AGV Despatching in a Flexible Manufacturing System

An important issue in the design of a flexible manufacturing system (FMS) is the operational control of the materials handling subsystem, through which reparts are conveyed from one work station to the next. A popular type of materials handling device is the automatic guided vehicle (AGV), which has been widely adopted in FMS because of its versatility and speed. This paper presents a simulation study to investigate the effects of different AGV dispatching rules on the performance of an FMS under various operating conditions. The dispatching rules studied are: FAFS — select the first available AGV; MIT — select the AGV with the most idle time; STT — select the AGV with the shortest travel time; and LTT — select the AGV with the longest travel time. The performance measures adopted are: overall production rate of the system; mean work station utilisation; and mean AGV utilisation. Although the results obtained are related to the specific FMS layout studied in this paper, it is believed that the inferences drawn from them are applicable to any FMS with similar layout structure and can provide useful guidelines for AGV design.