road surface An automotive lidar and radar are mounted on a controlled pod on both sides of the vehicle A
68. ages will be ignored instead of being flagged invalid 32 71 This will 51 enable transmitting of real time signals over CAN FD in mixed systems To make the transition to CAN FD easier Lennartsson and Olsson propose an enhanced format that interleaves extra data bits inside classic CAN frames These frames would appear valid to all CAN controllers since the extra data bits are transmitted within a nominal bit time sufficiently before the bit sampling point 71 3 2 2 IEEE 802 3 Ethernet Ethernet is the most actively developed and supported local area network LAN technology The development started in the 1970s and the first Ethernet standard was published in 1985 by the Institute of Electrical and Electronics Engineers IEEE The first implementations used a thick coaxial cable as the physical medium Several new physical layers have been standardized since but most specifications have remained valid 57 In addition to ongoing strong development and standardization Ethernet has an extremely strong position in the office consumer and industrial markets IEEE standards for Ethernet cover the physical and the data link layer of the OSI model 56 57 Since Ethernet was originally developed for the office environment there are features that are not optimal for industrial applications not to mention mobile machines Nowadays the physical layer of Ethernet is often implemented according to 100BASE TX or 1000BASE T specifications
69. al machines The applicability of typical solutions for data transfer is discussed Controller area network with a standardized higher level protocol is proposed to be applied where data signalling rates above 1 Mb s are not required The main benefits are the availability of robust generic devices and well established software tools for configuration management Ethernet can be utilized to network equipment with high data rates typically used for perception Although deterministic industrial Ethernet protocols would fulfil most requirements the conventional internet protocol suite is likely to be applied due to device availability Sometimes sensors and other devices without a suitable communication interface need to be applied In addition device related real time processing or accurate synchronization of hardware signals may be required A small circuit board with a microcontroller can be utilized as a generic embedded module for building robust small and cost efficient prototype devices that have a controller area network interface Although various microcontroller boards are commercially available designing one for heavy machinery applications in particular has benefits in robustness size interfaces and flexible software development The design of such a generic embedded module is presented The device specific challenges of building an automated machine are discussed Unexpected switch off of embedded computers has to be prevented by
70. alatali A Gutierrez J Johnston S Harbaugh H Kato W Messner N Miller K Peterson B Smith J Snider S Spiker J Ziglar W Whittaker M Clark P Koon A Mosher amp J Struble A Robust Approach to High Speed Navigation for Unrehearsed Desert Terrain Journal of Field Robotics Vol 23 Iss 8 2006 pp 467 508 Available http www ri cmu edu publication view html pub id 5532 C Urmson J Anhalt D Bagnell C Baker R Bittner J Dolan D Duggins D Ferguson T Galatali C Geyer M Gittleman S Harbaugh M Hebert T Howard A Kelly D Kohanbash M Likhachev N Miller K Peterson R Rajkumar P Rybski B Salesky S Scherer Y W Seo R Simmons S Singh J Snider A Stentz W Whittaker J Ziglar H Bae B Litkouhi J Nickolaou V Sadekar S Zeng J Struble M Taylor amp M Darms Tartan Racing A Multi Modal Approach to the DARPA Urban Challenge Defense Advanced Research Projects Agency April 2007 25p Available http www ri cmu edu pub_files 2007 4 Tartan_ Racing padf C Urmson J Anhalt D Bagnell C Baker R Bittner M N Clark J Dolan D Duggins T Galatali C Geyer M Gittleman S Harbaugh M Hebert 119 120 121 122 123 124 125 147 T M Howard S Kolski A Kelly M Likhachev M McNaughton N Miller K Peterson B Pilnick R Rajkumar P Rybski B Salesky Y W Seo S Singh J Snider A Stentz W Whittaker Z Wolkowicki
71. and a robust radio modem The application specific board of the relay module is similar to the one in the remote control module In addition the board has a transistor that drives the emergency stop relay that is in series with the conventional emergency stop buttons of the machine There is also an input for a bypass switch which disables the wireless emergency stop The actual switch has two pairs of contacts One pair is used to bypass the relay The other pair signals the microcontroller board if the bypass is enabled The emergency stop button in the button module is also a double pole switch While one pair of contacts shuts off the power supply to the microcontroller and the radio modem the other signals the emergency stop to the microcontroller board In the button module the application specific board has an electrolytic capacitor that powers the button module for approximately 200 ms after the emergency stop button has been pressed After initial tests it was noted that an additional run wait function would streamline testing Therefore another button with momentary action was installed In addition to the button inputs the board has a voltage regulator a connector for the radio modem and outputs for LED indicators The software of the relay module transmits a repeating bit pattern to the button unit If the button unit does not reply with a correctly manipulated pattern within the period of the microcontroller watchdog the relay is d
72. ansmitted over Ntrip Code differential correction data is also broadcast on marine radio beacon frequencies by base stations in many coastal areas which may be utilized in some sites with a compatible receiver Due to the nature of ionospheric delay it is possible to meet the performance of a local base station by estimating the local correction data based on several more distant base stations Several overlapping grids of base stations with various densities have been implemented worldwide some publicly others privately maintained There are regional nationwide continental and worldwide grids that provide the differential correction service The communication from the grid servers to the GNSS receiver can be implemented on Ntrip over mobile network modems or via satellite The differential corrections via satellite are broadcast one way Two way 78 communication over mobile networks on the other hand often includes transmitting the position of the rover to the server typically in a NMEA 0183 compatible format This makes it possible to optimize the differential corrections for the neighbourhood of the rover resulting in improved accuracy The satellite broadcast corrections either leave the location dependent ionospheric effect to be estimated by dual band reception or provide a list of corrections for different areas of the grid The area division does not necessarily follow the locations of the physical base stations Publicly maintained
73. appold H Herman R Mandelbaum T Pilarski P Rander S Thayer N Vallidis amp R Warner Toward Reliable Off Road Autonomous Vehicles Operating in Challenging Environments The International Journal of Robotics Research Vol 25 Iss 5 6 2006 pp 449 483 Available https www ri cmu edu pub _files pub4 kelly alonzo 2006 _1 kelly alonzo 2006 1 pdf D Kwak J Mo amp M Kang Investigation of Handoffs for IEEE 802 11 Networks in Vehicular Environment Proceedings of the 1 International Conference on Ubiquitous and Future Networks Hong Kong June 7 9 2009 pp 89 94 68 69 70 71 72 73 74 75 76 141 A T Le Q Nguyen Q P Ha D Rye H Durrant Whyte M Stevens amp V Boget Towards Autonomous Excavation in A Zelinsky ed Field and Service Robotics Springer 1998 London UK pp 124 128 Lead acid starter batteries Part 1 General requirements and methods of test International Electrotechnical Commission IEC 60095 1 Geneva Switzerland 2006 53 p Leading Networking Solutions for Industrial amp Mission Critical Applications Belden 10 ed 2014 89 p Available http www belden com products catalogs upload Hirschmann Networking Catalog pdf K Lennartsson amp J Olsson How to use high bit rates in a CAN system Proceedings of the 14 international CAN Conference iCC Paris France November 12 13 2013 CAN in Automation 8p Available http www kvaser com
74. arge protection almost any battery type is suitable even without external circuitry Unfortunately this is usually not the case Regardless of whether the system level solutions described above are utilized controlling the power states of the electrical devices have to be considered The control system could for example command applicable sensors and actuators to a low power mode by default when the engine is stalled The devices that are sensitive to cranking could be treated similarly when the engine is started If some of these devices are needed during cranking they can be supplied by a boost type voltage regulator With these measures the battery life and operating time without the engine running are maximized Moreover the separate power supply to be used during cranking can be minimized if needed at all 4 1 3 Nominal battery voltage and DC DC conversion The nominal voltage of the battery system also has to be specified Depending on the type and size of the machine the electrical system of the manually controlled equivalent may be the only reasonable starting point There may be essential electrical actuators or sensors that are only 66 available for a 12 V system for example In general 24 V is a widely supported supply voltage in both automation and mobile machines apart from small machines with a 12 V system The use of automotive components also promotes a 12 V system A possible process of specifying the battery system vol
75. ation speed Proportional VANG A 50 800 b s target spool position GNSS receiver RTK 96 b 10 960 b s latitude amp longitude ick ee 30 b 50 1 5 kb s 3 axes Wheel P 16b 100 1 6 kb s single wheel ingar or angular 16b 200 3 2 kb s position sensor Pressure sensor 10 b 500 5 kb s MU 96 b 200 19 2 kb s 6 degrees of freedom Monitoring camera 320 by 240 pixels 10 192 kb s H 264 compression 5 Single plane lidar 270 scan at 0 25 17 3 kb 25 432 kb s interval distance only Machine vision camera 1920 by 1080 pixels 8 bit Bayer pattern 16 6 Mb 10 166 Mb s 42 In this thesis a typical control system of an automated mobile machine is assumed to have ten pressure sensors six proportional valves two joysticks and six linear or angular sensors Uncompressed digital video and two lidars are utilized for perception while compressed video is transmitted for direct teleoperation A GNSS receiver an IMU and wheel odometry of four wheels are used in pose estimation The data transfer of these devices including overhead must not cause more than 50 network load on board leaving bandwidth for distributed computation and devices to be added in further development 2 2 3 Requirements for wireless data transfer Remotely operated mobile machines need wireless data transfer to receive control signals from the remote operator This is clear in the case of direct teleoperation as described by Sheridan 101 However even
76. board J aa ILA Application specific board Enclosure Figure 24 A typical arrangement with an application specific board 94 Since the microcontroller board has only logic level inputs an application specific board has protective or biasing input circuitry Analogue inputs may also have amplifiers and external filtering circuitry Logic level outputs may control power driving transistors An application specific board may also include board mounted embedded sensors transceivers converters or mass storage devices 5 2 Discussion The microcontroller board has proven to suit research applications which is demonstrated by several applications presented in Chapter 6 and Chapter 7 The effort required in implementing an application has been reasonable devices with simple I O have been designed built into protective enclosures and programmed all by one person in less than one week Utilizing the microcontroller board has made application specific boards simple to design and quick and easy to build The software development with CodeWarrior has also been efficient due to reusing source code and utilizing the integrated Processor Expert tools including automatic code generation The automatically generated code however sometimes requires manual corrections Since the microcontroller software is written in C it can also be ported to other microcontrollers Updating the software of a microcontroller board requires connecting a programming
77. bucket telescope and auxiliary hydraulics outlet The valve has a load sensing port for measuring the maximum load pressure of the actuator ports A pressure transducer with current output was installed in this port In addition there are on off valves for 117 toggling between one and two pumps as well as locking the boom and bucket An electrically actuated pressure relief valve is used to control the supply pressure according to load sensing The rotation speed of the engine is controlled by an electrical actuator instead of the original mechanical accelerator cable There are quick couplings for the auxiliary hydraulics A multipole connector for electric supply and CAN has been added Therefore it is possible to extend the CANopen based control system to attachments 7 3 Construction of excavator The excavator attachment shown in Figure 28 is modified from Avant Backhoe 205 It has four hydraulic cylinders for slew boom stick and bucket movements The original mechanically operated valves have been replaced like the ones of the wheel loader An excavator control module has been designed utilizing the generic embedded module The control module can be configured to compensate the typical nonlinear characteristics of proportional valves for example 63 The proportional valve has integrated current amplifiers The amplifiers are controlled with a voltage signal The range of the signal is proportional to the battery voltage The amplifi
78. cations without other traffic or dynamic obstacles The setup work at a new site was to be minimized The sites were assumed to be rather flat possibly without any landmarks and mostly have a line of sight to navigation satellites Therefore a GNSS receiver and wheel odometry possibly with inertial measurements were considered to be a sufficient sensor combination Since there is no sensor for solving the initial orientation of the machine a short path has to be driven to enable orientation estimation from successive position estimates 6 7 1 GNSS receiver Based on the accuracy requirement a code differential receiver was considered sufficient An interface for various external sources of correction data was required A Trimble SPS351 104 differential GPS DGPS receiver with a Trimble GA530 antenna was selected In addition to receiving GPS satellite signals SBAS correction data is also received This includes the European Geostationary Navigation Overlay Service EGNOS Furthermore the receiver and the antenna are compatible with the correction data transmitted on marine radio beacon frequencies The receiver and antenna are targeted at marine applications in demanding environmental conditions Therefore no additional protection is required The receiver has diverse options for communication Internet protocol suite over Ethernet was chosen for transmitting the position data to the embedded computer since processing the UDP packets is st
79. ces An SPI is therefore mandatory unless the performance of the microcontroller enables SPI implementation in software Many sensors are available only with analogue signal outputs The microcontroller board must therefore have analogue voltage inputs The input range has to be at least 0 2 V to avoid noise problems Moreover the input range must not exceed 0 5 V It is then possible to measure the common voltage and current ranges without losing ADC resolution by choosing suitable external resistors The ADC must have a resolution of at least 10 bits Since the natural frequencies in mobile machinery are quite low a conversion frequency of 10 kHz is considered sufficient The board may also be used to produce control signals for actuators Therefore hardware generated PWM outputs are mandatory unless the performance of the microcontroller enables PWM generation in software Applications include integrated digital circuits different types of switches indicators relays and on off valves For these devices general purpose inputs and outputs GPIO are needed Preferably logic levels of both 3 3 V and 5 V should be supported Some pins on a microcontroller package 89 can usually be configured for two or more different functions This flexibility must not be restricted by the design of the microcontroller board Since the board has to be universal and easy to use it has to operate from a single positive voltage supply Moreover the connect
80. ch can be utilized for controlling the power supply to device 3 directly pee main relay Power manager 12V b ge e power status ee oo re t Device 1 Device 2 Device 3 main switch Figure 18 Arrangement with power management module without low power state 72 4 2 PLCs and I O modules Mobile PLCs and modular I O systems have replaced mechanical pilot controls in many manually operated machines As stated in Chapter 2 an automated machine needs to have electrically controlled functionality This can be implemented with similar PLCs and I O modules such as modern manually operated machinery There are however some extra requirements typically the control system of an automated machine has more sensors and more closed loop control Even if the number of sensors is not increased higher sampling rates and resolutions may be required from ADCs There is typically more on board communication between PLCs I O modules sensors and actuators Furthermore the allowed communication delay may be smaller and more accurate synchronization of events may be required To meet the requirements the devices may need to be grouped into several physical networks 4 2 1 I O modules As the number of sensors actuators and networks is increased more analogue and digital I Os are needed and more complex hardware architectur
81. cing prototype devices with a distributed control system The design process of the embedded module is presented in Chapter 5 In addition to designing and implementing the embedded module applying the module on devices presented in Chapter 6 and Chapter 7 are contribution of the author apart from developing the real time algorithm for wheel odometry Demonstration of the above contributions in two experimental automated machines Designing and implementing the control systems presented in Chapter 6 and Chapter 7 are partial contribution of the author The excavator control module in particular and its control software demonstrated in Chapter 7 are developed and experiments conducted by the author Comparison of the control systems with the proposed reference hardware architecture is presented in the end of Chapter 6 and Chapter 7 1 6 Outline of thesis In Chapter 2 the requirements for control systems of automated mobile machinery are presented The characteristics of mobile machinery the required sensor and actuator interfaces communication and properties of multi machine environments are discussed The feasibility of different solutions for data transfer is discussed in Chapter 3 These include the typical buses and networks an automated machine has on board 37 In Chapter 4 the challenges linked to different types of devices required in automated machinery are discussed Devices for embedded computing pose estimation and percept
82. cols that specify a late sampling point for maximum bus length CANopen and J1939 for example Some applications also require more accurate timing Therefore an external frequency reference can be used Because of size optimization a high accuracy ceramic resonator was preferred to quartz crystal To maximize available GPIO both transceivers and the ceramic resonator can be left out if they are not used Solder pads for zero ohm resistors were included for bypassing the omitted transceivers Since the 56F8323 has only well established digital interfaces PWM outputs GPIO and analogue voltage inputs all vacant signal pins of the microcontroller were connected directly to the board to board connectors as illustrated in Figure 23 93 The microcontroller has an IEEE 1149 1 compliant interface for programming and _in circuit debugging The interface is commonly referred to as JTAG according to the original developer Joint Action Test Group An Enhanced On Chip Emulation EOnCE module that can be accessed through JTAG is included in the microcontroller for debugging in real time An 8 pin header is placed on the microcontroller board for accessing the JTAG EOnCE interface Software development is done with CodeWarrior development tools The latest versions are based on the Eclipse open development platform which has also been adopted by several other microcontroller manufacturers 5 1 3 Application specific board Using the microcontroller b
83. cted to the main PLC Simple proportional controllers could be implemented with the generic embedded module also inside the valve drivers In that case the access to CAN 4 would be required for transmitting target velocities or flow values from the main PLC to the valve drivers Running the digital hydraulic controller on the embedded computer has endorsed safer methods for developing the xPC Target models the default standalone model on the system drive of the embedded computer has to be reliable and stable especially concerning the controller for the working hydraulics Testing new controllers has to be done with a host laptop by running the loader model on the embedded computer from a USB drive Furthermore the new standalone models have to be tested thoroughly from a USB drive before changing the default standalone model on the system drive It was not possible to connect the volume counter sensor to the main PLC because there are no compatible inputs for incremental signals Therefore a module very similar to the one utilized in wheel odometry was developed utilizing the generic embedded module The signals were connected to the quadrature decoder inputs of the microcontroller board The microcontroller was programmed to read the difference register of the quadrature counter every 5 ms and transmit both the raw value and a low pass filtered value over CAN The volume counter module was connected to CAN 4 for communication with the embedded compu
84. ctions Embedded computer LittleBoard 800 i Motion control yes do Embedded computer with display Axiomatic DM586 Sensors actuators wireless Radio modem 1 O module Ultracom UC800 Axiomatic MIO24 Embedded computer LittleBoard 800 Video server Axis 241Q Engine start stop control module Camera L NET FO134SC Attachment Excavator control module CAN 250 kb s CANopen Ethernet 100 Mb s internet protocol suite IEEE1394 400 Mb s Inclinometer V 24 V 28 38 4 kb s Figure 29 Control system layout For manual operation on board the machine has a steering wheel a joystick and a gas pedal all outputting a voltage signal The signals are measured by two generic CANopen slave I O modules In addition the outputs of the hydraulic pressure transmitters wheel odometry sensors and the position sensor of the engine actuator are connected to the I O modules The modules control the hydraulic valves directly and the engine actuator through a separate H bridge board Because the control system of the machine was originally designed for direct teleoperation the odometry sensors were not intended for closed loop velocity control Therefore the odometry sensors do not indicate the direction of travel and the conventional pulse counter inputs of the CANopen I O module
85. d 2003 45 p Road vehicles Controller area network CAN Part 2 High speed medium access unit International Organization for Standardization ISO 11898 2 Geneva Switzerland 2003 21 p Road vehicles Controller area network CAN Part 4 Time triggered communication International Organization for Standardization ISO 11898 4 Geneva Switzerland 2004 32 p H Saha Some Methods to Improve Life Cycle Manageability of Low Volume Mobile Processing Platforms dissertation Tampere University of Technology Publication 899 2010 175p Available http urn ti URN NBN lt fi tty 201005121126 Sensor Actuator Cabling and Industrial Plug in Connectors Phoenix Contact 2013 656 p Available https www phoenixcontact com assets downloads ed global web dwl promotion 4 HK FV 13 EN LR pdf T Sheridan Telerobotics Automation and Human Supervisory Control The MIT Press Cambridge MA 1992 393 p S Singh State of the Art in Automation of Earthmoving 2002 Proceedings of the Workshop on Advanced Geomechatronics Japan October 2002 Sendai University 19p Available http www ri cmu edu pub _files pub4 singh sanjiv_ 2002 1 singh sanjiv 2002 1 pdf 103 104 105 106 107 108 109 110 145 Smart Network Infrastructure Intelligent Network Solutions Vol B 1 HARTING January 2013 106 p Available http www harting com fileadmin harting documents Ig hartingconnectivitynetworks service
86. d an optimal development platform for real time software for the first research projects and demonstrations Therefore the embedded computer and its expansion boards were required to be supported by xPC Target Based on experience of xPC Target in a laboratory environment a single core Pentium processor operating at over 1 GHz clock frequency and with 2 MB of L2 cache was considered to have sufficient performance for the first path following application A Pentium M based LittleBoard 800 with a 1 4 GHz clock frequency was selected The chosen model can be operated without a cooling fan over a wide range of ambient temperatures The computer complies with Embedded Board eXpandable EBX specification 29 with a PC 104 Plus expansion bus There are two Ethernet interfaces one of them implemented with a controller supported by the xPC Target A PC 104 expansion board with two CAN interfaces was installed Unfortunately very few CAN expansion boards are supported by the xPC Target A PCAN PC 104 from PEAK System Technik was chosen due to previous experience in developing an xPC Target driver for an expansion board from the same product series Since the source code of Linux drivers was available and the board is based on widely used CAN controller ICs the extra effort required by the driver development was reasonable The LittleBoard 800 can be powered from a regulated 5 V supply Depending on the boards installed in the PC 104 Plus bus additional re
