A throughput model for carousel/VLM pods

In this paper we present the msults of a research project to develop analytical models to determine the throughput of pods of carousels or Vertical Lift Modules (VLMs) with human order-pickers picking batches of orders. The primary advantage of using carousels/VLMs over static shelving is that much of the walking time associated with static shelving is removed since the carousels/VLMs bring the items to the order pickers. Multiple carousels/VLMs are typically grouped together in what are called pods to ensure that the order-picker does not have to wait on the carousel/VLM while it is rotating to retrieve the next item. The carousel and VLM throughput models are presented along with testing that indicates that they perform well under various system configurations. We include an example of how the throughput models can be used as an aid in the storage design process.