High-gain observer-based output feedback controller design for dynamic positioning of ships

The motion of a ship at sea is nonlinear and complex due to fact that the ship is subjected to hydrodynamic forces and environmental disturbances. Thus, the problem of velocity measurement and position tracking for a dynamically positioned ship is still of a great interest. In view of that, this paper proposes a high-gain observer based output feedback controller for the control of dynamic positioning of surface ships in the presence of constant unknown environmental disturbances. We apply both vectorial backstepping control technique and Lyapunov stability theory to design the output feedback controller using the high-gain observer. Simulation is carried out to demonstrate the effectiveness and performance of the proposed design approach. In addition, results obtained relatively show that the proposed controller guarantees both global boundness and global uniformly asymptotic stability (GUAS).