User Manual - The Image Section
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1. Listings Diiveecxample zai sor sE p Pave eo a Se eee GS Pe 2a He bee a 6 IR range sensor example O Geo e ae ii Eea ee EAA OO de a ee ee es 7 Front b riper example os ocorre a i ir DA RE RS ana AOR A i aaa 9 1 USER MANUAL 1 User Manual This manual for using Player Stage on the Scorpion robots will help you get started writing robot control programs It assumes that Player version 2 0 3 or greater and Stage version 2 0 1 or greater have already been installed on the local system and that the source package in the following referred to as the source package has been checked out from the DIKU ImageLab SVN repository ERSP 3 1 software Evolution Robotics Software Platform is required to be installed for using the physical Scorpion robots The manual will first give you a brief introduction to Player Stage and the features of the Scorpion robots Following are examples on using the various sensors and actuators supported by the Scorpion robots For the first few examples Stage the 2D simulator for Player will be used Later examples will move on to run programs on the physical Scorpion robots If you encounter any errors while going through this manual please refer to Section 1 10 which has details on some of the most common errors 1 1 Getting Started To give you an idea of how the basic system works here is a quick 3 step guide to getting started It uses the Makefile in the root directory of the source package to simplify initial2. Unable to communicate with resource driver IR_bn_ene Please check hardware connection WARN returning comm write error WARN RCM4 command f9 failed with result 32724 WARN Unable to communicate with resource driver IR_tn_edown Please check hardware connection WARN returning comm write error WARN RCM4 command c0 failed with result 32724 To fix the issue you need to shutdown the Player server Use the following command from any terminal killall player You can then reconnect the laptop and robot and restart the Player server to continue 1 11 Other Topics The manual has only touched briefly the world of Player Stage This section will try to give you a taste of other interesting topics and where to find more information 1 11 1 Other Languages All examples in this manual so far have used C for programming the robots However Player Stage supports a variety of other languages for writing robot control programs Be sides the C and C client libraries bundled with Player are clients for Python Scheme LISP and Java to name a few See the Player Wiki page for a list of supported languages and how to get started using them Note that some languages do not yet provide a complete implementation of the Play er Stage 2 0 API so before considering using a language other than C or C be sure to check the project page of the client library you want to use 1 11 2 Virtual Drivers One of the interestin
3. ization of the Player server 1 From the root folder of the checked out source package build the drivers and test programs by running make 2 Start the Player server To make Player use the Stage simulator pass it the cave world configuration file 5 make stage cave cave cfg 3 Start a test program A good and simple example is the random walk test program that uses the IR range sensors to navigate Start it by running randomwalk The robot in the window of the Stage simulator should now be exploring the cave world To stop the test program press Control C in the same console you started the program The robot in the simulator should stop moving You can resume control over the robot by simply restarting the test program Normally there is no reason to restart the Player server unless you have changed some of its configuration files If you want the robot to return to its starting position simply drag it to the desired position in the Stage window Stage has several settings worth exploring see Section 1 9 for a brief overview The Player server can be shutdown by running the following command in the same ter minal it was started o make stop This will also shutdown the simulator window and any robot control programs con nected to the Player server 1 2 A Brief Overview of Player Stage 1 USER MANUAL Robot Control Program playerprint Program Player Server Scorpion Robot Driver Stage Simulation Driver A
