Optimization on Retrieving Containers based on Multi-phase Hybrid Dynamic Programming

Retrieving export containers from a container yard is an important part of the ship-loading process. This paper presents a three-phase hybrid algorithm to solve for an optimized working plan for a gantry crane to retrieve all the containers from a given yard according to a given order. The optimization goal is to minimize the number of container movements, as well as the crane's working time. After generating an initial feasible retrieving sequence with heuristic rules, phase two obtains several alternative retrieving sequences through various methods. With a network, phase three constructs a shortest path problem and derives the optimal sequence by dynamic programming. Numerical testing results show that the algorithm is able to solve instances with more than 2000 containers, which is within the range of real-world applications. Moreover, the number of movements approaches the lower bound in most cases, and the resulting retrieving sequence is efficient.