Anti-lock braking system prevents your car's brakes from "locking up" and skidding. When the brake pedal is hit with force, short sharp pulsations are felt as the car's computer system applies and release braking effort. A typical ABS is composed of a central electronic unit (CEU), four speed sensors covering all wheels, and two or more hydraulic valves connected to the brake circuit. The CEU continiously monitors the rotation speed of each wheel to determine if wheels are going to lockup. It can detect this by sensing wheels which are rotating considerably slower than the others. Once it has detected a possible lockup - the CEU moves the valves to help relieve the pressure within the braking circuit, by doing so it helps to reduce the braking force on the targetted wheel. Following that the wheel then turns faster and when it starts turning too fast, the force is reapplied. The ABS system does the prococess repeatedly.
Problems with ABS
The sensors on the wheels might get contaminated by metallic dust. When this condition occurs the sensors become less efficient in picking up problems. In modern ABS systems, two more sensors are added to help:
- wheel angle sensor,
- gyroscopic sensor
The idea behind this is that when the gyroscopic sensor detects that the car's direction is not the same as what the wheel sensor reports, the ABS software will cut in to brake the necessary wheel in order to help the car go the direction the driver intends.
For more information on how ABS works, click here