Variable structure attitude control of staring mode spacecraft with disturbance observer

Attitude control problem of staring mode spacecraft in Low Earth Orbits (LEO) is studied in this paper. The staring mode of LEO spacecraft and its merits for observation are initially presented, and then the dynamic equation and kinematic equation are obtained on the basis of deriving the expected attitude quaternion and angular velocities. In order to improve the observation precision and prolong the observation time, a variable structure controller and a disturbance observer are proposed to reduce inherent chattering. Simulation results show that the controller has quick response and good robustness to the inertia parameters uncertainty and the external disturbance, and the chattering of variable structure control is effectively weakened.