Study On Semi-Active Suspension Control Considering The Change Of Fluid Temperature Of Adjustable Damper

As a damping element in suspension,shock absorber plays a decisive role in improving the maneuverability and stability of the vehicle.Most of the current researches on suspension performance still focus on how to control the damping characteristics of the damping element when it works,and most of them are on mechanical structure.However,the damping force of the shock absorber is generated by the fluid flowing through the damping hole.When the shock absorber works,the fluid temperature changes in real time.The change of the temperature will cause the change of the fluid property,thus affecting the damping characteristics of the shock absorber,and finally the damping effect of the suspension system,leading to the deterioration of the vehicle ride comfort.Based on the "Research on adaptive switching of active suspension control under road intelligent perception"(51605213)funded by NSFC youth fund,this thesis mainly studies the relationship between the damping force characteristics of shock absorbers and the change of oil temperature,and designs the oil temperature compensation method to improve the ride comfort of vehicles.Firstly,the internal structure and working principle of the damper are analyzed,and the modeling hypothesis is put forward.The relationship between the opening and pressure of each valve system is analyzed by Matlab/Simulink software,and the force and deformation curve of each valve system is obtained.The fluid mechanics model of the damper is built by AMESim software.Secondly,the characteristics of the damper are tested under different oil temperature,different input current and different piston velocity.According to the test data,the characteristics of the damper under different working conditions are sorted out,and the hydrodynamic model of the damper is simulated and verified according to the test data.Thirdly,the thesis analyzes the thermodynamic characteristics of the shock absorber and puts forward the hypothesis of heat transfer process.According to the first law of thermodynamics,the thesis analyzes the heat dissipation process of the shock absorber from three aspects of heat conduction,heat convection and heat radiation,and deduces the theoretical formula,obtains the calculation formula of the oil temperature of the shock absorber,and designs the adjustable viscosity oil module instead of the solenoid valve to control the fluid force of the shock absorber The fluid module of the model is used to build the fluid dynamics model of the adjustable damper considering the temperature,and the random road is used as the excitation input to get the temperature change of the fluid in the damper under different working conditions.Finally,a quarter vehicle semi-active suspension model is established,LQG controller based on optimal control theory and temperature compensator based on adjustable damping damper characteristic test are constructed,and the vehicle semi-active suspension control considering temperature is completed.The research results show that the temperature compensated semi-active suspension and the temperature compensated semi-active suspension have better control effect than the passive suspension when the damper fluid temperature is low,but when the temperature is high,the temperature compensated semi-active suspension can not play its control effect well.As the temperature is higher,the control effect is worse,and the temperature compensated semi-active suspension still can It can be concluded that the semi-active suspension with temperature compensation is better than the semi-active suspension without temperature compensation in improving the ride comfort of the vehicle,which proves that the temperature compensator can improve the performance of the suspension.