Lift Characteirstic Analysis And Research On Control Method Of Fin Stabilizer At Low Speed

No matter at any speed, while the ship is sailing on the sea, it inevitable must have swaymovement in which the rolling motion is most significant. In the moment, the fin stabilizer isthe most effective and the most widely used active anti-rolling device, it mainly resist thedisturbance forces by the lift on the fin stabilizer, and its anti-rolling effect is up to90%.However, the traditional fin stabilizer has a disadvantage that it can only reduce rolling whenthe ship speed is high. At low speed or at anchor, it can’t reduce rolling effectively. With thedevelopment of the ship and marine engineering, people make increasing demands on the rollstability of the ship, so it urgently need to create a fin stabilizer which can not only reducerolling when the ship speed is high, but also at low speed and even at anchor. This new kindof fin stabilizer has been developed in some other countries, and been widely used in the largemotor yachts. It proves that the low speed fin stabilizer can achieve a good anti-rolling effectat any ship speed in practice. As there is no such low speed fin stabilizer applications in ourcountry, the research of the low speed fin stabilizer has great practical significance.At first the thesis summarizes the development of the low speed fin stabilizer in othercountries, and analysis the generating lift principle and anti-rolling principle of the low speedfin tabilizer. Then it researches the fin pattern which is fit for the fin at low speed. Accordingto the knowledge of the fluid mechanics, it analysis the composition of the fluid force on thelow speed fin stabilizer and establishes the system mathematical model.In order to analyze the hydrodynamic characteristics of the low-speed fin stabilizer, thethesis establishes a physical model of the low speed fin stabilizer, and carries out the umericalsimulation in different motions with the FLUENT fluid dynamics simulation software. And itanalysis the influence of different motion control parameters(the swing period, the maximumangle, the velocity, the acceleration, the time of acceleration and uniform), ship rolling andship speed on the lift of the fin stabilizer at low speed.Finally, according to the characteristics of low speed fin stabilizer at low speed, thethesis determines a control method of the low speed fin stabilizer system: at high or middlespeed, using the traditional PID control method; low, at low speed or at anchor, using thefuzzy control method. In addition it establishes the “waves-ship-fin stabilizer” system model,and carries out the anti-rolling effect simulation of the low speed fin stabilizer in different seaconditions by the real ship parameters. From the simulation results, the low speed fin stabilizer system can achieve a good anti-rolling effect at any ship speed, and it prove the lowspeed fin stabilizer system in the thesis is feasible in theory.