A remote lab implementation using SAHARA
Contents
1. if _name__ __main__ parser argparse ArgumentParser description Execute an OpenOCD command parser add_argument command type str choices halt resume reset help Provide an OpenOCD command args parser parse_args main vars args sys exit 3 4 Remote Programming To program the Stellaris we have chosen to use OpenOCD one of the most popular open source in system programmers Once installed it is run from the command line with the location of the configuration file given as an argument It then verifies the JTAG scan chain specified and if successful starts as a daemon waiting for connections from telnet clients or the GDB debugger The most recent versions come with configuration scripts for the Stellaris EKS LM35S1968 so it is trivial to get working The UTS team opted to use a shell script for their bitstream upload script however we have chosen to use a simple Python program This is mainly due to our preference for Python along with the fact that the language has evolved such that there are libraries to accomplish most system level tasks In this case we are using the pexpect module short for Python Expect to communicate with OpenOCD via a telnet session Expect is an extension to the Tcl scripting language allowing users to easily create scripts which talk to interactive applications Here it is used to start a telnet session to OpenOCD reset the Stellaris microcontrol2. A number of other options were considered including an Arduino board and a purpose built USB to GPIO module However the FTDI has the best combination of features and price It meets all our requirements with the following features 9 1 Complete USB device mode protocol handled on chip without custom pro gramming 2 Complete USB hardware on chip including USB resistors 3 8 GPIOs available this will allow for future expansion 4 USB suspend and resume support to switch device to low power mode when not in use 5 Integrated level converter and 5 V 3 3 V 2 8 V and 1 8 V totem pole output so it can interface with most standard microcontrollers In this case 5V logic is used to interface with the Stellaris 6 No additional crystal or oscillator required In order to communicate with the FTDI chip the open source libftdi library is used Initially a simple breadboard circuit was constructed where an LED was connected to one of the GPIO pins of the FTDI chip as shown in Fig 5 A simple program was written and run to test that 1 The toolchain and libftdi library worked 2 The circuit was feasible http www arduino cc http www intra2net com en developer libftdi repository php 3 RIG CUSTOMISATION Nick Wareing 8 A remote lab implementation using SAHARA Figure 5 The GPIO signals are sent to the Stellaris microcontroller using an FTDI device 3 3 1 Reset Functionality The soft r
3. able to gain visual feedback on the performance of their code via a live video stream The central premise of remote labs is that universities around the world can install and host physical experiments which can be accessed by students over the In ternet 2 3 4 The idea holds great promise because it can enhance collaboration between universities by the sharing of expensive lab resources 5 and moreover allow students to work from wherever they are at whatever time of day suits Re mote labs can thus help flatten the demand for expensive lab resources and software is able to impose limits on the safe use of equipment As public access is not required to a remote laboratory they are more secure re ducing problems associated with theft vandalism and damage to equipment through inappropriate use Student safety is also improved through physical isolation from hazardous equipment These factors may have economic benefits in the form of re duced occupational health and safety OSH compliance costs and reduced insurance premiums Until recently the technological challenges involved in real time Internet com munication have limited the growth of remote laboratories However recent im provements and innovations in web technologies have rapidly begun to remove these impediments The University of Technology Sydney UTS has already imple mented a fully featured remote laboratory system In 2012 the Electrical and Computer Engineering
4. components in the remote micro controlled helicopter laboratory 2 SAHARA Nick Wareing 4 A remote lab implementation using SAHARA 2 1 1 Web Interface The web interface is the platform presented to students to interact with the physical lab It is coded in PHP using the Zend Framework along with HTML CSS and JavaScript It allows students to authenticate with the system using either a MySQL database or the university s LDAP servers Queueing and reservation functions are also supported The SAHARA library contains a number of elements which can be placed on a customised HTML5 page to support newly designed rigs 2 1 2 Scheduling Server The scheduling server forms the core of SAHARA It is written in Java and needs to connect to a MySQL database The scheduling server provides a web interface which lab technicians and lecturers can use to allocate access to specific rigs or entire classes of rigs 2 1 3 Rig Client The Rig Client is the component that receives user input and communicates with hardware It is usually installed on a machine that is physically close to the labora tory equipment to reduce the amount of cabling required Three Rig Client control types are provided by SAHARA 8 1 Batch Control The rig operates using batch instructions uploaded by the user No other intervention is required 2 Peripheral Control A rig has a controller that is outside of SAHARA 3 Primitive Control The rig i
