Robust tracking of guidance trajectory for probe pinpoint soft landing on small bodies

To pinpoint land on the surface of irregular small bodies safely, an effective guidance and control algorithm based on dynamic surface was presented. The relative orbit dynamic models of the probe in landing site coordinate were obtained through the coordinate conversion, and irregular gravitation of the rotating small body was presented as polyhedral models. The open-loop fuel sub-optimal polynomials were adopted for the nominal guidance trajectory. From the point of view of realtime performance, the dynamic surface control was adopted for tracking the nominal trajectory. The designed robust tracking guidance laws for the uncertain nonlinear system with external disturbances are simpler than the existing algorithms based on the traditional backstepping method. The close-loop system is proved to be stability. The performance and effectiveness of the proposed synthesized closed-loop nonlinear guidance system are verified by numerical simulation results.