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Ranger Telerobotics Program. Brian Roberts University of Maryland Space Systems Laboratory http://www.ssl.umd.edu/. On-Orbit Servicing Workshop 14 November 2001. Space Systems Laboratory. 25 years of experience in space systems research

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Ranger Telerobotics Program

Brian Roberts

University of Maryland

Space Systems Laboratory


On-Orbit Servicing Workshop

14 November 2001

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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

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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

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What are the Unknowns in Space Robotics?

Flexible Connections to Work Site?

Capabilities and Limitations?

Human Workload Issues?

Multi-arm Control and Operations?

Control Station Design?

Interaction with Non-robot Compatible Interfaces?


Hazard Detection and Avoidance?

Utility of InterchangeableEnd Effectors?

Development, Production, and Operating Costs?

Ground-based Simulation Technologies?

Effects and Mitigation of Time Delays?

Ground Control?

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Multimode Proximity Operations Device (MPOD)

  • 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

  • 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

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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

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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

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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

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    “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

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    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

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    Ranger’s Place in Space Robotics

    How the Operator Interacts with the Robot

    How the Robot Interacts with the Worksite

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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

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    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

      • Articulating Portable Foot Restraint setup/tear down

    • Non-robotic ORU task

      • HST Electronics Control Unit insertion/removal

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    End Effectors

    Microconical End Effector

    Bare Bolt Drive

    Right Angle Drive

    Tether Loop Gripper

    EVA Handrail Gripper

    SPAR Gripper

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    Operating Modalities

    Video Displays (3)

    • 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)

    Keyboard, Monitor, Graphics Display

    2x3 DOF Hand Controllers

    CPU (Silicon Graphics O2)

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    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:

    • 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

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    Graphical Simulation

    Task Simulation

    GUI Development

    Worksite Analysis

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    Simulation Correlation Strategy



    All On-Orbit

    Operations Performed

    Pre/Post Flight with

    RTSX Neutral

    Buoyancy Vehicle for

    Flight/NB Simulation








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    Arm Evolution

    Roboticus Dexterus

    Roboticus Videus

    Roboticus Grapplus

    BAT Dexterous Arm (5 DOF)

    BAT Tilt & Pan Unit (2 DOF)

    BAT Grapple Arm (0 DOF)

    ca. 1984

    ca. 1984

    ca. 1984

    Ranger Dexterous Arm Mark 1 (7 DOF)

    Ranger Grapple Arm (7 DOF)

    ca. 1994

    ca. 1996

    Ranger Dexterous Arm Mark 2 (8 DOF)

    Ranger Video Arm (7 DOF)

    Ranger Positioning Leg (6 DOF)

    ca. 1996

    ca. 1996

    ca. 1998

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    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

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    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

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    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

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    Results of a Successful Ranger TSX Mission

    Demonstration of DexterousRobotic Capabilities

    Understanding of Human Factorsof Complex Telerobot Control

    Pathfinder for FlightTesting of Advanced Robotics

    Precursor for Low-CostFree-Flying Servicing Vehicles

    Lead-in to CooperativeEVA/Robotic Work Sites

    Dexterous Robotics forAdvanced Space Science