Study On Disturbance Estimation, Modeling And LQG Control Of Latitudinal Movement For Ship

The shorted prediction for and control the movement cross direction of shipping is essential to safe catapulting and efficient navigate and curb of vessel. Because of action of ocean wave, wind and the other interactions, shipping has complex movement in six degrees. So, it is very difficult for us to predict and control the movement attitude of shipping in a very short period and it needs further study whether in theory or real project. The problem solved in this paper is the tenth five-year plan national defense scientific research fund subsidization topic, having practical value.On the basis of analyzing and comparing the history and the present study condition in foreign and China for the motion prediction and control of shipping, it used course rudder as the anti-rolling device. At first, this paper established the latitudinal equations of the shipping based on strip theory, in the latitudinal equations, swaying, rolling and yawing are intercoupling. Because it could not measure wave disturbance of real system, but we could easy get ship motion attitude and use the dependence of measuring state variable to estimate wave disturbance by means of three methods: central difference, Kalman filtering and extended Kalman filtering. When wave disturbance were estimated by using central difference, because of ignorance influence of system observation noise, estimation precision was low. Its estimation algorithm was simple, needing non condition and estimation precision could meet engineering precision requirement, so this technique had some use value in the situation of needing no high control requirement. By using Kalman filtering, service condition and computing process were more complex. Because system observation noise removed by filter and estimation precision was higher than central difference, this technique had more applied cost in works. By using extended Kalman filtering, the service condition was the most complex and the system order was run up, but its estimation precision was the highest of the three, because it meets the condition of Kalman filtering estimation. It estimated power spectrum of wave disturbance first, got forming filter, then using extended system model by forming filter to carry through Kalman filtering.