Research On Vision Based Terrain Relative Navigation For Small Celestial Body Exploration In The Descending Stage

Small celestial bodies exploration is a hot issue in deep space exploration activities.After decades of development,countries around the world have successively carried out a variety of small celestial bodies exploration activities,including flying,circling,impact,landing and sampling return,and achieved the predetermined scientific research objectives.The exploration of small celestial bodies plays a key role in the verification and development of advanced space technology,and is of great scientific significance to the exploration of the birth of celestial bodies and the origin of life.In the exploration activities of small celestial bodies,navigation technology determines whether the probe can land on demand successfully and therefore whether the subsequent scientific research missions can be carried out successfully.The traditional inertial navigation method has a large error and error accumulation problem,so it is difficult to apply to the complex small celestial body exploration activities.However,the introduction of relative navigation method based on visual technology makes it possible for the detector to navigate autonomously.At present,the navigation technology commonly used in small celestial bodies exploration missions generally combines the traditional inertial navigation method and the terrain relative navigation method based on visual technology.It has the advantages of high precision and fast speed,and can effectively assist the detector to complete the landing task.First of all,the navigation problem in small celestial bodies exploration mission is studied,and the relative terrain navigation method suitable for detector descent stage in small celestial bodies exploration mission is proposed.According to the basic principle of the rear intersection of single image space,the error equation including the navigation camera's internal and external azimuth elements,image point coordinates and object square coordinates is established,and the conditional adjustment method with parameters is used to solve the parameters accurately.Compared with the existing navigation algorithms,this algorithm not only takes into account the errors caused by azimuth elements in the camera,but also USES the adjustment method to adjust the object square data in the parameter calculation process.The method can reduce the interference to navigation accuracy caused by the parameter error in camera and the noise in object data.Secondly,a navigation data simulation platform is created for the simulation generation of navigation data in the descending stage of small celestial bodies exploration task.Using the data generated by the platform,the navigation algorithm is verified,the influence of the distribution of feature points and their number on navigation accuracy,the error scale and convergence of each parameter are analyzed,and the running time of the algorithm is counted.Finally,the navigation algorithm is tested and analyzed by using the terrain data of small celestial bodies.Experimental results show that the proposed navigation algorithm can control the error of navigation parameters within an acceptable range,and the algorithm is capable of navigation.