Research On Dual Channel Vibration Measurement Technology Of Fiber Laser Interference

With the rapid development of high-tech industry,especially for industries such as precision machine tool machining,the demand for precision and reliability of vibration measurement is increasing day by day.Laser interferometric vibration measurement technology was the most comprehensive measurement technology among multiple vibration measurement technologies.Aimed at the phenomenon that the accuracy of domestic laser vibration measuring instruments was generally low,the signal interference was more serious and most of them are single point measurement.This paper took precision machining machine tool as the research object.The dual-channel vibration measurement technology based on optical fiber laser interferometry was proposed,which can realize the dual-channel measurement with high precision and high signal-to-noise ratio,and made the measurement system more stable and accurate.Firstly,the key technologies and mathematical methods needed by optical fiber laser interferometry for vibration measurement were studied,based on which a mathematical model was established.The application of Doppler effect and optical heterodyne technology made the system have higher measurement accuracy.The stable frequency difference of 100 MHz was obtained by acousto-optic modulation,which not only met the requirement of heterodyne measurement,but also improved the measurement resolution.The optical fiber transmission characteristics were analyzed and the optical fiber path was built,which replaced the traditional air path and enhances the anti-interference ability of the system.The design of double channel measurement improved the applicability of the measurement system.Secondly,the selection and circuit design of the key photoelectric devices required by the vibration measurement system were completed.Through performance analysis,a semiconductor laser with low noise,high output power and good coherence was selected,and its overall drive circuit design was completed.Photoelectric conversion was accomplished by photoelectric detector with high responsiveness.The research and design of optical fiber,collimating probe,circulator and other optical fiber passive components,so that the overall optical path has a certain adaptive measurement distance and anti-interference ability;In order to filtered the Doppler frequency shift signal,the related signal processing circuits such as frequency selection amplification,demodulation and filtering were designed.Then completed the digital signal processing algorithm research.According to the relationship between PSD and autocorrelation function,fast correlation analysis was realized by used fast Fourier transform,so that the response speed of measurement system was improved.Doppler signal was extracted from the noise of the same frequency band to improve the resolution of the system.In addition,the inversion compensation algorithm improved the stability of the system and improved the amplitude-frequency and phase-frequency characteristics of the system.Finally,the test and verification experiment of the measuring system,the field vibration measurement and the related uncertainty evaluation were carried out.It can be found that the vibration measuring system had good adaptive ability and the synchronization of the two channels was good,and the relative error was less.In addition,the field vibration measurement showed that it was reliable for the vibration analysis of machining machine tools.Traceability analysis was carried out on the uncertainty affecting the measurement system,and the final uncertainty assessment results showed that the uncertainty of the system was less than 0.6%.The measurement was reliable and instructive to some extent.