Home

PR2 Manual - Clearpath Robotics

1. Keep the PR2 away from open flames and other heat sources The PR2 covers may burn if ignited Never use the PR2 around stoves or ovens Always be prepared for a fire and have a fire extinguisher close by and ready to use An ignition source could come from anywhere including an internal failure of the PR2 system e Other Environmental Specs UV exposure should be minimized UV radiation can damage the PR2 s skin Dust and dirt can clog air filters Forces and torques 8 2 Forces and Torques Joint position velocity and force limits are implemented in the PR2 s URDF file in the etc ros distro urdf robot xml file on the PR2 These joint limits control the range of travel of the mechanism the allowable velocity to prevent over travel These limits are enforced by pr2 controller manager and are designed to prevent poorly commanded control efforts from damaging the PR2 and harming operators The limits below are from the PR2 URDF file If a velocity or torque limit is not specified no value is enforced by pr2 controller manager Joint Velocity rad s or m s Torque Nm or N caster rotation joint caster wheel joint torso lift joint 0 013 10000 laser tilt joint 10 00 0 65 head pan joint 6 00 2 65 head tilt joint 5 00 15 00 shoulder pan joint 2 10 30 00 shoulder lift joint 2 10 30 00 upper arm roll joint 3 27 30 00 elbow flex joint 3 30 30 00 forearm roll joint 3 60 30 00 wr
2. To use a driver users must explicitly mount dev removable to use it and should umount dev removable when done Until the drive is unmounted there is not guarantee that the data has been written to the disk and if the robot runs out of batteries data may be lost 13 7 1 Formatting Drives To partition reformat one of the removable drives or the the internal drive on c2 use the format disk helper utility Simply pass it the name of the drive that is to be formatted for example sudo formatdisk dev sda or sudo formatdisk dev removable 13 7 2 Drive Maintenance If a drive is having problems run a selftest using smartmontools sudo smartctl t short dev sda After a few minutes check the results sudo smartctl 1 selftest dev sda START OF READ SMART DATA SECTION SMART Self test log structure revision number 1 Num Test_Description Status Remaining LifeTime hours 1 Short offline Completed without error 00 4195 2 Short offline Completed without error 00 3713 In the event that there are reported bad sectors http smartmontools sourceforge net provides information on freeing the bad blocks CHAPTER 18 COMPUTER CONFIGURATION 45 13 8 Default User Account The default account on the robot is pr2admin When the robot is first installed it does not have a password set however this password is set as part of the branding process When the PR2 is first received from Willo
3. coders mounted in the drivetrain after the major sources of potential backlash gears The laser tilt axis is driven directly by the motor through the encoder and then via a belt drive The head pan and tilt are both driven from the motor through a gear set planetary gear head for the tilt joint and external spur gears for the pan joint The encoder is mounted on the shaft after the gear set and then a belt drive is used for the final stage reduction These drivetrains are all high efficiency and capable of very high velocities The software velocity and position limits on these joints are important to prevent hard collisions with the joint stops which will cause damage to the hardware especially to the sensors If the mass of the head changes significantly the pan and tilt link gains may need to be re tuned 6 4 Counterbalance Although not an actuated drivetrain the arm counterbalance is one of the more compli cated mechanisms on the PR2 Inside of the shoulder turret there are two springs These springs are attached to belts which run over cams and provide a uniform downward force In the upper arm there is a four bar linkage which transmits the torque through to the shoulder lift joint upper arm roll joint and elbow flex joint As the arm moves through its configuration space the linkage changes the amount of leverage with which the counterbalance is pulling which compensates for the effect of the mass of the arm in different configu
4. 22 24 24 25 25 26 27 28 29 29 29 29 30 31 31 32 32 33 33 34 34 34 36 36 37 39 39 39 39 40 CONTENTS PRE AMI ERES REM EE REDE ESTAD RE 1323 Networking spread bei ad EE 13 2 1 Jaunty Networking gt lt o ek sac EERE so EES OK EEL OE 13 2 2 Lucid Networking lt e cca s ateoa ea Ea a o NFS Umini gi oe aad ES E PE E RE a a Ra ES DO ose sarta rs eee eee R RAE E SE eS 13 5 Home Directories cocos eras rr e IA ln a EEE O E e yl LE PIN 1o m1 Pomme DEVES es coa e pp ew A 14 72 Drive Maintensnce o ro ses ga NE AQE Re ee A A 13 8 Default User Account s sorae b eek aaa E E E 13 9 Creatine User ctommis si co 66464 oc esmas e a e RIIIE 13 11Backing Up and Restoring Users eae 13 12Clock Synchronization occ PRE aa ES 13 13Configuring the System ROS Installation 13 13 1 Switching ROS Distributions Example ML RM AAA A essas De SP ES Gee ee E E E LE ES 14 Basestation Setup and Pairing 14 1 Requirements 14 1 1 Naming 14 1 2 IP Address Configuration 2 2 2 000 14 1 3 Examples 14 2 Plugging Things In 14 3 Configure the Basestation Network o o 14 3 1 Configuring IPs 1432 Conhenrie Tesi oscar awe ea ee eee ee 14 3 3 Applying Settings 14 4 Configure the Robot Wifi 14 5 Initialize the Basestation VPN Server 004 14 6 Pairing w
5. 3 Drivetrains ao secan cun ena ea waaa enaa adka 6 4 Counterbalance oo e corsas iesaki eag a Guo Drivetrains o ss fose sic snes E e a a ee E Gb Drivetrain oo eea rrean a RR a a a ER OT JOVIVEURAI ss de o aa al ld 7 Motion Control TL Motor Controller Boards es sdo dhe ida a o ea DES T2 Realtime LOOP sec d s nlia A A A e io Controler Manager os sso sad sa elea SEG aa E Qd es 8 Mechanical Specification o Don s se ee e VALTER pre e DE e Sk e 8 2 Forces and Torques isis a ARA 8 3 Joint Limits and TYPE pr eeki t ee rei ARA 8 4 Modifying Joint Lime e o soe soend seso s hooo a 9 Sensor Overview UL Bre LG ss spa pp Y A EO SR A RO KS A Pe Titing LAO eos sanet so gs PESA ba Ba E RA o ad Cat rms do Sa rd RA ai a aa A Ro Gripper DM cs ao ek ae bed dna SARE RES e RAR GERE Us Inertial Measurement Unit gt a s ce ce ssie E EWR SEERA ERS A aco e ameo tam be sas Pine BG DE RE porh e REG 10 Power System A A 11 Computer Overview LETS OO sua tas sure Sa ar e E E TE Compar RO saga a PIE A A A A RR AIN 11 4 Default Password Reference o eee 12 Networking 12 1 Network CM ancestrais ow ROE SER RR DEN DS MRE 122 Network Espa lt s soe doa Gwe aKa WERE EER Ce hee a EE LES Service PO ea i Ga awe k dee eke we AREAS EEE A Ra a ee oe He eS A Ge ee ee a 12 5 Wireless Access Po o co c couma roae a Re ee ES 12 0 Wireless Router ios rasa e a we Se we we 13 Computer Configuration 19 19 20 20 20 21 21 21 22
6. 475 9794 CHAPTER What s in the Box The PR2 ships in 2 packages e Robot Crate Large wooden crate which contains the PR2 accessory kit base station computer and toolkit e Calibration Target Large checkerboard for accurate calibration of stereo cameras 3 1 The PR2 The PR2 is a robotics research and development platform that allows innovation right out of the box Please watch the video Unpacking the PR2 The video covers un packing the PR2 and turning on the PR2 while in the crate s base The video can be found in the tutorials of the PR2 s support website 3 2 The PR2 Accessory Kit The PR2 accessory kit includes tools and cables for teleoperating powering and cali brating the robot Additionally the sensor fingertips are stored in the accessory kit Figure 3 1 The PR2 accessory kit CHAPTER 8 WHAT S IN THE BOX 10 e Wireless Joystick The PR2 ships with a bluetooth joystick for teleoperating the robot The bluetooth joystick is a Sony DUALSHOCKS Figure 3 2 wireless controller It can be charged using any standard USB A to mini B USB cable one is in cluded in the accessory kit For more information see the ps3joy or pr2_teleop package at ros org Figure 3 2 The PR2 bluetooth joystick e Wireless run stop The PR2 comes with an OMNEX T50 wireless run stop transmitter When the red button is pressed or the unit is out of range the wireless run stop transmitter will halt the mot
7. Hwaddr 00 30 1b 48 c8 f8 inet addr 192 168 1 100 Bcast 192 168 1 255 Mask 255 255 255 inet6 addr fe80 230 1bff fe48 c8f8 64 Scope Link UP BROADCAST RUNNING MULTICAST MTU 1500 Metric 1 RX packets 2702 errors 0 dropped 0 overruns 0 frame 0 TX packets 2709 errors 0 dropped 0 overruns 0 carrier 0 collisions 0 txqueuelen 1000 RX bytes 129699 129 6 KB TX bytes 218528 218 5 KB Interrupt 17 In this case the address is 192 168 1 100 To actually brand the PR2 first plug the basestation into the service port of the PR2 and then use the robot brand command For example if the Pr2 would be named CHAPTER 14 BASESTATION SETUP AND PAIRING 54 prx cl would be named prx1 c2 would be named prx2 and if wanting to use the default 10 68 1 0 192 168 1 100 run sudo robot brand prx prx1 prx2 10 68 1 0 During the branding process it may prompt for the password of root c1 By default this will be willow Additionally a prompt may occur to choose a password for the pr2admin account When branding a Lucid robot you will additionally be asked to confirm multiple steps of the branding process Unless you have reason not to you should select y at each prompt When the script finishes a user should be able to connect to the robot over the VPN Check that it works and then exit ssh pr2admin 10 68 1 1 exit 14 7 Forwarding IPs to the robot To make contacting the robot from the building network more conveni
8. basestation For example prbase1 and edit etc hosts to resolve the basestation locally After modifying etc hosts it should look something like 127 0 0 1 localhost 127 0 1 1 prbasel willowgarage com prbasel 10 68 255 1 prbasel willowgarage com prbasel 10 68 0 11 cil 10 68 0 2 c2 The following lines are desirable for Ipv6 capable hosts al localhost ip6 localhost ip6 loopback fe00 0 ip6 localnet ff00 0 ip6 mastprefix ff02 1 ip6 allnodes ff02 2 ip6 allrouters ff02 3 ip6 allhosts Finally set the hostname using the hostname command for example sudo hostname prbasel CHAPTER 14 BASESTATION SETUP AND PAIRING 52 14 3 3 Applying Settings Once the network is reconfigured reboot the basestation to make sure the network comes back up correctly At this point the user be connected to the local network and be able to ping any machine that the user may want to access the robot from 14 4 Configure the Robot Wifi The Linksys wrt610n on the robot is located at the IP address 10 68 0 5 To configure it either plug a laptop or a basestation into the robot service port open a web browser and a go to http 10 68 0 5 Click on the Wireless tab The default login should be root and willow although after a factory reset the router may end up with login root and admin Set either Wireless Physical Interface wl0 for 2 5 Ghz or Wireless Physical Interface wll for 5 Ghz to
9. is a very good reason to use DHCP and it is understood how to configure the DHCP server to obey client id based requests 14 3 1 Configuring IPs Static IP To configure the basestation with a static IP edit the file etc network interfaces and change wan0 to use a static IP address for example iface wan0 inet static address 192 168 1 100 netmask 255 255 255 0 gateway 192 168 1 1 post up robot forward start pre down robot forward stop Update etc resolv conf to contain the appropriate name server e g CHAPTER 14 BASESTATION SETUP AND PAIRING 5l domain school edu search school edu nameserver 192 168 1 1 DHCP if using DHCP make sure that the DHCP server respects the client id specification and is configured to assign a consistent IP address to the client id of the basestation NOTE mac address based assignment of IPs on behalf of the robot The default client id for the basestation is basestation If this needs to be changed to a different client id edit the file etc dhcp3 dhclient conf and change the relevant line for example send dhcp client identifier prbase1 14 3 2 Configuring Hostname It is very likely that the hostname of the basestation will need to change Leaving it as basestation is ok but to make sure the DNS server correctly resolves this name to the IP address that has been assigned to the basestation To change the hostname edith the files etc hostname to just contain the name of the
10. monitors for various types of problems the PR2 could experi ence NOTE When using the robot command to start the PR2 the user s current ROS PACKAGE PATH will be used for the default path robot start 18 9 PR2 Dashboard When running the PR2 the pr2_dashboard should always be up on the screen This is how the robot software will announce if something is going wrong and is also how the motors and power turn on and off On a computer with a built ROS installation e g the basestation desktop computer that ships with the PR2 not on the PR2 itself set the ROS MASTER URI to point at the master running on the PR2 and launch the dashboard by typing export ROS MASTER URI http pr lt x gt 1 11311 rosrun pr2 dashboard pr2 dashboard The pr2 dashboard control panel a graphical user interface should appear and pro vide information about the state of the PR2 It is ok if not all of the icons are green In fact the run stops should be warning that the wireless run stop is not on Take a moment to review the state of the PR2 A sense can be obtained for the health of the PR2 by looking at the diagnostics information click on the wrench on the far left Since the run stop is in the stop position the motors will be giving a warning because the robot was just turned on and the encoders on the joints have not been calibrated yet If warnings or errors are seen in any other sections read the error messages and try to figure out wha
