Research On Stability Of Vehicular Interior Active Noise Control System

Vehicular noise is easy to make drivers and passengers mentally upset and more likely to feel tired,which will bring many hidden dangers to passengers' mental and physical health and affect comfort.With the development of the national economy and the automobile industry,users' attention to car performance has gradually changed from fuel economy and power to ride comfort.And the automotive industry's demand of automotive NVH performance has gradually increased.The traditional passive noise reduction has a limited effect on reducing low-frequency noise in the car,while the active noise control technology has a better control effect on mid-low frequency noise.However,there are many key core technologies of active noise control systems that have not been cracked,such as the real-time accurate identification of the primary sound field,the convergence of the unsteady state sound field active control system,and the stability of the control system.This paper focuses on the stability control of active noise control systems.This dissertation first analyzes and deduces the adaptive filtering principle and adaptive notch filter algorithm,and proposes a variable step size algorithm to improve the convergence speed of the active noise control system,and simulates and analyzes the different values of various parameters of the variable step size algorithm.The variable step size parameter with the best control effect is optimized.and proposes a scheme to maintain the stability of the system when the car opens and closes the window.Then it analyzes the causes of the noise in the car,deduces the relationship between the main peak frequency of the low-frequency noise in the car and the engine speed.In the Simulink environment,a model for offline identification of secondary paths using time delay estimation method is established,which simplifies the complexity of secondary paths.The adaptive notch filter algorithm with fixed step size and variable step size was used to analyze the noise of single frequency and three frequencies.The simulation results show that for a single frequency noise source with an amplitude of 4.2Pa,The amplitudes after variable step and fixed step algorithm control are 0.3Pa and 0.5Pa respectively.For three frequency noise sources with amplitude of 7Pa,the amplitudes after variable step and fixed step algorithm control are 0.6Pa respectively.Compared with 1.0Pa,the variable-step algorithm is slightly better than the fixed-step algorithm,and the convergence speed is twice as fast.Then,the software and hardware of the active noise control system are developed,and the secondary speakers,power amplifiers,error microphones and other acoustic devices suitable for the active noise control system are selected.The software modules include the secondary path identification program and the active noise control program.Then,a hardware-in-the-loop adaptive noise active control system was built indoors,and the fixed-step and variable-step algorithms were used to actively control the interior noise of the vehicular at constant speed and acceleration.The test results show that the variable-step algorithm is darker than the second-order noise corresponding to the chromatogram after the fixed-step algorithm cancels,and it has a better effect on noise tracking control when the car accelerates.When simulated constant speed conditions,the variable-step algorithm has twice the convergence rate of the control system of the fixed-step algorithm.However,the control effect of the variable step size and fixed step size algorithms is not much different.The peak frequency noise reduction is about 30 dB,which can be used for real vehicle control of different needs.A low-frequency noise adaptive active control system in the vehicle was built on the actual vehicle,and the control effect and stability of the system were tested and verified.The test results show that the system can work normally under the acceleration condition of the automobile engine,and the engine order noise Has a good offset effect.Under the same constant speed condition,the variable step size algorithm has twice the convergence speed than the fixed step size algorithm.For the selected engine secondorder noise frequency of 48.5 Hz,the peak noise reduction of the variable step size and fixed step size algorithms are respectively It is 17.47 dB and 9.65 dB.For the selected second-order frequencies of 80 Hz and 96 Hz,the variable step and fixed step algorithm peak frequency noise reduction is about 28 dB,and the final cancellation effect is not much different.When the window of the car is opened and closed,the most suitable secondary path is selected through the window opening and closing state.The variable step algorithm can converge and have a good noise reduction effect.The peak frequency noise reduction is about 25 dB.It takes about 0.2s to converge and work steadily.Finally,summarize the full paper,the research conclusion is given,and the suggestions for further research are clarified.