Study On Rudder Stabilization System For Ships

The ship stabilization is one of an important topic about ship and ocean structure. The motion of ship is a very complex movement. Because of action of ocean wave, wind and the other interactions, shipping has movement in six degrees .In the bad sea condition, it would bring about prodigious safe hidden trouble for ship's operation. It is introduced the principle of anti-rolling and anti-pitching by rudder. Based on strip theory, this paper establishes the latitudinal equations of the shipping coupled swaying, rolling and yawing. The ship longitudinal motion coupled equations about heaving and pitching two degree of freedom is also built. Forming filter of sea disturbance is given, which modeled for the disturbing force and moment of random sea. Forming filter of sea disturbance being part of ship motion system, the ship augmenting motion equations are established. By studying rudder stabilization, many investigator find that the nondeterminacy of ship model affect the effect of rudder stabilization.Firstly, use PID control, in the MATLAB environment, simulation curves are obtained by simulink toolbox. From the result it is shown that under some circumstance the roll reduction rate can reach 53%, at the same time control the heading of the ship. Because it could not measure wave disturbance of real system, but we could get ship motion attitude, and estimate wave disturbance by means of two methods: Kalman filtering and extended Kalman filtering. Usingπtype rudder as the device of anti-rolling and anti-pitching and control it by optimal control method. It divide into suboptimal control and optimal control base on difference feedback state estimation result brought by system input difference disturbance. It shows optimal control effect is better than suboptimal control effect. When system is extended, the extended status contained not only inherent system status but also information of stochastic wave disturbance. The extended stochastic optimal control variable contain negative feedback for the system status and the compensation for systems stochastic wave disturbance. By theoretical analysis and simulation conclusion, for rudder stabilization, the result shows that the extended stochastic optimal control is better than classical stochastic optimal control. The result shows that rudder stabilization has much use value.