Research On Guidance And Control Algorithm For Softlanding Of Deep Space Probe

In deep-space exploration missions, landing on the surface of a celestial bodysoftly and sampling by the instruments onboard is an important way of gatheringscientific data. In recent years, with some new scientific found in astronomy, such asthe discovering of the possible existence of ice on the north pole of the moon by theClementine probe, more and more deep-space missions require the ability of precisionor pin-point landing on the probe for an detail exploration of the area with highscientific interest. This thesis is mainly focus on the problem of the guidance andcontrol algorithm of pin-point soft landing for the deep-space probe, the main work is asthe following:In the base of the analysis on the lunar and mars soft landing procedure, theconstraints on the soft-landing trajectory optimization is presented according to therequirement of the next generation of landing navigation and hazard detective sensors toachieve a precision landing. The problem of the conventional dynamic model fornon-pin-point landing is presented, then two different three-dimensional dynamicmodels were developed in the inertial and surface fixed coordinates, and the concept oftrajectory rendezvous is introduced to simplify the nonlinear dynamic model.A pin-point soft-landing trajectory optimization problem is modeled based on theoptimal control theory, the optimal thrust vector direction and thrust level switchingequation were presented based on the Pontryagin maximum principle, and theinexistence of singular interval of the thrust level was proved. Based on the convexoptimization theory, the trajectory optimization problem is transformed into a convexoptimization problem by a set of convex transformation. By discretization, the problemwas transformed into a finite dimensional parameter optimization problem, which canbe solved efficiently by interior-point method, and the relative simulation result ondifferent scenarios is presented.A model tracking controller was designed for the tracking of nominal optimaltrajectory based on the model tracking control theory of linear system. The feedbackgain matrix was presented by closed-loop poles and free vector parameters through amethod based on the structure of the eigen matrix, then the gain matrix was solved andrelative test simulation was conducted.A six degree of freedom dynamic model was established to analysis the effect ofattitude motion on trajectory control, and an attitude tracking control algorithm based onLyapunov principle was introduced, and the stability of attitude control system wasproved. In the end, a closed-loop simulation system was developed in the Matlab Simulink environment, which includes these sub-models: trajectory optimization,trajectory tracking, attitude tracking and6DOF dynamic model, and the whole system’sbehavior simulation result was presented and analyzed.