Research On Ship Anti-rolling Control Techniques With Model Free Learning Adaptive Control Method

Disturbed by the wave and wind, the sailing ships have six degrees of freedom motions. When the condition is bad, rolling has the largest effect of the six degrees of freedom motions. The severe rolling not only makes the crew can’t work, but also might lead to equipment instruments failure. The serious rolling may even create capsizing accidents, heavy losing of property, environmental pollution and effects on life safety.Currently, how to effectively avoid this phenomenon occurred is a hot topic in the field of ship motions control. In order to ensure the safety of navigation ships, firstly, the characteristics of the wave environment should be studied, so the disturbed effects on the ship will be studied and the disciplines of the ship motions in the wave will be achieved. Secondly, the dynamic characteristics of the ship rolling motion should be studied, and then the reason of hard controlling of the ship rolling can be found. Thirdly, what kind of anti-rolling equipment will be chosen should be analyzed and what kind of control strategy will be chosen should be verified. At last, the new and effective control strategy should be studied to get the better anti-rolling effects for the purpose of safe navigation.Therefore, the ship rolling motion was chosen as the research object, after the analysis of its dynamic characteristics, the paper is focusing on the rolling reduction strategy. The specific studies are as follows:(1) On the basis of the overview of ship rolling methods for analysis of nonlinear dynamic characteristics at domestic and foreign, the Hilbert-Huang Transform (HHT) method was introduced into the analysis of the ship nonlinear dynamic characteristics, the sliding widows technique and the three B spline theory were applied into the improved HHT method, which not only extends the application field of the HHT method, but also provides a new idea for the characteristics analysis of the ship rolling motion. At the same time, the frequency components of the rolling motion were discussed and the reason that the rolling motion is difficult to control was analyzed, which provide the foundation of the application of the model-free control methods on the ship rolling motion control.(2) The standard MFLAC method and the PID method were introduced in the paper, according to the shortcomings of the application of standard MFLAC method on the ship anti-rolling system, the improved MFLAC method was studied, including the MI theory> the TD technology and the CGA algorithms. The improved MFLAC based on MI theory has the better convergence speed. The improved MFLAC based on TD technology has the stronger ability of anti-interference. The improved MFLAC based on CGA has the better adaptive ability.(3) On the basis of the overview of the ship rolling control methods at home and abroad, the improved MFLAC method was introduced into the area of the ship anti-rolling control. The single fin stabilizer system and the integrated fin and anti-rolling tank system were chosen as the controlled system. Compared with the traditional PID control method, the standard MFLAC method, the effectiveness and the practical application of the improved method were verified.(4) The simulation platform of ship motions was designed. The platform has the simple interface, the rapid calculation ability and the feature of3D display. It not only can provide the disciplines of the ship motions in the irregular wave, which bring the theoretical guidance for the safe navigation, but also can be intuitive to observe the real-time motions, at the same time, the control effect can be shown in this platform, which provides the visual, vivid form of expression about the control methods.