An optimal dual command policy for warehousing systems control: A case study

In this paper we propose an algorithm for op- timizing the sequencing of Dual Command (storage and re- trieval) operations into a modern warehousing system. We assume, as often it happens in real situations, that the se- quence of retrieval orders, which is just a list of instructions into a PC, can be modied so to maximize the throughput of the warehousing system. A rst eort is devoted to nd the theoretical throughput improvement, obtained by applying the proposed algorithm, assuming that the warehouse con- sists of a single one-sided aisle. On one side of the aisle there is a storage rack, which is assumed to have a contin- uous structure (that is it consists of an innite number of virtual location, each one addressed by a pair of real num- bers). The continuous approximation allows us to express the throughput improvement as a function of the rack shape factor only. In the second part of the paper, we derive the model of a real warehousing system, by means of a Colored Petri Net approach. Such a model is then used to show and validate the eectiveness of the proposed algorithm.