Scheduling and Re-Scheduling of FMS Using AGVs on the Basis of Petri Net

Abstract

This paper deals with a scheduling and re-scheduling method for flexible manufacturing systems (FMS) using automatically guided vehicles (AGVs) and input-output buffers. The purpose is to solve coordination problems of AGVs transferring jobs between machines so as to minimize idle time of each machine and the total job processing time without collision of AGVs, and quick generation of another substituting effective schedule in the case of troubles of AGVs. A hierachical timed Petri net is applied to modeling and analysis of systems. Two priority functions are defined to effectively determine job processing precedence relationships among machining orders and AGV assignment. Some scheduling simulation results are also shown in this paper.