Crane scheduling for opportunistic remarshaling of containers in an automated stacking yard

摘要

Loading of containers onto a vessel can be delayed if the containers are inappropriately stacked at the yard. Remarshaling is the preparatory task of rearranging the containers ahead of loading time to minimize the delay at the time of loading. Previous works on remarshaling derive a remarshaling plan assuming that a certain amount of continuous period of time is available for the remarshaling jobs to be done in a batch; remarshaling jobs cannot be mixed together with the current main jobs in the crane schedule. In contrast, the method proposed in this paper allows remarshaling jobs to be scheduled together with the current jobs under the framework of iterative rescheduling, in which scheduling and execution of the jobs within a predetermined fixed-length look-ahead horizon are repeated in a regular interval. The remarshaling jobs selected for the mix are those that contribute the most to the reduction of future loading delay. The number of remarshaling jobs and their temporal positions within the mixed schedule for a look-ahead horizon are determined appropriately to best utilize the idle time of the automated cranes, which is enforced by an objective function to minimize the delay of the current main jobs as well as the makespan of all the jobs in the horizon.