Reserch On Vehicle Localactive Noise Control On Bumpy Road

Vehicle noise,vibration and harshness(NVH)is a key index to measure the performance of a vehicle.The size of the noise inside the vehicle has a great impact on the ride comfort.The traditional sound absorption and sound insulation methods have good suppression effect on the middle and high frequency noise.Compared with traditional sound absorption and insulation methods,Active Noise Control(ANC)has significant advantages in solving the problem of low frequency noise in the vehicle.Based on the principle of active noise control,this paper studies the active noise control in vehicle.Firstly,the principle of active noise control is studied in this paper.According to the good stability of the feedforward active noise control model,the feedforward active noise control structure is selected,the adaptive filtering algorithm is derived,and the stability of Fx LMS algorithm is analyzed.However,the classic Fx LMS algorithm is difficult to adapt to the noise of bumpy road to ensure the stable noise reduction effect due to its fixed step parameters when facing the interior noise of bumpy road.Therefore,an adaptive step-size filter-x least mean square algorithm(ASSFx LMS)is proposed in this paper,which can adjust the step size according to the size of the reference signal to ensure the stability of the adaptive process.In order to improve the performance of the algorithm,the particle swarm optimization algorithm is also used to automatically adjust the step size parameters,so that the adaptive algorithm always maintains an ideal step size.In order to verify the performance of the proposed algorithm,the simulated standard SαS pulse noise was used as the reference signal for MATLAB simulation.The simulation results show that the proposed algorithm has improved the noise reduction stability and amplitude under different levels of pulse noise compared with other algorithms.In order to further verify the performance of the proposed AASFx LMS algorithm in practical applications,through the road noise data collected by real vehicles,the hardware in the loop test,under different working conditions of road noise,the proposed algorithm has a maximum noise reduction effect of 12 d B below 100 Hz low frequency noise.Because the sound pressure reduction point of active noise control is mainly at the error microphone,and in the active noise control system of the vehicle,the error microphone cannot be placed at the human ear,resulting in a substantial decline in the noise reduction performance of the human ear.Therefore,the virtual sensing method is adopted in this paper to improve the noise reduction effect of human ear.In order to explore the stability of Auxiliary Filter(AF)method and Remote microphone(RM)method when reference signal frequency bands are inconsistent in the training stage and control stage,Simulink is used to simulate the noise of different frequency bands respectively.The results show that RM method has better stability under different frequency band reference signals.In order to further verify the performance of the RM method,ANC experiments were conducted on the active noise control method of the RM method and the active noise control method without virtual sensing in the laboratory by using noise signals of different frequency bands.The results show that the performance of the RM method is not much different from that of the active noise control method that directly places the error microphone in the target quiet area.Compared with the active noise control method that only places the error microphone in the physical position,the noise reduction performance of the RM method is greatly improved.Therefore,RM method is feasible for the research of local active noise control in vehicle interior.On the premise that the previous work can be carried out,this study has arranged an active noise control test platform inside the vehicle and conducted ANC tests on the bumpy road of the vehicle.First,when the vehicle is stationary,secondary channel identification is performed,and offline identification of virtual secondary channels and physical secondary channels is performed by playing white noise through secondary speakers.Then drive the vehicle at a constant speed of 30 km/h on a bumpy road surface and train the observation filter.After completing the secondary channel identification and training stages,the error signals at the virtual error microphone when the ANC system is turned on and off were measured on the same road at different vehicle speeds.The experimental results show that the proposed local active noise control system has a good suppression effect on bumpy road noise under four different uniform speed conditions.