Global Robust and Adaptive Output Feedback Dynamic Positioning of Surface Ships

A constructive method is presented to design a global robust and adaptive output feedback controller for dynamic positioning of surface ships under environmental disturbances induced by waves, wind and ocean currents. The ship’s parameters are not required to be known. An adaptive observer is first designed to estimate the ship’s velocities and parameters. The ship position measurements are also passed through the adaptive observer to reduce high frequency measurement noise from entering the control system. Using these estimate signals, the control is then designed based on Lyapunov’s direct method to force the ship’s position and orientation to globally asymptotically converge to desired values. Simulation results illustrate the effectiveness of the proposed control system. In conclusion, the paper presents a new method to design an effective control system for dynamic positioning of surface ships.