Gardell G. Gefke, Craig R. Carignan, Brian J. Roberts, and J. Corde Lane University of Maryland Space Systems Laboratory Ranger

Gardell G. Gefke, Craig R. Carignan, Brian J. Roberts, and J. Corde Lane

University of MarylandSpace Systems Laboratoryhttp://www.ssl.umd.edu/

Ranger Telerobotic Shuttle Experiment: Status Report

Intelligent Systems and Advanced Manufacturing ConferenceTelemanipulators and Telepresence Technologies VIII

28 October 2001

Space Systems LaboratoryUniversity of Maryland

Ranger Robotics Program: Status Report2

Space Systems Laboratory• 25 years of experience in space systems research • A part of the Aerospace Engineering Department at

University of Maryland• People

– 4 full time faculty– 12 research and technical staff– 18 graduate students– 28 undergraduate students

• Facilities– Neutral Buoyancy Research Facility (25 ft deep x 50 ft in diameter)

» About 150 tests a year» Only neutral buoyancy facility dedicated to basic research and only one

in world located on a university campus» Fabrication capabilities include rapid prototype machine, CNC mill and

lathe for prototype and flight hardware – Class 100,000 controlled work area for flight integration

• Basic tenet is to involve students in every aspect of research



What are the Unknowns in Space Robotics?

Ground Control?

Capabilities and Limitations?

Multi-arm Control and Operations?

Flexible Connections to Work Site?

Interaction with Non-robot Compatible Interfaces?

Effects and Mitigation of Time Delays?

Control Station Design?

Human Workload Issues?

Utility of InterchangeableEnd Effectors?

ManipulatorDesign?

Hazard Detection and Avoidance?

Development, Production, and Operating Costs?Ground-based

Simulation Technologies?



“Ranger” Class Satellite Servicers• Ranger Telerobotic Flight eXperiment (RTFX)

– Free-flight satellite servicer designed in 1993; neutral buoyancy vehicle operational since 1995

– Robotic prototype testbed for satellite inspection, maintenance, refueling, and orbit adjustment

– Demonstrated robotic tasks in neutral buoyancy

» Robotic compatible ORU replacement

» Complete end-to-end connect and disconnect of electrical connector

» Adaptive control for free-flight operation and station keeping

» Two-arm coordinated motion

» Coordinated multi-location control

» Night operations

• With potential Shuttle launch opportunity, RTFX evolved into Ranger Telerobotic Shuttle eXperiment in 1996



• Demonstration of dexterous robotic on-orbit satellite servicing– Robot attached to a Spacelab pallet within the cargo bay of the orbiter

– Task ranging from simple calibration to complex dexterous operations not originally intended for robotic servicing

– Uses interchangeable end effectors designed for different tasks

– Controlled from orbiter and from the ground

• A joint project between NASA’s Office of Space Science (Code S) and the University of Maryland Space Systems Laboratory

• Key team members– UMD - project management, robot, task elements, ground control station

– Payload Systems, Inc. - safety, payload integration, flight control station

– Veridian - system engineering and integration, environmental testing

– NASA/JSC - environmental testing

Ranger Telerobotic Shuttle eXperiment (RTSX)



LocallyTeleoperated

Remote(Ground)

Teleoperated

Supervisory/Autonomous

Control

SpecializedRobotic

Interfaces

SRMS/SSRMSMFD/SPDMAERCam

ETS-VIIROTEX

Sojourner

Any EVA-Compatible

InterfaceRanger TSX

Any Human-Compatible

InterfaceRobonaut

Ranger’s Place in Space RoboticsHow the Operator Interacts with the Robot

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Robot Characteristics• Body

– Internal: main computers and power distribution

– External: end effector storage and anchor for launch restraints

• Head = 12 cube

• Four manipulators– Two dexterous manipulators

(5.5 in diameter; 48 long)

» 8 DOF (R-P-R-P-R-P-Y-R)

» 30 lb of force and 30 ft-lbf of torque at end point

– Video manipulator (55 long)

» 7 DOF (R-P-R-P-R-P-R)

