Research On The Identification Method Of High Mileage Noise Source Of A SUV With Uniform Speed

The vehicle high mileage NVH performance is the NVH performance of a car after a certain mileage,and its essence is the durability of the car’s noise and vibration.The performance of high mileage NVH not only affects the comfort of the car,but also affects the repurchase rate of the car and the residual value of the used car,which is an important performance of the car.Therefore,identify the reasons of high mileage NVH performance attenuation accurately and efficiently is the basis for improving automobile noise and vibration durability.This paper studies the varation characteristics of noise sources in the high mileage,and proposes a new identification method of vehicle high mileage noise source,which is mainly based on the theory of Operational Transfer Path Analysis.The formation mechanism and various identification methods of the main noise sources of the automobile are analyzed and studied.Take a SUV as the research object,select five representative mileages such as 0km、3000km、20000km、40000km and 50000 km,carry out the vehicle interior noise source diagnostic test under all representative mileages,obtain acoustic and vibration signals of the car driver’s left and right ears,engine and tire surface in the near field under operational condition,the driving condition is 60km/h,the road condition is outdoor straight asphalt pavement and in order to achieve the mileage accumulation of 0km to 50000 km,the adaptive testing of simulate the actual driving state of the user is carried out on the public road.Through the study of the varation characteristics of the driver’s left and right ears,the engine’s surface and the near-field acoustic and vibration signals with the increasing mileage,we find the cause of the attenuation of the interior noise in high mileage.Take advantage of the noise decomposition technology based on OTPA theory,we first decompose the interior noise under various mileage numbers into engine noise,road noise and wind noise,and determine the number of uncorrelated excitation sources and the contribution of each excitation source to the driver’s right ear noise.Then,these excitation sources are decomposed into air-borne noise and structure-borne noise according to the transfer path,the decoupling of the transfer rate between the excitation source response and the internal response of the vehicle is realized,and the structure-borne noise of the front suspension is initially identified as the largest contribution to the interior noise under high mileage.Through the correlation analysis and order analysis for vibration signals of tire axle head,we finally identify the cause of the attenuation of the interior noise performance,and carry out a series of confirmatory tests,the reliability and validity of the identification method is verified.