11. own screen mouse and keyboard A laptop with wireless access is ideal e Linux Familiarity with the Linux command line is strongly recommended The com puters in the base of the PR2 as well as the base station computer run Ubuntu Linux Since the computers in the robot do not have attached dis plays all tasks on them have to be performed by logging in remotely e g via ssh e Electrical The PR2 charges using a standard 120V or 220 VAC power outlet The robot can draw 15A of current when plugged in so it is strongly recommend to recharge the PR2 only on outlets with no other devices on the same circuit breaker e ROS All of the PR2 software is based on ROS Completing the beginner tutorials available at ros org will help PR2 users understand the structure of the soft ware on the robot and will give PR2 users the tools to understand the flow of data in the system e PR2 Support Please visit the PR2 support web page at pr2support willowgarage com to review beginner tutorials service information modularity specification safety information and to submit a ticket or report a safety incident CHAPTER Safety Safety is a key goal at Willow Garage Safety is important yet challenging and it is a continual process shared by the robot designer user and administrator The following chapter provides an overview of the issues describes some safety related design features enumerates a set of basic usage gui
12. sudo rm distro pr2admin0pri0XX etc ros sudo ln s cturtle distro pr2admin0pri0XX etc ros ls 1 distro lrwxrwxrwx 1 root root 7 2010 11 12 10 19 distro gt cturtle 13 14 Log Files The PR2 is configured to consolidate all system logs into var log messages CHAPTER 18 COMPUTER CONFIGURATION 48 13 15 Udev A number of custom udev rules have been provided to help give sensors more meaningful names These are all stored in etc udev rules d 71 pri network interface rules is responsible for renaming the network interfaces and lan0 lan4 wan0 and ecatO consis tently based on mac address ranges 73 pr aliases rules makes convenient aliases for the hokuyos imu batteries and joystick All of these aliases end up in dev sensors Finally 74 pr disk rules is responsible for ensuring that the removable drive always just shows up as dev removable It is important to note that the creation of these udev rules depends on a functioning ROS system If the ROS configuration from etc ros is non functional udev will not be able to talk to the hokuyos to create appropriate symlinks In the future there may be more sensors that depend on ROS for this initial configuration as well CHAPTER Basestation Setup and Pairing Before using the PR2 and basestation it needs to be configured This configuration can be done by logging into the basestation The default account is pr2admin with password willow The following instructions ass
13. the dashboard should be reading OK If this calibration step fails then use the pr2 dashboard to diagnose the problems with the PR2 See the PR2 administrator if assistance is needed in understanding and addressing the issues 18 11 Tucking PR2 Arms Before driving the PR2 around it is best to tuck the PR2 s arms If the PR2 s arms are not tucked in before driving then the arms are likely to swing around while the PR2 is moving To run the tuckarm package type into the PR2 s computer prx1 rosrun pr2_tuckarm tuckarm py b This will tuck both PR2 arms The feedback from tuckarm should display something like this INFO 1264099125 710039 Waiting for controller manager to start INFO 1264099125 718283 Tucking both left and right arm For more information about how to drive the robot around see the pr2 tuckarm package at ros org 18 12 Driving PR2 with a Joystick To move the PR2 drive it around with the joystick Tod o this open a new terminal window with a new ssh connection to the robot and run the teleop joystick launch file ssh lt unsername gt pr lt x gt 1 roslaunch pr2_teleop teleop_joystick launch CHAPTER 18 RUNNING THE PR2 65 Be sure to check to see if the PR2 is plugged in e g ethernet cables or power cables If PR2 is plugged in be very cautious to avoid pulling the cables out improperly Once the teleop joystick mode is running press the pairing button in the middle of the joystick to pai
14. 168 head tilt joint revolute 60 30 r shoulder pan joint revolute 40 130 shoulder pan joint revolute 130 40 shoulder Jift joint revolute 80 30 r upper arm roll joint revolute 44 224 Lupper arm rolljoint revolute 224 44 elbow flex joint revolute 133 0 x forearm roll joint continuous wrist flex joint revolute 130 0 wrist roll joint continuous gripper joint prismatic 86 mm 0 mm CHAPTER 8 MECHANICAL SPECIFICATION 28 8 4 Modifying Joint Limits On the PR2 soft limits stop the joints from reaching the full range of motion to prevent damage to the mechanism These soft limits similar to a virtual spring are specified in the robot s URDF file For an explanation of their implementation see safety limits in the pr2 controller manager package The soft limits have been validated by Willow Garage and are required for safe operation of the PR2 Under no circumstances should these limits be increased without prior written authorization by Willow Garage Safety Unauthorized and unvalidated modification of these limits could cause mechanism damage and increase the risk of injury or death to PR2 operators Mechanism damage resulting from changing these limits can include e Thermal damage to motors from exceeding maximum current specifications e Damage to drive trains resulting from collision with end stops e Premature wear and damage to motor gear head or drive train resultin
15. 2 calibration package for more information Figure 3 7 Small calibration target 3 3 The PR2 Toolkit A toolkit is provided with the PR2 To avoid damaging the robot or personal injury while repairing the PR2 always use these tools and follow the Repair and Replacement procedures at pr2support willowgarage com when performing any hardware maintenance on the robot CHAPTER 8 WHAT S IN THE BOX 13 E a Figure 3 8 The PR2 Toolkit 3 4 Base Station Computer The base station computer ships without a monitor keyboard or mouse See Chapter 14 on computers for more information on how to configure the base station Figure 3 9 The PR2 base station computer 3 5 Large Calibration Target The large checkerboard calibration target which ships with the PR2 is 1 inch thick and approximately 3 feet square This is the recommended calibration target to use for calibrating the intrinsics of the stereo cameras on the robot The PR2 ships with stereo cameras already calibrated but re calibration may be needed after shipping and occasionally as vibration and thermal effects change the parameters over time The squares on the board are 108mm in each direction Since the flatness of the board is critical to the accuracy of the calibration please store this where it will not warp CHAPTER Mechanism Terminology The PR2 kinematics are talked about using the concepts of joints links frames actu ators and transmissions Each of thes
16. 68 0 100 10 68 0 199 Important addresses on this network e 10 68 0 1 cl lan0 e 10 68 0 2 c2 lan0 e 10 68 0 5 wifi router e 10 68 0 6 basestation lan0 e 10 68 0 91 cl esms e 10 68 0 92 c2 esms e 10 68 0 250 wap 36 CHAPTER 12 NETWORKING 37 10 69 0 0 24 Secondary Robot Internal Network The 10 69 0 0 network is a second internal subnet The cameras are given addresses on this subnet to partition traffic across the computer s two network interfaces of the computers This way heavy network utilization by the cameras is less likely to interfere with more critical computer functions such as NFS e 10 69 0 11 cl lanl e 10 69 0 12 c2 lanl 10 68 X 0 24 Robot VPN Network The primarily role of the basestation is to function as a VPN server for the robot Each robot can be given a unique VPN subnet to facilitate the operation of multiple robots using a single VPN server The basestation can be configured to automatically forward relevant traffic from the building network into the VPN network hiding this from the end user However if greater security is desired the basestation can instead be configured to require users to be assigned a VPN key to access the PR2 s VPN network Important addresses on this network e 10 68 X 1 cl tun0 e 10 68 X 2 c2 via cl tun0 e 10 68 255 1 basestation tun0 12 2 Network Explanation Figure 12 1 The PR2 network diagram The above figure depicts t
17. A150 digital triaxal accelerometer The measurement range 2g 4g or 8g and bandwidth 25Hz 1500Hz of the accelerometer can be selected in software For more informa tion see the ethercat_hardware package at ros org Fingertip Pressure Sensors The default fingertips of the PR2 are sturdy aluminum blocks with non slip rubber covers for added friction and compliance is grasping However the aluminum tips can be swapped out for an included set of RoboTouch tactile sensing pads made by Pressure Profile Systems each with 22 tactile sensing elements fifteen in a 5x3 array on the front surface two on top two on each side and one in back near the top Each tactile element has a pressure range of 0 30 psi 0 205 kPa and sensitivity of 0 1 psi 0 7 kPa The sensors connect to the robot via an SPI ribbon cable and two screws and have a maximum scan rate of 35 Hz The tactile sensors are highly fragile when not protected by the rubber covering and so care should be taken not to damage the rubber covering For more information see the fingertips_pressure package at ros org CHAPTER 9 SENSOR OVERVIEW 31 e Calibration LED 9 5 Inertial Measurement Unit The PR2 has an inertial measurement unit IMU located next to the tilting laser The IMU is a MicroStrain Inertial Link 3DM GX2 which has an accelerometer range or 5g and a gyro range of 300 degrees s For more information see the microstrain 3dmgx2 imu package at ros org 9 6 Spe
18. ETUP AND PAIRING 55 forward is provided which takes care of setting this up automatically To set this up edit the file etc robot forward conf and add the lines lt C1_NAME gt lt VPN_SUBNET gt 1 lt ROBOT_IP1 gt lt C2_NAME gt lt VPN_SUBNET gt 2 lt ROBOT_IP2 gt For example in this case prxi 10 68 1 1 192 168 1 101 prx2 10 68 1 2 192 168 1 102 Note that for this to work properly the PR2 computers should have been named prxl and prx2 respectively and furthermore the DNS server should resolve prx1 to 192 168 1 101 and prx2 to 192 168 1 102 Much like the basestation these IPs can be assigned via DHCP prxi 10 68 1 1 dhcp prx2 10 68 1 2 dhcp In which case the basestation will use the client id s prx1 and prx2 to acquire 2 IP addresses from the DHCP server These IPs should be assigned consistently given the client id s and should match the IPs that the DNS server returns for the particular hostnames Robot forwarding is enabled whenever the network starts but to manually start forwarding run sudo robot forward start The user should now be able to contact the robot at the given IP address and if they DNS server is set up properly using its hostname For example ssh par2admin 192 168 1 101 and sudo robot forward stop At this point the basestation should be configured to work on the network CHAPTER Reinstalling the Basestation With a basestation USB installer the ba
19. LAN and allows direct access to the Robot Internal Network The WAP can be configured by plugging into the PR2 s service port and going to the IP address 10 68 0 250 The default login and password are root and willow respectively 12 6 Wireless Router The PR2 has a Linksys WRT610N dual N band wireless router This router can be con figured to connect to the building wireless network In the absence of a WAN connection the robot will attempt to contact the basestation through this wireless router instead The wireless router can be configured by plugging into the robot service port and going to the IP address 10 68 0 5 The default login and password are root and willow respectively CHAPTER Computer Configuration The operating system running on the PR2 computers is an extended version of Ubuntu 9 04 Jaunty Jackalope or 10 04 Lucid Lynx It depends on a number of additional packages for system configuration but should otherwise be familiar for Ubuntu users If there is a computer problem not covered by the PR2 documentation the Ubuntu Documentation is the next place to look 13 1 BIOS The BIOS configuration is slightly different between cl and c2 to allow them to boot differently cl defaults to booting off of the internal disk while c2 defaults to netbooting off the lan0 interface Early in the boot process cl is reconfigured to try netbooting off of the the lanl interface before booting off the dis
20. NETWORKING 39 static IP of the basestation resolves properly and is allowed through the firewall on port 1194 Regardless of how the robot is connected to the basestation a desktop situated on the building network will always talk to the robot in the same way Traffic from the desktop depicted in green is actually routed through the basestation and into the VPN tunnel Once in the tunnel which pathway the robot is using is abstracted and the traffic seamlessly emerges from the other side of the tunnel 12 3 Service Port The PR2 service port is the bottom ethernet port on the back panel of the robot It connects directly to the PR2 internal network allowing a connection to the computers directly DO NOT PLUG THIS PORT INTO THE BUILDING NETWORK cl serves DHCP for this network and if it conflicts with another DHCP server this will most likely cause problems both on the building network and on the PR2 network depending on which DHCP server takes precedence 12 4 WAN Port The PR2 WAN port is the top ethernet port on the back panel of the PR2 This connects directly to wan0 on cl This port is intended to be plugged into the building network The robot will attempt to acquire an IP address via DHCP and then attempt to contact the basestation at a known IP address 12 5 Wireless Access Point The PR2 comes configured with a cradle point ctr350 configured as a Wireless Access Point WAP The ESSID of this network defaults to ROBOTNAME_
