Real-time pickup and delivery scheduling for inter-island logistics using waterborne AGVs

Archipelagic areas are in urgent need of efficient logistics systems to replace the limited bridges and fixed liners. This paper addresses the dynamic pickup and delivery challenge in inter-island logistics by utilizing waterborne autonomous guided vessels (AGVs). Specifically, the waterborne inter-island logistics problem is precisely expressed as a mixed integer programming (MIP) model. The model considers a variety of practical system constraints that could arise for the waterborne AGVs, e.g., capacity, time windows, berth allocation, and loading constraints. Moreover, in order to solve the possible large-scale scheduling problem dynamically and efficiently, we design an improved variable neighborhood search heuristic method. The approach is featured with four local search strategies and an effective perturbation heuristic to deal with the local minima issue. Extensive comparison experiments are carried out using real-world datasets. The results demonstrate that our algorithm outperforms baseline algorithms in 98% of cases, achieving improvements of over 10% compared to greedy rule-based methods and more than 5% over state-of-the-art heuristic algorithms, such as VNSME. These findings highlight the substantial benefits of the proposed technique, offering significant cost savings when effectively implemented. Comprehensive ablation experiments and parameter sensitivity analyses also demonstrate that the proposed algorithm has superior capabilities in space exploration and exploitation, provided that the step size operator is properly set. The proposed modeling and solution algorithms show great potential in enhancing the efficiency of the inter-island logistics systems.