Research On High-speed Small And Micro Target Motion Speed Demodulation Technology

Photon Doppler velocity measurement technology is a new type of optical interferometry technology,which calculates the speed information of moving objects through the frequency shift signal generated by the detection light emitted by the surface of the moving object and the reference optical interference,and the signal demodulation algorithm.Photonic Doppler velocimetry technology has the advantages of non-contact measurement,wide velocimetry range,high responsivity,and continuous measurement,and is widely used in explosion and impact dynamics research and other short-term high-speed and micro-moving targets.The development and application background of photon Doppler velocity measurement technology and photon Doppler effect are introduced,and the related principles of photon Doppler velocity measurement system,such as photon Doppler effect,optical heterodyne principle,optical interference velocity measurement technology and photoelectric detector square detection principle.The advantages and disadvantages of fringe method,short time Fourier transform and wavelet transform are analyzed and compared.It is analyzed and pointed out that the principle of fringe method is simple and the accuracy is high,but it is sensitive to highfrequency noise and the universality of the algorithm is poor.The short-time Fourier transform algorithm is easy to implement,but its window length is fixed,the overall time-frequency resolution is fixed,and it can not be compatible with low-frequency and high-frequency signals at the same time.Although the wavelet transform realizes the mechanism of variable window length,it is cumbersome to select the wavelet base and extract the frequency of the spectrum.According to the actual test environment and calculation requirements,in order to extract the velocity information from the noisy weak Doppler signal and complete the adaptive demodulation of batch Doppler signals,it is necessary to select a reasonable data processing scheme.The velocity demodulation method of weak Doppler signal based on livewire algorithm is adopted for weak signal,and a set of automatic processing flow is completed for batch Doppler signal processing.The advantages and disadvantages of the local maximum method were analyzed for the extraction of differential frequency curves.An image processing based extraction method was proposed,which achieved the extraction of frequency curves through five steps: edge extraction operator,noise point removal,breakpoint connection,and curve refinement.This compensated for the low accuracy of the local maximum method in extracting noisy timefrequency maps.PDV test system and metal bridge foil electric explosive device were built.The photon Doppler velocity signal is simulated and the demodulation algorithm is verified.The photon Doppler voltage signal is demodulated to the spectrum by the time-frequency analysis method of short-time Fourier transform,and the local extreme maximum method is used to calculate the velocity of the target object according to the time-frequency curve.On this basis,the signal demodulation program is designed on the python platform by using Python+opencv+Tkinter to complete the Doppler signal demodulation software package and realize the GUI humancomputer interaction interface.The visual interface with simple interface and simple operation is completed.The feasibility and robustness of the design software are verified by the data processing of metal bridge foil detonation flyer.