Research On Attitude And Position Determination Around Small Body Based On Image Feature

Flying around the small body is quite an important stage in the small body exploration task.Autonomous optical navigation,as one of the key technologies to realize flying around the small body,has numerous advantages such as high navigation accuracy,strong survivability,low cost and so on.In this thesis,aiming at navigation feature recognition,spacecraft pose estimation,autonomous navigation determination and other issues,an autonomous optical navigation method based on image features flying-around small body is researched,considering the characteristics of small body flying-around exploration.The main contents of this paper are as follows:Firstly,the dynamic model and navigation observation model of small body are established and the navigation system scheme in the flying-around phase is designed.Specifically,the orbit and attitude dynamic model of the spacecraft is establish and the observation model of navigation system based on perspective projection is given.Accordingly,an autonomous optical navigation scheme utilizing the characteristics of opportunity region features and craters is designed combining the imaging characteristics of small body surface.Secondly,the relative pose estimation method based on opportunity region feature is studied.According to the characteristics of illuminated and shaded changes in the surface of small body,an opportunity region feature based on the region of interest and the transition region of illuminated and shaded in the image is defined.Then,the description and search criteria of opportunity region feature are achieved.Afterwards,the improved iterative closest points’ algorithm is adopted to match the opportunity region feature in the adjacent sequence images.Thus,the relative pose of the spacecraft could be estimated employing the normalized eight-point algorithm.Next,the absolute navigation method based on crater characteristics is studied,combining the imaging characteristics of craters on the surface of small body.Then,the twodimensional maximum entropy image threshold segmentation algorithm is employed to segment the illuminated and shaded areas of craters,which is combined with watershed algorithm to complete the marking and detection of the potential crater area.Further,by imaging and analyzing of the virtual control points,the fast absolute pose estimation of the spacecraft could be realized by pose from orthography and scaling with iterations algorithm.Finally,a semi-physical simulation system is built for the autonomous optical navigation around the small body,and the simulation experiments are carried out.The simulation experiment analysis of the opportunity region features are executed and the performance of the crater features detection method is completed through the simulation and imaging of the topographical features of the small body.