Direct/Indirect Adaptive Robust Control for Dynamic Positioning of Unmanned Underwater Vehicle

In this paper, a direct/indirect adaptive robust controller is presented to address the problems of parametric uncertainties, uncertain nonlinearities and unpredictable disturbances in horizontal dynamic positioning of unmanned underwater vehicle. Firstly, the model of kinematics and dynamics with 6 degrees of freedom is simplified and decoupled, and the independent model with 3 degrees of freedom in horizontal dimension is obtained. Then, the framework of direct/indirect adaptive robust controller is proposed. In the controller, adaptive model compensation, linear stabilizing feedback, nonlinear robust feedback and fast dynamic compensation are combined. A projection type adaptation law is applied to the estimation of model parameters, disturbances and model compensation errors. The proposed controller can guarantee vehicle's fast and stable trajectory tracking and point hovering as well as accurate on-line estimates of model's parameters and disturbances. The boundedness and stability of the proposed controller are proved. The simulation is carried out in MATLAB/Simulink environment, and the results verify the effectiveness of the proposed controller.