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1. Once the key_teleop script is executed we can modify the velocity of the vehicle using the keys W and S change the direction of the vehicle using A and D change the angle of the laser using and K change the position of the bucket using U and J moving up and down the mechanical arm using O and L change between the different models of piles using the keys 1 2 and 3 and stop the program using C aS LLL cp vy jon ke USER MANUAL Wheel Loader Simulator You can also visualize the vehicle in Rviz typing 5 e oua aa USER MANUAL Wheel Loader Simulator 2 9 Pa P4 J DATA Fa ALATIN CO 11323110 ATHY Je pe A a l I L i J I L J V Y 1 i L e Iw i 4 ii i Ul 4 a L 1 X J L C The path following simulation consists on a simulation of the L120F Volvo Wheel Loader on a flat ground map The waypoints of the path loaded by default on the simulator are marked by construction cones with disabled collisions To load the scenario type ores exor Sensi 55 To load the controller type e Lai Lennie i n You can now execute the path following mechanism typing S oath se cle me You can also visualize the vehicle in Rviz typing Z moe desto well II Abie eo Sexe vato a LIE Ine2. using models of actual work sites The simulator also will make it possible to evaluate algorithms for task and path planning in a much more efficient way than would be possible otherwise Summary Autonomous Long Term Load Haul Dump Operations ALLO is a joint project by the MR amp O Lab Volvo Construction Equipment and NCC Roads The goal of the ALLO project is to find a solution to the demand for efficient material transport 1n many industrial environments The employment of autonomous mobile robots in the cycle of material handling including loading and unload the material is a solution which has a great potential to offer improvements in terms of safety cost efficiency reliability and availability This project consists on the analysis and porting of an old wheel loader simulator with the Player Stage framework from the ALLO Project to a modern robotic framework like Robot Operating System ROS and Gazebo The new simulator is able to reproduce a realistic scenario as well as simulate a LI20F Volvo wheel loader model The developed software also provides the mechanism to drive the wheel loader through the reproduced terrain to control the movement of the different articulated joints of the robot to receive information of the environment through different sensors and to provide of a waypoint routes to the robot The simulator makes it possible to generate realistic data for mapping localisation and obstacle detection using mode
3. We 77 EN Updated Jul 30 2013 Figure 3 2 4 Data flow of ros control and Gazebo http wiki ros org ros_ control 13 26 Position PI Controller v 4 Controllers x L Effort Without Controller Controller Articulated Joints Legend Figure 3 2 5 L120F model structure 3 2 Implementation of the 3D Map For the implementation of the 3D Map it has been received from the ALLO project the following files e Two 32bits RGB PNG 1000x1000 pixel heightmaps Figure 3 2 1 a b e APLY mesh with 411958 vertices and 661609 faces Figure 3 2 2 It has been started trying to implement the heightmap system because the triangle mesh that was received from the ALLO Project is too huge to have a good performance with it a heightmap is much softer and more efficient A heightmap can also represent the surface elevation data of the ground where the asphalt plant is in Eskilstuna Kjula Figure 3 2 1 a b for its representation on the Gazebo environment To do it first it has been adapted the heightmap to the Gazebo 1 9 requisites e A 8bits square greyscale image e Each side must be 24n 1 pixels The PNG file has been resized to a 513 x 513 pixels image as we can see in the Figure 3 2 1 c using Photoshop It has been also generated a normal map as we can see in the Figure 3 2 1 d using the NVIDIA Texture Tools for Adobe Photoshop PEL However the wheel loader model doesn t behaviour corre
4. e Extend the path following mechanism o Read the path format from the ALLO Project e Change the usage of the standards libraries plugins and messages for its own more adapted to the needs of the project 21 26 1 2 5 4 5 6 7 5 References Magnusson Martin Cirillo Marcello Kucner Tomasz Automomous Long Term Load Haul Dump Operations Project Accessed 16 of June 2014 URL http aass oru se Research mro allo Koenig Nathan amp Howard Andrew Gazebo 3D Multiple Robot Simulator with Dynamics Accessed 16 of June 2014 URL https www gazebosim org Hedges Reed Stoy Kasper Bers Josh Douglas Jason K Jinsuck Kim Martignoni III Andy Melchior Nik stergaard Esben Sweeney John Batalin Maxim Burns Brendan Douglas Jason K Dahl Torbjgrn Fredslund Jakob Jung Boyoon Dandavate Gautam University of Melbourne RoboCup Team Player Project Accessed 16 of June 2014 URL http playerstage sourceforge net Gerkey Brian Vaughan Richard Howard Andrew The player stage project Tools for multi robot and distributed sensor systems Proceedings of the 11th international conference on advanced robotics 2003 ICAR 2003 pp 317 323 Coimbra Portugal Accessed 16 of June 2014 URL http robotics usc edu gerkey research final papers 1car03 player pdf Koenig Nathan amp Howard Andrew Design and Use Paradigms for Gazebo an Open Source Mult
5. 26 3 Implementation 3 1 Implementation of the wheel loader and sensors 3 1 1 Model structure and measurements The first step to implement a realistic simulation of a Wheel Loader in gazebo 15 to build the 3D model of the wheel loader machine The 3D model of the previous implementation of the wheel loader from the ALLO Project is not compatible with our version of Gazebo However it has been able to reuse some information of the previous model like the hierarchy of the Joints of each part of the body of the model and estimate the dimension of these parts Two different approaches were considered for the building of the new L120F model try to use all the possible information about the old model and follow it structure or build a completely new one model In order to reuse as much software and data from the Player Stage simulator It has been made the design choice of adapting the previous model to the new URDF format The creation of a completely new model would be better in terms of accuracy but it has been considered it not a priority leaving this option to a future development of the project Respect to the dimensions of the resulting model it has been approached to the dimensions of the Volvo s L120F technical specifications and the dimensions of the model of the previous simulator Like in the old code it have been used the basic geometric shapes which Gazebo uses to build the model The wheels are represented by cylinders and th
