Research Of Star Pattern Recognition Algorithms Based On Star Sensor

Star sensor is one of the most important accurate sensors for spacecraft attitude determination. The technique of attitude determination based on star sensor is so important that the reliable, fast and accurate star pattern recognition is widely investigated. In this dissertation the algorithms on star pattern recognition based on star sensor are presented. The contents mainly consist of the star image simulation and detection, star pattern recognition and spacecraft attitude determination based on star sensor.Firstly, the method of star image simulation and detection is presented to simulate the background of star sky. The star image simulator on the special star table is developed by the analysis of the mathematic model of star image and the parameters of star sensor. On the basis of the analysis of noise characters, the Gaussian denoising method and frame accumulating denoising method is given to finish the pre-processing on the star image with noise. Using the non-supervising cluster algorithm, multiple stars in the star image are fast detected. Moreover, the star centroids are labeled by means of a centroid-threshold algorithm and a weighted squared centroid-threshold algorithm. The simulating results show that the centroid-threshold algorithm is more accurate than the other's.Secondly, the star pattern recognition algorithms are investigated. For the problem of redundancy match and non-match of single star in the Triangle algorithm, an improved triangle algorithm and the correlation algorithm are proposed respectively. The experimental results using multi-frame star images show that the correctly identified ratio of the improved triangle algorithm was more than 95% , and the other was more than 98%. Both algorithms are robust to the changing environment of star sky.Finally, the spacecraft attitude determination based on star sensor is researched. On the basis of the static single-frame attitude determination algorithms, the EKF attitude estimation algorithm is presented by means of star sensor and gyro measurement model. The simulation results show that the EKF algorithm based on star sensor can meet the demand of the attitude determination...