Fixed-time fault-tolerant attitude control for rigid spacecraft with torque saturation

This paper investigates the fixed-time attitude control problem for spacecraft under input saturation, actuator faults, and system uncertainties. Three novel saturated fixed-time nonsingular terminal sliding mode surfaces (NTSMSs) are designed, which can keep the system states fixed-time stable after the establishment of their sliding manifolds. Two of them are time-varying and firstly designed. Each of the two NTSMSs has an adjustment parameter that is adjusted dynamically and used to handle saturation and cancel the attitude dynamics. According to other related predesigned parameters, a conservative lower bound of this parameter is obtained. A saturated control scheme is then designed in conjunction with a newly proposed saturated reaching law. A modification strategy is carried out to facilitate the engineering applications of our methods. The fixed-time stability of the closed-loop systems is validated by Lyapunov stable theory. Simulation results validate the effectiveness and superiority of the proposed control scheme. •Three novel saturated terminal sliding surfaces are firstly designed which keep the states stable.•The lower bound of designed adjustment law can be calculated based on the predesigned parameters.•Our control scheme keeps the states fixed-time stable while rejecting uncertainties, actuator faults, and input saturation.•A modification strategy is developed to promote the application of our methods to engineering.