An efficient simulation model for rack design in multi-elevator shuttle-based storage and retrieval system

A shuttle-based storage and retrieval system (SBS/RS) is a relatively new material-handling facility. A multi-elevator tier-captive SBS/RS is a newly designed subset of such a facility. This new system consists of tier-captive shuttle carriers, multiple elevators with a lifting table, and racks. The storage rack of the system is defined in terms of tiers, columns, and the number and position of the elevators. The aim of this study is to develop an efficient simulation model that can be auto-remodeled for different rack configurations. With this model, it will be easy for warehouse designers to test a large number of rack alternatives and to determine the optimal solution efficiently. Furthermore, the designers can illustrate the solution to shareholders through animation identical to the real system. A simulation case study is presented for a multi- elevator tier-captive SBS/RS containing 81 different rack alternatives. These alternatives are simulated under 15 different retrieval rates within 48 h, and finally, the optimal rack design is found out. We believe that our work will assist warehouse designers in efficiently designing racks of multi- elevator tier-captive SBS/RSs during early technology selection.