Modelling and performance analysis of shuttle-based compact storage systems under different storage policies

Abstract

<p style='text-indent:20px;'>Short response time for order processing is important for modern warehouses, which can be potentially achieved by adopting appropriate storage policy. This paper models and analyses shuttle-based compact storage systems under random and class-based storage policies using a probability and queueing based approach. The ABC curve and the basic Economic Order Quantity model are used to determine the assignment of storage locations under class-based storage policy. The performance measures are obtained by using an iterative approach based on parametric-decomposition. The analytical model is validated against simulations and the results show our model can accurately estimate the system performance. Numerical experiments based on a real case are carried out. The results show that the best performance is likely to be provided by a class-based storage policy with a steep ABC curve and a skewed demand rate distribution. Multiple system configurations in terms of number of tiers, depth/width ratio, size of storage positions and velocity of system resources are also analyzed. The results suggest benefits of class-based storage policy regardless of the number of tiers. Moreover, the class-based storage policy outperforms the random storage policy in the system with a small depth/with ratio. However, the random storage policy is recommended for the system with deep storage lanes.</p>