Research On Cross-correlation Infrared Velocity Measurement System Based On ARM

Infrared velocity measurement system plays an important role in projectile velocity measurement.High precision time-testing method is the main research direction at present.And there will be warhead wave in some high-velocity projectile,the precision of measuring time will be greatly reduced by the interference of warhead wave.In order to solve the problems,this paper proposes an infrared real-time velocity measurement system based on cross-correlation algorithm.Through the study of traditional cross-correlation algorithm and generalized cross-correlation algorithm,the MATLAB simulation model of cross-correlation measurement is established.By the simulation analysis of pulse-counting method with fixed threshold,traditional cross correlation and generalized cross correlation to measure time,cross correlation algorithm has higher accuracy in measuring time,and cross correlation has smooth effect on signal noise,which can reduce the influence of noise and other interference on measuring time.Fast Fourier Transform FFT to complete the cross-correlation measurement can greatly reduce the amount of computing,which is suitable for the application of the real-time measurement system.The time-testing system is combined with the CPLD hardware timing module and the cross correlation algorithm.The length of AD acquisition time and the length of discrete signal sequence involved in cross correlation are based on CPLD timing results.The method of quadratic search peak value and the method of three-point interpolated fitting function are used to determine the transit time.The former can reduce the number of search peaks and improve the operation speed.And the latter is helpful to improve the precision of time measurement.AD acquisition module based on ARM chip is designed to meet the system requirements through multiple data acquisition,AD conversion precision,save development time and cost,and use the processor with floating point arithmetic to have shorter operation time.At last,the feasibility of the system is verified by the comparison experiment.The system has high accuracy in the speed-measuring range and meets the requirements of various indexes.