Adaptive Integral Fault-Tolerant Sliding Mode Control of a Flexible Spacecraft Based on Disturbance Observer

This article investigates the enhancement of the control performance of flexible spacecraft by addressing actuator faults, input saturations, and internal and external disturbances (including flexible solar panel vibrations) during attitude maneuvers. First, the proposed disturbance observer, which can estimate the angular velocity and lumped disturbances of the system, is developed. Hereinafter, a fault-tolerant control algorithm is proposed using an integral sliding mode with adaptive gain to accurately estimate the upper bound of actuator faults with input saturation considering the rigid-flexible body interaction effects. On the other hand, fault-tolerant control, which proposes adaptive gain in the structure of the sliding surface, has the potential to eliminate the undesirable phenomenon of chatter in the system. The global stability of the nonlinear system is proven using Lyapunov theory. Additionally, during the attitude maneuver, active vibration control, also referred to as strain rate feedback control, using piezoelectric sensor/actuator patches is simultaneously implemented to reduce residual vibrations caused by rigid-flexible body dynamic interactions and the effect of actuator faults. The simulations in the form of a comparative study with conventional approaches show the validity and capability of the proposed approach in reducing the effect of external and internal disturbances for flexible spacecraft with actuator faults.