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The Next StepSPACE ROBOTICS INITIATIVE
CDR11/18/99-1
RoadmapRoadmapRoadmapRoadmap
• Boards & Buses
• Communications
• Sensing
• Software
• Goals
The Next StepSPACE ROBOTICS INITIATIVE
CDR11/18/99-3
Processor: Intel Pentium 166MHzPorts: 2(4) Serial, 1 ParallelMemory: 32 MBStorage: E-IDE HD & FloppyPower: @5V < 8WFeatures: Ethernet
Video-InSize: 101.6 x 91.4 x 50.8 mmWeight: ~0.17kgCost: $1307
Advanced Digital Logic’s MSM-P5SAdvanced Digital Logic’s MSM-P5SAdvanced Digital Logic’s MSM-P5SAdvanced Digital Logic’s MSM-P5S
The Next StepSPACE ROBOTICS INITIATIVE
CDR11/18/99-4
Operating SystemOperating SystemOperating SystemOperating System• Red Hat Linux 5.2
– Expected control rate of 100Hz
– Large development support base
– Familiarity– Inexpensive
The Next StepSPACE ROBOTICS INITIATIVE
CDR11/18/99-5
Offboard CommunicationOffboard CommunicationOffboard CommunicationOffboard Communication
Format Signal Characteristics
Physical Characteristics
Cost
RF serial Pontech SWM-1
RS-232 serial 85 kbps
300 ft (walls) 900 mHz DSS
5.25” x 4” x 1” 8 oz 300 mA 5 V DC
$250/pair
IR serial Oplink OPM 115HP
RS-232 serial 115 kbs
230 ft (line of sight) 65 ft (indirect)
3.75” x 2” x1.25” 10 oz 100 mA 5 V DC
Unknown
RF ethernet Lucent WaveLAN
PCMCIA ethernet 1800 kbps
1300 ft (walls) 2 GHz DSS
10.2” x 7.2” x 2.0” (hub) 3.86 lb 330 mA 5 V DC
$240 (card) $1300 (hub)
RF ethernet Proxim RageLAN
10 Base T 1600 kbps
300 ft (walls) 2 GHz DSS
5.4” x 3.3” x 1.35” 9.2 oz 240 mA 9 V DC
$700 (adapter) $1000 (hub)
The Next StepSPACE ROBOTICS INITIATIVE
CDR11/18/99-6
Onboard Communications BusOnboard Communications BusOnboard Communications BusOnboard 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 branches1. 3 Joints (1,2,3) & Gripper A2. 4 Joints (4,5,6,7) & Gripper B3. 4 Joints (8,9,10,11) & Gripper C4. 3 A/Ds for the 6 IR sensors and F/T
sensors
The Next StepSPACE ROBOTICS INITIATIVE
CDR11/18/99-7
Motor ControlMotor ControlMotor ControlMotor 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
The Next StepSPACE ROBOTICS INITIATIVE
CDR11/18/99-8
Control LayersControl LayersControl LayersControl Layers
The Next StepSPACE ROBOTICS INITIATIVE
CDR11/18/99-9
SensingSensingSensingSensing
• 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
The Next StepSPACE ROBOTICS INITIATIVE
CDR11/18/99-10
Force Torque Sensor PlacementForce Torque Sensor PlacementForce Torque Sensor PlacementForce Torque Sensor Placement
The Next StepSPACE ROBOTICS INITIATIVE
CDR11/18/99-11
Force SensingForce SensingForce SensingForce 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
The Next StepSPACE ROBOTICS INITIATIVE
CDR11/18/99-12
Joint SensingJoint SensingJoint SensingJoint 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
The Next StepSPACE ROBOTICS INITIATIVE
CDR11/18/99-13
Gripper SensingGripper SensingGripper SensingGripper 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
IR Sensors Mounts
The Next StepSPACE ROBOTICS INITIATIVE
CDR11/18/99-14
Gripper SensingGripper SensingGripper SensingGripper 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)
Sensor Values
0
20
40
60
80
100
120
140
Mea
sure
men
t (m
m)
Actual Distance
Real Sensor
The Next StepSPACE ROBOTICS INITIATIVE
CDR11/18/99-15
Communications ModelCommunications ModelCommunications ModelCommunications 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
The Next StepSPACE ROBOTICS INITIATIVE
CDR11/18/99-16
Inter Process CommunicationInter Process CommunicationInter Process CommunicationInter 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
The Next StepSPACE ROBOTICS INITIATIVE
CDR11/18/99-17
Communication LayersCommunication LayersCommunication LayersCommunication Layers
The Next StepSPACE ROBOTICS INITIATIVE
CDR11/18/99-18
Software DesignSoftware DesignSoftware DesignSoftware 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
The Next StepSPACE ROBOTICS INITIATIVE
CDR11/18/99-19
Software BlueprintSoftware BlueprintSoftware BlueprintSoftware Blueprint
The Next StepSPACE ROBOTICS INITIATIVE
CDR11/18/99-20
VizVizVizViz
• 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
The Next StepSPACE ROBOTICS INITIATIVE
CDR11/18/99-21
Robot ConfiguratorRobot ConfiguratorRobot ConfiguratorRobot 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.
