A Fully-actuated System Approach for Spacecraft Attitude Control with Input Saturation

This paper investigates the attitude control problem for a rigid spacecraft subject to external disturbances and actuator saturation. A novel control scheme is technically proposed by incorporating the Nussbaum gain technique and extended state observer into the fully-actuated system theory. First, a fully-actuated system model for the attitude error dynamics is established. Then, the Nussbaum gain technique is employed to tackle the time-varying input gains arising from input saturation, and an extended state observer is introduced to estimate and compensate system uncertainties and external disturbances. The stability of the closed-loop system and the convergence of state errors are accordingly proven via Lyapunov stability approaches. Finally, a numerical simulation is carried out to validate the effectiveness of the proposed scheme.