REAL-TIME PETRI NETS FOR MODELING, CONTROLLING, AND SIMULATION OF LOCAL-AREA NETWORKS IN FLEXIBLE MANUFACTURING SYSTEMS

Flexible manufacturing systems (FMSs) are advanced manufacturing systems consisting of machining cells, robots, and automated guided vehicles (AGVs) that function under the hierarchical control of computers. The flexibility of an FMS is primarily imparted by integrating the functions of different system elements such as machining cells, robots, and AGVs using computers. Hence, the communication among computers, machining cells, robots, and AGVs in the FMS is important to realize the full benefits of FMSs. Despite the abundant literature on factory communications there is a need for integrated tools to model communication networks in FMS that can be used for both performance evaluation and real-time control. In this paper, the role of local area networks (LANs) in FMSs is explicated. The contribution of this paper is two-fold. With this aim first, the differences between the LANs in conventional computer systems to that of LANs in FMSs are emphasized. Secondly, Real-time PNs are demonstrated as an integrated modeling tool for LAN in FMS. A software package has been developed to simulate the Petri net models (PNMs). The software package developed aids system designers by simulating the PNM and generating certain performance criteria. Furthermore, the same package assists control engineers for the real-time control of the system designed by system designers.