Research On Methods Of Vehicle’s Wheel Center Forces Identification And Response Contribution Rates Calculation

Road excitation is one of the main excitation sources of automobile’s noise and vibration.The forces acting on the wheel center include the translational forces in three directions and the moments in three directions.Identifying the wheel center forces and computing each degree’s contribution rate to vehicle’s noise and vibration accurately is very meaningful for vehicle’s NVH performance development and improvement.The main contents and conclusions of the paper are as follows:(1)Based on the frequency domain direct inverse method,the wheel center forces identification method is studied.The method of calculating the moment-acceleration transfer functions with multiple force-acceleration transfer functions and excitation points’ coordinates is studied.The number of the response points and the number and the location of the excitation points are clearly stipulated.In order to identify and verify the wheel center forces,the number of the response points should be greater than twice the number of wheels.And in order to improve the condition number of the transfer function matrix,the number of the response points is required to be close to four times the number of the wheels.The number of the excitation points on each wheel should be greater than or equal to 3.And the location of the excitation points should be chosen such that the vehicle structure between the excitation points and the wheel center is approximately rigid,that is,there is no resonance frequency in the frequency band of interest.(2)The accuracy test method of the identified wheel center forces is proposed.The correctness of the wheel center forces identification method and the accuracy test method are verified by a road excitation identification experiment.The accuracy of the identified wheel center forces is verified by comparing the measured response and the identified response of each sensor’s +Z direction.The results show that the identified response is consistent with the measured response in 0-400 Hz,and they are both small in 100-400 Hz,the absolute error is below2-4-10.005 m ×s ×Hz,and the relative error is small in 0-100 Hz.(3)A correlated excitation energy flow model is proposed by combining the multi-reference TPA method and the virtual coherent method.The data of the road excitation identification experiment is processed.According to the correlated excitation energy flow model,the contribution of the transfer path of the front left wheel center +Z,+Y and the front right wheel center +Z and the forces of the front left wheel center +Z,the rear left wheel center +Z and the front right wheel center +Z is relatively big to target point’s response.(4)Complicated calculations are required when computing the transfer functions between the wheel centers and the response points.A computation program is developed to simplify this work.The program only need an XML file related to the excitation points’ coordinates and the transfer function UFF test file as inputs and give the transfer functions between the wheel centers and the response points as outputs.Thus the work of the wheel center force identification and the contribution rate calculation can be done easily.