Objective   To solve lumped uncertainties of Unmanned Surface Vessels(USV)caused by system modeling errors and parameter perturbations, and path tracking problem of the model including non-zero non-diagonal terms and controller input saturation,

  Methods   a tracking control method of backstepping adaptive path of USV based on surge-varying Line-of-Sight (LOS)is proposed. First of all, a coordinate transformation is introduced to transform system model into skew-symmetric form. The controlled system is divided into two subsystems, guidance subsystem and control subsystem, respectively. In the guidance subsystem, the surge-varying LOS algorithm is developed to make guidance law of longitudinal speed positively correlated to transverse tracking error and ensure USV can effectively go towards and keep on the expected path; In the control subsystem, the lumped uncertainties of system are compensated by constructing backstepping adaptive algorithm. Simultaneously, the auxiliary system is introduced to deal with the problem caused by saturation of system control input.

  Results   The guidance-control closed-loop system is proved to be uniformly ultimately bounded by using Lyapunov stability theories.

  Conclusion   Simulation results verify the effectiveness and robustness of the proposed method. It has certain reference value for tracking control of backstepping adaptive path of unmanned surface vessels.