87. d capacitor One solution is to use a UPS that continues to supply power from its battery when the main battery is disconnected There are UPS devices with both internal and external batteries A UPS monitors the external supply voltage and the charge level of its battery When either of these drops below a set limit the devices supplied by the UPS are signalled It is therefore not mandatory to start the shutdown process immediately when the main battery is disconnected The protected equipment can for example monitor a set time whether the main power is restored UPSs are available as computer expansion boards and separate devices 84 115 120 A UPS expansion board is feasible when a single embedded computer is the only sensitive device in the control system Moreover in research use one embedded computer may be moved between different control systems and test setups In this case it is a clear advantage if the computer has an internal UPS When several devices are to be protected a separate UPS is a feasible modular solution To minimize hardware and maintenance costs it is also possible to protect sensitive devices without an extra UPS battery Different solutions are presented in Figure 17 70 12V unprotected uE main battery UPS 12V power status 12V stand by Hie UPS battery Device 1 main manager Power
88. d industrial sensors actuators PLCs and embedded computers can be added by extending the original networks either directly or by standardized I O modules Connecting similar equipment to embedded computers through expansion boards would lead to higher dependency on software and driver support and board availability from a smaller number of vendors 5 Generic embedded module Since automated applications require new types of devices for sensing actuation and communication the devices have inputs outputs or communication interfaces that cannot be connected to mobile PLCs or I O modules This applies to state of the art technologies in particular but also devices that are not originally targeted at mobile machinery applications Although some devices may be connected directly to an embedded computer it is not feasible considering real time performance or the aim for modularity and flexibility The low level control system of the reference hardware architecture presented in Figure 20 has three devices that involve these challenges State of the art inertial sensors or IMUs are not available with a CANopen interface Optimal performance of wheel odometry requires a programmable device capable of sub millisecond processing of four incremental sensor inputs Emergency stop PLC needs to communicate through a radio modem Implementing efficient half duplex communication requires processing of a V 24 V 28 serial port at sub millisecond accuracy In this c
89. d to have the same data signalling rate this limitation alone may require dividing the devices of a system into several CANs To utilize high bus loads careful message scheduling is required 43 The main limitation with CAN is the maximum data signalling rate of 1 Mb s Therefore in a control system with several closed loops the data transfer capacity of CAN is often insufficient Another problem in some control applications is that the common CAN protocols are not deterministic a message with a higher priority may cause extra communication delay at any time This can be 49 avoided to some extent by careful node configuration and synchronous message transmission 16 A deterministic time triggered communication has been specified 98 but not widely implemented so far When CAN is operated at 1 Mb s the maximum bus length is only 25 40 m 16 97 Since the bus topology requires short stubs the trunk may become surprisingly long An example of this is illustrated in Figure 11 Moreover these distances can be reached with late bit sampling points only The chosen application layer protocol specifies the sampling point and thus maximum tolerance for the oscillator For example CANopen specification for sampling point is 75 87 5 of nominal bit time 16 For size or cost optimization a system can be designed with devices that have more inaccurate oscillators To enable sufficient resynchronization jumps in such conditions the sampling
90. d wheel loader 6 2 Control system architecture For robustness flexibility and product range CAN with CANopen was chosen as the main network technology To enable future extensions with sensors and multiple embedded computers communicating at high data rates Ethernet with internet protocol suite was also included Furthermore on board Ethernet makes it possible to utilize well established wireless standalone solutions In addition CAN with SAE J1939 and V 24 V 28 compatible serial communication with navigation related protocols were applied where neither CANopen nor Ethernet were available The layout of the control system is presented in Figure 26 The devices are divided into three levels based on function The bottom level in the diagram consists of sensors and actuators and possible sensor or actuator specific real time signal processing In addition a joystick a display and modules for wireless communication are considered to be on the bottom level The middle level includes the hardware for real time control of steering velocity and working hydraulics The target values for the middle level are generated either directly by the on board or remote operator over the equipment on the bottom level or by the embedded computer for automated functionality on the top level of the diagram 99 Automated functions Embedded computer LittleBoard 800 Motion control Digital hydraulics controller Main PL dSPACE MicroAutoB
91. design is not sufficient for an application Since the PLC is targeted at mobile machinery applications the issues related to mechanical and electrical robustness are minimized In addition to CAN communication the PLC is used to measure analogue signals from pressure and temperature transducers and control the pump of the working hydraulics via an electrically actuated proportional pressure relief valve Auxiliary functions of the PLC include parking brake and front attachment lock control The PLC performs power management velocity and steering control and data routing to the embedded computer for automated functionality 6 4 Power train and steering To meet the velocity and traction performance of commercial machinery with similar structure the diesel engine was required to have a maximum power output of 100 kW For convenient electrical control and modularity a CAN interface was preferred for setting target engine speed Hydrostatic transmission with an electrically controlled variable displacement pump and four hub motors was considered a suitable generic solution for testing different control strategies and hydraulic circuits For steer by wire functionality an electrically actuated mobile proportional valve was specified to control the AFS cylinders To simplify control system layout and increase modularity hydraulic components with CANopen interface were preferred A 44 CWA diesel engine from Agco Power was selected The engine has a S
92. devices are reviewed Two examples of an on board control system of automated heavy machinery for multi machine environment are presented and discussed 1 2 Scope of thesis The control systems of automated heavy machinery discussed in this thesis are primarily for research and development but also applicable to commercial future machinery to a great extent The discussion applies to autonomous machines but also more common applications where the control system performs operator assisting functions remote monitoring or data logging The term mobile machinery is used in this thesis to describe wheeled and tracked heavy machinery typically equipped with either a fixed tool or a removable attachment The discussion in this thesis applies to mobile machines in particular The mobile machines that are presented as examples of automated heavy machinery in Chapter 6 and Chapter 7 are designed and built for research and development They are operated in closed environments under immediate human supervision The machine safety required of commercial machinery by legislation is not considered in this thesis Although the machines of the presented automated machinery cases are research platforms they have much in common with commercial mobile machines This applies to operating environment maintenance and upgrades for example Therefore many of the results are also applicable to designing the control systems of commercial automated mobile machine
93. downloads ethernetcatalogue Version 19 6 B Smart Network Infrastructure Intelligent Network Solutions 19 6 Cabling pdf Smart Network Infrastructure Intelligent Network Solutions Vol B 2 HARTING January 2013 100p Available http www harting com fileadmin harting documents Ig hartingconnectivitynetworks service downloads ethernetcatalogue Version 19 6 B Smart Network Infrastructure Intelligent Network Solutions 19 6 Cabling pdf S Teller M R Walter M Antone A Correa R Davis L Fletcher E Frazzoli J Glass J P How A S Huang J H Jeon S Karaman B Luders N Roy amp T Sainath A Voice Commandable Robotic Forklift Working Alongside Humans in Minimally Prepared Outdoor Environments Proceedings of the IEEE International Conference on Robotics and Automation ICRA Anchorage AK May 3 8 2010 Institute of Electrical and Electronics Engineers pp 526 533 Available http dspace mit edu openaccess disseminate 1721 1 62144 S Terho Using stereo cameras in MaCl Proceedings of GiMnet 2010 Espoo Finland June 16 2010 Aalto University pp 46 51 S Terho Building and sharing the cognition model of the environment with collaborative service robots dissertation Aalto University Publication Aalto DD 104 2011 2011 123 p Available http urn fi URN ISBN 978 952 60 4332 6 R Tikkanen Using Displacement Control and Hydraulic Energy Storage in Working Hydraulics of a Wheel Loader master s thesis Tampere
94. e Therefore especially long cables have to be shielded V 24 V 28 devices have quite low data rates The V 28 recommendation covers data signalling rates only up to 20 kb s 31 but devices supporting up to 115 2 kb s are common nowadays In any case the maximum data signalling rate has to be checked for each device separately A point to point serial link can also use differential signalling according to V 11 specification 30 also referred to as RS 422 The specification enables longer cables and higher data signalling rates Similar transceivers can also form a half duplex multi point network as specified by ISO IEC 8482 59 or RS 485 if the transmitters can be switched off This type of serial bus is common in traditional industrial automation 3 2 4 Local Interconnect Network To complement automotive networking with CAN for example a low cost technology called Local Interconnect Network LIN has been developed In addition to protocol definition LIN specification covers a work flow concept with configuration and node capability languages An application programming interface API is also specified LIN can be implemented with the same UARTs that are used in V 24 V 28 serial links only the bus driver receiver circuitry is simpler One common single ended bus signal is used making the cabling simple but also more sensitive to interference LIN has a maximum data signalling rate of 55 20 kb s which limits its applicability T
95. e the other is for backup The single plane lidars communicate over V 24 V 28 serial link the quad plane models have external electronic control units with Ethernet interface The cameras have an IEEE 1394 interface and they are arranged into a trinocular vision system 12 Intelligent Vehicle Management Pn Re A ee 3 System VMS I va Fight SICK i OS 4 H 4 ten i t i Obstacle Det i i i H e o Rett i Vision System i g s Cornor Obstacte Det s S oM Path Detection i i m LIDAR i i i Obstacie Det Analog gt Transmission i Na i Plane s Steering s e ECU a ae Vehicle Manager Servo Steerng Multi iiia i a Piane gt ECU f Path Planer 41 t Scanner i Li i Epean pe pe d Vetwcie Control i r ia aa AS GO EET E inio Store 08 Araico gt Throttie t OmniStar GPS API 4 oa i 5 i i RSZ CAN ES Trimble rs232 gt Oxford i Shed lt cano ECU 8 AgDGPS gt GPSIMU r System Manager w gt i 5 Oxford M a ii Program Monitor A gt GPS IMU i i u i i Se SSE ES CE Secure Ethemet to DC o Converter 3 Aralog gt Brakes Odometer Figure 8 Hardware architecture of control system of TerraMax 12 31 Urmson et al present the development of two automated military vehicles Sandstorm and Highlander In addition to embedded computers the control systems include several embedded modules of one or more microcontro
96. e 2 An automated straddle carrier AutoStrad 28 A high integrity navigation system is implemented with a horizontally scanning radar four wheel encoders one encoder in the steering system of each straddle leg a real time kinematic RTK global navigation satellite system GNSS receiver and an inertial measurement unit IMU AutoStrad also has four horizontally scanning lidars one at each end of each straddle leg for obstacle detection Next to each lidar is a mechanical bumper with a limit switch The system has a receiver for a heart beat radio signal and another radio link for receiving tasks and plans from the base station Although the computing platform sensor interfaces and on board networking are not described in detail it is mentioned that a separately housed computer operates the on board safety system After thorough testing of the first prototype four AutoStrads were built for testing fleet operation The hardware of the control system was redesigned and machine level control functionality was implemented by the manufacturer of the original straddle carrier Nevertheless the system design was not changed from the first prototype of AutoStrad Finally the commercial version of AutoStrad was designed to have a series hybrid drivetrain and on board networking based exclusively on CAN 28 Teller et al have developed an automated forklift that can be operated safely and flexibly alongside humans both outdoors and indoors Although
97. e energized resulting in an emergency stop The states of the emergency stop button and the run wait button are transmitted in the response packet from the button module When the emergency stop button is pressed the energy stored in the shutdown capacitor is sufficient for transmitting two or three response packets Therefore the relay module can trigger the emergency stop before watchdog time out The status of the emergency stop the run wait button and the bypass switch are transmitted over CAN to the main control system The status of the bypass switch is also transmitted to the button module to be shown with the LEDs The radio modem communication is synchronized to packets transmitted by the button module The communication protocol supports a system of up to two relay modules There are two time slots for the relay modules after the button module has completed its transmission Therefore both 107 relay modules have an individual delay before starting their transmission The protocol could be extended to three machines without notable delay However if the number of machines is increased it is likely that several supervisors and several button modules are required leading to fundamental modifications of the emergency stop system 6 11 Electrical power supply Almost all the devices of the electrical system have a range of supply voltage compatible with a 24 V battery system It was also estimated that a 24 V system is more likely to be
98. e presented by Uusisalo 121 pp 42 57 Although mobile PLCs and I O modules are available with a serial port accessing the registers of the serial port from the control application in real time is typically not convenient Therefore a CANopen compatible remote control interface was designed utilizing the generic embedded module Another benefit is that remote control functionality can then be added to other machines by installing similar devices In this case both CAN and serial port transceivers were mounted on the microcontroller board The application specific board consisted of power supply for the microcontroller board another power supply for the short range radio modem and connectors The software reads data from the serial port every 200 us transmits a response packet after a complete control packet is received and transmits the control values via CAN The response to the remote controller can include force feedback data in addition to conventional status information 6 9 Site wide wireless communication A separate general purpose IEEE 802 11 compliant wireless module with Ethernet interface was selected for secure high performance wireless communication A standalone module was preferred since it is independent of the operating system of the embedded computer Moreover replacing the wireless solution in future is straightforward The module is targeted at vehicle applications Therefore neither electrical nor mechanical installation
99. e stabilization 116 It is even possible to extend the coverage of a single plane lidar by continuous rotation 66 or oscillation 13 92 If the lidar has no fixed mounting the ranging data has to be synchronized with the actual orientation of the lidar Integrated multi plane lidars are also available for extended coverage So far the most extreme solution is a 64 plane scanning lidar 72 118 Several of the listed solutions have external moving parts and rather limited operating conditions which makes applying them to mobile machinery applications more difficult Figure 19 Challenges in obstacle detection with fixed single plane lidar Most of the scanning lidars support Ethernet communication over internet protocol suite typically UDP It is therefore important to make sure that other communication does not cause significant delays especially if the lidar data is used in sensor fusion Communication over a V 24 based serial link is also common If the data rate is low the communication delay needs to be taken into account in calculation Furthermore each lidar may require a dedicated serial port If the lidar has 82 an active aiming system the complexity of communication and functional integration is increased with additional sensors actuators and controllers 4 7 Cameras Well implemented camera systems provide information for remote operation and monitoring Furthermore machine vision can be utilized in mobile machinery a
100. eivers CAN 1 Mb s CANopen active star motion control advanced at 1 Mb s f automotive sensors machine vision cameras surveillance cameras laser 1 Gb s scanners IEEE 802 11 Ethernet f 100 m active star devices GNSS receivers typical mass storage PLC general I O motion control advanced sensors GNSS receivers radio V 24 V 28 115200 kb s 15m point to Saral typical typical Sn modems laser scanners yP yP P advanced sensors bus LIN 20 kb s 40m cabin controls general I O active star IEEE 1394 aes Mb s ae m active sar machine vision cameras typical typical daisy chain mass storage mass storage web cameras 480 Mb s 5m i j f USB typical typical active star machine vision cameras yP yP GNSS receivers 3 4 Wireless data transfer Wireless data transfer is required for direct teleoperation but also for communicating with an automatically operating machine There are several wireless technologies that can be applied to mobile machinery Some solutions include network functionality others are intended for simple point to point applications For some wireless technologies there is support for internet protocol suite or other advanced protocols for others transceiver registers may have to be accessed directly 59 Wireless transceivers are optimized for data signalling rate range reliability or communication delay Some have configurable reception sensitivity and transmission power Transceiv
101. eld programmable gate array FPGA configured to operate as a microcontroller With electrical characteristics of the microcontroller signals and types of the board connectors however the situation is not that simple This has to be taken into account when deciding which signals of the microcontroller to make available and which board to board connectors to use Long term production prospects of connectors need to be assessed In addition complex microcontroller I O without strong support prospects has to be avoided In particular this applies to I O with unconventional electrical characteristics and the digital buses difficult to implement in software 5 1 2 Microcontroller board A microcontroller was selected based on the requirements and experience from different microcontroller families and manufacturers in machine control applications A 56F8323 16 bit digital signal controller from Freescale Semiconductor was chosen The core frequency of the microcontroller is 60 MHz Its data arithmetic logic unit includes a multiply accumulator unit for integer arithmetic With pipelining the microcontroller can perform a multiplication or multiply accumulation of two 16 bit integers on every core clock cycle 26 Although with a typical program the efficiency of the pipeline is not ideal in many matrix operations the core architecture of the 56F8323 is efficient This makes the microcontroller suitable for digital filtering for example The microcontrol
102. elds for Arduino single board computers CAN Newsletter Online CAN in Automation January 10 2014 website Available accessed on November 5 2015 _ http www can newsletter org hardware host interfaces df_for a few dollars more can shields for arduino single board controllers 140110 R Ghabcheloo M Hyv nen J Uusisalo O Karhu J Jara amp K Huhtala Autonomous Motion Control of a Wheel Loader Proceedings of the ASME 2009 Dynamic Systems and Control Conference Vol 2 Hollywood CA October 12 14 2009 The American Society of Mechanical Engineers pp 427 434 A Green Path planning for autonomous vehicles in difficult unstructured environments dissertation University of Sydney 2007 197 p Available http db acfr usyd edu au content php 292 html publicationid 706 M Grenier L Havet amp N Navet Pushing the limits of CAN Scheduling frames with offsets provides a major performance boost Proceedings of the 4 European Congress on Embedded Real Time Software ERTS Toulouse France January 29 February 1 2008 The French Society of Automotive Automobile Engineers the French Society of Aeronautic and Aerospace amp the French Society for Electricity Electronics and Information amp Communication Technologies 8p Available http www loria fr nnavet publi erts2008 _offsets pdf Q Ha M Santos D Rye amp H Durrant Whyte Robotic Excavation in Construction Automation IEEE Robotics amp Automation
103. ements The hardware architecture of the control system has proven flexible robust and research friendly Since most of the utilized devices are targeted at demanding operating conditions they have caused very few reliability problems All the devices cover the minimum operating temperature range specified in Chapter 2 The specified minimum degree of protection IP55 however is not met by the Ntrip module It was installed inside the cabin because it had not been tested according to IEC 60529 23 and the degree of protection was estimated to be no more than IP34 The original enclosure could also have been changed The embedded computers and devices based on the generic embedded module were installed in protective enclosures with panel connectors The enclosures and connectors were chosen to meet IP65 at minimum Although the assembled enclosures were not tested according to IEC 60529 the installation guidelines of connector and enclosure manufacturers were followed to maintain the degree of protection Some reliability problems were experienced related to heat management of the linear voltage regulators as mentioned above In addition a sensor fault in wheel odometry caused an excessive sensor supply current to flow through the application specific board of the wheel odometry module Unfortunately the fuse protection of the module had not been rated properly and the excessive current damaged the board In general the arrangement of the contro
104. ements Part 2 Logical Link Control Institute of Electrical and Electronics Engineers IEEE 802 2 New York NY 1998 239 p Available http standards ieee org getieee802 download 802 2 1998 pdf Information technology Telecommunications and information exchange between systems Local and metropolitan area networks Specific requirements Part 3 Carrier sense multiple access with Collision Detection CSMA CD Access Method and Physical Layer Specifications Institute of Electrical and Electronics Engineers IEEE 802 3 New York NY 2008 597 p Available http standards ieee org about get 802 802 3 html Information technology Telecommunications and information exchange between systems Local and metropolitan area networks Specific requirements Part 11 Wireless LAN Medium Access Control MAC and Physical Layer PHY Specifications Amendment 2 Fast Basic Service Set BSS Transition Institute of Electrical and Electronics Engineers IEEE 802 11r New York NY 2008 108 p Information technology Telecommunications and information exchange between systems Twisted pair multipoint interconnections International Organization for Standardization ISO IEC 8482 Geneva Switzerland 1993 18 p Internet Protocol Internet Engineering Task Force RFC 791 1981 Available https www ietf org rfc ric791 txt 140 61 62 63 64 65 66 67 Introducing OneNet press release National Marine Electronics
105. epartment of Intelligent Hydraulics and Automation at Tampere University of Technology and the Department of Automation and Systems Technology at Aalto University in the Finnish Centre of Excellence in Generic Intelligent Machines Research Myrsky describes modular software implementation of automated functionality and communication over the Internet 80 H ltt et al utilize the small wheel loaders in a case study on user interface framework for control of multi robot systems 53 Terho has utilized the stereo camera system in stereoscopic teleoperation as well as calculating 3D geometry of the surroundings of the machine 106 107 Uusisalo has researched the effect of short range remote control and vibrotactile feedback on performance and user experience with the excavator attachment 121 Furthermore the small wheel loaders and the excavator attachment have been used in several technology demonstrations for industrial and academic audiences 7 11 1 Control system modifications The flexibility of the control system was tested in practice as the control system was extended and modified for different research topics As mentioned above the video streams transmitted by the Axis 241Q video server were initially routed through an IEEE 802 11 wireless AP As the LittleBoard 800 embedded computer with an IEEE 802 11 expansion board was installed it was straightforward to connect the Ethernet cable to a spare Ethernet port on the computer instead of