5. department s existing server infrastructure Using VMs can provide a number of advantages including live migration reduced electricity usage and better distribution of computational load 12 At present authentication is local to the scheduling server using a simple con figuration with the username and password stored in a MySQL database When students start using the system it is desirable that they can use their existing Uni versity of Canterbury credentials SAHARA makes this transition to using LDAP lightweight directory access protocol simple changing a few lines of the configu ration file is all that is required 5 4 ENZCON Paper A research paper has been written and was accepted to the ENZCON 2013 confer ence 13 This was presented at Massey University in Auckland on 5th September 2013 5 DISCUSSION Nick Wareing 15 A remote lab implementation using SAHARA 6 CONCLUSION We have presented a new application of remote laboratories aimed at undergraduate Electrical Engineering students A complete system has been developed utilising the SAHARA remote laboratory framework It allows students to upload compiled code and monitor its ability to control the flight of a small model helicopter Currently two rig clients are in operation two helicopters The next stage of the project should add more advanced forms of feedback to help students debug their programs We are pleased with the success of this remote laboratory im
6. in Java and utilises several third party libraries In order to design a customised rig a developer creates a new Java class which extends the AbstractControlledRig class The Rig Client program loads in this class at runtime after specifying its presence in a configuration file Our customised HeliRig class has four main features 1 Facility to take the compiled student program from its temporary upload di rectory or the demo program and flash it onto the Stellaris Microcontroller 2 Facility to channel virtual button presses to specific pins of a USB to parallel device 3 Reset functions which the Rig Client runs after a student finishes using the rig to ensure it is ready for the next user 4 Test functions which run periodically by the Rig Client to determine if the rig remains in a working order These features were developed in an iterative manner with each significant change being tested and then committed to Git 3 2 Web Interface Customisation SAHARA provides a number of elements which can be placed within an HTML page to develop a customised web interface for a specific rig type This meant it was a relatively simple exercise to build up the page The majority of the development effort was in heli js which responds to user actions on the web page and invokes methods of the HeliController class The actions are sent to the appropriate server asynchronously in JSON JavaScript Object Notation format via an HTTP GE
7. it does not give students any debugging information in terms of program execution Secondly and perhaps of greater concern is that the onus is on the student to slow the speed of the helicopter or reset the microcontoller if their program is poorly functioning For example due to a poor PID control implementation the helicopter may run at 100 of its altitude range for an extended period of time This risks burning out the motor For this reason a number of extra features should be added in future design iterations One such feature would involve the Rig Client interpreting the analogue voltage coming from the helicopter stand which is linearly proportional to the helicopter s height If this is read in perhaps through an Arduino device with an analog to digital converter ADC the Rig Client could send a signal to a relay circuit to have the power to the helicopter cut and notify the student that their program needs improvement LI This could also be implemented with a programmable logic controller PLC A second feature being considered is to use the second serial port of the Stellaris device to send debug information back to the web interface in a text stream to aid students in the development of their programs 5 3 2 Server Configuration At present the web interface and scheduling server are hosted on an average desktop computer When the system is fully developed these services are likely to be moved to virtual machines VMs on the
