In: Zhou, M.C.: Petri Nets in Flexible and Agile Automation, pages 239-264. Dordrecht, NL: Kluwer Academic Publishers, 1995.
Abstract: Multiple products through a flexible manufacturing system (FMS) with limited resources can lead to deadlock situation. In this chapter, we study the problem of deadlock avoidance by using the Petri net (PN) model for FMS 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 the deadlock in the system. When the number of any key kind of resources is greater than 1, this policy is minimally restrictive and maximizes the resource usage. We present the Petri net realization of these restriction policies. The Petri net controlled by the policies may be used as the Petri net model for an FMS in which deadlock can never occur. The restriction policies can be easily implemented. Several examples are provided for illustration.
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