Variable structure with sliding-mode control for landing on asteroids

Due to physical parameters and motion information of target asteroid aren't acquired accurately, landing dynamics equations inevitably include various disturbances, such as un-model acceleration terms. This paper brings forward a landing guidance and control scheme based on variable structure with sliding mode (VSS) to overcome the impact coming from un-model acceleration terms. First, the desired trajectory is planned out under considerations of safe soft landing constrains. Second, according to VSS, the guidance law is designed to achieve tracking of the desired trajectory and succeed in landing on asteroid; Finally, the feasibility of this scheme is validated by computer simulation.