Research On Full Vehicle Vibration Coupling Of The FR Automobile

Since the financial crisis sweeping the world in2008, China’s automobile industry hasushered in the rapid development in the last couple of years. In2011, the number ofpassenger cars in China exceeded50million. From2006to2011, the sale quantity ofChina’s passenger car is generally on the rise. Under this enterprising consumpsion demandcharacteristic, the automotive product development has followed the technical route of safety,energy conservation, environmental protection, and intelligence, meanwhile, more attentionhas been payed on improving the quality of the car of the development model, and the voiceto improve car comfort becomes louder and louder, which requires us to do some research onthe vehicle vibration.Less work has been done on the coupling vibration by Scholars both at home and abroad,while much more on the single direction vibration relatively.Some research work has been done on vehicle vibration coupling in this paper, the main taskis to establish the mathematical vehicle vibration model accord with the actual situation, andto solve the vibration response with fourier transform, at first random road alone has beenput in to realize vibration simulation and analyse the vehicle vibration coupling factors; thenboth the simplified engine and random road incentive has been put in to carry on simulationand analysis, according to the parameters affecting the vibration coupling, some work hasbeen done on the optimized matching.The main contents are as follows:(1) Coupling vibration modeling of the FR automobileCombined with the research direction, based on certain assumptions, and according to theactual arrangement of the FR automobile, a quarter of plane vehicle vibration couplingsystem of nine freedom has been established to simplify the model, the model focuses onconsidering the driving wheel and the drive axle vibration, which involves the verticalvibration between rear axle and the body, the longitudinal vibration between rear axlenon-sprung mass and the body removed rear axle non-sprung mass, and the driveline torsionvibration.Mutual excitation relations among vertical vibration, longitudinal vibration and transmissiontorsional vibration has been built, according to Lagrangian approach, the mathematicalmodel has been deduced.(2) Method study of frequency domain solution of the FR automobile’s coupling vibrationMathematics model analysis and decomposition has been done to the coupling vibrationmodel, based on Fourier transform the vibration frequency response functions and the amplitude-frequency characteristics has been deduced, and the vibration response spectra,spectral matrix, and the corresponding Root-Mean-Square value in response to differentexcitation spectrum input could be calculated, which provides a theoretical basis forvibration coupling simulation and the parameter analysis.(3) Vehicle vibration simulation&paremeters analysis of the FR automobileAccording to the existing car parameters, to understand the inherent characteristics of the car,the natural frequency relation to corresponding vibration form has been solved as well asanalyzed.Based on the theory deduced from the frequency domain, the simulation program has beenmade out; road random excitation alone will be input frequency domain simulation toanalyze the impact of the road grade, driving speed to vehicle vibration, and to explore theimpact of vertical vibration on the longitudinal vibration, torsion vibration.Then two incentives at the same time will be input to realize vibration simulation, the engineincentive could be simplified, and the road random excitation power spectrum deserves abrief description, then the excitation spectrum matrix could be established, according to theMIMO theory, programming, and the response power spectrum under the two incentive aswell as the output response of the Root-Mean-Square value could be calculated, whichprovides analysis of data to explore the incentive effects of vibration coupling, and thevarious parameters on the coupled vibration.In this paper, combining with present development situation of the FR automobile, the1/4vehicle coupling vibration model has been built, the method study of frequency domainsolution of the FR automobile’s coupling vibration has been done, and the system vibrationfrequency response, amplitude frequency characteristics and power spectral density ofvibration respose, the root mean square value has been calculated; vibration couplinganalysis under road random excitation alone has been done, considering the suspensionstiffness, load and other factors on the vehicle vibration coupling; Then the two incentivevibration coupling has been analyzed, considering both the engine incentives and roadexcitation, analyzing the impact of the suspension stiffness and other parameters on thevibration coupling. The conclutions has provided a theoretical basis in order to reduce theextent of vibration coupling, improving vehicle ride comfort, as well as optimizing vehicleperformance.