21. PR2 User Manual Willow Garage October 5 2012 Contents Contents 2 1 Manual Overview 1 11 eq e ie ee ewe oR ewe eS OO A GS DS 1 2 Safety 3 21 Salety LM css eee he SEER SG Be OEE RE OSG EE OR 3 2 2 Desien Features o o a saoi rh ek EEE do SAE EE ER RT 3 2 3 General Usage Guidelines eee ee ee 4 24A By Programi cia e dp E E RE ERE SESE RE EEE RA 7 3 What s in the Box 9 ad ME us rosas rs A A ee EA ra RAS 9 32 The PRZ Acer 6k wk a a a ES 9 dl The FRA Toolkit oscar dara dd Ba gs STA 12 da Base Station Compter lt a sedrer saias dA ee 13 3 9 Large Calibration Del spas sds RA dE Bie RG 13 4 Mechanism Terminology 14 AL DI 2c dw 64 REA dedo Rd a A A DE 14 e DEM S iio pe E e e A A A 14 La JOT e ra Ae AR da OES OS io ae A 14 AA ALIS o ica bos Bde ta de RA Sb RA SESE de pg 15 45 Transmission III 15 40 PR2 Home Fose esa corea d OE mp E RE ER O Ree RA 15 47 PR2 Coordinate System 4 oo se ccrten esa aaa a da a a a 15 4 8 Naming Conventions 2 a aooaa eee ee eee Bee 16 5 Links and Joints 17 AQ cererea TO TE aeta d adad een 17 o Base Body Spine 122 as ow taine Eras drama es 17 DO Head risadas OG SO Oe OE DEBE dE Kin iona 17 Wa ATMS e ee ee n ee pos Ee dae eek e e 18 dm MR e e ate AA SEL EA EEE E 18 ao Additional Information ss 6544644 dee eb E eR ED EO 18 CONTENTS 6 Drivetrain Overview 6 1 Drivetrains ea dos e ea toea edo new a Ee AE E EAR a we E 6 2 Drivetrain a am pn O ek E RO EE BA LE a a ES E 6
22. Y 15 pr2 description package The PR2 has mostly rotational joints but the torso is transla tional and there are also a number of fixed joints used to represent the notion that two links are part of the same rigid body Rotational and translational joints are generally represented in the same way in the system and are referred to as joint effort instead of force or torque as well as using position and velocity to represent both linear and angular movement 4 4 Actuator The motor encoder units in the PR2 are explicitly modeled as actuators The actuator model treats them as torque sources with position measurement The details of the actuator model e g the motor torque constant or max current as well as the names of actuators are stored on the motor controller boards See the pr2_ethercat package 4 5 Transmission Transmissions also defined in the URDF robot description are used to represent the mapping between actuators and joints They map actuator position into joint position meters or radians and map from commanded joint efforts torques or forces to actuator efforts In most cases in the robot this is a linear mapping between one joint and one actuator that just defines a reduction but the wrist has two motors controlling two joints in a cross coupled manner and the gripper the mapping from motor rotation to gripper position is non linear 4 6 PR2 Home Pose In order to describe the PR2 robot pose
23. age Guidelines While many guidelines for the safe use of a robot stem from common sense a basic set is listed here It is fundamental to follow these guidelines but note that these guidelines alone do not guarantee safety only reduce risk e Every organization that uses a PR2 must appoint a Safety Officer The Safety Officer s contact information should be known by everyone who uses the PR2 including designers developers programmers and end users Details of the Safety Officer s roles and responsibilities are described in section 2 4 e Before operating or working with the PR2 every user must View the safety video Read this user manual in particular the entirety of Chapter 2 on Safety Read and understand the latest list of potential hazards which can be found at safety willowgarage com Know how to contact the organization s Safety Officer e Supervise children visitors and anyone who has not followed the previous guideline In particular make sure they Do not come within range of the PR2 when active Are aware that the robot could move unexpectedly and is potentially danger ous CHAPTER 2 SAFETY 5 Are not alone with the PR2 Do not operate the PR2 e Maintain a safe environment Safety is not only affected by how a PR2 user operates the robot but by the environment as well The PR2 is designed to operate in a laboratory environment Keep the robot at least 7 meters from the
24. aker The PR2 has one Logitech V20 notebook speaker located under the pan tilt head next to the tilting laser For more information see the sound play package at ros org CHAPTER 10 Power System Place holder for the power system 10 1 Subsection 32 CHAPTER Computer Overview PR2 has two computers each has 24 Gb of RAM 2 quad core Nehalem processors and both a 2 5 inch internal hard drive and an externally removable 3 5 inch drive Additionally the PR2 ships with a basestation computer which facilitates seamless communication with the PR2 when transitioning between wired and wireless networks and additionally helps in a number of maintenance tasks 11 1 Computer 1 cl Computer 1 c1 is physically located on the right side of the robot It is referred to as the master computer because it serves a number of key roles for the computer infrastructure e cl stores the operating system of both computers C2 cannot boot unless cl has booted first e cl is connected to the PR2 ethercat network and is the only computer that can perform motor control e cl provides routing for the rest of the robot when it is plugged in via the WAN port e cl provides routing for the rest of the robot when connected to another network via an open VPN tunnel cl s PCI slot is used for a 4 port ethernet card giving it a total of 6 ethernet ports These are e lan0 lan3 connection to internal robot network e wan0 connected directly t
25. an be found in the pr2 ethercat package At runtime the node is called the realtime loop This process uses the RT PREEMPT extensions to the Linux kernel to run as a hard realtime process with a cycle time of 1ms and performs both controller update computations and communication over EtherCAT with the MCBs Non real time threads within the same process are used to communicate over ROS to publish diagnostics configure controllers and otherwise control the behavior of the PR2 s motion control system 7 3 Controller Manager Within the realtime loop the controller update is dealt with by a ROS component which contains both realtime and non realtime functionality called the controller manager see the pr2_controller_manager for more information Controller manager has an update step which is called by the realtime loop at 1khz which receives measured motor torques and positions and sends desired motor torques for the next cycle The controller manager includes the joint limit safety code that enforces position velocity and torque limits which are necessary to keep the PR2 from damaging its hard ware In addition it has a dynamic plugin loading mechanism that allows shared libraries containing realtime controllers to be loaded and executed inside the 1kHz realtime loop CHAPTER Mechanical Specification Do not operate the PR2 before reviewing the mechanical specifications listed below Please contact Willow Garage Support at safety Qwillowga
26. and ip rule ip rule O from all lookup local 1000 from all to 10 68 0 0 24 look up main 1001 from all to 10 0 2 239 look up main 1002 from all to 10 68 1 0 24 look up main 2000 from all look up VPN 3000 from all blackhole 32766 from all lookup main 32767 from all loookup default The two important rules are priority 2000 and 3000 The priority 2000 rule routes all traffic into the VPN routing table ip route list table VPN default via 10 68 1 6 dev tun0 metric 1 The priority 3000 rule is what sends things to the blackhole By disabling the priority 3000 rule traffic which cannot be routed through the basestation such as when the VPN tunnel is down will simply go to the main routing table To remove the priority 3000 rule run sudo ip rule del priority 3000 This may be especially helpful when repairing a system in a particularly bad state since otherwise the necessary software updates or necessary configuration files may not be fetched for downloading 13 2 2 Lucid Networking The Lucid networking functions similarly to the Jaunty networking but is controlled much more dynamically by the tool multi_interface_roam Rather than removing ip rules manually multi_interface_roam can simply be stopped to put the robot in a nominal non roaming state You should only do this if logged in via the service port since otherwise you will lose your connection sudo etc init d multi_interface_roam stop One source of
27. and joint positions in a consistent manner a home pose of the robot has been defined At the home pose all joint angles are considered to be at zero In the home pose the casters are facing straight ahead the arms are straight out in front of the robot the grippers are closed the tilting laser is level and the head is centered and level For most joints the calibration reference point is not at the home pose or zero position The URDF of the PR2 contains the offsets between the flag positions and the home positions of the joints 4 7 PR2 Coordinate System The coordinate frames for all links of the PR2 are defined to aligned with a world coor dinate frame of positive z axis up positive x axis forward and positive y axis robot left when the PR2 is in the home pose All joint angle conventions are chosen so that from the home position positive motion of the joint causes positive motion around one of the positive axes of the world coordinate frame CHAPTER 4 MECHANISM TERMINOLOGY 16 4 8 Naming Conventions In general the names for a link and the associated frame will be similar e g r forearm link and r_forearm_frame and the names for an actuator a transmission and the associated joint will be similar e g r_elbow_flex_motor r_elbow_flex_trans and r_elbow_flex_joint For components such as arms and casters that are included in the robot in multiple locations a short prefix is used to indicate which location is referred hea
28. be used The self plug in cord has magnets on the side opposite the checkerboard which should be used to attach it to the magnetic pad on the base e Sensorized fingertips and boots The PR2 ships with sensorless fingertips attached Included in the accessory kit are fingertips which have an integrated 22 element pressure sensor Figure 3 6 These sensorized tips are easy to damage and are not as robust as the rest of the PR2 Five fingertip sensors are provided 2 for each gripper plus 1 spare as well as 20 rubber protective boots which prevent the sensor from CHAPTER 8 WHAT S IN THE BOX 12 coming into direct contact with the environment When using the fingertip sensors always have an undamaged boot in good condition installed over the sensor Continuing to use the fingertip sensors after the rubber boot is dam aged greatly increases the chance that the sensors themselves get damaged Replacement sensor tips will be available for purchase from Willow Garage See the support site at pr2support willowgarage com for more information Figure 3 6 Fingertip sensors and replacement boots e Small calibration target This small hand held calibration target which looks like a checkerboard is used for the PR2 self calibration The PR2 holds the checkerboard in one gripper and uses it to calibrate the arms the head the cameras and the tilting laser together The squares on the board are 25mm in each direction See the pr
29. ce from the local system administrator may be needed to allow traffic on this port 49 CHAPTER 14 BASESTATION SETUP AND PAIRING 50 Finally for the PR2 to be able to find the basestation both the wired and wireless networks must provide a DHCP server The operation of the system is that the PR2 will acquire an IP address that it is paired to Review the section on Networking for a more thorough overview 14 1 3 Examples In the remainder of the examples in this section it is assumed that the basestation has been given the hostname prbase1 and the computers will be named prx1 and prx4 It is assumed that the DNS resolves them correctly as follows prbasel 192 168 1 100 prx1 192 168 1 101 prx2 192 168 1 102 14 2 Plugging Things In Insert Image here Figure 4 2 No Name When plugging in the basestation make sure that WANO on the motherboard is plugged into the building network LANO on the PCI card is only intended to be plugged into the robot service port Additionally it is important to plug the DVI port into the installed graphics card on the right side of the computer and not the extra DVI port on the motherboard There is only one place to plug in the power and a keyboard mouse can be plugged into any of the available USB ports 14 3 Configure the Basestation Network There are two ways to set up the basestation using a static IP or DHCP Is it strongly recommended that a Static IP is used unless there
