A Hierarchical Model-based approach to Systems Health Management

Integrated Systems Health Management (ISHM) provides the ability to maintain system health and performance over the life of a system. For safety-critical systems, ISHM must maintain safe operations while increasing availability by preserving functionality and minimizing downtime. This paper discusses a model-based approach to ISHM that combines fault detection, isolation and identification, fault-adaptive control, and prognosis into a common framework. At the core of this framework are a set of component oriented physical system models. By incorporating physics of failure models into component models the dynamic behavior of a failing or degrading system can be derived by simulation. Current state information predicts future behavior and performance of the system to guide decision making on system operation and maintenance. We demonstrate our approach on the fluid loop of a secondary sodium cooling loop of a nuclear reactor system. We model the fluid loop at the system level and a generic pump system at the component level. Monitoring and diagnosis at the system level may point to faults and degradation in components, e.g., the pump. A more detailed analysis of the pump using structural and material models may point to physics of failure models that explain degradation in the pump components. This information can form the basis for prognostic analysis that forms the core methodology for monitoring system performance and decision making for maintenance.