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6 June 1997 Health monitoring and damage detection of a rotorcraft planetary geartrain system using piezoelectric sensors
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This paper considers the use of non-intrusive piezoceramic (PZT-5H) strain sensors coupled with wavelet analysis to characterize the vibration signature from a planetary geartrain under simulated fault conditions. This planetary geartrain assembly consists of an electric motor, coupled with a planetary geartrain drive (reduction ratio: 4 to 1) and a belt drive (reduction ratio: 1.67 to 1). The piezoelectric sensors are placed at strategic locations on the geartrain ring gear to measure loads created by the meshing of the sun, planet and ring gears. Strain time histories are obtained at 500 rpm under no-aerodynamic loading. In addition, output rpm and motor temperature are monitored. Each vibration signature is passed into a harmonic wavelet transform algorithm and the mean square wavelet map is computed. This map is used to classify three types of planet gear faults: missing tooth, spalled gear and cracked gear. Results from the application of the harmonic wavelet transform indicate that the different simulated fault cases have unique characteristics which appear in the mean square wavelet map. Visual inspection of the wavelet map provides a wealth of information regarding the frequency of occurrence of the fault under steady rpm and the associated intensity or power changes at various harmonics. When combined in the mean square wavelet map, these two pieces of information allow for better detection and classification of the fault.
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Paul D. Samuel and Darryll J. Pines "Health monitoring and damage detection of a rotorcraft planetary geartrain system using piezoelectric sensors", Proc. SPIE 3041, Smart Structures and Materials 1997: Smart Structures and Integrated Systems, (6 June 1997);

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