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Case study methodology for information fusion interface definition

An overall Prognostics and Health Management System (PHM) implementation has the fundamental function of integrating information from multiple system elements and fusing this information into useful knowledge about system and vehicle health. Effectively developing this function requires a structured approach to ensure that data level fusion, feature level fusion, and information level fusion are performed in a coherent architecture. This paper describes a methodology for examining the interfaces between aircraft system/subsystem elements of a PHM function. Case study scenario development is used as the basis for this methodology. Likely failure/damage/wear modes of the equipment are tracked from the observable symptom level through multiple levels of fusion to the top layer of the fusion architecture. There are multiple advantages of this structured approach: identification of interface requirements; clarification of information flows; identification of the individual functional elements of the architecture; and confirmation of the effectiveness of a given architecture. This methodology is applicable to all of the levels of the PHM information hierarchy. Case studies range from propulsion and vehicle system conditions that require immediate pilot notification as well as maintenance notification, to those that are analyzed over longer periods of time for estimating remaining life. Using a wide range of conditions allows examination of interfaces and modeling and cross-correlation techniques that support all levels of the information fusion hierarchy. A summary of the outcome and issues identified during the review of case studies of the vehicle, propulsion and air vehicle PHM systems is presented.