Research On Active Of Control Method Of Road Noise For Pure Electric Vehicles

With the upgrading of automobile product consumption in China,NVH(Noise Vibration & Harshness)performance has become one of the important factors to measure automobile quality and determine customers’ purchase intention.Pure electric vehicles are the main trend of the future development of automobiles.During the driving process,the contribution of middle-frequency and low-frequency broadband road noise to the noise inside the vehicle is significantly higher than that of traditional vehicles.Traditional passive noise reduction methods have limited noise reduction effects on middle-frequency and low-frequency noise.Active noise control technology can offset and attenuate the secondary sound source with the same amplitude and opposite phase as the primary noise source,which can achieve a quiet zone in a designated area.It has better noise reduction effect on low frequency noise.After analysis,the low-frequency noise in the pure electric vehicle mainly comes from the structural road noise generated by the interaction between the tire and the road surface.Therefore,the key to reducing the low-frequency noise in the vehicle lies in the active control of the transmission of noise to the vehicle structure(wheel center,suspension,chassis and body).Based on the above analysis,this paper studies the principle and implementation method of active noise control system.According to the characteristics of the road noise in the vehicle interior,a new adaptive active control strategy is developed to reduce the road noise in the pure electric vehicle.Structural road noise is caused by the excitation force generated when the tire and the road surface are compressed,rolled and released.Therefore,the road noise in the vehicle has a certain correlation with the vibration acceleration signals of different structural parts of the vehicle.The active control strategy of the road noise in the pure electric vehicle is as follows: First,the neural network is used to identify and construct the reference signal of the road noise in the vehicle through the vibration acceleration signal with higher coherence.Then,the improved feedforward FXLMS algorithm is used to reduce the noise of the road noise in the pure electric vehicle.According to the researched control method,following tasks are completed:The improved BP(Back Propagation)neural network algorithm is used to identify and predict the noise signal in the car.The established identification model was simulated and verified by the vibration acceleration signals of different structural parts of the vehicle and the noise signal of the driver’s headrest measured at the same time.During the research on active noise control algorithms,the enhanced generalized adaptive weight-constrained EGMACFx LMS algorithm is proposed based on the limitation of the reference signal and the error signal.Then,a PSO(Particle Swarm Optimization)based novel adaptive step size Fx LMS with a reference signal smoothing filter is proposed to further improve the noise reduction performance,called NASFSx LMS-PSO algorithm.Based on the proposed active noise control algorithm,a simulation model for the adaptive active control of road noise in a pure electric vehicle is built in MATLAB/Simulink.The noise reduction effectiveness capacity of the proposed active noise reduction algorithm is preliminarily verified by simulating different simulated noise signals.In the active noise control model built by MATLAB/Simulink,the noise signal and vibration acceleration signal collected by the actual vehicle are used as the reference signal of the active noise control model in the vehicle.When the noise signal is used as the reference signal,the noise reduction bandwidth can reach 300 Hz,and the noise reduction amount is concentrated in the interval of 5-12 d B(A).When the vibration acceleration signal is used as the reference signal,the maximum noise reduction can reach 20 d B(A).Based on the purified electric vehicle road noise active method,a hardware-in-the-loop test platform was further built to conduct noise reduction experiments.When the noise signal in the car is used as the reference signal,the noise reduction bandwidth achieved by the active noise control system can reach 120-260 Hz,the noise reduction is concentrated in 3-8d B(A),and the maximum noise reduction is17 d B(A).When the vibration acceleration signal is used as the reference signal,the active noise control system has a good control effect on the noise signal in the frequency range of 60-300 Hz.The noise reduction is concentrated in 2-7d B(A),and the maximum noise reduction is 13 d B(A).