The TRANSCEND system for fault detection and isolation in continuous systems uses qualitative reasoning methods to analyze transients caused by abrupt faults. Qualitative transient analysis avoids some of the computational difficulties associated with numerical schemes, but they lack discriminating power. This paper presents the formal basis for qualitative transient analysis, and then establishes the limits of the discriminatory power of this methodology. An integrated scheme that starts with qualitative fault isolation to narrow down possible fault hypotheses, and then uses a focused quantitative parameter estimation scheme to identify the true fault is developed. This approach provides a number of advantages over purely quantitative FDI schemes.

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Copyright 2000 IFAC.