Chattering-free fuzzy sliding mode control in MIMO uncertain systems

Control of nonlinear multivariable systems is very challenging in the area of systems and control. This paper is concerned with a framework that unifies sliding mode control (SMC) and fuzzy logic control (FLC). Based on the combination of the SMC with fuzzy control, this paper presents a new and feasible design algorithm to synthesize a robust fuzzy sliding mode controller which can easily tackle the stabilizing and tracking problem of a class of MIMO nonlinear systems in the presence of uncertainties and external disturbance. A practical design that combines a fuzzy technique with SMC to enhance robustness and sliding performance in a class of uncertain MIMO nonlinear systems is proposed. Using a fuzzy scheme, a Fuzzy Sliding Mode Controller (FSMC) is used to approximate the hitting control in the neighborhood of the sliding manifold. The main contribution of the proposed method is that the structure of the controlled system is partially unknown and does not require the bounds of uncertainty and disturbance of the system to be known: meanwhile, the chattering phenomenon that frequently appears in the conventional variable structure systems is also eliminated without deteriorating the system robustness. A series of computer simulations are included to verify the effectiveness of the proposed design algorithm. (C) 2009 Elsevier Ltd. All rights reserved.