Dual Channels Vibration Measurement System Based On Laser Doppler Interference

With the development of science and technology, demand of high-speed, high precision vibration measurement is more and more required in the field of precision manufacturing,precision testing, military engineering and so on. Laser Doppler interferometry is an effective method that meets the demand. It has the advantages of high precision, fast dynamic response, non-contact measurement, wide measuring range and no additional mass effect. Doppler measurement instruments are mostly single-channel or single-point scanning measurement type, the system can only measure one vibration point at the same time. The Doppler interference measurement system with two points simultaneously measured has important application value in multi-point and multi-dimensional vibration analysis.In this thesis, a dual-channel Doppler interferometric vibration measurement system is proposed. Based on the single-point measurement structure,the dual-channel Doppler interference measurement system is designed for measuring vibration perpendicular to the surface. It has great bandwidth and dynamic characteristics of measurement, and can adapt to different surface vibration of non-contact measurement.The main work of this thesis includes the following aspects:(1) The research background and significance of laser Doppler interferometry are analyzed. The technical research and the application significance of laser Doppler interference vibration measurement of dual channel Doppler vibration measurement are discussed.(2) The basic principles and key techniques of laser Doppler vibration measurement are analyzed. The realization principle and measurement application method of dual channel Doppler vibration measurement are proposed.(3) The optical path structure of the system is optimized and the design of the high precision imaging lens is completed.(4) The processing circuit of the laser Doppler signal is designed to realize the signal conditioning, signal acquisition and processing of the Doppler interference signal.(5) The principle and method of demodulation of Doppler signal are analyzed. The waveform counting method is proposed and the demodulation efficiency and feasibility of the demodulation algorithm under different sampling rate and noise are verified.(6) The vibration measurement experiment of the system was carried out, and the measurement effect of the system on the vibration of micrometer and submicron was tested.The measurement errors of channel 1 and channel 2 are analyzed respectively, and the experimental results are validated by two experiments.(7) The thesis summarizes the research content, and puts forward some suggestions.