Robust design of fault isolation observers

The robust diagnostics design has gained more attentions recently in real a pplications. It is known that the freedom in eigenstructure assignment lead s to the well-conditioned design which is robust to unstructured uncertaint ies (Shen et al., 1995, 1998). Moreover, the unknown input fault detection observer (UIFDO) decouples the known inputs, the structured uncertainties, from the diagnostic residuals. In this paper, we present an unknown input f ault isolation observer (UIFIO) based on the UIFDO by using the eigenstruct ure assignment. It achieves robust fault isolation subject to both structur ed and unstructured uncertainties. Moreover, the optimal gain matrix of the present diagnostic observer is obtained to improve its robustness without degrading diagnostic performance. Experimental results of an automotive eng ine show the validity and applicability of the proposed robust UIFIO design . (C) 1998 Elsevier Science Ltd. All rights reserved.