30. client mode and enter the SSID for the network To change other settings make sure that under Setup the WAN connection type is Automatic Configuration DHCP the local IP Address is 10 68 0 5 and the DHCP Server is Disabled When done make sure to select Apply Settings To test the setup of the wireless you can temporarily add a specific route on the basestation which will route a particular IP address through the wifi router and then try to access that ip address Once the routing entry is added and the IP address is reached the wifi router is connected properly For example to route requests to the Willow Garage website through the wifi router explicitly sudo ip route add 157 22 19 22 via 10 68 0 5 dev lan0 Then point the web browser to http 157 22 19 22 This should end at Willow Garage s home page via the wireless router If the building infrastructure wireless access point requires accepting an EULA this method will typically give an opportunity to accept it Once that is working remember to disable the route so that it works if the basestation is not plugged into the service port sudo ip route del 157 22 19 22 via 10 68 0 5 dev lan0 14 5 Initialize the Basestation VPN Server One of the primary functions of the basestation is to host a VPN server that the robot can connect to On Jaunty robots this configuration is in etc openvpn On Lucid robots this configuration is in etc wg openvpn The serv
31. d_tilt_link r_shoulder_lift_link r shoulder pan link head pan link r upper arm link Tupper am roll Tn 1 elbow flex link tilt laser mount link r forearm link 1 forearm roll link torso lift link base link Lwrist flex link 1 wrist roll link Tgripper palm link gripper finger link gripper r finger link gripper finger tip link gripper finger tip link Figure 4 1 The PR2 link naming scheme CHAPTER Links and Joints 5 1 Casters Each robot has four steered and driven casters one at each corner of the base The casters are referred to as front right fr front left 1_ back right br and back left b1 Each caster consists of a rotation joint caster rotation joint which rotates or steers the body of the caster called the caster rotation link around a vertical axis Attached to the body of the caster are two parallel driven wheels whose drive joints are caster r wheel joint and caster 1 wheel joint 5 2 Base Body Spine The four caster of the robot attach to the base link of the robot via the caster rotation joint Physically the base link of the robot includes the rear panel with electrical network con nections computers and battery system The torso of the robot is a prismatic joint described by the torso lift joint which moves the torso up and down relative to the base link The torso lift link wh
32. debug information related to multiinterface_roam is in the log file var log roam console output log It shows the 3 available interfaces and their CHAPTER 18 COMPUTER CONFIGURATION 42 respective quality metrics and which one is currently considered active 2011 02 24 21 58 52 147 INFO Thu 24 Feb 2011 21 58 52 147743 2011 02 24 21 58 52 173 INFO bsClani inf Wired 0 000 100 2011 02 24 21 58 52 173 INFO wan0 inf Wired 100 000 100 active 2011 02 24 21 58 52 174 INFO ddwrt inf Wired 99 998 100 2 133 NFS Unionfs The single largest difference between a normal Ubuntu installation and the PR2 config uration is that c2 mounts nearly its entire filesystem via NFS The exceptions to this are the directories etc var and pr2bin which are mounted via unionfs fuse In short union s allows one to specify an additional overlay on top of the underlying filesystem On a Jaunty robot the contents of this overlay can be found in the directory slave on cl On a Lucid robot the contents of the overlay can be found in the directory unionfs overlay on cl Files added here will show up in the appropriate location on c2 For more information on how this is set up see the main page for unionfs fuse and look at the init script etc unionfs fuse nfs root New software and configuration changes should only be made on cl Since c2 mounts most of its filesystems read only this will usually enforced automatically If using a non standard piece
33. delines to support safety and details the safety pro gram 2 1 Safety Overview Safety is a vitally important concern whenever anyone is around a PR2 It is a heavy piece of equipment with many moving parts The robot travels through the environment and can carry and manipulate a wide variety of objects Its movements and actions are not completely predictable The PR2 can cause significant damage if it falls on or runs over someone There are several ways it can pinch grab and twist fingers or other body parts The robot can wield dangerous implements and knock heavy objects over People must always be cautious and attentive when around a PR2 Managing safety is a challenge when dealing with any complex engineering system In the case of the PR2 consider also the open extensible programmable and experimental nature of the platform The PR2 s capabilities and behaviors change over time with user interactions and with reprogramming With this in mind Willow Garage has chosen a three fold approach First the PR2 is designed to minimize potential risks and maximize inherent safety Second all users receive communication about how to minimize risk And third an explicit safety program ensures that the community continues to identify potential hazards seek design mitigations and communicate effective usage guidelines 2 2 Design Features While retaining the power of an open platform both hardware and software are designed to minimize ris
34. e is defined and represented in code as well as having a unique name In general a single joint will have an actuator and a transmission and will connect two links together A link is a rigid body in the kinematic tree and will have a coordinate frame but not all frames are associated with links Fixed joints are allowed so some rigid bodies that could be considered one link are considered to be two links rigidly joined together This is done mostly at locations where there is a physical interface between components 4 1 Link A link is considered to be a rigid body within the robot It generally has geometry to define visual and collision space representations has inertial properties and has a name The links for the PR2 are defined in the URDF description that can be found in the pr2 description package 4 2 Frame Frames are geometric entities that represent coordinate frames in space Every link has an associated frame but frames are also used to represent other things such as the optical frame of a camera the origin of global map or the location of a detected object Frames are always defined relative to one another and relationships and transformations between them are tracked using the tf package 4 3 Joint A joint is considered to be part of the robot and define the relationship between links The joints for the PR2 are defined in the URDF description that can be found in the 14 CHAPTER 4 MECHANISM TERMINOLOG
35. eans that the gripper is unable to detect if it has mis calibrated on startup CHAPTER Motion Control PR2 motion control describes the electrical and mechanical hardware in combination with software to produce the desired joint effort position or velocity control Figure 7 1 shows the hardware and software layer interaction as well as the realtime and non realtime processes that occur in the motion control loop Software non realtime ROS messages Software realtime Controller Manager 1 kHz loop Software realtime Hardware EtherCAT Motor Controller Boards 100 kHz loop UONISO Figure 7 1 The PR2 motion control layout 7 1 Motor Controller Boards Each motor encoder on the PR2 has its dedicated Motor Controller Board MCB The MCB detects and counts transitions in the encoder signal measures the motor current and commands the voltage going to the motor Each MCB runs a PI control loop to 22 CHAPTER 7 MOTION CONTROL 23 control the motor current to a desired value by commanding the motor voltage This control loop is closed at 100kHz on an FPGA on the MCB A shared EtherCAT realtime Ethernet link with the first computer allows all MCBs in the PR2 to communicate with the main computers with deterministic timing Each MCB has the following inputs and outputs Encoder Input Each MCB can read quadrature incremental encoder input In proper opera tion this should never skip or drift Po
36. ed is the internal drive on cl There are 3 relevant partitions created during installation On a Jaunty robot these are physical partitions e cl dev sdal cl holds the root filesystem for the OS e cl dev sda5 cl home stores user home directories linked from u by way of pr 1 e cl dev sda6 cl hwlog stores hardware logs generated by the pr2 On a Lucid robot these are instead LVM partitions e cl dev vg00 root cl holds the root filesystem for the OS e cl dev vg00 home cl home stores user home directories linked from u by way of pr 1 e cl dev vg00 hwlog cl hwlog stores hardware logs generated by the pr2 The internal hard drive on c2 has a single partition which is generally used as extra user storage On Jaunty robot e c2 dev sdal c2 home stores user home directories linked from u by way of pr 2 On a Lucid robot e c2 dev vg00 home c2 home stores user home directories linked from u by way of pr 2 Finally both computers are configured to conveniently make use of the additional removable drives Any drive loaded into the removable bay should always show up as dev removable The mount point removable is set up to allow users to mount the first partition on this drive CHAPTER 18 COMPUTER CONFIGURATION 44 e dev removablel removable stores temporary data users may want to move off the robot primarily used for large bag files This is NOT mounted by default
37. ent the basestation can be configured to forward IP addresses assigned statically or via DHCP to the robot This is achieved through a combination of ip tables rules and additional ip addresses claimed by the basestation First the basestation should claim a couple extra IP addresses These are the IPs that will be used to contact the robot from the local network Eventually these IP addresses should show up in ifconfig for example wan0 prx1 Link encap Ethernet Hwaddr 00 30 1b 48 c8 f8 inet addr 192 168 1 101 Bcast 0 0 0 0 Mask 255 255 255 255 UP BROADCAST RUNNING MULTICAST MTU 1500 Metric 1 Interrupt 17 wan0 prx2 Link encap Ethernet Hwaddr 00 30 1b 48 c8 f8 inet addr 192 168 1 102 Bcast 0 0 0 0 Mask 255 255 255 255 UP BROADCAST RUNNING MULTICAST MTU 1500 Metric 1 Interrupt 17 Additionally ip tables should forward each of these IP addresses to the respective robot computer in the VPN In the IP tables viewable with iptables save A PREROUTING d 192 168 1 101 32 j DNAT to destination 10 68 1 1 A PREROUTING d 192 168 1 102 32 j DNAT to destination 10 68 1 2 A POSTROUTING s 10 68 1 1 32 j SNAT to source 192 168 1 101 A POSTROUTING s 10 68 1 2 32 j SNAT to source 192 168 1 2 A OUTPUT d 192 168 1 101 32 j DNAT to destination 10 68 1 1 A OUTPUT d 192 168 1 2 32 j DNAT to destination 10 68 1 2 Setting this up by hand is tedious and time consuming Instead a utility called robot CHAPTER 14 BASESTATION S
38. er needs an appropriate key To generate they key for the VPN server on Jaunty run CHAPTER 14 BASESTATION SETUP AND PAIRING 53 sudo etc openvpn gen_server_key on Lucid run sudo etc wg openvpn gen_server_key It will prompt for some information It is good practice to get the information correct but will not actually impact the performance of the robot 14 6 Pairing with the Robot Robot pairing is performed with the robot brand command on the basestation It takes 5 arguments sudo robot brand lt ROBOT NAME gt lt C1_NAME gt lt C2_NAME gt lt VPN_SUBNET gt lt BASESTATION_IP gt e ROBOT_NAME This is the name the PR2 will be given e C1NAME This is the intended hostname of cl The DNS server needs to resolve this to the IP address that is intended to be used for the PR2 e C2 NAME This is the intended hostname of c2 The DNS server needs to resolve this to the IP address that is intended to be used for the PR2 e VPN SUBNET Unless multiple PR2 s are being used 10 68 1 0 The 3rd field of the IP however can be any value other than 0 and 255 which are reserved for the robot local network and the basestation server respectively No two robots on the same basestation should be assigned the same VPN subnet e OPTIONAL Basestation IP By default this is taken from the IP assigned to wan0 It is worth checking that it is correct using the ifconfig command ifconfig wan0 wan0 link encap Ethernet
39. estart chrony again 13 13 Configuring the System ROS Installation The system ROS installation is managed by a set of configuration files in etc ros This configuration determines which distro is used which ROS processes are launched by default and contains the calibrated description of the robot URDF The default configuration files are provided by the package pr2 core Additionally there are pack CHAPTER 18 COMPUTER CONFIGURATION 47 ages pr2 core boxturtle and pr2 core cturtle which provide specific configurations and dependencies for the different ROS distributions In order to change which ROS distro is used by default simply change the symlink etc ros distro to point to a different distribution The two important entry point to etc ros that most users need to know about are etc ros setup bash and etc ros robot launch Note that each of these is actually just a symlink to the corresponding file in etc ros distro To make use of a specific distribution use e g etc ros boxturtle setup bash In Jaunty robots etc ros setup bash works by loading a number of environment variables from files stored in etc ros distro env The contents of each of these files will be loaded into the environment variable of the corresponding name In Lucid robots etc ros setup bash instead sources etc ros distro setup sh This is where additional environment variables should be set or tweaked if necessary etc ros robot launch is resp
