Reseach On Autonomous Navigation Technology Of Small Celestial Body Detection Landing Segment

As a popular direction of space exploration activities,the detection of small celestial bodies is of great significance for exploring the origin of life,promoting social development and maintaining the safety of the earth.Among them,the soft landing of the detector on the surface of the small celestial body is an important part of the small celestial body detection mission,and the autonomous navigation technology is an important guarantee for the soft landing of the small celestial body detector.Based on the research background of the small celestial body detection mission landing segment,this paper studies the autonomous navigation technology of the small celestial body detection landing segment,aiming at the establishment of the system model,the design of the autonomous navigation scheme,and the estimation of the state of the detector.The main work of this paper is as follows:（1）The commonly used navigation coordinate systems in the small celestial body detection landing segment are defined,and the conversion relationship between the navigation coordinate systems is deduced.Aiming at the irregularity of the gravitational field of small celestial bodies,the spherical harmonic function method is used to construct the gravitational field model of small celestial bodies.By analyzing the force of the probe,the dynamic model of the probe in the landing section is established,and on this basis,the kinematic model of the probe is constructed.（2）Aiming at the problem that the small celestial body landing mission requires high navigation accuracy,the autonomous navigation scheme of the detector is studied.The inertial navigation scheme and optical navigation scheme of the detector in the landing section are designed,and the attitude and position information of the detector in the navigation scheme is solved.On this basis,with the help of information fusion technology,an optical/inertial integrated navigation scheme based on information fusion is designed.This scheme can not only solve the problem of error accumulation over time in the inertial navigation scheme,but also has higher navigation accuracy than the optical navigation scheme.（3）Aiming at the nonlinear problem of the navigation system,the nonlinear navigation filtering algorithm is studied,and an improved unscented Kalman filtering algorithm is proposed.The algorithm has higher estimation accuracy than the traditional filtering algorithm.Using the improved unscented Kalman filter algorithm,a combined optical/inertial navigation scheme based on the improved unscented Kalman filter is designed.Compared with the previous navigation scheme,this scheme has higher navigation accuracy and can meet the navigation accuracy requirements of small celestial body soft landing missions.