Output Feedback-Based Refined Fault-Tolerant Control for Drag-Free Satellites with Disturbance

In this paper, an output feedback-based refined fault-Tolerant control strategy for drag-free satellites is investigated to counteract actuator fault and disturbance. The coupling of disturbance and fault in the same channel will affect the reliability of fault diagnosis and the control precision of drag-free satellites. Therefore, an observer-based method is designed to realize the fault diagnosis by the separation estimation of disturbance and fault, even though the relative velocity information is not measurable. More specifically, according to the modellable characteristics of disturbance and the non-modellable characteristics of actuator fault, a reduced-order state observer (ROSO) is designed to estimate the disturbance and the relative velocity information, and an extended state observer (ESO) is designed to estimate the actuator fault. Then, by incorporating a sliding mode controller, a composite control law is proposed to enhance the anti-disturbance and fault-Tolerant capability of satellites. Finally, numerical simulations are performed to demonstrate the effectiveness of the proposed strategy.