A Four-Quadrant Thrust Controller for Marine Propellers with Loss Estimation and Anti-Spin

Abstract In this paper a nonlinear thrust controller for a fixed pitch marine propeller with torque loss estimation and an anti-spin strategy is presented. The controller, designed to work in the four-quadrant plane composed by the shaft speed and the vessel speed, is a combination of a thrust controller designed for calm sea conditions and an anti-spin strategy to reduce power peaks and wear-and-tear in extreme sea conditions. The anti-spin algorithm avoid large increase of the shaft speed once high torque losses due to ventilation are detected and set the shaft speed to normal when the loss situation is considered over. The ventilation incident is detected by monitoring the torque losses, estimated with a nonlinear observer. The performances of the proposed controller are validated by experiments carried out in a towing tank.