8. presses 3 The ability to upload programs onto the microcontroller remotely 4 The ability to view the helicopter on a video stream 1 INTRODUCTION Nick Wareing 3 A remote lab implementation using SAHARA 5 The system must maintain robust behaviour at all times Throughout the remainder of this report italics will be used whenever we refer to elements of code we have written such as class method function or variable names 2 SAHARA 2 1 SAHARA Components A number of software tools have been created to assist with the development of remote laboratories UTS SAHARA MIT s iLab 6 and Lab2Go 7 are some promi nent examples The decision to use SAHARA was made in large part for non technical reasons Dr Steve Weddell has established a working relationship with the remote labs team at UTS and so it made sense to use their system Additionally it has all of the features required to support our desired remote helicopter laboratory SAHARA is a generic platform for designing customised remote labs It is devel oped and maintained by a team at UTS SAHARA consists of three separate but interconnected components 1 Web Interface 2 Scheduling Server 3 Rig Client The interactions between these components in the context of the our completed remote laboratory is detailed in the top section of Fig Web H o C IO Script Scheduling Server Software Figure 2 Interactions between various software and hardware
9. provides a short code extract to perform this GPIO interrupt initialisation With this done students can work on the rest of their program with no thought to its being used in a remote lab context The virtual buttons are mapped to GPIO inputs of the Stellaris development board as follows all pins are on Port B Button Pin Description Pad Select PB4 C0 1 Up PB5 C1 3 Down PB6 C0 4 Reset PB1 CCP2 18 The GPIO peripheral is initialised to interrupt on the falling edge of these pins with the code shown in Listing 2 Listing 2 Initialising the required GPIO pins void initialisePortB void GPIO PortB must be enabled for configuration and use SysCtlPeripheralEnable SYSCTL_PERIPH_GPIOB Set pins 5 amp 6 as input SW controlled GPIOPinTypeGPIOInput GPIOLPORTB_BASE GPIO_PIN_1 GPIO_PIN_4 GPIO_PIN_5 GPIO_PIN_6 Register the port level interrupt handler GP10PortIntRegister GPIOLPORTB_BASE portBIntHandler Make pins 5 amp 6 a both edges triggered interrupt GPIOIntTypeSet GPIOLPORTB_BASE GPIO_PIN_1 GPIO_PIN_4 GPIO_PIN_5 GPIO_PIN_6 GPIO_ FALLING_EDGE Set the interrupt priority to 0x40 13http docs oracle com javase 6 docs technotes guides jni 3 RIG CUSTOMISATION Nick Wareing 11 A remote lab implementation using SAHARA IntPrioritySet INT_GPIOB 0x40 Enable the pin interrupts GP1OPinIntEnable GPIOLPORTB_
10. 2013 Third Professional Year Project A remote lab implementation using SAHARA Nick Wareing Supervisors Steve Weddell and Phil Bones Electrical amp Computer Engineering University of Canterbury New Zealand September 2013 A remote lab implementation using SAHARA Abstract A remote laboratory system has been designed to allow students to test micro controller code on model helicopters and view its performance without physically being in a laboratory They access a web based system running open source SA HARA software and are able to remotely upload a compiled program onto a Stellaris LM35S1968 microcontroller Students view the helicopter on a live video feed and have virtual button presses sent to pre defined pins of the microcontroller for their program to respond to Remote resetting of the microcontroller is also supported An embedded helicopter control program has also been written for demonstration purposes Two helicopters are currently accessible remotely and the software is de signed to scale easily The system has proven robust over hours of testing It costs 1210 10 to setup each helicopter laboratory A remote lab implementation using SAHARA 1 INTRODUCTION This report describes the design and implementation of a remote laboratory system for the University of Canterbury The laboratory allows Electrical Engineering stu dents to upload compiled C code and use it to control an electric helicopter They are
11. BASE GPIO_PIN_1 GPIO_PIN_4 GPIO_PIN_5 GPIO_PIN_6 IntEnable INT_GPIOB Note INT_GPIOB defined in inc hw_ints h Students are also told that in order to control the helicopter they must configure the ADC and PWM peripherals as follows e The helicopter s altitude reading is connected to ADCO of the Stellaris board e The helicopter s main rotor is connected to PWM1 of the Stellaris board To give students confidence in the remote lab system and to allow us to perform tests during its development a demonstration helicopter control program has been written Students do not have access to the source code of this program but are able to press the Program Demo button on the web interface at any time to have the binary loaded onto the Stellaris board The demonstration program was designed to meet all of the specifications re quired in the student s assignment A real time operating system FreeRTOQ was used to break the code into a number of tasks as shown in Fig 7 Communication between tasks is by way of queues and semaphores ADC Peripheral Get Altitude from ADC Figure 7 The helicopter control program was broken down into a number of FreeR TOS tasks 3 6 Video Feedback One important point to note is that the video streaming and Rig Client have no connection with each other One must simply ensure that the correct video formats are being continuously streamed using any suitable software