4. User Manual for ERSP Player Driver Source Package From the project Player Stage Player driver implementation for ERSP Bue Petersen lt buep diku dk gt Jonas Fonseca lt fonsecaldiku dk gt Department of Computer Science University of Copenhagen Winter 2006 CONTENTS LISTINGS Contents Contents 2 List of Figures 2 List of Tables 2 Listings 2 1 User Manual 3 Li Getting Started lt sg awk tae ee AA Ad oe GS a ee a 3 1 2 A Brief Overview of Player Stage a s gs kaona eos Pee ERS S SSH 4 1 9 he Scorpion RODOS vereda dar a eee Ee eee 5 1 4 Taking the Scorpion Robot for a Spit isis air 6 1 5 Using the Sensors 22s kes he See SSS Rda er 7 1 6 Running on the Physical Robots 3 44 44 02 285 rss 2433494 8 17 supported Interfaces 62 26 4 rhage i E a So A 8 135 Advanced Sensor Usage 4 04 dote s spie ae aS WEEE SERS PERS 8 1 9 Une Player Toolbox sce aa don GA GOR Kl Se Re aC BSS 10 1 10 Known Limitations and Problems 00000084 10 LIL Other Topics y xe bd ee ba ea oe ea ee eRe dee Bae a RS 12 IT Other Languages aces 64 e hab oe Ore PR Re ore Se Oe 12 1 11 2 Virtual Drivers s sacs aasa 00 000 000 2 eee aia e 12 1 11 3 Further Reading 4644424545 0 24sGt0hoxvbabaa bas 12 List of Figures 1 The Player Fram Work os haces so Oy He cae eed RR ea a 4 2 stage Scorpion IR range sensors 425406 n04 24268 8a we baw ae Re 5 List of Tables 1 Supported Playerimterlaces sss fe eho Ra ee a ee we RR da 9
5. argc char argv Since there is no processing of sensor data taking place in this example it moves on to commanding the robot The first command will move the robot forward with a speed of 20 centimeters per second Player by default uses meters as the basic length unit thus it is specified as 0 20 The robot will continue executing this order until another command is issued To give the robot time to move forward the program will sleep for 3 seconds position SetSpeed 0 20 0 0 sleep 3 To turn the robot pass a non zero value as the second argument to the Set Speed method For 3 seconds turn the robot rightward with an angle of 0 50 radian per second position SetSpeed 0 0 0 5 sleep 3 Alternatively you can use the DTOR macro to convert angles in degrees to radians For another 3 seconds turn the robot leftward with an angle of 30 degrees per second position SetSpeed 0 0 DIOR 30 sleep 3 When done stop the motors so the robot is in a safe state when the program terminates position SetSpeed 0 0 0 0 return 0 Compile the robot control program by using the following command o gt o move turn pkg config cflags libs playerc test move turn cc Before running the move turn program remember to restart the Player server with the cave world configuration file if you stopped it in the previous section NO UV BF WN BR 20 21 22 23 1 5 Using the Sensors 1 USER MANUAL 1 5 Us
6. diku PlayerStage driver lib trying to load home diku PlayerStage driver lib libersp success invoking player_driver_init Registering ERSP driver success Listening on ports 6665 The following error is reported when a robot control program is started and no Player server is running playerc error connect call on localhost 6665 failed with error Connection refused See Section 1 1 or 1 6 for information on starting the Player server with or without the Stage simulator backend A failure to subscribe to a device will generate the following error messages warning skipping subscription to unknown device 14 0 playerc error got NACK from request playerc error failed to get respons Shutting stage driver down stage driver has been shutdown BumperProxy BumperProxy 1 could not subscribe closing connection to client 0 on port 6665 See the end of Section 1 7 for and example of how to avoid this error by conditionally subscribing to devices If for any reason the USB cable connecting the laptop and the robot is unplugged the ERSP library will start printing a lot of warnings in the terminal window where the Player server was started WARN Failed to read batteries WARN Unable to communicate with resource driver Battery Please check hardware connection WARN returning comm write error WARN RCM4 command 40 failed with result 32724 11 1 11 Other Topics 1 USER MANUAL WARN
7. est bump stop cc Note this example can only be run on the physical Scorpion robots as the bumper device is available in the simulator This concludes the program examples in this manual More examples are available in the driver source package s test directory Here you will find the output program which dumps data from all sensors including the vertical bumper sensors for which no example has been given 1 9 The Player Toolbox Player Stage comes with a rich set of tools some of which are worth getting acquainted with playerv also known as the Player Viewer is a tool for examining and in some circumstances controlling devices provided by a running Player server The basic idea is that you can subscribe to the devices in which you are interested For example by subscribing to the position2d 0 device in the Devices menu you will be able to see the current velocity and pose of the robot playerprint is a simple alternative to playerv which dumps sensor data to the console stage has several helpful features for debugging your program For example you can vi sualize the IR range sensors by enabling the ranger config entry in the View menu The same menu also contains Show trails which over time will color the path of the robot The File menu in the Stage GUI also allows you to grab a screenshot or capture a movie 1 10 Known Limitations and Problems Some of the most common problems you might run into are listed below Amon
