| Star sensor is a kind of attitude measuring instrument based on the observation of stars,and it has been widely used in space missions for its high precision and reliability.Limited by the development of hardware systems and software algorithms,the dynamic performance of domestic star sensors are relatively low,and they are generally used when carriers fly smoothly.With the rapid development of domestic aerospace technology,many highly dynamic carriers such as agile satellites and ranged weapons require for the star sensors with higher dynamic performance.Therefore,highly dynamic star sensor has been one of the most important parts in domestic aerospace industry.After analyzing the key technologies of highly dynamic star sensor,we focus on the research of star centroid methods,star identification methods,star tracking methods and imaging system of highly dynamic star sensor,and the main work can be summarized as:(1)Under highly dynamic condition,trailing of star pixels happens,which makes the accuracy of star centroid reduce,hence restoration methods of blurred star image are researched and a restoration method for blurred star image based on region filter is proposed.The kinematic model of star centroid in blurred star image is firstly established,based on which the motion trail of star centroid and the star blurred region are determined.Then morphological filter and improved Richardson Lucy algorithm are respectively used to preprocess and restore the star image in blurred region,which solves the problems that the RL algorithm is susceptible to noise,inefficient and does not have termination condition.Hence,the restoration effect of blurred star image is improved and the restoration process is accelerated.As a result,the accuracy of star centroid is improved in real time.(2)Under highly dynamic condition,redundant and false matching of star identification occur because of the existing centroid errors,hence star identification methods based on subgraph isomorphism are researched,then a fast identification algorithm based on multi-feature matching is proposed based on the classic triangle algorithm.Firstly,by using partitioned star catalog and blocked navigation feature library,the searching range of navigation feature library reduces,hence the identification speed is improved.Besides,by using multi-feature matching,the probability of redundant and false matching reduces,hence the identification rate is improved.As a result,the problems that triangle algorithm has low identification rate and slow identification speed under highly dynamic condition are solved.(3)Under highly dynamic condition,star locations in adjacent star images are greatly changing and the success rate and efficiency of star tracking reduces,hence highly dynamic star tracking methods based on attitude estimation are researched,then an attitude tracking algorithm based on SVD-UKF algorithm and an attitude tracking algorithm based on SCKF algorithm are proposed respectively.The highly dynamic star sensor is modeled as a nonlinear stochastic system,based on which UKF(Unscented Kalman Filter)algorithm and SVD(Singular Value Decomposition)method are combined to improve the robustness of UKF algorithm during highly dynamic star tracking.Besides,SCKF(Square-root Cubature Kalman Filter)algorithm is applied to the star tracking of highly dynamic star sensor,which improves the problem that the tracking accuracy of SVD-UKF algorithm in the modeled high-dimensional nonlinear system is limited.Finally,a fast tracking identification method is proposed based on the partitioned star catalog,which improves the problem that the identification of new stars with traditional star identification methods is slow during highly dynamic star tracking.(4)By comprehensively analyzing the main technical parameters of highly dynamic star sensor,a design scheme of imaging system is proposed.By using an optical lens with large field of view and an image sensor with high quantum efficiency,sufficient available stars for highly dynamic star sensor is ensured.Therefore,the integration time of star sensor can be shortened and the trailing length of star pixels reduces.Besides,according to the proposed scheme,electronic system of the highly dynamic star sensor is designed and a prototype is developed.Finally,ground testing experiment is carried out to verify the dynamic performance of highly dynamic star sensor. |
