Study On Transfer Path Analysis Method Of Interior Structure-Borne Noise Based On Inverse Substructure Method

Transfer path analysis(TPA)is one of the main testing analysis methods to study vehicle vibration and noise.In the traditional TPA method,it is necessary to disassemble the excitation source and then get the uncoupled frequency response function inherent in the transfer path,but it is difficult to get it for the vehicle system.In this paper,the inverse substructure method is proposed to obtain the frequency response function of substructure directly from the frequency response function of system level to replace the uncoupled frequency response function.Based on the theoretical formula of frequency response function of system derived from the characteristics of substructure and connecting components,the essential relations among the frequency response function of system,frequency response function of substructure and coupling dynamic stiffness matrix of connecting component are obtained,and then the frequency response function of substructure is calculated directly from the frequency response function of system level based on the inverse substructure method.By establishing the lumped parameter model,the validity of the theoretical formula of the frequency response function of substructure of the inverse substructure method is verified by using the calculated frequency response function of substructure.Combining the frequency response function of substructure calculated by inverse substructure method with the parametric load identification model of operational transfer path analysis with exogeneous(OPAX)method,a transfer path analysis method based on inverse substructure method is proposed.The transfer path analysis method based on the inverse substructure method is applied to the vehicle interior structure-borne noise analysis.Under the idle speed and constant acceleration conditions,the frequency spectrum analysis,speed extraction technology and order tracking analysis technology are used to understand the vibration and noise level in the vehicle.The frequency response function of the system is measured by the hammering technique,the coherence function and the frequency response function estimation method.The frequency response function of the substructure is calculated from the frequency response function of the system based on the inverse substructure method and the virtual decoupling method.The two methods are compared with the uncoupled frequency response function measured by the reciprocity principle from the passive side of each mount to the front floor of the cab.The results show that the frequency response function of substructure calculated by inverse substructure method is better.Collect the operating data and calculate the frequency response function of substructure from the passive side of each mount to the target and the indicator points based on the inverse substructure method,then combine the parametric load identification model to identify the load,analyze the contribution of the transfer path of the vehicle interior structure-borne noise,and identify the main contribution path.The results show that the Z-direction of the rear mount has the largest contribution to the vehicle interior structure-borne noise under the second-order condition.The advantage of this method is that it does not need to disassemble the excitation source,which greatly reduces the time required to measure the uncoupled frequency response function,makes up for the disadvantage that the reciprocity principle measurement of OPAX method is not easy to implement in some target locations,and further improves the TPA method.