ANALYSIS OF DUAL-SHUTTLE AUTOMATED STORAGE-RETRIEVAL SYSTEMS

This paper addresses the throughout improvement possible using a dual- shuttle automated storage/retrieval system. Travel-between time in a d ual-command cycle is virtually eliminated, resulting in large throughp ut improvement. The system is extended to perform an equivalent of two dual commands in one cycle in a quadruple-command mode (QC). A heuris tic that sequences retrievals to minimize travel time in the QC mode i s developed. Monte Carlo simulation results show that the heuristic pe rforms well, achieving large throughput improvement compared with that of the dual-command cycle operating under the nearest-neighbor retrie val-sequencing heuristic.