| 摘要 |
The invention is directed to an arrangement for controlling a braking force applied to each of front and rear road wheels of a four-wheel drive vehicle depending upon a braking condition, with a hydraulic braking pressure supplied to each of the wheel brake cylinders through an actuator. The actuator is controlled by a braking force controller into which output signals of wheel speed sensors are fed. On the basis of the wheel speeds detected by the sensors, a wheel acceleration of each road wheel is calculated. Also, an oscillation of a relative movement between the front and rear road wheels is determined. And, a coefficient of friction of a road is estimated in accordance with the wheel acceleration and the oscillation. For example, it is estimated that the road is of a relatively low coefficient of friction, when a mean wheel acceleration of all road wheels becomes less than a predetermined standard acceleration, and when the oscillation is caused to exceed a predetermined level. Then, the hydraulic braking pressure applied to each of the wheel brake cylinders is controlled by the braking force controller in accordance with the estimated coefficient of friction and in response to each wheel speed.
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