A hybrid bond graph modeling paradigm and its application in diagnosis

Vanderbilt University

From another viewpoint, abrupt faults in process components can be modeled as discontinuities that take system behavior away from its nominal, steady state, operation. To quickly isolate the true faults, well constrained hybrid models avoid the inherent intractability problems in diagnostic analyses by integrating and facilitating the (1) generation of behavioral constraints from physical laws, (2) expression of system dynamics as energy transfer between constituent elements, and (3) modeling of steady state behavior as a special case of dynamic behavior. The analysis of transients is paramount to accurate and precise fault isolation. However, this is a difficult problem which can be further complicated by operator intervention, and intermittent and cascading faults, therefore, quick capture and analysis of transients is the key to successful diagnosis.

This thesis develops a formal hybrid modeling theory based on physical principles, a model verification method, and a physically correct behavior generation algorithm. Next, it describes a methodology for monitoring, prediction, and diagnosis of dynamic systems from transient behavior, based on the developed hybrid bond graph modeling paradigm. Simulation results from diagnosing a high-order, nonlinear, model of a liquid sodium cooling system in a nuclear reactor demonstrates the success of the approach.

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**GAUTAM BISWAS**
Associate Professor of Computer Science

Vanderbilt University, 455 The
Village at Vanderbilt, Box 1679 Station B, Nashville, TN 37235

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6204

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**GEORGE E.
COOK** Professor of Electrical and Computer Engineering

Vanderbilt
University, 401b The Village at Vanderbilt, Box 1826 Station B, Nashville, TN
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**GABOR
KARSAI** Assistant Professor of Electrical and Computer Engineering

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**KENNETH A.
DEBELAK** Associate Professor of Chemical Engineering

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**MICHAEL
GOLDFARB** Assistant Professor of Mechanical Engineering

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**AMIT MISRA**

misra@vuse.vanderbilt.edu