An integrated optimization of location assignment and storage/retrieval scheduling in multi-shuttle automated storage/retrieval systems

This paper deals with the location assignment and storage/retrieval scheduling problem simultaneously in multi-shuttle automated storage/retrieval systems. Both the situations of performing a single operation cycle and multiple operation cycles are considered. Two related models, including an integer programming model and a dynamic programming model, are developed to formulate the problem. A two-phase tabu search algorithm is proposed to solve the integer programming model for the situation of performing a single operation cycle. Based on the search results, a construction heuristic is developed to improve the solution for the situation of performing multiple operation cycles. The computational results show that the two-phase tabu search algorithm can find better solutions than GA + MNN methods especially for the large-sized problems. In addition, it reveals that the construction heuristic can also significantly improve the quality of the solution for the situation of performing multiple operation cycles.