An analysis of the end-of-aisle order picking system: Multi-aisle served by a single order picker

This study deals with an end-of-aisle order picking system in a miniload automated storage/retrieval system (AS/RS). The system has a horse-shoe style buffer at the front end of each aisle. A conveyor system delivers the containers through the buffer positions. Earlier studies for the system assumed that an order picker serves only a single aisle. In general, however, an order picker can serve two or more aisles for labor cost saving, and so this paper assumes that an order picker serves a number of aisles in a predetermined order. The system can be modeled as a queueing system with a limited queue length and this paper analyses the queueing model with supplementary variable technique to find the system's long-run behavior. Then, it proposes a simple optimization model to find an optimal buffer size. To illustrate the results, some examples are included.