Research On Anti-rolling Control Strategy Of Fin Stabilizer At Full Speed Based On Multi-mode Technology

Fin stabilizer is the most commonly used anti-rolling device.The research of the theory of stabilization of fin stabilizer has been focused on the rolling motion of ship at medium or high speed.There is relatively little research on the use of fin stabilizer in low speed.bionic wings are applied in our anti-roll system.This type of foil not only meets the requirements of the traditional roll stabilizer,but also can ensure the anti-roll effect under low speed and even mooring.The theory of aeronautical wing can not analyze the hydrodynamic characteristics of fin stabilizer under full speed,since the working mode of fin stabilizer at low speed is different from that of traditional fin stabilizer,which means the flow field of fin stabilizer is relatively more complicated at low speed.The latest research on fin stabilization of fin stabilizers is focused on the use of fin stabilizers in mooring or at zero speed,And the designed nonlinear control system method with difficulty in solving,complicated control law structure,large computation amount and strong limitation is adopted,which does not consider the compatibility of the system under full speed.The lift of the fins at low and medium speeds is obtained by using hydrodynamic analytical relation at zero speed,that is to ignore the angle of attack and fin speed of this part of the hydrodynamic.This approximation neglects the fact that the small-aspect-ratio fins used in full-speed fin stabilizers and the high-speed dynamic motion in which conditions the stall angle will delayed.While confusing the hydrofoil's dynamic characteristics and hydrostatic characteristics of the hydrofoil.After the above discussion,The paper mainly studies the following issue:First,Mathematical modeling of ship roll stabilization system.the ship disturbance model is established,the ship roll rolling motion is analyzed by force,and the ship roll equation is established.Second,The lift formula of fin stabilizer at full speed was established based on the fluid mechanics and computational fluid dynamics(CFD)software FLUENT.The modeling of hydrodynamic in the process of tapping of the fin stabilizer,using the CFD software to simulate the 3D full scale fin stabilizer model and the complex undetermined coefficients in the theoretical analytical formula are fitted.The hydrodynamic characteristics of the fin stabilizer under low and medium speed are analyzed by a large number of computer simulation hydrodynamic experiments.It is proved that the lift speed model has the disadvantage of neglecting the fin attack angle,based on the experimental data,The formula of lift force of fin stabilizer of full speed is given with several sets of experimental data andtheoretical analysis.Last,Multi-controller switching research of fin stabilizer at full speed.the mathematical model of each basic structure of the fin stabilizer control system is established.the corresponding sub-controller is set separately for the lift sub-model.Based on the speed,the whole speed control law is set to achieve full speed rolling system of variable parameter control,By applying the slow switching theory and decomposing the controller into a fast decay mode section and a slow decay mode section to achieve bumpless switching between the controller.The control scheme of the original anti-rolling system is simply improved.Finally,Matlab Simulink is used to build the whole speed anti-rolling control system,the simulation result shows that the designed Multi-mode controls with the well effects.