Car Resequencing For Automobile Assembly Shops Based On Downstream Release Order

The diversity of product has dramatically increased nowadays.As a low cost and efficient flexible production system,mixed-model assembly line(MMAL)can produce different models of a common base product on the same assembly line.It has been widely used in the automotive industry.Typically,multiple departments have different sequencing objectives in production.Therefore,actively adjusting the upstream sequence allows for a new individual sequence that meets the objective of the downstream departments.This thesis focuses on the resequencing problem with selectivity banks before automobile assembly shops.In view of the limitations and shortcomings of the traditional resequencing idea,this thesis proposes a new resequencing idea based on the downstream release order of vehicles,that is,to determine the release order of the upstream vehicles leaving the selectivity banks,and then to determine the arrangement of the vehicles in the selectivity banks.The framework of this thesis is summarized as follow:(1)For the general resequencing problem with selectivity banks before the assembly shops,an integer-programming model is developed,and a new resequencing idea based on the downstream release order of vehicles is proposed.Based on this new idea,four basic resequencing methods are proposed,namely block resequencing,rolling resequencing,ant colony optimization algorithm based resequencing,and step resequencing method.These methods have strong versatility and can be applied flexibly with different sequencing objectives.(2)This part treats the resequencing problem for the objective of car sequencing with selectivity banks.The integer-programming model is developed.The objective is to minimize the number of rule violations,and feasible resequencing methods are designed according to the overall framework of the four basic methods mentioned above.The performance of the proposed methods is tested through computational study.The results show that all the four resequencing methods have a good effect in acceptable time,and the step resequencing method is the best.In addition,the performance of ant colony optimization algorithm based resequencing method is similar to that of the step resequencing method for small-scale problem cases.(3)This part researches the resequencing problem for the objective of level scheduling where a selectivity bank is used to reshuffle the upstream sequence to achieve a constant production rate for each product.The integer-programming model is established.Based on the framework of the four basic resequencing methods,four resequencing methods for the objective of level scheduling are designed.The performance of the four methods is tested through computational study.The results show that the performance of the four methods is gradually enhanced,and the step resequencing method is the best.Additionally,the resequencing effect of the four methods decreases slightly with the increase of the number of vehicle.