Robust nonlinear attitude tracking control of an underactuated spacecraft under saturation and time-varying uncertainties

Abstract

The three-axis attitude tracking control of an underactuated spacecraft in the large-angle maneuver was investigated in this study. As a major contribution of this paper, a robust controller was developed to achieve the perfect attitude tracking of the underactuated spacecraft with consideration of saturation and uncertainties. Interestingly, due to non-singularity of this design, it could relax the burden of limiting the initial condition of the quaternions. The stability analysis of the developed controller could be guaranteed by Lyapunov method as shown here. Overall, the simulation results indicate that the proposed controller has robustness against saturation, external perturbations, inertia uncertainties, and internal disturbances of actuators. As result, the controller was asymptotically stable under the combination of the soft saturation and the perturbations so that attitude parameters converged to the desired path within the 230 s. In this case, the saturation level was consumed 0.08 N.m. Also, it was still asymptotic stable under the hard saturation whose level is equal to 0.01 Nm, 12.5% of the soft saturation level.