Effects of relocation to automated storage & retrieval systems storage location policy with production quantity variation

Most research on AS/RS (Automated Storage & Retrieval Systems) operation policy concludes that class-based storage policy has better performance than random storage policy. This result would be obtained if the system performance is evaluated with a fixed production plan. However, the production quantity of each item can not be kept at the same level at all times. The effect of production quantity variation per product between 10 and 80% is studied with random storage policy, 2 class-based, and 3 class-based storage policies with/without relocations to find acceptable ranges of variations. A typical AS/RS model is developed using GPSS/PC to be used for the evaluations. An applicable operation policy could be selected based on the degrees of production plan variation or a necessary variation point for re-location could be determined with the current policy.