Travel time analysis for the double-deep dual-shuttle AS/RS

Comparing with traditional single-deep single-shuttle automated storage/retrieval systems, double-deep dual-shuttle AS/RS have the advantages of high space utilisation and more efficient, since less number of aisles and less empty travel of S/R machine. This warehousing systems have been developed for use in factories and distribution centres. In this paper, we first develop analytical models of quadruple command cycle to estimate the performance of such system, then taking the single shuttle and dual command cycle as the benchmark model, the potential improvement by dual shuttle has been analyzed, the results show that the efficiency of the system has a significant improvement using dual shuttle S/R machine. In addition, we have extended the proposed travel time to a special case that the double empty storage locations will take place and some management insights are given.