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ISSN: 0148-7191, e-ISSN: 2688-3627
Published June 15, 2015 by SAE International in United States
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Random vibration control systems produce a PSD plot by averaging FFTs. Modern controllers can set the Degrees of Freedom (DOF), which is a measure of the amount of averaging to use to estimate the PSD. The PSD is a way to present a random signal-which by nature “bounces” about the mean, at times making high excursions from the mean-in a format that makes it easy to determine the validity of a test. This process takes time as many frames of data are collected in order to generate the PSD estimate, and a test can appear to be out of tolerance until the controller has enough data to estimate the PSD with a sufficient level of confidence. Something is awry with a PSD estimate that achieves total in-tolerance immediately after starting or during level changes, and this can create dangerous over or under test conditions within specific frequency bands and should be avoided. This paper intends to treat some of the inherent properties of the PSD and some faulty PSD estimation methods that attempt to circumvent these inherent properties.
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CitationVan Baren, J., "Random Averaging," SAE Technical Paper 2015-01-2213, 2015, https://doi.org/10.4271/2015-01-2213.
- Van Baren , Philip Statistical Properties of the Random PSD Vibration Research Corporation Technical Paper http://www.vibrationresearch.com/public_pdf/StatisticalPropertiesOfRandomPSD.pdf
- Van Baren , John Is Your Random Vibration Testing Fulfilling MIL-STD-1540D? Vibration Research Corporation Technical Paper http://www.vibrationresearch.com/public_pdf/Fulfilling_MIL-STD-1540D-Tolerance_on_Vibration_Controllers.pdf
- Lang , George and Van Baren , Phil Does Your Random Controller Square With Chi? Vibration Research Corporation Technical Paper http://www.vibrationresearch.com/public_pdf/SquaringWithChi.pdf