Robust dynamic ship positioning control system design and applications

This paper describes the robust control system design for a ship dynamic po sitioning system. The control design is based on an approximate linear mode l derived from the nonlinear hydrodynamic equations governing the horizonta l motions of the ship. The nonlinear models of the ship, seawaves, current, wind and thrusters are derived and simulated for control design verificati on. The H-infinity control design technique is employed to design the contr oller. The control problem is formulated in state-space form and the design specifications are translated into requirements on the weighting functions of the error signal and the thrusters input. A tuning procedure is propose d based on the wind and wave disturbances. The controller is initially test ed on the nonlinear ship model and simulation results are presented to demo nstrate the robustness of the H-infinity controller. Tank tests results are then presented to assess the controller performance. Copyright (C) 2001 Jo hn Wiley & Sons, Ltd.