Dynamic Characteristic Test And Modal Analysis Based On Laser Doppler Vibration Measurement

With the rapid development of modern engineering technology towards precision and intelligence,the vibration problems of MEMS devices,mechanical parts,equipment and engineering structures have become increasingly prominent.Modal analysis technology is used to analyze the vibration characteristics of the measured object,which can obtain the natural frequency,damping ratio and other modal parameters.And it provides technical basis for the optimization design,damage detection and performance evaluation of devices,equipment or engineering structures.In this paper,the heterodyne interferometry system is used for signal acquisition,and the least squares complex frequency domain method is used to extract modal parameters.It has the advantages of high measurement accuracy,fast calculation speed,high signalto-noise ratio,high sensitivity,and strong stability.The summary of the main work completed in this paper around the dynamic characteristic test and modal analysis based on laser Doppler vibration measurement is as follows:(1)The paper has done optical path design,circuit demodulation processing and signal processing design,and built a heterodyne interference vibration measurement system;(2)The vibration measurement of typical MEMS devices such as phononic crystals,tuning forks and microphones was carried out using the built heterodyne interference vibration measurement system.The modal parameters were extracted using the least squares complex frequency domain method,and the frequency response function was curve-fitted.,The goodness of fit obtained is above 88%;(3)The vibration measurement of the piezoelectric ceramic is completed,the amplitude of the piezoelectric ceramic torus is scanned and the vibration mode of the torus is obtained.(4)The human carotid artery was measured by the built heterodyne interferometric vibration measurement system,and the vibration signal of the carotid artery was obtained.After processing such as noise reduction and filtering,a higherquality pulse wave signal was obtained.