LAUSR

Automated material handling systems (AMHSs) used in semiconductor fabrication are sophisticated and integrated control systems that transfer materials from one machine to another within a manufacturing facility via hundreds of vehicles. Vehicular congestion in AMHSs causes significant production inefficiency. In this paper, we demonstrate the reasons for and classification of congestion, and suggest congestion metrics for material handling systems. We develop and implement a congestion monitoring system (CMS) based on the proposed metrics at an actual manufacturing site. We provide practical case studies on three applications to address the effectiveness of CMS: 1) congestion monitoring; 2) redistribution of routing; and 3) enhancing a routing algorithm. Simulation results demonstrated that the proposed routing algorithm decreased the average delivery time by 12.41% in heavy congestion. The shorter average delivery time reduces the loss in production by at least 1%.