Research On Navigation And Guidance Method During The Period Of Approaching The Small Celestial Based On Optical Measurement

Small body detection has gained more and more attention in recent years,it has become a hot field of deep space exploration.Due to the irregular shape of the small body and the inhomogeneity of the mass distribution,the flying environment of the detectors changes rapidly,what's more the small bodies are far away from the Earth and there is serious problem of the information delay.It is difficult to maintain or maneuver in orbit operation,such as orbit maintenance,maneuvering,transfer and attitude,so that the key technologies in the process of detection have been put forward with higher requirements such as strong autonomy,high precision and so on.In this paper,the near-field autonomous navigation guidance scheme is studied based on the proximity of the small body and the dynamical modeling of the detector and the observability analysis of the autonomous navigation scheme based on the modeling of the gravitational field around the small body.First of all,the relevant reference coordinate system and the dynamic modeling of the detector and small body is introduced.Inertial coordinate system,B-plane coordinate system and non-rolling line-angle coordinate system are introduced.The kinetic model of the detector and the small object is established,and the dynamic model of the two is established in the inertial coordinate system.The relative kinematic model is given.The emphasis and difficulty of modeling is the establishment of the gravitational field around the small body,so the gravitational field modeling method is studied deeply.Secondly,the modeling method of gravitational field of small object is studied.The existing gravitational field model mainly includes the spherical harmonic function method and the polyhedral model method,in which the spherical harmonic function method has the analytical form and the algorithm is simple,but the gravitational field divergence in the Brillouin sphere.The polyhedral model method is globally convergent.However,this method has a large computational cost which affects the on-orbit computation efficiency of the detector.In order to obtain a gravitational field model with good real-time performance,high precision and low computational complexity,a modeling method for the fast approximation of small celestial body gravitational field is given in this chapter,and the precision and calculation of this method are discussed.Thirdly,the observability of small-celestial bodies approaching only the angle-only autonomous navigation system is studied.Because of the inherent flaw of unobservable radial distance,the observable performance of the navigation system is influenced by the observable performance of the navigation system.It is found that the navigation performance can be improved by appropriate maneuvering.By changing the navigation observation path to improve the navigation performance of the solution,at the expense of a certain fuel consumption in the case of reduced navigation error to improve the overall system performance.Finally,the design of the guidance scheme for the detector in the proximity of the small celestial bodies is proposed.In order to improve the performance of navigation,a new approach is proposed to optimize the approach trajectory by using observability as one of the constraints.And the guidance accuracy of the guidance strategy is compared with the proportional guidance,the improvement of navigation performance by the guidance strategy is analyzed.