When sudden heavy braking causes the wheels to begin skidding on a compromised road surface, the Anti-lock Braking System (ABS) automatically executes a high-speed closed-loop control sequence. How should these stages of the ABS electronic and hydraulic operational cycle be arranged in the correct chronological order?
- 1Wheel-speed sensors signal to the electronic control unit (ECU) that a wheel's rotational speed has dropped abruptly relative to vehicle road speed, indicating impending lock-up.
- 2The electronic control unit commands the hydraulic modulator valve to isolate and release hydraulic fluid pressure from the brake caliper of the affected wheel.
- 3Frictional contact with the road surface causes the released wheel to regain rotational velocity and restore directional steering control.
- 4The hydraulic modulator pump re-pressurises the brake line to reapply clamping force up to the threshold of maximum road grip.
- 5The pressure release and re-application cycle repeats multiple times per second, creating a distinct pulsation through the brake pedal until traction stabilizes.
Answer
The correct operational order begins with wheel-speed sensors detecting impending lock-up, followed by the hydraulic modulator reducing caliper pressure, the wheel regaining rotation and grip, the modulator re-applying hydraulic pressure, and finally the high-frequency repetition of this cycle causing pedal pulsation.
The Anti-lock Braking System functions as an automated feedback loop. First, wheel sensors detect that deceleration is excessive relative to vehicle movement. Second, the hydraulic modulator dumps fluid pressure to prevent the wheel from freezing. Third, the unbraked tyre spins up and regains rolling traction. Fourth, pressure is re-introduced to maximize stopping power. Finally, this process repeats rapidly (15-20 times per second), creating the characteristic pedal pulsation.
Step-by-Step Solution
Key Concept
ABS closed-loop electro-hydraulic cycle and wheel slip regulation
Estimated Time:2m 0s