Stepwise scheduling for AGVs in FMSs

The scheduling for AGVs is always a complicated and important issue in FMS. In this paper, a stepwise AGV scheduling method is presented. According to this measure, the AGV scheduling process is composed of a rough schedule and a final schedule. The rough one gives AGVs rough tasks following upper planning. The finer one completes in-depth task analysis and division under resource constraints. The final one tries to fulfil the AGV subtasks and approach ultimate control. Of these 3 steps, the finer schedule is the most essential and complex one. To make it easier, decisionable extended Petri nets (DEPNs) are suggested. DEPNs enhance the ability of PNs in that they can describe processes with time delay and make decision making possible with a concise model. By means of running the DEPN model, the process of AGV finer scheduling can be performed. The application of this stepwise AGV scheduling to a real FMS(SJ-FRMS) is illustrated and the results are satisfied