Design Of Self-mixing Vibration Measurement System By Solid-state Laser

Micro-vibration measurement is an important research direction in the field of engineering technology.A commonly used method of measuring micro-vibration is to perform non-contact non-destructive measurement using light interference.Self-Mixing interference measurement has many advantages such as simple structure,high sensitivity,corrosion resistance and stable operation in harsh environments,and it has attracted strong interests from experts and scholars in the field of micro-vibration measurement.Semiconductor lasers are commonly used as light sources for sensing measurement with SMI.Solid-state lasers become the preferred source of the SMI micro-vibration measurement system because of the advantages which compared with semiconductor lasers,such as the high frequency stability,the strong energy storage capacity and the narrow linewidth.Therefore,the design and development of the system of SMI micro-vibration measurement using solid-state laser have a broad engineering application prospect.The main research contents of the thesis include the following aspects:Firstly,on the basis of summarizing the research status of self-mixing interferometry,the SMI scheme of low-frequency vibration measurement with a scale of micro-nanometer has been designed using a diode-pumped Nd:YAG microchip laser,the mathematical model of SMI vibration measurement has been established and the numerical simulation has been carried out.The simulation results show the effectiveness of SMI model and the feasibility of the micro-vibration measurement scheme.Secondly,an experimental sensing system of SMI micro-vibration for diode-pumped Nd:YAG microchip laser has been established,and the experiment has been achieved.The experimental results show that the SMI signal with stable performance is obtained.The SMI conditioning circuits have been designed,including current-voltage conversion,signal amplification,filtering and other circuits,and their functions have been tested.The test results show that the design of conditioning circuits are reasonable and they can provide good pre-treatments for the SMI signals.Finally,the SPI serial data acquisition and transmission system and the vibration measurement algorithm of self-mixing interferometry have been designed based on FPGA,and the frequency and amplitude of micro-vibration have been obtained after data processing.Under the existing experimental conditions,the range of frequency measurement is 30?200 Hz,and the range of amplitude measurement is 0?15?m,the relative error of measurement frequency is no more than 0.63%,and the relative error of measurement amplitude is no more than 9.36%.,which achieve the expected experimental objectives.In conclusion,the scheme of SMI micro-vibration measurement using solid-state laser designed in this thesis is feasible.This research is a practical and high-precision micro-vibration measurement system designed with relatively low price,which lays a foundation for further research and application of micro-vibration measurement in the future.