Simulation Study On Joint Anti-Rolling Control Of Ship Fin And Rudder

Bad sea conditions will seriously affect the maneuverability of the ship,and the forces and moments acting on the ship will cause its sway motion in all degrees of freedom.,the influence of ship maneuverability is given priority to with rolling motion and bow wave motion,rough rolling games causes the damage of equipment and transport goods,and even cause rollover accidents;Rolling motion will lead to ship yaw,prone to accidents such as reef collision and casualties,which will cause huge loss of property and people.Therefore,reducing the horizontal wagging of the ship and ensuring the stability of its course could effectively improve the stability and safety of the ship in the process of sailing.Based on the improved LQR control algorithm,this paper designs a fin-and-rudder joint anti-roll control system,which aims to improve the ship’s anti-roll efficiency and heading stability by using the joint control of fin stabilizer and autopilot under the interference of sea waves.Ships are usually equipped with autopilots to control course and anti-roll fins to reduce roll.During steering,the deflection of rudder blade and fin stabilizer will produce rolling moment,and the deflection of fin stabilizer also produces roll moment and roll moment at the same time.If the anti-roll action of automatic rudder and fin stabilizer is coupled,the ship’s anti-roll ability can be enhanced.Therefore,reducing the ship’s transverse rocking motion and ensuring the stability of its heading can effectively improve the reliability and safe of the ship’s navigation.In this paper,the joint fin and rudder control system is studied to improve the ship’s transverse motion reduction efficiency and maintain the stability of the ship’s heading.This paper sorted out and analyzed relevant research methods of fin rudder joint roll reduction at home and abroad,proposed a new control method to realize fin rudder joint control on the basis of existing research,and the control system simulation block diagram is built based on MATLAB/Simulink software to verify its roll reduction and course keeping ability.The main findings and results of this paper are as follows:(1)Firstly,a four degree of freedom nonlinear mathematical of the ship is established based on the MMG separation model to analyze the ship motion,and the equations of motion are given for the relevant force and moment projections.To simplify the design of the controller,the nonlinear mathematical model of the vessel is linearized at the operating state of the equilibrium point.The mathematical model of actuator(rudder/fin)is built,in which the dynamics characteristics of rudder/fin are fully considered.(2)Secondly,the effect of wave disturbance on ship maneuverability is analyzed;the random waves are described mathematically through the superposition of regular waves.The random wave perturbation model is established by superposition of regular waves.The ITTC single parameter spectrum recommended by the 11 th International Towing Tank Conference in 1966 was converted into the spectrum of dip angle to describe the random wave interference.The wave disturbance mathematical model is built by wave forming filtering theory.Finally,the projection formula of the disturbance force and moment in the attached coordinate system is given.(3)Then,improving on the traditional LQR theory and using the improved LQR control algorithm to design a fin-and-rudder joint controller: A closed-loop state observer is used to estimate the state quantities of the control system.Based on the control law obtained by the traditional LQR control algorithm,the speed control law without static error is proposed through the linear transformation of the matrix,which can not only ensure the optimality of the control law,but also realize the static error of the controlled parameters,eliminate the steady-state error,and improve the control effect.A disturbance compensator is designed to reduce the deviation of roll angle and heading angle caused by wave disturbance.(4)Finally,a simulation platform of ship fin rudder joint control system based on MATLAB is established,and the feasibility of the proposed algorithm and the performance of the controller are confirmed by the simulation results.In different sea states,it is verified that the speed control law without static error can not only retain the optimality of the rate control law but also eliminate the steady-state error of the controlled parameters.The compensation jammer can effectively compensate the deviation of ship roll Angle and heading Angle caused by sea wave interference.Finally,it is verified that the fin-rudder joint controller designed based on the improved LQR control algorithm can achieve 80% transverse sway reduction efficiency and maintain the stability of the ship’s heading.