The Study Of Vibration Measurement Technology Used Of Fiber Acousto-optic Modulation

The method of laser heterodyne based on the laser Doppler effect has the advantages such as high accuracy and non-contact, but the system is more complex and the distance is short, therefore this paper studied the vibration measurement technology based on fiber acousto-optic modulation and designed the system. Using acousto-optic modulation technology be able to get stable frequency shift, using optical heterodyne measurement, has the advantage of high precision and high range resolution and low dc drift. The use of optical fiber, can achieve long-distance measurement and transmission, reducing external electromagnetic interference and improve SNR; Designed intelligent signal processing system, can achieve vibration signal acquisition, processing and display, the system can also be monitored and controlled; The design of PC software based on virtual instrument, can be digital filtering and spectrum analysis for collected signals.Firstly, analyzed the application and the importance of vibration in every engineering field, analyzed the principle of several existing vibration measurement technology, proposed fiber acousto-optic modulator vibration measurement technology for the deficiencies of the existing technology; Analyzed measuring vibration principles and methods using acousto-optic modulation technology, a vibration system is designed and the mathematical model is deduced, can realize the speed,acceleration and displacement measurement; Especially for shaft and other rotating body designed differential measurement model, it can be obtained the vibration of the object in a two-dimensional plane;In order to realize the function of the system, designed the optical system and the hardware system. Selected the laser light source, and designed a light frequency stabilization module; Selected the photodetector and designed the signal acquisition circuit; Designed the structure of optical fiber coupling based on the existing theory, on the front end choose direct coupling method, the back-end choose lens coupling way; Embedded Intelligent microprocessor STM32F407 in signal processing unit, to realize the collection of the signal and operation, can monitor the status of the system and compensate for it; Selected the touch screen to realize human-computer interaction, can show the result of the vibration measurement,also can input the command to control the system; In order to realize the numerical analysis and specturm analysis for the acquisition signal, designed the PC signal analysis software based on virtual instrument and DAQ card.Tested the performance of vibration system, determined the center frequency and bandwidth of the acousto-optic modulator, calculated the size of the deflection angle of the diffracted light on the center frequency, for the design of fiber coupling structure provides a theoretical basis; Used the vibration system using acousto-optic modulation detected the vibration of standard vibration table, and designed the contrast experiment with piezoelectric sensors detected the vibration of machine, proved the feasibility of the designed vibration system, has obvious advantages compared with piezoelectric sensor;Finally analyzed the error source of the vibration measuring system, and put forward the error control measures, help to further improve the overall performance of the system.