Fixed-time attitude control for rigid spacecraft with external disturbances

In this paper, a finite-time control method based on fixed-time is developed for attitude stabilization of a rigid spacecraft with external disturbances. In comparison with the existing finite-time techniques based on terminal sliding mode, of which the initial value of system states must be known when estimating the settling time, the proposed fixed-time based sliding mode controller can not only stabilize the attitude faster, but also eliminate the need of the knowledge of the initial condition to estimate the time of the reaching and the sliding phase. Moreover, if the initial condition is known, the expression of a more accurate settling time is also given in this paper. Finally, the attitude stabilizing performance of the controller is evaluated through a numerical example and the results show that the closed-loop system is robust to external disturbances and initial conditions.