Brian Roberts University of Maryland Space Systems Laboratory Ranger Telerobotics Program On-Orbit Servicing Workshop 14 November

Brian Roberts

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

Ranger Telerobotics Program

On-Orbit Servicing Workshop

14 November 2001

Space Systems LaboratoryUniversity of Maryland

Space Systems Laboratory• 25 years of experience in space systems research • Focus is to develop and test complete systems capable of

performing complex space tasks end-to-end• 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 maximize involvement of students in every level of research activities


SSL Assets for On-Orbit Servicing• Development and testing of

multiple complete robotic systems capable of performing complex space tasks end-to-end:– Docking– Assembly– Inspection– Maintenance

• Facility for evaluating systems in a simulated 6 degree-of-freedom (DOF) microgravity environment

• Expertise:– Autonomous control of multiple robotic systems– Design of dexterous robotic manipulators– Adaptive control techniques for vehicle dynamics– Use of interchangeable end effectors– Investigation of satellite missions benefiting most from robotic servicing


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?


Multimode Proximity Operations Device (MPOD)

• Probe-drogue docking system• Operational since 1986• Achievements:

– Autonomous approach and docking– Maneuvering and berthing of large masses– Application of nonlinear adaptive neural network control system

• System to evaluate controls associated with robotic docking

• Full 6 DOF mobility base

• Full state feedback through an on-board sensor suite, including an acoustic-based sensor system


Supplemental Camera and Maneuvering Platform

• Supplemental Camera and Maneuvering Platform (SCAMP) is a free-flying camera platform– 6 DOF mobility base– Stereo video and close-up color

cameras

• Originally used to observe neutral buoyancy operations

• Evolved to evaluate robotic inspection

• Operational since 1992• Achievements:

– Used routinely to observe robotic and non-robotic neutral buoyancy operations

– Demonstrated visual survey and inspection


SCAMP Space Simulation Vehicle (SSV)• Continuation of SCAMP’s evolution

into a high fidelity neutral buoyancy simulation of 6 DOF space flight dynamics– Uses onboard sensors (3-axis gyros,

accelerometers, magnetometers, and a 3-D acoustic positioning system) to accurately calculate its position, attitude, and translational and rotational velocities

– Robot is positioned to a specified location, determined by a mathematical computer simulation

• Operational since 1997• Achievements:

– Cancellation of water drag effects for flight dynamics– Model-referenced vehicle flight control– Adaptive control of unknown docked payloads– Autonomous docking– Different methods of trajectory planning are being investigated


Beam Assembly Teleoperator (BAT)• Free-flying robotic system to demonstrate assembly of an

existing space structure not robot friendly:– 6 DOF mobility base– 5 DOF dexterous assembly manipulator– Two pairs of stereo monochrome video cameras – Non-articulated grappling arm for grasping the

structure under assembly– Specialized manipulator for performing the coarse

alignment task for the long struts of the truss assembly

• Operational since 1984

• Achievements:– Combination of simple 1 DOF arm with dexterous 5 DOF manipulator

proved to be a useful approach for assembly of a tetrahedral structure

– Demonstrated utility of small dexterous manipulator to augment larger, less dexterous manipulator

– Assisted in the change out of spacecraft batteries of Hubble Space Telescope


“Ranger” Class 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


• 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

• Non-robotic 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

– Refining hardware– Modifying control algorithms and developing

advanced scripts– Verifying boundary management and computer

control of hazards– Correlating space and neutral buoyancy operations– Supporting development, verification, operational,

and scientific objectives of the RTSX mission– Flight crew training

• 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


Arm Evolution

BAT Dexterous Arm (5 DOF)ca. 1984

Ranger Dexterous Arm Mark 1 (7 DOF)ca. 1994

Ranger Dexterous Arm Mark 2 (8 DOF)ca. 1996

Roboticus Dexterus

BAT Tilt & Pan Unit (2 DOF)ca. 1984

Ranger Video Arm (7 DOF)ca. 1996

Roboticus Videus

BAT Grapple Arm (0 DOF)ca. 1984

Ranger Grapple Arm (7 DOF)ca. 1996

Roboticus Grapplus

Ranger Positioning Leg (6 DOF)ca. 1998


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: Mock-up began operation (62 hours of

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

Mark 2 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


SSL Assets for On-Orbit Servicing• Development and testing of

multiple complete robotic systems capable of performing complex space tasks end-to-end:– Docking: MPOD and Ranger TFX– Assembly: BAT and Ranger– Inspection: SCAMP– Maintenance: Ranger

• Facility for evaluating systems in a simulated 6 DOF microgravity environment

• Expertise:– Autonomous control of multiple robotic systems– Design of dexterous robotic manipulators– Adaptive control techniques for vehicle dynamics– Use of interchangeable end effectors– Investigation of satellite missions benefiting most from robotic servicing


Backup Slides


Robot Stowed Configuration


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


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

Brian Roberts University of Maryland Space Systems Laboratory Ranger Telerobotics Program On-Orbit Servicing Workshop 14 November