Finite-time control for soft landing on an asteroid based on line-of-sight angle

Motivated by the requirement for safe and pinpoint soft landing in future asteroids missions, a soft landing control method based on finite-time control (FTC) technique is developed in this paper. Firstly, in order to utilize the design philosophy of cascaded system, the landing error dynamics of asteroid probe are divided into two subsystems, including a position error subsystem (PES) and a line-of-sight angle error subsystem (LOSAES). Secondly, homogeneous system theory is employed to design the control law for LOSAES such that the states of LOSAES will be stabilized to the origin in finite time. For the reduced PES subsystem, a FTC law is designed such that the rest of states will converge to zero in finite time. Strict analysis shows that the whole system satisfies the finite time stability. Simulation results demonstrate that the proposed method provides faster convergence rates and better disturbance rejection properties compared with the traditional asymptotically stable control (ASC) method.