6. sudo sh a Techo deb m packages orae c raring main i ccc Ade sources lot dros latei bui st 3 Setup your keys S wget http packagss sudo apt key 4 First make sure your Debian package index is up to date 5 sudo apt get update 5 Install the ROS Desktop Full version that includes Gazebo s sudo apk get inseall ros ii GliaO desktop 6 Before you can use ROS you will need to initialize rosdep rosdep enables you to easily install system dependencies for source you want to compile and is required to run some core components in ROS S sudo anit S rosdep update 7 It s convenient if the ROS environment variables are automatically added to your bash session every time a new shell is launched S echo Source eis nos derselbe I5 S eim e If you have more than one ROS distribution installed bashrc must only source the setup bash for the version you are currently using If you just want to change the environment of your current shell you can type Source AD AS S659 Setup bash SE USER MANUAL Wheel Loader Simulator 8 Rosinstall is a frequently used command line tool in ROS that is distributed separately It enables you to easily download many source trees for ROS packages with one command suene tots je clave IE UL 9 The ros hydro full desktop version should have the gazebo ros pk
7. June 2014 URL https developer nvidia com nvidia texture tools adobe photosho 21 Marder Eppstein Eitan 2D navigation stack Accessed 16 of June 2014 URL http wiki ros org navigation 22 Chitta Sachin Motion planners stack Accessed 16 of June 2014 URL http wiki ros org motion planners 23 Institute of Electrical and Electronics Engineers EEE Xplore Digital Library Accessed 16 of June 2014 URL http ieeexplore ieee org 23 26 24 Google Google Scholar Accessed 16 of June 2014 URL http scholar google com 24 26 URDF hierarchy 651 SOLS I 6STvT Ads 6STPTE SOLS I 6STHTE AC 651 8OLS I 6STPT Ads 0 O T 2ZAx 0 0 T z x L 0 0 T z x uoisuadsnsjeaJ juiofuoisusdsns 0 0 0 Adi L O 0 0 z x rebuipppng 0 0 0 Ads 05 0 2Ax eost anav a6uiyjecy mesy iu 95 99 1 11 5 9 1 0 4 9 ebuipyuriav 6STPTE 80 8 T 6STbT Ads 00 0 Adi L 0 0 ET ZAX 0 T 0 zAx 10fsd6 C uiotioass 7 Cuotas gt gt jurof3ubre Mue3unoo uetus gt qujofasequige gt 0 0 0 Adi 0 0 0 Adu TOZ SLO 0 z X 5 SZ T 0 z x 0 0 0 Adu 0 S Z Q z x 0 0 0 Adi 00 0 z X 80451 0 0 4 1 ST SZO T 0 z Ax 80458 1 0 0 Ads SO Z T 0 poq jase uiqe 25 26 Wheel Loader Simulator User Manual 26 26 Orebro Universitet User Manual Wheel Loa
8. Simulator 4 3 SickLMS200 Configuration Inside the 1120f gazebo file you can change the laser configuration and adjust the parameters of the SicKLMS200 laser scanner By default are lt ray gt secum IUOS al Sig IE de lt samples gt 181 lt samples gt lt rosolucion On suave Leo dei angle 50 0 3 max angle Lo lt q See gt lt range gt ile LY lt 7 am lt resolution gt 0 01 lt resolution gt lt range gt lace You can consult more information about the 1 4 SDF laser format here
9. arm structure The wheel loader XML model of the player stage simulator uses joint loops for the representation of the mechanical arm of the Volvo L120F vehicle A way to solve this problem is the use of SDF models and assigning pose in joint loops to create parallel mechanisms however it have been opted for simplifying the model removing the joint loops and let the task of developing a more realistic model to a future 8 26 Another difference with the specification of the old L120F model and the new one is the fact that the older specify the position of all the pieces of the model in their body s tags The equivalent of that in our model are the link s tags but we cannot define the position of each piece there because two reasons the main reason 1s for modelling the articulated joints we need to compute the difference between the position of the articulated joint and the geometric centre of the link The other reason 15 related to the fixed joints we need to define the location in the joints tags because if not the centre of mass of each piece will be in the origin instead on the centre of each piece A graphic representing the resulting URDF hierarchy can be seen in Appendix A The units of measure of the old model are also different to the URDF standard for example the angles in the old model are represented 1n degrees and we are representing it in radians to follow the URDF standard Another measure is the mass Gazebo 1 9 doesn
10. eal 4 5 TE Stan queda l USER MANUAL Wheel Loader Simulator 4 Technical details 4 1 ROS Gazebo communication For the communication between gazebo and ROS some topics have been created Is able to subscribe to its topics or publish information on them Topic Message 120f leftRearWheelHinge_effort_controller command std_msgs Float64 1120f rightRearWheelHinge_effort_controller command std_msgs Float64 120f leftFrontWheelHinge_effort_controller command std_msgs Float64 1120f rightFrontWheelHinge_effort_controller command std_msgs Float64 120f steerJoint_position_controller command std_msgs Float64 120f cabinLaserJoint_position_controller command std_msgs Float64 120f ADLinkHinge position controller lcommand std msgs Float64 120f BuckHinge position controller lcommand std msgs Float64 120f camerat image raw sensor msgs Image 1120f camera1 camera info sensor msgs Cameralnfo 1120f laser scan sensor msgs LaserScan 1120f odometry data sensor msgs Odometry 4 2 Path description file format The format to the input path files should be like Waypoints number Front Angle 1 Pitch Angle 1 Effort 1 Front Angle 2 Pitch Angle 2 Effort 2 Example path1 dat 5 SUME ecco Mr c 2 Qe gd c Ue Ho Note that a positive effort means backward movement and a negative effort forward movement 200 USER MANUAL Wheel Loader
11. the cycle of material handling including loading and unload the material 1s a solution which has a great potential to offer improvements in terms of safety cost efficiency reliability and availability A previous approach on this project was the development of a wheel loader simulator using Gazebo with the Player Stage framework The simulator was used both for algorithm testing and for preparing demos without running the real wheel loader But the code of the ALLO project was migrated to the ROS framework rather than player stage with the Hydro version of ROS a simulator can be develop using the version 1 9 of Gazebo rather than the 0 8 version that used the previous ALLO s simulator 1 3 Project The first task of the project has been the analysis the previous simulator written in Player Stage and the research of the different ways to improve it including what robotic framework could be better to our proj ect The next task have been to port what is there from Player Stage to the chosen framework resulting in a simulator that can be used to visualize the wheel loader in its environment and to collect simulated laser and position data 4 26 1 4 Requirements The requirements have divided in three steps the first one had high priority and the rest were optional In each one the simulator had the following capabilities e Step I high priority o Gazebo simulator o Ability to use 3D maps of work site Kjula o Ability
