Analysis And Calculation Of Vehicle’s Random Vibration Response

The randomness of vehicle vibration is mainly caused by the following two factors. Oneis random excitation from the road. The other is randomness from parameters of such internalstructure as vehicle suspension stiffness and damping. At present, there are basically twomeans used to resolve the problem of the randomness of vehicle vibration. The first means isto take road excitation as sinusoidal excitation and turn the stochastic problem into thedeterministic one by using pseudo excitation method. The second one is to study the vibrationresponse of the fixed parameter under random road. However, few studies are conducted onthe randomness of such parameters as vehicle stiffness and damping etc. In this case, thepresent paper will focus on the following aspects:(1) The paper first briefly introduces some theories like random vibration and pseudoexcitation method. Next, the paper gives two different forms of the road input includingfrequency-domain input and time-domain input. As far as time-domain input is concerned, byusing filtered white noise method, the random road model of single wheel vehicle isestablished, and the matlab is used to simulate the time-domain excitation of road with A, B,C levels.(2) In vehicle linear suspension system, by adopting the pseudo excitation method, thesystem acceleration power spectral density function expressions of1/4vehicle’s single degreeof freedom and two-degree-of-freedom are calculated, and when body mass, suspensionstiffness and suspension damping etc. change within a certain interval, the power spectrumgraph of response acceleration is simulated. By using the James formula, the system responsespeed variance of the single degree of freedom is calculated, and when the body mass,suspension stiffness and damping etc. follow a normal distribution, the mean, standarddeviation and coefficient of variation of the response speed variance are calculatedrespectively. The calculation results show that as the random parameter is single, body masshas a maximum influence on the response amount and the influence acts less powerfully onsuspension damping and suspension stiffness the least, and that as the random parameter isthe two-parameter, the random factors not only increase, and the variability of the parametersbut also exerts a more apparent influence on the response amount.(3) In vehicle nonlinear system, when the vehicle suspension stiffness and damping etc.follow the normal distribution, the paper mainly discusses their influence on the system. Thepaper first transforms the nonlinear system vibration equation of1/4vehicle withtwo-degree-of-freedom into the equation of state. By using the fourth-order Runge-Kuttanumerical method, the paper then makes the numerical simulation of different dynamicbehaviors since the suspension stiffness and damping are different. The simulation results show that vehicles run in better stability within the range of the road excitation frequency.When the suspension stiffness following the normal distribution is the random parameter, thelarger the mean value of the stiffness becomes, the stronger the randomness of displacementresponse caused by the stiffness will be and meanwhile the worse the stability of the vehiclesystem will be. When the suspension damping is the random parameter, the smaller the meanvalue of the damping is, the worse the stability of the vehicle system will be.The simulation analysis and calculation of the vehicle system adopted by the presentpaper are conducive to determining the appropriate suspension parameter, to controlling thevibration of the vehicle as well as to providing theoretical guidance for the optimizationdesign of vehicle suspension system.