Mathematical modelling and solving the Car Resequencing Problem considering remaining in PBS buffer as a new objective

One of the most important problems in managing the final assembly line of the car manufacturing factories is Car Sequencing Problem (CSP). By solving this problem, the optimal permutation of car models launched down in a mixed-model assembly line is determined. In a realistic circumstance, unforeseen occurrence of disturbances like shortage or delay in feeding required parts to the assembly line, caused to stir up an initially planned sequence. In this situation, another challenging problem should be solved that is car resequencing. This study treats the car resequencing problem where there is an intermediate buffer before final assembly line to rearrange a given initial sequence. Two objective functions are considered: (1) minimizing the ratio constraint violations (classic objective of car sequencing problem), and (2) minimizing work in process that remained in PBS buffer. For this problem, an integer linear programming mathematical model is developed. Since this problem has been proved to be strongly NP-hard, a new hybrid algorithm is proposed based on NSGAII+VNS in order to solve the problem in medium and large scales. The numerical experiments are used according to sample problems in CSPLib to run the mathematical model and evaluate the performance of the proposed algorithm in comparison to NSGAII. The computational results show that the hybrid proposed algorithm has a good effect on minimizing two objective functions in solving the medium and large-sized problems.