Frame Trolley Dispatching Algorithm for the Frame Bridge Based Automated Container Terminal

Abstract

This paper studies the container handling process for a newly designed container terminal, known as the Frame Bridge based Automated Container Terminal (FB-ACT). The system was shown to be an effective solution to the next generation container terminal, but its efficiency depends on the dispatching of frame trolleys (FTs), which transport containers along the apron. We address the FT dispatching problem to ensure conflict-free movements, while considering the handshakes with other devices in the system. A mixed-integer programming (MIP) model is formulated to minimize the makespan considering FT conflicts and handshakes. An algorithm based on filtered beam search is developed to solve the problem. In this algorithm, two filtering approaches are used to guide the search for beam nodes at each level. The first approach uses a surrogate model to effectively screen out the less promising nodes. Then, the second approach uses a reduced MIP model to further identify the beam nodes for the next level. Numerical experiments show that our proposed algorithm yields near-optimal solutions in small-scale problems. In large-scale problems, our algorithm significantly outperforms two other algorithms based on first come, first served (FCFS) or FCFS with dedicated vehicle assignment. Some interesting insights about the FB-ACT system are also shown in the study.