Trajectory Tracking Control of Underactuated USVs Based on a Fixed-Time Guidance Strategy

To address the underactuated characteristics of Unmanned Surface Vehicle (USV), particularly the lack of actuation along the sway axis, a fixed-time stable imaginary solution avoidance(FTIA) guidance method is developed based on the backstepping technique. This approach ensures that the main position tracking error at the kinematic level achieves practical fixed-time stability. To further enhance the robustness of the control system, a reduced-order disturbance extended state observer (RDESO) is designed at the dynamic level. By applying the estimated disturbances to the surge and yaw rate controllers, the velocity tracking error of the front-actuated USV is guaranteed to be uniformly ultimately bounded.