40. flective which is used at startup to identify a home position Once the home position is identified the incremental encoders are used to track motion All drivetrains in the robot have positive engagement drives gears or belts and the motor controllers monitor for encoder errors The repeatability of the calibration sensors may cause minor differences in position sensing between runs Velocity estimates are made by differentiating the position sensors at Ims so the quantization of the encoders produces noise in the velocity signal which is significant at low speeds Torque estimates are made by measuring the commanded current of the motor and using the values of the torque constant from the data sheet of the motor together with the model of the transmission These transmission models assume 100 efficiency and accuracy of torque estimates and commands are limited by the friction in the drivetrain so joint torque accuracy should be characterized where one is relying on it 6 1 Drivetrains The three joints in each caster have basically the same drivetrain which is a Maxon amax 32 motor with a gear head and a continuous belt output Position sensing is done via an encoder on the back of the motor The drivetrain is efficient enough to be easily backdriveable All three motors work together to rotate the caster The rotation motor drives the rotation and the two wheels drive in opposite directions to provide additional forces To drive the two
41. g from operating over the components rated speed e Premature wear of slip rings or other electrical connections from operating over the components rated speed e Vibration damage to sensors or other components resulting from excessive velocities or collisions with joint stops CHAPTER Sensor Overview The PR2 has a variety of sensors on its body Insert Figure Here Figure 3 12 Sensor Modularity Diagram 9 1 Base Laser The base laser is a Hokuyo Top URG UTM 30LX scanning range finder This laser has a 30 m and a 270 degrees scanning range For more information see the hokuyo_node package at ros org 9 2 Tilting Laser In addition to the base laser the PR2 has a Hokuyo Top URG UTM 30LX mounted on a tilting platform located just below the pan tilt head The tilting platform can sweep the scanning laser through 135 degrees 90 degrees and 45 degrees from level and can be controlled using the default laser_tilt_controller For more information see the hokuyo_node and pr2_default_controllers packages at ros org 9 3 Head Cameras The PR2 pan tilt head has three cameras and a textured light projector e Wide Stereo Camera The wide stereo camera is part of the dual stereo pari and is a 100Mb color ethernet camera The wide stereo uses the Aptina MT9V032C12STC imager chip and has a maximum resolution of 752 x 480 pixels at 15 fps The camera has a field of view FOV of approximately 90 degrees and a 2 5mmm F2 5 Mars
42. g in security fixes for the pr2 configuration as well as for the appropriate ROS release 17 1 Fixing the Nvidia Module Occasionally upgrading the basestation will cause a new kernel to be installed When this happens the nvidia module which are built for the kernel will no longer work If this hap pens once a reboot is done X will fail to start Choose the option to exit X The script to re build and install the modules is located in usr src NVIDIA Linux x86 64 195 36 15 pkg2 run Simply run it sudo usr src NVIDIA Linux x86_64 195 36 15 pkg2 run 99 CHAPTER Running the PR2 Running the PR2 requires a basic understanding of ROS the BSD licensed Robot Oper ating System A ROS system consists of multiple processes running on multiple comput ers If ROS is not familiar it is recommended to follow some of the beginner tutorials on ros org Familiarity with ROS tools will make using the robot much easier In particular the PR2 user should understand what a launch file is and how to run it and how to run ROS with nodes on multiple computers This chapter will walk through the steps of starting up and running a PR2 using ROS 18 1 Out of the Box Please see the video Unpacking the PR2 This chapter assumes that the PR2 is already set up for use in the lab 18 2 Batteries and Power Before running the robot make sure it has power Follow the instructions in this chapter to start up the PR2 while it is plugged into the powe
43. hall V 4402 5 2 5 HR lens For more information see the wge100_camera package at ros org 29 CHAPTER 9 SENSOR OVERVIEW 30 e Narrow Stereo Camera The narrow stereo camera is part of the dual stereo pair and is a 100Mb monochrome ethernet camera The narrow stereo uses the Aptina MT9V032C12STM imager chip and has a maximum resolution of 752 x 480 pixels at 15 fps The camera has a FOV of approximately 55 degrees and a 5 6mm F2 0 Marshall V 4402 5 2 5 HR lens For more information see the wge100 camera package at ros org Gigabit Ethernet Camera The PR2 has a gigabit ethernet camera located to the left of the dual stereo pair on the pan tilt head The gigabit ethernet camera is a Prosilica GC2450C which uses the Sony ICX 625AQ imager chip and has a maximum resolution of 2448 x 2050 pixels at 15 fps Additionally the gigabit ethernet camera has a 8mm F1 4 F16 Kowa LM8JC lens For more information see the prosil ica camera package at ros org e Textured Light Projector The PR2 has a textured light projector located to the PR2 s left of the dual stereo pair on the pan tilt head The projector has a FOV of approximately 55 degrees and a 5 6mm F2 0 Kowa LM12JC lens For more information see the pr2 camera synchronizer package at ros org Note The projector will only work if the motors are enabled and the runstop is not hit 9 4 Gripper Sensors Accelerometer The gripper of the PR2 is equipped with a Bosch BM
44. he interaction between the robot and building networks The dotted lines show paths which may or may not be connected at any given point in time That is the basestation or a laptop may not always be plugged into the service port and the robot WAN port may not always be plugged into the building network The colored lines depict pathways that different network traffic follows CHAPTER 12 NETWORKING 38 The main thing of importance to note is that there are three ways to talk to the robot direct wire direct wireless or VPN Additionally the VPN traffic itself can be routed in one of two ways either via a wired or wireless path Note for clarity all interfaces connected to the building network as WAN and interfaces connected to the robot network as LAN have been labeled but this may not be the case for laptops or desktops on the actual network where the usual default interface name is typically etho e Direct wired connection One possibility is to connect a laptop or the basestation lan0 port to the PR2 service port This simply puts the laptop or the basestation directly on the PR2 s internal network The basestation is always configured to use the IP address 10 68 0 6 whereas the laptop will likely be configured to use DHCP When plugged into the service port the PR2 user can talk to the PR2 s LAN ports directly on the 10 68 0 0 24 subnet This system will work even if the VPN system is not functioning This is typically
45. ich moves up and down contains the speaker and the IMU as well as serving as the attachment point for both arms and for the head 5 3 Head The pan tilt head which holds the wide and narrow stereo cameras the 5 mega pixel camera and the texture projector is made up of two links the head pan link connected to the torso by the head pan joint and the head tilt link connected to the pan link by the head tilt joint The sensors are all attached to the tilt link The tilting Hokuyo laser range finder is mounted to the laser mount link which is tilted up and down by the laser tilt mount joint 17 CHAPTER 5 LINKS AND JOINTS 18 5 4 Arms The arms ofthe PR2 attach to the torso lift link at the shoulder pan joint which connects to the shoulder pan link The shoulder pan link represents the coun terbalance assembly of the arm Connected to the shoulder lift link through the shoulder lift joint The shoulder lift joint moves the arm up and down The upper arm roll joint allows the upper arm of the PR2 to rotate 268 degrees The elbow flex joint connects the upper arm roll link and the elbow flex link allowing the arm to bend similar to a human elbow The forearm roll joint attaches the x forearm roll link to the x elbow flex link and allows the elbow flex link to rotate continuously The elbow flex link is connected to the wrist flex link by the wrist flex joint The wrist flex link connects to the wrist roll li
46. ist flex joint 3 10 10 00 wrist roll joint 3 60 10 00 gripper joint 0 20 1000 The PR2 motor controller boards MCB s will not allow a current command greater than the maximum continuous current specified for the joint s actuator This means that maximum joint effort may be lower than the maximum effort specified above Below CHAPTER 8 MECHANICAL SPECIFICATION Ze are the actuators for each joint Maxon part number and their maximum allowable commanded current Joint Motor Power W Max Current caster rotation joint 236672 20 0 655 caster wheel joint 236672 20 0 655 torso lift joint 148877 150 3 12 laser tilt joint 310009 60 1072 head pan joint 310009 60 1 72 head tilt joint 310009 60 172 shoulder pan joint 148877 150 3 12 _shoulder_lift_joint 148877 150 3 12 _upper_arm_roll_joint 148877 150 3 12 elbow flex joint 148877 150 3 12 forearm roll joint 310009 60 1 72 _wrist_flex_joint 310009 60 1 72 wrist roll joint 310009 60 1 72 gripper joint 222057 11 0 204 More information about each actuator may be found in Maxon data sheets 8 3 Joint Limits and Types The position limits for the PR2 are specified below These hard limits are the maximum travel for the mechanism Joint Type Limit Limit caster rotation joint continuous caster wheel joint continuous torso lift joint prismatic 310 mm 0 mm laser tilt joint revolute 85 45 head pan joint revolute 168
47. ith the Robot 14 7 Forwarding IPs to the robot 15 Reinstalling the Basestation 15 1 Booting from the USB Installer 15 2 Booting from the DVD Installer sa oo soc e ee ns ee ee 16 Reinstalling the Robot 16 1 Forcing a Netboot 17 Software Maintenance 17 1 Fixing the Nvidia Module 40 40 41 41 42 42 42 43 43 44 44 45 45 45 46 46 46 47 47 48 49 49 49 49 50 50 50 50 5l 52 52 52 53 54 56 56 57 58 58 59 CONTENTS 18 Running the PR2 18 1 Out of the Box 18 2 Batteries and Power 18 3 Run Stop 18 4 Getting an Account 18 5 Turning on PR2 18 6 Logging In 18 7 Checking for Other Users e sor e ewe ewe EE a 18 8 Starting the PRI SoftWare gt sa e so ede soe ia caga a RAS aa 18 9 PR2 Dashboard Te Calibrating the Jones ap gs aros 18 11 Tucking PR2 Arms 18 12Drivine PRZ with a Joystick lt 4 coca e bbe dee te da a RE A an 18 13 istalicme Sensor Dats lt lt cues ponia rs oe OREO eS 18 14Putting PR2 Away 19 PR2 SE 60 60 60 60 61 61 62 62 62 63 63 64 64 65 65 67 CHAPTER Manual Overview This manual is intended to give PR2 users information to successfully install use and develop code on the PR2 robot The software on the PR2 is based on ROS Please visit ros org to learn about ROS and higher level software available for the PR2 To get started with the PR2 as quickly as possible please start by
48. ive into contact with or over any body part Do not allow the robot to interact with any sharp or dangerous items Do not allow the robot to operate potentially dangerous appliances like stoves or power tools e Pay attention to warning labels on the robot e Do not remove the covers of a PR2 or disassemble it in any way without prior and appropriate instruction by Willow Garage There are high voltages inside the robot There are a variety of pinch points and other mechanical dangers in the interior of the robot Counterbalances and springs store significant potential energy which could cause damage if unloaded abruptly e Do not modify or remove any part of the software safety features e The texture projector can trigger headaches or seizures in people sensitive to 50 Hz flashing light e When developing software always consider that some people have adverse reactions to the flicker from the texture projector and only turn it on when necessary CHAPTER 2 SAFETY 7 Regularly inspect and maintain anything the robot interacts with For exam ple regularly inspect the electrical outlets the robot plugs into Anticipate potential problems and hazards Always imagine what might happen ifthe robot malfunctions or behaves in a way different from the desired action Be vigilant e Be aware that many things can go wrong even with a seemingly simple activity For example consider what might go wrong while dri
49. k using lanl rather than lan0 enables the basestation to distinguish the 2 computers On a proper shutdown cl is switched back booting off the disk but in the event of a hard power failure the default BIOS state leaves cl netbooting This is convenient for reinstallation or recovery 13 2 Networking To keep connections behaving sensibly when transitioning the VPN connection to the basestation between wired and wireless the robot is configured to route ALL traffic that is not on the PR2 internal network out through the basestation Depending on if the robot has been installed as Jaunty or Lucid the mechanism that allows this is slightly different and discussed below In both OS versions iptables is configured using configuration files in etc iptables d These rules are responsible for providing fire walling on the robot wan0 interface turning on masquerading and NATing incoming VPN traffic into the robot local network 40 CHAPTER 18 COMPUTER CONFIGURATION 41 13 2 1 Jaunty Networking Any traffic not routed via the basestation is sent to a blackhole to keep connections from getting broken This means that if VPN is not connected the PR2 will not be able to see the outside world even though it might appear that the network is configured appropriately This is handled using an ip rule configuration Most of these rules are added by the init script etc init d iprules sh The current rule configuration can be viewed using the comm
