Output feedback control for fuzzy systems with immeasurable premise variables

This paper is concerned with the output feedback control for fuzzy systems with immeasurable premise variables. When we consider a fuzzy system, the selection of the premise variable is important. If it is the state of the system, a fuzzy system describes a wide class of nonlinear systems. However, the state is not measurable in the output feedback control problem. Hence, the premise variable is not unknown. In this case, the separation principle, in general, does not hold. This causes a difficulty in control design. In order to overcome this difficulty, a new approach to the output feedback control is introduced. Our approach converts the output feedback stabilization into the H_infin control problem where the terms related to the premise variable is considered an unknown signal. The method does not only stabilizes the system but also takes care of the control performance. A numerical example is given to show the effectiveness of our output feedback control.