106. eration The vehicles are able to supplement on board sensing by launching an automated helicopter and receiving aerial lidar and camera data A second generation vehicle with sensors and antennas is shown in Figure 7 66 The computing system consists of several Intel Pentium or compatible computers each with a dedicated purpose sensor and wireless interface excluding stereo and teleoperation cameras planning and hardware accelerated stereo camera processing teleoperation camera interface top camera and lidar processing and low level sensor interface with actuator control All the computers are clocked at 1 2 4 GHz and communicate over Ethernet at 1 Gb s 1000BASE T A separate pulse per second PPS signal is connected to all the computers The signal causes an interrupt that is used to synchronize the real time clocks of the computers which enables precise pose tagging and fusion of sensor data 66 Mast Color Ladar Camera GPS Top Vertically Antenna Scanned Ladar Telemetry Left Stereo Antenna Pair Right Stereo Bumper Sensor Pair Teleop Camera of d Tr j p i s can D CEI pey h Bottom Vertically t Scanned Ladar ey i aS 1 m Horizontally t Py Scanned Ladar 4 Figure 7 Sensor and antenna locations on automated off road vehicle 66 28 1 3 6 Automated excavation Various research projects have been targeted at automated excavation and several arrangements have been patented
107. ers have integrated error detection forward error correction or retransmission mechanisms Some devices are targeted at mobile machinery applications others require protective enclosures or modified power supplies Some technologies are available as ICs or prototyping boards only 3 4 1 IEEE 802 11 IEEE 802 11 based wireless networks have high data signalling rates reasonable ranges and are supported by various protocols There are standalone client modules that typically connect to on board Ethernet as well as wireless adapters that are installed to on board computers In general wireless adapters can be configured more freely by software On the other hand standalone wireless modules are independent of the operating systems of on board computers straightforward to configure and to replace 2 4 GHz versions of IEEE 802 11 based transceivers are unfortunately popular in numerous applications making the frequency band unreliable in some working sites Furthermore there can be other devices besides the IEEE 802 11 compatible transmitting in the 2 4 GHz frequency band The range of an IEEE 802 11 based wireless network is affected by several factors If there is a line of sight between the antennas of the machine and the wireless AP ranges over 200 m are possible but network throughput can be heavily decreased already at 100 m 62 The situation gets worse when the line of sight is lost Therefore several 802 11 based APs may be re
108. ers have low pass filters at control signal inputs enabling PWM signals to be used The valve also has a measurement port for maximum load pressure Similar to the valve on the wheel loader a pressure transmitter with current output was installed in this load sensing port 7 4 Control system of wheel loader The layout of the control system of the small wheel loader utilized with the excavator attachment is presented in Figure 29 To meet the requirements of Chapter 2 the control system is distributed over CAN and Ethernet utilizing CANopen and internet protocol suite as proposed in the reference hardware architecture in Figure 20 For reasons of size cost and device availability at the time of building the machine sensors and actuators with analogue interfaces were applied instead of CANopen versions The data signalling rate of CAN is 250 kb s instead of the proposed 1 Mb s The initial tests revealed that the utilized CANopen I O modules were not able to process bursts of several messages at data rates of 500 kb s and above On the other hand the utilization of I O modules instead of separate CANopen sensors and actuators results in less protocol overhead and therefore a lower network load The Ethernet also has a data rate lower than proposed by the reference hardware architecture 100 Mb s was considered sufficient since the machine vision cameras are connected to a dedicated image processing computer via IEEE 1394 118 Automated fun
109. erter was needed A 20 W model was selected having 13 W of extra capacity over the consumption of the embedded module The converter was installed into a protective enclosure with M12 connectors enabling the converter to be used with possible future low power devices requiring a 12 V power supply It was however noted in initial tests that the linear voltage regulators of the remote control module and the emergency stop relay module overheat when supplied by the 24 V battery system To solve the problem these devices which were fortunately located next to the DC DC converter were connected to the extra 12 V output No arrangements were needed considering switch off because there are no sensitive devices in the control system However if the operating system of the embedded computer is changed the 108 need has to be reassessed The same applies if applications that write data on the system drive are run Table 3 Maximum continuous electrical power consumption when machine is idle Device Maximum continuous power W Engine electronics 140 Parking brake control valve 30 Motor displacement reduction valve 30 Hydrostatic drive pump 25 Steering valve 25 Embedded computer 20 Cabin display 12 Working hydraulics controller 12 Digital hydraulic valve drivers 10 Main relays 10 IEEE 802 11 wireless module 8 Main PLC without external load 7 Emergency stop relay module with modem 6
110. es and read valve control patterns via CAN In addition to the main PLC the middle level of the control system has a separate controller for controlling the digital working hydraulics Because complex experimental control algorithms were to be tested ASPACE MicroAutoBox hardware was selected The dSPACE MicroAutoBox is targeted at control system prototyping in automotive applications The research oriented MATLAB Simulink environment can be directly used to develop the control algorithms Moreover it is possible to monitor the controller log data and adjust parameters online To enable automated loading and other sophisticated control functions potentiometers were installed to measure the lift and tilt 102 angles of the working hydraulics These analogue sensors were connected directly to the ADC inputs of the MicroAutoBox Two separate CAN interfaces of the MicroAutoBox are utilized one for communication with the valve drivers another for communication with the main PLC 6 6 Computing automated functions Although it is possible to utilize the MicroAutoBox in automated functionality research to a certain extent a separate embedded computer was considered superior in flexibility and cost effectiveness CAN and Ethernet communications were specified to be mandatory To enable new interfaces to be added a well established mechanically robust bus for embedded expansion boards was seen as valuable MATLAB Simulink with xPC Target was considere
111. es required It also has to be considered that the control system may need to be extended during the life cycle of the machine The benefits of a modular solution and a standardized design and management process are therefore emphasized Modular I O systems are typically based on slave devices that may perform simple signal processing in addition to basic I O functionality Depending on the physical construction of the machine these I O modules are physically distributed across the machine or located centrally ina cabinet If a protective cabinet is used the I O modules can have a lower degree of protection and the number of commercially available modules physical networks and protocols is therefore much higher On the other hand the wire harness becomes complex if most sensors and actuators are not next to the cabinet Since an automated machine may contain devices that are not intended for mobile machinery applications the I O interface on some of these devices differs from conventional sensors and actuators Typically mobile I O modules are optimized for robustness inputs have low impedances low sampling rates and high decision levels Outputs have low impedances and voltage levels close to the supply voltage Push pull outputs are available but a typical on off output has either a low side or a high side driver Analogue inputs typically have measuring ranges for positive current and voltage signals only For example a sensor may have an
112. eters are based on accelerometers there is some disturbance in the angle signals as the machine vibrates or the bucket is hit against the ground Therefore the maximum angular velocity of the signals is limited to 200 s The effect of the rate limiter on the bucket angle is shown in Figure 34 180 Angle 4 120 6 0 T T T T T 0 1 2 3 4 5 6 Time s Figure 34 Effect of rate limiter on bucket angle signal 125 Up to 15 trajectory points can be stored during open loop control When commanded the controller will move the excavator into one of the trajectory points The position controller has an individual proportional controller for each cylinder This typically results in a slightly curved bucket trajectory There is thus no path following controller Therefore the trajectory points have to be selected so that the order of the joint movements is insignificant Total error is calculated from the relative position errors of cylinders that are assumed uncorrelated siew boom stick ANA Cpucker according to 5 2 2 2 2 tot V eslew boom e stick bucket 5 If the total error stays below a set limit a set settling time the controller will switch back to open loop control The parameters were set to 3 total relative error and 500 ms settling time These limits were experimentally found suitable for the excavation application resulting in steady state position error of less than 10 cm 7 10 Tests of aut
113. files on the system drive is not possible once the xPC Target real time kernel has been invoked Since there is no consistent support for remote access and networking in MS DOS compatible systems it was considered most convenient to utilize live USB with GNU Linux for remote accessing of the CompactFlash To enable live USB the boot sequence of the BIOS was set to give the first priority to USB drives before the CompactFlash A panel connector for USB with sufficient protection was installed on the enclosure A mating cable was fitted with a panel feed through on the dashboard for easy access In addition to enabling live USB this arrangement makes it possible to run an alternative xPC Target model from a USB drive For development and testing of xPC Target models the real time kernel may run a loader model enabling the application models to be loaded from a host laptop Since the loader model supports communication over Ethernet utilizing internet protocol suite it is possible to have the host laptop connected on board or over the site wide wireless network 6 7 Pose estimation sensors One of the first applications to be demonstrated with the wheel loader was specified to be automated path following Horizontal position error was specified to be less than 0 5 m most of the time to be able to follow a typical road and perform reasonably in various earthmoving tasks for example Demonstrations were planned to be conducted at various closed lo
114. ften possible to utilize similar alternators With research equipment in particular managing the power consumption of the control system when the engine is not running is more critical Embedded computers typically require intelligent management of the electrical power supply to prevent file system errors due to unexpected switch off With high performance computers thermal management is also challenging Robust expansion boards are relatively expensive Minimizing the number of different types of bus and network interfaces and utilizing the most common ones improves life cycle manageability Equipment for advanced perception typically requires additional protection machine vision cameras require protective temperature controlled enclosures On the other hand applying advanced lidar systems to mobile machinery is restricted due to external moving parts A small generic microcontroller board may be utilized in intelligent sensor and actuator interfaces being an answer to the third research question Several embedded devices for mobile machinery applications were designed utilizing the developed microcontroller board The approach was found to be flexible and efficient The same approach could be suitable for commercial prototyping projects and control system development Using a generic plug in microcontroller board is a life cycle efficient solution because maintenance and software updates can be continued even after the original microcontroller
115. fter modifications eeeeeeeeeeeeeeeeeteeeeeeeeeeees 111 Modified wheel loader with excavator attachment ceeeeeeeeeseeeeeeeees 116 Control system layo Utes cenena a a a needy a a 118 Inclinometer installations on excavator sseseeseerreessserrrrrrrrrsserrrerrrn 120 Cameras on wheel loader and excavator stick DOOM cceeeeeeeeeeees 121 Electrical system with auxiliary battery eecceseeeeeeee eee eeeeenneeeeeeeeeeeeees 122 Excavator controller block diagram cccccceeeeeeeeeeeeeeeeteeeeeteeeeeeeeeeteee 124 Effect of rate limiter on bucket angle signal cceeeeeeeeeeteeeeeeeeeeeeees 124 Figure 35 Stored excavator positions for automated bucket emptying and return 125 Figure 36 Manual excavation cycle ceeeeeescccceeeeeeeeeeeeeeeeeeeeeeeeeeeeenaaaaeeeeeeeeneneas 126 Figure 37 Excavation cycle with automatic emptying c cccceeeeeeeeeeteeteeeeeeeeeeee 127 List of Tables Table 1 Data rates of device types ececceccceeeeeeeeeeeeseeeeeeeeeeeeeeeeecaaaaeeeeeeeetenensaaaaes 41 Table 2 Comparison of on board data transfer solutions sseseeeeeeeseseeeeeeeeees 58 Table 3 Maximum continuous electrical power consumption when machine is idle 108 List of Symbols Obucket Ostick Ctot slew boom stick bucket R Rp Ta Tss angle measured by boom inclinometer angle measured by stick inclinometer ang
116. gulated supply voltages may be required Fortunately the same 5 V power supply is sufficient for the PCAN PC 104 A DC DC converter with a wide input voltage range was installed inside the same enclosure with the computer M12 panel connectors for Ethernet and the two CANs were also installed on the enclosure Another M12 connector was included for accessing BIOS through a V 24 V 28 serial port Moreover the serial port can be used to connect various embedded sensors to be tested on board The computer has a parallel ATA controller for conventional hard drives and SSDs In addition USB mass storage or a CompactFlash memory card may be utilized Any of these can be used as a system drive Since neither the xPC Target real time kernel nor the application requires writing on the system drive an industrial grade CompactFlash memory card was chosen 103 Since the real time kernel for standalone xPC Target models has to be invoked from an MS DOS compatible operating system FreeDOS was installed on the CompactFlash card The standalone xPC Target models can also be stored on this system drive Although it is possible to invoke the real time kernel and specify a standalone model file at FreeDOS command line it is more convenient to have the model started as soon as the operating system has booted without any manual action However changing which model file is run requires modifying a batch file on the system drive This in addition to managing the model
117. hapter the problems are approached by developing a generic microcontroller board with analogue and digital communication With this board CAN and serial port communications can be implemented and sensor related data processing can be performed Furthermore it is possible to use the board for measurements and control with accurate timing To utilize the microcontroller board in a control system another board with simple application specific circuitry and an enclosure with suitable connectors are applied The design criteria features and use of the boards are presented first Then practical experiences of applying the module are discussed Although the main focus is on control systems of experimental machines applicability to commercial machine control systems is also considered Commercially available boards with similar features are targeted at education research and hobbyists Therefore a commercial solution may require several boards 40 Typical evaluation boards of microcontroller manufacturers may have sufficient hardware included but the size of the boards is often too large for on board applications Moreover the demanding operating conditions of mobile machinery are not considered in the design of these boards 88 There are also commercial embedded modules with various protocol stacks based on CAN or Ethernet These modules speed up the development of devices as there is no need to implement the software or circuitry related to the co
118. he maximum length of the bus is 40 m with a topology similar to CAN 73 Using hubs the length and topology could be extended 99 Another limitation is that a LIN always has one master and up to 16 slaves Although slaves can receive each other s frames directly all the frame transfers are initiated by the master according to a schedule table The header includes a sync byte that enables the use of inaccurate oscillators in the LIN slave devices Thanks to master initiated communication a LIN can be configured to be deterministic Because of these mechanisms the total overhead is unfortunately more than four bytes per frame In addition the LIN specification allows rather long inter byte space resulting in long frame slots in the schedule table Let us consider the actual throughput of a LIN system with slaves that are 8 bit sensors transmitting frames that have one data byte The actual throughput R can be calculated according to 1 Re TERy 1 where Tais the length of sensor data T the length of a frame slot and R the data signalling rate A frame header transmitted by the master is always 34 bits long not taking into account possible inter byte space The slave then transmits one byte of data and a checksum byte Bytes are transmitted similarly to UART communication with one start and one stop bit Thus the response from the slave takes 20 nominal bit times The nominal length of a frame with 1 byte of data is therefore 54 bit
119. ibility and robustness are discussed 7 1 Functional objectives The control system has to support operation in a fleet of several machines The machine may be controlled manually either on board or remotely The remote operator may stand next to the machine or be located in another city In addition to real time video load information has to be available for the remote operator To enable automated excavation the excavator attachment has to perform closed loop control of the joint angles Moreover to maintain the flexibility of the original machine the modifications must not make installing and removing the excavator more difficult 116 7 2 Construction of wheel loader The wheel loader and the excavator attachment suit research use well although the machine is compact the mechanical and hydraulic structures have similarities to larger machines Figure 28 The wheel loader is modified from a commercial machine of the Avant Tecno 300 series The machine is skid steered and has a throttle controlled hydrostatic power transmission with four hub motors The maximum output power of the diesel engine is 15 kW There is a variety of attachments available for the machine Figure 28 Modified wheel loader with excavator attachment The original machine has mechanically operated valves which have been replaced by an electronically controlled stackable mobile proportional valve The valve has six spools two for travel and one each for boom
120. ic equipment Part 7 Detail specification for 8 way unshielded free and fixed connectors International Electrotechnical Commission IEC 60603 7 Geneva Switzerland 2008 92 p Connectors for electronic equipment Product requirements Part 2 101 Circular connectors Detail specification for M12 connectors with screw locking International Electrotechnical Commission IEC 61076 2 101 Geneva Switzerland 2012 118 p S Corrigan Controller Area Network Physical Layer Requirements Application Report Texas Instruments Literature number SLLA270 January 2008 15 p Available http www ti com lit an slla270 slla270 pdf Degrees of protection provided by enclosures IP code International Electrotechnical Commission IEC 60529 Geneva Switzerland 2001 91 p S Demmel A Lambert D Gruyer A Rakotonirainy E Monacelli Empirical IEEE 802 11p Performance Evaluation on Test Tracks Proceedings of the IEEE Intelligent Vehicles Symposium IV Alcala de Henares Spain June 3 7 2012 Institute of Electrical and Electronics Engineers pp 837 842 Available http eprints qut edu au 51539 J Derrick Adaptive Control of a Farm Tractor with Varying Yaw Properties Accounting for Actuator Dynamics and Nonlinearities master s thesis Auburn University 2008 97 p Available httos etd auburn edu handle 10415 6 DSP56800E and DSP56800EX Reference Manual Freescale Semiconductor Literature number DSP56800ERM September 201
121. ication of an automated machine it is common that the machine is intended to travel without a human operator on board To implement path following the machine has to perform pose estimation that is estimate its position and orientation in relation to a reference frame Since the reference frame bandwidth reliability and accuracy vary between sensor types data fusion from several devices is typically applied 4 4 1 Global navigation satellite system receivers A GNSS receiver enables the global position of a machine to be estimated practically anywhere in the world without any local infrastructure The antenna of the GNSS receiver however has to have a line of sight to several satellites which limits the number of feasible applications Nevertheless if the signals from a sufficient number of satellites can be received only occasionally a GNSS receiver can still be used together with other pose estimation sensors At the moment there are two operational global systems the Global Positioning System GPS system operated by the U S Air Force and Global Navigation Satellite System GLONASS operated by the Russian Aerospace Defence Forces Probably due to the long history of GNSS applications in well standardized maritime electronics practically all GNSS receivers are able to output NMEA 0183 compliant messages typically over a V 24 V 28 serial interface If this interface is used replacing a GNSS receiver can be straightforward Since the N
122. ico ITXe Specification Rev 1 0 Small Form Factor Special Interest Group August 2009 12 p Available http www sff sig org pico itxe_ spec v10 pdf D Prescott Autonomous heavy equipment positioned to be next disruptive technology SAE Off Highway Engineering June 13 2013 SAE International Available http articles sae org 12084 Product information DWM1000 DecaWave 2013 2p Available http www decawave conm sites default files product pdf dwm1 000 product brief padf K Rajapolvi Sinusoidally commutated direct current motor drive for laser scanner master s thesis Tampere University of Technology 2012 93 p in Finnish Regulation on collective frequencies for license exempt radio transmitters and on their use FICORA 15 AF 2013 2013 Available 144 94 95 96 97 98 99 100 101 102 https www viestintavirasto fi attachments Viestintavirasto15AF2013M_ en pdf Requirements for Internet Hosts Communication Layers Internet Engineering Task Force RFC 1122 1989 Available https www ietf org rfc ric1122 txt Richards P Understanding Microchip s CAN Module Bit Timing Microchip Technology Literature number AN754 2001 13p Available http ww1 microchip com downloads en AppNotes 00754 paf Road vehicles Controller area network CAN Part 1 Data link layer and physical signalling International Organization for Standardization ISO 11898 1 Geneva Switzerlan
123. ified to also supply 24 V devices that do not necessarily require a regulated power supply If there are devices that require a regulated 12 V supply another voltage regulator is needed It can be powered either from a 12 V battery or regulated 24 V supply If the converter is supplied by the battery a more complex 12 V to 12 V converter is required On the other hand if there are two DC DC converters in series the overall efficiency is lower and the total output current required of the 12 V to 24 V converter is higher DC DC converter Vin Vout S a A 24 V devices 8 5 18 V 24V Device 1 Device 2 moderate combined power GND Vin GND Vin GND 22 26 V 18 36 V DC DC converter can Vin Vout Eee ea ee 12 V devices with regulated supply 8 5 18 V 12V Device 3 lowest combined power GND Vin GND 11 13 V 12 V devices with direct battery supply Device 4 highest combined power Vin GND 8 5 18 V Figure 16 Example of power distribution 69 4 1 4 Switch off As described above the power consumption of the electronic control system has to be minimized when the engine is not running Even more important is that the battery is not discharged when the control system is switched off This can be done by controlling a battery isolator relay directly with the ignition lock or a main switch Some devices however do not tole
124. ing System dual inline package digital signal processor Embedded Board eXpandable computer form factor European Geostationary Navigation Overlay Service Enhanced On Chip Emulation Embedded Platform for Industrial Computing computer form factor field programmable gate array floating point unit Global Navigation Satellite System the particular system maintained by Russian Aerospace Defence Forces global navigation satellite system in general general purpose input output Global Positioning System the particular system maintained by U S Air Force hardware description language Inter IC digital interface integrated circuit International Electrotechnical Commission Institute of Electrical and Electronics Engineers inertial measurement unit input output internet protocol ISO JTAG LAN LED MEMS NMEA Ntrip ODVA International Organization for Standardization Joint Action Test Group local area network light emitting diode Local Interconnect Network micro electrical mechanical system National Marine Electronics Association Networked Transport of RTCM via Internet Protocol ODVA Inc formerly Open DeviceNet Vendors Association Inc Open Systems Interconnection Process Data Object proportional integral derivative programmable logic controller Power over Ethernet pulse per second precision time protocol random access memory registered jack 45 pulse width modulation Radio Technical Commis