» Stereo video camera at distal end

– Positioning leg (75 long)

» 6 DOF (R-P-R-P-R-P)

» 25 lb of force and 200 ft-lbf of torque; can withstand 250 lbf at full extension while braked

~1500 lbs weight; 14 length from base on SLP to outstretched arm tip



Robot Stowed Configuration



• Fiduciary tasks– Static force compliance task

(spring plate)

– Dynamic force-compliant control over complex trajectory (contour task)

– High-precision endpoint control (peg-in-hole task)

Task Suite

• Robotic assistance of EVA

– Articulating Portable Foot Restraint setup/tear down

• EVA ORU task– HST Electronics

Control Unit insertion/removal

• Robotic ORU task– Remote Power Controller

Module insertion/removal



End Effectors

Microconical End Effector

Bare Bolt Drive

EVA Handrail Gripper

Tether Loop Gripper SPAR Gripper

Right Angle Drive



Operating Modalities

• Flight Control Station (FCS)– Single console– Selectable time delay

» No time delay» Induced time delay

• Ground Control Station– Multiple consoles– Communication time delay

for all operations– Multiple user interfaces

» FCS equivalent interface» Advanced control station

interfaces (3-axis joysticks, 3-D position trackers, mechanical mini-masters, and force balls)

CPU (Silicon Graphics O2)

Keyboard, Monitor, Graphics Display

2x3 DOF Hand Controllers

Video Displays (3)



• Neutral Buoyancy Vehicle I (RNBV I)– Free-flight prototype vehicle operational since 1995

– Used to simulate RTSX tasks and provide preliminary data until RNBVII becomes operational

• RNBV II is a fully-functional, powered engineering test unit for the RTSX flight robot. It is used for:

Ranger Neutral Buoyancy Vehicles

– Supporting development, verification, operational, and scientific objectives of the RTSX mission

– Flight crew training

– Developing advanced scripts

– Refining hardware

– Modifying control algorithms

– Verifying boundary management and computer control of hazards

– Correlating space and neutral buoyancy operations

• An articulated non-powered mock-up is used for hardware refinement and contingency EVA training



Graphical Simulation

Task Simulation

Worksite Analysis

GUI Development



Simulation Correlation Strategy

SimulationCorrelation

EVA/EVRCorrelation

SimulationCorrelation

EVA/EVRCorrelation

All On-OrbitOperations Performed

Pre/Post Flight withRTSX Neutral

Buoyancy Vehicle for Flight/NB Simulation

Correlation

All On-OrbitOperations Performed

Pre/Post Flight withRTSX Neutral

Buoyancy Vehicle for Flight/NB Simulation

Correlation



Computer Control of Hazards

• Human response is inadequate to respond to the robot’s speed, complex motions, and multiple degrees of freedom

• Onboard boundary management algorithms keep robot from exceeding safe operational envelope regardless of commanded input



Program Status

• 1995: RNBV I operations began at the NBRF• 1996: Ranger TSX development began• June 1999: Ranger TSX critical design review • December 1999: Space Shuttle Program Phase 2

Payload Safety Review• April 2000: EVA mock-up began operation (62 hours of

underwater test time on 45 separate dives to date)• October 2001: Prototype positioning leg pitch joint and

dexterous arm wrist began testing• Today: RNBV II is being integrated; 75% of the flight

robot is procured• January 2002: RNBV II operations planned to begin• Ranger TSX is #1 cargo bay payload for NASA’s Office

of Space Science and #2 on Space Shuttle Program’s cargo bay priority list



Results of a Successful Ranger TSX Mission

Demonstration of DexterousRobotic Capabilities

Pathfinder for FlightTesting of Advanced Robotics

Dexterous Robotics forAdvanced Space Science

Precursor for Low-CostFree-Flying Servicing Vehicles

Understanding of Human Factorsof Complex Telerobot Control

Lead-in to CooperativeEVA/Robotic Work Sites

Documents

Gardell G. Gefke, Craig R. Carignan, Brian J. Roberts, and J. Corde Lane University of Maryland Space Systems Laboratory Ranger