Flexible modeling and analysis of large-scale AS/RS-AGV systems

A method of modeling large-scale AS/RS-AGV systems is proposed in an attempt to describe the AS/RS precisely and flexibly in which a lot of items are stored and retrieved. The system considered in this study consists of the large-scale AS/RS with stacker cranes, the looped-track AGV system, aisle conveyors connecting these two systems, and incoming and outgoing conveyors. There are two major stages to model large-scale AS/RS-AGV systems flexibly and execute simulation experiments. The first stage is to generate a simulation program by inputting the selected parameters such as the number of banks, the number of bays, the number of levels of AS/RS, and the number of AGVs. The second stage is to perform simulation experiments. In the proposed model, every item number put on each rack, the corresponding number of cases for each item, the time of arriving at the warehouse, and the time of departing from the system are stored and recorded. Regarding a large-scale AS/RS system, three particular types of the rack arrangement, which have the same number of racks inside the warehouse, are analyzed to examine their performance. The analysis is performed using both average flowtime and equivalent annual cost as performance measures