125. ion are included A generic microcontroller module that can be used to interface new sensors and actuators with the control system is presented in Chapter 5 The design criteria features and construction of the module and application specific use are presented In Chapter 6 a wheel loader with automated path following is presented as an example The control system architecture and individual devices are described Meeting the requirements for control systems of automated mobile machinery is discussed The control system of a small remotely operated skid steered wheel loader with an automated excavator is discussed as another example in Chapter 7 The architecture of the control system hardware is presented The implementation of operator assisting functionality is described and test results are shown Finally conclusions are drawn Guidelines for designing the control systems of automated mobile machinery are proposed 2 Application related requirements for electronic control systems Automated mobile machinery has special requirements for electronic control systems that pose design challenges In this chapter these requirements are presented The requirements are divided into ones that derive from long life cycles and demanding operating conditions of mobile machines ones that are related to automated functions and ones that are specific to multi machine environments 2 1 Mobile machinery Mobile machines have longer life cycles than e
126. ions ssesssneneeeeeseeeeeerrnrrrsserrerrnrersserrrrrrn n 128 7 11 2 Meeting requirements c cccccceeeeeeeeeseeeeeeeeeeeeeseeaeaeeeeeeeeenenenaaeaes 128 8 CONCLUSIONS inrninrenniinonein inna tare ait de tees alate N 131 REFERENCES vinice eea ea aa RA etal ae eaea Sat CEEE ETETEA RA cates rene 133 List of Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Figure 11 Figure 12 Figure 13 Figure 14 Figure 15 Figure 16 Figure 17 Figure 18 Figure 19 Figure 20 Figure 21 Figure 22 Figure 23 Figure 24 Figure 25 Figure 26 Figure 27 Figure 28 Figure 29 Figure 30 Figure 31 Figure 32 Figure 33 Figure 34 Modular computing platform of the AGV adapted from 27 cee 20 An automated straddle carrier AutoStrad 28 eecceeeeeeeeeeeeeeeeeeeeeeeees 21 Proof of concept of an automated forklift 105 0 eeeeeeeetteeeeeeeeeeeeees 22 An automated mining machine with additional sensors 76 000 23 Hardware architecture of tractor implement navigation system 10 25 Hardware architecture of retrofitted control system for off road vehicle 42 26 Sensor and antenna locations on automated off road vehicle 66 27 Hardware architecture of control system of TerraMax 12 ceeeeeee 30 Hardware architecture of Sandstorm adapted from 125 cece 32
127. ire external circuitry between cameras for buffering and biasing Industrial machine vision cameras are typically designed to have a regulated supply voltage and therefore require a DC DC converter in mobile machinery applications Since regulating the lighting conditions in outdoor applications is not typically feasible a camera has to adapt to dark and bright ambient lighting For this purpose auto iris lenses may be applied Unfortunately auto iris control is not common feature in machine vision cameras To improve performance in dark conditions infrared or visible lighting is also used A camera with a high dynamic range image sensor may be utilized to improve detection of objects when there are both dark and bright areas in the field of view If a machine vision camera is used in a mobile machinery application usually due to performance requirements additional protection is mandatory for tolerating the operating conditions An enclosure is often required for protection against dust and water Moreover heating may be 83 required to maintain temperature and humidity within camera specifications and to keep the front window clear The accumulation of dust and dirt on the front window has to be considered when selecting the installation location to maximize the cleaning interval A mounting that attenuates mechanical shocks and vibration may be needed A suspension on the other hand decreases performance as the camera is no longer aligned wi
128. is applied 75 1 3 7 DARPA challenges Several automated off road vehicles with path following and obstacle avoidance capabilities have been developed for the Grand Challenges organized by the Defense Advanced Research Projects Agency Later the focus has been on automated driving with other traffic and pedestrians present in the DARPA Urban Challenge Although most of these vehicles cannot be considered experimental mobile machines there are similarities in the design objectives of the control systems demanding environmental conditions sensor types and on board communication can be close to automated mobile machinery Moreover the research and development work in these projects may be done by dozens of people at different locations and further work may continue over a decade with the same vehicle platform Therefore modular and flexible hardware and software solutions are often desirable in these projects Braid et al developed the control system for an automated off road military truck TerraMax The truck has six wheels all wheel drive and all wheel steering The computers and networking equipment are installed in a suspended rack under the passenger seat A display keyboard and mouse for on board testing and development are mounted on the dashboard of the truck The sensors are fixed to the roll cage with adjustable mounts that tolerate shocks and vibration A cleaning system is installed to enable automatic washing and drying of the sens
129. is simply cycling the three target positions Considering bucket emptying in particular the control system could change to target 3 bucket emptying automatically as soon as target 2 over emptying position is reached In Figure 37 the excavator is idle 1 7 s after reaching target 2 because of waiting for input from the operator Moreover the control system could simply wait a short time at target 3 to let the soil fall off the bucket and then return to target 1 Based on the tests conventional mobile proportional valves and low cost inclinometers can perform closed loop position control for operator assistance The performance and I O features of the generic embedded module were also sufficient The control software can be quite simple but there are several parameters to configure Although the functionality of the developed system is simple compared to the automated excavation systems presented in Chapter 1 also the required hardware is simple and low cost Moreover the developed controller demonstrates the versatility of the generic embedded module Based on the results the position controller can make excavation work easier The presented system could improve the efficiency of novice operators in particular 128 7 11 Discussion In addition to automated excavation several research topics have been covered utilizing the modified small wheel loaders and the excavator attachment The research has been conducted in co operation between the D
130. ke Fan Crank RPM Lights Accessories Shaft RPM Left Encoder Figure 6 Hardware architecture of retrofitted control system for off road vehicle 42 Beacon The hardware architecture of the retrofitted system is presented in Figure 6 The sensors have a grey and actuators a white background in Figure 6 The angular velocities of the engine torque converter output and wheels on both sides are measured with encoders Sensors for measuring position and pressure of each brake actuator are installed as well as limit switches Limit switches are also mounted on the gear selection mechanism A GNSS receiver with an integrated IMU is used for global pose estimation Electrical servo motors and controllers are used for throttle and choke control The electrical actuation of brakes and gear selection are not described There is one computer for navigation and another for low level vehicle control The vehicle control computer has an expansion board for analogue I O The sensors and actuators are connected to the expansion board apart from the electrical servo controllers that communicate with the computer via a V 24 V 28 serial link There is also an emergency stop system that can override the actuator control signals from the vehicle control computer with a separate hardware signal The computers are connected with Ethernet CAN and a V 24 V 28 serial link In addition to the retrofitted system extra sensor actuator and computing modules can be installed
131. l sources of ripple are switching mode converters There are also inductive loads such as mobile hydraulic valves and electric motors that generate interference when they are switched A separate conductor is used for each analogue signal in a control system This results in high cable costs and increases the probability of a cable or connector fault as the number of signals becomes higher Each conductor is also a potential source of interference for the signals of the neighbouring conductors Analogue sensor signals are typically connected to an ADC of an I O module or a mobile PLC Depending on the properties of the analogue signal there are several design considerations amplification anti aliasing filter ADC resolution sampling frequency and digital signal processing Similar parameters need to be decided when analogue actuator signals are produced by digital to analogue converters DAC 3 1 1 Continuous analogue signals Voltage signals are the most difficult type of analogue signals regarding interference Therefore they only have to be carried over short distances in a mobile machine Designing a cost effective generic voltage input or output circuit is difficult due to several commonly used voltage ranges Moreover as mobile machine control systems mainly consist of single supply devices the ranges that include negative voltage values are challenging to process Measuring a resistance includes transferring a voltage signal Therefo
132. l system follows the reference hardware architecture presented in Figure 20 The low level control system however is distributed over three CANopen 112 networks instead of one and the data rates are lower than the proposed 1 Mb s This solution increases flexibility and improves compatibility with the CANopen slave devices that have limited message or data rates The joystick was ordered with a J1939 interface instead of CANopen due to a shorter delivery time Analogue temperature pressure and position sensors auxiliary on off valves and cabin buttons are connected to the I O of the main PLC instead of separate CANopen I O modules This is not optimal considering life cycle manageability since a replacement PLC needs to have similar I O to minimize software modifications Utilizing the three CAN interfaces of the PLC also has a negative effect as the higher number of used CAN interfaces decreases the number of potential replacement PLCs A separate CAN switch would improve the situation The high level control system is distributed over Ethernet at 100 Mb s instead of the proposed 1 Gb s Therefore adding machine vision as estimated in Table 1 requires an upgrade to 1000BASE T However no devices need to be replaced The embedded computer supports 1000BASE T and the rest of the current 1O0OBASE TX network can be connected to one of the ports of a 1O00BASE T switch The CAN Ethernet bridge proposed in Figure 20 is replaced by the quad channel C
133. ld Robotics Vol 23 Iss 9 2006 pp 693 708 Available http www ce unipr it people broggi publications jfr terramax pdf G Broten J Collier Continuous motion outdoor 21 2D grid map generation using an inexpensive nodding 2 D laser rangefinder Proceedings of the IEEE International Conference on Robotics and Automation ICRA Orlando FL May 15 19 2006 Institute of Electrical and Electronics Engineers pp 4240 4245 Bulgin Product Catalogue Elektron Components 2010 212 p Available http www bulgin co uk PDFs Cat83_sections Bulgin cat83_all pdf H N Cannon Extended Earthmoving with an Autonomous Excavator master s thesis Carnegie Mellon University 1999 110p Available http www cs cmu edu hcannon thesis pdf CANopen Application Layer and Communication Profile CAN in Automation CiA DS 301 Erlangen Germany 2002 135 p CANopen ChipF40 System Manual SYS TEC electronic June 2012 90 p Available http www systec electronic com en products system on modules core modules canopen chip f40 J A Caywood D M De Moss E C Fitch R F Osborn amp J O Matous Automatic back hoe control system Pat US 3339763 A App No 587385 October 14 1966 September 5 1967 16 p 20 21 22 23 24 25 26 27 135 Ceramic Dual In Line CDIP Family 600 inch Row Spacing JEDEC Solid State Product Outline JEDEC JEDEC Standard MS 032 A 1999 5 p Connectors for electron
134. le discussion and feedback to the people who have been working in the same office with me during the past decade Miika Ahopelto Joni Backas Ji Wung Choi Reza Ghabcheloo Tomi Krogerus Erkki Lehto Jarno Uusisalo Jani Vilenius and Antti Vuohijoki In addition wish to thank Ville Ahola Janne Honkakorpi Mikko Huova Mika Hyv nen Seppo Joonala Sanna J rvensivu Antti Kolu Juha Kukkohovi Markku Luomaranta Jussi Tervonen and Vesa Ulvila for fruitful teamwork in designing building and utilizing the equipment discussed in this thesis The valuable pre examination feedback from professors Marcus Geimer and Kari Tammi is highly appreciated Part of this research was funded by TUT Graduate School The research was conducted partially in the Centre of Excellence in Generic Intelligent Machines Research funded by the Academy of Finland Part of the research was also conducted in the Energy and Life Cycle Cost Efficient Machines EFFIMA research program managed by the Finnish Metals and Engineering Competence Cluster FIMECC and funded by the Finnish Funding Agency for Technology and Innovation TEKES research institutes and companies Their support is gratefully acknowledged Furthermore wish to express my gratitude for financial support to the Jenny and Antti Wihuri Foundation the Finnish Science Foundation for Economics and Technology as well as the Finnish Foundation for Technology Promotion Although consider prototyping wi
135. le measured by bucket inclinometer bucket joint angle stick boom joint angle total error relative error in slew position relative error in base boom position relative error in stick boom position relative error in bucket position network throughput data signalling rate length of payload data length of frame slot b s b List of Abbreviations 10BASE T 100BASE TX 1000BASE T 4G 6DOF 8P8C AC ADC AFS AGV AP API ARP ATX BIOS CAN CAN FD CiA CIP CRC DAC DARPA DC DC DFCU DGPS DIP DSP EBX EGNOS EOnCE EPIC FPGA FPU GLONASS GNSS GPIO GPS Ethernet at 10 Mb s in twisted pairs of copper wire Ethernet at 100 Mb s in twisted pairs of copper wire Ethernet at 1 Gb s in twisted pairs of copper wire fourth generation of mobile telecommunications technology six degrees of freedom eight position eight contact modular connector alternating current analogue to digital converter articulated frame steering autonomous guided vehicle access point of a wireless network application programming interface address resolution protocol Advanced Technology eXtended computer form factor basic input output system controller area network CAN with flexible data rate CAN in Automation Common Industrial Protocol cyclic redundancy check digital to analogue converter Defense Advanced Research Projects Agency direct current to direct current digital flow control unit differential Global Position
136. lectronic components Therefore a machine is likely to have its electronic control system at least partially updated or upgraded at some point In addition to changing spare parts new functionality is added to old machines To reduce the costs of these changes the control system has to consist of generic modules that are straightforward to replace The spare part stock can be kept smaller if one generic module can be configured to perform different tasks The architecture of the control system also has to be flexible so that the control system can be extended by adding new devices Mobile machines often operate in demanding conditions extreme temperatures dust snow and high pressure water are not uncommon Not only do the machines work on rough terrain but heavy vibration and shocks are also generated by the on board mechanisms and engine Although some sensitive devices may be located inside a cabin in general dust and water proof enclosures robust construction and thermal management are required The electrical devices that are neither cleaned with a pressure washer nor sunk into water still require a minimum degree of protection of IP55 as specified in IEC 60529 23 The devices need to operate over an ambient temperature 40 range of 20 C to 50 C at minimum For devices mounted next to an engine or exposed to direct sunlight this is not sufficient In addition single electronic components inside an enclosure may need to operate at up
137. ler does not have a floating point unit however which has to be taken into account in software development The features of the 56F8323 are presented in Figure 21 The microcontroller has a CAN controller a 6 channel PWM controller two 12 bit ADCs with 4 channels each a quadrature decoder for incremental pulse signals two logic level serial ports and two SPls Any of these apart from the ADC inputs can be disabled and the corresponding pins can then be configured for GPIO The microcontroller also has an input for external interrupts The 56F8323 has a supply voltage of 3 3 V but its logic level inputs tolerate more than 5 V Logic level outputs tolerate external pull up to 5 V 2 91 COP Watchdog Program Memory Power Management Temperature Sensor AKB 32 KB RAM Flash Relaxation Oscillator 2 SPI PLL 8 KB Boot Flash 2 SCI Up to 27 GPIO JTAG EOnCE 56800E Core 8 16 bit Timer 60 MIPS 60 MHz ae 64 LOFP age Quadrature Decoder 9 12 bit ADC Data Memory 6 ch PWM FlexCAN 8 KB 8KB RAM Flash Figure 21 Features of a 56F8323 microcontroller 3 For flexibility and easy prototyping the board was planned to fit a normal dual inline package DIP socket The 40 pin variant would have been optimal regarding the number of pins The available board space however was insufficient Moreover an option for a more secure fastening was considered necessary Therefore the row spacing of the pins was designed to be 25 4 mm instead of the 15
138. level protocols are based on transmission control protocol TCP 109 which corresponds to a transport layer protocol in the OSI model As a connection oriented protocol it has features that are not needed in control applications A more suitable option is another transport layer protocol UDP A lost or duplicated packet is not detected by UDP 119 In a small properly configured on board network transmission errors are unlikely and typically originate from a hardware fault Therefore a separate detection of fault situations is usually implemented 3 2 2 2 Industrial Ethernet Neither Ethernet specifications nor internet protocol suite definitions are deterministic although frame collisions can be avoided by using switches instead of hubs the communication delay cannot be predicted if the transmissions of several devices overlap There are several competing solutions that implement a deterministic industrial Ethernet Some of these however require modified Ethernet hardware Some specifications are entirely based on proprietary network controllers others work with IEEE 802 3 compliant controllers but achieve improved accuracy if modified controllers are used Fortunately the modified controllers required for accuracy enhancement are often IEEE 1588 compliant and used to implement hardware assisted precision time protocol PTP that enables clock synchronization in sub microsecond range It is also possible to implement PTP with conventional IEE
139. ling is required if the installation location of the computer does not enable sufficient thermal conduction or the ambient temperature is too high This is even more likely with high performance embedded computers It may therefore be feasible to distribute the computing over several lower performance computers that can be cooled by thermal conduction If a fan is used air filtering is often required to achieve a sufficient degree of protection for the enclosure unfortunately increasing the need of maintenance 75 4 3 2 Mass storage Although some embedded computers include soldered flash memory external mass storage is often needed In machinery applications flash based solid state drives SSD are a feasible option tolerating mechanical shocks and vibration In addition to conventional buses for internal mass storage an embedded computer typically has a socket for a flash memory card Furthermore practically all embedded computers support USB mass storage In many cases it is possible to boot the computer from a memory card or a USB flash drive removing the need for an actual SSD entirely Commercial grade memory cards and USB flash drives are not designed to tolerate the operating conditions of mobile machinery In addition the reliability and endurance of commercial grade flash ICs may be insufficient Even industrial grade memory cards and USB flash drives perform as a system drive slower than devices that are actually designed to be sys
140. lled joint An angular potentiometer is used to measure the freely moving joint between the tractor and the seed drill The signals of these sensors are transmitted to the ISO 11783 network A measurement system is installed on the roof of the tractor for pose estimation It consists of an RTK GNSS receiver with Virtual Reference Station VRS service an IMU optionally a separate fibre optic gyroscope and a microcontroller board that merges the data and transmits it over the ISO 11783 network using NMEA 2000 compliant messages as specified by National Marine Electronics Association The GNSS receiver and the sensors have V 24 V 28 based serial communication with the microcontroller In addition the wheel encoders and the ground speed radar of the tractor are used for pose estimation 10 Cruise control control Hydraulic valve anne RS 232 WLAN Tractor bus NAVIX GUIDEX TECU ISO 11783 Figure 5 Hardware architecture of tractor implement navigation system 10 A vertically downwards scanning lidar is installed on the seed drill to detect the adjacent swathe left in the field by the previous drive A similar lidar installed horizontally scanning is mounted in front of the tractor for obstacle detection The lidars are equipped with IEEE 802 11 based wireless interface The computing of the guidance system is performed by an Intel Core 2 Duo based desktop computer with a CAN USB adapter and an IEEE 802 11 wireless interface Although
141. llers that run a real time operating system each The modules are connected with automotive grade data links Hardware related functions are developed in C and assembler but MATLAB Simulink with automated code generation is used to implement control routines The original alternators of the vehicles are removed Because the maximum power consumption of the electrical system also exceeds the ratings of the replacement generators both vehicles have microcontroller modules controlling the generators and the voltage converters based on loading conditions There is a separate radio link for remote emergency stop 116 Sandstorm is customised exclusively for automated operation the roof and passenger compartment are removed Sensors and computers are installed on a suspended platform for protection The movement of the suspended platform in relation to the vehicle frame is not measured which affects path following performance for example A separate small diesel engine and a 24 V generator are installed to supply electrical power instead of the original alternator of the vehicle Heat management of the electronics is realized by installing an extra evaporator inside the electronics cabinet The compressor of the cooling system is driven by the main engine A large gearwheel is mounted behind the steering wheel for electrically actuated steering The gearwheel is paired with an electric motor The actual steering angle is measured by a sensor at the output of
142. lmost fully charged when starting the engine to prevent the computers and I O modules from resetting In addition to occasional file system errors the rebooting caused another problem since the rotation speed of the diesel engine is controlled by one of the computers a reboot during engine start often resulted in the engine not starting at all Therefore a small auxiliary battery was connected through a Schottky diode as presented in Figure 32 o gt main _ auxiliary_ ii PODE converter battery J battery J Vin Vout M AAJ 10 16 V 48 V o Starter Alternator DM586 MIO24 MIO24 Figure 32 Electrical system with auxiliary battery 123 The IEEE 802 11 AP utilized initially for video transfer is a Power over Ethernet PoE device Because a suitable PoE power injector for vehicle use was not available an automotive DC DC converter with a 48 V output was utilized The converter was installed inside the side compartment due to insufficient degree of protection The entire control system was planned to be operated for testing development or calibration without the engine running Because fitting a large battery in the small wheel loader was not feasible a connector was installed for external power supply 7 9 Automated excavation functions As the first step in developing automated excavator control a simple closed
143. lse frequency signals are quadrature signals A quadrature interface has two square wave signals that have 90 or 90 phase difference These signals are typically used for calculating angular or linear movement Each edge of either signal corresponds to a small change in rotation or displacement and the sign of phase difference indicates the direction of the change Quadrature outputs are typically push pull type Therefore there is no need for external resistors On the other hand quadrature devices often operate at a fixed signal voltage level which is not directly connectable to a typical mobile I O device A similar interface can also be implemented with sinusoidal signals 3 2 Digital buses and networks Digital communication has undisputable advantages compared to analogue signals digital signals have a strong tolerance of interference and noise it is possible to transfer several control signals and configuration data in one conductor and transmission errors can be detected and corrected for example When arranged as a network digital communication enables efficient distributed control and minimizes cabling A device with a digital interface has an embedded microprocessor typically as the core of a microcontroller unless both functionality and communication interface are simple This makes the devices more expensive On the other hand as the computation of a system can be distributed the main controller can be less expensive The ke
