Hybrid Brake Actuation Changeover
The "hybrid brake actuation changeover" designates the unit composed of the control unit and hydraulic unit. It is also referred to as the Sensotronic Brake Actuation SBA. The installation location of the SBA unit is to the left of the brake servo. It can only be replaced as a complete unit.
The SBA control unit assumes the master role for brake activation. It measures the driver's braking request and splits this total braking torque into a regenerative portion and a hydraulic portion. For this purpose, the SBA control unit has the following electrical interfaces:
- Brake pedal angle sensor
- Shut-off valve of the shut-off unit
- Pressure sensor of the shut-off unit
- Solenoid valve in the brake servo
- Diaphragm travel sensor in the brake servo
- Brake vacuum-pressure sensor in the brake servo
- Electrical vacuum pump (activation and monitoring)
- Voltage supply
- PT-CAN and H-CAN 2 bus systems
To implement the regenerative portion, the SBA control unit communicates with the hybrid master control unit via the hybrid CAN 2, hybrid interface module and hybrid CAN. The SBA control unit transmits the hydraulic portion by directly activating the solenoid valve in the brake servo. Here, as with all interventions into the hydraulic brake system, the DSC control unit is an important communication partner for the SBA control unit. The following is a summary of important input and output variables of the SBA control unit that are transmitted via bus systems:
| Information | Direction | Source/sink |
|---|---|---|
| Request regenerative braking torque | Output | SBA > HCP, SBA > DSC > VTG |
| Request hydraulic brake power assistance | Output | SBA > DSC |
| Maximum possible regenerative braking torque | Input | DSC > SBA, HCP > SBA |
| Driving speed and wheel speeds, longitudinal acceleration | Input | DSC > SBA |
| Stability of the driving situation | Input | DSC > SBA |
| Status of operating readiness | Input/output | DSC > SBA, HCP > SBA, DME > SBA SBA > DSC, SBA > HCP, SBA > DME |
| Index | Explanation |
|---|---|
| 1 | Electrical connector |
| 2 | Hydraulic part |
| 3 | Bracket |
| 4 | Connection for rear brake circuit brake line, input from tandem brake master cylinder |
| 5 | Connection for rear brake circuit brake line, output to DSC unit |
| 6 | Connection for front brake line, output to DSC unit |
| 7 | Connection for front brake line, input from tandem brake master cylinder |
| 8 | Control unit |