Active Fractional-Order Sliding Mode Control of Flexible Spacecraft Under Actuators Saturation

Abstract In this article, a novel multi-purpose modified fractional-order nonsingular terminal sliding mode (MFONTSM) controller is designed for the flexible spacecraft attitude control and appendages passive vibration suppression, assuming the control torque saturation in the system dynamics. Furthermore, an active FONTSM controller is proposed separately to perform active vibration suppression of the flexible appendages using piezoelectric actuators. The fixed-time stability of the closed-loop system for both the passive and active controllers is analyzed and proved using the Lyapunov theorem. Finally, the performance of the proposed controllers has been tested in the presence of uncertainties, external disturbances, and the absence of the damping matrix in order to study the effectiveness of the proposed method.