12. T This means that there are no page reloads the web site behaves as though it were a desktop application The completed web interface as show in Fig 4 includes a connection to the video stream along with buttons to perform upload of binaries and to control the microcontroller GPIO lines 3 3 Virtual Buttons The next step was to investigate how GPIO signals would be sent to the Stellaris board An FTDI FT245R USB to Parallel FIFO chip was chosen for this purpose Thttp git scm com Shttp www ftdichip com Products ICs FT245R htm 3 RIG CUSTOMISATION Nick Wareing 7 A remote lab implementation using SAHARA UC SAHARA Labs CANTERBURY Session Session Time Heli 2 In Session 00 00 39 Finish Session xi Remaining 8 Heli Camera x Turn Off 00 29 21 5 i Video Formats Q Logout Heli Camera Program Motion JPEG ao Down Help Operations List Program e Up button pressed Demo e Up button pressed Select e Up button pressed Cones Up button pressed Hard Reset Support e Up button pressed Select button pressed Soft Reset Select button pressed Finished loading Figure 4 The web interface in action The buttons of the left of the video stream allow program binaries to be uploaded and allow users to reset the microcontroller via JTAG The buttons immediately right of the video send signals to allocated GPIO lines of the microcontroller
13. We chose to use the Logitech C920 Webcam for video capture and fimpeg as our streaming and transcoding solution ffmpeg streaming can be initiated from the command line For example the following invocation Listing 3 starts streaming in the formats described by ffserver conf 4http www freertos org http www ffmpeg org 3 RIG CUSTOMISATION Nick Wareing 12 A remote lab implementation using SAHARA Listing 3 Initialising the virtual button pins 1 ffserver f ffserver conf amp ffmpeg v quiet r 5 s 320x240 f video4linux2 i dev videoO http localhost 7070 feed1 ffm 2 4 SYSTEM SUMMARY AND BUDGET 4 1 Summary of Software The following software is used in the system In order to reduce source software was chosen cost only open Software Use License SAHARA Remote Labs Framework BSD Ubuntu Server Operating System GNU GPL Java JDK 6 Java Virtual Machine and Compiler GNU GPL Apache Web Server Apache License MySQL Scheduling Server Database GNU GPL PHP PHP Interpreter PHP License libftdi FTDI USB driver with bitbang mode LGPL OpenOCD In system programming for Stellaris device GNU GPL ffmpeg Video transcoding and streaming of helicopter GNU GPL Python Interaction with OpenOCD telnet daemon Python License FreeRTOS Real time operating system for demo GNU GPL 4 2 Summary of Hardware per rig The hardware costings are listed belo
14. cant customi sation are the Web Interface and Rig Client The procedure for deploying changes to each component are different Changes to the web interface simply require the affected files to be copied to the correct directory on the server Users then see the new changes when the page is next loaded or refreshed Each change to the Rig Client requires the Java class to be recompiled using an Ant build script similar to make In order to deploy this class the Rig Client service must be stopped and then started again when the new class is copied across If done manually this deployment is a tedious process and takes time away from doing real development work To make better use of my time I wrote a deployment script in Python using the Fabric library Fabri is designed to help streamline deployment and system administration tasks over SSH In the later stages of the project when extra servers were provisioned to host extra Rig Clients so that multiple helicopters could be in use it was a simple matter of adding their host names to this script 5http www ubuntu com http docs fabfile org en 1 7 2 SAHARA Nick Wareing 6 A remote lab implementation using SAHARA Git has been used for version control throughout the project The repository is hosted on the department s GitLab sever at https eng git canterbury ac nz david vanleeuwen labshare 3 RIG CUSTOMISATION 3 1 Rig Client Class The Rig Client is coded
15. d quickly We have tested the rig hosted at the University of Canterbury in Christchurch New Zealand from Canberra Australia and have found the delay in the video to be acceptable at approximately one second The software has been developed to achieve graceful failure wherever possible In most cases if an error is encountered such as the USB to parallel chip being disconnected an informative error message will be written to a log file the user logged out of the system and the rig automatically placed in an offline state until a technician resolves the problem Staff are notified of problems automatically via email The system is highly scalable To add a new rig helicopter to the remote laboratory a new computer is provisioned and the SAHARA software installed With a webcam USB to parallel chip and Stellaris microcontroller connected all that remains is for the IP address of the scheduling server to be specified in the new rig s configuration file Registration then occurs automatically A guide to aid technical staff in this process has been written and can be found in Appendix A 5 2 Security Allowing students to upload executable programs to university servers is an in herently security sensitive operation The target audience of this facility are pre dominantly young electrical engineering and computer science students the type of individuals who like to push the bounds of whatever system they are using From a network and co
