The Study On Path Modeling Of Active Noise Control System In Pipeline

Active noise control can effectively reduce the low-frequency noise generated by air conditioning,ventilation ducts and engines,and it is light in weight,small in volume and easy to control.In recent years,it has become a popular research scheme.The existence of secondary path and secondary acoustic feedback in active noise control system seriously affects the cancellation performance of the control system.In this paper,the secondary path modeling and acoustic feedback in active noise control system are taken as the main research objects,and the methods of online secondary path modeling are mainly studied.The validity of the proposed online secondary path modeling method is verified by the built pipeline system.The main work is as follows:(1)The influence of path modeling in active noise control system on system cancellation performance is studied.For the active noise control model of pipeline,the effects of the components of different paths,the principle of active noise cancellation,Fx-LMS algorithm and the error of transfer function on the cancellation performance are analyzed.The results show that the accurate modeling of secondary path is the basis of the normal operation of the system,and when the phase error of modeling reaches 90 degrees,the system will not work properly.The existence of secondary acoustic feedback seriously affects the cancellation effect.Accurate modeling of feedback path is the basis of improving the performance of noise cancellation system in pipeline.(2)The method and performance of secondary path modeling are studied.The principles and performance of off-line modeling methods such as adaptive time delay estimation,dual microphone method and additional random noise method are studied.The principles and performance of Eriksson online modeling method,delay-based technology and variable step-size LMS algorithm are studied,and their performance are verified by experiment.(3)Aiming at the interaction between active control process and modeling process in online secondary path modeling,a method of online secondary path modeling based on generalized Sigmoid variable step-size normalized least meansquare algorithm is proposed.By establishing generalized Sigmoid function between step-size parameters and error signal,variable step-size parameters are obtained,which improves the convergence speed of the modeling filter,and the auxiliary noise power adjustment strategy is introduced to improve the steady-state performance of the system.The simulation results show that the algorithm can effectively improve the convergence speed of the system,eliminate the influence of Gauss white noise on residual noise,and achieve good steady-state performance and noise cancellation performance under the simulation of single frequency input signal and multiple frequency input signal.(4)Aiming at the problem of interaction between convergence of feedback path modeling and neutralization filter and noise cancellation performance of active noise control system,a new method of online feedback path modeling and neutralization is proposed.This method adopts self-tuning gain scheduling strategy of Gauss white noise,and introduces variable step-size LMS algorithm to update the weights of online feedback path modeling and neutralization filter.The simulation results show that the algorithm can effectively improve the convergence speed,reduce the steady-state error and achieve good noise reduction performance under the simulation of single frequency input signal and multiple frequency input signal.(5)Experimental research.The experimental platform of pipeline noise active cancellation system with STM32F407 as controller is built.The experimental scheme that the method of variable step-size LMS algorithm and the proposed method in this paper is used in online secondary path modeling and noise cancellation is designed,and the experimental results are analyzed.The experimental results show that the noise reduction of 350 Hz is 28 dB,and the noise reduction of multiple frequency can reach 21 dB in VSSLMS algorithm.In GSVSSNLMS algorithm,the noise reduction of 200 Hz is 35 dB,and the noise reduction of multiple frequency can reach 25 dB.The validity and effectiveness of the proposed algorithm are proved in practical system.