12. to drive articulated wheel loader model interactively o Simulated sensors laser scanners odometry GPS IMU e Step II optional o Ability to replace part of the 3D map for when the piles change after a bucket fill o Ability to follow a given path given as a list of waypoints with a given speed some variance e Step III optional o Asphalt plant model that is maintaining a representation of the gravel level in bins and emptying rates for a given recipe some variance in levels and emptying rates o An interface for getting and setting parameters for the simulation from the outside developed in dialogue with the ALLO project All the goals have been fulfilled with the exception of given a speed in the path following goal and the implementation of the asphalt plant model 1 5 Outline The structure of the remainder of the document is as follows Section 2 describes the tools and basic setup that has been used Section 3 contains much of the core of the work as it details the implementation of the simulator s components Section 4 details the results of the project and Section 5 discuss the reached competences during the course of the project 5 26 2 Methods and tools 2 1 Methods During the project have been used an incremental development model with some iterative elements An initial set of requirements have been established at the beginning of the project and it has been redefined during the course of the pr
13. Computer Science Degree Project Advanced Course 15 Credits AUTONOMOUS WHEEL LOADER SIMULATOR Samuel Navas Medrano Computer Engineering Programme 180 Credits Orebro Sweden Spring 2014 Examiner Franziska Kl gl rebro universitet Institutionen f r naturvetenskap och teknik e 701 82 rebro 5 Orebro University LJ School of Science and Technology amp SE 701 82 Orebro Sweden e UNINSS Abstract The use of simulators when developing robotic systems provides the advantages of the efficient development and testing of robotics applications saving time and resources and making easier publics demonstrations This thesis project consists on the simulation of a wheel loader at an industrial environment in the cycle of material handling This report describes the development of a physics based simulator using the Robot Operating System ROS and Gazebo frameworks The resulting simulator allows reproducing the 3D map of the work site as well as the robotic wheel loader and simulating it in a realistic way The developed software also provides the mechanism to drive the wheel loader through the reproduced terrain to control the movement of the different articulated joints of the robot to receive information of the environment through different sensors and to provide of a waypoint routes to the robot The simulator makes it possible to generate realistic data for mapping localisation and obstacle detection
14. The full desktop package of ROS hydro also includes the stand alone version of Gazebo 1 9 and the libraries for the ROS Gazebo communication There 1s also a newer version of Gazebo 2 0 but the newer version is not compatible with ROS Hydro Medusa To work properly with a 3D environment simulator like Gazebo we should work with a dedicated graphic card The computer we have used to the development of the project has the technology NVIDIA Optimus This is not supported out of the box by Ubuntu 13 04 Some hybrid graphics laptops still allow you to choose using only the nVidia card in BIOS but most modern Optimus laptops don t have this option It is possible to solve this issue with the installation of the Bumblebee Project It is a set of tools developed by people aiming to provide Optimus support under Linux Bumblebee doesn t have a release for Ubuntu 13 04 in their official repository the only way to use it is installing the version of Bumblebee to Ubuntu 12 10 Due to this lack it is necessary to modify the manual configuration of the Bumblebee files and indicate to it to use specifically the PCI Bus ID of our NVIDIA GPU 2 3 Other resources All the needed data 3D maps of the terrain the Volvo s L120F wheel loader 3D model the code of the old simulator external algorithms path planning task scheduling and gravel simulation path data and all required information related to the project have been supplied by the ALLO Project 7
15. anning monitoring and implementation between the whole project periods as it can be seen in the schedule of the specification of the project e Write emails and plan weekly meetings with the staff from the ALLO Project 20 26 5 1 3 Values and attitude During the project it has been acquired the following values e Have the ability to stay informed about current knowledge research development and working methods used in the field as it can be seen during the course of the project in the report in the results and in the references of the report e Have a professional approach in their relationships with the ALLO Project It has been doing regular meetings during the project maintained active communication by email with members of the ALLO Project and receiving feedback from them about the result of the project and the changes in the requisites e Have a professional approach to the end product of the project The resulting software of the project has been developed making particular emphasis on the reliability usability extensibility documentation and the reutilization of the software 5 2 Compliance with the project requirements The high priority Step I of the project consisting on the installing and configuration of the Gazebo ROS environment the recreation of the Kjula map into the simulator and the ability of drive the wheel loader through the terrain have been completed in their majority Also the optional Step II consisting on th
16. communication works using topics different modules of our software publish information about the robot in these topics and some modules subscribe the information in these topics It has been used the JointStateInterface to allow ROS read information about the robot joints in Gazebo The EffortJointInterface allows ROS to send to Gazebo how the robot has to behave wheels mechanical arm etc It would be better to use a VelocityJointInterface to manage the rotation velocity of the wheel joints of the robot but that interface 1s not fully implemented in Gazebo 1 9 The problem using a force control instead a velocity control 1s that 1s hard to maintain a reasonable speed on bumpy ground like the ground of the Eskilstuna terrain in the simulation The EffortJointInterface offer to us different kind of controllers to change the parameters of the joints of the robot It can be seen a list of all the available controllers of Gazebo at the Figure 3 2 4 I have used the JointPossitionController to change the position of the articulated Joints like the direction joint between the rear frame and the front frame and also for the articulated joints of the mechanical arm and the bucket of the L120F wheel loader About the control of the rear wheels 1t has been tested the diff drive controller DiffDriveController velocity controllers JointVelocityController effort controllers Joint VelocityController and the effort controllers JointEffortControlle
