Research on Timing Compensation of Shadow Photograph System with Three-sequence Laser Sparking

Abstract

The accuracy of the laser sparking time interval measurement plays a key role in the measurement results when the projectile velocity is measured by shadow photograph system with three-sequence laser sparking. By comparing with the original single-chip measurement results, it was found that there was a certain deviation in the measurement results of the laser sparking time. Then the principle of the laser sparking time measurement circuit is introduced in detail, and the reasons for this error phenomenon are summarized. And analyze the original laser sparking time measurement data column and the data column accurately measured with an oscilloscope, use the Pearson correlation coefficient to describe the correlation between the two data columns, and obtain the sample correlation coefficient, the first laser sparking interval coefficient r1=0.50, the second laser sparking interval coefficient r2=0.52. According to the three-level division rule, when 0.4≤|r|<0.7, the two variables are significantly correlated. In order to compensate the original data, it is necessary to find a suitable Δ value to minimize the residual sum of squares of the measured column data after compensation. The mathematical model is developed and solved for the nonlinear system of equations, and the optimal value of Δ for the original data is obtained using a global search for the optimal value: Δ1= 0.238μs, Δ2= 0.201μs. Comparing the compensated data with the original data, The standard deviation of the measured columns of the first flash interval decreased from 0.117μs to 0.022μs after compensation, and the second decreased from 0.102μs to 0.014μs. This shows that the two columns error of compensated data are significantly reduced, which is important for the improvement of the velocity measurement accuracy of the target channel.