Patent ID: 8207839

Claim:
An apparatus for detecting a tire having a decreased pressure based on resonance frequency of tires attached to respective wheels of a vehicle, comprising: a storage means for storing information regarding a distribution of resonance frequencies respectively corresponding to a plurality of air pressure statuses, the distribution being learned in advance; an initialization means for estimating, based on rotation speed information or rotation acceleration information regarding the tires at a normal internal pressure, a frequency characteristic of the rotation speed information or the rotation acceleration information; a frequency estimation means for estimating, based on running rotation speed information or rotation acceleration information regarding the tires in a running vehicle, a frequency characteristic of the rotation speed information or the rotation acceleration information; and a Bayesian estimation means for subjecting a tire pressure status at a certain time to a Bayesian estimation based on the resonance frequency during the initialization, a resonance frequency at the certain time obtained from the frequency estimation means, and distribution-related information stored in the storage means.