Deadlock avoidance policy for petri-net modeling of flexible manufacturing systems with shared resources

Multiple products through a flexible manufacturing system (FMS) with limited resources can lead to deadlock. In this paper, we study the problem of deadlock avoidance by using the Petri net (PN) model for FMS's and introducing the concept of deadlock structure. The necessary and sufficient conditions to prevent deadlock are characterized, We use a state feedback restriction policy which prevents some enabled transitions from firing for avoiding deadlock in the system. In particular, when the number of any key kind of resources is greater than one, this policy is minimally restrictive and allows the maximal use of resources in the system, We present the PN realization of these restriction policies when the closed-loop system can be modeled by a live PN. The restriction policies can be easily implemented, An example is provided for illustration.