144. ly operated machines without positioning equipment or unmapped objects moved by manual machines In this case the automated machines need to have sensors to detect these obstacles In this thesis the minimum requirement is that two automated machines may be operated in a closed environment simultaneously There is no need to detect other machines or obstacles by on board sensors However the hardware architecture of the control system must enable perception sensors to be installed later 3 Feasibility of typical data transfer solutions There are several ways to transfer measurement and control signals in hydraulic mobile machines Keeping the control system architecture modular robust and generic can prove difficult even with manually operated machines The problem becomes more complex when the functions of a machine are automated and it is operating in a multi machine environment This requires sensor and computation devices that have not been used in mobile machines before Furthermore as these devices are not targeted at mobile machine applications they have limited compatibility with typical control system I O buses and networks In this chapter the challenges related to these means of data transfer are discussed 3 1 Non digital interfaces Most sensors first convert the measured quantity into an analogue electric signal typically voltage More advanced operations such as signal processing amplification conversion and digital inte
145. me PLC can also perform other functions in the control system This can decrease overall hardware costs but what is more important using a generic PLC can also improve life cycle manageability It is however critical that the PLC has minimal power consumption when the deep discharge protection becomes active Devices 1 and 2 are signalled before the battery is disconnected and perform a coordinated shutdown or a transition into a low power mode There are also devices that do not have a low power mode and tolerate a sudden loss of power Device 3 is an example of such a device and 65 therefore requires no prior indication from the protector The lower diagram shows a system with devices that have internal protection circuitry against deep discharge Since each protection circuit operates independently it has to be confirmed that the devices can be shut down in any order without causing undesired or even dangerous operation Deep 12V n discharge protector alarm Device 1 Device 2 Device 3 Device 1 Device 2 Device 3 e Sa Deep Deep Deep discharge discharge discharge protection protection protection Figure 14 Two arrangements for deep discharge protection If all the devices of the control system accept a wide supply voltage range and have internal deep disch
146. me grabber expansion board may be more expensive than a standalone video server It is also possible that running the video server application uses much of the computing performance Moreover the separate solution has better life cycle manageability due to the limited driver support of embedded computer expansion boards Real time video often consumes most of the available wireless data transfer capacity especially if several on board cameras are used simultaneously to cover the monitored area Therefore the specifications of video frame rate resolution and encoding method need to be considered together with specifications for wireless communication Alignment and synchronization of cameras is not as critical as with machine vision However if the image data of several cameras is fused into one video these aspects need to be taken into account A special case is stereoscopic video where camera alignment and baseline are critical in producing a tolerable view for the remote operator Although some of the alignment errors can be compensated by image processing it results in increased delay and decreased image quality 84 4 8 Emergency stop Since an automated machine may be operated without an operator on board there has to be a reliable wireless system for signalling emergency to the on board control system to prevent accidents The system has to be independent of the rest of the control system and rather simple considering verification and ri
147. milar arrangements are needed when prismatic joints are measured Cable actuated rotary sensors as well as sensors with a linear push rod are applied Some sensor technologies are however not suitable for mobile machinery applications the vibration of a machine heavily limits the life a conventional potentiometer for example if it causes the sliding contact to oscillate With incremental sensors on the other hand the problem is that moving a mechanism for initializing the sensor is not always possible The sensors may be installed distant from PLCs and computers on complex boom structures for example Therefore the benefits of network communication in tolerance of interference and simple cabling are clear If there are several sensors close to each other analogue signalling and a networked I O module may be applied In many cases however it is feasible to choose a sensor with a suitable network interface Regardless of the type of the sensor mechanical protection has to be taken into account considering both installation location and possible additional protective structures Nevertheless the sensor also has to be accessible for service with reasonable effort 4 6 Laser scanning Scanning lidars are common in robotics providing accurate ranging to various surface materials Typical applications include obstacle detection pose estimation and simultaneous localization and 81 mapping Some lidar models are targeted at outdoor and even
148. mmunication interface Unfortunately the modules may have limited software configurability and support only simple I O interfaces to sensors and actuators Therefore in addition to the embedded communication module a separate microcontroller is often needed to process application related data or interface an embedded sensor 17 81 5 1 Board design Design criteria for the microcontroller board were specified Tolerating the operating conditions of mobile machinery was considered essential Therefore the operating temperature range of the board has to be at least from 20 C to 85 C In addition the board must have a robust mechanical structure that withstands shocks and vibration present in mobile machinery In mobile machinery applications the board has to be protected against dust and water by aluminium or plastic enclosures with a degree of protection of at least IP55 as defined in Chapter 2 The low level control system of the reference hardware architecture presented in Figure 20 is distributed over CAN which is a typical solution in automated mobile machines Therefore a CAN interface is mandatory An asynchronous V 24 V 28 serial port is required for radio modem communication for example Ethernet connectivity would extend the applicability of the board but also make the board larger and more complex An Ethernet interface is therefore considered optional Furthermore sensor converter and driver ICs have synchronous serial interfa
149. mpere University of Technology pp 365 375 Available http URN fi URN ISBN 978 952 15 3273 3 7 M Ahopelto J Backas amp K Huhtala Power management in a mobile work machine reduced diesel rom for better energy efficiency Proceedings of the 7 FPNI PhD Symposium on Fluid Power Reggio Emilia Italy June 27 30 2012 Fluid Power Net International pp 133 148 8 ATX Specification Intel 2004 26 p Available http www formfactors org developer specs atx2_2 pdf 9 J Backas M Ahopelto M Huova A Vuohijoki O Karhu R Ghabcheloo amp K Huhtala IHA Machine A Future Mobile Machine Proceedings of the 12 Scandinavian International Conference on Fluid Power SICFP Vol 1 134 Tampere Finland May 18 20 2011 Tampere University of Technology pp 161 176 Available http urn fi URN ISBN 978 952 15 3273 3 J Backman Navigation System for Modular Agricultural Machines using Optimal Control Methods and Industrial Standard Network dissertation Aalto University Publication Aalto DD 169 2013 2013 107 p Available http urn fi URN ISBN 978 952 60 539 1 2 L Benatazzo M Bertocco C Narduzzi amp R Tittoto Analysis and Measurement of TCP IP Performance over GPRS Networks in M Conti S Giordano E Gregori amp S amp Olariu eds Personal Wireless Communications Springer Berlin Germany 2003 pp 261 275 J Braid A Broggi amp G Schmiedel The TerraMax Autonomous Vehicle Journal of Fie
150. n and several computers These devices typically communicate over Ethernet and interface with low level controllers via CAN and V 24 V 28 serial communication The reasons for choosing the data transfer solutions and hardware architectures are typically not discussed in detail The life cycle manageability of the presented control systems of automated mobile machinery is not discussed in literature The presented research on life cycle manageability on the other hand is focused on control systems with conventional I O and does not cover the sensors and computers required in automated mobile machinery 1 4 Research questions The aim of this thesis is to find out how the electronic hardware of the control systems of future automated mobile machinery has to be designed This objective is formulated into the following research questions What are the limitations of applying different communication technologies There are different communication technologies that may be applied to a control system What are the limits in network throughput and segment length What are the differences in deterministic communication delay cost efficiency and electrical and mechanical robustness Which technologies are feasible in respect of life cycle manageability What are the essential device related design aspects concerning sensing actuation computing and electrical power supply in contrast to designing manually operated machinery Utilizing state of the
151. nables connection to various simple embedded devices and PLCs Moreover radio modems are available with various carrier frequencies to avoid interference with other wireless traffic Unfortunately there are very limited license exempt frequencies available and many of them have tight limits for transmission power and duty cycle 93 Therefore it is possible that a license is required to meet application or location specific requirements Although different models of radio modems typically have compatible serial interfaces the wireless communication is often proprietary Therefore both radio modems of a point to point link may need to be similar Although the radio modems can be interfaced with simple devices some configuration work is required Typically the transmitter power has to be selected as well as receiver sensitivity A cyclic redundancy check CRC algorithm may be implemented to reject received invalid data Other optional features include addressing forward error correction and networking functionality 3 4 3 Embedded wireless transceivers If short range wireless communication is needed at minimal size or cost an embedded transceiver module or IC may be used With these devices some circuit board design and a protective enclosure are required Although there are modules and ICs that implement IEEE 802 11 Bluetooth ZigBee and other standardized wireless communication also proprietary transceivers exist In addition to size and c
152. national Conference on Fluid Power SICFP Vol 3 Tampere Finland May 21 23 2007 Tampere University of Technology pp 343 353 Available http urn fi URN ISBN 978 952 15 3272 6 Mini ITX Addendum Version 2 0 To the microATX Motherboard Specification Version 1 2 Intel October 2010 16p Available http www formfactors org developer specs Mini_ ITX Spec V2_0 pdf MLX80104 5 LIN Slave for Switches LIN IO Extension Short Datasheet Melexis Literature number MLX801045 June 2012 15p Available http www melexis com Assets MLX801045 Lin SwitchlO Extender Short Datasheet 5933 aspx M Myrsky Application of MaCl for controlling work machines Proceedings of GlMnet 2010 Espoo Finland June 16 2010 Aalto University pp 68 71 netIC Fieldbus amp Real Time Ethernet as DIL 32 IC data sheet Hilscher Gesellschaft f r Systemautomation December 2012 2p Available http www hilscher com fileadmin cms _upload en US Resources pdf netIC Datasheet DS 2012 10 EN pdf Network and Customer Installation Interface Connector Wiring Configuration Catalog Alliance for Telecommunications Industry Solutions T1 TR 05 1999 USA 77 p Network Infrastructure for Ethernet IP Introduction and Considerations ODVA Literature number PUBOOO35RO 2007 118p Available http www odva org Portals 0 Library Publications Numbered PUB00035R0 Infrastructure Guide paf OPENUPS 6 30 V Intelligent Uninterruptible Power Supply Installation
153. nctions ss ssseeeseseenerrerersserertrrnrttssrrrrnrrrnnnesernnne 73 4 3 1 Power supply and thermal design sssssssnneneessssennnrrnrrrsserrrrrnnnrsserrrnee 74 4 3 2 Mass SIOlAG Cr cit cetles tet ened ert Pela ie tlninttnatss et ea tee ae terete 75 43 3 R m te ACCESS ranne aeaa Sones ut ae EE e E a aa i 75 Aid POSSOSTIMATION seere EE EE E EEE EESE EES ESEE raS Eea 76 4 4 1 Global navigation satellite system receivers ssssseeneesssseeserrreerseerree 76 AAA Odometer a E E E ER EE 78 4 4 3 Inertial measurements sesssesneeeseeeeereerrerrrrrrrrrrrrrrrrrrrrrrrrrrerrrrrrrrrrtttt 79 4 5 Measuring configuration States scsz kcaesis isteneset cocnccede obese dedidatele Meeesietteanlebinass 79 46 LASEM SCANMING seie epa a a Eaa A EEE E EEE Ea E EA EA E ERRE E 80 47 CameraSrsesseoesa itear aet ea raaa Er aeti Eo aaee pi Ea aAa 82 47A Machine Vielo ctbacienetiatataetietidentietadaetbaskieeuemtaeedacses 82 4 7 2 Remote operation sseseeeeseseenerrrertsstrrntrrnttrssrttntrrnnnrssrrtnnrrnnnneseeennee 83 4 8 Emergency Stopis ieira eea E a A E aE N EA a 84 49 Reference hardware architecture 0c cccecccecceeeceeeceeeceeeceeecececeeeceeeneeeneeenees 85 GENERIC EMBEDDED MODULE c 82s gat ientea lode oiled sake weak aueatiin 87 BA BOard deSIQN serre e E Ea E ER ae 88 5 1 1 Life cycle manageability ssnnnneeeeeeeeennrrnntnsserrrrrrrntrrsrerrnnrrnnnrsserrnern n 89 5 1 2 Microcontroller oar ane
154. ndows NT operating system is 29 installed on the machine for higher level control Furthermore the computer can be used to host a transputer network for parallel processing The industrial computer communicates with the digital control modules over CAN Two short range lidars are used to scan the terrain on both sides of the bucket The operator s cab has been removed The electrical system of the excavator is used to power the electronic control system 44 68 A digging controller with robust sliding mode control and a task planner with hierarchical behavioural approach are developed Experiments with loading and trenching are performed with the excavator The results are close to the performance of human operators especially when the soil is not very hard 44 Maeda et al have used the same excavator to experiment with iterative trenching without utilizing a model of the soil tool interface or actuator force measurements Cartesian impedance control is applied The reference trajectories are generated based on a penetrate drag strategy Feedforward actions are pre calculated using the free motion inverse dynamics of the boom stick and bucket A variable structure observer is implemented for disturbance compensation The results are presented with and without disturbance compensation It is concluded that the proposed iterative control will converge towards the reference trajectory in more demanding conditions if disturbance compensation
155. nensruneonenreirunanenn inore nn nnan 90 5 1 3 Application specific board veccc c sccececedeccesseseccestsdeceetseseuseacsdeceessaeennestedateed 93 5 27 MIDISCUSS IM eeke e E E e Ee a a EE nie ra Eae rE 94 CASE 1 AUTOMATED WHEEL LOADER ss twtr dailies Wee ieeeiteed cients 97 6 1 Mechanical ConsttuclOn lt iW 45 Senws de eacadsdu cease cae eaaacceine 97 6 2 Control system arcnieClune sstecct etc celica anesetecentieeet can depes caters neat ated aati eeataad 98 63 Maim PG yeno ee EE EAA RE E EE ARRE 99 6 4 Power train and steering sssssseeeseeesseeetrrnrtrsstrrrrrrnnrtsstrrnnnrnnnneserrnnren nne 100 6 5 Digital hydraulic boom and bucket control ssssesssssessresererrrsererrrsrrrrrsernn 101 6 6 Computing automated functions sssssseeeeeeesseeerrrrrrrrsserrnrrrnrreserrrnrnnn 102 6 7 Pose estimation SENSORS sce cece ceeds crc catieet ane bent eee eatr renee uate eran etait 103 6 7 1 GNSS eCOIVe lies ccciccsiens sete ccencsalccns tetecees sd ERE EDERE EEA decent REE R REE 103 6 7 2 WWMGGLCOOME Ly 226 iso eo Ss aa eee 104 6 8 Short range remote CONMO 2 ccceace ne Se ed a ea Rae 105 6 9 Site wide wireless COMMUNICATION ccc ee eeeeeetee eee e eee eeeteeteeeeeeeeeeteee 105 6 10 Emergency SIO arere tamer cet eh eatin cculucare enema t en ttae cette sane lebat en caene 106 6 11 Electrical power SUPP viet Song acledadhse Mage Newncaesiw Senne cie pated eae N conan stetye 107 6 12 POISSON a ge OM eM ee ee sae ae ses
156. ng only two cables one for CAN and electrical power the other for the camera on the stick boom The data transfer requirements of Chapter2 are met However the arrangement of the stereoscopic system as explained above does not follow the reference hardware architecture proposed in Figure 20 Utilizing Ethernet cameras instead there would be no need to maintain an embedded computer with a dual IEEE 1394 interface The presented system with IEEE 1394 however makes 100BASE TX Ethernet sufficient for the rest of the high level control system Similar improvement in life cycle manageability would be achieved if the CAN expansion board of the other embedded computer were replaced with a separate CAN Ethernet bridge and the IEEE 802 11 connectivity were realized with an external module as proposed in Figure 20 Some devices of the control system do not meet the operating conditions required in Chapter 2 Although the machine vision cameras are installed inside an IP55 enclosure they do not have a sufficient range of operating temperature The same applies to the AXIS 241Q video server and the DC DC converter supplying the IEEE 802 11 AP Nevertheless the applied enclosures and mounting locations seem to have protected the equipment during the research applications For long term research in demanding conditions additional sealing heating and possibly mechanical suspension of some of the enclosures has to be applied Some reliability problems have been
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158. nside the AFS joint to enable closed loop steering control The resolver has a CANopen interface 6 5 Digital hydraulic boom and bucket control One of the topics to be researched with the wheel loader is applying digital hydraulics to mobile machinery There are four digital flow control units DFCU controlling the lift cylinder and another four controlling the tilt cylinder Each DFCU consists of five parallel on off valves with different orifice sizes Therefore each DFCU has 31 nonzero states resulting in practically proportional volume flow control For electronic pressure compensation advanced operating modes and test measurements pressure sensors were included in all actuator ports Supply pressure was also measured 52 To minimize unwanted pressure transients during state transitions the closing and opening times of the on off valves have to be accurately synchronized This can be achieved with special valve driver circuitry 77 Since the working hydraulics circuit requires 20 special on off outputs no commercial valve driver was available A 20 channel valve driver was designed and connected to CAN with the generic embedded module 20 logic level outputs from the microcontroller board were used to control the on off output circuits Pressure sensor signals were also measured by the microcontroller board To have enough logic level outputs the serial transceiver was left out The microcontroller was programmed to transmit pressure valu
159. nsmitted when new data is available This applies to both control signals and video stream Depending on the level of autonomy an automated machine may require a new subtask from the operator or external control system every second or a new mission every week In any case more delays in communication can be tolerated than when the machine is remotely operated Lost data has to be retransmitted as transmission is usually not a continuous stream However if the automated machine transmits video or other sensor data for real time supervision the requirements regarding retransmission delay and data rate are similar to direct teleoperation In this thesis the control system must enable direct teleoperation over a wireless connection meeting the minimum specification above In addition task data is transmitted The wireless 43 technology has to have sufficient data rate for video transfer at the minimum quality described above Wireless APs may be installed in the working area if required by the chosen wireless technology 2 3 Multi machine environment It is most straightforward to implement automated machines that operate alone in a closed environment There are however applications that require other machines automated or manual to be operated in the same area The presence of other machines sets new requirements and restrictions for the control system of an automated machine On site wireless communication may be intensive even without
160. oard in a control system requires another board which has at least a power supply and wire terminals Depending on the application the motherboards can include different components In this thesis these motherboards are referred to as application specific boards A key benefit of having a separate microcontroller board is that the application specific board can be simple In most cases the electric power supply is the battery and alternator of the machine Therefore the application specific board typically includes a regulated power supply that tolerates battery voltage at input and outputs 5 V to the microcontroller board at least The application specific board may also have components that require a regulated 5 V power supply If the power consumption of these components is less than 200 mW and the machine has a 12 V battery the power supply can be a conventional linear voltage regulator Otherwise a switched mode voltage regulator has to be used or special care taken to ensure proper heat dissipation Minimum configuration also includes a socket for the microcontroller board and wire terminals for the power supply and desired signals The application specific board is shaped and drilled so that it can be fixed into an enclosure A typical arrangement with an enclosure and a panel connector is shown in Figure 24 If the number of components is small and none of them are surface mount devices the application specific board can be made using strip
161. odularity flexibility and robustness are discussed The machine is used in research and demonstration of automated path following short range remote control and digital working hydraulics 9 The control system also needs to support operation as a member of a fleet of automated machines In addition different optimizations of the power train control are to be researched with the wheel loader Moreover the control system has to support modifications of the hydraulic system Overall the control system has to be flexible in terms of updating control algorithms and adding or replacing devices 6 1 Mechanical construction Although the frame of the machine is from a commercial loader the engine and the hydraulic system have been replaced The machine has a mass of 3500 kg a 100 kW common rail diesel engine and AFS with two hydraulic cylinders Since pure drive by wire is needed the steering cylinders are controlled by an electrically actuated proportional valve The front attachment can be changed Most of the tests and demonstrations have been conducted with a pallet fork installed as shown in Figure 25 The machine has a closed loop hydrostatic transmission with a variable displacement pump and four parallel fixed displacement hub motors The working hydraulics circuit has been implemented with digital hydraulics There are 20 seat type on off valves for both lift and tilt 5 in parallel for each control edge 9 98 Figure 25 Automate
162. omated excavation The performance of the excavator control module was tested in a ditch digging scenario where the control system helps the operator empty the soil from the bucket in a pile 7 10 1 Test setup The control system of the wheel loader was configured to send a store position command when a display button on the DM586 is pressed A button on the joystick was configured to trigger a move to target command to be transmitted The index of the stored position was set to cycle from 1 to 3 for both commands which enabled bucket emptying and return functionality 1 over digging point ready to fill bucket 2 soil in bucket boom over emptying position 3 stick boom and bucket extended at emptying position These stored positions are illustrated in Figure 35 D Figure 35 Stored excavator positions for automated bucket emptying and return gt 126 A fourth trajectory point could be introduced if the soil is dug so deep that the base boom has to be lifted before slewing over the emptying position Nevertheless the three trajectory points are sufficient to prove that the concept works Because the hydraulic system of the wheel loader has a fixed displacement pump the control system of the wheel loader was also programmed to control the diesel engine according to the volume flow request from the excavator The gain parameters of the proportional controllers were tuned experimentally Because the modified excavator
163. ometimes it is possible to mount a rotary sensor directly on top of the joint A machine however may have rather large gaps at joints allowing radial movement This is not tolerated by a typical rotary sensor and protective arrangements are needed Moreover installation on top of a joint exposes the sensor to shocks scraping and other mechanical stress When designing the mechanical structure of an automated joint a rotary sensor can be fitted inside the joint pin In retrofit systems this is typically not possible It may be appropriate to locate the sensor away from the joint instead The rotary movement of the joint can be transmitted by a belt for example The orientation of a link can also be measured with inertial MEMS sensors The key benefits of this approach include high mechanical endurance and the possibility to choose mounting location rather freely On the other hand sensor fusion of accelerometers and gyroscopes and kinematic modelling of the mechanism are required to meet the performance of traditional solutions 51 Another option for determining the angle of a joint is to measure the distance between two points on the adjacent links These points are often chosen near the brackets of the actuating hydraulic cylinder providing protection to the sensor arrangement and simplifying calculation A linear displacement sensor may even be integrated into the hydraulic cylinder although in retrofit systems external sensors are common Si
