Filtered Extended State Observer Based Line-of-Sight Guidance for Path Following of Unmanned Surface Vehicles With Unknown Dynamics and Disturbances

This paper investigates the path following problem for an underactuated unmanned surface vehicle (USV) in the presence of ocean currents, model uncertainties and input saturation. Firstly, a novel filtered extended state observer (FESO) based line-of-sight (LOS) guidance law is proposed. The FESO is employed to estimate the time-varying sideslip angle caused by ocean, wind and wave disturbances, which is incorporated into the proposed LOS guidance scheme. Then the path following control system is developed to keep the USV moving on the desired path by combining adaptive fuzzy technique with sliding mode method, where adaptive fuzzy technique is applied to deal with model uncertainties. Besides, an auxiliary system is designed to solve the issue of actuator saturation. By using Lyapunov's stability theory, the closed loop system is shown to be semiglobally uniformly ultimately bounded (SGUUB). Lastly, the comparison simulation results demonstrate the correctness and effectiveness of the proposed scheme.