Optimization for integrated scheduling of intelligent handling equipment with bidirectional flows and limited buffers at automated container terminals

Although a large amount of intelligent handling equipment has been widely used in automated container terminals, few studies have explored the coordination optimization among them, which is critical to the overall operational efficiency of terminals. This paper investigates the integrated scheduling of intelligent handling equipment at automated container terminals, with challenging characteristics such as bidirectional flows and limited buffers. Besides, other characteristics such as blocking, machine eligibility, and separable sequence-dependent setup times also complicate the problem, making it difficult to find an optimal or near-optimal solution. This study formulates the problem as the blocking hybrid flow shop scheduling problem with bidirectional flows and limited buffers, and then develops a compact mixed-integer linear programming model that can obtain the optimal scheme on small-scale cases. To increase the size of solvable problems and improve the performance of the solution, an adaptive large neighborhood search is presented, which takes a high-quality coding scheme that specifies the equipment used by each job in various stages. Experiments have been conducted and computational results demonstrate the superiority of the proposed algorithm in terms of solution quality and convergence speed.