164. ompatible distribution of GNU Linux A radio modem for short range remote control was connected to the serial port of the DM586 The DM586 was programmed to choose the target values for velocity steering and working hydraulics between three possible sources the on board operator the short range remote operator or via CANopen from another embedded computer In addition the DM586 can route target values to the excavator control module A Pentium M based LittleBoard 800 embedded computer was included for implementing automated functionality and routing data for multi machine operation and direct long range teleoperation The computer was equipped with two expansion boards on the PC 104 Plus bus one for CAN the other for IEEE 802 11 wireless networking The computer was configured to run GNU Linux from a CompactFlash memory card Another LittleBoard 800 with GNU Linux was utilized for processing stereoscopic images A PCI 104 expansion board for IEEE 1394 was installed for communication with the two machine vision cameras In addition robust video cameras with analogue output were utilized for remote monitoring A video server was included for transmitting the analogue video content over the IEEE 802 11 wireless connection No separate Ethernet switch was required for connecting the video equipment since the LittleBoard 800 has two integrated Ethernet adapters The bottom right corner of Figure 29 shows also the CAN devices installed on the excavat
165. on off or pulse output that is implemented with a 5 V push pull circuit Because of the high decision levels 5 V may be interpreted as the logical low state Ina similar way a device may have an on off input with a pull down resistor and a specified maximum voltage of 6 V Because of the output voltage level of around 14 or 28 V a typical I O module 73 cannot control a device like this directly Even if the I O module has a low side driver without an internal pull up resistor to the high supply voltage an external pull up to 5 V for example has to be implemented The use of generic I O modules in the control system of an automated machine may therefore require several signal converters amplifiers or simple external circuits with resistors transistors and zener diodes Especially with the physically distributed approach these converters and circuitry require several extra enclosures I O modules typically have a microcontroller for implementing a network interface The same microcontroller may perform digital filtering for inputs for example If the microcontroller has a low computing capacity it may not be able to process all the communication under high network loads Each I O module type considered for a control system therefore has to be tested with high data rates and network loads before deciding whether it is suitable 4 2 2 Mobile PLCs Although an automated machine may require embedded computers for calculating the algorithms of a
166. or attachment If the excavator is removed from the wheel loader a bus terminating cap has to be mated with the CAN connector to maintain proper termination 7 5 Excavator control module An excavator control module was designed and built utilizing the generic embedded module The application specific board was designed to have input circuitry for the load sensing pressure transmitter and a linear potentiometer for slew cylinder measurement Transistors were included for shifting the voltage level of PWM outputs for valve control 120 A linear voltage regulator was considered sufficient since the wheel loader has a 12 V battery system and the current consumption of the excavator control module is less than 100 mA Wire terminals were included for all the sensors valves power supply and CAN The excavator control module was mounted on top of the proportional valve minimizing the length of valve control cables 7 6 Joint angle measurement The excavator control module was first programmed to perform simple closed loop control of the slew cylinder For this a sealed long life linear potentiometer was mounted parallel to the slew cylinder 64 Because the results were encouraging more sensors were added 65 In addition to the slew cylinder sensor there are three inclinometers measuring the absolute positions of the main boom stick boom and bucket The arrangement is shown in Figure 30 where the boom stick and bucket inclinometers are ma
167. or lenses An electrically actuated proportional pressure control valve is used to control the brakes The throttle is controlled by generating a pulse width modulated PWM voltage signal for the original engine 30 control unit Gear selection is already electrically actuated in the original truck An electrical servo motor is mounted in parallel with the steering wheel The original truck has a dual input steering gearbox which makes parallel installation straightforward 12 The hardware architecture of the control system is presented in Figure 8 The system is distributed over Ethernet at 100 Mb s 100BASE TX A conventional internet protocol suite is used Computing is distributed over several embedded computers One of the computers has an I O expansion board for gearbox and throttle control Two differential GNSS receivers with integrated IMUs are used in pose estimation for redundancy A wheel odometry signal is connected to the GNSS units to improve read reckoning performance during poor satellite reception One of them is configured to perform differential calculation with a satellite based augmentation system SBAS the other receives differential corrections via a V 24 V 28 serial link from a third agricultural GNSS receiver with a subscribed OmniStar correction service Obstacle detection is performed by three cameras and four scanning lidars two single plane and two quad plane models Only one of the quad plane lidars is used at a tim
168. orrection data through a traditional circuit switched connection 6 7 2 Wheel odometry Since the applications of the wheel loader include power train optimization and testing different pose estimation arrangements it was considered necessary to measure the angular velocities of all the wheels An encoder was installed on each wheel outputting incremental signals The velocities of 0 40 km h with direction indication were to be measured at maximal accuracy over the velocity range synchronized with the AFS angle measurement Therefore a special odometry algorithm and real time input processing were needed A simple application specific board was designed to be used with the generic embedded module Only a power supply and voltage dividers with transient protection to adapt the sensor signals to the logic level inputs of the microcontroller board were included on the board The microcontroller was programmed to read the inputs every 500 us and continuously calculate the angular velocity of 105 each wheel then transmit the result via CAN when requested by the higher level controller The request is done by transmitting a SYNC message as described in CANopen specification 16 6 8 Short range remote control Remote control of mobile machines is one of the research topics tested and demonstrated with the wheel loader For flexibility a general purpose radio modem link is used A compatible handheld remote control and communication protocol ar
169. ors of the microcontroller board need to enable mating with simple application specific boards preferably even a stripboard or breadboard The microcontroller board also has to include the minimum external components required by the microcontroller The microcontroller on the board has to perform at least simple digital filtering and other sensor related data processing in real time Simultaneously the microcontroller has to be able to process CAN traffic up to 1 Mb s at maximum bus load without losing messages To meet the minimal functionality there has to be at least 4 KB of non volatile program memory and 512 bytes of RAM Non volatile data memory has to be available for storing at least 256 bytes of application parameters such as filter coefficients scaling factors and communication settings The software development tools have to include at least a C compiler in circuit debugging features and a programming interface A well established high level development environment such as MATLAB Simulink or an IEC 61131 3 compliant environment such as CODESYS would support life cycle efficiency by minimizing hardware dependency of the application software The C compiler however is required when low level I O access and minimal processing overhead are needed The tools have to be convenient to use reasonably priced and reliable The hardware of the programming interface has to be commonly used and available or at least easy to design and build 5 1
170. ost optimization an embedded wireless module may be chosen to experiment with state of the art technology Embedded modules are often the first products that are commercially available when a new communication technology is released The recently introduced IEEE 802 15 4 2011 based ultra wide band UWB modules are a good example 91 As the embedded wireless modules are designed to be interfaced with a microcontroller a serial peripheral interface SPI Inter IC I C or UART is typically used If the wireless module does not have an integrated antenna the antenna signal has to be routed to an external antenna Care has to be taken to maintain the characteristic impedance of the antenna terminal in circuit board design in wiring inside the enclosure and in a possible panel connector Especially with ICs an impedance matching circuit is often needed to match an external antenna to the antenna terminal of the IC If the module has an integrated antenna the enclosure material and model have to be chosen carefully to minimize attenuation of the radio signal To interface a wireless module with the on board control system of a machine embedded software is needed The requirements for the software depend heavily on the application and the features of 61 the wireless module sometimes simple data routing between CAN and SPI is sufficient sometimes all the functions of a wireless network layer need to be implemented 3 4 4 Mobile Internet acce
171. over this enables the control systems of manual and automated machines to be developed and maintained side by side In addition to CAN automated functionality usually requires a network with a high data rate Ethernet being the only practical solution For configuration and maintenance an ideal combination of technologies would be CANopen and POWERLINK or DeviceNet and Ethernet IP Since industrial Ethernet protocols are not widely supported by GNSS receivers laser scanners machine vision cameras etc a standard Ethernet with conventional internet protocol suite is almost mandatory Special attention needs to be paid to scheduling analysis and connector solutions In addition specific devices require V 24 V 28 serial ports or an IEEE 1394 interface However GNSS receivers lidars and machine vision cameras for example have recently become widely available also with Ethernet interface Although USB has severe limitations in mobile machinery applications it is a feasible option for interfacing mass storage especially removable flash drives Addressing to the second research question the essential device related design aspects concern the power supply embedded computing and advanced sensing The electronic control system for automated operation may increase the loading of the electrical system compared to a manually 132 operated machine On the other hand an automated machine may not need as many lights as much seat heating etc It is o
172. ower supply and thermal design Desktop computers have a well established power supply specification according to Advanced Technology eXtended ATX documentation 8 pp 19 22 The ATX power connector is also one of the recommended connectors in the Embedded Platform for Industrial Computing EPIC specification for example 34 p 16 The ATX power connector however is rather large and the required power supply is rather complex with several regulated voltage outputs Although there are automotive versions of ATX power supplies available 74 an embedded computer may have a simpler power connector some even operate from a single voltage supply As the power supply specifications are not strict there are several different solutions between manufacturers and models In addition to supplying the embedded computer itself the expansion boards and other peripherals need to be considered the total power consumption may increase considerably with these devices installed Moreover even if the computer itself operates from a single voltage supply it does not necessarily generate all the regulated supply voltages for the expansion buses Although embedded computers have lower power consumption than desktop computers thermal design may still be a challenge Embedded computers are often available as conduction cooled versions Without a fan it is easier to make the enclosure of the computer water and dust proof Nevertheless a fan or other additional coo
173. ox eke Bodas RC36 Auxiliary Cabin Sensors actuators wireless g Wl bait valves uttons 3 k l Valve driver lift sensors i amp LEDs Joystic Wireless module with Ethernet switch Acksys WLg ABOARD N Valve driver tilt Display Hydrostatic drive Sg Diese pump engine DGPS receiver Trimble SPS351 Remote control Radio modem module BR M4 steering DGPS correction module smallTRIP Emergency stop Proportional valve Radio modem module BR M4 auxiliary hydraulics Wheel odometry L I I I I I r I I I H Proportional valve l I L I I I I L I I I CAN1 250 kb s CANopen CAN 4 500 kb s CANopen module CAN2 250 kb s CANopen Ethernet 100 Mb s internet protocol suite Angle resolver CAN 3 250 kb s J1939 V 24 V 28 9 6 kb s 38 4 kb s articulated frame Figure 26 Control system layout As many components of the hydraulic system as possible were chosen to have integrated electronics with a CANopen interface The CAN devices are grouped into four buses Since the only SAE J1939 devices are the diesel engine and the joystick they are connected to the same bus The CANopen devices are divided into three buses based mainly on device functionality to balance the bus loads Some of
174. pes and applications The specifications also cover system management process and interfaces between CANopen software tools 87 Therefore CANopen devices can be replaced with a similar product from another manufacturer rather easily Conformance tests are not mandatory which has contributed to extending the CANopen product range On the other hand some of the devices that have not been tested for conformance do not fully meet CANopen specifications CIP is the application layer protocol of DeviceNet which is managed by ODVA Inc The manufacturers of DeviceNet equipment are closely linked to ODVA to maintain product conformance This in contrast makes developing new products more difficult Most DeviceNet products are targeted at industrial automation Because a CAN frame is simple and networks of only a few devices are common implementing light system specific protocols is often fast and easy However considering the life cycle of mobile machines a commonly used protocol makes maintaining and extending the control system more efficient Because most application layer protocols have minimal overhead and flexible options for timing system specific protocols have no performance benefit Although CAN is the current industry standard in mobile machine control systems it is likely to be eventually replaced with a faster network CANopen and CIP are already available as deterministic real time protocols on Ethernet for example 36 83 Moreover
175. pplications There are cameras targeted at mobile machinery for reversing and work area monitoring for example For machine vision and remote operation on the other hand special arrangements are often required 4 7 1 Machine vision Typical cameras utilized in machine vision applications have high performance image sensors and replaceable lenses for optimizing focus and framing for example The cameras typically communicate over IEEE 1394 Ethernet or USB There are also digital interfaces targeted especially at machine vision and other video applications such as Camera Link CoaXPress and Serial Digital Interface SDI These specifications include higher layer protocol definitions improving compatibility between camera models On the other hand these digital video interfaces require an adapter that is not included in embedded computers There are also well established higher level protocols for general purpose interfaces such as GigE Vision for Ethernet Depending on application the timing accuracy requirement between cameras may be high This is the case in depth perception by stereographic imaging for example In some cases the accuracy achievable via software triggering is not sufficient Many cameras support triggering by hardware inputs and produce a strobe output for triggering a slave camera or an external flash Unfortunately these on off inputs and outputs are implemented with various circuits and signal levels that typically requ
176. quired to cover the working site of an automated machine Depending on application fast roaming or handoff between APs may be needed A procedure for fast roaming with encrypted IEEE 802 11 communication has been standardized by IEEE in 2008 58 but proprietary solutions still exist Different methods for vehicle use are compared by Kwak et al As the AP is selected by the mobile node the handoff performance depends mainly on the on board hardware Wireless adapters may support fast handoff directly or with updated driver software Some proposed schemes even include using an on board localization system to assist in fast handoff 67 Vernersson et al have compared general purpose and vehicular versions of IEEE 802 11 communication in a quarry environment a likely application of an automated mobile machine Although the vehicular IEEE 802 11p equipment has a lower data signalling rate it provides higher range and reliability in the tests 122 Furthermore Demmel et al demonstrate how the speed of the vehicle affects maximum range communication delay and packet loss in IEEE 802 11p communication The results imply the performance is affected very little when travelling at 50 km h for example 24 60 3 4 2 Radio modems When a point to point wireless connection high reliability or long range is required a radio modem may be preferred over IEEE 802 11 based networking Radio modems typically have a V 24 V 28 serial interface that e
177. r the high level control system This decision is made because the odometry data can also be applied in low level speed control To optimize the synchronization of the IMU and odometry data they are connected to the same network In addition the installation locations of these sensors are close to the devices of the low level control system The sensor signals from four wheels are processed by the wheel odometry module before transmitting the odometry data over CAN The odometry data of all wheels is thus synchronized and optimal odometry algorithms are applicable Moreover the steering angle signal is available on the same CAN from one of the CANopen position sensors and can be synchronized with the other pose estimation signals The high level control system is distributed over Ethernet as proposed in Figure 13 since all the included device types are available with an Ethernet interface To enable machine vision as defined in Table 1 1000BASE T is chosen Conventional internet protocol suite is applied since camera and lidar protocols are typically based on UDP The separate CAN Ethernet bridge improves life cycle manageability since neither an embedded computer with a CAN interface nor a mobile PLC with an Ethernet interface is required Utilizing CANopen J1939 and Ethernet with internet protocol suite in the control system enables diverse future modifications and extensions Replacement devices are widely available Moreover future automotive an
178. raightforward within the xPC Target models Moreover the on board Ethernet switch had a spare port making the hardware installation straightforward Initial tests showed that although there was a marine beacon transmitter located at a distance of 125 km its signal could not be received reliably To make the machine independent of the working site a commercial grid based correction service Trimble VRS DGPS was selected The position data of the DGPS receiver is transmitted to the Ntrip server over mobile Internet every 10 seconds An optimal set of correction data for the current working area is then received from the server every second For this communication an embedded mobile Internet module with Ntrip client functionality was installed The module has a V 24 V 28 compliant serial port for communication with the DGPS receiver The receiver outputs position data according to NMEA 0183 and receives the correction data according to the RTCM specification The DGPS receiver also has Ntrip client functionality This however requires that there is Internet access from the on board Ethernet Utilizing the separate module as the Ntrip client enables correction data to be received almost anywhere without on site wireless Internet access Moreover with the external module it is possible to keep the embedded computer and the DGPS receiver entirely separated from the Internet for improved security The module can also be used as a modem for receiving the c
179. rate sudden loss of power supply This sensitivity is typically related to storing data during operation For example a write operation to a flash memory must not be interrupted to ensure data consistency Unfortunately flash memory has to be erased in most cases before the write cycle and erasure is only possible by pages Therefore modifying a single byte requires erasing and rewriting several bytes For example the worst case duration of the write sequence to internal data flash with a Freescale 56F8323 microcontroller is over 25 ms consisting of a 512 byte page erasure and 256 consecutive 16 bit write operations 1 2 Since the flash write sequence is rather short and does not consume much power the problem can be avoided at device level by monitoring the external supply voltage and preventing write cycles to flash if the voltage falls too low 83 If this happens in the middle of the write cycle the internal capacitors of the device have sufficient energy stored for completing the cycle Not all sensitive devices have a built in mechanism for surviving the sudden loss of power Some cannot react as rapidly as simple microcontroller devices Embedded computers with full scale operating systems perform shutdown scripts to prevent file system errors and to ensure proper boot up next time Running these scripts sometimes takes several minutes In this case the energy needed for completing a shutdown script cannot be stored in a reasonably size
180. re simple resistive sensors have the same problems as devices communicating by voltage signal In addition resistive sensors may require biasing or bridge circuits In general current signals are more tolerant of interference Most devices use an established current range of 4 to 20 mA This makes a generic approach easier Moreover a sensor may operate with two conductors as no separate ground conductor is needed Compared to voltage signals this can reduce cabling substantially 47 3 1 2 Pulse signals Voltage pulses that carry signals in either frequency or pulse width are quite convenient in the sense of interference They can be connected to conventional digital I O However for high frequencies or accurate pulse widths a dedicated pulse I O with hardware timer or counter or both is needed Pulse signals are often transmitted by open collector circuits Therefore external pull up or pull down resistors are required depending on the circuit Rating these resistors depends on the type of the output transistor supply voltage maximum pulse frequency and accuracy requirements Moreover mobile I O modules typically have no convenient way of installing external resistors This may result in the need for separate enclosures or connector blocks for resistors Because of this most pulse signal devices are not easily interchangeable On the other hand a single product may be configurable for several operating voltages A special case of pu
181. re the swing boom stick bucket and track movements are controlled by the electronic control system Angular resolver sensors are mounted at each joint Pressure sensors are installed to measure the actuator force of each hydraulic actuator Perception is performed by two scanning lidars mounted on the roof of the excavator There are controlled platforms that are used to point the lidars The computer for automated functions consists of an array of four processors Cannon has the main focus on dig planning The developed planner is a perception based system that exploits models of excavator dynamics and soil tool interaction 15 Ha et al present an experimental automated excavator A commercial small excavator is modified for electrohydraulic operation According to Le et al the machine has eight hydraulically controlled movements tracks cab swing boom swing boom stick bucket and backfill blade Mechanically controlled valves have been replaced by electrohydraulic servo valves Additional hydraulic components required by the servo valve are added The servo valves are equipped with spool position sensors Actuator pressure sensors are installed on the hydraulic system and load pins on the excavator joints Rotary absolute encoders are fitted to joints with timing belts Encoder installations are protected by steel guards Closed loop control of the actuators is performed by proprietary digital control modules An industrial computer with a Wi
182. re is needed if there is no dust and waterproof control cabinet available for installation The connector type can be changed from 8P8C into M12 on the enclosure panel with an adapter see Figure 12 70 p 45 100 p 240 103 pp 94 95 However even inside the extra enclosure conventional 52 8P8C connectors are still vulnerable because of the mechanical vibrations and shocks of the machine There are robust 8P8C products but both the plug and the receptacle need to be of the same product series 14 pp 46 51 103 104 they are more expensive and require more space than M12 connectors Although there is a standard that specifies robust 8P8C connectors for industrial networks 54 various manufacturer specific connectors are widely used Most robust 8P8C receptacles however accept the regular 8P8C jack which makes testing and configuration in clean and dry locations easier as no special cables are needed Figure 12 Adapters between M12 and 8P8C for panel installation 103 p 94 Excluding obsolete coaxial cable implementations Ethernet typically has a star topology with a switch or a hub in the centre A daisy chain is also possible if all the devices have two physical Ethernet ports Regardless of the topology the physical layer of Ethernet is more expensive to implement than CAN for example At the moment there are not many Ethernet devices available for motion control of mobile machines However considering embedded compu
