Simulation For Automobile Ride Comfort Based On Pseudo Excitation Method

With the rapid development of national economy, the overall construction of expressway network and the great improvement of people's living standard, automobiles have gradually come into people's life and work, and become an indispensable means of transportation. Automobile ride comfort is one of the most important capability guideline. The quality of automobile ride comfort influences not only people's comfortableness, efficiency of work and healthiness, but also influences the automobile's power and economic performance and handling and stability. Therefore the investigation to improve automobile ride comfort is attached more and more attention.The pseudo excitation method(PEM) is a precision and highly efficient algorithm for random vibration proposed by Pro J.H.Lin. Especially when calculating the high degree of freedom(DOF)model's random dynamical response, it can greatly predigest the calculating step and still keep theoretically accuracy. The pseudo excitation method has been applied and further developed in many engineering fields, and solved many problems. But few people apply this method in automobile field. This article is for the purpose of applying PEM in automobile ride comfort. Main content of this article is as follows:(1) Aiming at the description of theory of PEM wasn't systemic anciently, from the single DOF linearity system, its basic theory of the single DOF linearity system has been elucidated. Research of PEM of the single DOF linearity system, constructing method of pseudo excitation has been elucidated by the simple and easy understanding way, at the same time, the basic formula and derivative relations of PEM have been showed. Researching of the multi-DOF linearity system, the basic theory of the real mode and the complex mode has been described. Using the theory can translate the multi-DOF linearity system into the single DOF linearity system. Thereby, the theory of PEM of the multi-DOF linearity system has been constructed completely.(2) After study of six DOF vibration model of 1/2 automobile, the mechanics and mathematics model have been summarized. The road excitation of the above model has been confirmed. Based on the road excitation model, the pseudo excitation of the road has been constructed. First of all, using the real-mode PEM, power spectrum density of three responses(perpendicular acceleration of body, dynamic flexibility of suspension, relatively dynamic load of wheel)have been acquired. Due to the traditional power spectrum analytical method is mature in theory, a contrast between the traditional power spectrum analytical method and the real-mode PEM has been made. The results show that there exist errors under the real mode condition, because neglecting the damp of non-diagonal elements. So the following work is discussing of the plural-mode PEM. Using the plural-mode PEM, power spectrum density of three responses has been acquired. A contrast between the traditional power spectrum analytical method and the plural-mode PEM has been made. The results show that the curve can absolutely inosculate. Therefore the plural-mode PEM has the feasibility and accuracy when applied to automobile ride comfort.(3) After study of eleven DOF vibration model of tridimensional automobile, the mechanics and mathematics model have been constructed, and the method of calculating system static load has been confirmed. The four-wheel road excitation has been confirmed. Based on the above road excitation model, the pseudo excitation of the road has been constructed using the road surface spectrum matrix's character pair. Power spectrum density of three responses has been acquired based on the plural-mode PEM.(4) Based on GUI of MATLAB, the software of evaluating of automobile ride comfort based on PEM has been developed. This software includes three parts: simulation of responses of vibration model of 1/2 automobile, simulation of responses of vibration model of tridimensional automobile, evaluating of automobile ride comfort. Simulation curves of power spectrum density of responses and the results of evaluating of automobile ride comfort can be acquired by inputting vehicle parameter, road surface type and vehicle velocity. The operation of the software is simple and convenient.This paper tries to apply PEM to the analysis of automobile ride comfort, the results show that the feasibility and accuracy of the method. PEM will have a wide application in the automobile ride comfort analysis.