Job assignment considering OHT vehicle failure and, central loop and, traffic volume

Abstract

This thesis identifies the health state and the effect of the traffic volume on the OHT system of Overhead Hoist Transport (OHT) system vehicles, which are key equipment for semiconductor logistics transport, and addresses the job assignment problem considering them. OHT vehicle failure is a problem that frequently occurs in the manufacturing process, and is one of the causes of deteriorating the overall semiconductor logistics transport performance. In particular, when a movement stop occurs due to a temporary problem such as a communication failure, unexpected logistics transport congestion occurs. Job assignment policy considering failure is necessary as it adversely affects the OHT system when a vehicle in health-control fails in a place with a large volume of traffic, such as a central loop route. In this research, we present a quantitative analysis of how health state of vehicle and failure occurrences in central loop routes and high traffic volume affect the overall logistics performance. In addition, job assignment policy considering the failure rate, central loop path, and traffic volume is presented, and the effect analysis results are shared by applying it to the simulation environment.