Fuzzy logic and controller design-a review

Abstract

Fuzzy controllers have been proposed for physical systems which do not lend themselves to easy and accurate mathematical modeling and crisp variables, and therefore, cannot be tackled by traditional strictly analytic control design techniques. Instead, control variables are represented by fuzzy variables which let the level of uncertainty of the variables be modeled in a systematic way. In addition the expert knowledge of a typical operator of such a process is embodied in a set of linguistic or rule-based engines which constitutes the core of a fuzzy controller. The magical advantages of fuzzy controllers over the classical ones have been demonstrated by recent results in diverse application domains as well as the surge of commercial products to worldwide consumer market. Thus, the control engineering research, education, and practice have to be revised accordingly. Fortunately, this area finally found its long-expected place in academia and industry, after its first introduction about thirty years ago. Recently, there have emerged many fuzzy logic software and hardware products. The objective in this paper is to give a comparative review of these resources and techniques, and introduce the reader to the state of knowledge in fuzzy controller design research and education. Subjects such as fuzzy set theory, fuzzy logic, fuzzy ruled based expert systems, intelligent control, and fuzzy control will be studied. A number of case studies and applications of fuzzy controls, and some fuzzy logic hardware and software tools are pointed out.