An analysis of AS/RS performing both single and dual commands

Abstract

As for the performance estimation of the AS/RS(Automated Storage/Retrieval System) most research assumes the AS/RS machine performs only either single command (SC) or dual command (DC) at each operation, and in addition, the type of requests is known in advance, which are not adequate in the real system. In this paper, we propose a stochastic approach for the performance estimation of a unit-load AS/RS. We assume that the service time when the AS/RS performs single command is differently distributed from that of dual command. Especially, we obtain the steady state probability distribution of the numbers of storage and retrieval commands waiting in the queues at each service completion epoch.