We consider a reliable decentralized supervisory control problem for discrete event systems in the inference-based framework. This problem requires us to synthesize local supervisors such that the controlled system achieves the specification and is nonblocking, even if local control decisions of some local supervisors are not available for making the global control decision. In the case of single-level inference, we introduce a notion of reliable 1-inference-observability and show that reliable 1-inference-observability together with controllability and Lm(G)-closedness is a necessary and sufficient condition for the existence of a solution to the reliable decentralized supervisory control problem.

In this paper, we introduce conditional decisions for enforcing forcible events in the decentralized supervisory control framework for timed discrete event systems. We first present sufficient conditions for the existence of a decentralized supervisor with conditional decisions. These sufficient conditions are weaker than the necessary and sufficient conditions for the existence of a decentralized supervisor without conditional decisions. We next show that the presented sufficient conditions are also necessary under the assumption that if the occurrence of the event tick, which represents the passage of one time unit, is illegal, then a legal forcible event that should be forced to occur uniquely exists. In addition, we develop a method for verifying the presented conditions under the same assumption.

The conventional decentralized supervisory control architectures for discrete event systems assume that default control of controllable events is static. In this paper, we propose a new decentralized supervisory control architecture using dynamic default control of controllable events. We present necessary and sufficient conditions for the existence of a decentralized supervisor in the proposed architecture. Then, we give an example of a language that is achieved in the proposed architecture, but not in the conventional architectures using static default control.

In this paper, we study reliable decentralized supervisory control of discrete event systems with a control architecture where certain controllable events are controlled under the conjunctive fusion rule, and certain others are controlled under the disjunctive fusion rule. We first introduce a notion of reliable co-observability with respect to such a partition of the controllable event set. We then prove that reliable co-observability together with Lm(G)-closure and controllability is a necessary and sufficient condition for the existence of a reliable decentralized supervisor under a given partition. Moreover, we present necessary and sufficient conditions for the existence of a partition of the controllable event set under which a given specification language is reliably co-observable.

This paper deals with the decentralized supervisory control problems of uncertain discrete event systems which are represented as a set of some possible models. For a given global specification, this paper provides the necessary and sufficient conditions for the existence of local supervisors to achieve the specification under model uncertainty.

We consider a discrete event system controlled by a decentralized supervisor consisting of n local supervisors. Given a nonempty and closed language as the upper bound specification, we consider a problem to synthesize a reliable decentralized supervisor such that the closed-loop behavior is still legal under possible failures of any less than or equal to n-k (1 k n) local supervisors. We synthesize two such reliable decentralized supervisors. One is synthesized based on a suitably defined normal sublanguage. The other is the fully decentralized supervisor induced by a suitably defined centralized supervisor. We then show that the generated languages under the control actions of these two decentralized supervisors are incomparable.

In this paper, we study decentralized supervisory control of discrete event systems where local disabling actions are fused by the OR rule. We generalize an on-line procedure for synthesizing decentralized supervisors proposed by Prosser. By using the generalized procedure, we can achieve a sublanguage of a specification which is not achieved by a class of decentralized supervisors synthesized by the Prosser's procedure.

The supervisory control theory of discrete event dynamic systems was proposed in the framework of automata and formal languages. The concept of decentralized supervisory control was developed for the local supervisor Si whose concurrent operation results in the closed-loop language L (Si/G) equal to that of global supervisor, L (S/G). In this letter we extend this concept by considering the problem of optinal combination of decentralized with centralized control in case pure decentralized control happens to be inadequate. We introduce the concept of locally controllable complementary tuple and present an analytical framework for nonhomogeneous decentralized supervisory control systems.