Research On Performance Improvement Of Laser Semi-active Positioning System

The semi-active laser positioning system is a system for receiving laser echo scattered by target,calculating target orientation information,and realizing target tracking function.At present,there is a serious decline in signal-to-noise ratio in long range detection,and the problem of severe decrease in angle measurement accuracy caused by low signal-to-noise ratio because it uses the method of directly detecting the energy of laser echo.This paper improves semi-active laser positioning system signal to noise ratio and angle measurement accuracy,realizes the function of the semi-active laser positioning system calculates the target azimuth information correctly in crescent spot case by theoretical analysis and derivation,simulation and experimental research.This paper analyzed the research status at home and abroad of improving SNR of semi-active laser positioning system and improving positioning system accuracy by kalman filtering.At present,the research for improving the performance of the system,progress of study abroad has reported relatively less research at home and abroad mainly focus on the research on improving the accuracy of the research,there have been no reports on the SNR and the crescent spot.Firstly,in view of the serious reduction of SNR in the long range detection of the laser semi-active positioning system,a scheme for directly detecting the semi-active laser positioning system based on polarization detection is proposed,determine the structure parameters of polarization detection by the norm theory,derived the polarization detection of semi-active laser positioning signal and background light system model,gives the azimuth information of target polarization detection mode algorithm.The verification system of polarization detection laser semi-active positioning system is set up,and the signal-to-noise ratio test and target azimuth information resolution test are carried out.The experimental results show that polarization detection can increase the intensity ratio between signal light and background light SBR of the semi-active laser positioning system by about 1.2 times,the experimental results of target azimuth information in polarization detection mode are approximately similar to the theoretical simulation curve.Secondly,in view of the problem that the angular error of the semi-active laser semi-active positioning system increases with the SNR,and the accuracy of the angle measurement is reduced,the factors affecting the angular accuracy of the system and the statistical characteristics of the system are analyzed.Derivation of semi-active laser positioning system in the state space of constant projectile target deviation angle and unsteady projectile target deviation angle of two kinds of working mode of system description,according to the measurement accuracy of approximate normal distribution characteristics to choose kalman filter to improve measuring accuracy of the system.The angular accuracy of two modes of constant bullet point,deviation angle and non-constant projectile angle of deviation is simulated and studied,the simulation results show that the kalman filter can increase the angle measurement accuracy from 0.50 to 0.21 degrees for non-constant bullet point deviation angle and working state.For constant bullet point,deviation angle,working state,kalman filtering can increase angle measurement accuracy from 0.50 to 0.19 degrees.An experimental system for measuring angular accuracy of direct test laser semi-active positioning system is set up,and the kalman filter is used to improve the angular accuracy test of the system.The test results show that for non-constant projectile target deviation angle,kalman filtering accuracy can be improved to 0.50 degrees from 1.24 degrees,for a constant projectile target deviation angle,kalman filtering accuracy can be increased to 0.01 degrees from 0.11 degrees.Finally,according to the direct detection of laser semi-active positioning system at work,there is a crescent spot on a photosensitive surface of the detector because of scattering and projectile barrier.This paper analyzes the formation mechanism of crescent shaped light spot,given the azimuth information of target in this case the solution algorithm.The crescent beam azimuth information of target solution test,test results and simulation results of curve curve approximation with effective system of active positioning laser half field angle by ±2.5 degrees increased to 3.5 degrees,to enhance the detection ability of the system.