On supervisor synthesis of discrete event systems

In this paper we propose a deadlock control policy for a class of nets, called G-system with limited shared resources, which is a large class of discrete event systems generalizing well-known models presented in the literature. A relevant property of the system behavior is to be non-blocking, i.e., from any reachable state, a desirable state can be always obtained under supervision. The analysis of the system leads us to characterize deadlock situations in terms of an unmarked siphon based on the Petri nets model. Our deadlock prevention policy is to make all unmarked siphons satisfying cs-property when all elementary siphons are properly supervised. Compared with the existing policies, the advantage of the policy is that a much smaller number of supervisor places are added and unnecessary iterative processes are avoided. Finally, the application of the approach is illustrated with a realistic G-system example.