Contents I. Introduction
IN THE PAST few years, there has been a rapidly growing interest in the fuzzy control of nonlinear systems, and there have been many successful applications. In particular, the control technique based on the so-called Takagi–Sugeno (T–S) fuzzy model [1] has recently attracted lots of attention [2]–[14], since it is regarded as a powerful solution to bridge the gap between the fruitful linear control and the fuzzy logic control targeting complex nonlinear systems. The common practice is as follows. First, the T–S fuzzy model is used to represent or approximate a nonlinear system. This fuzzy model is described by a family of fuzzy IF–THEN rules which represent the local linear input–output relations of the system. The overall fuzzy model of the system is achieved by smoothly blending these local linear models together through the membership functions. Then, based on this fuzzy model, the control design is worked out by taking full advantage of the strength of modern linear control theory. As a common belief, this technique is conceptually simple and effective for controlling complex nonlinear systems. Moreover, it has been proven that a linear T–S fuzzy model is a universal approximator of any smooth nonlinear system on a compact set [14].
