Scheduling of automated guided vehicles for tandem quay cranes in automated container terminals

This study investigates the automated guided vehicle scheduling problem for serving the tandem quay cranes in the automated container terminal. The tandem quay crane is equipped with two spreaders, allowing it to execute both single-lift and tandem-lift operations. When performing a tandem-lift, two automated guided vehicles are required to support the tandem quay crane's operation. Considering the coordination between tandem quay cranes and automated guided vehicles, a mixed-integer linear programming model is established to minimize the completion time of unloading operations by the tandem quay cranes. The formulation takes into account various crucial factors, such as traffic congestion and conflicts among automated guided vehicles, and the capacity limitation of yard buffers. A multi-start local search algorithm is developed for solving the problem. Computational experiments demonstrate the algorithm's efficiency and effectiveness in solving both small- and large-scale instances. Furthermore, the computational analysis highlights the importance of considering traffic congestion and conflicts, as well as limited yard buffers in the automated container terminal. The study also reveals that when a sufficient number of vehicles are available, the deployment of tandem quay cranes can lead to a substantial enhancement of approximately 30% in operational efficiency compared to conventional single-spreader quay cranes.