Study on the Multi-Equipment Integrated Scheduling Problem of a U-Shaped Automated Container Terminal Based on Graph Neural Network and Deep Reinforcement Learning

Intelligent Guided Vehicles (IGVs) in U-shaped automated container terminals (ACTs) have longer travel paths than those in conventional vertical layout ACTs, and their interactions with double trolley quay cranes (DTQCs) and double cantilever rail cranes (DCRCs) are more frequent and complex, so the scheduling strategy of a traditional ACT cannot easily be applied to a U-shaped ACT. With the aim of minimizing the maximum task completion times within a U-shaped ACT, this study investigates the integrated scheduling problem of DTQCs, IGVs and DCRCs under the hybrid "loading and unloading" mode, expresses the problem as a Markovian decision-making process, and establishes a disjunctive graph model. A deep reinforcement learning algorithm based on a graph neural network combined with a proximal policy optimization algorithm is proposed. To verify the superiority of the proposed models and algorithms, instances of different scales were stochastically generated to compare the proposed method with several heuristic algorithms. This study also analyses the idle time of the equipment under two loading and unloading modes, and the results show that the hybrid mode can enhance the operational effectiveness. of the U-shaped ACT.