ANTI-LOCK BRAKES - GETTING THE BEST OUT OF THEM

Getting The Best Out Of ABS In Practice

(i) What Happens

Under normal operating conditions, a vehicle equipped with ABS stops by using the conventional braking system. In severe braking conditions, however, the ABS system is automatically activated when any one of the vehicle's wheels approaches a lock condition. The system determines when ABS activation is required through wheel speed sensors and an electronic brake module (EBCM).

The sensors continuously relay information concerning the rotational speed and acceleration of each wheel to the EBCM, which compares these inputs with calibrated values of allowable wheel slip and other pertinent vehicle dynamics information. If and when conditions warrant, the EBCM then signals the ABS system's hydraulic modulator to begin ABS action.

The system modulates pressure to the affected wheel(s) by first isolating the wheel brake from further pressure build-up. This is performed by closing the solenoid bypass valve and energizing an electric motor that closes the displacement cylinder check valve assembly as pressure is released.

(ii) How To Get The Best Out Of The System

Under normal driving conditions, ABS brakes do not operate any differently than conve...