An efficient deadlock avoidance control policy in FMS using structural analysis of Petri nets

The aim of this paper is to cope with deadlocks occurring in FMS where different sequential processes share many distinct resources. The Petri net model of the class of FMS considered is a bounded asymmetric choice net called PAC net. In this paper, we propose a deadlock avoidance control policy based on the structural analysis of Petri nets. Our method first adds the “local control places” to ensure that the minimal deadlocks which are not trapped remain always marked. We then prove that the restriction of the augmented net´s evolution to safe markings (states) is sufficient to avoid any global deadlock. The safety property is defined in terms of a marking condition on the “local control places” and the principle of the method “never grant a resource that takes the system from a safe to an unsafe state” is easy to implement