Travel time analysis for shuttle-based storage and retrieval system with middle input/output location

Along with the rapid development of electronic commerce, the importance of logistics links and new designs of automated warehouse have been developed. A big boost has been given by shuttle-based storage and retrieval system (SBS/RS). Compared with traditional mini-load automated storage and retrieval system, SBS/RS could achieve higher warehouses volume and throughput capacity. Since in each tier there is a single shuttle in most SBS/RS, lift is always the bottleneck of this system. While all of the previous papers use lower left-point input/output location, in this paper, we present a single and dual command cycle time model of the elevator lifting table of the SBS/RS with middle I/O point location and consider the motion characteristics of the lift. The numerical analysis considers three different rack configurations and four velocity profiles. The results demonstrate good performance of our model, the dual command cycle time of lift reduce by 28.3% under the condition of middle I/O point, and the throughout increase by 17.3%.