Impact of zones on throughput and cycle times in warehouses with Autonomous Vehicles

Autonomous Vehicle based Storage and Retrieval System (AVS/RS) is a material handling technology, which has been proposed as an alternative to crane-based AS/RS. In AVS/RS, autonomous vehicles provide horizontal movement (x and y axis) within a tier whereas lifts provide vertical movement (z axis) between tiers. The transaction cycle time is composed of waiting time for vehicles and lifts, horizontal and vertical travel times, and load/unload times. In this research, we analyze the influence of multiple load/unload points on transaction cycle times and the design-tradeoffs involved in warehouse zoning. We model the system as a multi-class semiopen queuing network model with class switching and develop a decomposition based approach to evaluate system performance and obtain design insights. We validate the models using detailed simulation.