Mixed-Integer Linear Programming and Constraint Programming Models for the Dual-lane Zone Picking System Operation

The rapid growth of the e-commerce market has increased the need for efficient order processing in order picking systems. Sequential zone picking is an effective approach to enhancing order picking by dividing the storage area into zones and sequentially transferring in-process orders across these zones via a conveyor system. Building on this approach, the dual-lane zone picking (DZP) system enhances efficiency by incorporating a conveyor system with two parallel lanes. This study focuses on solving the joint lane assignment and scheduling problem in a DZP system, with the objective of minimizing the makespan required to complete picking a set of order batches. Two modeling approaches are employed for problem formulation, including mixed-integer linear programming and constraint programming. Numerical experiments are conducted to evaluate the performance of the two approaches on different problem sizes and highlight the improved performance of DZP in minimizing makespan compared to the single-lane zone picking system.