Decentralized Diagnosis of Fuzzy Discrete-Event Systems

In order to more effectively cope with the real-world problems of vagueness, impreciseness, and subjectivity, fuzzy discrete-event systems (FDESs) were proposed by Lin and Ying [12]. Recently, an approach of centralized diagnosis for FDESs was presented by the first author and Qiu [15]. As a continuation, this paper aims to extend it to the decentralized framework. We formalize the notion of codiagnosability for decentralized diagnosis of FDESs, in which the observability of fuzzy events is defined to be fuzzy instead of crisp. The codiagnosability of an FDES is a necessary but not sufficient condition of its diagnosability. A codiagnosable FDES is required that each failure can be detected by at least one local fuzzy diagnoser within a finite delay based on the observability of fuzzy event strings. From a given FDES, we construct a codiagnoser to perform the decentralized diagnosis, each component of which carries out the local detection based on its local observation. In particular, a necessary and sufficient condition for the codiagnosability of FDESs is presented. In addition, some examples are provided to illustrate the main results.