A travel time model for order picking systems in automated warehouses.

This paper addresses an order picking problem in a multi-aisle automated warehouse, in which a single storage/retrieval (S/R) machine performs storage and retrieval operations. When retrieval requests consist of multiple items and the items are in multiple stock locations, the S/R machine must travel to several storage locations to complete a customer order. The objective is to minimize the total time traveled by the S/R machine to complete the retrieval process of customer orders at the shortest time. First, we formulate the problem as a nonlinear programming model. Then, we propose a heuristic to solve the problem. Finally, we provide numerical experiments to evaluate the performance of the proposed heuristic. The results show that as the number of items in customer order increases, the heuristic shows a better performance by obtaining solutions close to optimal but in very small amount of times. [ABSTRACT FROM AUTHOR]