Research On Interior Active Noise Control Technology Of Pure Electric Vehicle

Pure electric vehicle has the advantages of low pollution,high energy efficiency and simple structure,and has a broad development prospect.Due to the lack of engine "masking",the problem of low-frequency noise inside pure electric vehicles becomes particularly prominent,which greatly reduces the comfort of drivers and passengers.Active noise control(ANC)technology has become an important noise reduction method for pure electric vehicles due to its strong ability to control low-frequency noise,flexible control target and convenient arrangement.However,the noise sources of pure electric vehicles are scattered.The interior noise signal has the characteristics of time-varying,wide-band and poor linearity.It seriously affects the noise reduction effect of active noise control.Therefore,it is necessary to study the active control technology of interior noise of pure electric vehicle.(1)The interior noise analysis of pure electric vehicle is established.For a pure electric vehicle,the interior noise acquisition experiments are carried out under constant speed and acceleration conditions.The frequency components and range of active control of interior noise are determined.The induction electromechanical magnetic wave which has strong correlation with the interior noise is deduced theoretically.The results show that the higher frequency components of the interior noise pressure level are concentrated in less than 500 Hz under the condition of constant speed.The order characteristics of the noise signal in the vehicle under acceleration condition are not very obvious.The higher frequency components of noise pressure level are concentrated in less than 1000 Hz.(2)The design and simulation analysis of active noise control system are established.Firstly,the mathematical model of active noise control is established.The theoretical derivation of adaptive filter and related adaptive algorithm is completed.Secondly,the secondary pathway identification model is established.An off-line identification method was used to complete the simulation analysis of the secondary path.The transfer function of the secondary path is obtained.Then,according to the characteristics of interior noise,a normalized variable step size filtering least mean square(FXNELMS)algorithm based on exponential function is proposed.The simulation analysis of single channel active noise control is carried out by using this algorithm.Finally,a multi-channel active noise control system is built.Multiple secondary pathways were identified.The proposed algorithm is used to simulate the multi-channel active noise control system.Simulation results show that the proposed algorithm is suitable for both single and multi-channel active noise control systems.The average noise reduction is about 32 d B(A)when the single-channel active noise control system is used.When multi-channel active noise control system is used,the average noise reduction is about 22 d B(A).(3)Based on the simulation of sound field in pure electric vehicle,the research of secondary sound source placement is established.Firstly,the theory of the placement of secondary sound sources is discussed.It is considered that the minimum power at a certain point in space is related to the frequency and distance of two sound sources.Then,the three-dimensional structure model of the test vehicle is established and simplified appropriately.The primary sound source is placed and the acoustic finite element method is used to complete the interior acoustic field simulation.Finally,secondary sound sources are placed in multiple positions in the car cavity.The optimal placement of secondary sound source is obtained by simulation.It provides guidance for the placement of secondary sound source in real vehicle test.(4)The development and experimental research of active control system for interior noise of pure electric vehicle are established.Taking a pure electric vehicle as the test object,the single-frequency and multi-frequency noise active control tests are completed in the vehicle.The active noise control test of real vehicle is completed under constant speed condition and accelerated condition.The test results show that for the single frequency noise signal,the noise reduction is more than 10 d B(A)after ANC is turned on.For multi-frequency noise signals,the noise reduction is 4-6 d B(A)after ANC is turned on.For constant speed conditions,the noise reduction after ANC is turned on is 1.5-3d B(A).Under the acceleration condition,the interior noise is obviously reduced,and a good control effect is achieved.