Modified model-based fault-tolerant time-varying attitude tracking control of uncertain flexible satellites

Abstract

A novel, modified model-based fault-tolerant attitude tracking control scheme is derived for the uncertain flexible satellites with four reaction wheels. The stability conditions of this type of satellite are also analyzed. The attitude tracking error dynamics is employed to derive the novel control scheme, which is formulated in the presence of actuator fault uncertainties, moment-of-inertia uncertainties, flexible appendage dynamics uncertainties, space environmental disturbances, and reaction wheel dynamics. The uncertainties are estimated to update the computed torque, which extremely enhances the pointing accuracy and reduces the conservativeness. The large-angle attitude tracking and time-varying attitude trajectory can be stabilized by the novel controller, which solves the constant desired trajectory restriction in most of other control schemes. Numerical results are presented to verify the advantages of the proposed control scheme in comparison with proportional–derivative controller, model-based controller, time delay controller, and modified time delay controller.