Robust time-varying formation tracking control of underactuated unmanned vessels

Time-varying formation tracking of multiple surface vessels system is considered. Firstly, the interaction topology and the time-varying formations of multiple surface vessels are established based on algebraic graph theory. Secondly, the cubic spline interpolation method is used to obtain the desired trajectory when only several path points are given. Thirdly, for leader ship, trajectory tracking control law of outer loop and robust attitude tracking law of inner loop are designed based on the idea of virtual leader. Fourthly, for multiple follower vessels, a distributed time-varying formation tracking control law using only neighboring relative information is designed in the outer loop, and a robust attitude tracking law is designed in the inner loop. In attitude tracking, sliding mode control method is utilized to control the course angle and navigation speed, which eliminates the influence of model parameter perturbation and external disturbances such as wind, wave and current in vessel motion. Finally, numerical simulation results are given to confirm the effectiveness of the acquired theories.