Fuzzy variable structure control.

A new methodology is presented to improve the design and tuning of a fuzzy logic controller (FLC) using variable structure control (VSC) theory. A VSC-type rule base is constructed and the fundamentals of FLC explored quantitatively by VSC theory. A very concise mathematical expression for the FLC is presented, in which the Lyapunov stability criterion can be applied to guide the design and tuning. This results in a simpler and more systematic procedure. Application of the method to higher order systems is made straight forward by applying a hierarchical technique. The validity of the design methodology is demonstrated by simulation.