Fuzzy adaptive output tracking control of nonlinear systems

In this paper, a stable adaptive fuzzy output tracking control scheme is developed for a single-input-single-output unknown nonlinear system which can be represented globally by an input-output model. The main characteristics of the proposed adaptive fuzzy control are (i) it does not need the assumption that all the states of the system are available for full feedback, but introduces a high gain observer to estimate them. (ii) It is composed of a robust control term and an equivalence fuzzy control so that it not only ensures the stability of closed-loop system, but also attenuates the effect of fuzzy approximation error on the tracking error of the system to arbitrary small level. (iii) It is proved that the designed output feedback adaptive fuzzy control can recover the performance achieved under the state feedback controller. (C) 2000 Published by Elsevier Science B.V. All rights reserved.