17. criber program will check if the vehicle is in the x and y coordinates of the corresponded waypoint and if it fits with a determined offset margin it will publish the new position of the direction Joint to the wheel loader then it will start to turn and when it reach the corresponding pitch angle also with an offset margin the C program will publish a message to the direction joint of 0 radians and then the vehicle will stop turning At the end we have a C program that is ROS subscriber and publisher at the same time which receives the odomertry information of the L120F wheel loader vehicle and sent to them the changes of the direction of it movement to reach the waypoints of the path AH Figure 3 2 1 a grid overlayed heightmap Figure 3 2 1 b heightmap 16 26 Figure 3 2 1 c adapted heightmap to Gazebo Figure 3 2 1 d generated normal map Figure 3 3 1 a Kjula simplified triangle mesh Figure 3 3 1 b scan data from a real gravel pile 17 26 Figure 3 3 1 c the same pile after having Figure 3 3 1 d the same pile after having simulated the removal of 5 buckets of gravel simulated the removal of 49 buckets of gravel distance front x front y front waist rear x rear y rear waist angle angle angle angle speed 0 105 0 105 0 012 0 207 3 064 0 291 0 195 0 118 NEUTEE ES AT TI OT TT ICT Figure 3 4 1 ALLO Project path description rear x rear y front pitch wheels angle angle
18. ctly when it 15 tried to drive thought the generated terrain and in addition the latest versions of Gazebo including the 1 9 version has several bugs in the uses of the heightmaps related to the physics collisions and textures of the heightmap s terrain As result we had contemplate to implement the terrain map with a triangle mesh It has been received from the ALLO Project another 3D mesh in COLLADA format which is just a simplified fragment of the original previously mentioned Kjula 3D map with only 24912 vertices and 49999 faces Figure 3 3 2 14 26 3 3 Implementation of the 3D Map Deformation The implementation of the 3D Map deformation has been motivated due to the necessity of visualize the effect of the gravel simulation algorithm form the ALLO Project in the gravel piles when the wheel loader takes material from them Gazebo doesn t have a lot of variety of options to implement the change or update of a mesh in simulation time One possible option for the implementation of the map deformation is having the variable parts of the terrain like a different mesh In this way Gazebo has a helper script called spawn model is provided for calling the model spawning services offered by gazebo ros It has been received from the ALLO project three COLLADA triangle meshes of the different levels of a grave pile Figure 3 3 1 b c d These meshes have been computed using the ALLO Project gravel simulation algorithms And using the gazebo s
19. del It can be also modified the damping of the joints By default in URDF the joints have 0 dumping on the controlled position joints the steering joint the mechanical arm and the bucket when we try to move some joint and it arrive to the desired position the joint starts to bounce and finally converge to the position It has been reduced on the mentioned joints the dumping force to 50 Newton meter seconds per radian A 50 value shows a realistic dumping but you can reduce the dumping until 300 if it is reduced more the dumping the model it will destroy Related to the friction is possible to modify the friction related to each material modifying the two friction coefficients of each material which specify the friction in the principle contact directions as defined by the ODE physics engine used by Gazebo These tags represent the friction coefficients u for the principle contact directions along the contact surface as defined by the ODE physics engine of Gazebo Is also possible modify the friction related of each joint 1n the friction tags of the joints It has been defined the coefficient of the wheels material the kinetic coefficient like 0 68 and the static like 0 9 This 1s the coefficient of dry rubber on asphalt 15 And It has been defined the friction of the mobile joints with 50 But changing these values doesn t show any significant change on the behaviour of the vehicle The only physical engine with works with a full fu
20. der Simulator Samuel Navas Medrano USER MANUAL Wheel Loader Simulator 1 Index L T ET A E N 1 Piel 2 Zl D wnl d and Install aai 2 22 Configuring Your ROS Environment eese nennen nne nnne 3 2 9 Installing the Wheel 848 5 310 4 c 7 2b bog he Dt U6 qereenmeenre E 7 Folowing SImMUlIOr ERR 9 2 T ND T EEA 10 At ON 10 10 11 USER MANUAL Wheel Loader Simulator 2 Installation This manual assumes that you are using Ubuntu 13 04 Raring 2 1 Download and Install ROS 1 Configure your Ubuntu repositories to allow restricted universe and multiverse You can follow the Ubuntu guide for instructions on doing this 2 Setup your computer to accept software from packages ros org ROS Hydro ONLY supports Precise Quantal and Raring for debian packages
21. e ability to replace part of the 3D map to another and the ability of the vehicle to follow a path given a list of waypoint have been also completed Related to the Step III it has been done an interface for the ALLO Project using the ROS topic structures Only it has not been completed the asphalt plant model due to it has been dedicated more resources to solve and improve the others aspects of the simulator Even the uncompleted aspects the project 1s a suitable solution to the problem presented from the ALLO Project of the porting and development of their previous simulator 5 3 Specific results and conclusions It is possible to simulate the behaviour of a wheel loader vehicle in a realistic environment using ROS and Gazebo in spite of their limitations And will be interesting to continue the development of the simulation at the same time as Gazebo and ROS grow 5 4 Project development The simulator has been developed following the standards in the using of the ROS and Gazebo frameworks which allows an easy expansion of it and its functionalities Expand and enhance the project should be able in the future at the same time that ROS and Gazebo grows Examples of tasks which should be developed in the future are the following e Complete the Step III of the project e Enhance the L120F Prototype with a more realistic physics and visuals e Enhance the driving mechanism of the vehicle o Have a better control of the velocity of the vehicle
