Vibration Isolation Optimization Of Full-float Suspension Based On VTPA

Due to the fact that commercial vehicle is often exposed to bad operation conditions,the structure borne noise caused by the road roughness and the vibration of the heavy dutydiesel engine is very serious. Meanwhile the air borne noise, like engine radiation noise,intake noise and exhaust noise is also very severe because of the large weight capacity of thecommercial vehicle. This noise will transmit into the cab and leads the driver to be fidgetyand tired which brings a huge challenge for the safe of the transportation. Researches aroundthe world are making great efforts to achieve a good interior noise condition of the cab.Recent study of the vehicle noise control is based on the target of A-weight soundpressure level. As A-weight sound pressure level ignore the human subjective feeling, cannotreflect the interior noise level accurately. In order to take the subjective perception intoaccount, more and more researches take sound quality as the target to analyze and control thevehicle interior noise. The vehicle sound quality design draws increasing attention of theresearcher.The research of this aim to solve the interior noise sound quality of the commercialvehicle at the steady-state conditions, which comes from the science and technologydevelopment project of Jilin province-acoustic optimization of full floating suspensionsystem (20130206031GX).Virtual transfer path analysis technology are used to build aVTPA model of the structure borne noise inside the cab. According to the loudnesscalculation method regulated by ISO532B, loudness contribution of each path are calculated,the critical path will be funded at the largest loudness contribution. Optimize the parameterswhich had a greater influence on the vibration excitation of the suspension to reduce theexcitation. Optimization analysis result has been validated to be effective.The main research Contents of this thesis are as follows:Virtual transfer path analysis model (VTPA) of the cab. The VTPA model has two main components: The first part is the structure borne noisetransfer function based on the vibro-acoustic model of the cab; the second part is thesuspension vibration excitation based on the rigid-flexible coupling model of the full floatsuspension.For the vibro-acoustic model, other parts of the cab exclude the body in white are takeninto account, meanwhile the coupling effect between the structure and the air is also underconsideration. The noise transfer function result from the model approach to the test resultwhich can be used to represent the property of the noise transmit.For the rigid-flexible coupling model, the connection between each body of thesuspension is according to the dynamic relationships of the full float suspension. TimeWaveform Replication method has been used to make the measured acceleration input themodel. The influence of the bushings is also under consideration. The rigid-flexible couplingmodel is proved to be correct by the road test.Finally, according to the basic principle of transfer path analysis, combine the noisetransfer function from the vibro-acoustic model and the vibration excitation fromrigid-flexible coupling model to build the VTPA model. The max absolute error between themodel synthesis results and the test results is1.9dB(A), the max relative error is3%, whichdemonstrates the virtual transfer path analysis model can accurately simulate the interiornoise.Loudness contribution analysis of the cab.According to the VTPA model, the sound pressure contribution of each path has beenattained. As the loudness calculation method regulated at ISO532B, the loudness of eachpath contribution has been calculated. The critical path has been funded at the largestloudness contribution. The Z-axis vibration excitation at the rear left suspension(RL_Z) isfunded to be the critical path to be optimized.Suspension vibration parameters optimization.In order to minimize the Z-axis vibration excitation at the rear left suspension, the RMSof the force between the cab and suspension is taken to be the objective function ofoptimization. Choose the radial stiffness of each bushing at the rear suspension as the designvariables.3level full factorial DOE analysis has been conducted and get27results. A response surface model has been built using the DOE results. An optimum has been attainedwith the help of response surface model, the interior noise in the cab reduce up to0.65dB(A),and the loudness reduce up to1.01sone. Based on the critical path of vibrationexcitation is optimized, a good improvement has been achieved, the structural optimizationaccording to sound quality parameter has been realized.