Institute of Transportation, MOTC

　　Most container terminals use transfer cranes to stack containers in higher tiers to enhance their capacities. Hence, more containers may be stacked in the yard and picking complexity of loading them onto vessels may increase. According to the properties of transfer cranes, the problem of arranging their working sequence while picking export containers from the yard can be divided into two sub-problems: finding the optimal routing path for the crane to move among different bays, and arranging picking sequences for the trolley and the spreader of the transfer crane when the crane stays at a specific bay. This article focuses on the latter, and uses constraint programming, which accepts both logical and mathematical constraints, to develop a model to solve the sequencing problem for trolley and spreader. This model is verified with some cases.