Abstract: In order to ensure accurate course tracking of underactuated unmanned surface vessels (USV) under wind, wave and flow interference, a course tracking control algorithm based on disturbance estimation is proposed. Compared with the traditional output feedback interference estimation algorithm, the extended disturbance observer is more flexible and controllable, which is designed by the longitudinal error as the state variable. At the same time, the variable gain is designed based on the state estimation error of the longitudinal tracking error. Compared with the constant gain observer, it can effectively reduce the oscillation of course tracking when realizing the disturbance compensation. Based on the theory of Lyapunov and the cascade system, the semi global exponential stability of the control system and the interference observation system is proved. The effectiveness and advancement of the algorithm are proved by simulation and comparison experiments.

Key words: underactuated, unmanned surface vessels (USV), variable gain, extended observer, variable line of sight (LOS), integral LOS (ILOS), course tracking