Acoustic Emission Source Location Based On Adaptive Filter And Phase Spectrum Analysis

Acoustic emission signal detection and processing technology is a popular non-destructive testing technology.It is widely used in many fields,including transportation,military industry,aerospace,new energy materials and large-scale industrial equipment detection.As a nondestructive testing technology,acoustic emission technology is mainly used to study the safety,stability and reliability of equipment,so as to quickly and accurately find the source of damage.Acoustic emission source localization algorithm is an important part of acoustic emission research.An acoustic emission source localization method which combines adaptive filter and phase spectrum analysis has been presented.It mainly includes the following aspects:(1)Before processing AE signal,it is necessary to denoise and filter it.In view of the unique attenuation characteristics of burst AE signal,adaptive filtering technology is applied to AE signal processing.In order to solve the contradiction between convergence speed and steady-state error of traditional LMS adaptive filter,an improved variable step size LMS adaptive filter algorithm is proposed in this paper.At the same time,aiming at the abrupt change of iteration error,the step factor is controlled by multiplying the djacent errors,and the selection and adjustment process of each parameter is introduced in detail.The MSE is used to evaluate the performance.The simulation results show that the algorithm improves the convergence speed significantly and reduces the steady-state error.Finally,the expectation function related to AE signal is established and substituted into the adaptive filter for filtering.The results are compared with the existing algorithms,and good results are obtained.(2)The traditional source location method takes the time when the signal crosses the threshold as the time when the acoustic emission signal arrives at the sensor.This method has large error.Starting from the information of waveform itself,this paper studies an all-phase FFT spectrum analysis method,derives its derivation formula and compares its performance with traditional FFT,and obtains its "phase invariant" characteristic.Accurate phase of the signal is obtained by phase spectrum analysis,and the relationship between phase difference and time difference is combined to obtain more accurate estimation of time difference of acoustic emission signal,which lays the foundation for source location.(3)In the research of source localization algorithm,2D source localization is extended to 3D source localization.The least square method and Geiger algorithm are combined to compare the performance of the algorithm with PAC’s software location algorithm and Newton’s iteration method,and then all-phase FFT spectrum analysis method is used to calculate the time difference.Based on the standard of mean square error,2D and 3D positioning experiments are carried out.The experimental results show that the source localization method based on allphase FFT spectrum analysis has the best localization performance,higher localization accuracy and lower mean square error.(4)A set of "AE detection and data processing system" is developed independently based on C#.The AE signal adaptive filtering algorithm,all-phase FFT spectrum analysis method,AE plane and spatial source location algorithm are integrated into the AE detection data analysis software.The main functions of the system include: AE signal acquisition module,signal processing module,signal processing result display module,AE source location module and AE signal processing result document saving module.The system can complete the real-time acquisition,playback and data processing,source location and pattern recognition classification of acoustic emission signals,and provide technical support for the analysis and processing of acoustic emission signals.