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We consider Petri net models of discrete event systems with faulty behaviors which are triggered by the firing of failure transitions. We extend a necessary and sufficient, condition for diagnosability shown by Sampath et al. to unbounded Petri nets. But it is algorithmically impossible to check the condition in general. We introiduce methods for modification of coverability trees in order to detect failure transitions. By using such approximated sets, we propose two kinds of diagnosers called a difference marking wdiagncser and an w-refined diagncser. For o b servable places whose token numbers are replaced by w in the coverability trees, the former diagnoser calculates difference between token numbers before and after partially observed markings change, and detects failures. In the latter diagnoser, we refine the symbol w, and modify the coverability tree in order to distinguish markings reachable by normal behaviors from those reachable by faulty behaviors.

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This paper proposes an observer-based approach to synthesis of synchronized chaotic systems. We consider a linear system with nonlinear feedback which exhibits chaos. Using an observer for the linear system, we design synchronized chaotic systems. Moreover, we introduce a new concept of synchronization called (M, c)-synchronization. We also propose a synthesis method for (M, c)-synchronized systems by modifying the observer-based method.

785conjunction with a low power consumption (7 mW). Thus, it can constitute an elegant solution to implement the IF stages required in numerous wireless equipment [11] as it necessitates one active element and few passive components only.Abstract-Delayed feedback control (DFC), proposed by Pyragas, is one of useful control methods for chaotic systems. However, this static DFC has a limitation such that it can not stabilize any systems with an odd number of real eigenvalues greater than unity. In this paper, to overcome the limitation we introduce dynamic delayed feedback, and derive a necessary and sufficient condition for stabilization of such chaotic systems. Moreover, it is shown that the order of the dynamic delayed feedback controller is not necessarily greater than that of the chaotic system. Furthermore, we show a method of designing reduced-order controllers which is based on the linear matrix inequalities.Index Terms-Control of chaos, delayed feedback, linear matrix inequality, stabilization. Publisher Item Identifier S 1057-7122(01)04284-2.