Terminal sliding mode control with active disturbance reject for spacecraft trajectory tracking

For the purpose of probe soft landing on small bodies safely, this paper focuses on improving convergence speed, decrease the chattering and process uncertainties and perturbations from the trajectory tracking control system. This paper presents improved Terminal sliding mode control based on active disturbance reject, which changes terminal sliding mode surface to the sliding mode hyper-surface and apply Active Disturbance Reject Controller (ADRC) to estimation and compensation uncertainties and perturbations, respectively, in the case of the asteroid irregular shape and low gravity. The proposed algorithm can fast and accurately track the planned trajectory in the finite time and is robust to parameter uncertainty, feedback state error and external disturbances. Finally simulation experiments are carried out to demonstrate the effectiveness of the proposed control law.