TRACKING AND ALMOST DISTURBANCE DECOUPLING CONTROL FOR SOME CLASS OF NONLINEAR SYSTEMS WITH MISMATCH UNCERTAINTIES

Abstract

This paper studies the output tracking and almost disturbance decoupling problem for some class of nonlinear control systems with mismatch uncertainties. The main contribution of this study is to construct a controller, under appropriate conditions, such that the resulting closed-loop system is valid for any initial condition and bounded tracking signal with the following characteristics: input-to-state stability with respect to disturbance inputs and almost disturbance decoupling, that is, the influence of disturbances on the L 2 norm of the output tracking error can be arbitrarily attenuated by increasing some adjustable parameters. The fundamental theoretical approaches are the differential geometry approach and the composite Lyapunov approach. One example, which cannot be solved by the first paper on the almost disturbance decoupling problem, is proposed in this paper to exploit the fact that the tracking and almost disturbance decoupling performances are easily achieved by the proposed approach. To demonstrate the practical applicability, this paper has successfully derived tracking and almost disturbance decoupling controller for a famous ball and beam system.