Study On Robust Estimation And Guidance For Autonomous Landing On Planets Based On Optical Navigation

Precise planetary landing is a challenging task in deep space exploration. Thelevel of navigation and guidance determines the success of the whole landingmission. However, traditional dead-reckoning based navigation and guidancemode can’t meet the accuracy requirement for future precise planetary landingmission. So it’s necessary to develop the new generation navigation and guidancealgorithm based on optical measurement for autonomous planetary landing.With the supports of the863major program “Simulation and demonstrationsystem of asteroid attachment”, the National Natural Science Foundation ofChina “Research on Autonomous Navigation Theory and Method for Deep SpaceExploration” and the973Program “Research on GNC for Precise Landing onPlanets”, this dissertation deeply and systemically studies the navigation andguidance algorithm for precise landing on planets based on optical measurementfrom the following two aspects: states estimation algorithm and guidance andcontrol strategy. The main contents of this dissertation are as follows.Firstly, researches on relative navigation based on optical measurement androbust estimation method are carried out. Optical measurement aided inertialnavigation algorithm is developed to make up the shortage of optical relativenavigation of planetary landing mission. Furthermore, the H∞-based robustestimation algorithm is presented to deal with the non-Gaussian noise in opticalmeasurement and the initial uncertainties in the integrated navigation system.The LQ game approach is introduced to form the estimation guideline tominimize the worst-case estimation error caused by the disturbance input.Besides that, the coordination of the estimation accuracy and robust performanceis taken into account and the estimation algorithm of planetary landingnavigation is improved.Then, optical navigation based observer trajectory stochastic optimizationmethod is explored. For the adverse effect of estimation error resulting from thelack of observability, the stochastically optimized guidance algorithm is proposed.The estimation performance of navigation system is incorporated into the processof observer trajectory planning, which takes advantage of the nonlinear coupling between observability and trajectory. And the overall performance of thenavigation, guidance and control system for planetary landing is improved byplanning landing trajectory rationally with considering the trade-off betweenefficient control and reliable estimation.Further, rapid planning method with multi constraints for planetary landing isinvestigated. The guidance and control strategy with convex programming is putforward to overcome the defects of the typical polynomial guidance law in theburn-up optimization and task constraints satisfaction. The complex nonlinearprogramming is solved efficiently by casting the nonlinear dynamic pathplanning problem with state and control constraints as a second-order coneprogramming with the performance index of fuel consumption. Besides, thereceding horizon framework is introduced, and the real-time computingarchitecture of the algorithm for planetary landing is constructed.In addition, investigation of robust tracking and control method for planetarylanding is carried out. Considering the influence of uncertainties from gravitymodel and disturbance on tracking the guidance trajectory, the adaptive robusttrajectory tracking algorithm is conducted. The adaptive trajectory trackingcontrol is designed by introducing the online estimation parameters of celestialgravity model. And the design of the robust feedback control is performed basedon bounding arguments on the model uncertainties to ensure that the variation ofthe actual state that deviates from the nominal trajectory does not exceed thedesired sector.Finally, on the basis of the aforementioned research, the system function ofnavigation, guidance and control for planetary landing is deeply analyzed and thesystem architecture of semi-physical simulation platform is constructed withmultiple simulator and the prototype. Furthermore, the on-board autonomousnavigation, guidance and control software system is developed by real-timeoperation system for planetary landing. And the feasibility of the proposedoptical measurement based navigation, guidance and control algorithm isconfirmed by semi-physical simulation and analysis.