Robust attitude tracking control of spacecraft under unified actuator dynamics

This paper investigates the attitude tracking control of spacecraft under unified actuator dynamics. The inertia uncertainties, external disturbances, and input saturation are also considered. A novel robust attitude tracking control scheme is proposed by incorporating a disturbance observer and an auxiliary dynamic system into the command filtered backstepping control design. The command filtered backstepping control can avoid the 'explosion of complexity' problem inherently existing in the traditional backstepping control. The disturbance observer is designed to estimate the mismatched compound disturbance induced by inertia uncertainties and external disturbances. The auxiliary dynamic system is conducted to tackle the effect of input saturation. The uniform ultimate boundedness of the overall closed-loop system is rigorously proved. The proposed controller can guarantee the attitude tracking errors converge to the arbitrary small neighbourhood of zero even subject to actuator dynamics. Numerical simulations and comparisons illustrate the effectiveness and advantages of the proposed control scheme.