16. department at the University of Canterbury offered a course ENCE36 I entitled Embedded Systems One of the projects Fun with Avionics required students to write an embedded program to control the flight of a small model helicopter The helicopter was fixed on a custom built stand which allowed it to rise fall and turn through a range of motion see Fig fi Students purchased a Stellaris development board with a Cortex M3 micro controller which included a development platform for compilation programming and debugging The helicopter stand output a voltage proportional to the height of the helicopter Students were required to control the rotor using pulse width modulation PWM signals This assignment has proved to be both challenging and interesting for students It provides a platform to apply embedded programming concepts such as interrupts implementing proportional integral derivative PID control and creating a small real time operation system RTOS Due to a limited number of helicopters and associated challenges however all students were not able to gain equal access to the laboratory equipment The remainder of this report discusses how the Fun with Avionics assignment has been converted to a remote laboratory format to help solve some of these issues The SAHARA Labs software framework developed at UTS was chosen for the project Our configuration of SAHARA is described in the following section http w
17. ed in var WI application configs Contains the settings for LDAP database email and institution customisation 6 2 Scheduling Server schdeulingserver properties Located in usr lib schedulingserver conf 6 3 Rig Client rigclient properties Located in usr lib rigclient conf Contains parameters to uniquely identify a rig and specify its type rigattributes properties Located in usr lib rigcleint conf conf d Contains settings for the video feed including formats size port and the number of cameras batch properties Located in usr lib rigcleint conf conf d Contains settings for the temporary storage of uploaded program binaries heli properties Located in usr lib rigcleint conf conf d Specifies the location of the various exter nal scripts and example program binaries 7 FAQ amp Troubleshooting In almost every case the most useful debugging resource I found was the log files
18. eset button triggered by one of the virtual inputs discussed above relies on the user s program to interrupt on this signal and perform a software reset The hard reset button on the other hand causes the OpenOCD daemon to send a reset command via JTAG and so will work regardless of the program loaded on the Stellaris device The Python script in Listing I shows how the hard reset functionality is imple mented The script is called from the Java program as shown in Fig 6 It can be easily adapted in the future to send any other OpenOCD arguments Rig Client Heli Hard Reset Button Controller pressed jtagCommandAction method invoked Telnet session to heli_jtag py called with OpenOCD daemon reset passed as an started argument programmatically and reset executed Figure 6 Block diagram of a hard reset execution The button calls the jtag CommandAction method in the customised Rig Client This method then invokes a Python script which executes the command inside an OpenOCD telnet session 3 RIG CUSTOMISATION Nick Wareing 9 BR oO N H A remote lab implementation using SAHARA Listing 1 Python script to send OpenOCD commands import pexpect import argparse import os import sys def main kwargs jtag_command kwargs command def jtag command command child pexpect spawn telnet localhost 4444 child sendline command child expect gt child sendline exit
19. l online laboratories in Education Engineering EDUCON 2010 IEEE 2010 Sahara Development Handbook Version 1 0 2012 Future Technology Devices Interntional Ltd FT245R USB FIFO IC datasheet version 2 12 2010 Online Available http www ftdichip com Products ICs FT245R htm A Cardoso M Vieira and P Gil A remote and virtual lab with experiments for secondary education engineering and lifelong learning courses Interna tional Journal of Online Engineering iJOE vol 8 no S2 pp 49 54 2012 D A Samuelsen and O H Graven Assessment of the quality of low cost data acquisition equipment for remote lab setups in Remote Engineering and Virtual Instrumentation REV 2013 10th International Conference on IEEE 2013 V Lasky Implementing resilient remote laboratories with server virtualiza tion and live migration in Remote Engineering and Virtual Instrumentation REV 2018 10th International Conference on IEEE 2013 N Wareing S Weddell and P Bones A remote lab implementation using SAHARA ENZCON Proceedings pp 58 63 2013 REFERENCES Nick Wareing 17 APPENDIX A Fun with Avionics Heli Rig Technician Guide August 2013 1 Prerequisites e Ubuntu installed e Scheduling Server installed on another machine e Stellaris board Logitech webcam and FTDI device all connected via USB e SSH Screen and Vim installed 2 Acquiring the SAHARA Binaries Down
