Integration of products expiry dates in optimal scheduling of storage/retrieval operations for a flow-rack AS/RS

Abstract

The contribution of this paper is to extend the problem of retrieval sequencing by integrating the product expiry date. Many researchers have studied the problem of sequencing storage and retrieval requests but by taking into account only the type of product without its expiry date. We apply this approach to the flow-rack AS/RS, by introducing an optimisation method as decision process which performs a real-time optimisation into two phases and formulated as integer program. The first objective is to select all interesting products for picking by determining a higher limit of the expiry date for each requested product. The second objective uses the results of the first optimisation problem in order to find bin locations for the retrieval requests realising minimal retrieval cycles for a batch of customer request. A numerical example is discussed to show the effectiveness of the method.