Research On Optimization Control And Navigation Method For Detector Soft Landing Asteroid

At present,many countries pay more attention on the asteroid exploration activities,and make a long-term plans about asteroid exploration activities.This paper studied the control and navigation methods which aimed at the problem of detector soft landing.The main research contents of the paper include:Firstly,the paper analyzed the characteristics of asteroids,and got the model of the asteroid's gravitational field by the method of spherical harmonics coefficient.The dynamic model of the detector is established in the landing point coordinates by the transformation matrix between the coordinate systems.According to the boundary conditions of the detector descending trajectory,designed the desired descending trajectory.With the constraint of the actual trajectory of the detector,a error equation based on the position error and velocity error of the detector is established.Secondly,the navigation method based on optical information is studied by analyzing the motion process and navigation process of the detector,and established the navigation observation equation and state equation.Besides,the paper designed an interacting multiple model filter with improved model weight information.The filter co-variance is introduced into the weight information,and realized the motion estimation of the detector.Simulation results show that the interacting multiple model filter is feasible and effective.Finally,the paper designed a double-sliding modes controller based on fast two-power reaching law in the descending process of detector.Designed a compensation controller based on RBF network which aimed at the problem of system unknown interference affecting the detector motion.Then,according to the detector motion characteristics in the landing process,a sliding mode control method that based on fast double-power reaching law is used to realize the vertical soft landing of the detector.The simulation results show that the detector can arrive the desired position according to the preset trajectory,and meet the requirements of the detector safe landing on target asteroids.