ABS modulation: Notes

Fig 1: ABS Modulation Graph

Courtesy of SAAB-SCANIA OF AMERICA, INC.

1. Speed
2. Brake force
3. Vehicle speed
4. Wheel speed
5. Inlet valve open, outlet valve closed
6. Inlet valve closed, outlet valve closed
7. Outlet valve open, return pump activated

The ESP control module continually monitors wheel speed. If the value for a wheel exceeds the slip limit, the control module activates the ABS function and modulates the brake pressure to the wheel (s) in 3 phases. The modulation of the front brakes is individual, while the rear brake pressure is distributed evenly and determined by the wheel with least grip (greatest slip).