20. ler and flash the bin file to the microcontroller Additionally the Python argparse library is used to process the command line arguments sent from the Java Rig Client instance The script has been successfully verified and tested in isolation 1http openocd sourceforge net 2http www noah org python pexpect 3 RIG CUSTOMISATION Nick Wareing 10 A remote lab implementation using SAHARA 3 5 Prototype Stellaris Program We now turn our discussion to the embedded C program students must write to control the helicopter Recall that button presses on the web interface result in an asynchronous function call to the Heli Rig class The Java function checks the argument passed to it is a valid integer and then calls a C function via the Java Native Interface JNIF The JNI allows Java code running in the Java Virutal Machine JVM to call and be called by native applications written in other languages We use the JNI here because the FTDI board is controlled with a C library The C code we have written performs a number of checks to see that the FTDI board exists and is connected to the server if it is not the rig is taken offline It then pulls a corresponding pin low for a predefined period of 200ms The upshot of this design from a user s perspective is that their program must be configured to interrupt on the falling edge of the attached GPIO pins This information is provided in a user s manual This document also
21. load the RigClient and RigClient Commons RPMs from http sourceforge net projects labshare sahara files Installers r3 2 3 Installing the Rig Client and Libraries telnet ienabler canterbury ac nz 259 sudo apt get update sudo apt get install openjdk 6 jre openjdk 7 jre alien openocd vim libftdi dev git yasm sudo alien i RigClient 3 2 0 x86_64 rpm sudo alien i RigClient Commons 3 2 0 x86_64 rpm 3 1 Configuring the Rig Client The easiest way to do this is to copy the configuration files and HeliRig class from an existing rig client The only thing that needs to change is to increment the number of the Rig Name parameter and specify the address of the scheduling server both in rigclient properties The temporary directories for the batch operation also need to be created as follows sudo mkdir var tmp rigclient sudo mkdir var cache rigclient 4 Installing ffmpeg sudo git clone git source ffmpeg org ffmpeg git cd ffmpeg sudo configure sudo make sudo make install usermod a G video nmw50 Replace nmw50 with your username 5 Starting everything up The following assumes the OpenOCD and ffmpeg config scripts are located in your home directory sudo openocd Ctrl z bg ffserver f etc ff conf amp ffmpeg v quiet r 5 s 320x240 f video4linux2 i dev videoO http localhost webcam ffm Ctrl z bg 6 Location of Config Files 6 1 Web Interface config ini Locat
22. mputer security standpoint this means that the software should be carefully designed to be resistant to exploits and that the user s actions should be tightly controlled Our design puts security at the forefront by choosing a SAHARA primitive controller This means that students access the remote laboratory only through a web interface and it does not expose a Remote Desktop Connection as a number of existing systems have done Only port 80 is exposed which greatly reduces the vulnerability of the server as there is no way for the end user to open a command shell Another major concern is that of running student s code on the microcontroller without performing any sort of verification on it other than checking that the file extension is that of a valid binary file For the most part this should not be a problem as causing a chip to stop working would be a detriment to the student and his classmates However if the system were to be expanded to a wider user base a new system might be put in place where it is the source code that is sent to the 5 DISCUSSION Nick Wareing 14 A remote lab implementation using SAHARA rig server which then runs some sanity checks on its contents before compiling it for the microcontroller 5 3 Future Plans 5 3 1 Debugging Features At the present point in time the only feedback to the student in regards to the performance of their program is the video stream This has a number of issues IO Firstly
23. plementation and are excited about the experience it will provide to future students 6 CONCLUSION Nick Wareing 16 A remote lab implementation using SAHARA References 1 6 7 10 11 12 13 D Ursutiu C Samoila and M Dabacan Cross platform methods in digital electronics engineering education in Remote Engineering and Virtual Instru mentation REV 2013 10th International Conference on 2013 C F Riman A El Hajj and I Mougharbel A remote lab experiments im proved model International Journal of Online Engineering iJOE vol 7 no 1 pp 37 89 2011 K Jona R Roque J Skolnik D Uttal and D Rapp Are remote labs worth the cost insights from a study of student perceptions of remote labs Inter national Journal of Online Engineering iJOE vol 7 no 2 pp 48 53 2011 B Aktan C Bohus L Crowl and M Shor Distance learning applied to control engineering laboratories Education IEEE Transactions on vol 39 no 3 pp 320 326 1996 P Ordu a L Rodriguez Gil D L pez de Ipi a and J Garcia Zubia Sharing remote labs A case study International Journal of Online Engineering vol 9 pp 26 27 2013 M I of Technology ilabs Internet access to real labs 2009 Online Available http icampus mit edu projects ilabs D Zutin M Auer C Maier and M Niederstatter Lab2go A repository to locate educationa
