A mathematical programming model in path planning of a human-cobot order picking system

This paper optimises a single picker-cobot order picking system for e-commerce warehousing, aiming to minimise cobot path length based on the picker's route. In this Single-Picker-Cobot Routing with Decoupling Problem (SPCRDP), a picker selects items and carries limited goods, with the cobot providing transport. Based on the tri-tier commodity flow network structure and arc matching mechanism, we establish a special optimistic bi-level optimisation model. We transform the bi-level optimisation model into a single-level mixed integer linear programming model through optimal value reformulation, and build an algorithm framework with a three-level structure for solving. We also adopt a two-stage planning to quickly obtain feasible solutions to improve computing efficiency. Numerical results demonstrate promising performance on small to medium-scale instances, achieving cobot path optimisation ratios of up to 60%. This SPCRDP approach improves picking efficiency, reduces energy consumption, and contributes to intelligent human-cobot warehousing systems.