Modeling and control of workstation level information flow in FMS using modified Petri nets

A flexible manufacturing system (FMS) has a traditional structure of three levels: cell, workstation, and equipment. The workstation level plays an im portant role in the overall performance of the FMS. This paper focuses on m odeling and control of the FMS workstation level information flow. In order to have a unified workstation level system structure, front-end interfaces are introduced as a standard communication medium between the workstation level and the equipment level. A detailed information flow analysis is then carried out on the workstation level. For modeling purposes, a modified Pe tri net is proposed with its increased modeling capability over an ordinary Petri net. It associates data structures with places and programs with tra nsitions. Finally, the modified Petri net is used to model and control the FMS workstation level information flow. The designed control system has bee n implemented in a real manufacturing factory with satisfactory performance .