Supervisory Policies for Flexible Manufacturing Systems

This paper focuses on a method for synthesizing deadlock avoidance controllers in flexible manufacturing systems. The modelling process of a supervisory policy that enforces liveness is realized with Petri nets. Petri nets are a popular modelling paradigm for a wide class of discrete event systems. Our supervisory policy is based on the next two steps in modelling process: a) A bottom-up approach for the synthesis of a controlled Petri net model for the production flow; b) A liveness condition for the above mentioned model, under the circumstances of underlying the potential peril path (PPP) in the Petri net model by respecting the concept of minimal resource requirements. While the deadlock avoidance controller ensures the liveness of the global Petri net model (GPN) of the FMS, an algorithm for estimating the system throughput is introduced. The utility of our approach in alleviating the computational burden of policy synthesis is illustrated via example.