Indirect adaptive fuzzy sliding mode control: Part I: fuzzy switching

In this paper, by using the concept of sliding mode control design and Lyap unov synthesis approach, we propose an indirect adaptive fuzzy sliding mode control (IAFSMC) scheme for a class of nonlinear systems. In contrast to t he existing sliding mode fuzzy control system designs, where the sliding mo de control law is directly substituted by a fuzzy controller, in our approa ch both the equivalent control term and switching-type control term in the sliding mode control law are approximated by fuzzy systems, respectively. A n on-line adaptive tuning algorithm for the consequent parameters in the fu zzy rules is also designed. The sliding mode-based design procedure ensures the stability and robustness of the proposed IAFSMC. We prove that the pro posed adaptive scheme can achieve asymptotically stable tracking of a refer ence input with a guarantee of the bounded system signals. The chattering p henomena in the sliding mode control is attenuated and the steady error is also alleviated. Simulation studies have shown that the presented adaptive design of fuzzy sliding mode controller performs very well in the presence of an unknown disturbance. (C) 2001 Elsevier Science B.V. All rights reserv ed.