| Photonic Doppler Velocimetry(PDV)is the measurement of the velocity of a moving object by detecting the Doppler shift caused by reflected light on the surface of the object.PDV system,featured by the wide velocity measurement range,high measurement accuracy and fast response,has been widely applied to the detection of shock wave and detonation wave,R&D of new materials and energetic materials,etc.With the increase in PDV application objects,new problems emerge continuously.Taking the cylinder wall surface motion driven by explosive detonation as the measuring object,the probe and data processing methods of PDV system are studied and improved according to the characteristics of its tilting surface motion and low signal-to-noise ratio of measured data,specifically as follows:1.In view of the fact that the common grin lens probe can only detect the reflected light of objects in rectilinear motion,a new optical probe combining grin lens and plano-concave cylindrical lens was designed,which could be used to detect the reflected light of objects in tilting motion.The simulation and experimental results show that the improved optical probe has better light collection efficiency than the common grin lens probe.2.The principles,advantages and disadvantages of various data processing methods were analyzed,and the autocorrelation function of PDV signal was derived.In addition,the influence of sampling frequency,measuring speed,signal-to-noise ratio,moving average filtering and autocorrelation filtering on velocity measurement accuracy was studied.The conclusion is drawn that the measurement accuracy of autocorrelation filtering is much higher than that of moving average filtering.3.The beat signals of cylinder wall surface motion is processed,and its velocity curve is obtained.It's indicated that the maximum relative standard deviation of velocity measurement caused by sampling frequency is 1.29-2.90%,and 2-10% and0.1-1% respectively by moving average filtering and autocorrelation filtering. |
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