A nonlinear bottom-following controller for underactuated autonomous underwater vehicles

The bottom-following problem for underactuated autonomous underwater vehicles(AUV) was addressed by a new type of nonlinear decoupling control law.The vertical bottom-following error and pitch angle error are stabilized by means of the stern plane,and the thruster is left to stabilize the longitudinal bottom-following error and forward speed.In order to better meet the need of engineering applications,working characteristics of the actuators were sufficiently considered to design the proposed controller.Different from the traditional method,the methodology used to solve the problem is generated by AUV model without a reference orientation,and it deals explicitly with vehicle dynamics and the geometric characteristics of the desired tracking bottom curve.The estimation of systemic uncertainties and disturbances and the pitch velocity PE(persistent excitation) conditions are not required.The stability analysis is given by Lyapunov theorem.Simulation results of a full nonlinear hydrodynamic AUV model are provided to validate the effectiveness and robustness of the proposed controller.