Scheduling Multiple Yard Cranes with Crane Interference and Safety Distance Requirement

Container terminals require robust scheduling algorithms for yard cranes to optimally determine the sequence of storage and retrieval operations in yard blocks for higher container terminal performance. This paper investigates the multiple yard crane scheduling problem within a generic yard block and considers the operational restrictions such as the crane noncrossing constraint and models the crane travel time realistically. Further, the fact that any two adjacent cranes must keep an operational safety distance is also taken into consideration. These physical constraints limit the mobility of yard cranes and greatly render the scheduling difficulty for such pieces of equipment.This paper proposes a clustering-reassigning approach, which fully considers all of the operational constraints in practice. The complexity of the approach is o ( n 3 ), where n is the number of container moves to be scheduled, making it suitable for real-time scheduling. Numerical experiments and benchmark with a continuous time-based mixed-integer linear programming model indicate that the clustering-reassigning approach can provide satisfactory near optimal solutions for different sets of test cases in a real-time scheduling context.