The warehouse reshuffling problem with swap moves

Abstract

The warehouse reshuffling problem deals with rearranging pallets in a storage from their initial to desired locations as fast as possible. In most studies involving the rearrangement of pallets, only relocation moves have been considered where a pallet is always relocated to an empty storage location. In this paper, we consider a warehouse with a twin shuttle stacker crane, which is designed to perform swap moves where the pallet at a storage location is swapped with that currently loaded on the stacker crane. We analyze and evaluate the warehouse reshuffling problem with swap moves, both analytically and experimentally, and examine differences to the problem variant with relocation moves. We propose heuristic algorithms as well as a transformation to the traveling salesman problem, which is applied to calculate optimal solutions using exact algorithms. Finally, we present computational results for randomly generated data based on a real-world company setting.