A Constraint Programming Approach for the Multi-Robot Multibay Unit Load Pre-marshalling Problem

Autonomous mobile robots are increasingly employed to automate intralogistics operations. This work addresses the multi-robot multibay unit load pre-marshalling problem, wherein robots optimize warehouse processes during peak times by proactively reshufing inventory based on anticipated demand during idle periods. The problem involves reshufing a warehouse according to priority classes using multiple robots, necessitating coordinated tour planning between reshufing moves while respecting dependencies. A stage-based constraint programming model is introduced that determines reshufing moves and plans robot tours while considering dependencies between moves. Our objective is to minimize the makespan for the minimum number of moves. The results demonstrate the limitations of the constraint programming model and offer valuable insights for future heuristic approaches.