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Space Systems Lab
University of Maryland

Compliance Control for the
Ranger Dexterous Manipulator


Contact:
Enrico Sabelli
Graduate Research Assistant

Robots intended for space manipulation tasks must be carefully designed for precision and dexterity. The robot's control scheme must be capable of stiff, accurate positioning, while at the same time remaining flexible enough so that contacts are made softly. Unfortunately, the environment with which manipulators interact is often uncharacterized. A space manipulator must be robust enough to perform accurately and delicately in a variety of unpredictable circumstances. Hence, one of the objectives of space manipulator control is to ensure that the manipulator reacts stably to contact with an unknown environment.

The Ranger manipulator was developed by the Space Systems Laboratory at the University of Maryland as their research test bed for robotic manipulation both in neutral buoyancy and on dry land. To address the issue of compliance, an impedance/admittance controller has been developed by Dr. Craig Carignan that allows the manipulator endpoint to behave as a spring-dashpot system. When an external tooltip force is sensed, the manipulator modifies its intended trajectory and recoils in order to lessen the contact force. Until now, the impedance parameters (mass, stiffness and damping) of this controller have not been fully characterized for Ranger. The goal of this research is thus to determine suitable controller gains and demonstrate stable contact during simple manipulator tasks.

Project advisor:
Dr. David Akin
Lead graduate student:
Enrico Sabelli


Acknowledgements
Compliance Control for the Ranger Dexterous Manipulator is under development at the University of Maryland Space Systems Laboratory, part of the Aerospace Engineering Department and the A. James Clark School of Engineering. Funding is provided through the Institute for Dexterous Space Robotics

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