Distributed cell controllers using colour Petri-nets and Fieldbus : An application in flexible assembly

Abstract

In this paper, a reference system architecture is presented which utilizes colour Petri-nets (CPNs), a distributed Fieldbus sensory network and the manufacturing message specification (MMS) modelfor the control of the flexible assembly system (FAS)over a distributed communication network.In this architecture, a client and server methodology based on the MMS is utilised where the robots and the conveyor systems are modelled as servers and a CPN based cell controller is modelled as a client which is capable of dispatching the assembly task requirement to the remote devices in a timely, conflict and deadlock free manner. One of the distinct features of the proposed controller is the provision of high level interfaces for the definition and configuration of both the assembly task requirement and the structure of the assembly system. It makes the system highly effective for small batch production where reconfiguration of the physical system is frequently needed. A case study is presented to demonstrate a real application of the proposed system.