The Next StepSPACE ROBOTICS INITIATIVE
CDR11/18/99-22
Sky ScriptSky ScriptSky ScriptSky Script
• Tool for developing high-level scripts to coordinate various Skyworker actions
The Next StepSPACE ROBOTICS INITIATIVE
CDR11/18/99-23
Sky CoordinatorSky CoordinatorSky CoordinatorSky 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
The Next StepSPACE ROBOTICS INITIATIVE
CDR11/18/99-24
Sky RobotSky RobotSky RobotSky 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
The Next StepSPACE ROBOTICS INITIATIVE
CDR11/18/99-25
KinematicsKinematicsKinematicsKinematics
• 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
The Next StepSPACE ROBOTICS INITIATIVE
CDR11/18/99-26
D-H ModelD-H ModelD-H ModelD-H Model
Gripper A holding structure
The Next StepSPACE ROBOTICS INITIATIVE
CDR11/18/99-27
D-H ModelD-H ModelD-H ModelD-H Model
Gripper B holding structure
The Next StepSPACE ROBOTICS INITIATIVE
CDR11/18/99-28
Onboard ControllerOnboard ControllerOnboard ControllerOnboard 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
The Next StepSPACE ROBOTICS INITIATIVE
CDR11/18/99-29
InitializationInitializationInitializationInitialization• 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
The Next StepSPACE ROBOTICS INITIATIVE
CDR11/18/99-30
Software ProgressSoftware ProgressSoftware ProgressSoftware Progress
The Next StepSPACE ROBOTICS INITIATIVE
CDR11/18/99-31
Skyworker Organizational ChartSkyworker Organizational ChartSkyworker Organizational ChartSkyworker Organizational Chart
Mobile Robot Design Class
C h ris G a isorM e ch. E n g in e er
S a rjou n S ka ffM e ch.E n g in e er
J in w u Q ianM e ch. E n g in e er
P e te r S ta ritzM e ch a n ica l L e ad
W illia m W o ngC o m p u te r E n g in e er
O re n L a sk inC o m p u te r E n g in e er
D e W itt La tt im erN IS T S e n so rs E n g .
Jo na th an S a m u e lP o w er E n g in e er
S co tt R ob b insC o m p ute r S cie n tist
T im W a rn e ckP o w er E n g in e er
Ja so n M e ss in g erC o m p u te r E n g in e er
C h ris U rm sonE le c trica l L e ad
J im "O z" O sb o rnP ro je c t S c ie n tist
W illia m "R ed " W h itta kerP rin cip le Inve s tig a to r
The Next StepSPACE ROBOTICS INITIATIVE
CDR11/18/99-32
BudgetBudgetBudgetBudget
$6,633 Reserve
$96,366Total
$44,730 Outsourcing
$481 Tooling
$3,100 Power
$20,320 Sensing
$7,845 Computational
$19,890 Mechanical
The Next StepSPACE ROBOTICS INITIATIVE
CDR11/18/99-33
Outcomes of Skyworker Phase IOutcomes of Skyworker Phase IOutcomes of Skyworker Phase IOutcomes 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
The Next StepSPACE ROBOTICS INITIATIVE
CDR11/18/99-34
Outcomes of Skyworker Phase IOutcomes of Skyworker Phase IOutcomes of Skyworker Phase IOutcomes 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
The Next StepSPACE ROBOTICS INITIATIVE
CDR11/18/99-35
Outcomes of Skyworker Phase IOutcomes of Skyworker Phase IOutcomes of Skyworker Phase IOutcomes 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
The Next StepSPACE ROBOTICS INITIATIVE
CDR11/18/99-36
Skyworker Phase II - RobotSkyworker Phase II - RobotSkyworker Phase II - RobotSkyworker 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
The Next StepSPACE ROBOTICS INITIATIVE
CDR11/18/99-37
Skyworker Phase II - SimulatorSkyworker Phase II - SimulatorSkyworker Phase II - SimulatorSkyworker 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
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