24. s controlled directly by the Rig Client Of these options batch control is obviously not suitable because further interaction is required after program upload to control and monitor the helicopter A remote desktop connection is an example of peripheral control In this case the Rig Client has no direct control over the hardware and is only responsible for assigning users running tests and detecting rig activity The helicopter laboratory could be developed in this way by simply installing the Code Composer Integrated Development Environment IDE on the remote server and allowing students to develop their code on the server A desktop program could be written to change the state of the various GPIO lines of the microcontroller via a USB device The peripheral control approach is problematic however Writing code is a time intensive process so having this done on the remote laboratory side would compro mise the system s ability to share access around Moreover students would likely be unreceptive to being logged out when in the middle of writing a complex function Security is also compromised by giving students remote desktop access The final option is primitive control This is typically implemented within the web interface Actions are routed through to methods of the customised Rig Client class as shown in Fig 3 Primitive control also provides users with a more elegant and streamlined experience Security is enhanced because access is onl
25. w It can be seen that the cost scales linearly with the number of rigs provisioned Item Supplier Price NZD Model Helicopters Acorn Models 250 00 Logitech C920 Webcam Ascent 124 32 Stellaris EKS LM3S19 Element 14 103 83 FTDI UM245R Board Element 14 31 95 10A Bench Power Supply UC ECE 200 2x Headless Computers UC ECE 500 Total 1210 10 Total for 2 rigs 2220 20 5 DISCUSSION 5 1 Performance The system as it stands meets or exceeds all of the requirements specified Testing has shown the system to be robust with the helicopters having been flown remotely for many hours Although not the immediate focus of this project a number of 5 DISCUSSION Nick Wareing 13 A remote lab implementation using SAHARA mechanical changes have been made to the helicopter stands to further enhance reliability 1 Springs were added to prevent the helicopter being damaged when the mo tors are stopped mid flight These have performed well and greatly enhance robustness 2 The power cables for the main rotor are now routed down the shaft of the stand rather than hanging freely from the helicopter This prevents them from wrapping around the helicopter or being caught in the blades Latency in the video feed is one issue that had the potential to cause problems with this project because it is important that students are able to press a button and see the helicopter respon
26. ww uts edu au http www canterbury ac nz courses 3http sourceforge net projects labshare sahara 1 INTRODUCTION Nick Wareing 2 A remote lab implementation using SAHARA Figure 1 The helicopter is fixed in a stand which allows a range of motion The stand has an optical sensor to detect the height of the helicopter The various design decisions required for the lower level components of the rig are explained next We then present our example helicopter control program Finally the current state of the system is described in detail and future plans are presented The appendices contain a guide to aid technicians in adding additional rig clients Before we delve into the technical detail we will define a number of terms specific to remote laboratories that will be used throughout the paper SAHARA An open source framework for developing generic remote laboratories Rig Client The SAHARA software application that provides an abstraction to rigs Heli Rig The customised version of the Rig Client providing functions to commu nicate with the helicopter microcontroller and associated hardware Rig A single instance of a laboratory referring to both the hardware and software In this case one rig refers to one helicopter For this project to deliver the required experience to students and be successful the following must be achieved 1 Two functioning helicopter rigs 2 The ability to respond to virtual button
27. y through the web browser The compromise is that additional development time is required On the balance of these reasons primitive control was chosen http framework zend com 2 SAHARA Nick Wareing 5 A remote lab implementation using SAHARA Sahara Native Controls Library Rig Client Figure 3 Block level diagram of primitive control 8 2 2 SAHARA Installation The following steps were taken to install the three components of SAHARA Firstly a standard desktop machine 4GB RAM was provisioned with the Ubuntu oper ating system In order to install SAHARA the following prerequisites were installed e Java 6 openjdk 6 jdk e Alien to allow the installation of SAHARA RPM packages designed for Red Hat Linux on Ubuntu e LAMP a commonly installed stack of web sever technologies the acronym expands to Linux Apache MySQL and PHP Ubuntu makes this install straightforward using the tasksel and lamp server packages The Rig Client Rig Client Commons a further set of optional abstractions and Scheduling Server packages were then installed using Alien Finally the Web Inter face files were copied to the root of the Apache document folder 2 2 1 Deployment We quickly determined that a quick code to test cycle was going to be crucial to both the project s success and to providing an enjoyable and efficient development experience The two SAHARA components that would require signifi
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