Regenerative Brake Mode, Function - GF42.22-P-1000GRH
MODEL 166.063 as of model year 2016
Diagram of operating principle
Function requirements for regenerative brake mode, general
- Hybrid system "READY"
- Selector lever position "D"
- Vehicle speed > 8 km/h
Regenerative brake mode, general
The driver's brake command is detected by the pedal angle sensor and sent to the Electronic Stability Program control unit.
The Electronic Stability Program control unit communicates continuously over the chassis CAN 1 (CAN E1), powertrain control unit (N127) and the engine CAN (CAN C1) with the ME-SFI [ME] control unit (N3/10) and the power electronics control unit about the value of the currently available, the requested and the applied regenerative braking torque.
Regenerative brake mode function sequence
The ME-SFI [ME] control unit forecasts the current status of the maximum available regenerative braking torque which can be generated by the electrical machine.
The status is sent by the ME-SFI [ME] control unit over the engine CAN and the chassis CAN 1 using the powertrain control unit interface to the Electronic Stability Program control unit.
If the high-voltage battery (A100g1) is fully charged, regenerative braking is not possible. In this case, braking is performed solely by the hydraulic brake until the high-voltage battery is partly discharged again through energy takeoff and can again absorb electrical energy. In the event of ABS control (antilock braking system), regenerative braking for this braking operation is terminated and the braking torque is applied solely by the hydraulic service brake.
The Electronic Stability Program control unit divides the overall braking torque moment requested by the driver according to the driving condition into a regenerative part (to be applied by the drive train) and a hydraulic part (to be applied over the service brake). If the requested total braking torque can be fully regenerated, then the split into an additional hydraulic portion is no longer required. In this case the deceleration is generated solely by the alternator output. As soon as a speed of less than 20 km/h is recorded during a brake application, a switchover takes place from regenerative braking to hydraulic braking. Regenerative braking is not possible at speeds lower than 3 km/h.
The 3-phase AC voltage generated during regenerative braking by the electric machine is converted by the power electronics control unit into high-voltage DC voltage and supplied to the high-voltage battery.
On the regenerative braking system control unit the brake pedal connection to the push rod of the BAS brake booster has free travel (3) integrated into it. This is used to display the regenerative braking system control unit's functionality. When in normal operation the driver's brake command is recorded by the pedal angle sensor using the pedal travel (1) and read in and processed by the Electronic Stability Program control unit. At the same time the brake pressure simulator valve generates a simulated pedal resistance each time the brakes are actuated. If regenerative braking is used, it increasingly reduces the free travel (3) between the brake pedal and push rod as the regenerative braking torque increases. The regenerative braking system is activated during the first brake actuation. While doing so, the brake pressure simulator is deactivated resulting in a somewhat longer pedal travel than in normal operation during the first brake actuation.
Once the brake pedal has been completely released again, the regenerative braking system is activated again.
As a matter of principle, the brake pedal feeling on a regenerative braking system is perceived differently from that on a conventional brake system.
Regenerative braking is switched off for the driving cycle, when the requested regenerative braking torque is not correctly provided or in the event of any malfunction in the hybrid system.
The braking torque actually applied is sent by the power electronics control unit over the hybrid CAN (CAN L) and chassis CAN 1 back to the Electronic Stability Program control unit.
| Overview of system components for regenerative braking system | GF42.22-P-9999GRH |