50. king Up and Restoring Users Before reinstalling the robot operating system back up the user accounts This can be done with the command pr2 usermigrate To save users pr2admin ci sudo pr2 usermigrate save myrobot users Move this file off the robot before reinstalling Then to restore users sudo pr2 usermigrate load myrobot users 13 12 Clock Synchronization Consistent time stamping of data from the two computers is important for interpreting sensor data on a moving system As a result keeping the system time on the two computers synced together requires some attention The system that is used for this is chrony and the general strategy is to have the two computers tightly coupled to one another but loosely coupled to an external time source to prevent the robot time from drifting too far from the outside world Sometimes the clocks on the computers get into an inconsistent state This will show up as an error in the pr2dashboard as NTP offset from XXX to YY Y Offset too great If the clocks are in an inconsistent state try restarting chrony on the basestation cl and c2 in that order pr2admin basestation sudo etc init d chrony restart pr2admin ci sudo etc init d chrony restart pr2admin c2 sudo etc init d chrony restart The following message should show up Restarting time daemon chronyd is running and online If the following message shows Restarting time daemon chronyd is running and offline R
51. ks These aspects of the design are often described as inherent safety features For example the PR2 s arms are back drivable This means that when an arm CHAPTER 2 SAFETY 4 encounters an object be it a table or a person the interaction will drive the motors back and bring the arm to a stop Unlike traditional industrial robots the PR2 s arms cannot punch through an object The PR2 s arms have been designed using relatively small motors with respect to their payload This is possible due to a spring counterbalance offsetting the gravity forces acting on the arms That is the arms do not need to hold their own weight against gravity so the motors need only be strong enough to hold the payload The arms simply cannot push very hard In software low level checking has been incorporated to limit the current in a motor the velocity of a motor and the range through which a joint should travel Users and developers are obviously discouraged from changing these configurations High level applications also avoid obstacles during navigation and movement using the various on board sensors These design choices help make the PR2 robust However a robot with the PR2 s capabilities can never be absolutely safe The PR2 user s safety as well as the safety of others critically depends on the user s constant attention The PR2 user must be aware of the potential dangers and learn to anticipate and prevent problems 2 3 General Us
52. n PR2 If the robot is already running skip this step but the wireless run stop should still be in the stop position To turn the PR2 on 1 Verify that the wireless run stop is in the stop position If it is not yet in the stop position they press the wireless run stop s red STOP button the light s on the wireless run stop should turn off 2 Switch the red run stop button on the back panel of the robot to the on position turn it clockwise and it will pop out 3 If the DC breaker switch at the back panel of the robot is switched off then flip the DC breaker switch Figure 18 1 to the on position ON O OFF Figure 18 1 The PR2 DC breaker switch in the ON position The red lights on the computers should turn on the fans should spin up and several rising tone beeps from the computers should be heard as they boot The process of CHAPTER 18 RUNNING THE PR2 62 booting the computers will take about five minutes The computers are on when a red light illuminates on each of the computers in the robot base 18 6 Logging In Once the PR2 is on ssh into the main computer using the account created by the administrator using the steps below In the following instructions prx1 will be used to refer to the first computer on robot x and username to refer to the account username Ask the robot administrator what name should be used for the PR2 being set up To log into the robot open a terminal window and ty
53. native to simply stopping the processes running on the PR2 turn off the PR2 computers To do this open a new terminal and type ssh lt username gt pr lt x gt 1 sudo pr2 shutdown If the PR2 is turned off four sets of descending beeps from the PR2 s computers will be heard Then the red lights on each of the computers will turn off If this does not happen then the PR2 s computers might not be completely shut down properly CHAPTER 19 PR2 SE 67
54. nk by the wrist roll joint which can rotate continuously All together the PR2 arm has 7 DOF 5 5 Grippers The gripper consists of a central palm link called the gripper palm link which is rigidly fixed to the wrist roll link and has a single actuated degree of freedom The motor in the gripper drives the four joints of the gripper together to result in parallel motion of the fingertips The parallel distance between the gripper tips is treated as a translational joint called gripper joint that can be controlled The four rotational joints in the hand which are constrained to move together are also modeled as joints which can be observed but not controlled The gripper also contains a 3 DOF accelerometer and an LED which can be turned on and off to assist in calibration or finding the location of the gripper in camera images 5 6 Additional Information A CAD approximated kinematic and inertial description of the PR2 can be found in the pr2 description package This package uses a robot specific Extensible Markup Lan guage XML and Document Object Model DOM representation called Unified Robot Description Format URDF which can be converted or exported to other formats such as COLLADA CHAPTER Drivetrain Overview The joints in the PR2 are all actuated with brushed electric motors and all position sensing is done with optical incremental quadrature encoders Except where noted each joint has an optical sensor interrupt or re
55. o WAN port on back of robot e ecatO connected to robot ethercat network 33 CHAPTER 11 COMPUTER OVERVIEW 34 11 2 Computer 2 c2 Computer 2 c2 is physically located on the left side of the robot It is sometimes referred to as the slave computer because it netboots from cl c2 only has 2 ethernet ports lan0 and lanl both of which are connected to the internal robot network 11 3 Basestation The basestation is a Zareason xPC It is a dedicated point of contact through which network traffic to the robot can be routed It has 2 ethernet ports wan0 on the moth erboard is the primary ethernet port It is intended to be plugged into your building network lan0 on the pci card is a dedicated port for servicing the robot When neces sary this port should be plugged directly into the robot service port When configured properly it is important that the basestation is visible on UDP port 1194 or other user configurable port both via the wired building network as well as via the building wireless network This will likely require assistance from the local network administrator 11 4 Default Password Reference There are many different devices which make up the PR2 Many of these have passwords which should be changed for security purposes The default logins and passwords are e Basestation 10 68 0 6 Standard unix logins root willow pr2admin willow e Cl 10 68 0 1 Standard unix logins root willo
56. of software that attempts to write to the filesystem outside of the home directory some accommodating changed must be made to either the computer configuration or the software being used 13 4 autofs Both of the computers have auto mount configured for mounting the home partition of the other computer in a computer independent way using autofs These auto mounts are located in the directory pr To get to the home partition on cl use the path pr 1 and to get to the home partition on c2 use the path pr 2 It should rarely be needed to do this explicitly but it is necessary to make sense of home directory locations 13 5 Home Directories The default configuration for user home directories as given in etc passwd is u usernane Instead of a directory this location is by default a symlink to pr 1 username locating the home directory on cl To place a users home directory at a different location such as the disk on c2 an admin can simply move or copy the home directory and update the symlink accordingly CHAPTER 18 COMPUTER CONFIGURATION 43 13 6 Kernel Both cl and c2 run a 2 6 kernel with the RT PREEMPT patch The kernel is compiled in order to apply the patch and to enable some configuration 13 7 Storage Each computer has two hard drives one internal 2 5 inch 500Gb Seagate Momentus drive and a slot for a removable 3 5 inch SATA hard drive that is exposed on the top of the PR2 base By default the only hard drive us
57. onsible for setting up the robot configuration and then launching the minimal set of nodes for robot functionality The robot launch files for different distros may need to load different URDFs or analyzer files It is important that this file should use distrorelative paths rather than depending on the distro symlink For example in boxturtle it will use etc ros boxturtle urdf robot xml rather than etcros distro urdf robot xml This allows the launch file to be used even if the distro symlink points to a different distribution Finally etc ros sensors is a directory containing logical symlinks to sensors While udev rules have been provided to mount sensors in consistent locations in dev sensors this 2nd layer of indirection allows us to create a symlink such as etc ros base hokuyo rather than having to modify robot launch to use something like dev sensors hokuyo H0902620 The two hokuyos are the most likely devices to be configured incorrectly If the lasers are switched swap the symlinks for etc ros sensors base_hokuyo and etc ros sensors tilt_hokuyo Note that etc ros sensors on cl and c2 are different To modify the symlinks on c2 modify slave etc ros sensors from the cl machine 13 13 1 Switching ROS Distributions Example Example to switch from ROS boxturtle to ROS cturtle pr2admin0pri0XX etc ros ls 1 distro lrwxrwxrwx 1 root rosadmin 9 2010 11 10 15 27 distro gt boxturtle pr2admin0pri0XX etc ros
58. ors and put the power system in standby mode Note that this does not completely cut power to the robot Figure 3 3 The PR2 wireless run stop To start the wireless run stop press the green start button Figure 3 3 a flashing light on the wireless run stop will appear next to the green start but ton While transmitting the wireless run stop has a range of approximately 800 ft The wireless run stop is powered by four AA batteries the battery light will flash when the battery charge is low and new batteries are required It is recommended to always keep spare AA batteries handy CHAPTER 8 WHAT S IN THE BOX 11 e Robot Power Cord and Self Plug in Robot Power Cord To recharge the PR2 s batteries it must be plugged into a 120V 220VAC electrical outlet Use only the provided power cords many power cords and power strips have thinner conductors and cannot safely supply the current required by the PR2 F b Figure 3 4 The PR2 power cord Figure 3 5 The PR2 self plug in power cord Using inappropriate cables is hazardous and may cause fire Either cable may be used when manually plugging the robot in to re charge When plugging in the PR2 always attach the power cord to the AC inlet on the robot before attaching it to the AC outlet on the wall Unplug the cord from the wall before unplugging from the robot When attempting to have the PR2 plug itself in the shorter self plug in cord with attached checkerboard must
59. ot could cause damage by running into a person or falling down stairs The Safety Board maintains a list of all known hazards in a document called PR2 Hazards which can be found on the safety willowgarage com web site Anyone who works with a PR2 should review this list CHAPTER 2 SAFETY 8 regularly If a potential source of damage that is not covered by one of the hazards in the list is discovered please let Willow Garage know using one of the contact methods described below When a hazard is identified one or more of the following steps is taken e A design change is made to mitigate the potential damage Examples of these can be found in the document called Design for Risk Reduction on the safety willowgarage com web site e guideline is written to let people know how to avoid the potential damage The list of guidelines can be found in an earlier section of this chapter or in a document called PR2 Usage Guidelines on the safety willowgarage com web site e A warning decal is added to the robot Communication is key to the safety program There are several sources of information available e The web pages at safety willowgarage com e This chapter of the PR2 User Manual e A Safety Officer for each PR2 site assists with two way communication Anyone who has any concerns about safety or witnesses a safety related incident should contact the Willow Garage Safety Board e By email at safety Qwillowgarage com e By phone at 650
