Research On Autonomous Optical Navigation And Safety Assessment Method For Small Body Landing

Small body landing detection is an important part of deep space exploration.In order to achieve the accurate landing in the complex area of small body,the lander needs the capability of autonomous navigation and safety assessment.In this paper,considering the characteristics of small body landing detection,this paper studies the methods of autonomous optical navigation and landing safety assessment for weak gravitational field modeling,descending pose estimation and landing safety assessment,and build the visual simulation of small body landing.The main contents are as follows:Firstly,consider the dynamics model of small body.Aiming at the characteristics of irregular small body's gravitation,research on the weak gravitational modeling method,and establish the high-precision gravitational model of small bodies by using polyhedron method.On this basis,analyze the influence of percussion force under weak gravitational condition.and establish the dynamics model of small body landing.Secondly,research on the autonomous landing navigation method based on optical /IMU.The observation model of the optical camera and the measurement model of the inertia unit are established.The position of the landing position of the lander is determined by the multi-line line information measurement.Analyze the error source of the navigation system.by comparing the optical navigation and the inertial navigation,and consider the characteristics of the small body landing navigation,design an integrated navigation filter based on extended Kalman filter.Then,the landing safety assessment method based on the collision probability is researched.Considering the characteristics of the landing point distribution and the topographic features of the small body,the collision probability is introduced into the landline safety assessment index,establishe the collision probability density function model of the landing error ellipse,the collision probability between the lander and the obstacle is deduced.and analyze the impact of drop error,obstacle distribution on the probability of collision,Using the collision probability value to carry out safety assessment of small objects landing.Finally,build a small body landing visual simulation system,and the autonomous optical navigation and safety assessment methods are simulated and analyzed by the visual simulation system.Three-dimensional model of small body model and landing plane was established by using software 3ds Max by model modification,texture mapping and light simulation.Based on the visualization model and the Open GL environment,the small body landing visual simulation system was established.Based on the system,the visual simulation of autonomous optical navigation and landing safety assessment is worked out.