Bi-criteria Scheduling in an Assembly Flowshop
This paper addresses an assembly flowshop scheduling problem with finite intermediate storage between stages. The production occurs in two 8-hour shifts per day. Hence, the production is discontinuous. The objective of the problem is to minimize the linear combination of total setup time and weighted tardiness. The paper evaluates the performance of non-permutation schedules vs. permutation schedules. Since the problem is NP-hard, two algorithms each, are developed for permutation and non-permutation schedules. The first algorithm uses tabu search based only on short-term memory as a local search algorithm whereas the second algorithm incorporates tabu search into the framework of path relinking technique. The efficiency and effectiveness of the algorithm is compared with the results obtained from CPLEX. The results show that the non-permutation schedules offer a slight advantage over permutation schedules. In addition, it is shown that the tabu search/path relinking algorithm is superior to the short-term tabu search algorithm. To mimic real industry situations, sequence-dependent setups, dynamic release times and dynamic machine availability times are considered.
Keywords - Assembly flowshop, shift production, finite storage capacity, tabu search, path relinking, sequence-dependent setup