H∞ Output Feedback Control of Fuzzy Systems with Immeasurable Premise Variables

This paper is concerned with an H_infin output feedback control of Takagi-Sugeno fuzzy systems with immeasurable premise variables. Takagi-Sugeno fuzzy systems can usually approximate nonlinear systems and can even describe a certain class of nonlinear system exactly. When we consider the output feedback control of Takagi-Sugeno fuzzy systems, the selection of premise variables plays an important role. If the premise variable is the state of the system, then a fuzzy system describes a wide class of nonlinear systems. However, the state is not measurable in the output feedback control problem. In this case, a control design of the underlying nonlinear system based on its fuzzy system description is difficult. In this paper, we consider an H _infin output feedback control problem. In this problem, the premise variable may not be measurable. Thus we formulate an H_infin output feedback control problem of fuzzy systems as a robust H_infin control of uncertain systems. Numerical examples are given to illustrate our theory