Fault-Tolerant Attitude Control of Flexible Spacecraft Based on High-Order Fully-Actuated System Approach and Extended State Observer

This paper investigates the fault-tolerant attitude control problem of flexible spacecraft subject to actuator faults, external disturbances, and unmeasured flexible modes. By employing variable elimination, a high-order fully-actuated (HOFA) model is derived to describe the complex rigid-flexible coupling dynamics. An extended state observer (ESO) is designed to reconstruct the unmeasured system states and compensate for the generalized disturbance, which incorporates coupling effects, external disturbances, and actuator faults. Within the HOFA framework, a fault-tolerant controller is developed to establish a linear closed-loop structure while actively compensating for disturbances using the ESO. Rigorous theoretical analysis guarantees that the proposed control scheme effectively accommodates actuator faults while ensuring the stability of the closed-loop system. Finally, a numerical simulation is carried out to demonstrate the effectiveness of the proposed control scheme.