Integrating virtual resequencing with car resequencing via selectivity banks for mixed-model assembly lines

Abstract

Physical resequencing and virtual resequencing are two general forms of sequence adjustment in the context of mixed-model assembly lines. Selectivity banks can be used to physically change the production sequences on a mixed-model assembly line. Virtual resequencing can be incorporated into this process in order to improve the reordering outcomes. This paper introduces a problem of car resequencing before final assembly via selectivity banks that incorporates virtual resequencing. A mathematical programming formulation is presented to describe this integrated resequencing problem. The objective is to minimize the number of violations of sequencing rules within the downstream sequence. Several heuristic approaches for the car storage and retrieval processes are proposed, based on which nine integrated resequencing algorithms are developed. Computational experiments show that incorporating virtual resequencing nearly always obtains noticeably better results than pure physical resequencing. In addition, one of the presented algorithms, denoted by IR9, which jointly applies a chromosome based fill procedure and an integrated release procedure, performs best.