Predictor-Based Fixed-Time LOS Path Following Control of Underactuated USV With Unknown Disturbances

This paper investigates the path following problem of underactuated unmanned surface vehicle systems suffering unknown disturbances. A fixed-time predictor is proposed to approximate the sideslip caused by disturbances, by which the prediction error can converge to zero in a fixed time. By selecting appropriate controller parameters, the upper bound of settling time is identified. And it's independent of initial conditions, compared with the finite-time predictor. In addition, a fixed-time line-of-sight (LOS) guidance law and a fixed-time heading controller are proposed. The cascade system composed of the guidance law and heading controller is fixed-time stable. All states of the Unmanned surface vehicles (USV) system can be stabilized globally in a fixed time, and USVs can follow the desired path accurately. Finally, numerical experiments are given to illustrate the effectiveness and feasibility of the proposed algorithm.