Downloaded from https://www.everyspec.com ADS-79D-HDBK There are several benefits of using sensor fusion instead of single sensor limits, including: a) more robust performance; b) extended spatial/temporal coverage since one sensor may contribute information while others are unavailable or lack coverage of the event; and, c) increased confidence because more than one sensor may confirm the same event which increases assurance of its detection. Sensor data may be fused at the raw data level, feature level, or decision level. Direct fusion of raw sensor data requires sensors of the same/similar type, with similar output formats and sampling rates.
Feature level fusion requires the raw data be first processed into features, and then these features are fused into a single combined parameter. Observing changes in the signature of this parameter then identifies faults. Feature level fusion is best applied to the same types of measurement technologies. Decision level fusion processes each sensor to achieve decisions, and then combines the decisions. For the example in Figure M-7, decision level fusion was chosen because this does not limit the fusion process to a specific feature. New features can be added to the system or different features can be used without changing the entire analysis.
This allows the most flexibility when applying this process to condition based systems since, in most cases; different sensors and post-processing methods are used. FIGURE M-7: Vibration data and ODM data fusion model 101 As shown in the matrix in Table M-III, the combined output from the vibration and ODM sensors provides a more comprehensive state of the bearing and suggested maintenance action. Integration of condition indicators, as shown in Figure. M-7, should be practiced, where possible. 101 Dempsey, P. J., G. Kreider, T. Fichter, Tapered Roller Bearing Damage Detection Using Decision Fusion Analysis, NASA Technical Report: NASA/TM – 2006-214380, July 2006. 260 TABLE M-III:
Combine ODM and vibration output Wear Debris Status Vibration Status Low Medium High Low OK OK INSPECT High INSPECT INSPECT REPAIR/REPLACE