基于相似三角形的星图识别

Star identification algorithm based on similar triangle principle

星图识别算法是星敏感器快速获得姿态信息的关键,传统的星图识别算法,例如三角形算法、多边形算法以及一些改进算法,大多是以星对间的角距作为识别特征,而星对角距的计算精度严重依赖于星敏感器相机的焦距f的校准精度。如果校准精度不够或者由于环境原因导致相机焦距有较大变化时,这些基于星对角距的识别方法将无法正常工作,本文提出了一种基于相似三角形的星图识别算法,该算法利用观测星组成的三角形与CCD相机所成像点三角形相似来进行识别,由于识别过程不需要焦距信息,在焦距有较大变化时仍能正常工作。最后用蒙特卡罗方法进行了仿真验证,结果表明该算法在引入较大焦距误差时识别率无明显变化,其平均识别率为95.2%,平均识别时间为5.3 ms,而相同仿真实验条件下传统三角形算法的平均识别时间为7.6 ms,在引入0.5 pixel的像面位置误差时该算法识别率为93.3%,而传统三角形算法识别率仅为86.5%,该算法较传统三角形算法在识别速度方面有一定优势,同时对像面位置噪声的鲁棒性更好。

The star identification algorithm is a key technology for star sensors.Traditional star identification algorithms,such as triangle algorithm,polygon algorithm,and other improved algorithms mainly consider the star diagonal distance as an identification feature.The accuracy of the calculated star diagonal distance is dependent on the calibration accuracy of the focus length of the charge-coupled device(CCD)camera.These identification algorithms cannot work properly if the calibration accuracy is insufficient or if the focus length of the camera changes significantly owing to environmental conditions.This paper proposed a new star identification algorithm based on the similar triangle,which operated using the similar triangles between the observed triangle and the triangle consisting of image points of the CCD camera.Because the identification process was not dependent on the focus length,it still had a large focus error.Finally,simulation verification was carried out with the Monte Carlo method.The results show that the recognition rate of the proposed algorithm remains unchanged,with large focus length error.The proposed algorithm has an average recognition rate of 95.2%while the recognition speed can reach 5.3 ms.In contrast,the average recognition speed of the traditional triangle algorithm is approximately 7.6 ms under the same experimental conditions.The proposed algorithm and traditional triangle algorithm has a recognition rate of 93.3%and 86.5%,respectively,when the image position error is 0.5 pixels.Compared with the traditional triangle algorithm,the proposed algorithm has higher speed and improved robustness.