The Next Step SPACE ROBOTICS INITIATIVE CDR11/18/99-35 RoadmapRoadmap Boards & Buses Communications Sensing Software Goals

The Next StepSPACE ROBOTICS INITIATIVE

CDR11/18/99-1

RoadmapRoadmapRoadmapRoadmap

• Boards & Buses

• Communications

• Sensing

• Software

• Goals


CDR11/18/99-2

Electronics Overview


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


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


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)


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


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


CDR11/18/99-8

Control LayersControl LayersControl LayersControl Layers


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


CDR11/18/99-10

Force Torque Sensor PlacementForce Torque Sensor PlacementForce Torque Sensor PlacementForce Torque Sensor Placement


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


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


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


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


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


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


CDR11/18/99-17

Communication LayersCommunication LayersCommunication LayersCommunication Layers


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


CDR11/18/99-19

Software BlueprintSoftware BlueprintSoftware BlueprintSoftware Blueprint


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


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.


CDR11/18/99-22

Sky ScriptSky ScriptSky ScriptSky Script

• Tool for developing high-level scripts to coordinate various Skyworker actions


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


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


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


CDR11/18/99-26

D-H ModelD-H ModelD-H ModelD-H Model

Gripper A holding structure


CDR11/18/99-27

D-H ModelD-H ModelD-H ModelD-H Model

Gripper B holding structure


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


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


CDR11/18/99-30

Software ProgressSoftware ProgressSoftware ProgressSoftware Progress


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


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


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


CDR11/18/99-34


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


CDR11/18/99-35


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


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


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

Documents

The Next Step SPACE ROBOTICS INITIATIVE CDR11/18/99-35 RoadmapRoadmap Boards & Buses Communications Sensing Software Goals