22. e an informative visualization or a nuisance In addition the Hyokuo laser plugin will publish all the data obtained from the sensor to the 1120f laser scan topic It has been also implemented a camera sensor which publish on the 1120f cameral image raw topic and an Odometry sensor which publish on the 1120f odometry data topic After a meeting with the client the configuration of the laser was changed to be like a SickLMS200 scanner the same sensor that uses the old simulator from the ALLO Project And more importantly the same that we use on the real machine However it has been decided not to implement the GPU IMU and Odometry sensors these sensors aren t included in the gazebo ros libraries and we have to depend of community packages to implement it Due to we are working with a simulation this information can be obtained directly from Gazebo instead from the simulation of these sensors Nevertheless I have looked for the packages what should implement leaving sensors the hector gazebo plugings package implements different sensors plugins like a 6dw differential drive an IMU sensor an Earth magnetic field sensor a GPS sensor and a sonar sensor Another option for an IMU sensor plugin is the microstrain 3dmgx2 imu plugin which is compatible with the microstrain 3DM GX2 and 3DM GX3 protocol Figure 3 2 2 Bounding box of the bucket s mesh 12 26 Available controllers controller manager tests EffortTestContro
23. e other structures like the rear frame the suspension the articulated arm etc are represented by cuboids boxes For the pieces that before were represented by meshes the front frame and the bucket the first approach was represent it as boxes of an approximated size but later them I replaced it modelling a new COLLADA meshes using Blender See Figures 3 2 2 and 3 2 5 The format which gazebo uses to the description of robot models 1s Simulator Description Format SDF but It has been parsed all the information of the previous project model to the Unified Robot Description Format URDF and it has been used the XACRO tool to clean up our URDF files It has been chosen this format instead of SDF because is the most extended and standardized XML format for the description of robots However in the process of the reconstruction and parsing of the previous model into de URDF format we have discovered some issues The first is that some features of URDF have not been updated to deal with the evolving needs of robotics URDF can only specify the kinematic and dynamic properties of a single robot in isolation neither can specify the pose of the robot itself within a world This is not a big deal because Gazebo 15 going to solve these points however there is a problem which gazebo can t deal with it the hierarchical data structure in URDF that does not allow for loops parallel joints that the previous model of the wheel loader has in the mechanical
24. effort 20 6 6 0 0 25 0 80 2 0 Eu up dm Figure 3 4 2 Actual path description 18 26 4 Results The result of the project has been evaluated by the researchers of the ALLO Project They are generally happy with the state of the simulator The final point of the requirements interface for communicating with the simulation is actually quite important and it s good to see that it 15 in place using the ROS topics listed 1n the user manual Since Rviz can show the poses of all the links of the vehicle and the simulated laser data that also means that the output of the simulator looks essentially the same to our software as the data from the real robot The main issue with the current simulator 1s the lack of velocity control Given that this controller is not fully functional in Gazebo 1 9 it is understandable that it wasn t implemented but that is something we will need to work around for future development of the simulator Magnusson Martin result notes from the ALLO Project The resulting code of the simulator is also well documented and easy to use in a future development 19 26 5 Discussion 5 1 Achievement of the course objectives 5 1 1 Knowledge and comprehension During this project it has been acquired deep theoretical knowledge in rigid body simulation that 15 being performed by Gazebo And it has been acquired following competences e Work with an officially unsupported GPU in Ubuntu 13 04
25. es 8 3 1 1 Model structure and measurements ccccccccccccccccccccccccccccccccccccccccccceccscsccccceccccccccccecccccceccees 8 3 1 2 Controllers ueni i zo be Cose ocu ove esta eva soe 11 3 1 3 ISIN EORR TT RENT 12 3 2 IMPLEMENTATION OF THE 3D MAP cccccccccsccccccccccccccccccccccccccccccccccccccccccccccccecccs 14 3 3 IMPLEMENTATION OF THE 3D MAP DEFORMATION ccccccccccccccccccccccccccccccccccccccccccs 15 3 4 IMPLEMENTATION OF THE PATH FOLLOWING cccccccccccccccccccccccccccccccccccccccccccccsces 15 d a iaa a AREO EE SESER 19 MEME DISCUSSION eec mc 20 5 1 ACHIEVEMENT OF THE COURSE OBJECTIVES ccccccccccccccccccccccccccccccccccccccccccccccccccces 20 5 1 1 Knowledge and comprehension d eee ee eoe eee ee eaa eene espe eee e vao ee Eee E Fee eu ee S UE RNC e RE EUREN 20 5 1 2 Prohiciency and ciiin 20 5 1 3 Values EET E 21 5 2 COMPLIANCE WITH THE PROJECT REQUIREMENTS cccccccccccccccccccscccccccccsccccccccccces 21 5 3 SPECIFIC RESULTS AND CONCLUSIONG cccccscccscccccccccccccccccccccccccccccccccccccccccccccccceccss 21 54 PROJECT DEVELOP MEN D lt osctackecesscehsncctacsschsshduuedeveuncddesdenecacdensdevacsue eva 21 0 REFERENCES o 22 APPENDICES A URDF hierarchy B Wheel Loader Simulator User Manual 3 26 1 Introduction 1 1 Objective The purpose of emerging a visual simulator
26. f the simulator 15 possible because of the generous software licenses used by ROS and Gazebo The core of ROS licensed under the standard three clause BSD which 15 a very permissive licence that allows for reuse in commercial and closed products the other parts of ROS like community packages usually uses licences such Apache 2 0 licence GPL licence MIT licence Gazebo requires a graphic card with OpenGL 3D acceleration to perform various rendering and image simulation tasks correctly But it can still working without it at the expense of not having camera simulations and a working Gazebo UI But even with these disadvantages it 1s still useful for testing algorithms A laptop with a dedicated graphic card has been used for develop the project A Lenovo IdeaPad Z580 with a Intel R Core TM 17 3612QM CPU 2 10GHz CPU working a Nvidia Optimus configuration with the following GPUs NVIDIA GeForce GT 630M amp Intel R HD Graphics 4000 6 26 Also additional software has been used in this project e Ubuntu 13 04 Raring o Bumblebee v Ubuntu 12 10 e Windows 7 o Adobe Photoshop CS6 Extended o NVIDIA Texture Tools for Adobe Photoshop o Blender 2 63a 2 2 4 Installation of the software tools During the project it has been used ROS Hydro Medusa this version of ROS only supports Ubuntu 12 04 Precise Ubuntu 12 10 Quantal and Ubuntu 13 04 Raring It has been installed the latest version of the supported Ubuntu releases Ubuntu 13 04
