A Mobile rack Automated Storage and Retrieval Systems (MAS/ RS) are picker-to-stock retrieval model which are a variation of the multi aisles AS/RS. This mobile storage system is composed of racks moving laterally on rails so that one can open an aisle between any two adjacent racks, the input/output system, the storage and retrieval (S/R) machine and the computer management system or the control system. Evaluating an AS/RS could be done using several performance indicators, the two most important ones are: The utilization rate of the S/R machine and the average time necessary to serve storage or retrieval requests (the travel time). The S/R machine could operate either in single command or in dual command. In a single command, the S/R machine executes either a storage or retrieval operation by cycle. The time necessary to execute a single command is said single cycle time. While in a dual command, the S/R machine executes a storage operation followed by a retrieval operation in the same cycle. The time needed to execute a dual command is said dual cycle time. In this paper our interest is concerned with the mathematical modeling of single-command operations in a Mobile rack (AS/RS) system. We developed a closed form analytical expression allowing an approximate calculation of the travel time of Mobile Racks-AS/RS. This expression was compared with an exact discrete expression developed earlier by one of the authors. The models developed in this work are used by Kouloughli et al to determine optimal dimensions of the mobile rack AS/RS that minimize expected travel times.
Progress in Material Handling Research: 2014
Guezzen, Amine Hakim and Sari, Zaki, "An Analysis of Single-command Operations in a Mobile Rack (as/rs) Served by a Single Order Picker" (2014). 13th IMHRC Proceedings (Cincinnati, Ohio. USA – 2014). 9.