Fault diagnosis and construction of a class of nonlinear systems with unmodeled dynamics

This paper presents a fault detection and construction scheme for a class of Lipschitz nonlinear systems with unmodeled dynamics and disturbance. A sliding mode observer is developed, and the design results are formulated in Linear Matrix Inequalities (LMIs). The fault considered here can be unbounded as long as its qth derivative is bounded. Unlike the classical fault construction method based on the property of sliding surface, the fault alarm rate is reduced by minimizing the unmodeled dynamics and disturbance effects on the construction error. An example is given to illustrate the effectiveness of this fault construction approach.