AGV systems with multi-load carriers: Basic issues and potential benefits

An alternative to increasing automated guided vehicle (AGV) fleet size to improve vehicle availability for material transport requests is to introduce vehicles with multiple load-carrying capacities. Aside from alleviating communication and congestion problems, the use of multiple-load carriers can potentially reduce the deadhead or unproductive time of vehicles. This paper discusses several key issues related to multiple-load AGV systems and demonstrates the potential benefits of using them. Alternative vehicle dispatching strategies for multiple-load AGVs are discussed, stressing that different considerations are involved in dispatching empty and partially loaded vehicles. The effectiveness of single-load and two-load AGV systems is compared using simulation. The results show that, with multiple-load vehicles, the sensitivity of AGV system performance to guidepath layout is decreased, and the job input rate, which the AGV system can effectively handle without becoming a bottleneck for the overall system, is significantly increased. The relative effectiveness of selected control strategies is also investigated.