Brake Regulation
In order to prevent the wheels from locking during braking, yet provide the optimum braking force for maximum braking efficiency, the ABS braking system must:
- Have the ability to monitor the wheel rotation rates
- Be able to regulate the braking forces applied to the wheels.
The ABS system carries out these functions with an electronic control system. The components of the ABS system include:
- The electronic control module
- The wheel speed sensors
- The brake hydraulic unit
- The brake master cylinder
The four wheel speed sensors are used as inputs to the control module. The module uses these signals to determine wheel speed, wheel acceleration and deceleration. ABS controlled braking starts when the module detects that one or more wheels are about to lock.
Once activated, the ABS control module pulses the brakes on the affected wheel rapidly (2-15 times a second). This allows the vehicle to be slowed down while still maintaining steerability and directional stability.
The ABS pulses the brakes through solenoids mounted in the hydraulic unit. The solenoids regulate the pressure to the affected wheel through three phases of control:
- Pressure Hold
- Pressure Drop
- Pressure Build