A performance estimation model for an Automated Storage/Retrieval System by M/G/1 queuing system

It is quite common to adopt a static approach or computer simulation method for the performance estimation of the Automated Storage/Retrieval System (AS/RS). In most research, the authors assume that the storage/retrieval machine performs only either single command or dual command at each operation and, in addition, the type of request is known in advance, which is not adequate in the real system. In this paper, we propose a stochastic approach for the performance estimation of a unit-load AS/RS by using an M/G/1 queuing model with a single server and two queues. In particular, the steady state probability distribution of the number of storage and retrieval commands waiting in the queues is obtained in the form of transform. According to the computational comparison with the simulation, the proposed approach gives satisfactory results with very high accuracy.