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


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Abstract
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.


Notes
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
@techreport{Lee_1991_254,
   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",
}