How does an anti-lock braking system (ABS) function?

@clifford.walsh 

An anti-lock braking system (ABS) functions by continuously monitoring the speed of each wheel during braking. Here are the steps involved in the operation of an ABS:

1. Monitoring: The ABS sensors are mounted on each wheel, or sometimes on the axle. These sensors monitor the rotational speed of the wheels.
2. Comparison: The ABS control module compares the speed of each wheel with the others. It expects all the wheels to have similar rotational speeds.
3. Deceleration: When the brakes are applied, the wheels slow down due to friction. The ABS module detects if any wheel is decelerating at a faster rate than the others. This indicates that the wheel is about to lock up or skid.
4. Intervention: If the ABS module detects an impending wheel lock-up, it intervenes by modulating the hydraulic pressure to the brakes. This is done through a hydraulic control unit (HCU) that operates solenoid valves to regulate brake fluid flow.
5. Pulses: The ABS system rapidly applies and releases the brake pressure on the specific wheel that is about to lock up. This results in pulsating braking pressure, which helps maintain the rotational speed of the wheel and prevents it from skidding.
6. Release: Once the ABS module senses that the wheel has regained its traction, it releases the brake pressure to allow the wheel to spin freely again.
7. Continuous monitoring: The ABS continues to monitor the wheel speed and conditions throughout the braking process. It adjusts the brake pressure accordingly to prevent wheel lock-up while maximizing braking efficiency.

By preventing wheel lock-up, ABS ensures that the driver retains steering control of the vehicle during braking. It helps reduce stopping distances and provides improved stability and maneuverability, particularly on slippery or uneven road surfaces.

@clifford.walsh 

ABS works in conjunction with the traditional braking system and does not replace it. It is an additional safety feature that enhances the performance of the brakes and helps prevent wheel lock-up during emergency braking situations.