8. g features of the Player Stage system is the notion of virtual drivers An example is the amc1 driver implementing the Adaptive Monte Carlo Localization algo rithm It uses odometry data from a position2d interface a laser interface for scanning surroundings and a map interface holding a map in which to localize the robot In return it provides a localize and aposition2d interface Virtual drivers usually take input from a collection of existing raw Player interfaces process this input and provide a higher level interface If you are implementing a generic algorithm that you would like to use in several projects or make available for others to use consider making it a virtual driver 1 11 3 Further Reading If you are interested in reading more about how to use Player Stage here are some relevant online resources http playerstage sourceforge net wiki PlayerClientLibraries 12 1 11 Other Topics 1 USER MANUAL e The Player Stage website http playerstage sourceforge net e The Player wiki http playerstage sourceforge net wiki e The Player Manual http playerstage sourceforge net doc Player 2 0 0 player e The C Player client library http playerstage sourceforge net doc Player 2 0 0 player group__player__clientlib__cplusplus html e Manuals for Player utilities http playerstage sourceforge net doc Player 2 0 0 player group__utils html 13
9. g them are some Player error messages that might need clarification e To localize the install path of Player header files and libraries the pkg config pro gram is used If it fails to find the installed Player C library package configuration file called playerc pc it report that Package playerc was not found in the pkg config search path Perhaps you should add the directory containing playerc pc to the PKG CONFIG PATH environment variable No package playerc found 10 Known Limitations and Problems 1 USER MANUAL 1 10 To solve the problem add an entry to your the configuration file of your shell For example if you are using Bash and installed Player into usr local add this line to bashre export PKG_CONFIG_PATH usr local lib pkgconfig PKG_CONFIG_PATH Before continuing remember to source it or open a new terminal to make it take effect Use the env command to check if it is set It can be hard to determine when the Player server has completed its initialization and are ready to be used The server will first look at the PLAYERPATH environment variable to look for plugin drivers It will then try to load any plugins In the example below the ERSP Player driver is loaded and the driver prints that it has registered itself Finally the server prints the port it is listening on in this case uses the default port After the port number has been printed the server is ready PLAYERPATH home
10. have a narrow beam and their range is 10 cm 80 cm They are positioned on the robot so the first 10 cm of the range are on the robot That is if they detect obstacle within 15 cm the obstacle is 5 cm from the robot 2 servo motors are available for controlling the front wheels The rear end wheel is simply for support The robots also have a camera mounted on top which can be used either via Player or the OpenCV library How to do this is beyond the scope of this manual Additionally in the simulator odometry data from the front wheels can be used to track the movement of the robot 1 4 Taking the Scorpion Robot for a Spin 1 USER MANUAL 1 4 Taking the Scorpion Robot for a Spin To give you an idea of how to write a robot control program the first simple program will make the robot drive forward stop it and then turn it left and finally right You can find the program in the test move turn cc file in the source package First include the header file of the Player C client library include lt libplayerc playerc h gt using namespace PlayerCc Next establish a connection to a Player server running on the local machine by construct ing a client object and use this object to subscribe to the position device used for controlling the motors on the Scorpion robot PlayerClient robot localhost Position2dProxy position amp robot Like any other C program the starting point is the main function int main int
