Fast Algorithm Research And Realization Of Active Noise Control In Vehicle

With the development of society,our country has made great progress in economy.People's way of travel has also produced a great change,the emergence and development of the car,greatly facilitate people's lives.At the same time,the noise in the car has also caused people's attention.The interior noise is mainly low frequency noise,and the traditional passive noise reduction technology is mainly used to control medium and high frequency noise,but the effect of low frequency noise reduction is not obvious.Active noise reduction is mainly used for low frequency noise control.Therefore,this paper proposes the use of Active Noise Control(ANC)technology to achieve in-car Noise Control.From the perspective of practical application,this paper completed the overall scheme design,algorithm design and performance optimization of ANC system,and finally completed the design and implementation of the entire experimental system.The principle analysis,structure selection and design of active noise reduction system are carried out.Based on FIR filter,feedforward structure is adopted to build a complete ANC system.Explore the factors that affect the noise reduction effect,and analyze the importance of secondary channel to noise reduction system and its influence on system stability in detail.Due to the complicated and changeable environment in the car,the idea of self-adaptation is added to the active noise reduction system.LMS algorithm is used to update the filter weight coefficient,and the filter structure is optimized according to the noise reduction effect.The existence of secondary channel leads to the difference between the output signal of the filter and the cancellation signal that arrives at the noise reduction region.In this paper,the secondary channel is estimated to improve the noise reduction algorithm,and the FXLMS algorithm of filtering is obtained.Aiming at the problem of too much computation when the filter length of ANC system increases,a new algorithm of partial coefficient updating of the filter is proposed.The relationship between the length of the secondary channel and the main channel and the simulation effect is studied.This paper analyzes the computational amount of FXLMS algorithm,and proposes an improved algorithm of partial coefficient update of filter to reduce the computational amount.The influence of various factors on filter coefficient updating is analyzed,and a reasonable selection criteria for updating items is designed.Secondly,the simulation test of the filter partial coefficient update algorithm is realized by MATLAB to verify the feasibility and superiority of the algorithm.The length of the filter was increased to order 128 to achieve the perfect estimation of the ANC system on the secondary channel and the main channel,and further improve the noise reduction.In order to solve the problem of slow convergence caused by updating partial coefficients of filter,a variable step size algorithm based on inverse tangent function is proposed.Under FXLMS algorithm,the requirements of convergence speed in different stages of system operation are analyzed.The correlation between convergence step size and system stability is explored,and the corresponding criterion of convergence step size and noise reduction effect is designed reasonably.Simulation verification of variable step size algorithm was completed based on MATLAB.Compared with FXLMS algorithm and other variable step size algorithms with better performance,the convergence speed of the new algorithm was verified to be significantly faster than other variable step size algorithms.Complete the combination of partial update algorithm and variable step algorithm and C language implementation.Experiments were conducted to test the denoising effect and convergence speed of the new algorithm,and to compare it with FXLMS algorithm to verify the superiority of the new algorithm in terms of noise reduction and convergence speed.In the laboratory environment,the vehicle noise environment was simulated,and the single-channel ANC system was used for noise reduction experiment.According to the principle of real-time and acoustic interference,the spatial layout of each module in the system is designed reasonably.By analyzing the noise reduction and the convergence speed through the three-dimensional noise diagram,it is verified that the new algorithm increases the noise reduction depth and speeds up the convergence speed in the practical application.