Design of Depth Controller for the Underactuated AUV

For the under actuated motion characteristics of autonomous underwater vehicle(AUV) with rudder and propeller joint control, a depth of back stepping controller has been designed by using back stepping method. First the linear modle of depth controller was get by analysing the vertical motion model of AUV. It used pitch as a virtual depth control. Then using differential homeomorphic transformation, the original control system became into a characteristic of nonlinear system with lower triangular structure. The depth controller was designed by using back stepping method. While, it was proved that the control system was globally stable under the action of the controller from Lyapunov stability theory. At last simulation experiments were made. Simulation results indicate that the controller has a strong robust, it is feasible and effective.