A Design And Experimental Research On Adaptive Active Noise Control For Vehicle

Nowaday,people's requirement of driving comfortableness of automobile is higher and higher.Comfort has become one of the important indexes while people evaluating the cars they plan to buy.All kinds of the noise inside the car has a crucial effect on comfortableness.The method of traditional technology to control the noise is usually to use specific sound materials to insulate the interior noise.These methods have good effect while controling the high frequency noise signal,but it is still difficult to control the low frequency noise inside the car,which is derived from the vibration of the body structure and its radiation.Due to the need to increase a lot of sound insulation materials,it is difficult to achieve the goal of lightweight.While controlling the low frequency noise,active noise control technology can be effective,and this method does not need to add a lot of sound-absorbing material,and the increased cost of the system is limited.This technology can achieve a good balance between economy and comfort.Based on the research on basic theory of acoustics and sound linear equation,according to the superposition theory,a single channel feedforward structure of active noise control system has been designed.The paper deduced LMS algorithm and FXLMS adaptive algorithm,and analyzed the noise control algorithm from the angle of convergence performance and steady-state performance performance.According to simulation experiments,FXLMS algorithm could solve the problem of delay by assigning estimated channel transfer function.To solve the problem of secondary channel transfer function model identification,a off-line model is built and a kind of white noise injection method is adopted.Using LMS algorithm to calculate the estimates of the secondary channel transfer function.The accuracy of the estimated results are verified by Matlab simulation experiment;To solve the problem of the placement of secondary sound source and error acoustic pick-up,through the combination of interior noise data collection and analysis,based on simulation analysis on the interior sound field by the acoustical finite element software LMS Virtual Lab,successfully find the optimal position and get the strategy and requirements of the sound source placement.The simulation analys also provides guidance and support for the actual experiment.On the basis of the above theoretical study and simulation experiment,a active noise control system experimental platform is established.Taking a interior noise signal acquired from a domestic car as the input,using FXLMS adaptive filter algorithm as the control algorithm,to calculate the secondary sound source signal,error acoustic pick-up read the error signal as the feedback signal of adaptive filter weight adjustment.Using the established interior noise active control system,the experiments for noise signal of different frequency generated by the system and interior noise signal collected from a domestic car have been carried out respectively.The test results showed that the noise active control system could reduce the interior low-frequency noise effectivly.The noise value of specific frequency is reduced by 9?11 dB(Lin);The value of interior noise signal decreased by 4?6 dB(Lin).And the system converges fast,works stably,can meet the needs of interior noise active control.