Scheduling Yard Cranes Considering Crane Interference

Automated stacking cranes form the heart of modern container terminals. Hence, their productivity has a major influence on the performance of the terminal. In the first part of this paper, the yard crane scheduling problem and its practical relevance from the point of view of the Container Terminal Altenwerder (CTA) in Hamburg, Germany, is described. In Altenwerder, 26 yard blocks orthogonal to the quay with transfer areas at both ends of each block are operated with double rail mounted gantries (DRMG). In the second part of the paper, an outline of a new scheduling algorithm for yard cranes on this particular layout is given. The procedure minimizes delays for the jobs and the cycle times of the cranes. In addition to in-motion times also other parts of the cycle time, as waiting and blocking times resulting from other cranes, are taken into account in the scheduling approach. A branch and bound algorithm is used to create sequences of jobs for each crane. Using a simulation model, both the influence of the length of these sequences and the impact of technical breakdowns on the results are analysed. Finally, the results are verified with operational data and the applicability for practice at the CTA is evaluated.