Research On Vibration Measurement System Based On Diffraction Grating

In recent years,with the rapid development of precision production and processing,micro mechanical facilities and electronic digital information technology,the diversity of the measured object causes the difference of the vibration mode of the measured object is gradually increasing.This not only points out the requirements of higher accuracy,faster measurement speed and higher resolution for vibration measurement,but also clearly points out that there should be wider adaptability for vibration frequency and measurement environment.In this paper,diffraction grating is selected as the core component of vibration sensing system,and a vibration measurement method of grating resonator based on grating displacement measurement system is designed.It is suitable for the increasing demand of measurement accuracy and more and more complex measurement environment.The main research contents and work of this paper are as follows:First of all,by studying the diffraction characteristics of one-dimensional grating,the principle of grating Doppler frequency shift,the principle of diffraction light interference and the theory of polarization optics,the optical structure of grating vibration sensor based on diffraction grating is designed,and the quadruple optical subdivision is realized by using the second diffraction,and the theoretical possibility of measuring four orthogonal signals is verified by the theory of polarization optics.Theoretically,the minimum resolution of grating vibration sensor after electrical subdivision can reach4.17×10^-9m.Secondly,in order to transform the displacement information measured by the grating sensor into vibration information,a"spring resonator"structure is constructed.In view of the vibration of the object to be measured and the harmonic oscillator when measuring the vibration of the grating harmonic oscillator,the mechanical model is established,and the principle of measuring the vibration of the harmonic oscillator is deduced theoretically,and the amplitude frequency curve of the grating harmonic oscillator amplitude varying with the vibration frequency to be measured is given;At the same time,in order to ensure the harmonic oscillator to vibrate in a single degree of freedom,the transverse vibration limiting spring is introduced.By analyzing the possible vibration forms and the factors affecting its stiffness,the structure is optimized,and the transverse vibration limiting performance is optimized.In addition,the mechanical structure of the grating resonator device is designed,and the amplitude range of the grating resonator device designed in this paper is obtained by theoretical calculation.The frequency range is 20Hz?500Hz.Finally,the overall framework of the grating vibration measurement system is built to test the performance of the grating sensor to ensure that it can meet the measurement requirements of the system.The vibration parameters under different vibration frequencies are measured to verify the amplitude frequency function by using the vibration source provided by the shaking table.Then,20 groups of data are measured for the simulated vibration with an amplitude of 5mm and a vibration frequency of 50Hz to analyze the source of the error,The correction and compensation method of the error caused by the amplitude frequency function is given,and the alignment error is analyzed by using the Zemax non sequential mode,and the angle tolerance of the grating relative to the sensor when it rolls,tilts and yaws is calculated.The experimental data show that the error of the system is less than 1%when the vibration amplitude is 5mm and the vibration frequency is 50 Hz.Compared with the parameters of traditional vibration measuring instrument,the grating vibration measuring system designed in this paper has the advantages of high precision,high resolution and fast response.