Research On Laser Doppler Hypervelocity Collision Velocity Measurement Technology

Hypervelocity Impact refers to a type of collision phenomenon in which the impact pressure generated by the collision is much greater than the yield strength of the material,that is,p/Y>10.The speed of the colliding objects can usually reach several kilometers per second.Its velocity measurement is of great significance in many fields such as basic discipline research and national defense weapons and equipment development.At present,the equipment used for ultra-high-speed collision velocity measurement usually adopts Photonic Doppler Velocimetry(PDV)velocity measurement technology.PDV speed measurement technology is essentially a laser interferometric speed measurement technology.However,in the process of measuring high-speed moving objects,the Doppler frequency shift caused by the object is too large,often dozens of GHz,and the bandwidth of the general oscilloscope cannot meet the test requirements.Aiming at the above problems,this paper proposes a speed measurement method that can reduce the bandwidth requirements of the oscilloscope-light beat Doppler speed measurement.The light beat signal generated by modulation is used to replace the traditional light source for Doppler speed measurement.This paper mainly focuses on the light-beating Doppler velocimetry technology.First,the principle of light-beating and light-beating Doppler velocimetry is introduced.order of magnitude,so that the reason for the upper limit of velocity measurement can be greatly improved for theoretical derivation;secondly,based on the characteristic that the injection current of the semiconductor laser affects the center wavelength,by introducing the MZI interference optical path,the continuous wave frequency-modulated semiconductor laser is used to generate the optical beat signal for velocity measurement.The influence of swept frequency nonlinearity of semiconductor laser on velocity measurement accuracy is analyzed,and an open-loop correction scheme based on iterative algorithm of chord secant method is proposed.;Then,the ultra-high-speed collision velocity measurement system is introduced in detail,the specific implementation scheme of nonlinear correction of semiconductor laser based on FPGA is proposed,and the minimum system of FPGA and the corresponding peripheral circuit are designed;A velocity demodulation algorithm based on signal extension frequency and digital correlation phase and frequency discrimination is presented,and the algorithm is simulated.The simulation shows that the scheme in this paper can effectively obtain the velocity curve of moving objects,and the maximum velocity is 20 d B under the condition of20 d B signal-to-noise ratio.The demodulation error is less than 2.98%,the higher the signal-to-noise ratio,the higher the demodulation accuracy.Finally,the nonlinear module of the semiconductor laser and the experimental device of the ultra-high-speed collision velocity measurement system are built respectively.The experimental results show that the iterative correction method based on the chord secant method can significantly improve the nonlinearity of the current-tuned semiconductor laser;the velocity measurement system can effectively obtain moving objects.The speed history of which the maximum speed measurement error is within 4%.