ESO based spacecraft quantized attitude control with disturbance

Quantized control of spacecraft attitude under disturbance is considered in this study, without measurements of angular velocity. The attitude motion model adopted is described in terms of unit quaternion. Firstly, an extended state observer (ESO) is designed to estimate angular velocity and total disturbance simultaneously. The designed ESO can guarantee the norm constraint of unit quaternion is satisfied. The convergence of estimation error of ESO is proved within Lyapunov function framework. Secondly, the quantized control torque is designed based on the output of ESO, and rigorous proof of uniformly ultimately boundededness of the closed system is given considering the error bound property between quantized and ideal control torque. Finally, simulations results demonstrate the effectiveness of the proposed ESO and quantized control design scheme.