Study On Autonomous Navigation And Soft Landing Control Methods Of Asteroid Lander

This paper is to undertake National Key Basic Research Program "973" project: "Irregular low gravitational field detector motion behavior analysis and landing control".Navigation, guidance and control as the most basic and the core of a distant space exploration technology, can affect the overall function of the spacecraft and decide the detection task can be successfully completed. Asteroid soft landing technology is a hot and difficult point in recent years.The spacecraft safely reaches asteroid surface in soft land on asteroid way. The methods of navigation and control are studied.The main research contents of this paper include:First of all, to analyze dynamics action in the process of landing spacecraft, consider to the asteroid in a weak gravitational field around irregular gravity and stars spin,established orbital dynamics model based on Newton motion law and mathematics principle of relative differential principle.Secondly, for the spacecraft navigation requirements, and the characteristics of system nonlinear, the proposed optical navigation information to assist the inertial measurement unit integrated navigation, inertial measurement and visual measurement model is established, to target landing site as reference established autonomous navigation filter model, proposed cubature kalman filter based on strong tracking filtering, projections where the spacecraft position and attitude. Finally simulation studies are presented to show the probe can land safely, and also show the effective of the proposed method.Finally, the control strategy of soft landing task is studied. In order to reduce fuel consumption, planning guidance trajectory. The guidance method is selected based on the theory of the fuel sub-optimal. Considering strong disturbance and the nonlinear characteristics of the system and problems of chattering, slow convergence speed of trajectory tracking in conventional control method, proposed hyper-surfaces of terminal sliding mode control based on double power reaching law. To achieve external disturbances and internal model uncertainty estimation of compensation, this paper define a compound disturbance and design a kind of nonlinear disturbance observer. Finally simulation studies are presented to new control law achieves to fast tracking desired trajectory, and avoids large amplitude oscillation, so spacecraft landed smoothly.