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Question

Difficulty: EasyBraking Systems and ABS

Arrange the stages in order to show how an anti-lock braking system (ABS) operates during emergency braking, from initial driver action to the vehicle coming to a stop.

  1. 1The driver applies firm, continuous pressure to the footbrake pedal.
  2. 2Wheel speed sensors detect that one or more wheels are about to lock up.
  3. 3The electronic control unit rapidly modulates hydraulic brake pressure.
  4. 4The wheels continue to rotate, allowing the driver to maintain steering control.

Answer

1. The driver applies firm, continuous pressure to the footbrake pedal. 2. Wheel speed sensors detect that one or more wheels are about to lock up. 3. The electronic control unit rapidly modulates hydraulic brake pressure. 4. The wheels continue to rotate, allowing the driver to maintain steering control.
During emergency braking, the driver applies firm, continuous pressure to the brake pedal. When wheel speed sensors detect that wheels are about to lock up, the electronic control unit rapidly modulates hydraulic brake pressure. This prevents the tyres from locking and skidding, allowing the wheels to continue turning so that steering control is maintained throughout the stop.

Step-by-Step Solution

1
Identify the initial driver action in an emergency braking scenario.
The driver presses the footbrake pedal firmly and continuously without releasing.
ABS requires sustained brake pedal application from the driver to function effectively.
2
Identify how the system recognizes a loss of traction.
Wheel sensors monitor rotational speed and detect when a wheel decelerates rapidly towards lock-up.
Sensor feedback is required to trigger automated pressure regulation before a full skid begins.
3
Identify the automated mechanical response of the ABS.
Valves in the ABS unit rapidly release and re-apply hydraulic fluid pressure to the brake calipers.
Modulating pressure multiple times per second keeps tyre grip near the threshold of maximum friction.
4
Identify the resulting safety benefit for vehicle handling.
The vehicle decelerates while the turning wheels preserve lateral grip for steering.
Locked wheels cannot steer; maintaining wheel rotation ensures the driver can navigate around hazards.

Key Concept

Sequence of ABS Operation and Steering Retention
Estimated Time:45s
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Topics

Braking Systems and ABS

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