A BRAKING ESTIMATION DEVICE, ANTI-LOCK BRAKE CONTROLLER, AND A BRAKING PRESSURE CONTROLLER

An apparatus for diagnosing a fault in a dynamic system includes a controller which controls the dynamic system through use of a control input signal and vibrates the dynamic system through use of an vibration signal irrelevant to the internal state quantity of the dynamic system; an observer for estimating, on the basis of a response output from the vibration dynamic system, total disturbance which is a sum of an internal disturbance vector stemming from a fault in the dynamic system and a vibration disturbance vector occurring in the dynamic system through vibration; a correlation calculation unit which calculates cross-correlation between the thus-estimated total disturbance and the internal state quantity of the dynamic system and separates a component related to the internal disturbance from the total disturbance; and a diagnostic unit for diagnosing a fault in the dynamic system on the basis of the thus-separated component related to the internal disturbance. Since the dynamic system is vibrated, the response output can be increased even when there exists small external disturbance. As a result, a fault or a variation in air pressure in a tire can be highly accurately diagnosed.