Integrator Reset Anti-spin for Marine Thrusters Operating in Four-quadrants and Extreme Sea Conditions

Transient regimes arise when the propeller of a ship is operating in extreme seas, where ventilation and in-and-out of water effects results in loss of propeller thrust. By introducing Lyapunov based controller state reset, the performance in transient regimes may be increased without influencing the performance in calm seas. Improvements have been presented previously for dynamically positioned (DP) vessels. Transit operations, however, introduces additional losses due to variations in the propeller advance velocity. The controller in this paper combines an existing shaft speed reference generator that uses an estimate of the propeller torque losses with a PI shaft speed control law with integrator reset. Moreover, an anti-spin strategy is included to be able to operate also in extreme seas. The method is experimentally validated in a towing tank. Copyright c ©2007 IFAC