A Class of Quasi-Natural Potentials for Robot Servo-Loops and its Role in Adaptive and Learning Controls

Abstract

ABSTRACTA new type of saturated position (Proportional) and velocity (Differential) feedback (SPD servo-loop) induced by a quasi-natural potential is proposed for control of robot manipulators with all revolute-type joints. If the servo loop is composed of such SP-D feedback, then not only the original robot dynamics but also the residual error dynamics satisfy the passivity with appropriate choice of feedback gains. By virtue of the passivity, it is possible to show the existence of Lyapunov functions in a global sense for a variety of set-point, adaptive trajectory tracking, and learning controls. Proofs of convergence of tracking errors in model-based adaptive control and learning control are given on the basis of construction of such Lyapunov functions.