Robust Optimization Study of Vessel Formation Departure Scheduling in Three Gorges Lock

The backlog of vessels in Three Gorges has become the norm. The scheduling of formation sailing according to the vessel crossing plan can improve the efficiency of a vessel crossing to a certain extent. Still, the sailing continuity and the smoothness of the approach channel in front of the dam are directly affected by unexpected events such as temporary vessel control, hydro-meteorological changes, and vessel failure. In this paper, we analyze the characteristics of unforeseen events affecting vessel formation navigation, and construct a robust optimization model for vessel formation navigation dispatching across Three Gorges with the vessel formation arrival time as the uncertain parameter for formation navigation, the minimum idle time at the designated position and the highest execution rate of the lock plan as the objectives, and verify the effectiveness of the robust model through actual vessel navigation data in Three Gorges. The research results show that, compared with the traditional vessel scheduling optimization, the robust optimization model of the Three Gorges Passage Vessel Formation Departure Scheduling proposed in the study avoids delays in lock operation and vessel vacancies caused by uncertainty in vessel sailing time and increases the utilization rate of channel resources by 5.42% and the execution rate of lock times by 12.5%.