Principle Of Operation

The ABS components are combined with a hydraulic booster and a tandem master cylinder to provide a two circuit braking system. The system consists of; four wheel speed sensors, a brake control modulator, and an ABS warning lamp.

Should a wheel start to lock up during braking, a signal transmitted from the wheel speed sensor to the brake control modulator will start the hydraulic pump. The brake control modulator will close the input valve of the line connected to the locked-up wheel to stop any increase in fluid pressure to the brake caliper. If this fails to prevent the wheel locking, the pressure in the caliper will be decreased by opening the return valve until the wheel starts accelerating again. The fluid pressure from the return valve is directed into the low pressure accumulator, housed in the modulator body.

From the low pressure accumulator, fluid is pumped through the damping chamber to the brake master cylinder. The pressure to the brake caliper will then be increased in small steps to maintain maximum adhesion between the tire and the road surface. This is achieved by closing the return valve, and opening the inlet valve for short periods to increase the pressure.

Although the system senses all four wheels independently, the rear wheels are regulated as a pair. If a sensor on a rear wheel detects a wheel decelerating rapidly, the fluid pressure to both rear wheels is reduced. The fluid pressure is then dictated by the wheel having the least adhesion to the road surface.

The system will adopt a fail-safe mode if a fault is detected, and a warning light on the instrument panel will notify the driver. The brake system will still operate conventionally, with the same level of performance as a vehicle not equipped with ABS.