The design of a parallel zone-picking system with cooperation area between neighbouring zones and its cooperation methods

Keeping the workload balanced between zones is critical to the performance of zone-picking systems. However, with zone-picking systems, even if they are designed with workload balance in mind, once they are running, it can be difficult to keep the workload balanced. Furthermore, their no-zone-crossing constraint refrains pickers of neighbouring zones from helping each other. As a result, nothing can be done when workload imbalance occurs. In this paper, we focus on solving the workload imbalance problem in parallel zone-picking systems. We propose a new parallel zone-picking system that allows pickers to help each other by setting up cooperation area between neighbouring zones and study its design and cooperation problems. We propose different methods for each problem and conduct simulation experiments to test them. The simulation results give us not only the performance of the proposed methods, but also several important findings. For example, setting up cooperation area between neighbouring zones benefits the system’s performance. However, this does not mean having lots of cooperation between zones is the best. In fact, our study shows the always-help method performs as poorly as the no-cooperation method. And cooperation-area designs that create more adjacency in the cooperation area of neighbouring zones will perform better.