Learning-Based Approach to Integrated Operational Optimization Problems in Robot-Assisted Multistation Warehouse Systems

In the era of booming e-commerce and Internet of Things technology, robotic mobile fulfillment systems (RMFSs) have gained more and more use in logistics industry. While these systems enhance labor efficiency, they introduce numerous optimization challenges. Order picking is a human–robot collaborative process in RMFS. It involves three critical and interrelated operational optimization issues: 1) pod selection; 2) resource scheduling; and 3) manual picking. Each of them is an NP-hard combinatorial optimization problem. Their integration is a significant challenge for operational optimization in RMFS with multiple picking stations and represents a novel problem that was not studied before to our best knowledge. To tackle this complex problem and fill the research gap, we first model it as a mixed integer program to derive exact solutions for small-scale and illustrative cases. For industrial-scale cases that cannot be solved by exact methods given limited time, we propose a tailored learning-strategies-enhanced local search algorithm. It integrates a 3-D bi-section encoding strategy, a three-stage decoding policy, a learning-based adaptive neighborhood selection method, and two learning-based tabu mechanisms. Experimental results demonstrate the effectiveness of our proposed method, achieving 2.9% to 33.2% performance improvement over six competitive peers. This highlights its superiority in solving the concerned problem, providing significant potential for addressing practical order picking optimization challenges in RMFS.