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Ranger Telerobotic Shuttle Experiment:
Status Report
Gardell G. Gefke, Craig R. Carignan, Brian J. Roberts, and J. Corde Lane
University of Maryland
Space Systems Laboratory
http://www.ssl.umd.edu/
Intelligent Systems and Advanced Manufacturing Conference
Telemanipulators and Telepresence Technologies VIII
28 October 2001
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
Ranger Robotics Program: Status Report
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Space Systems Laboratory
University of Maryland
What are the Unknowns in Space Robotics?
Human Workload
Issues?
Flexible Connections
to Work Site?
Capabilities and
Limitations?
Multi-arm Control and
Operations?
Control Station
Design?
Manipulator
Design?
Interaction with Nonrobot Compatible
Interfaces?
Hazard Detection and
Avoidance?
Utility of
Interchangeable
End Effectors?
Ground-based
Simulation
Technologies?
Effects and Mitigation
of Time Delays?
Ground Control?
Ranger Robotics Program: Status Report
Development,
Production, and
Operating Costs?
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Space Systems Laboratory
University of Maryland
“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
Ranger Robotics Program: Status Report
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Space Systems Laboratory
University of Maryland
Ranger Telerobotic Shuttle eXperiment (RTSX)
• 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 Robotics Program: Status Report
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Space Systems Laboratory
University of Maryland
Ranger’s Place in Space Robotics
How the Robot Interacts with the Worksite
How the Operator Interacts with the Robot
Locally
Teleoperated
Specialized
Robotic
Interfaces
Remote
(Ground)
Teleoperated
SRMS/SSRMS
MFD/SPDM
AERCam
ETS-VII
ROTEX
Sojourner
Any EVACompatible
Interface
Any HumanCompatible
Interface
Ranger Robotics Program: Status Report
Supervisory/
Autonomous
Control
Ranger TSX
Robonaut
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Space Systems Laboratory
University of Maryland
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)
~1500 lbs weight; 14 length from base on SLP
to outstretched arm tip
» 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
Ranger Robotics Program: Status Report
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Space Systems Laboratory
University of Maryland
Robot Stowed Configuration
Ranger Robotics Program: Status Report
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Space Systems Laboratory
University of Maryland
Task Suite
• 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)
• Robotic ORU task
– Remote Power Controller
Module insertion/removal
• Robotic assistance
of EVA
• EVA ORU task
– Articulating Portable
Foot Restraint
setup/tear down
Ranger Robotics Program: Status Report
– HST Electronics
Control Unit
insertion/removal
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Space Systems Laboratory
University of Maryland
End Effectors
Bare Bolt Drive
Right Angle Drive
Microconical
End Effector
Tether Loop
Gripper
EVA Handrail
Gripper
SPAR Gripper
Ranger Robotics Program: Status Report
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Space Systems Laboratory
University of Maryland
Operating Modalities
Video Displays (3)
• Flight Control Station
(FCS)
Keyboard, Monitor,
Graphics Display
– Single console
– Selectable time delay
2x3 DOF
Hand Controllers
» No time delay
» Induced time delay
CPU (Silicon
Graphics O2)
• 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)
Ranger Robotics Program: Status Report
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Space Systems Laboratory
University of Maryland
Ranger Neutral Buoyancy Vehicles
• 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:
– 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
Ranger Robotics Program: Status Report
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Space Systems Laboratory
University of Maryland
Graphical Simulation
Task Simulation
GUI Development
Worksite Analysis
Ranger Robotics Program: Status Report
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Space Systems Laboratory
University of Maryland
Simulation Correlation Strategy
EVA/EVR
Correlation
Simulation
Correlation
All On-Orbit
Operations Performed
Pre/Post Flight with
RTSX Neutral
Buoyancy Vehicle for
Flight/NB Simulation
Correlation
Simulation
Correlation
EVA/EVR
Correlation
Ranger Robotics Program: Status Report
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Space Systems Laboratory
University of Maryland
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
Ranger Robotics Program: Status Report
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Space Systems Laboratory
University of Maryland
Program Status
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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
Ranger Robotics Program: Status Report
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Space Systems Laboratory
University of Maryland
Results of a Successful Ranger TSX Mission
Demonstration of Dexterous
Robotic Capabilities
Precursor for Low-Cost
Free-Flying Servicing Vehicles
Ranger Robotics Program: Status Report
Understanding of Human Factors
Pathfinder for Flight
of Complex Telerobot Control
Testing of Advanced Robotics
Lead-in to Cooperative
EVA/Robotic Work Sites
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Dexterous Robotics for
Advanced Space Science
Space Systems Laboratory
University of Maryland