Fuzzy controller with stability and performance rules for nonlinear systems

This paper presents a fuzzy controller which can be designed through two steps for nonlinear systems. The proposed fuzzy controller consists of two groups of fuzzy rules, namely the stability and performance rules. Stability conditions which involve the stability rules only will be derived to guarantee the system stability. By properly designing the shapes of the membership functions of the fuzzy controller, the stability conditions can be relaxed. The proposed fuzzy controller offers a property that the performance rules will not alter the system stability. This favorable property enables the performance rules to be designed freely to achieve the system performance without affecting the system stability. Consequently, the system stability and performance can be designed in two separate processes. An application example will be presented to show the merits of the proposed approach.