Supervisory control of a modular class of discrete event systems based on elementary siphons of Petri nets

We develop a novel deadlock control policy for modeling concurrent execution of manufacturing assembly processes in FMS through 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. Resent work has shown that deadlock situations in terms of an unmarked siphon based on the Petri net models are characterized by the analysis of the system. Our deadlock prevention policy is to make all unmarked siphons satisfy 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 supervisory places are added and unnecessary iterative processes are avoided. Finally, the application of the approach is illustrated with a realistic G-system example.