Roadmap

1. Roadmap • Boards & Buses • Communications • Sensing • Software • Goals

2. Electronics Overview

3. Advanced Digital Logic’s MSM-P5S Processor: Intel Pentium 166MHz Ports: 2(4) Serial, 1 Parallel Memory: 32 MB Storage: E-IDE HD & Floppy Power: @5V < 8W Features: Ethernet Video-In Size: 101.6 x 91.4 x 50.8 mm Weight: ~0.17kg Cost: $1307

4. Operating System • Red Hat Linux 5.2 • Expected control rate of 100Hz • Large development support base • Familiarity • Inexpensive

5. Offboard Communication

6. Onboard Communications Bus • RS-485 • Increased Noise Immunity • Balanced signals • Multiple transmitters/receivers on a single chain • Processor uses standard serial ports (RS-232) • Converter translates RS-232 to RS-485 signals, allowing multiple motor controllers to talk to the same serial port • RS-485 bus has 4 branches • 3 Joints (1,2,3) & Gripper A • 4 Joints (4,5,6,7) & Gripper B • 4 Joints (8,9,10,11) & Gripper C • 3 A/Ds for the 6 IR sensors and F/T sensors

7. Motor Control • Distributed • 14 JR Kerr PicServos • Independently and group addressable • High Speed • Coordinated control rate of 100+Hz • PID servoing loop runs at ~20kHz • Easy to interface • Direct interface with 3 channel encoders • Plugs into standard serial port through converter

8. Control Layers

9. Sensing • Skyworker • Forces • Joint Angles • Gripper Sensing • Future Enhancements • Position/Localization Sensing • Compensate for dead reckoning errors during large traverses • Expensive and unnecessary for prototype operations • Improved Gripper Sensing • Allow for larger errors in world model

10. Force Torque Sensor Placement

11. Force Sensing • Record forces exerted by Skyworker • Capable of measuring large torques and small forces • Three JR3 6-DOF force-torque sensors • 67 mm diameter x 25 mm thick • 200N sensor (actual performance is a function of the forces applied along each axis) • Approximately 170g

12. Joint Sensing • Sense properties of joints to support multiple tasks • Walking; gripping; insertion; etc • Detect and report joint angles • Joint angular resolution of 2633 ticks/degree • Gripper angular resolution of 1077 ticks/degree • Gearing Errors • Planetary Drive 1.3 degree positioning error (0.78 arc min after 100:1 harmonic) • Harmonic Drive: Repeatability 1.4 arc seconds, Hysteresis 1 arc min • 1.55mm of error due to backlash

13. IR Sensors Mounts Gripper Sensing • Utilize two IR range sensors to determine the orientation and location of the target • Precision of 0.7% (0.9 mm) at 13cm • Sampling rate of 100Hz

14. Gripper Sensing • Detect presence of objects • Detect approach errors/ world model errors • Utilize the Sharp GP2D12 as a LADAR representative sensor • Sensing range 10-80cm • Non-linear analog output (higher resolution at shorter ranges)

15. Communications Model • Publish/Subscribe paradigm • Allows for extensibility • Information sharing • Control transfer • Tasks to be performed are published • Robot is specified in the message • Task completion and robot telemetry published • Allows for visualization and is potentially useful in cooperative behavior

16. Inter Process Communication • Anonymous Publish/Subscribe model • Robust operation • Safe to stop start Producers/Consumers • Client crash won’t take down network • Simple interface • Local expertise • Developed at CMU by Reid Simmons

17. Communication Layers

18. Software Design • Control partitioning and scalability concerns • Modularity • Easy interchange and upgrade of component elements • Decoupled components allow melding of simulation and real world • Provide a common interface to both simulation and operation

19. Software Blueprint

20. Viz • Allows programmer to create and manipulate complex three dimensional scenes • Imports VRML and OpenInventor (ProE exports both of these types) • C and Python programming language interfaces through XDR • Maintained by NASA Ames

21. Robot Configurator • Provides a technique for visualization of the joint configurations using Viz. • Allows the user to specify joint angles for all 11 DOF and select between anchor grippers.

22. Sky Script • Tool for developing high-level scripts to coordinate various Skyworker actions

23. Sky Coordinator • Receives plan messages from user interface • Parses scripts and queues actions in the coordinator robot models • Broadcasts high level actions to robots • Waits for acknowledgment of completion before sending further commands

24. Sky Robot • Breaks high level actions into smaller components and passes them to Sky Onboard • Keeps track of robot’s world position and internal state • Transforms requested end effector positions into internal joint angles • Queues actions if they are received before they can’t be immediately processed • Generates telemetry packets for visualization

25. Kinematics • Use D-H joint labeling • Inverse Kinematics performed through inverting the Jacobian utilizing a singularity robust inverse (SRI) • Idea: • Take small straight line steps through world space to desired position • Iterative algorithm • Limit step size so as to chose the joint configuration nearest to current posture • SRI idea: • Check to see if the Jacobian is becoming singular, if it is, “nudge” the desired position so as to avoid the singularity

26. D-H Model Gripper A holding structure

27. D-H Model Gripper B holding structure

28. Onboard Controller • Provides interface between hardware and software • Specifies joint angles and velocities to the motor controller • Interprets and reacts to sensor inputs • Utilizes a library of predefined joint trajectories • Generates low level telemetry packets 10-30 times a second

29. Initialization • Script is parsed by Sky Coordinator • Robots and their Onboard counterparts are “spawned” on machines identified in the script • All “Sky Robot” processes are homogenous • Sky Onboard is instantiated with either a simulated or actual motor controller • Sky Onboard performs axis homing and other initialization before reporting that it is available • Sky Coordinator waits until the Sky Robot and Sky Onboard are reported as operational before issuing any commands

30. Software Progress

31. Mobile Robot Design Class Skyworker Organizational Chart

32. Mechanical $19,890 Computational $7,845 Sensing $20,320 Power $3,100 Tooling $481 Outsourcing $44,730 Total $96,366 Reserve $6,633 Budget

33. Outcomes of Skyworker Phase I robots performing representative SSP assembly, inspection and maintenance tasks • physical demonstrations • a few fundamental scripted operations at laboratory scale • first evaluations of force, energy and control considerations • simulations • large scale / long duration operations • multiple robots working in coordination

34. Outcomes of Skyworker Phase I new approach to space robot worksystems • walking manipulator • motion by successive attachment to structure • constant velocity motion of payloads (“walking under the payload”) • limbs function as legs or arms • proprioceptive • self-contained

35. Outcomes of Skyworker Phase I opportunity to investigate important issues: • static/dynamic interactions of robot and facility structure • energy consumption • control strategies • infrastructure requirements imposed on the SSP facility by robots • robot coordination and task planning • robot workforce productivity

36. Skyworker Phase II - Robot • Push the performance envelope • better adaptation to structures • lighter walking • alternative grippers • ambitious maneuvers and tasks • Increase our understanding of the important issues • verify analyses of Skyworker performance through physical experiments • explore motivations (and solutions if needed) for • global position estimation • unit robot autonomy

37. Skyworker Phase II - Simulator • Push the performance envelope • task decomposition and scheduling • robot cooperation • Increase our understanding of the important issues • control bandwidth • study task duration vs. robot specifications • investigate robot workforce requirements • explore alternative robot/facility scale ratios