27. gs included but if not or if you installed anoter version of ROS you can still installing these packages typing sudo apt get install ros hydro gazebo ros pkgs ros hydro gazebo ros control 2 2 Configuring Your ROS Environment The first step is to create a ROS Workspace Mellie Gene LIU wey Sis ree eae ames Cercle clle weoicl lt epece Even though the workspace is empty there are no packages in the src folder just a single CMakeLists txt link you can still build the workspace Gsrcleiia Wwe catkin make The catkin make command is a convenience tool for working with catkin workspaces If you look in your current directory you should now have a build and devel folder Inside the devel folder you can see that there are now several setup sh files Sourcing any of these files will overlay this workspace on top of your environment To understand more about this see the general catkin documentation catkin Before continuing source your new setup sh file S source devel setup bash USER MANUAL Wheel Loader Simulator 2 3 Installing the Wheel Loader Simulator 1 Copy all the folders the catkin_ws to your catkin_ws folder and the gazebo folder to your gazebo folder catkin_ws and gazebo folders are by default in your home folder Please note that gazebo is a hidden folder Your hierarchy should be as follows catkin_ws src 1120f description package xml CMakeLists txt u
28. i Robot Simulator Intelligent Robots and Systems 2004 IROS 2004 Proceedings 2004 IEEE RSJ International Conference on 2004 Robotics Research Labs University of Southern California Los Angeles CA 90089 0721 USA Accessed 16 of June 2014 URL http robotics usc edu gerkey research final_papers icar03 player pdf Cousins Steve Gerkey Brian Conley Ken Staff from Willow Garage Sharing Software with ROS IEEE Robotics amp Automation Magazine June 2010 pp 12 14 Willow Garage Menlo Park CA USA Accessed 16 of June 2014 URL http ieeexplore ieee org stamp stamp jsp arnumberz05480439 Willow Garage ROS Robot Operating System 2014 Menlo Park CA Willow Garage Accessed 16 of June 2014 URL https www ros org Quigley Morgan Gerkey Brian Conley Ken Faust Josh Foote Tully Leibs Jeremy Berger Eric Wheeler Rob Ng Adrew ROS an open source Robot Operating System Proc Open Source Software workshop of the International Conference on Robotics and Automation ICRA 2009 Computer Science Department Stanford University Stanford CA Willow Garage Menlo Park CA Computer Science Department University of Southern California Accessed 16 of June 2014 URL http a1 stanford edu mquigley papers icra2009 ros pdf 22 26 9 NVIDIA Corporation Whitepaper NVIDIA s Next Generation Notebook Technology OptimusTM Accessed 16 of June 2014 URL http www nvid
29. ia com object LO optimus whitepapers html 10 The Bumblebee Project Accessed 16 of June 2014 URL http oumblebee project org 11 Volvo Corporation Volvo Wheel Loaders LI IOF LI20F Accessed 16 of June 2014 URL http www volvoce com SiteCollectionDocuments VCE Documents 20Global w heel2c20loaders ProductBrochure L110E L120F EN 21C1002738 2009 08 pdf 12 OGRE Open Source 5D Graphics Engine Accessed 16 of June 2014 URL http www ogre3d org 13 G nther Martin Sprickerhof Jochen UOT tools Accessed 16 of June 2014 URL http wiki ros org uos tools 14 Blender Foundation The Blender project Free and Open 3D Creation Software Accessed 16 of June 2014 URL http www blender org 15 Wikibooks Physics Study Guide Frictional coefficients Accessed 16 of June 2014 URL http en wikibooks org wiki Physics Study Guide Frictional coefficients 16 Smith Russell Open Dynamics Engine Accessed 16 of June 2014 URL http www ode org 17 Coumans Erwin Bullet physics engine Accessed 16 of June 2014 URL http bulletphysics org 18 Meyer Johannes Kohlbrecher Stefan Hector gazebo plugins Accessed 16 of June 2014 URL http wiki ros org hector gazebo plugins 19 Leibs Jeremy Gassend Blaise microstrain 35dmgx2 imu Accessed 16 of June 2014 URL http wiki ros org microstrain 3dmgx2 imu 20 NVIDIA Corporation NVIDIA Texture Tools for Adobe Photoshop Accessed 16 of
30. is information about the pose and orientation of the vehicle to ROS through a ROS topic using nav msgs Odometry ROS messages I have configured this plugin to use the position of the rear frame as reference to take the odometry information and sent via the base pose ground truth topic The next step was to develop a ROS subscriber C program to correctly receive and interpret the odometry information of the vehicle from the topic I have taken as a reference the code of the Writing a Simple Publisher and Subscriber tutorial from the ROS wiki Once we received a message from the topic we can be able to extract the X and Y coordinates from the pose of the vehicle and the quaternion of its orientation and then converts it to pitch from the roll pitch yaw vehicle orientation system using the following equation PITCHayg g atan2 2 yx wz ww xx yy zz 15 26 Now with the position and orientation of the vehicle I had to develop the way to represent a path and send the property information to vehicle to follow it I have taken as a reference some examples of back and forths path that I received from the ALLO Project Figure 3 4 1 and then I have implemented a simpler way to describe the waypoints of a path using only the position the angle of the direction joint of the wheel loader in radians and the expected pitch angle of the vehicle as we can see in the Figure 3 4 2 Then each time we receive a odometry message the subs
31. is twofold First it enables more rapid testing and development of the algorithms compared to testing them on the hardware platform and second it makes it possible to create visual demonstrations for public dissemination The use of simulators when developing robotic systems provides the advantages of the efficient development and testing of robotics applications saving time and resources and making easier publics demonstrations This thesis project consists on the simulation of a wheel loader at an industrial environment in the cycle of material handling The usage of a robotic simulator will offer advantages in terms of safety costs efficiency and availability as well as environmental advantages All these advantages compared to testing the algorithms on the real vehicle in its working 1 2 Background Mobile Robotics and Olfaction Lab MR amp O is part of the Centre for Applied Autonomous Sensor System at Orebro University MR amp O is focusing on research perception systems for mobile robots and advance the theoretical and practical foundations that allow mobile robots to operate 11 an unconstrained dynamic environment Autonomous Long Term Load Haul Dump Operations is a Joint project by the MR amp O Lab Volvo Construction Equipment and NCC Roads The goal of the ALLO project is to find a solution to the demand for efficient material transport in many industrial environments The employment of autonomous mobile robots in
