A comparison of sliding mode and unknown input observers for fault reconstruction

This paper compares the use of a recently proposed sliding mode fault detection and isolation scheme with a linear scheme based on an unknown input observer. Both methods seek to reconstruct actuator and sensor fault signals,for a class of uncertain systems. Although the explicit details of the two approaches are quite different, an underlying link between them is exposed and investigated. The methods are compared using a nonlinear model of a crane system in which known faults are deliberately introduced.