Performance evaluation of a robotic mobile fulfillment system with multiple picking stations under zoning policy

This paper evaluates the performance of a robotic mobile fulfillment system (RMFS) with multiple picking stations under a zoning policy. Focusing on a single picking process performed by robot, we develop an expected travel time model for the robot considering a constant velocity, and evaluate the system performance according to the travel time. Compared with the data of the actual RMF system from FAW Logistics Co., Ltd, the model developed in this study has high accuracy and can be used to rapidly evaluate the performance of RMFS with different layouts. In addition, by the numerical experiments, the effect of the number of horizontal aisles and two zoning policies on system performance is analyzed. The results show the following: (1) With the initial total number of storage locations determined, when picking efficiency and space utilization are taken as indexes for planning and designing, the optimal scheme can be obtained more directly by focusing on the effect of the number of horizontal aisles on the expected travel time. (2) Under the relevant assumptions and system characteristics proposed herein, when the expected travel time is taken as the index, it is always better to store A-class goods in the center of the pod storage area.