32. ller controller manager tests MyDummyController diff drive controller DiffDriveController effort controllers GripperActionController effort controllers JointEffortController effort controllers JointPositionController effort controllers JointTrajectoryController effort controllers JointVelocityController force torque sensor controller ForceTorqueSensorController imu sensor controller ImuSensorController joint state controller JointStateController position controllers GripperActionController position controllers JointPositionController position controllers JointTrajectoryController velocity controllers JointVelocityController Figure 3 2 3 List of Gazebo 1 9 available controllers G GAzEBO ROS ros control Simulation Hardware Reality nputOutput Encoders Actuators Sensors on the rea robot Servos etc read Sim write Sim Embedded Controllers 0 PID loop to follow effort setpoint Gazebo Plugin qos control gazebo ui Loads RobotHW interfaces via plugnib write wo N DDASS N SSS Joint State interface Joint Command Interfaces Hardware Resource Interface Layer NS e g JointStateintert e g Efforvointintertace NS SSS WSSSSSSSSSSSNINN Joint States Jom Efforts racdans Nm list controllers LC ads inloads ant Pa S f pdat O co load controller unload controller Switch controller
33. ls of actual work sites The simulator also will make it possible to evaluate algorithms for task and path planning in a much more efficient way than would be possible otherwise The development of this simulator enables more rapid testing and development of the algorithms developed within ALLO compared to testing them on the hardware platform that is available in Eskilstuna And it makes it possible to create visual demonstrations for public dissemination 1 26 Preface I would like to thank Martin Magnusson for giving me the opportunity to take part in this project and for guide me through it 2 26 Contents 1 ER 4 EE a 4 L BACKGROUND eneidiaa 4 L3 PROIECT 32 55 35 deitate iie tete TE PEP Te 4 cates 5 L5 JOUTEINE ned e 5 2 WIR THODS AND TOOLS iste vie E eas vh Safe 6 SINE USC PRSETER 6 22 oder 6 211 Installation of the software 00 6 eee eee eee ee eee sees 9 66 90 7 2 3 OTHER RESOURCES cM e M EE 7 5 ZINIPLEMENTA TION sisieun Eo SR ERR URURu nca a Qe ea nen Ioue Gan 8 3 1 IMPLEMENTATION OF THE WHEEL LOADER AND SENSORS ccccccccsccccccccccccccccccccccce
34. nctionality in Gazebo is Open Dynamics Engine ODE 6l when I tried to use the Bullet engine L17 instead of ODE Gazebo would not load at all because the Bullet integration in Gazebo 1 9 1s still experimental 10 26 3 1 2 Controllers Once the 3D model of the wheel loader was constructed the next step was the implementation of a control system to grant movement to the model There are a lot of alternatives to perform this if we were a bigger project the ideal way to control the model will be to make our own gazebo model plugin and create our own gazebo custom messages model But another simplest and efficient way to implement it is to use the gazebo control plugin it have all the resources we need to implement a good way to control the movement of the robot and it is a standard plugin of Gazebo ROS and uses the standard messages std msgs of Gazebo that means that the control mechanism will be easier to understand for a person who incorporates to the project later and the control mechanism will be easier to enlarge also in a future 1f we want to enhance the movement mechanism control libraries works like a controller interface between the ROS controller manager mechanism and the hardware interface whether it 1s real hardware or simulated hardware by Gazebo as represents the Figure 3 2 3 We were able to use different interfaces to make possible the communication between the control manager and the robot s hardware This
35. ng of inertias of 1 2 or smaller like elements in the inertia matrix because 1 is often much too high making the model hard to drive with an unnatural behaviour The usage of a default inertia matrix is enough for the purpose of the project but a calculated inertia mass for each piece will be a more complete and realistic solution having as result a more precise and realistic simulation The inertia matrix has been calculated according to a list of moment of 9 26 inertia tensors using the uos tools package from the University of Osnabr ck knowledge based systems group PL m 3r h 0 0 1 2 lee 0 m 3r h 0 0 0 mr 2 m h d 0 0 1 2 2 Dose 0 mw d 0 0 0 m w h Solid cylinder of radius r height h and mass m Solid cuboid of width w height h depth d and mass m www wikipedia org 2014 The Icvr mpeg matrix has been applied to the wheels and the Icugom matrix to the rest of the pieces of the model It has been simplified the inertia of the pieces represented by meshes like if 1t were cuboid using the dimensions of their bounding boxes See Figure 3 2 2 Another detail about the inertia of each body of the model and the centre of mass of them is that URDF have to specify the location of each model in the joints tags instead of in the link tags like the previous model if not the inertia matrix will be ignored and the centre of mass of each body in the model with be the origin of the mo
36. oject during weekly meetings with the client the researchers working in the ALLO project 2 2 Tools ROS Robotic Operating System is the main development framework used in this project It is an Open Source framework which has tools for the building of robotics applications and 1s maintained by the community in a very collaborative environment ROS provides libraries and tools to help software developers create robot applications In addition also Gazebo Simulator was used complementing ROS it offers the ability to accurately and efficiently simulate robots in complex indoor and outdoor environments and has a wide variety of physics engine including ODE Bullet Simbody and DART Using OGRE Gazebo also provides a realistic high quality graphics including high quality lighting shadows and textures Gazebo also has a convenient programmatic and graphical interface The documentation of ROS the wiki and tutorials and the Q amp A site have been a great support during the course of the project The ROS community has over 1 500 participants on the ros users mailing list more than 3 300 users on the collaborative documentation wiki and some 5 700 users on the community drivenROS Answers Q amp A website The wiki has more than 22 000 wiki pages and over 30 wiki page edits per day The Q amp A website has 13 000 questions asked to date with a 70 percent answer rate http www ros org 2014 Reusing these libraries for the development o
