Reduced-Order Observer-Based Robust Fault Estimation for a Class of Uncertain Nonlinear Systems

This study focuses on a challenging issue of reduced-order observer-based fault estimation for a class of nonlinear continuous-time systems with both unknown inputs and model uncertainties. By introducing a nonsingular coordinate transformation, a new nonlinear reduced-order fault estimation observer (RFEO) is proposed, which not only expands the application range of existing fault estimation observers, but also to achieve the accurate estimation of both states and faults. Simulation results of an aircraft application are presented to validate the effectiveness of the proposed methods.