Implementation of distributed control architecture for robotic manufacturing systems using Petri nets

Since the large scale and complex manufacturing systems have a hierarchical structure and the controllers are geographically distributed according to their physical structure, it is desirable to realize the hierarchical and distributed control. In this paper, the methods of the modeling and decomposition of the large and complex discrete event manufacturing systems are considered, and a methodology is presented for hierarchical and distributed control, where the cooperation of each controller is implemented so that the behavior of the overall system is not deteriorated and the task specification is completely satisfied. First, the task specification is defined as a Petri net model at the conceptual level, and then transformed to the detailed Petri net representation of manufacturing processes. Finally, the overall Petri net is decomposed and the constituent subnets are assigned to the machine controllers. The machine controllers are coordinated so that the decomposed transitions fire at the same time. System coordination through communication between the coordinator and machine controllers, is presented. Modeling and control of large and complex manufacturing systems can be performed consistently using Petri nets.