Flexible Performance Attitude Fault-Tolerant Control Based on Disturbance Observer

This paper addresses spacecraft attitude control with actuator faults, proposing a fault-tolerant scheme using flexible performance. A second-order disturbance observer is designed via the Euler-Lagrange model for time-varying faults, with simplified structure and adjustable parameters to enhance bandwidth flexibility. Flexible performance functions and dual-layer saturation limiters are integrated to mitigate actuator saturation, enabling adaptive performance regulation under saturated or unsaturated condition. The developed controller prevents performance boundary violations during saturation while ensuring stability via Lyapunov analysis.