60. pe ssh lt username gt pr lt x gt 1 Access to all the ROS tools should be available For instance to see what packages are available type rospack list names and a list of the ROS packages currently in the path should be visible 18 7 Checking for Other Users Always check to see if anyone else is using the PR2 if logging into a robot that was already rumning robot users This will show who is currently running robot If nothing shows up then no one else is logged into the PR2 If other people are logged into the robot find out if their work may be interrupted Ask if it is ok to kill their processes so that new work can be done If the people running processes on the robot cannot be found ask the robot administrator for guidance on what the policy is in the lab If it is fine to kill other processes running on the robot type robot stop and all the processes that are being run on the robot will be killed 18 8 Starting the PR2 Software To start the PR2 use the robot command again to first claim the robot by leaving a message that others can see when logging into the robot CHAPTER 18 RUNNING THE PR2 63 robot claim m my message Then use the robot command to launch the basic functionality of the PR2 This includes drivers for the sensors motors speakers projector power system and joy stick as well as the default set of realtime controllers processing and logging of diag nostics information and
61. r it with the PR2 Be sure to unplug the PR2 from wall outlets if the PR2 is going to be driven around For more information on the buttons and functionality provided by the joystick see the pr2 teleop package 18 13 Visualizing Sensor Data To see the sensor data from the PR2 use rviz on the off board computer e g base station Open a new terminal window and configure the ROS MASTER URI to point at the PR2 run export ROS_MASTER_URI http pr lt x gt 1 11311 rosrun rviz rviz and rviz should launch with a visualization of the PR2 For more information about how to view different types of data coming from the PR2 see the rviz documentation at ros org 18 14 Putting PR2 Away To properly put away the PR2 drive the PR2 to the appropriate location in the lab plug in the PR2 to recharge the batteries press STOP on the wireless run stop stop the process on the PR2 and log off of the PR2 e Put away the PR2 Drive the PR2 to the appropriate location in the lab and plug it in to recharge e Stop all the processes running on the PR2 To stop all the processes running on the PR2 and log off of the PR2 but do not turn off the PR2 computers then open a new terminal and type ssh lt username gt pr lt x gt 1 robot stop e Exit from the PR2 s computer terminal type exit If someone was waiting to use the PR2 be sure to let them know that the PR2 is no longer in use CHAPTER 18 RUNNING THE PR2 66 As an alter
62. r outlet which will keep the batteries charged The battery life of the PR2 is approximately two hours so it is a good idea to keep the PR2 plugged in when not in use 18 3 Run Stop Before running the PR2 always have the wireless run stop nearby in case the motors need to be powered off for any reason The PR2 has two run stop buttons the red push button on the middle of the PR2 s back and the yellow wireless run stop transmitter If either one is in the stop position the motors are disabled so the robot cannot move In an emergency press the stop button on the wireless transmitter or hit the push button 60 CHAPTER 18 RUNNING THE PR2 61 in the back Putting either run stop button in the stop position does not damage the PR2 or turn off the computers it simply stops the motors The wireless run stop is also powered by batteries which can run down Therefore it is a good idea to turn the wireless run stop off by pressing the STOP button when not in use If the wireless run stop runs out of battery charge then the battery light the light next to the battery symbol in the lower half of the wireless run stop face will flash To change the battery a slotted screwdriver is needed to open the wireless run stop case 18 4 Getting an Account Before using the PR2 an account on the robot computers is needed Ask the robot administrator to create an account for PR2 users using the instructions in Chapter 13 18 5 Turning o
63. rage com regarding any ques tions about the PR2 s specifications 8 1 Environmental The PR2 is an indoor household robot Operating outside this type of environment could cause damage to the PR2 and injury or death to operators e Drive Surface The drive surface of the PR2 must be capable of supporting the entire weight of the PR2 about 450 pounds 220 kgs If the surface is too soft the PR2 can get stuck and fail to drive A commercial carpet or tile is recommended e Incline Surface The PR2 is ready for ADA compliant ramps which are at 1 12 slope Ramps that are steeper than a 1 12 slope are unsafe and may be a tip over hazard e Water The PR2 has not been tested for any type of contact with water or any other liquid Under no circumstances should the PR2 come in contact with water from rain mist ground water puddles and any other liquid Water contact can cause damage to the electrical circuitry and the mechanism e Temperature and Humidity Temperature testing of the PR2 has allowed the unit to run between 15C and 35C Towards the upper end of this range above 30C decreased performance of the batteries may be experienced Temperatures outside of this range can 25 CHAPTER 8 MECHANICAL SPECIFICATION 26 cause malfunctions in the PR2 power system and instruments The PR2 has been tested in high humidity but under no circumstances should condensation be allowed to form on the mechanism
64. rations CHAPTER 6 DRIVETRAIN OVERVIEW 21 6 5 Drivetrains The first four degrees of freedom in the arm shoulder pan shoulder lift upper arm roll and elbow flex are all driven with Maxon RE40 motors that have single stage planetary gear heads which output to a toothed pulley that runs on a belt These belts all have terminations at either end of a capstan on the moving link which is how the torque is transmitted The terminations are also how these belts are tensioned Proper belt tensioning is important to prevent backlash which can come from extra slack in the belt and excess wear which can come from a belt which is too tight too loose or just misaligned The position is measured via an optical encoder on the back of the motor so the backlash of the gear head and the stretch of the belt both contribute to the error in the sensed position Velocity limits are important on these joints to prevent motor damage from running over speed as well as to prevent rapid deceleration which can damage the motor gear head and belt All of these drivetrains have fairly high efficiency which means they can be back driven This is made possible by the low force requirements on those joints due to the arms counterbalance The counterbalance uses a system of springs and linkages to com pensate for the effect of gravity on the upper arm and forearm links The compensation should be effective throughout the range of motion of the first four links of
65. reading Chapter 2 Safety do not start operating the PR2 before reading Chapter 2 If the PR2 is being set up for the first time please see the tutorial video Unpacking the PR2 to learn how to set it up properly before it is used then feel free to move on to Chapter 6 to learn how to start up and run the PR2 1 1 Before you start Before getting started please read through this section to review everything needed to use the PR2 safely and successfully e PR2 Safety Be sure to read Chapter 2 Safety in its entirety before using the PR2 e Safe Environment The space where the PR2 operates should be free of hazards Specifically stairways and other drop offs can pose an extreme danger Avoid hazardous objects sharp objects such as knives sources of fire hazardous chemicals or furniture that could be knocked over See Chapter 2 Safety for more details on making sure the PR2 s users and environment is safe e Space To use the PR2 enough space is needed for it to drive around move its arms and perform tasks The PR2 is designed to move through ADA compliant spaces Americans with Disabilities Act Doorways should be at least 32 inches wide and the ground should be flat and level CHAPTER 1 MANUAL OVERVIEW 2 e Development Tools At least one laptop or desktop computer to connect to the robot is needed The PR2 ships with a base station computer which is a desktop but PR2 users must provide their
66. s can be done in one of two way The easier way is to connect up to the KVM See the section on how to connect up to the KVM Alternatively plug a keyboard into the PR2 This can be done using the aux usb port under the back cover To remove this cover follow the instructions found in the PR2 Support website When the PR2 is booting 2 beeps will sound followed by a short pause and then another 2 beeps After the 4th beep hit F12 on the keyboard either physically or through the KVM to force cl to neboot 58 CHAPTER Software Maintenance When the robots ship the most recent version of ROS and the PR2 software stacks is installed in opt ros By default new users will have a ROS installation which references the pre installed code Users who wish to modify or replace a part of the system are recommended to install a development version of the stacks or packages which they wish to modify but to continue to use the base installation for most of the robot functionality Debian packages exist for all of the custom software and configurations on the robot The package which pulls in all the other requirements is called pr2 environment pr2 environment depends on pr2 core which in turn depends on ros boxturtle pr2 the meta package which contains all of the ROS software for the PR2 To upgrade the software on the PR2 simply use apt sudo apt get update sudo apt get dist upgrade Which will update all packages on the system pullin
67. sestation can be reinstalled to revert it to a completely fresh state Creating a new USB installer is outside the scope of this manual but instruction for downloading and creating one can be found on the PR2 Support website under Download 15 1 Booting from the USB Installer To boot off the USB installer 1 Insert the USB stick into one of the USB ports in the basestation 2 Reboot the basestation 3 Press the DEL or Delete key to enter setup 4 Choose Advanced BIOS Features 5 Choose Hard Disk Boot Priority 6 Select the drive listed as USB HDDO and press Page Up to make it number 1 7 Press F10 to save and exit the setup 8 The computer should boot off of the USB stick 9 If the installer complains about not being able to find the ISO choose Scan Hard Drive fro ISO and then press Enter to continue 10 Once the installer is actually progressing it will take about half an hour to com plete 11 When the installer completes press Enter to shut down and remove the USB stick 56 CHAPTER 15 REINSTALLING THE BASESTATION 97 12 When the basestation boots a fresh image should be acquired the section on Bases tation Setup and Pairing to configure the basestation 15 2 Booting from the DVD Installer To boot off the DVD installer 1 10 11 12 Insert the DVD into the drive on the basestation Reboot the basestation Press the DEL or Delete ke
68. t the problem is As the PR2 administrator for help if there are errors that are not understood For more information on using and debugging with the pr2 dashboard see the beginner PR2 tutorials on pr2support willowgarage com 18 10 Calibrating the Joints If no problems are discovered in the diagnostics and the continuation of the PR2 bring up is desired first check the physical area around the robot to ensure that the PR2 will not hit anything around it when it calibrates The PR2 s arms will be fully extended and CHAPTER 18 RUNNING THE PR2 64 the spine will move up and down during calibration Once the physical area is cleared press the green START button on the wireless run stop This should change the state of the run stop indicator on the dashboard to a green circle and will allow the robot to turn power on for the motors If the PR2 circuit breakers are not yet enabled the next step is to enable the circuit breakers marked L B R When the circuit breaker icon is clicked select enable all from the menu to turn on all three breakers If the PR2 motors are not yet reset then click on the picture of a motor and select reset motors When the wireless run stop is started all the PR2 circuit breakers are enabled and the PR2 motors are reset the PR2 will move its joints to find the absolute reference positions of each joint so that it can calibrate that mechanism When calibration is finished all the icons in
69. the DC breaker and contact Willow Garage If it is plugged into an AC outlet do not touch the robot Turn off the circuit breaker that controls the outlet Before removing any covers the PR2 should be unplugged and the DC breaker should be turned off CHAPTER 2 SAFETY 6 Make sure the power cord is in good condition Cord insulation must be intact with no cracks or deterioration Both connectors should be undamaged If the power cord is damaged in any way it should be discarded and replaced with a new cord from Willow Garage e When plugging in the PR2 always attach the power cord to the AC inlet on the robot before attaching it to the AC outlet on the wall Unplug the cord from the wall before unplugging from the robot e Use extreme caution whenever the robot s spine is contracting Objects or body parts could be crushed between the robot s body and base Also keep people and objects away from the PR2 s joints e Make sure the batteries cannot be overheated or punctured Do not run the robot without its covers They help protect the batteries during inadvertent collisions e The PR2 user should always have immediate access to the wireless run stop box and should stop the robot at the fist sign of a problem The stop button should always be pressed when examining inspecting or maintaining the robot e Use common sense when operating the robot Do not allow the robot to grab or hit any person Do not allow the robot to dr
