Warehouse order picking activities are among the ones that impact the most the bottom lines of warehouses. They are known to account for more than half of the total warehousing costs. New practices and innovations generate new challenges for managers and open new research avenues. Many practical constraints arising in real-life have often been neglected in the scientific literature. In this paper we incorporate many product specific characteristics such as weight, fragility, and category of the items. Motivated by our observation of a real-case, we introduce the order picking problem under weight, fragility and category constraints. We make a full description of the warehouse which enables us to algebraically compute the distances between all pairs of products. We then propose two mathematical models to formulate the problem, and we present four heuristic methods, including extensions of the classical largest gap, mid point, and S-shape heuristics. The fourth one is an implementation of the powerful adaptive large neighborhood search algorithm specifically designed for the problem at hand. On a set of instances generated from our real-life observations, we assess the performance of all our methods and derive some important insights for managing order picking in this kind of warehouses.
Mots clés : order picking, warehousing, formulations, exact algorithms, heuristic methods