Robust Saturated Finite Time Output Feedback Attitude Stabilization for Rigid Spacecraft

This paper investigates the velocity-free feedback control problem associated with finite time attitude stabilization of a rigid spacecraft subject to external disturbance and input saturation. First of all, to address the lack of angular velocity measurement, a novel, fast, finite time convergent observer is proposed to recover the unknown angular velocity information in a finite time under external disturbance. Then, a finite time output feedback controller is proposed using the designed finite time observer, in which the control input saturation nonlinearity is explicitly considered in the proposed finite time stabilizer. Rigorous proofs show that the proposed observer can achieve finite time stability, the controller rigorously enforces actuator-magnitude constraints, and the attitude of the rigid spacecraft will converge to the equilibrium in a finite time. Numerical simulations illustrate the spacecraft performance obtained using the proposed controllers.