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Impedance Control Based on a Position Sensor in a Rehabilitation Robot

[+] Author Affiliations
Bongsu Kim, Aurelien Rodot, Ashish D. Deshpande

The University of Texas at Austin, Austin, TX

Paper No. DSCC2014-6258, pp. V003T43A005; 7 pages
  • ASME 2014 Dynamic Systems and Control Conference
  • Volume 3: Industrial Applications; Modeling for Oil and Gas, Control and Validation, Estimation, and Control of Automotive Systems; Multi-Agent and Networked Systems; Control System Design; Physical Human-Robot Interaction; Rehabilitation Robotics; Sensing and Actuation for Control; Biomedical Systems; Time Delay Systems and Stability; Unmanned Ground and Surface Robotics; Vehicle Motion Controls; Vibration Analysis and Isolation; Vibration and Control for Energy Harvesting; Wind Energy
  • San Antonio, Texas, USA, October 22–24, 2014
  • Conference Sponsors: Dynamic Systems and Control Division
  • ISBN: 978-0-7918-4620-9
  • Copyright © 2014 by ASME


We examine the implementation of impedance control based on a position sensor in a wearable robot designed for rehabilitation. The first goal is to achieve the lowest possible impedance for the robot, with only a position sensor and an ON/OFF type pressure sensor, so that it is dynamically transparent to the user. We built a wearable robot for controlling the user’s arm with a brushless DC motor and a two-stage gearing system involving a planetary gearbox and a Capstan drive. We designed and implemented a controller to compensate for the inherent friction and reflected inertia using joint angle feedback from the robot, and for the stiction using the user’s intended direction detected by a pressure sensor. Stability conditions are analyzed first for the robotic system alone and then for the coupled human-robot system. Experiments with the robot show that the apparent impedance was significantly reduced with compensation. Experiments involving free motions driven by a user proved that the user’s physical effort to move the robot is dramatically decreased with compensation, thus making the robot feel lighter to the user.

Copyright © 2014 by ASME
Topics: Sensors , Robots



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