Dynamic Surface Robust Guidance and Control for Landing on Asteroids

With a comprehensive application of the theory of the disturbance observer based (DOB) control and dynamic surface control, this paper develops a dynamic surface robust guidance method for precise landing on asteroids. A reference trajectory is first generated by using the spacecraft initial conditions and the terminal landing constraints. We consider the gravitational field modeling errors of the asteroid, parameter perturbations of the spacecraft, and external disturbances as a lumped disturbance of the dynamic system and then design a reference trajectory tracking controller using the DOB technique and dynamic surface control theory. We analyze the asymptotic convergence problem of the estimation of the lumped disturbance. We also present the stability analysis of the closed-loop reference trajectory tracking control system and develop a method to determine the controller parameters. Numerical simulation results show that the DOB designed in this paper can estimate the lumped disturbance effectively and that the closed-loop reference trajectory tracking control system has a fine stability and control precision.