Modeling AS/RSs

At a simple level, an AS/RS move time may be modeled by taking a time from a probability distribution that approximates the time to store or retrieve a load. More precise modeling incorporates the actual crane (horizontal) and lift (vertical) speeds. Each movement usually has a different speed and distance to travel which means that movement along one axis is complete before movement along the other axis begins. From a modeling standpoint, it is usually only necessary to calculate and model the longest move time.

In modeling AS/RS, the storage capacity is usually not a consideration and the actual inventory of the system is not modeled. It would require lots of overhead to model the complete inventory in a rack with 60,000 pallet locations. Since it is primarily only the activity that is of interest in the simulation, actual inventory is ignored. In fact, it is usually not even necessary to model specific stock keeping units (SKUs) being stored or retrieved, but only distinguish between load type insofar as it affects routing and subsequent operations.