Study On The Nonlinear Dynamic Model Of High-speed Train Yaw Damper

As one of the key suspension components of high-speed trains,yaw damper plays a vital role in ensuring the stability of the vehicle’s hunting motion.At present,the yaw dampers of two typical structures have different dynamic characteristics due to the different internal oil flow directions,especially the asymmetry of the recovery and compression strokes,which is difficult to be simulated quickly and accurately in the vehicle system dynamics simulation.In this thesis,the structural characteristics,modeling process and damping characteristics of two typical yaw dampers with different oil flow directions are studied to establish the nonlinear dynamic model of the yaw dampers,which can be applied to the rapid and accurate simulation of vehicle system dynamics.Then,the dynamic and static characteristics and the relationships between them of the yaw dampers are studied.The work of this thesis is of great significance for the refined dynamics simulation of high-speed trains and the optimization of the parameters of the yaw damper.The specific researches are as follows:(1)The single damping model,the spring damping series model and the damping nonlinear Maxwell model of yaw damper are established to study the static and dynamic damping characteristics.Calculation methods of the dynamic stiffness and dynamic damping of the spring damping series and parallel models are equivalently analyzed.Considering the nonlinear characteristics of series damping of the Maxwell model,the dynamic characteristics of yaw damper with nonlinear damping are studied.(2)The structural characteristics and working principles of the unidirectional and bidirectional-oil-flow yaw dampers are analyzed in detail.The mathematical models of each sub-module of the yaw dampers are summarized,including: plunger and valve plate damping valve models,one-way flow valve model,oil flow loss model and chamber pressure-flow equations,etc.By converting the static damping characteristic curves to pressure-flow curves and optimizing the flow distribution coefficient,the damping valve models of the two yaw dampers with different oil flow directions are simplified separately.Considering the stiffness of the rubber nodes and the mass of the piston of the yaw dampers,the simplified nonlinear dynamic models of the two yaw dampers are established respectively,which are based on physical parameters.(3)The static and dynamic characteristics of the two types of yaw dampers are tested on the bench,and simulated by the damping nonlinear Maxwell model and the nonlinear dynamic model.The comparison between simulations and tests shows that the nonlinear dynamic model has high accuracy and speed in simulation,can accurately reproduce the static and dynamic characteristics of the two types of yaw dampers;the Maxwell model can basically reflect the static characteristics of the yaw damper,but cannot accurately reproduce frequencydependent and amplitude-dependent characteristics under dynamic conditions and damping force asymmetry of unidirectional-oil-flow yaw damper.Nonlinear dynamic models are ideal for vehicle system dynamics simulation.(4)By changing the nonlinearity,the position of the unloading point,the unloading damping force and the unloading speed of the static damping curve of the unidirectional-oilflow yaw damper,the law of influence on the dynamic parameters is analyzed,and the relationships between the static damping curve and dynamic characteristics are established.The static damping curve has obvious nonlinear characteristic before unloading,which has a significant impact on the performance of the yaw damper under the small displacement conditions.Increase the unloading force,the dynamic damping increases significantly,and the dynamic stiffness increased when the excitation frequency is greater than 4 Hz.Simply increase the unloading speed,both dynamic damping and dynamic stiffness are reduced.(5)The influence of the flow distribution coefficient of the piston compression damping valve and the number of data points in the low speed region of the static damping curve on the dynamic characteristics of the bidirectional-oil-flow yaw damper is studied.The results show that the dynamic characteristics of the yaw damper are sensitive to the damping characteristics of the static damping valve in the low-speed region,and increasing the number of data points in the low-speed region can make the simulated dynamic damping characteristics closer to the test results.It is suggested to increase the low frequency working conditions in the static test of the bidirectional-oil-flow yaw damper,so that the dynamic characteristics of the yaw damper can be accurately simulated in the vehicle dynamics simulation with the model established in this thesis.