Research On Adaptive Active Control Of Road Noise Inside Vehicles

With the continuous improvement of automobile quality requirements and the increasingly fierce competition in the automotive market,the noise inside the car gradually becomes an important indicator for the user to evaluate the ride comfort and product satisfaction of the car.The noise generated by the vibration of the automobile structure,which caused by the interaction between the tire and the road during driving is an important component of the low frequency noise in the vehicle.And the noise is characterized by the low-frequency broadband noise,which is random and timevarying.Traditional noise reduction methods such as sound insulation,sound absorption,shock absorption,and sealing are mainly used to reduce middle-frequency high-frequency noise in the car.While active noise control technology can effectively reduce the low-frequency noise in the vehicle,which is complementary to the traditional methods of noise reduction.Active noise control technology,which based on the principle of acoustic interference,artificially introduces a secondary sound source generating sound waves to interfere with the primary sound waves in the canceled area to form a sound cancellation zone,thereby achieving the effect of noise reduction.In this paper,the principle and implementation method of active noise control system in vehicle interior are studied.And a new adaptive active noise control strategy for structure-borne road noise is proposed to reduce the noise inside a vehicle cabin according to the characteristics of vehicle interior structure-borne road noise.Because of the strong but non-linear multi-coherence between structure-borne road noise and the suspension vibration,the adaptive active noise control strategy firstly uses the neural network method with good non-linear mapping ability to predict the road noise in the vehicle through the acceleration signal of suspension vibration.And then a broadband feedforward active noise control strategy based on the FXLMS algorithm was combined to control the interior road noise.The control strategy is divided into three main functional modules: vehicle interior road noise identification module,secondary sound channel module and noise adaptive active control module.Based on the proposed control strategy,the main research work is completed as follows:The prediction module model of interior road noise based on BP neural network algorithm and the broad-band feedforward noise control model with FXLMS algorithm were built respectively.And a strategy model of adaptive active control for road noise in the vehicle is built.Based on the simulation model,a hardware-in-the-loop simulation system of active noise control for road noise is built.The performance of active control strategy model for road noise and the hardware-in-the-loop simulation system are validated respectively employing data measured in a car.And the simulation data of the suspension vibration signals and the noise signals of driver's seat headrest is collected at the same time based on three different road speeds of 60,80,and 120km/h.The strategy model simulation results show that the noise correlated with vibration signals was cancelled effectively and the controlled low frequency range was up to 60-100 Hz.The noise peak was reduced by about 20 dB with linear sound pressure level.The hardware-in-the-loop experiments achieve noise reduction bandwidth of about 20-80 Hz.In the frequency band of noise reduction,the noise reduction is mainly distributed in 2-10 dB,and the maximum noise reduction is approximately 15 dB with linear sound pressure level.A hardware-in-the-loop simulation system for broadband feedforward active noise control based on FXLMS algorithm is built.And a hardware-in-the-loop simulation system for feedforward broadband active noise control based on FXLMS algorithm with vibration signal as reference signal is built.Based on collected data of three different road speeds of 60,80,and 120km/h,the hardware-in-the-loop experiment is carried out.In the experiment,A-weighted sound pressure level attenuations of 10-20 dB(A)were measured for frequency range up to about 300-400 Hz based on different road speeds on common road surface.Both of the hardware-in-the-loop simulation systems have a maximum noise reduction of more than 25 dB(A).