Research Of The Attitude And Trajectory Control Method Of The Asteroid Probe In The Weak Gravitational Field

Deep space detection technology is one of the development national key projects. The paper is on the basis of domestic and international numerous studies, to control the trajectory in the stage of decline and the attitude in the stage of landing of the probe in weak gravitational field.First of all, analysis the orbit dynamic model and the attitude kinematics and dynamics model. According to the characteristics of irregular shape of the asteroids that the paper studied, compared to the other asteroids the gravitational field is not strong and so on, applying the spherical harmonic coefficient method, the asteroid’s gravitational field is established. Considering the influence of the model uncertainty and the interference such as the solar photovoltaic, according to the moving behavior analysis of the probe, establishes the probe orbit dynamics model in the fixed coordinates. In the attitude modeling, treats as weak gravitational field, uncertainty and so on as the interference, establishes the probe attitude kinematics model and dynamics model with Euler angles and Rodriguez parameters method respectively.Secondly, for the trajectory control of the probe soft landing on asteroids with weak gravitational field, this paper presents an adaptive fuzzy sliding mode control scheme. According to the nominal trajectory designed by cubic polynomial method, considering the uncertainty of the probe orbit dynamics model in small body fixed coordinate system, the controller for the dynamic model of probe is established based on the combination of the integral sliding mode algorithm and adaptive fuzzy logic system. Meanwhile, a robust term is introduced to compensate the fuzzy approximate error. This scheme ensures the rapidity and accuracy of the nominal trajectory tracking, as well as enhances the robustness of the controller, improves the dynamic tracking performance on the probe soft landing on asteroids. At last, simulation results present the feasibility and effectiveness of the controller.Finally, in order to realize the control of the probe landing attitude, make the probe to achieve a soft landing, this paper designs a strategy based on the active disturbance rejection control (ADRC) method. The paper adopts tracking differentiator to arrange the transition process of ADRC, to obtain the differential instructions. On the basis of the extended state observer, to estimate the parameters uncertainty and the internal and external interference spacecraft attitude, achieve the closed-loop control. A nonlinear feedback control law is designed to suppress the error of the extended state observer. Contrast the traditional PD controller and ADRC, verify the ADRC relative to the superiority of PD control by the simulation.