| The star sensor is a type of high-precision measuring device which calculates the carrier attitude of the star sensor by taking the fixed stars in the celestial sphere as references.Because the in-flight calibration of the star sensor is difficult to implement and the cost is very expensive,it is very important to perform the testing and calibration on the star sensor in the laboratory;and moreover,the simulation level of the star map of the dynamic star simulator affects the performance and index of the star sensor when the star sensor is subjected to the effective testing and calibration on the ground.The requirements of the star sensor flight mission for the star sensor are high precision,high angular speed and high accelerated speed,so that the star map display of the dynamic star simulator is required to have high precision and high refresh rate characteristics.However,the simulation precision of the star point positions of the dynamic star simulator is affected by the existing star map display devices,so that the ground calibration precision of the star sensor is unable to reach the ideal value.Moreover,the high refresh rate of the star map is affected by the star catalogue search algorithm,so that the current refresh rate of the digital star map is difficult to meet the testing and calibration requirements of the star sensor with the high angular speed.Aiming at the problem that the simulation precision of the star point positions of the star map is affected by the finite resolution of the existing display devices,the paper adopts a sub-pixel display technology,that is,the pixel array based on the two-dimensional Gaussian distribution uses the energy center position of the pixel array to display the star points instead of the existing single-pixel star point display,and thus the simulation precision of the actual star point positions of the dynamic star simulator is improved.By analyzing the relationship between the Gaussian radius and the centroid positioning error of the star points under the certain background noise,the optimal value of the Gaussian radius of the star point pixel array is obtained.Through verification and analysis,the star point display precision adopting the sub-pixel display technology is better than 0.1 pixel under certain background noise,and the requirement that the single-star position error of the simulated star map is better than 10 seconds is ensured.Aiming at the problem of the low refresh rate of the star map of the dynamic star simulator,the paper proposes a new algorithm for searching navigation stars by partition,and the new algorithm optimizes the index mechanism of the sub partition so as to improve the refresh rate of the star map.The celestial sphere is subdivided by the new algorithm and is divided into tens of thousands of rectangular pyramids with the center as the vertex,and the navigation stars in the field of view of the star sensor are directly extracted from the bottom surfaces of the corresponding rectangular pyramids based on the attitude information.Experimental results show that there is no phenomena of star loss and few stars in the star map by using the algorithm,the refresh rate of the star map reaches 110 Hz and is nearly doubled compared with the refresh rate by using the traditional algorithm,and especially when the star data is large,the refresh rate of the star map is improved more obviously.Finally,the testing method of the star map of the dynamic star simulator is studied,the testing system of the star point positions of the star map is designed,camera lens is placed at the exit pupil of the optical collimated system of the dynamic star simulator,the simulated star points are imaged on the CMOS photosensitive surface located at the focal plane,the star point information is collected by the CMOS imaging control system,the detection of the star point positions is completed by the computer data processing and the star point extraction algorithm,and finally,the closed-loop detection of the star map display system is realized. |
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