Meanwhile electronically regulated brake boosters are available today. They can fulfill the following tasks:
In emergency situations, drivers often do not generate the necessary braking force for drastic braking. A sensor identifies this condition and ensures maximum possible deceleration (brake assistant).
For traction and driving dynamics control, among others, certain targeted brake interventions are necessary. Since the driver does not operate the brake pedal while doing so, the necessary brake force has to be generated by the brake booster.
The latest generations of cruise control also require brake interventions in the absence of a foot force created by the driver, such as on steep downward gradients or in automatic convoys.
From the point of view of improved comfort and safety, the creation of a constant foot force at a constant deceleration, independent of load would be favourable. This also requires an individual adjustment of the brake boost.
It has to be stressed, however, that an electronically controlled brake booster does not regulate the brake force at the wheel, but is rather involved in the creation and regulation of the output force FO.
The production of an auxiliary force in hydraulic brake boosters can in general be achieved pneumatically via the intake vacuum of the engine, or hydraulically using a separate pump. A vacuum brake booster is shown in the figure. The intake manifold vacuum acts on both sides of an extensive diaphragm plate. A soft conical spring moves the diaphragm plate to one side of the vacuum booster. As soon as the driver operates the brake pedal, air at atmospheric pressure flows onto the opposite side of the diaphragm plate. The resulting pressure difference on both sides of the diaphragm plate produces the supporting auxiliary force. A control valve provides a constant boost factor up to the modulation point.