Building AGV traffic-control models with place-transition nets

Owing to the lack of robust design and control algorithms, most current applications of automated guided vehicle systems (AGVSs) employ simple control methods despite the fact that the system is far from efficient. Recently, Petri nets have evolved into a powerful tool for modelling complex manufacturing systems. One of the advantages of the use of Petri nets is that analysis, simulation and on-line control can all be done on the same model once the model is built. The purpose of this paper is to establish the research fundamentals in the field of the Petri-net modelling of an AGVS. The main contribution of the paper is to define basic traffic-control nets which can be used directly to model an AGVS without too much thinking. Some basic AGV Petri-net control elements are described and illustrated in detail. Also, difficulties in the use of bidirectional flows are discussed, and it has been determined how Petri nets can be used to solve these problems.