Brake Control BS3

Sensotronic Brake Control (SBC) is an electro-hydraulic brake system, where the wheel brake cylinders on a vehicle are operated through a servomechanism.

The SBC system was developed by Daimler and Bosch, was introduced on the R230 SL-class, which went on sale in Europe in October 2001.

In a pure hydraulic brake system, the driver applies force to a pedal by a mechanical link which then directly applies force to the master brake cylinder. In turn the master brake cylinder develops hydraulic pressure inside the wheels.

In contrast, the SBC operates the brakes using brake fluid supply from a hydraulic high-pressure reservoir, which is sufficient for several braking events. A piston pump driven by an electric motor supplies a controlled brake fluid pressure of range between 140 bars (2,000 psi) and 160 bars (2,300 psi) in the gas diaphragm reservoir. 

When the driver presses the brake pedal—or when electronic stability control (ESP) intervenes to contrast the vehicle —the SBC control unit calculates the desired target brake pressures on each individual wheel. Through the use of independent pressure modulators the system regulates a hydraulic pressure at each wheel. These four pressure modulators consist of one inlet and one outlet valve, controlled by electronic output stages.

The system employs a travel sensor and a pressure sensor at the pedal to measure the speed and force of the driver’s command. The control unit processes this information and generates the control signals for the wheel pressure modulators. Normally, the master brake cylinder is detached from the brake circuit. A pedal travel simulator creates normal pedal feedback. If ESP intervenes, the high-pressure reservoir supplies the required brake pressure quickly and precisely to selected wheels, without any driver involvement.