Abstract
The automation of unified automated material handling system (UAMHS) in 300mm semiconductor wafer fabrication system (SWFS) is complex due to complicated product mixes, numerous and dynamic transportation demands, transportation deadlock, and vehicle blockages. Vehicle dispatching has become one of crucial means to improve the overall operating efficiency of UAMHS. Currently, many vehicle dispatching studies have been devoted to the optimization of the performance indexes of UAMHS. However, more important performance indexes related to SWFS, such as cycle time, throughput, and due date satisfaction, were seldom considered. To bridge this gap, a fuzzy logical and Hungarian algorithm-based (FLHA) vehicle dispatching approach is proposed to obtain better comprehensive performance of UAMHS and SWFS simultaneously. In the proposed approach, candidate wafer lots' transport priority is identified and sorted by fuzzy logic method firstly. Then the wafer lots with higher priority are selected as candidate lots, and it is assigned to the idle transport vehicles based on Hungarian method. After the optimized assigning solution is found, a greedy vehicle transport policy is design to execute it, which can reduce temporary transportation deadlock and vehicles' waste movement effectively. With experimental data from an UAMHS of 300 mm SWFS and running simulation experiments, the results demonstrated that the proposed approach is feasible and effective. Further comparisons with other traditional vehicle dispatching approaches show that the proposed approach has better comprehensive performance in terms of cycle time, throughput, due date satisfaction, delivery time, transport time, and OHT vehicle utilization.
Highlights
The semiconductor wafer fabrication system (SWFS) is one of the most complicated manufacturing systems in terms of technologies and manufacturing procedures [1]
This paper proposes a fuzzy logical and Hungarian algorithmbased (FLHA) vehicle dispatching approach for unified automated material handling system (UAMHS) in 300mm SWFS, in which the performance indexes of the UAMHS and SWFS are simultaneously taken into account
This paper proposed a FLHA dispatching policy to obtain better comprehensive performance of UAMHS and SWFS simultaneously
Summary
The semiconductor wafer fabrication system (SWFS) is one of the most complicated manufacturing systems in terms of technologies and manufacturing procedures [1]. In traditional vehicle dispatching approaches research, performance indexes to do with AMHS are usually focused on, such as delivery time, transport time, vehicle utilization, and so on. The proposed FLHA approach is an overall method, which is an organic combination and integration of three step methods, i.e. the wafer lots’ dynamic priority decision-making model, Hungarian algorithm-based vehicle assigning method, and greedy vehicle transport policy Through these methods, the comprehensive performances of the UAMHS and SWFS can be optimized. The purpose of the OHT vehicle dispatching is to assign a suitable wafer lot to each available OHT vehicle, and reduce temporary transportation deadlock and vehicle blockages during vehicle transportation, thereby improving the comprehensive performances of the UAMHS and SWFS. To describe the vehicle dispatching problem more clearly, a mathematical model is formulated
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