37. pawn service we can delete a model of a pile and replace it with the same model modified in simulation time However the Gazebo s spawn scripts have some issues and we can t spawn two times a model with the same name so when was implementing the changing of a mesh in simulation time on the existing bash script of keyboard control I had to count the times I was spewing the model and change its name to pile n where n 15 10 1 2 nj 3 4 Implementation of the Path Following Related to the ability to follow a given path first It has been looked for some Gazebo and ROS official libraries to help to perform it but it has been found only libraries of path planning these are the ROS 2D Navigation stack and the Motion Planners stack they take information from odometry and sensors streams and output velocity commands to send to a mobile base We want a simpler solution our wheel loader will move in the same map doing a repetitive movement from the gravel piles to the asphalt plant s containers In this project it is not going to explore a new map We rather want to use it to try out our algorithms for navigation motion planning etc 5o we only need to receive information about the location of the robot in our known map and depending of this location send to it new data about it velocity and orientation It has been used the P3D 3D Position Interface for Ground Truth controller plugin this plugin simulate an odometry sensor and sends th
38. r The first two controllers wasn t able to load by Gazebo the third loads but makes the model crash the joint hierarchy is destroyed and Gazebo visualizes al the joints together without any sense and I only could load the JointEffortController this controllers makes possible to spin the wheels and move de vehicle but we cannot control the velocity of it for example with the same effort the velocity will be different if the vehicle is climbing a hill o driving in a flat ground All the controllers can be seen in the Figure 3 2 4 With the action of the controllers of these interfaces the L120F robot will modify the respective properties of each joint when it receive a standard message in each controller It has been written a UNIX Bash Script to automate the sending of messages and to have an intuitive way to drive and control the articulated wheel loader model interactively by keyboard It has been chosen the use of UNIX shell scripting instead C due to the facility of the implementation and the absence of the necessity of compile the code after each small 11 26 change and the necessity of being multiplatform 3 1 3 Sensors The final step in the model implementation is the addition and configuration of sensors to the model It has been added a laser scan sensor configured like a Hokuyo laser to the top to the wheel loader machine With it a semi translucent laser ray is visualized within the scanning zone of the GPU laser This can b
39. rdf 1120f urdf xacro 1120f mod urdf xacro launch 1120f rviz launch 1120f mod rviz launch meshes cad 1120f gazebo package xml CMakeLists txt launch 1120f launch path following launch worlds 1120f world path following world models USER MANUAL Wheel Loader Simulator 1120f control package xml CMakeLists txt launch 1120f control launch config 1120f control yaml sim controller package xml CMakeLists txt key teleop sh ASEC 1120f control launch srv srv paths pathi dat gazebo models wp3 pile00 dae wp3 pile 5 dae wp3 pile49 dae pile00 11605 pile49 2 Copy all the files and folder from the gazebo to your Gazebo folder usualy gazebo 200 MENU USER MANUAL Wheel Loader Simulator 3 Build the workspace eol f Gul qe 4 Source the files S source devel setup bash USER MANUAL Wheel Loader Simulator 3 Execution 3 1 Driving Simulator The driving simulation consists on a simulation of the L120F Volvo Whel Loader on the Elkistsuna Kjula map You can also drive the vehicle and change the type of gravel pile on the scenario using the keyboard To load the scenario type o O Ii 5 TE a Ii To load the L120F controller type Sees laune lh eon mise oma it You can now execute the key_teleop sh bash script and start driving the wheel loader Sexe Gatkiny sve Sms cT ox S key teleop sh
40. t manage well the physics of body with huge masses provoking the explosion of the model Finally it has been adopted masses of approximately of 1 kilogram in each piece of the wheel loader The final dimensions of each body of the LI20F model can be seen in the Figure 3 2 1 In addition the previous meshes of the L120F model were compiled in OGRE but in a previous version that Gazebo 1 9 doesn t recognise it have been converted the compiled meshes back to their original OGRE XML files using the OgreXML Converter tool and it has been tried to convert it to another format which Gazebo load But due to the low complexity of the meshes we have decided that will be easier and quicker to remake using Blender the front frame and bucket meshes in the COLLADA XML format than convert the previous one to it Body Type Dimensions Figure 3 2 1 L120F model measurements in meters Another issue on the parsing of the model 1s that the previous version has not specified information about the inertia of the pieces of the model but in our actual version of Gazebo and ROS is necessary to specify the inertia in the model The inertia tensor encodes the mass distribution of a body so it does depend on the mass but also on where it 1s located and 1s represented in URDF with the diagonal and upper elements of a symmetric matrix One of the possible solutions is to use an identity inertia matrix as default in the model Another solution is the usi
41. using Bumblebee e Install and Configure a ROS and Gazebo Environment e Navigate the ROS Filesystem and create the ROS packages following the catkin standard Understand ROS Nodes Topics Services and Parameters Build and modify a Gazebo world Build a physical realistic robot using URDF and XACRO Use a URDF model in Gazebo Use a heightmap in Gazebo Make SDF models Import and attach meshes to the URDF and SDF models Add different sensors to a robot Use Gazebo plugins in ROS Work with the gazebo ros control plugin for the ROS communication with Gazebo Publish into a ROS topic to modify the state of a robot s joint in Gazebo Subscribe into a ROS topic to show information about the robot in Gazebo in Rviz 5 1 2 Proficiency and ability During this project it has been acquired the following abilities e Draft and define the technological problem of the realistic simulation of robotic hardware and rigid bodies e Search for scientific information to solve these problems in scientific databases such as IEEE Explore and Google Scholar e Plan and implement a technological project in a professional environment using an incremental development model with some iterative elements Defining an initial set of requirements and redefining them during the course of the project e Process and analyse scientific results as it can be seen in the results section e Have the ability to present the project orally and writing e Have control of pl
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