A deadlock prevention policy for FMS based on time constraints

To solve the problem of deadlock for flexible manufacturing systems (FMS), an effective deadlock prevention policy based on time constraints is presented in this paper. The proposed approach is for a special class of Petri nets, named S³PR. Reachability analysis is a fundamental method applied widely into analyzing Petri nets model. The deadlock-freedom is achieved by preventing the system from reaching the bad, deadlock markings and local isolated loops (LIL). By time constraints, the firing sequences of transitions are restricted to avoid the system entering the forbidden states. Compared with the traditional deadlock control policies, the controlled net by the presented method has simpler structure. Finally, an example is used to demonstrate the applications of the proposed approach.