Adaptive removal of resonance-induced noise

This invention relates to removing noise from the digitized output of a sensor, the sensor being subject to undesired (although perhaps necessary) internal or external resonance. It further relates to such removal when the resonant frequency is unknown or drifts. Noise is removed from the digitized...

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Bibliographic Details
Main Authors White, Stanley A, Woodard, Jeffrey P, Soderstrand, Michael Alan, Nelson, Karl Einar, Nguyen Dao, Phong Vu
Format Patent
LanguageEnglish
Published 26.08.2003
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Summary:This invention relates to removing noise from the digitized output of a sensor, the sensor being subject to undesired (although perhaps necessary) internal or external resonance. It further relates to such removal when the resonant frequency is unknown or drifts. Noise is removed from the digitized output of a sensor, subject to undesired resonance, even when the resonant frequency is unknown or drifts, with sufficiently low phase delay for the sensor to be used in closed-loop control. A very narrow notch filter which removes the resonance-induced noise is recursive (IIR) and therefore has a low phase delay. However, the apparatus which determines the center frequency of the notch filter is non-recursive, and therefore stable. It includes a tunable FIR filter which tracks the same resonance that we wish the IIR filter to remove. Tuning the FIR filter to minimize the output of the FIR filter therefore tunes the notch frequency to align with the resonant frequency. The tuning parameter which adaptively produces this result is suitably scaled and biased, and is applied to the IIR filter.