11. ing the Sensors The Scorpion robots are equipped with three different types of sensors Two of them are bumper sensors dedicated to hazard avoidance and the last provides information about ranges to near by obstacles In the following example the range sensors will be used to avoid obstacles in front of the robot by turning the robot before moving forward again The program preamble is similar to the previous example however this time the range sensors will also be used As a result the scorpion h header file is included and an IR device declared include lt libplayerc playerc h gt include lt scorpion h gt using namespace PlayerCc PlayerClient robot localhost Position2dProxy position amp robot IrProxy ir amp robot Sensor devices can be thought of as providing a continuous source of sensor readings which are buffered in the robot control program Consequently it is necessary for the Player client to continuously synchronize and process these readings so it can update the robot device objects This is done by periodically calling the Read method A good way to achieve this is to call it in the start of the program s main loop int main int argc char argv while true robot Read To see if there are any obstacles in front three of the IR front sensors are checked If either of them are reporting ranges less than 50 centimeters turn the robot if ir SCORPION_IR_TW_NNW lt 0 50 i
12. lgorithm Virtual Driver Scorpion Robot Hardware Scorpion Robot Model Figure 1 The different components making up the Player Framework At the top of the figure are different types of Player clients which besides robot control programs can be one of the many Player utility programs They all connect to the Player server which then takes care of providing access to the underlying hardware simulator or algorithm implementation All access is done via drivers 1 2 A Brief Overview of Player Stage Before continuing you should know the basics of what components make up the Player Framework and how it works As noted above Player uses a client server architecture where the Player server takes care of virtualizing access to various robot devices by pro viding a set of generic interfaces A wide range of different interfaces are defined such as an interface for controlling motors By using generic interfaces the same robot control pro gram can be used to control two widely different robots with little or no changes as long as the driver for the robots devices provide the interfaces required by the program More importantly the use of generic interfaces makes it possible to simulate these devices The configuration file given to the Player server program tells it which drivers to load The Stage 2D simulator can be thought of as just a basic driver providing simulated devices Figure 1 illustrates the relation between the components of the Playe
13. ndex irbump index irbump IsAnyBumped BumperProxy front robot front IsBumped index front index front IsAnyBumped Table 1 The interfaces supported by the ERSP Player driver and Stage For each interface relevant feature sets are listed along with examples on how to use them The two rightwards columns tells if the feature set is supported by the driver and Stage Below is an example of accomplishing this It checks the front bumpers once every sec ond to see if something is blocking the path of the robot If the path is clear the robot is moved forward else it is stopped include lt libplayerc playerc h gt include lt scorpion h gt using namespace PlayerCc int main int argc char argv PlayerClient robot localhost Position2dProxy position amp robot BumperProxy bumper amp robot robot SetDataMode PLAYER DATAMODE PULL robot SetReplaceRule 1 1 PLAYER MSGTYPE_DATA 1 1 while true robot Read if bumper IsAnyBumped position SetSpeed 0 0 0 sleep 1 else position SetSpeed 0 10 0 23 24 25 26 27 1 9 The Player Toolbox 1 USER MANUAL return 0 The calls to the robot object s SetDataMode and SetReplaceRule methods configures the client so that similar data messages are replaced with the newest version Compile it using cu O bump stop pkg config c leos libs playere Idriver include t
14. orkaround this problem is to probe interfaces inside a t ry catch construct and in the rest of the program only conditionally access the proxy objects in question See some of the programs in the test directory of the source package for examples on how to accomplish this 1 8 Advanced Sensor Usage As mentioned above sensors readings must periodically be processed This can be a prob lem if you are going to use sleep or do a lot of heavy computations in the robot control program since the buffer will quickly fill up This results in new readings being dropped and old stale sensor values being reported by the devices To avoid this problem you should set up the client to filter message and only use the most recent sensor values 8 o oo NoU BAe wo Nn Be NNN o PRB COR Bee PHB N e O OD WON DTD HO fF WOW NY YF CO 1 USER MANUAL 1 8 Advanced Sensor Usage Example usage Driver Drive position2d Motor commands Odometry Power enable disable IR range ir Range data Pose data IR bumper bumper Bump data Front bumper bumper Bump data Position2DProxy pp robot pp SetSpeed speed angle pp SetCarlike speed angle pp Goto x y yax pp GetXPos pp GetYPos pp GetYaw pp SetOdometry pp ResetOdometry IrProxy ir robot ir GetCount ir GetRange index ir index ir RequestGeom ir GetPoseCount ir GetPose BumperProxy irbump robot irbump IsBumped i
