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Method and apparatus for detecting air pressure in a tire using a basic wavelet function localized in time

  • US 6,109,099 A
  • Filed: 12/22/1998
  • Issued: 08/29/2000
  • Est. Priority Date: 12/22/1997
  • Status: Expired due to Fees
First Claim
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1. A method for detecting an air pressure of a tire comprising the steps of:

  • outputting an oscillating electric signal including a vibration frequency component of a tire of a vehicle;

    performing wavelet transformation of the oscillating electric signal at three or more predetermined frequencies by a basic wavelet function localized in time and expanded or contracted by a scale parameter, in accordance with a shift parameter indicating a time position;

    calculating wavelet coefficients through the wavelet transformation;

    calculating a mean value of the wavelet coefficients at every predetermined interval of time;

    obtaining an approximate curve of the second or greater order by a method of least squares using the mean values of the wavelet coefficients at the respective predetermined frequencies at every predetermined interval of time;

    extracting a constant of the approximate curve; and

    estimating the air pressure of the tire based on the constant.

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