ROBUST INDEPENDENT JOINT CONTROLLER-DESIGN FOR INDUSTRIAL ROBOT MANIPULATORS

The independent joint control approach to robot manipulator control is very useful for simplifying controller implementation. The key issues involved in such an approach is the suppression of disturbance at each robot joint due to dynamic coupling, friction, and gravity loading. In this paper, a novel approach is presented for the design of simple robust independent joint controllers for industrial robot manipulators. In this approach, each joint actuator is treated as a simple inertial system plus a disturbance torque representing all the unmodeled dynamics. By a very simple algorithm, the disturbance is instantly estimated and rejected, thus allowing a simple PD control scheme to be used. Stability of the proposed control law is analyzed. Experimental evaluations of the proposed controller on a microcomputer-controlled PUMA 560 arm are performed. It is shown that the control scheme is simple and practical and that it can be easily implemented on an industrial manipulator presently in use.