| 摘要 |
PROBLEM TO BE SOLVED: To detect the pressure of air in a tire by excluding the effect of disturbance from road surfaces and the like. SOLUTION: An electronic control device (ECU) 5 operates the wheel speeds from the detected signals of wheel-speed sensors 2a-2d, performs frequency analysis (FET operation) for the wheel speeds and obtains the signal strength for every frequency. Furthermore, the resonance frequency is obtained within the specified frequency range in order to make the resonance vibration appearing in the vicinity of 40Hz to be the object to be detected. Furthermore, two kinds of weighting processings for the resonance frequency are performed in accordance with whether the speed is located in the wheel-speed band (Vα-Vβ), where the resonance vibration is liable to occur, or not. That is to say, when the wheel speed is located in the wheel speed band of Vα-Vβ, a relatively large weighting amount Jαis used, and the weighting operation is performed. When the wheel speed is not located in the wheel speed band of Vα-Vβ, a relatively small weighting amount Jβis used, and the weighting operation is performed. Thereafter, the ECU 5 computes the average resonance frequency from the resonance frequency of (n) times and operates the pressures of air of the tires 1a-1d from the above described resonance frequency.
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