Precise modeling and analysis of large-scale AS/RS

A method of modeling large-scale AS/RS is proposed in an attempt to precisely describe the AS/RS in which a lot of items are stored and retrieved. The system considered in this study consists of a large-scale AS/RS with stacker cranes, a material handling system, and aisle conveyors connecting these two systems. In the proposed model, every item number put on each rack, the corresponding number of cases for each item, the time of arriving in the warehouse, and the time of departing from the system are stored and recorded. A framework of constructing simulation models is proposed, and an example is illustrated. It is shown that simulation proposed in this study can be used as a monitor of the real system for decision making. In addition, regarding a large-scale AS/RS system, four particular types of storing/retrieving systems are analyzed to examine their performance under various operation conditions.