Horizontal Trajectory Tracking Control of AUV Using a Two-way Channel High Gain Observer

As the complexity and variety of actual sea conditions, autonomous underwater vehicles (AUVs) are subject to unknown disturbances in the horizontal plane which can cause the control system unstable. In this paper, the kinematics and the dynamics of an under-actuated AUV in horizontal plane are simplified considering environmental disturbances. And the trajectory tracking error of the system is defined. The external disturbances are estimated by using a high gain observer, which can not be directly measured. The observer is designed in two-way channels of longitudinal velocity and transverse velocity. In order to deal with nonholonomic constraints, coupling, nonlinearity and current disturbance in the tracking control, a trajectory tracking controller is designed using the backstepping method, which can make the closed-loop system globally eventual converge. In order to verify the robustness and validity of the proposed controller, a sinusoidal time-varying trajectory curve is designed from the perspective of practical engineering. The numerical simulation shows that the vehicle can track the desired trajectory and the tracking error tends to zero quickly.