To estimate physical quantity for expressing the ease of slide of a wheel with a small amount of operation.
The estimating device on wheel in use is provided with a wheel speed detection means 10 for detecting a wheel speed signal, an amplitude operation means 12 for calculating the amplitude of the wheel speed signal corresponding to a plurality of different frequencies based on the wheel speed signal corresponding to the plurality of different frequencies out of the wheel speed signals being detected by the wheel speed detection means 10, an amplitude ratio operation means 14 for calculating the ratio between two amplitudes out of a plurality of amplitudes being calculated by the amplitude operation means 12, and a road surface μ judgment means 16 for judging physical quantity for indicating the ease of use of a wheel and for judging the inclination of the road surface μ in the form of the embodiment based on the ratio of the two amplitudes being calculated by the amplitude ratio operation means 14.
ASANO KATSUHIRO
ONO HIDEKAZU
SUGAI MASARU
NAKAGAWA TOSHIAKI
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