Path Optimization of Stacker in Automated Storage and Retrieval System with Split-Pallet Task

With the development of e-commerce, in some Automated Storage and Retrieval System (AS/RS) the basic unit of the loading and unloading operations is not a pallet, but a box. In the case of the coexistence of the whole-pallet and split-pallet tasks, it is important to optimize the operation path of the stacker. In this paper, a mathematical model for the optimization of the stacker's operating path in the mixed mode of the whole/split pallet is established. The stacker scheduling is transformed into a TSP problem, and the Lin-Kernighan-Helsgaun(LKH) algorithm is used to obtain the sequence. The tasks of the stacker are classified into three types: loading the whole-pallet, unloading the whole-pallet, and split the pallet. We optimize the operation path of the stacker according to type of the task. The algorithm is implemented by programming, and typical scenario is simulated. The results show that the algorithm is more efficient than ant colony algorithm (ACO) and simulated annealing algorithm (SA). The obtained operation path is reasonable and effective.