Research On Selective Attenuation Of Vehicle Cabin Noise Based On Active Control

On the basis of the project"Analysis and control of car interior noise"and the NVH group's former study experience, this article has proposed a research strategy of active control of car interior noise by selectivity after studying a lot of documents on Active Noise Control technology.According to the thorough research of each method for active noise control, the paper proposed a method for frequency-selective active control of car cabin noise based on digital filter of primary noise signal and adaptive algorithm. Through the computer simulation, it analyzed the influence of digital filter performance on the effect of adaptive active noise control and confirmed a design method of digital filter and design parameters of digital filter.According to the computational complexity and numeric stability, the article studied every adaptive algorithm employed on the active noise control technology and confirmed the algorithm of the study was adaptive least square mean FIR filter. Though the computer simulation, it analyzed the affection of step size and filter length on the convergence stability and speed and reasonably selected the filter length and step size as the control parameters.Based on the Least Square Mean method which is broadly applied on the active noise control technology, the paper calculated the frequency selective LMS algorithm and the formula equation for the application of the algorithm on active noise control; it established the Simulink model for the presented algorithm and analyzed the adaptive attenuation simulation with single tone noise signal and narrow band noise signal demonstrating that the simulation result was identical with theoretic solution and the presented algorithm was valid, at last ,the control parameters of filter performance parameters and step size and filter length of adaptive filter was decided.According to the seminar's former study experience, the method of calculating primary signal using engine rotational speed signal as referenced signal was confirmed. The two order active low pass analog filter was designed as anti-aliasing filter and reconstruction filter. The error signal amplifier was improved to make sure that the amplifier gain was changeable. At last, it was made sure that the capability of the adaptive controller was optimized.The essential parameters such as word length and sample speed of the control system were ascertained considering the characteristic of the main ECU chip in the controller. And the system control program such as each module code and digital filter and adaptive algorithm was finished among the Silicon Laboratories integrated development environment. Lastly, the control program for the single channel feed forward selective adaptive active noise control system was finished with the simulation result parameters after iterative debugging test.Finally, the single channel feed forward adaptive active noise control system was established in the anechoic chamber and implemented the experimentation of active control of the noise for selectivity in the vicinal of the left ear of the copilot on the stable operating mode, demonstrating that it was feasible to control the vehicle interior noise by selectivity with AANC and that the presented method of selective active noise control was effective.