70. the arm 6 6 Drivetrain The forearm roll joint is driven by a motor in the upper arm with a planetary gear head and external spur gear Position is measured via an optical encoder on the back of the motor Because of the higher hear reduction the efficiency and backdriveability of this joint is not as good as that of the first four joints of the arm The wrist flex and roll use a differential drive between two motors If the motors are turned in the same direction the wrist rolls if they are turned opposite the wrist flexes The differential bevel gears are attached after a standard encoder motor and gear head assembly 6 7 Drivetrain The gripper consists of two fingers with two joints each Within each finger a four bar linkage constrains the two joints to move together so that the fingertips remain parallel The two fingers are constrained together with a sector gear that meshes between the first phalanges of the two fingers The motion of the fingers is driven by a motor which drives a lead screw in the palm of the hand This lead screw is embedded in the four bar linkage so that the rotation of the motor has a nonlinear relationship to the movement of the joints The gripper can be back driven when significant force is applied Unlike all other non continuous joints in the system the gripper has no calibration flag Initial homing is done by closing the gripper until it gets blocked and then treating that position as a zero point This m
71. top of a stairway or any other drop off Make sure the robot has adequate and level space for any expected or unex pected operation If the robot travels on a ramp make sure the spine is lowered and the arms are tucked in so that the center of gravity is as low as possible The slope should not be more than 1 12 Ensure that the robot cannot fall off the edge under any circumstances Make sure the environment is free of objects that could pose a risk if knocked hit or otherwise affected by the PR2 Make sure there are no cables or ropes that could be caught in the covers wheels or arms these could pull other objects over Make sure no animals are near the robot Keep fingers hair and clothing away from wheels and gears Be aware of the location of emergency exits and make sure the robot cannot block them Do not operate the robot outdoors e The PR2 covers are flammable Keep the PR2 away from open flames and other heat sources The PR2 covers may burn if ignited Never use the PR2 around stoves or ovens Always be prepared for a fire and have a fire extinguisher close by and ready to use An ignition source could come from anywhere including an internal failure of the PR2 system Use caution to avoid electrical shock Do not allow the robot to come in contact with liquids spilled drinks rain etc This is particularly important when the robot is plugged into an AC outlet If a robot does get wet turn off
72. ume that the basestation is plugged into the robot via the service port 14 1 Requirements 14 1 1 Naming In order for ROS to work properly it depends on each computer in the system being able to correctly resolve the hostnames of all other computers in the ROS system For an in depth explanation please become familiar with NetworkSetup In short 3 hostnames and 3 IP addresses are needed one for the basestation and one for each of the two robot computers Each of these 3 hostnames MUST either be resolved by the building network DNS server or else they will need to be added to the etc hosts file of all the relevant computers 14 1 2 IP Address Configuration For the robot to be able to find the basestation it needs to be given a constant IP address Unless there is a reason not to this IP address should be assigned to the basestation statically However if it is certain that the DHCP server will always assign the same IP it is ok for this IP to be assigned via DHCP The IP address assigned to the basestation must be visible on both the wired and wire less segments of the building network on port 1194 This is the port that VPN uses when the robot makes its connection back to the basestation it can be changed by appropri ately modifying etc openvpn server conf on the basestation and etc openvpn basestation conf on the robot Depending on how secure the network is and whether these segments are separated by a firewall assistan
73. used for reinstalling the robot or debugging other networking problems e Direct wireless connection Another possibility is to connect a laptop directly to the PR2 s WAP This is essentially identical to plugging into the service port The PR2 computers can be reached directly on the 10 68 0 0 24 subnet e VPN connection When not plugged int the service port the basestation and PR2 communicate over VPN The basestation acts as the VPN server and is always reachable at 10 68 255 1 However there are two mechanism through which the VPN traffic may be routed Wired VPN connection The wired VPN connection is depicted in blue This only occurs when the robot Wan port is plugged into the building network Note that wan0 on cl goes directly to the robot WAN port When this is plugged into the building network cl acquires an IP address via DHCP At that point cl initiates a connection to the basestation using a specified static IP address Once this connection is established all VPN traffic is routed through this pathway Wireless VPN connection The wireless VPN connection is depicted in red If the WAN port is not plugged in the robot falls back on its wireless connection A secondary route instead send traffic through the wifi router which must be con figured to connect to the building wireless network In many cases the wireless network is located outside the firewall so it is important that the CHAPTER 12
74. ving the robot with the joystick The joystick could run out of batteries The Bluetooth connection between the joystick and the robot could fail The ROS node that talks to the Bluetooth driver could have been changed or have a bug The operating system in the robots computer could hang The motor controller software node could fail The motor controller board could fail The PR2 s electrical system could fail The motor or gear train could have a problem The wheels could have a problem Someone else could command the robot to move without the PR2 user s knowl edge The PR2 user could make a mistake It is intuitive to drive a robot when it is going away from the user but when it is coming towards the user everything is reversed 2 4 Safety Program The possibility of injury can never be completely eliminated when working with a PR2 Therefore Willow Garage has instituted a safety program to focus continual effort and attention on risk reduction The program is managed by a Safety Board and has three main goals e Anticipation identifying potential hazards associated with the PR2 e Mitigation taking action to reduce the likelihood and severity of hazards e Communication exchanging information about safety within the community The foundation of the safety program is an ongoing effort to identify ways a PR2 could cause damage These are referred to as hazards For example a rob
75. w pr2admin willow e Cl 10 68 0 1 Web interface login admin admin guest guest e C1 ESMS 10 68 0 91 root changeme e C2 ESMS 10 68 0 92 root changeme CHAPTER 11 COMPUTER OVERVIEW e Wireless Router 10 68 0 5 root willow e Wireless Access Point 10 68 0 250 root willow 35 CHAPTER Networking The majority of communication between components onboard the PR2 happens via an onboard ethernet network referred to as the robot internal network This onboard network can be accessed directly via either wired connection through the service port or wireless connection through the WAP Additionally the robot can be accessed via the basestation through a VPN tunnel 12 1 Network Segments There are a couple of different important network segments outlined here and discussed in more detail in the section 12 2 below 10 68 0 0 24 Primary Robot Internal Network The 10 68 0 0 subnet is the primary network used internally by the computers on the robot Both computers and the bases tation have addresses on this subnet Additionally many of the ethernet based devices such as the power board are given addresses on this subnet The robot Service Port and the cradle point ctr350 Wireless Access Point are directly connected to this network allowing a user to easily put their laptop on the robot internal network cl if booted will give out IP addresses via DHCP in the range 10
76. w Garage the password will most likely be set to willow 13 9 Creating User Accounts The expectation is that each person logging into the robot to develop code will have their own user account Any robot admin can create a new user using the adduser command NOT the useradd command on cl User accounts are automatically mirrored on c2 Some examples sudo adduser bob sudo adduser bill shell usr bin tcsh uid 2000 Note it may be helpful to assign users the same UID used on the building network so the UIDs are consistent when mounting shares or moving around the removable drives Do not create user accounts with UIDs over 30000 Moving the home directory and creating the symlink is handled by the script usr local sbin adduser local which gets run automatically as a part of user creation Do not worry about this script at all unless there are changes to the user creation process 13 10 User Groups There are a couple of important groups on the pr2 e admin Members of this group have full root privileges when using the sudo command e rosadmin Members of this group have access to change ros specific configuration settings in etc ros e apt Members of this group can install new software To add a user to a group use the usermod command The most common invocation uses the options a append and G group For example sudo usermod a G admin bob CHAPTER 18 COMPUTER CONFIGURATION 46 13 11 Bac
77. wer Input Each MCB is connected to the raw battery power bus and using the circuit breakers there can be a switch between enabled which provides 44 80VDC to the MCB and allows it to drive the motor standby which provides 18 VDC to the MCB and allows it to continue to communicate and read sensors but does not allow driving the motors and disabled which turns off power to the MCB altogether Digital Input Each MCB has a digital input which is used for detecting the flags at the calibration positions on power up The MCB internally latches the encoder counts at the time that the digital input transitions from high to low and from low to high which accurate detection of calibration flag positions Digital Output Each MCB has a digital output On the gripper this is used to control the LED mounted in the hand Elsewhere in the robot this is used to generate synchronization pulses which allows synchronizing the cameras the projector and the motion control systems together Motor Output Each MCB can drive a single brushed DC motor The MCB drives the output with an H bridge and uses a current measurement to do closed loop current control on the motor SPI There are two SPI ports which are only available on the gripper MCB s and which are used to connect to the fingertip sensors CHAPTER 7 MOTION CONTROL 24 7 2 Realtime Loop The realtime loop for the PR2 is a single process which c
78. wheel motors rotate in the same direction and the rotation motor helps to keep them aligned in the proper direction 19 CHAPTER 6 DRIVETRAIN OVERVIEW 20 6 2 Drivetrain The torso is driven up and down on a linear rail by a combination of a gas spring which supports most of the weight of the torso and a lead screw which is driven via an Maxon RE40 motor with 113 1 gear head connected to a continuous belt drive with a 5 1 reduction As a result of the force from the gas spring not being constant over the range of travel the lead screw may be loaded up down or neutrally as different points of travel of the torso Position sensing of torso lift is done via optical encoder on the back of the motor so any backlash in the lead screw belt or gear head is not sensed The torso joint has low efficiency so commanding large forces in the range of 1000 newtons will be required to move the torso The maximum speed of the torso lift joint is limited by the thermal rating of the lead screw nut Driving the torso lift link faster than the velocity limit will cause permanent damage to the lead screw assembly Similarly driving at the safety limit but with excessive load because of the large reduction the torso lift link is capable of exerting high forces 6 3 Drivetrains The drivetrains for the head pan head tilt and laser tilt are all fairly similar Since precise pointing of sensors is important all three of these joints have 10 000 count en
79. y to enter setup Choose Advanced BIOS Features Choose Hard Disk Boot Priority Select the CDROM and press Page Up to make it number 1 Press F10 to save and exit the setup The computer should boot off of the DVD If the installer complains about not being able to find the ISO choose Scan Hard Drive for ISO and then press Enter to continue Once the installer is actually progressing it will take about half an hour to com plete When the installer completes press Enter to shut down and remove the DVD When the basestation boots a fresh image should be acquired consult the section on Basestation Setup and Pairing to configure the basestation CHAPTER Reinstalling the Robot To reinstall the robot first back up anything needed off of cl Next shutdown the computer using pr2 shutdown netboot Make sure to then plug the service port directly into the basestation Run the robot installer sudo robot install 1 Boot cl by pushing the power button with a paperclip 2 After N minutes the net console on the basestation will show the install dialog Press Enter to start the installer and wait for it to complete 3 Once the installer has completed and the PR2 is shut down boot it up The PR2 must be paired with the basestation before it can be used 16 1 Forcing a Netboot If the robot BIOS is not configured to netboot hit F12 on the keyboard Thi

PR2 Manual - Clearpath Robotics

Contents

Download Pdf Manuals

Related Search

Related Contents