The above paper considers the state-feedback control problem of fuzzy discrete-event systems (DESs) (FDESs) and gives a necessary and sufficient condition for the existence of a state-feedback controller. In this correspondence paper, after indicating that the problem under consideration is applicable for general DESs, not limited to FDESs, we show that the condition given in the above paper is not necessary by a counterexample and then provide a necessary and sufficient condition for the existence of a state-feedback controller.

This paper discusses recent applications of fuzzy sets and the theory of approximate reasoning. The primary focus is on fuzzy logic control (FLC). We begin with a brief history of the key ideas, a survey of recent applications, and a discussion of the genesis of FLC in Japan. We then turn to a study of the general principles of FLC, considering it as a combination of ideas from conventional control theory, artificial intelligence, and fuzzy sets theory. We next provide a detailed analysis of a simple application in consumer electronics, namely, a fuzzy washing machine developed by Hitachi Corporation. In concluding sections we briefly consider other types of applications, including recent work on pilotless helicopters, fuzzy expert systems, and the concept of a fuzzy computer, and we discuss the potential for future developments. It is our opinion that the subject of FLC is still very much in its infancy, and that recent events mark the beginning of an entirely new genre of "intelligent" control.>