183. rfaces may follow Many sensors and actuators are available with an analogue or a digital interface Because the analogue versions have lower pricing digital versions are used in commercial systems only when the benefits are clear A digital interface is usually slower to develop than the analogue version Therefore when a new device is introduced onto the market the version with analogue output is sometimes released first Furthermore some devices are targeted at completely analogue processing Especially with high frequency signals digital processing may not be reasonable Unlike digital interfaces an analogue signal does not include any information on the relation between the measured physical quantity and the electric signal Therefore gains and offsets need 46 to be defined for all analogue signals These may differ even between two similar devices from the same manufacturing batch Regarding modularity this is a key problem common to all analogue interfaces Interference is a common problem with analogue signals In a mobile machine the electric power supply is typically an alternator with a battery The alternator is an AC generator with a rectifier Therefore the output voltage has a ripple with a frequency that is proportional to the rotation speed of the engine The battery does not attenuate the alternator ripple completely but it remains a significant source of interference through both conducting and radiation Other potentia
184. rked with numbers 1 2 and 3 respectively The inclinometer module has been developed at the Department of Intelligent Hydraulics and Automation utilizing the same microcontroller and software development tools as with the generic embedded module 50 The inclinometers have MEMS accelerometers which have a limited bandwidth This is not however considered a problem in this application The inclinometers also have MEMS gyroscopes that can be enabled in case the bandwidth has to be extended The inclinometers have a CANopen compatible interface so they are simply connected using 4 pole cables that supply power and communications Figure 30 Inclinometer installations on excavator 121 Because there is no inclinometer installed on either the wheel loader or the excavator frame the actual joint angle of the base boom cannot be calculated as the difference between two sensor signals It is however possible to use inclinometer 1 alone for relative measurement of the base boom angle assuming the wheel loader stays at rest Moreover it is possible to cancel the offset every time the wheel loader has been moved by lifting the base boom into a known angle Nevertheless lifting the entire machine during operation for example by pushing the excavator bucket against the ground generates an error that is not straightforward to detect 7 7 Video Video cameras were installed for demonstrating direct teleoperation of the excavator without line of
185. s 1 3 Related research There has been active publishing in the field of automated mobile machines since the 1990s The machines that are discussed in most publications have been built as proof of concepts or for use as research platforms Control system architecture and hardware are however usually neither 19 described nor discussed in detail and the emphasis is often on control algorithms and performance The automated machines that are most comprehensively discussed in the literature and therefore covered by this section are developed for cargo handling agriculture mining and earth moving applications This section also covers research on automated off road capable vehicles with advanced sensing and computing often targeted at military applications 1 3 1 Systems integration and management over machine life cycle Saha proposes several methods to improve the life cycle manageability of electronic control systems These apply to hydraulic mobile machines with conventional digital and analogue inputs and outputs especially The methods include extending the scale of controller area networks CAN with switches and splitting the electronic hardware platform into a logical and a physical platform Then the logical architecture that is the functionality of the control system could be implemented and maintained in hardware description languages HDL independent of the physical platform 99 To enable this in system reconfigurable mi
186. s The maximum length of a frame with inter byte space is specified to be 140 of the nominal transmission time including bit timing tolerance If the jitter in master task timing is not significant each frame slot has to be at least 75 6 nominal bit times 73 Substituting Ta 8 and Ts 75 6 to 1 we get Ry Rp 0 11Ry 2 Most networks have similar efficiencies when a frame carries minimal payload data because addressing and error checking typically form a fixed overhead However the problem is emphasized with LIN because M is low Therefore at the full data signalling rate of 20 kb s the network of 8 bit sensors would have a maximum throughput of only 2 1 kb s Since LIN is targeted to be a low cost technology for automotive manufacturers commercially available LIN products are mainly automotive ICs not robust I O modules However slave I O ICs can be used to develop simple generic I O modules that can be configured according to the LIN work flow 79 111 112 56 3 2 5 IEEE 1394 IEEE 1394 is a high performance serial bus for computer peripherals for example Depending on interface generation an IEEE 1394 interface uses a data signalling rate of up to 3 93 Gb s The interface is often called FireWire according to the brand name of Apple Inc the original developer The specification includes different physical transfer mediums but the most common is short haul copper cable It typically has a maximum length of 4 5
187. s amongst others Exceeding the rated current of an alternator will decrease its life The longer the overcurrent condition lasts and the more often it occurs the more it will wear the alternator Therefore when choosing an alternator for an automated machine it has to be taken into account that the battery may be notably discharged at an average start Moreover since the output current of an alternator is limited by its rotation speed the entire output current of an undersized alternator may be 64 consumed by the electrical loads in the system when the engine is idling preventing the battery from being charged Therefore not only the nominal or maximum output current but also the output current when the engine is idling has to be considered when selecting an alternator 4 1 2 Battery type As mentioned above the control system of an automated machine is operated for various reasons when the engine is not running This has to be taken into account when defining the required capacity of the battery For machines used in research and development it is reasonable to have connectors for an external power supply to enable long tests without extreme oversizing of the battery The type of battery has to be chosen carefully If the entire control system is not switched off when the engine is stalled it has to be considered whether a battery that tolerates deep discharge is required Moreover the battery voltage should not drop below the supply
188. s these result in a maximum length of a couple of metres 113 114 In mobile machinery applications USB has connector limitations similar to IEEE 1394 3 3 Comparison of key parameters Key parameters of the presented bus and network technologies are compiled in Table 2 The number of plus signs in the application programming interface API column is intended to give a relative impression of the extent of software support The rating is based on driver or API availability for different operating systems likely to be used in automated mobile machinery the estimated effort of writing a driver or API for unsupported operating systems and the complexity of writing software using the API It is also considered to be a clear advantage if the APIs of different vendors comply with a standardized or otherwise well established specification All of this applies to the communication interface itself but also the connected devices The availability of different protocol stacks is also considered The device availability column lists devices that are available with the network or bus interface in question The lists are not exhaustive but reflect the device types that are commonly used in automated mobile machines 58 Table 2 Comparison of on board data transfer solutions Max data Max f f i Physical ote signalling segment API Device availability topology rate length 25m power train PLC general I O bus sensors GNSS rec
189. s and spatially and temporally variable satellite to earth communication delay a GNSS receiver achieves only an accuracy of several metres unless these error Sources are compensated Most of the effect of the communication delay can be cancelled by dual band reception because the ionospheric delay depends on carrier frequency Dual band receivers are more expensive however and still need to compensate for orbit and clock errors Since the total error varies with time and receiver location a fixed reference receiver can be set up near the site as a base station to cancel the error Some GNSS receivers have an internal wireless module for receiving the differential corrections from a local base station However not all internal radios are compatible and they may have insufficient range External radio modems can be applied in these cases as most differential GNSS receivers accept the correction data via V 24 V 28 serial port It is also possible to use a modem for mobile networks for point to point communication or even Ntrip over mobile Internet The accuracy of the differential GNSS declines as the distance to the base station is increased Depending on the required positioning accuracy however the acceptable distance may be more than a hundred kilometres It is therefore not always feasible to have a dedicated base station for each site If a base station is made available to several GNSS rovers at different sites the correction data is typically tr
190. s were considered sufficient For flexibility and small size a separate CANopen compatible module was designed and built for controlling the starter the glow plugs and the stop solenoid Since the design of the generic embedded module was not finished at the time another prototyping microcontroller board with some similar features was used The same software development tools and programming hardware were utilized However the applied microcontroller board has a larger size inconsistent board to board connector arrangement lower performance and no option to install a V 24 V 28 transceiver or bypass the CAN transceiver Since the applied board was not designed for long term utilization there are no more compatible spare boards available However the generic embedded 119 module has the I O and performance to replace the utilized microcontroller board The application specific board however would need to be redesigned to match the board to board connectors of the generic embedded module The low level motion controllers and CANopen master functionality were implemented on an embedded computer running simple embedded GNU Linux The DM586 computer also has a bright monochrome display for presenting sensor signals and adjusting control parameters The motherboard has interfaces for CAN V 24 V 28 serial and Ethernet There is soldered flash that can be used as a system drive The software was developed and compiled on a laptop running a binary c
191. search on automated mobile machines on the other hand is concentrated on describing the performance of the developed automated functionality Although hardware architectures or lists of utilized devices are published the development process of the hardware architecture of the control system is not discussed in detail Life cycle manageability in particular is not discussed probably since the developed systems are not intended for long term operation Contribution of this thesis Life cycle manageability of control systems Automated functionality Mobile machinery Figure 10 Contribution of this thesis in relation to previous research 36 The scientific contribution of this thesis is the following Feasibility assessment of different digital networks and buses for automated mobile machinery The feasibility assessment is done in Chapter 3 The key characteristics are compared in Table 2 and a proposed arrangement to utilize different data transfer solutions is presented in Figure 13 Compilation of hardware specific challenges and design aspects in the electronic control systems of automated mobile machinery The challenges and design aspects are discussed in Chapter 4 In particular a proposed workflow for specifying the voltage of a battery system is presented in Figure 15 and a proposed reference hardware architecture of an automated mobile machine is presented in Figure 20 Design of a generic embedded module for interfa
192. sion for Maritime Services real time kinematic SAE International formerly Society of Automotive Engineers Serial Digital Interface single inline package serial peripheral interface solid state drive transmission control protocol user datagram protocol uninterruptible power supply Universal Serial Bus ultra wide band Virtual Reference Station 1 Introduction The constant development in heavy machinery aims at higher efficiency easier and more comfortable operation and lower maintenance costs These goals can be reached by increasing the level of automation and implementing sophisticated operator assisting functions These functions have already been introduced in many fields of heavy machinery There are even autonomously navigating and operating machines available for certain applications According to Prescott the development is likely to continue and cover more and more fields of heavy machinery This is predicted to have a substantial effect on the market eventually 90 Meanwhile utilizing another disruptive technology the Industrial Internet or the Internet of Things also requires similar equipment to be installed on manually operated machines 1 1 Background Traditionally the control systems of hydraulic heavy machinery have consisted of mechanical and hydraulic components With machines like these design production maintenance and spare parts service can be straightforward Even several decades after the original
193. sk analysis The safe reaction to the emergency signal depends on application In this thesis the discussion is limited to situations where stalling the engine and activating the brakes is considered safe Depending on how a site or a machine is monitored one or more handheld button units or a site wide infrastructure may be needed When testing new sensors and software with research machinery an additional run wait function makes testing more fluent Moreover an automated machine may be operated manually on board for maintenance or transport In these cases operation without the wireless emergency stop system may be desired which has to be taken into account in specification On a multi machine site an emergency stop may be global machine specific or zone specific The emergency stop system may implement one or more of these The more emergency stop types are implemented the more complex and more difficult to verify the emergency stop system becomes The same applies to zone specific emergency stop if a machine operates in more than one zone Another challenge is posed if the number of simultaneously used button units in the system needs to be flexible There are commercial wireless emergency stop systems available They are rather expensive and typically targeted at simple applications Where these off the shelf systems are sufficient they may still reduce the overall cost as less verification work is needed However customized I O software
194. some functionality may remain mechanically or hydraulically controlled For example automated driving requires electrically controlled acceleration braking steering and gear selection but working actions may still have mechanical control levers Automated functionality often requires sensors that are not present in manually operated machines Measured quantities are for example the positions of work mechanisms hydraulic load pressures and centre link angle in an AFS machine In some applications limit switches are sufficient but usually actual sensors are needed For automated drive the angular velocities of wheels global position and orientation of the machine and inertial signals typically need to be measured Depending on the level of automation also different types of cameras radars lidars or ultrasonic sensors are required 41 2 2 2 Requirements for on board data transfer The control system of an automated machine implements several closed loop controllers which increases the number and transmission rate of sensor signals compared to a manually operated machine In addition sensors with high output data rate are utilized Approximated payload data rates of different device types are listed in Table 1 Devices that do not involve cyclic data transfer are omitted Table 1 Data rates of device types Size of one Device Rate Hz Data rate measurement cycle Diesel engine 12b 50 600 b s target rot
195. sputers became obsolete soon after the results of the project were published 27 a Base Pilot station T805 Radar Navigation Control Safety and condition monitoring DoF H 1420 T805 T805 Radar T805 collision i data Radar ER T805 e T420 T420 Safety and mil H T420 condition Gj E T420 sensors Encoders Hydraulics Figure 1 Modular computing platform of the AGV adapted from 27 More complex automated machines have also been developed for cargo handling Durrant Whyte et al present an automated eight wheeled straddle carrier AutoStrad The machine Figure 2 is based on a manually operated straddle carrier Both straddle legs of the prototype machine have a diesel engine with a semi automatic gear box The machine has hydraulic all wheel steering and load lifting The four wheels of each straddle leg are mechanically linked to produce symmetric steering The actuators and sensors are connected to a programmable logic controller PLC via CAN The PLC monitors and regulates vehicle health based on hydraulic pressures and oil temperature for example The functional architecture of the control system is rather similar to the previously described AGV but the hardware of the control system is different The system controls the engines gear boxes steering brakes hoist and lights of the machine 28 21 Figur
196. ss In addition to voice calls and messaging mobile networks provide Internet access The main benefit in mobile machinery applications is that the mobile data terminal is able to communicate over the Internet without any local wireless AP Therefore no setup work is required for communication when a machine is moved to a new site as long as the site is within the coverage of a mobile network Unfortunately the network throughput can be less than 10 kb s and communication delay can be several seconds if only general packet radio service GPRS is available Moreover the performance varies depending on other mobile communication and cell distance The change can be considerable at handoff from one cell to another 11 Fourth generation 4G technologies enable much better performance network throughput of several Mb s and a communication delay of less than 30 ms Nevertheless the handoffs between cells can still have a considerable effect 126 3 5 Applying data transfer to automated mobile machine A proposed utilization of the presented data transfer solutions in the control system of an automated mobile machine is presented in Figure 13 For distributing the computing of low level controllers CAN and Ethernet are the only feasible solutions with sufficient flexibility robustness and real time performance For mobile machine applications there are diesel engines sensors hydraulic valves and pumps etc available with an integrated CAN in
197. tage is presented in Figure 15 assuming the selection has to be made between 12 V and 24 V The process aims at minimizing the size and cost of the system as well as conversion losses First the devices of the control system are classified by supply voltage Since the actual voltage of a battery varies between the low cranking voltage of a partially discharged battery and the maximum output voltage of the alternator many devices that are not intended for mobile machinery or automotive applications cannot be powered directly from the battery Devices like this need to be supplied by a separate voltage regulating direct current to direct current DC DC converter In the flow chart these devices are classified with the opposite voltage 12 V unregulated with 24 V regulated and vice versa This is done because a non isolating DC DC converter that has either a step up or a step down function is smaller simpler and has a lower cost than a converter that performs both functions This more complex converter type is required if a regulated 24 V supply is converted from a battery voltage of 24 V for example On the other hand if an isolating DC DC converter is used there is no extra cost for having the output voltage within the input voltage range In this case the devices that require a regulated supply can be left out when making the decision about the nominal voltage of the battery system Depending on the application isolating DC DC converters may be req
198. ted functions typically embedded computers are required Some sensors also require complex driver software or physical interfaces that are only available for embedded computers with an expansion bus 74 Depending on the application several embedded computers may be required For example real time processing of high resolution images may consume all the available performance of a dedicated computer Especially in experimental systems several computers also enable efficient simultaneous development of different subsystems Furthermore several different operating systems may be needed on board The need can be related to different real time requirements driver support available software libraries and preferred tools for software development and testing 124 In general embedded computers are compatible with laptop and desktop computers the same processor families expansion buses operating systems and even some peripheral devices are used The dimensions or expansion bus connectors are however different Several specifications for different physical platforms have been released with different emphasis on cost size mechanical robustness and performance 29 34 78 89 The expansion boards of desktop or laptop computers are therefore not mechanically compatible with many of these specifications 29 34 89 Therefore the selection of the physical platform has to be made by considering the available expansion boards as well 4 3 1 P
199. tem drives SSDs are available for system drive use with optimized internal cache RAM and with industrial grade ICs for example Nevertheless there are differences in wear levelling solutions and system drive performance between SSD models as well In case neither the operating system nor the applications write data on the system drive the effect of write speed and write cycle endurance may be ignored This can however limit the flexibility of the system 4 3 3 Remote access Since embedded computers are compatible with conventional peripherals it is typically possible to install an operating system and application software by plugging in applicable USB devices and a display This approach however is typically not convenient for accessing the computer after it has been installed on a machine Access may be needed for updating the operating system or application software testing starting on board data logging or downloading logged data On some systems the applications are even compiled on board If the computer has a network interface remote access software can be used In this case a network patch cable is connected either directly to the computer or to a network switch If there is a wireless connection a remote accessing computer can be located more freely In case there is no remote access software available for the operating system the files on local mass storage can be managed by booting the computer to another operating system that
200. ter This was convenient as the valve drivers of the working hydraulics communicate over the same CAN The layout of the control system after the described modifications is presented in Figure 27 Comparing to Figure 26 it can be seen that the original arrangement of one Ethernet and four CANs has been maintained 111 Automated functions Embedded computer Hurricane QM57 Co 1 Motion control Main PLC a Bodas RC36 Sensors actuators wireless i S cies Val lif valves uttons ick alve driver lift I sensors i8 LEDs Joystic Wireless module with l Ethernet switch L Hydrostatic drive Diesel Acksys WLg ABOARDIN Valve driver tilt i y pump engine DGPS receiver Display i Trimble SPS351 r Proportional valve Volume counter i BR M4 steering Remote control I DGPS correction module module 7 smallTRIP Radio modem t Proportional valve BR M4 auxiliary Emergency stop hydraulics Radio modem module l L Wheel odometry CAN1 250 kb s CANopen CAN 4 500 kb s CANopen i module CAN2 250 kb s CANopen Ethernet 100 Mb s internet protocol suite l Lj Angle resolver CAN 3 250 kb s J1939 V 24 V 28 9 6 kb s 38 4 kb s articulated frame Figure 27 Control system layout after modifications 6 12 2 Meeting requir
201. terface Connecting similar devices to Ethernet has to be done through generic I O modules with analogue pulse and on off signals With Ethernet however a much higher network throughput can be achieved This makes it possible to distribute the entire computing and 1 O of the low level control system over a single Ethernet instead of several CANs Several embedded computers are required for navigation perception and other high level controllers Ethernet is the most feasible network technology for communication between these computers due to performance software support and cost Ethernet is also the most utilized solution for communication between embedded computers in the related research discussed in Chapter 1 To meet the data rate requirements listed in Table 1 at least 1000BASE T has to be selected Ethernet is a common interface in machine vision cameras lidars GNSS receivers and other sensors related to perception and navigation Utilizing other digital buses is however mandatory when experimenting with specific sensor products 62 Computing of navigation perception high level control Ethernet Wireless V 24 V 28 serial USB Sensors for perception localization Ethernet IEEE1394 V 24 V 28 serial Ethernet CAN Wireless V 24 V 28 serial Sensors actuators pt pF l CAN Ethernet Computing of low level control E CAN Ethernet E Ethernet i in CAN LIN
