Ship Formation Control Using Nonlinear Model Predictive Control With Safe Speed Constraints and Tidal Elevation Variations

ABSTRACT To improve transportation efficiency, an adaptive speed control method is proposed for ship formation control when a ship formation enters a port with tidal elevation variations. The nonlinear model predictive control (NMPC) method and leader‒follower structure are utilised for the formation keeping and trajectory tracking tasks. The proposed method establishes a ship manoeuvring model and a dynamic speed constraint model for adaptive speed control. A safe distance model is constructed to maintain a safe distance between ship formation members. The proposed safe distance model utilises a Serret‒Frenet (S‒F) coordinate system to describe the positions of ship formation members. Simulation experiments are applied to the North Channel of the Yangtze River. The experimental results indicate that the maximum actual draught accounts for 101.4% of the maximum safe draught without speed constraints. The draft ratio decreases to 99.2% after the adaptive speed control method is applied. This method can be utilised to effectively control ship formation navigation considering variations in tidal elevation.