Device and method for estimating physical quantity and device and method for ABS control

摘要

A wheel velocity signal for each wheel detected by a wheel velocity sensor is input to a bandpass filter. Signals from frequency bands unrelated to the unsprung resonance are then removed from the wheel velocity signal and only signals from frequency bands related to the unsprung resonance are output. A road surface mu gradient estimation device uses an online identification method to identify an damping ratio of a second order resonance model similar to a suspension-tire resonance model from the signal output from the bandpass filter. The road surface mu gradient is then estimated from the identified damping ratio. The damping ratio of the second order resonance model corresponds to the road surface mu gradient in the following manner: when the damping ratio is identified as being small, the road surface mu gradient is estimated as being large; and when the road surface mu gradient is identified as being large, the damping ratio is estimated as being small.