15. r SCORPION_IR_BN_N lt 0 50 ir SCORPION_IR_TE_NNE lt 0 50 position SetSpeed 0 0 0 5 continue As can be seen the IR device provides access to its readings as if it was an array The somewhat cryptic names of the array indices are defined in the scorpion h header file and can optionally be used to refer to the individual sensors The names are derived from the sensor names used in the resource configuration file for the Scorpion robots Finally when no obstacles are found move the robot forward position SetSpeed 0 10 0 0 return 0 You can find the above example in the test ir avoid cc file in the source package Compile it using 1See the resource config xml file which is typically found in the local installed Evolution Robotics doc umentation eg opt evolution robotics config on DIKUs robot laptop computers 1 6 Running on the Physical Robots 1 USER MANUAL a Char 9 li awoie ake comnie et lease lilos pileren Tdriver ine lude Rosa atea ode e 1 6 Running on the Physical Robots Until now you have only run the example programs on the Scorpion robot modeled in the Stage simulator Before continuing introducing more examples you should try to run the previous examples on the physical robots First shutdown any currently running Player servers and simulators o make stop Then bring up a new Player server this time using the configuration file for the physical Scorpion
16. r Framework In the Player system robot control programs act as clients connecting to the Player server on startup It then subscribe to devices via the interfaces provided by the server after which it enters the basic feedback loop of reading and processing sensor input followed by con trolling actuators like the motors To summarize the basic flow of a robot control is the following e Establish connection to Player server s e Subscribe to device s e Read sensory data from device s e Processing e Command robot motors 1 3 The Scorpion Robots 1 USER MANUAL Figure 2 The IR range sensors in Stage The Scorpion robots IR range sensors as modelled in Stage 1 3 The Scorpion Robots The robots that you will be programming are equipped with the following features 2 contact bumpers are as the name suggests situated on the front of the robot to protect it from collisions There are two sensors one on each side 7 vertical bumpers are short range digital IR sensors 4 are used for ledge detection to avoid hazardous falls or to detect if the robot has been lifted up from the floor and the re maining 3 up facing sensor for overhang detection to avoid camera damage As the sensors are digital they only sense if obstacles are within range or not They all trigger on distances from 1 cm 24 cm 13 analog IR range sensors are placed all around the robot with horizontal facing as de picted in Figure 2 They
17. robot make player scorpion cfg Running the robot control programs on the real robots is the same procedure as with the simulator There is no need to recompile any of them 1 7 Supported Interfaces One of the benefits of using the Player system is to able to quickly prototype and test an initial version of a robot control program in the simulator and then seamlessly move the program to run on the physical robot with little or no modifications Since Player Stage is a work in progress this is not entirely the case Consequently before starting to write you own program you should first find out what Player interfaces are provided by the robot for which you want to program be it a simulated or real world physical robot and which interfaces you want to use in your program Stage as of version 2 0 1 lacks support for simulating certain Player interfaces it might therefore be necessary to take this into account by conditionally using interfaces only available on the physical robot A summary of the supported interfaces is available in Table 1 As can be seen there are several differences between the interfaces provided by Stage and those provided by the ERSP Player driver The basic difference is that all bumper sensors dedicated to hazard avoidance are missing in Stage For more advanced robot control programs the incompatibilities can become a problem hindering easy switching between running in Stage and on the physical robots One way to w
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