Analyzing the impact of key parameters of vehicle management policies in a unified AMHS

This paper deals with the management of vehicles in the Automated Material Handling System of a semiconductor wafer fabrication facility. Vehicle management policies (allocation of vehicles to transport requests, positioning of idle vehicles,...) strongly impact critical performance indicators, among them the allocation time (delivery time) and the lot cycle time. In the literature, most studies on the impact of vehicle policies on delivery times focused on segregated layouts and generally do not consider minimum service transport policies. We investigate a minimum service policy which consists in keeping a minimum number of available vehicles in bays to quickly answer transport requests. After describing the transport policy, we investigate how to define its key parameters. Using a detailed discrete event simulation model of a real semiconductor manufacturing facility, various simulation studies are performed to analyze the impact of these parameters.