Robust constrained fault-tolerant attitude control for flexible spacecraft

In this paper, robust constrained fault-tolerant attitude controllers are proposed for flexible spacecraft subjected to external disturbance, model uncertainty, input saturation, and actuator faults. Three types of actuator faults of spacecraft, i.e. partial loss of effectiveness, stuck fault, and outage fault, are modeled explicitly. To handle these actuator faults, a significant lemma is proposed and rigorous proof is conducted at length. By introducing two e-modification parameter update laws to online estimate the unknown parameters caused by actuator faults, constrained fault-tolerant attitude controllers of flexible spacecraft are designed to accommodate these faults without the need of any prior information about these faults. The proposed controllers can achieve the disturbance attenuation in the sense of L2 gain. The effectiveness of the proposed algorithms is assessed through numerical simulations.