Robust nonlinear unknown input observer-based fault diagnosis for satellite attitude control system

Robust nonlinear unknown input observer(RNUIO)-based fault diagnosis for satellite attitude control system(ACS) is investigated in this paper. First, the attitude control of nonlinear model with space disturbance torque and model uncertainties is given, and then RNUIO is designed to achieve actuator fault diagnosis, LMI-based sufficient conditions for the existence of RNUIO is derived for design purpose using Lyapunov stability analysis. Systematic observer design problem is solved effectively in terms of MATLAB/LMI toolbox. Finally, application on closed-loop satellite ACS demonstrates the effectiveness of the proposed approach.