Robust adaptive nonlinear controller design for dynamic positioning system of ships

For the dynamic positioning problem of surface ships with dynamics uncertainties and unknown disturbances, a robust adaptive nonlinear controller is developed based on radial basis function networks and vectorial backstepping. The radial basis function networks are employed to compensate for uncertainties of ship dynamics and disturbances. The advantage of the proposed control scheme is that any priori knowledge about dynamics parameters and disturbances of ships are not required. The derived control law can regulate the position and heading of ships to the desired target position and guarantee uniform ultimate boundedness of all the signals of the resulting closed-loop dynamic positioning system of ships. Furthermore, the positioning error can be made arbitrarily small by choosing the design parameters appropriately. Finally, simulation results on a supply ship demonstrate the effectiveness of the proposed control scheme.