Near-Minimum Time Feedback Controller for Manipulators Using On-Line Time Scaling of Trajectories

[+] Author and Article Information
A. Kumagai

United Technologies, Automotive, Huntington, IN 46750

D. Kohli, R. Perez

University of Wisconsin—Milwaukee, Mechanical Engineering Department, Milwaukee, WI 53201

J. Dyn. Sys., Meas., Control 118(2), 300-308 (Jun 01, 1996) (9 pages) doi:10.1115/1.2802318 History: Received December 01, 1993; Revised April 01, 1995; Online December 03, 2007


A near-minimum time feedback controller for robotic manipulators with bounded input torques is developed. Since the bang-bang input torque obtained from the timeoptimal control theory leaves little or no room for the extra torque of the feedback control action, it is difficult to combine a minimum time open-loop controller with an additional feedback controller. A simple solution to this problem has been to solve the minimum time problem using arbitrarily reduced torque bounds so that a torque head room is created for the feedback control action. Such a scheme, however, wastes considerable input torque potential and gives significantly larger execution time of the trajectory than the theoretical minimum time calculated from the time-optimal control theory. A stable feedback controller is developed in this paper which applies a time scaling method to move a manipulator in near-minimum time using the allowable input torques efficiently. This new feedback controller algorithm adapts to an uncertain environment and automatically adjusts the desired speed along a specified path to be as fast as possible while avoiding the velocity saturation condition. Numerical examples of the near-minimum time feedback controller are provided using a two-link SCARA manipulator.

Copyright © 1996 by The American Society of Mechanical Engineers
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