Abstract: As the bottleneck resource of the four-way shuttle systems, the performance of lifts scheduling scheme is closely related to the system operational efficiency. A lifts scheduling strategy is proposed for the lifts scheduling problem. First, the lifts scheduling problem is transformed into a flexible job-shop scheduling problem with transportation time, and a mathematical model is constructed considering the constraints of task sequencing on the same tier. Second, an improved hybrid genetic algorithm is proposed to solve the model, which is based on the hybrid genetic algorithm. Since the hybrid genetic algorithm is easy to produce illegal individuals, leading to the decline of the search ability of the algorithm, an individual correction method is proposed to enhance the search ability of the algorithm. Finally, the feasibility and effectiveness of model and improved hybrid genetic algorithm are verified using the actual data of an agricultural product cold store. The results show that the improved hybrid genetic algorithm can save the task completion time by at least 24.66% compared to the actual applied strategy.

Key words: four-way shuttle systems, lifts scheduling problem, improved hybrid genetic algorithm