Research On The Identification And Control Of Exhaust System Noise Source Based On Instantaneous Frequency Estimation

With the increasing demand for the vehicle riding experience,the NVH performance of the vehicle has become the key content of the automotive design.It is an important technical means to improve the performance of automobile NVH by accurately identify the source of automobile noise,analyzing the mechanism and controlling it.Taking the exhaust system as the research object,the theory of noise and vibration of the exhaust system is systematically analyzed and summarized.Briefly describe the theory of instantaneous frequency parameter estimation and deduce the key formula.This method is applied to the estimation of the engine speed,and the calculation method of the engine speed based on the instantaneous frequency estimation is established,and the non-contact speed measurement is realized,it overcomes many difficulties in the practical application of the measurement of the spindle speed of the conventional engine.The basic principle of speed calculation algorithm is described in detail.At the same time,the algorithm is verified by means of simulation analysis and experiment,which proves the feasibility of the algorithm.The noise and vibration test equipment and environment are briefly introduced.According to the test standard of vehicle noise and vibration,the exhaust system is tested under specific conditions,the noise level of exhaust system of the vehicle is checked,and the noise source identification test data is obtained.At the same time,the dynamic rigidity of the exhaust lug bracket and the rigid body modal of the powertrain are tested to determine the rationality of the design of the relevant components of the exhaust system of the test vehicle.The theory of order analysis is briefly introduced.The engine speed extraction algorithm based on instantaneous frequency estimation is used to extract the information of engine spindle speed from the test signal to realize the order analysis of exhaust system noise,and obtain the main order components and characteristic frequencies of exhaust system noise.According to the structural characteristics and operating characteristics of the exhaust system,the noise sources of the exhaust system are identified as low-frequency fluctuation noise,high-frequency burning noise and frictional noise,Helmholtz resonance noise and their corresponding characteristic frequency.According to the results of noise source identification,a noise control strategy and CAE simulation analysis route are proposed for the exhaust system.