Study On Joint Anti-rolling Control Of Fin/Tanks Under Parametric Roll

Large-scale vessels such as container ships are prone to a large-angle,non-linear roll phenomenon when navigating in vertical waves.This phenomenon is called parametric roll.Once the parameter roll occurs,it will cause serious economic losses and even the possibility of capsizing.Therefore,applying the anti-rolling device to the suppression of parametric roll has very important practical application significance.Aiming at the problem of large roll angle in the parametric roll phenomenon,a plan of combined fin stabilizer/active anti-roll tank is proposed.According to the different effects of fin stabilizers at different speeds,a speed-based fin/tank righting moment distribution system is proposed.Simulations prove that this method can reduce the roll angle when the parametric roll occurs at different speeds.Finally,considering the anti-rolling effect and system energy consumption,comprehensive goals and constraint equations are given.The optimal strategy for the distribution of the righting moment of the fin and the water tank is given by using genetic algorithm optimization.The active control of parametric roll through ship fin stabilizer/active anti-rolling tank is studied mainly,including the following aspects:First,referring to the three-degree-of-freedom(heave,pitch,and roll)nonlinear model,this model is simplified to obtain a single-degree-of-freedom nonlinear time-varying parameter roll mathematical model.The simulation comparison of these two models proves that the singledegree-of-freedom model can track the three-degree-of-freedom model well.Then,the working principle and mathematical model of the fin stabilizer and the antirolling tank are analyzed,and the mathematical model of the joint anti-rolling control system is established on this basis.The influence of the parameters of fin stabilizer on the anti-rolling efficiency and the influence of the parameters of anti-rolling tank on the natural frequency of the ship are analyzed,so as to select the appropriate parameters of fin stabilizer and anti-rolling tank.Secondly,the controller of the fin stabilizer and the anti-rolling tank is designed and simulated to analyze the respective effects of anti-rolling and the energy consumption.The righting moment required for ship rolling and the righting moment produced by the fin stabilizer and the anti-rolling tank are calculated,and the distribution algorithm of righting moment of the joint anti-rolling system based on the speed is designed.And the energy consumption required by the fin stabilizer and the stabilizer tank to generate the righting moment is calculated,and the simulation proves that the method can reduce the roll angle when the parametric roll occurs at different speeds.Finally,the moment distribution problem of the joint anti-rolling control system is reduced to a multi-objective optimization problem.The righting moment required for ship rolling and the energy required for the fin and anti-rolling tank to generate the corresponding righting moment are calculated.Based on the principle of optimal energy consumption,genetic algorithm is used to optimize the distribution of righting torque.Simulations prove that this method can reduce system energy consumption while hardly affecting the anti-rolling effect.