202. ters wireless communication modules and various advanced sensor systems Ethernet is often the only reasonable option 3 2 2 1 Internet protocol suite The internet protocol suite often called TCP IP is the most common set of protocols used in Ethernet systems Although the internet protocol suite is a layered set of protocols it does not strictly comply with the OSI model Most of the suite is divided into application layer transport layer internet layer and link layer protocols 94 These layers do not have strict definitions Part of the data link layer of the OSI model is covered by the link layer of the internet protocol suite One of the key protocols of the link layer is address resolution protocol ARP which finds an Ethernet address for a destination internet address The pairs of Ethernet and internet addresses are stored into a translation table which is typically cleared at shutdown Therefore after boot up ARP communication takes place before the first transmission to each destination address 35 The main protocol of the internet layer is called internet protocol IP Its main functions are addressing and fragmentation of data packets from higher layers IP has a header checksum which makes sure the packet is addressed and fragmented correctly The data of the packet however is 53 not checked for errors in this layer IP has no mechanisms for acknowledgment retransmission or flow control either 60 Most application
203. th automated heavy machinery to be very rewarding am grateful for my family and friends as well wish to thank my parents Heikki and Liisa for encouraging me to consider doctoral studies Most of all wish to express my gratitude to Maija Oliver and Aada for their love support and understanding After all Mum is a teacher and dad repairs stuff Contents Abstract Preface List of figures List of tables List of symbols List of abbreviations 1 gt JURIDIC TIN 0 os ate eae ec elas eR A ee es eee el age Notes 17 la Backo OUA aa r Serene te eM E m ere See enrT een ene St my ean ten 17 1 2 SCOP Of eSis ere entender le eed ected ee 18 1 3 Related research rrine e odes emecmel Macatee ate eee 18 1 3 1 Systems integration and management over machine life cycle 19 1 3 2 Electronic control systems in automated cargo handling ee 19 1 3 3 Electronic control systems in automated Mining eeeeeeeeeeeee eee eeee 23 1 3 4 Electronic control systems in automated agriculture cceeeeeee 23 1 3 5 Electronic control systems of automated off road vehicles 00 25 1 3 6 Automated GxCavalloliieasiccete a cornea Aenea naune edt 28 133 7 DARPA challenges eii eieiei ai a a aa RERE EA ERRE 29 3 8 Summaya e e e ees a E eE pace edo a a dea eas elena ob ETE toes 34 Tc RGSS Arh QUGSHONS si test na a ETE A ETE i 34 1 5 Scientific COMMBUNON2 a es Snca ones cea ee taaen e
204. th the machine frame In addition to protecting the camera locking the mechanical adjustments of the lens has to be considered 4 7 2 Remote operation While automated functionality may rely on other perception sensors a camera is often the most convenient solution for remote monitoring and teleoperation Many of the requirements for a camera are in this case similar to machine vision applications Image quality however may be lower in many cases as long as the camera adjusts to the expected lighting conditions and has a sufficient field of view Another critical characteristic is a minimal transmission delay especially in direct teleoperation Some cameras with integrated digital encoding are therefore not fast enough for comfortable and safe remote operation The monitoring cameras that are targeted at mobile machinery applications can be applied to remote operation which simplifies mechanical and electrical installation However these cameras typically output an analogue video signal Although there are wireless transmitters for signals like this it is typically feasible to utilize the digital wireless communications of the control system For this an Ethernet video server can be applied There are automotive grade video servers for single or multiple cameras as well as analogue frame grabber boards for embedded computers Although implementing the video server on an embedded computer among other functionality seems cost efficient the fra
205. the communication between the tractor and the implement can be realized over ISO 11783 some proprietary messages are required Backman proposes ISO 11783 to be updated to define the communication in these cases 10 1 3 5 Electronic control systems of automated off road vehicles Green has researched path planning for automated off road vehicles in unstructured environments The algorithms are tested with a rugged amphibious vehicle although the tests are performed only on land The skid steered vehicle has eight wheels driven by a petrol engine a variable ratio torque converter and a manual gearbox with differential The skid steering is realized with separate hydraulic brakes for both sides An electronic control system for automated operation is retrofitted on the commercial vehicle An extra alternator and a deep cycle tolerant 24 V battery system were installed because the original 12 V system does not supply sufficient electrical power for the retrofitted control system especially when operating the engine at low speeds 42 Motor Control Payload Throttle Servo y Interface Payload i Vehicle Choke Servo Control oo sw A CPU E Gear Change UV a I Gear Motor Gear Encoder i Us eke ee Brakes and Skid Steer Navigation aay 5 PU S a i l g l D l gt STOP System Electrical Starter Fuel Pump a n ati Ignition otor Feedbac osition Feedbac Bra
206. the CANopen devices are designed built and programmed at the department since no applicable commercial products are available These include the digital hydraulic valve drivers and the modules for remote control emergency stop and wheel odometry All of these deploy the generic embedded module presented in Chapter 5 6 3 Main PLC The main mobile PLC of the control system was specified to have several CAN interfaces and versatile I O for conventional hydraulic valves analogue current and voltage signals and switches Moreover extra I O was considered essential for convenient future testing of sensors and actuators For further flexibility data processing performance was targeted to be high among the 100 conventional mobile PLCs Standardized or well established software development tools were also required BODAS RC36 20 30 from Bosch Rexroth was considered to meet the specifications The PLC has four CAN interfaces several analogue voltage and current inputs on off inputs frequency inputs and outputs for proportional and on off valves The microprocessor core has a multiply accumulator unit and an FPU The clock frequency of the core is 150 MHz and most arithmetic instructions can be repeated at least every third core clock cycle Software development can be done with BODAS design which is based on CODESYS tools and is IEC 61131 3 compliant Furthermore C development tools are available in case the flexibility or performance of BODAS
207. the control system to avoid file system errors Moreover the control system has to protect the batteries against deep discharge when the engine is not running With many devices protective enclosures with heating or cooling are required The electronic control systems of two automated machines utilized as research platforms are presented and discussed as examples The hardware architectures of the control systems are presented following the proposed communication solutions as far as is feasible Several applications of the generic embedded module within the control systems are described Several research topics have been covered utilizing the automated machines In this thesis a cost efficient operator assisting functionality of an excavator is presented and discussed in detail The results of this thesis give not only research institutes but also machine manufacturers and their subcontractors an opportunity to streamline the prototyping of automated heavy machinery Preface am grateful to professors Kalevi Huhtala and Matti Vilenius for providing excellent research facilities for automated heavy machinery as well as for their guidance at the Department of Intelligent Hydraulics and Automation Also wish to thank the entire staff of the department not forgetting the many old colleagues working outside the university nowadays for creating an inspiring and supportive environment for research Especially express my gratitude for valuab
208. the power steering gearbox A multi turn angular sensor is included in the electric motor for redundancy A microcontroller module performs close loop control of the steering angle Since the original engine has a mechanically controlled injection pump an automotive throttle actuator is modified and fitted on the engine The actuator consists of an electric motor with an integrated position sensor A microcontroller module is used to control the actuator angle The brake pedal is actuated by an electric motor with a reduction gear Torque based control is realized with a microcontroller module 116 The electrical system of the Hihglander is replaced by the system of a later model of the same vehicle to make transmission and engine control accessible in the software Although a suspended enclosure is installed for the embedded computers the sensors of the Highlander are mounted without extra suspension A 340 V switch reluctance generator supplies an electric air conditioning compressor and step down voltage converters for 24 V and 12 V devices The original steering system has been replaced by an electro hydraulic system A hydraulic rotary actuator is controlled by an electrically actuated proportional valve with integrated closed loop spool position controller The hydraulic power is generated by a fixed displacement pump A rotary sensor is mounted on the shaft of the rotary actuator The position of one of the cylinders of the rotary actuator is meas
209. ther option is to choose the cable gland according to connector diagonal and increase the diameter of the cable to ensure proper sealing This can be done by applying heat shrink tubing that has a high shrink ratio for example Furthermore the 9 pin cable may be fitted through solid tubing that has a sufficient diameter Using cable glands the solid tubing forms a sealed channel between the enclosures Whichever the solution extra effort is required An IEEE 1394 interface is not included in a typical embedded computer A separate adapter board is therefore needed Although an IEEE 1394 interface can be implemented with low cost components industrial grade adapter boards for embedded computers tend to be considerably more expensive 3 2 6 Universal Serial Bus USB was designed for interfacing peripherals with a personal computer The latest version of the specification USB 3 1 has a maximum data signalling rate of 10 Gb s At the moment however most devices only support USB 2 0 which has a maximum data signalling rate of 480 Mb s The 57 USB network has a tiered star topology which requires a host that is connected to devices directly or via hubs The devices do not communicate with each other but only with the host USB 3 0 has more complicated cable and connector specifications than USB 2 0 Neither specification states the maximum length of a cable but only a limit for signal propagation delay and insertion loss With typical cable
210. to detect shouted warnings Four cameras are used to form a 360 view around the forklift for a remote operator Speakers a skirt of light emitting diodes LED and LED matrix displays are added to signal to humans whether the system has detected them and what actions the forklift is about to perform Many of the lidars and LEDs are visible in 23 Figure 3 Each sensor is connected directly to one of the four laptop computers A fifth laptop computer is used as a diagnostics display for the local operator A wireless access point AP provides remote access A PLC monitors heartbeat signals from higher level software run on the laptop computers and performs low level control 105 1 3 3 Electronic control systems in automated mining Marshall et al have developed a system for automated hauling with an underground mining vehicle with articulated frame steering AFS The system was tested with two machines originally built for manual operation Both have a modular control system that is distributed over CAN The system consists of ruggedized operator panels display modules I O modules and proprietary computational modules that tolerate the demanding mining environment The computational modules have a real time operating system 76 To enable automated functionality the machines were equipped with extra sensors and embedded computers On one of the machines an Intel Pentium III oased computer operating at 700 MHz was added On the other one
211. to implement fast current switching Another option is to utilize devices that have both high side and low side driving outputs In this case several I O modules would be applied to replace each 20 channel valve driver Careful scheduling analysis would be needed to ensure a deterministic communication delay to these I O modules The emergency stop system could be replaced with a commercial one but the CANopen interface would have to be implemented with a mobile PLC for example 113 The flexibility of the hardware architecture has been further indicated in the development of similar systems on other wheel loaders A smaller AFS machine with distributed low level computation 6 has been equipped with embedded computers a GNSS receiver wheel odometry and emergency stop modules In addition advanced sensors like lidars and machine vision cameras are connected via Ethernet The flexibility of the architecture also enabled rapid development of automated path following and digital working hydraulics on another wheel loader for industrial demonstration The frame of the wheel loader is similar to the one presented in this chapter but in this case the original mechanical parts of drive train and steering were preserved The machine was ready for demonstration six months after the functional requirements were specified The control systems presented in Chapter 1 have computers sensors and communication similar to the control system presented above The
212. uency or pulse counter input Moreover several wheels may need to be measured The measurement may need to adapt to both low and high angular velocities and therefore be able to not only count pulses but also measure cycle time To improve data fusion accuracy calculation may need to be synchronized with other measurements related to pose estimation Thus conventional mobile PLCs and I O modules are sometimes insufficient for wheel odometry especially when typical software development tools and default firmware are utilized 4 4 3 Inertial measurements To estimate the orientation of a machine and improve the location estimate inertial measurements are applied An inertial sensor is either an accelerometer for measuring linear acceleration or a gyroscope for measuring angular velocity An IMU typically consists of several inertial sensors arranged at perpendicular axes often both accelerometers and gyroscopes Depending on the application up to three perpendicular accelerometers and three perpendicular gyroscopes are needed If several discrete inertial sensors are used attention has to be paid to measurement synchronization communication mechanical alignment and calibration Although tactical grade IMUs are sometimes used in research projects they are expensive for mobile machinery applications IMUs based on micro electrical mechanical systems MEMS are applied instead There are devices with CAN communication wide supply voltage range and
213. uired to protect sensitive equipment from different ground potentials for example To create an isolated section the signal paths that cross the boundary of the section have to be isolated as well Another reason for choosing an isolated converter is that DC DC converters with sufficient mechanical and electrical robustness are not always available as non isolated versions In this case the ground terminals of the input and the output side of the isolating DC DC converter can be tied together if a common ground is required Some devices have a wide supply voltage range 6 40 V for example Although the range of the supply voltage can reach rather high most devices have internal circuitry that has a lower regulated operating voltage If the internal regulated power supply for this circuitry is implemented with a linear voltage regulator the efficiency of the device decreases as the supply voltage is increased Performance or maximum operating temperature may therefore be higher if the external supply voltage is lower Even the efficiency of switched mode voltage regulators depends on input voltage If there is no clear supply voltage dependence in performance devices with a wide supply voltage range can be classified into class A or class B The same applies to devices that are available as different versions with different nominal supply voltages The flowchart in Figure 15 tests whether a majority of the electrical load can be concentrated to a
214. ure 29 had not yet been installed Therefore an outdoor IEEE 802 11 wireless AP was mounted on the wheel loader In further research conducted by the Department of Automation and Systems Technology at Aalto University stereo vision was applied 106 Two machine vision cameras and lenses were installed inside a protective enclosure shown in Figure 31 on the left The lenses have set screws to lock the adjustable zoom and focus Since both cameras are fixed into one enclosure it is possible to move the entire stereoscopic system between research platforms without repeating stereo calibration Due to previously developed software and experience cameras with IEEE 1394 interface were selected instead of 1000BASE T Ethernet Since real time image processing is computationally demanding a dedicated LittleBoard 800 computer with a 3 channel IEEE 1394 adapter was installed inside the same enclosure In this way it was also possible to avoid problems related to maximum length of IEEE 1394 cables and utilize commercial Beta connectors Moreover it is straightforward to install hardware synchronization circuitry between the cameras if needed 7 8 Electrical power supply To be able to utilize the original starter and engine controls the 12 V electrical system of the commercial machine was preserved Most of the devices of the control system can be supplied directly from the battery system However it was noticed in initial tests that the battery has to be a
215. ured for redundancy A microcontroller module performs closed loop control of the steering angle The engine control unit of the updated electrical system has CAN communication The brake master cylinder is actuated by an electric motor with a reduction gear A microcontroller module performs torque based close loop control 85 116 32 The perception and computing system is similar in both vehicles one horizontally scanning long range lidar is mounted on an actively controlled gimbal This is done because the pitch and roll angles of an off road vehicle change rapidly during drive and cause distorted range measurements In addition to stabilizing the lidar the active control makes it possible to point the lidar at different areas of interest The stabilized lidar is used with two short range lidars for terrain characterization Another two short range lidars are used for detecting positive obstacles To improve perception performance through dust a horizontally scanning radar is also installed A dual antenna GNSS receiver with an integrated IMU and data fusion is used for pose estimation The pose estimation algorithm also uses odometry data A camera with IEEE 1394 interface is installed for documentation The computing is distributed over Ethernet 1OOOBASE T between 11 computers Seven of them are built of modular CompactPCI hardware with Pentium M processors The remaining four consist of modular PC 104 hardware based on Pentium Ill processors
216. utomated functionality it is often not practicable to have the computers communicating directly with all the I O modules As communication with the I O modules consists of small data packets that are transmitted at short intervals computing capacity would be consumed by network traffic processing The logical functionality of a manually operated machine is implemented with a mobile PLC instead The same PLCs can also be used in automated machines Since PLCs often have several interfaces for CAN and other networks they can communicate with other PLCs slave I O modules other networked devices and the embedded computers As PLCs are suitable for real time control at short control steps and some even have an FPU they are an appropriate platform for calculating low level functions These include position control of hydraulic actuators and AFS angle and travel velocity control by controlling the diesel engine and the components of the power train A PLC may also be used to synchronize events Although PLCs are available from many vendors most of the devices can be programmed with IEC 61131 3 compliant software development tools 4 3 Computing automated functions It is reasonable to calculate on board at least some of the algorithms that are required for automated functionality This applies in particular to real time calculation and processing of high bandwidth sensor data Although some PLCs have sufficient computing capacity for simple automa
217. ves need to have minimal stand by power consumption Moreover they need to switch to the low power state reliably The shutdown is now controlled directly by the main switch when the power supply to unprotected devices is disconnected the shutdown process has to be initiated For embedded computers there are automotive power supply modules that fulfil these requirements and switch to a low power mode after a set time even if the shutdown process of the embedded computer fails 74 It is possible to utilize a device without a low power state as the power management module with the circuit presented in Figure 18 In this case all the devices including the power manager module are powered through the main relay To switch the system on a double pole main switch is utilized one of the poles controls the main relay in parallel with the power manager module The other pole signals the power manager to initiate shutdown when the main switch is opened With this approach the power management functionality may even be distributed between several devices of the control system as long as the implementation is reliable All the diagrams of Figure 17 and Figure 18 include a device 3 as an example of how a device that tolerates sudden loss of power is connected When utilizing a power manager the device 3 consumes power while the sensitive devices perform a shutdown process If this power consumption is significant an extra pole of the main swit
218. wp content uploads 2013 12 canefpaper pdf J Leonard J How S Teller M Berger S Campbell G Fiore L Fletcher E Frazzoli A Huang S Karaman O Koch Y Kuwata D Moore E Olson S Peters J Teo R Truax M Walter D Barrett A Epstein K Maheloni K Moyer T Jones R Buckley M Antone R Galejs S Krishnamurthy amp J Williams A Perception Driven Autonomous Urban Vehicle Journal of Field Robotics Vol 25 Iss 10 2008 pp 727 774 Available http april eecs umich edu pdfs mitduc2008 pdf LIN Specification Package Revision 2 2A LIN Consortium 2010 194 p M4 ATX HV 6 34 V Intelligent ATX Power Supply Installation Guide Mini box com 7p Available http resources mini box com online PWR M4 ATX HV PWR M4 ATX HV manual paf G J Maeda D C Rye amp S P N Singh Iterative Autonomous Excavation in K Yoshida amp S Tadokoro eds Field and Service Robotics Springer 2014 Heidelberg Germany pp 369 382 Available http db acfr usyd edu au content php 237 html publicationid 1079 J Marshall T Barfoot amp J Larsson Autonomous Underground Tramming for Center Articulated Vehicles Journal of Field Robotics Vol 25 Iss 6 7 2008 pp 400 421 142 77 78 79 80 81 82 83 84 85 J Mikkola V Ahola T Lauttamus M Luomaranta M Linjama amp M Vilenius Improving Characteristics of On Off Solenoid Valves Proceedings of the 10 Scandinavian Inter
219. xed signal hardware is required Saha also demonstrates that a physical platform like this can be designed and built The example platform has a field programmable analogue integrated circuit IC which is used to implement reconfigurable analogue to digital converters ADC 99 Uusisalo compares distributed and centralized computation in small remote controlled wheel loaders Two machines developed to be used as research platforms are used as examples It is concluded that although distributed computation has the benefits of modularity and flexibility a complex application may also require some centralized computation An approach where the simple control tasks of an automated machine are computed by the devices of the actuator layer is suggested 121 1 3 2 Electronic control systems in automated cargo handling Durrant Whyte describes an autonomous guided vehicle AGV that has been developed for transporting cargo containers in a port environment The AGV has a hydrostatic power transmission with a constant speed diesel engine a variable displacement pump and variable displacement hub motors Steering is also realized with hydraulics The low level control of the hydraulic system is implemented using proprietary control units that can perform proportional integral derivative PID control Since the platform does not have a suspension system the protective central computer housing is suspended Pose estimation i e solving the position and
220. y problem with microprocessors however is their relatively short life cycle There are different compilers software development tools and hardware programming and debugging interfaces for each family of processors or microcontrollers As workstation hardware and operating systems tend to become obsolete within a few years maintaining configuration tools for older devices is often challenging 48 Digital communication can be optimized for data rate transfer delay distance cost or reliability The solution is always a trade off between some of these design parameters Since one bus or network cannot be optimal for everything there are dozens of standardized and established ways of digital communication Furthermore the rapid development of electronics and industrial competition constantly produce new digital buses and networks Updated specifications are backwards compatible in general but the rapid introduction of entirely new buses and networks tends to make the older ones obsolete In addition to physical specifications a communication protocol has to be defined Depending on the system different levels of the Open Systems Interconnection OSI model 55 are implemented There are typically several competing higher layer protocols for each physical layer Some of these protocols conflict with each other and therefore require separate physical layers Considering design production and maintenance of mobile machines it would be ideal to

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