Solving the yard crane scheduling problem with dynamic assignment of input/output points

Abstract

This paper introduces an automatic yard crane scheduling problem with additional assignments of input/output (I/O) points at the block. I/O points are the buffer between the block and the rest of the terminal and containers are relocated from the block to the I/O points or vice-versa. The crane schedule therefore not only considers movements, storage and retrieval of containers, but must also be coordinated with the release and due times of containers at the I/O points, which are also limited and need to be assigned during the scheduling process. This results in a complex, but at the same time, more realistic problem. Two GRASP (Greedy Randomized Adaptive Search Procedure) heuristic approaches are proposed along with improvements to the solution construction and local search phases that are specifically tailored for this problem. The proposed algorithms are statistically calibrated and comprehensive experiments are designed to assess the performance of the method, including validation across small, medium, and large size instances. The experimental results show that the proposed methods are effective and competitive when compared to existing approaches. The GRASP manages to obtain an optimality average rate of 71.25% for small instances and finds 461 new best solutions in the 480 medium and large instances, with up to 200 containers, when compared to existing approaches for this problem.