A model based Vehicle Health Monitoring system for the Space Shuttle Main Engine (original) (raw)

A Vehicle Health Monitoring (VHM) system is designed to detect and isolate failures in the engines of Reusable Launch Vehicles (RLV). This VHM system takes into account engine failures in both sensors and valves, as well as internal components such as turbopumps, injectors, and the combustion chamber. The algorithm of the VHM system is model based. Specifically, using information from a thermodynamic model of the engine together with sensor measurements, a Kalman filter (KF) is designed to predict sensor outputs. The residual, or the difference between the predicted and actual measurement, is used by several statistical tests to detect the presence of a failure, and to categorize the failure as a sensor/valve failure or an internal component failure. Sensor and valve failures are then isolated using the Generalized Likelihood Ratio Test (GLRT). Internal component failures, on the other hand, are isolated using the Multiple Model (MM) method. The proposed methodology can be used for online Failure Detection and Isolation (FDI) as well as for postflight analysis. At the engine design stage, it can help determine the detectability and distinguishability of failures given a candidate sensor configuration. The FDI algorithms are applied to a simulation of the Space Shuttle Main Engine (SSME) to demonstrate their performance. 1 Work supported by Charles Stark Draper Laboratory.