Research And Application Of ANC System Of Household Air Conditioning Indoor Unit Based On FbLMS Algorithm

In order to improve people’s living and working comfort,home air conditioner has been widely used.However,more and more attention has been paid to the noise problem of household air-conditioner indoor unit.Frequent exposure to noise environment will not only cause certain interference to people’s work and life,but also greatly harm their health.Passive noise control can eliminate most of the medium and high frequency noise,but it can not effectively eliminate the low frequency noise which is more harmful to people’s health.The advent of active noise control(ANC)technology makes up for this shortcoming and can effectively suppress the low-frequency noise.Therefore,this paper studies the active noise control of the indoor unit of household air conditioner.Firstly,the basic principle of active noise control is studied,and the basic adaptive active noise reduction algorithm is derived and analyzed.This paper focuses on the characteristics of feedback active noise control system,and makes theoretical derivation and analysis of the basic algorithm.It is concluded that the feedback ANC system and its feedback least mean square(FbLMS)algorithm can eliminate the problem of acoustic feedback better.In addition,the secondary channel problem in ANC system and the necessity of modeling are also studied.Secondly,through the actual measurement and analysis of the noise of the indoor unit of the household air conditioner,the characteristics of low frequency,narrow band and periodicity are obtained.According to the noise characteristics,the characteristics of ANC system and the practical application of the subject,the feedback ANC system and its FbLMS algorithm are determined.At the same time,aiming at the defects of the existing basic structure of the algorithm,the main channel and secondary channel synchronous variable step algorithm is proposed for the ANC system of domestic air conditioner.Through the modeling and simulation on Matlab,the improved algorithm has achieved good results in convergence speed,modeling accuracy and noise reduction performance.Finally,based on the research of the enhanced FbLMS algorithm,the hardware platform of ANC system for air-conditioner indoor unit is built.FPGA is utilized as the ANC system controller,and the algorithm is implemented by using Verilog HDL.TheExperiments show that the improved FbLMS algorithm can make the ANC system effectively suppress the fan noise of the household air-conditioner indoor unit,and the noise reduction can reach up to 15 dB.