Perfect position/force tracking of robots with dynamical terminal sliding mode control

According to a given performance criteria, perfect tracking is defined as t he performance of zero tracking error in finite time. It is evident that ro botic systems, in particular those that carry out compliant task, can benef it from this performance since perfect tracking of contact forces endows on e or many constrained robot manipulators to interact dexterously with the e nvironment. In this article, a dynamical terminal sliding mode controller t hat guarantees tracking in finite-time of position and force errors is prop osed. The controller renders a dynamic sliding mode for all time and since the equilibrium of the dynamic sliding surface is driven by terminal attrac tors in the position and force controlled subspaces, robust finite-time con vergence for both tracking errors arises. The controller is continuous; thu s chattering is not an issue and the sliding mode condition as well the inv ariance property are explicitly verified. Surprisingly, the structure of th e controller is similar with respect to the infinite-time tracking case, i. e., the asymptotic stability case, and the advantage becomes more evident b ecause terminal stability properties are obtained with the same Lyapunov fu nction of the asymptotic stability case by using more elaborate error manif olds instead of a more complicated control structure. A simulation study sh ows the expected perfect tracking and a discussion is presented. (C) 2001 J ohn Wiley & Sons, Inc.