Analysis Of Radiated Acoustic Field In Hybrid Electric Vehicles And Study On Noise Reduction

Compared with the pure electric vehicle,the hybrid electric vehicle(HEV)takes into account the characteristics of both the pure electric vehicle and the ordinary internal combustion engine vehicle,and solves the shortcomings of the short life mileage and the inconvenient charging of the pure electric vehicle which is an ideal new automobile solution.How to reduce the low frequency structural noise caused by the coupling of the structure and the acoustic cavity has always been a key and difficult point in the control of vehicle interior noise.At the same time,because the running condition of hybrid electric vehicle is very complex,the vibration and noise source and its dynamic characteristics have changed greatly compared with internal combustion engine and pure electric vehicle.Under the impact of noise sources such as motor,engine and dynamic coupling mechanism,the problem of in-car low-frequency noise is more complicated.In order to solve the problem of HEV low-frequency noise under mixed driving conditions,the main work of this paper is as follows:First of all,according to the different working modes of hybrid electric vehicle,the driving force at different vehicle speeds,the driver's binaural noise,the passenger's right ear noise and the vibration acceleration at the foot of the main and auxiliary driving system were analyzed and compared under the motor drive mode,hybrid driving mode and acceleration condition.The near-field noise and vibration acceleration amplitude of motor,engine,dynamic coupling mechanism and body plate were studied in order to determine the peak frequency and amplitude of each vibration noise source,so as to provide a reference for subsequent simulation analysis.Secondly,the theoretical basis,advantages and disadvantages of constant coherence function,multiple coherence function and partial coherence function were introduced.After choosing the partial coherent function method,the calculation of the partial coherent function was simply deduced.At the same time,according to the characteristics of the noise source of the hybrid electric vehicle,a multi-input and single-output sound source system model was established.The concept of "Sum of weighted coefficient" is introduced to improve the original partial coherence analysis.Then,the main source of HEV low-frequency structure noise was determined by comparing and analyzing the noise sources based on the vibration noise spectrum.In addition,with the help of Hypermesh and Virtual.Lab software,the finite element andboundary element models of the body structure grid and the acoustic cavity inside the vehicle were established.Then the excitation force is applied to the vehicle body mounting joint,and the acoustic contribution of each plate was analyzed by using the acoustic transfer vector(ATV)method.The existing plate acoustic contribution analysis method was improved.Taking the proportion of the acoustic energy of the field point to the total acoustic energy of the sound field as the weighting coefficient,the acoustic contribution of the plate to the multi-field point was weighted sum,and the main contribution plate was found.According to the modal shape diagram of the structure and the actual situation,taking the roof position as an example,the position which needs to be improved was plotted,and the stiffness was increased to reduce the vibration.In addition,After installing composite noise-reducing materials consisting of PET+PP and IIR on the HEV roof and floor,the initial noise was reduced.According to the analysis results,the total noise reduction amount is 3.2 dB after the noise reduction measures are taken on the relevant parts of the car body.The validity of the correlation control method is analyzed and verified theoretically.