Research And Application Of Velocity Measurement System Based On Laser Doppler Effect

High-precision speed measurement technology plays an important role in many fields.With high precision,quick response and other advantages,laser Doppler velocimetry can be used to measure speed in industrial,aviation and other fields.And the accuracy of speed is significant to the length and acceleration measurement.This paper has designed an improved laser Doppler velocimetry system to measure the velocity and length of moving objects accurately.Compared to the traditional laser Doppler system,this system contains two adjustable mirrors to focus the beams,so that the position of the measurement point is adjustable,and the data processing is real-time.Firstly,this paper described the basic principles of laser Doppler velocimetry and commonly used measurement modes.It analyzed the advantages and disadvantages of various measurement modes.In this part of the paper,the double beam and double scattering measurement mode is mainly introduced and a specific speed expression is given.Secondly,for the defect of the traditional measurement structure,this paper designed an improved optical system which contains two adjustable plane mirrors.By adjusting the two mirrors,the measurement point position will be changed and the moving objects can be placed at different distances.As for the photoelectric detection circuit,an APD is used as the receiver to receive the Doppler signal.The laser Doppler signal will be send to the computer after A/D conversion and the digital signal is processed continuously on the LABVIEW platform.Finally,the function of the designed system is tested by a series of experiments,including the verification experiment of the photoelectric detection circuit,the velocity calibration experiment of the moving objects,laser Doppler velocimetry experiment and laser Doppler length measurement experiment.In this part of the paper,the measurement result has been compared with the calibration value and the factors affecting the accuracy of measurement results are analyzed,and the relative error of the length measurement results is less than 1%.