Design of multi-mode switch controller for fin stabilizer

Ships will inevitably roll with the disturbance of ocean environment when sail on the sea. Fin stabilizer is the most effective device to reduce ship roll motion. It rotates around its shaft to a certain angle of attack according to ships roll motion caused by the sea wave. However, the function of fin stabilizer is always in the passive status as the unpredictability of sea waves. This paper proposes a method to control fin stabilizer indirectly according to ship's roll to improve the timeliness of fin's works. The power spectrum density (PSD) of ship roll angle at different sea conditions are established. The peak frequency of the roll angle power spectrum density is chosen as the switching points. The controller parameters at different sea states are design in advance. The simulations is carried out to testify the effectiveness of the designed controller.