Abstract: In a method of controlling an anti-skid brake system for a vehicle having one modulator and two wheel speed sensors for each axle, when the vehicle brakes during running, for example, on a split road where surface friction coefficients on the right and left surfaces of the road are greatly different from each other or on a curved road where torque values of the right and left wheels are quite different from each other, in case that one of the right and left wheels which is lower torque is set in a pressure reducing mode while the other wheel which is higher torque of the road is in a normal service braking state, a retaining mode or a slow pressure reducing mode is selected to the braking pressure of the right and left wheels. Therefore, when the conditions of the right and left wheel are quite different from each other as mentioned above, the braking pressure is retained or is intensified slowly so as to secure its braking force and thereby shorten the braking distance of the vehicle.

Abstract: the present invention, a counter value is increased by a predetermined increment when it is judged that front wheel speed is being decelerated and speed difference between front and rear wheels is higher than a setting value, and the counter value is decreased by a predetermined decrement when it is judged that speed difference between front and rear wheels is not higher than the setting value. Next, if it is judged that the counter value is higher than the setting value, a high .mu. flag is set. If it is judged that the counter value is not higher than the setting value, the high .mu. flag is cleared. Thus, it is judged whether road surface has a high .mu. value or not by speed difference between front and rear wheels and by duration, during which the speed difference is maintained. When a high .mu. flag is set, a control value for high .mu. value is set as a control value relating to anti-skid brake control, and if the high .mu. flag is cleared, a control value for low .mu. value is set.

Abstract: In the present invention, an estimated car body speed is obtained on the basis of the highest wheel speed selected from three wheel speeds including the lowest of the wheel speeds of left and right rear wheels and the wheel speeds of left and right front wheels. Because the car body speed is obtained on the basis of wheel speed selected by Select-High of three channels of wheel speeds of the two front wheels and wheel speed by Rear Select-Low, wheel speed of outer rear wheel, which is much higher than the speed of the gravity center of the car body when a car is turning, is excluded, and the estimated car body speed thus obtained is closer to the speed of the gravity center of the car body.

Abstract: When skidding of a wheel is detected at braking of the wheel, a passage changeover valve is changed over to allow a brake fluid within a brake cylinder to escape to a low-pressure accumulator, thereby reducing the pressure within the brake cylinder. In addition, by driving a pump, the brake fluid, which has accumulated in the low-pressure accumulator, is fed under pressure to circulate this brake fluid to a brake fluid passage between the master cylinder and the passage changeover valve. When wheel velocity recovers a predetermined amount, the passage changeover valve is changed over, thereby supplying the brake fluid from the pump to the brake cylinder so as to increase the pressure of the brake cylinder again. When the wheel velocity of the braked wheel has recovered to a predetermined wheel velocity, brake hydraulic pressure is generated a predetermined number of times in pulsed fashion, after which the brake hydraulic pressure is increased again.