Yard Crane Scheduling in the Presence of Uncertain Handling Times

This paper researches the problem of the scheduling of yard cranes within a yard block inside a container port terminal. Existing models found within the literature generally consider improvements to the scheduling of yard crane operations using a static and deterministic approach where all the problem parameters are fixed or certain. In reality, however, due to the interaction between the yard cranes working in a given yard block, the vast number of decisions required to be made in a short timeframe, as well as the unexpected events and failures that occur in real-world scheduling environment, there is a degree of uncertainty in the operation of such yard cranes. Hence, in this paper, the handling time of yard cranes is assumed to be uncertain and that it follows a triangular distribution. The resulting challenge of scheduling under uncertainty is NP-hard and presents a complex optimization problem. This research develops a heuristic solution by considering the real yard crane operational constraints like fixed safety distance, inter-crane interference, and simultaneous storage and retrieval operations. The proposed heuristic approach is able to find near optimal solutions in reasonable time. The performance of the proposed approach is demonstrated through multiple experiments which are carried out on a large set of instances which reflect different operational scenarios.