THEORETICAL AND LINGUISTIC ASPECTS OF THE FUZZY LOGIC-CONTROLLER

Successful applications of the fuzzy logic controller by various researchers to a variety of ill-defined processes motivated this theoretical study of the fuzzy logic controller. Initially the controller is analysed by traditional (nonlinear) algebraic methods which are particularly useful in stability studies, provided the process is algebraically modelled. Despite the success of this technique, it suffers from a major limitation in that the algebraic model of the controller cannot directly deal with the linguistic aspects of the fuzzy logic controller. This observation leads to the introduction of a more concise, and hence more powerful, notation for representing the linguistic rules that describe the fuzzy logic controller. The so-called linguistic models that arise from this notation are shown to be extremely useful for modelling highly nonlinear low-order systems and for determining, explicitly, the rules of 'optimal' fuzzy logic controllers. © 1979.