A quantitative fault detection method for a class of nonlinear systems

This paper proposes an observer-based fault detection method for a class of nonlinear models which have bilinear and quadratic nonlinear terms in their discrete state-space representations. Various other methods proposed in the field are related to this method or are special cases of it. A nonlinear fault detection observer is proposed such that the error dynamics are independent of an unknown disturb ance. A result is proved for the observer error dynamics and a numerical algorithm is given for calculating the observer and residual gain matrices. Sufficient conditions are also stated for fault detectability. An illustrative example is given for the problem of detecting certain faults in a hydraulic system.