Probabilistic Performance Analysis of Fault Diagnosis Schemes
Probabilistic Performance Analysis of Fault Diagnosis Schemes
Probabilistic Performance Analysis of Fault Diagnosis Schemes
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3 <strong>Probabilistic</strong> <strong>Performance</strong> <strong>Analysis</strong> 24<br />
3.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24<br />
3.2 Problem Formulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24<br />
3.3 Quantifying Accuracy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26<br />
3.3.1 <strong>Fault</strong> Detection and Hypothesis Testing . . . . . . . . . . . . . . . . . . . 26<br />
3.3.2 <strong>Probabilistic</strong> <strong>Analysis</strong> . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26<br />
3.3.3 Aggregate Measures <strong>of</strong> <strong>Performance</strong> . . . . . . . . . . . . . . . . . . . . . . 29<br />
3.4 Characterizing the Range <strong>of</strong> Achievable <strong>Performance</strong> . . . . . . . . . . . . . . . 30<br />
3.4.1 Randomized Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30<br />
3.4.2 Receiver Operating Characteristic . . . . . . . . . . . . . . . . . . . . . . . 33<br />
3.5 Certifying and Visualizing <strong>Performance</strong> . . . . . . . . . . . . . . . . . . . . . . . . 35<br />
3.5.1 Bounds on <strong>Performance</strong> Metrics . . . . . . . . . . . . . . . . . . . . . . . . 35<br />
3.5.2 Bound on Bayesian Risk . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38<br />
3.6 Extension to <strong>Fault</strong> Isolation and Identification . . . . . . . . . . . . . . . . . . . 40<br />
3.6.1 Quantifying Accuracy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40<br />
3.6.2 Bayesian Risk . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42<br />
3.6.3 ROC Curves for Multiple Hypotheses . . . . . . . . . . . . . . . . . . . . . 43<br />
4 Computational Framework 44<br />
4.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44<br />
4.2 <strong>Fault</strong> Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45<br />
4.2.1 Limiting Complexity with Structured Markov Chains . . . . . . . . . . . 47<br />
4.2.2 Special Case: <strong>Fault</strong> Model Based on Component Failures . . . . . . . . . 55<br />
4.3 System Dynamics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56<br />
4.3.1 Assumptions Regarding the System Dynamics . . . . . . . . . . . . . . . 57<br />
4.3.2 Computing the Conditional Mean and Variance . . . . . . . . . . . . . . 59<br />
4.3.3 Special Case: Models with Only Additive <strong>Fault</strong>s . . . . . . . . . . . . . . . 60<br />
4.4 Decision Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61<br />
4.4.1 Threshold Decision Functions . . . . . . . . . . . . . . . . . . . . . . . . . 61<br />
4.4.2 Dynamic Decision Functions . . . . . . . . . . . . . . . . . . . . . . . . . . 62<br />
4.5 Algorithms for Computing <strong>Performance</strong> . . . . . . . . . . . . . . . . . . . . . . . 68<br />
4.5.1 Sufficiently Structured Systems . . . . . . . . . . . . . . . . . . . . . . . . . 68<br />
4.5.2 LTV Special Case Based on Component Failures . . . . . . . . . . . . . . 70<br />
4.5.3 LTI Special Case Based on Component Failures . . . . . . . . . . . . . . . 74<br />
4.6 Comments on Continuous-Time Models . . . . . . . . . . . . . . . . . . . . . . . 76<br />
5 Worst-Case <strong>Performance</strong> <strong>Analysis</strong> 77<br />
5.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77<br />
5.1.1 Notation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77<br />
5.1.2 Types <strong>of</strong> Uncertainty Considered . . . . . . . . . . . . . . . . . . . . . . . 78<br />
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