Flow optimization method for control synthesis of flexible manufacturing systems modeled by controlled timed Petri nets

A flow optimization method for control synthesis of flexible manufacturing systems modeled by a class of controlled timed Petri nets is presented. A closed-loop control framework, which consists of a controlled Petri net model as plant and a supervisor which controls this plant, is used. This allows external control to be applied to Petri nets for modeling dynamic control strategies. A supervisor is designed using a two-level hierarchical structure: a continuous flow approximation model of a discrete-event system for the optimization of the firing frequencies of transitions in Petri nets, and a real-time firing frequency tracking controller for conflict-solving. A conflict-based method is proposed to decompose the control problems so that a hierarchical decentralized real-time supervisor can be constructed