Carnegie Mellon University
A Composite Discrete/Continuous Control of Robot Manipulators

Ju-Jang Lee and Yangsheng Xu
tech. report CMU-RI-TR-91-09, Robotics Institute, Carnegie Mellon University, April, 1991

  • Adobe portable document format (pdf) (719KB)
Copyright notice: This material is presented to ensure timely dissemination of scholarly and technical work. Copyright and all rights therein are retained by authors or by other copyright holders. All persons copying this information are expected to adhere to the terms and constraints invoked by each author's copyright. These works may not be reposted without the explicit permission of the copyright holder.

In this report, a composite control scheme for the control of robot manipulators is proposed.

Due to the modeling error or environmental uncertainties, robot motion may present a significant positioning error by using a conventional Computer-Torque Method. To improve tracking capability of robot manipulators, sliding mode control and nonlinear control algorithms have been introduced, but computation is costly, and thus a fast motion execution using simple computer sources is impossible.

To solve this problem, we present a composite control algorithm to control robot motion combining a discrete feedforward component and a continuous feedback component. The discrete feedforward component provides a nominal torque computed using the robot dynamics and compensates for dynamic coupling between the links. This part can be updated in a large sampling time, and can be computed off-line generally, thus real time computation is decreased. The continuous feedback control component uses a structure of Variable Structure System and provides a robust control to disturbances during the sliding mode. This part can be digitally implemented using a short sampling time, and thus a fast motion of a multi-degree freedom robot manipulator can be executed by using a simple computer, or even a single board computer with an 8-bit CPU.

The stability of the proposed multiple-rate control scheme is proven in the paper and efficiency of the control scheme has been demonstrated by simulations of a three-link robot subject to parameter and payload uncertainties.

Grant ID: N00014-81-0503, N00014-90-J-1656
Associated Center(s) / Consortia: Vision and Autonomous Systems Center
Number of pages: 24

Text Reference
Ju-Jang Lee and Yangsheng Xu, "A Composite Discrete/Continuous Control of Robot Manipulators," tech. report CMU-RI-TR-91-09, Robotics Institute, Carnegie Mellon University, April, 1991

BibTeX Reference
   author = "Ju-Jang Lee and Yangsheng Xu",
   title = "A Composite Discrete/Continuous Control of Robot Manipulators",
   booktitle = "",
   institution = "Robotics Institute",
   month = "April",
   year = "1991",
   number= "CMU-RI-TR-91-09",
   address= "Pittsburgh, PA",