Design of Robust Observers for Fault Isolation

Abstract This paper provides a systematic treatment of observer design for the fault detection and isolation (FDI) in linear time-invariant systems. The results of the unknown-input observer obtained recently by the authors are extended to the more general case in which the unknown disturbances are involved also in the system measurement equation. Based on these results the necessary and sufficient conditions for the existence of FDI observers are presented and the design procedure for FDI observers is given. This design procedure is simple and has a clear physical meaning. The most important feature of this method is that the original FDI observer design problem is reduced to an equivalent conventional observer design problem which can be easily dealt with following the well-known Luenberger observer theory. An example is included to illustrate the design procedure. The results presented in this paper can be used directly to the design problem of FDI observers for systems with unknown inputs.