GF42.47-P-2000TM Additional Functions, Adaptive Brake (ABR), Function

GF42.47-P-2000TM Additional functions, adaptive brake (ABR), function

The following additional functions are integrated in the Adaptive Brake (ABR) and are coordinated by the ESP control unit (N47-5):
^ Electronic brake force distribution (EBV)
^ HOLD
^ Precharging
^ Dry braking

Additional function

Electronic brake force distribution (EBV)
EBV assists the driver in the partial braking area. The system prevents overbraking of the rear axle and increases the vehicle stability in the curve, the brake pressure at the rear wheel on the inside of the curve being reduced or the pressure at the front wheel on the outside of the curve being increased if necessary.

Additional function

HOLD
HOLD makes like easier for the driver if desired
^ When starting off, driving uphill
^ When maneuvering on mountain roads
^ When waiting in traffic

With USA and CDN the additional function HOLD is deactivated by coding in the ESP control unit. This takes place through the coding information from the central gateway control unit (N93).

HOLD function description
HOLD can be switched on by operating the brake pedal (via the stop lamp switch (S9/1)) when the vehicle is stationary. The vehicle is then held in position without any further actuation of the brake pedal. The braking affect is canceled when starting off by pressing the accelerator (via the accelerator pedal sensor (B37)).

Switching on HOLD
Hold can be switched on when:
^ the vehicle is stationary
^ the engine hood is closed
^ the engine is running
^ the selector lever is not in position "P" (with transmission 722)

Operate the brake pedal, the depress the brake pedal briskly again until the message "HOLD" appears in the multifunction display (A1p13). The vehicle is held automatically when the brake pedal is subsequently released.

Switching off HOLD
Hold is switched off automatically when:
^ the accelerator is operated
^ the selector lever is switched into position "P" (with transmission 722)
^ the brake pedal is operated again until the display "HOLD" goes out in the multifunction display
^ the parking brake is operated

The case of ignition "Off" HOLD
Holding the brake pressure is finished when the driver changes the vehicle over to a safe condition after ignition "Off". The "P" position is read in and evaluated permanently via the driver-side SAM control unit with fuse and relay module (N10/1) discretely by the electronic selector lever module control unit (N15/5) (with transmission 722). A signal is passed on to the ESP control unit by the driver SAM when "P" position is engaged (with transmission 722). HOLD is finished as a result.

Deactivation enforcement of HOLD function by the driver
In order to enforce a deactivation of HOLD before leaving the vehicle, optical and acoustic warning messages are output in various escalation stages.
^ Warning message in the instrument cluster when:

- circuit15 ON and the driver door is opened

^ Regular discreet horn tone when:

- circuit15 OFF and the driver door was or is opened

^ Regular loud horn tone when:

- in addition an attempt is made to lock the vehicle

The horn is actuated by the passenger-side SAM control unit (N10/11).

Termination of horn
The horn is always terminated as soon as the driver has deactivated HOLD. This can take place by shifting the selector lever into position "P" (with transmission 722) or by operating the brake pedal.

CAN communication
The Controller Area Network bus class B (interior) (CAN-B) is kept awake by the driver SAM as long as hold is activated.

Actuation of horn
The front passenger-side SAM control unit transmits the signal for horn actuation on CAN-B. The driver SAM control unit receives the request for sounding the horn and actuates the left fanfare horn (H2) (model 219) or fanfare horns (H2) (model 211) and right fanfare horn (H2/1).

On-board electrical system of HOLD
If HOLD is active with circuit 15 OFF, the power supply for maintaining HOLD must be ensured. An active system is detected via a signal which is transmitted from the driver SAM on CAN B irrespective of the circuit status and an activation of HOLD is displayed.

Display concept of HOLD
The display concept of hold as well as the plausibility check of the driver door status are implemented in the instrument cluster.

Actuation of warning messages
Warning messages (e.g. "HOLD Off") are only actuated by the ESP control unit.

Differentiation of warning message depending on the transmission model
Different warning messages are output depending on the transmission model:

With transmission (716): "Immediate braking"

With transmission (722): "Selector lever to P"

Fault warning message in the event of system faults
The driver is informed by messages in the multifunction display as well as warning lamps and indicator lamps in the instrument cluster.

Door contact plausibility check
The plausibility check serves to detect a fault in the signal path from the left front door contact switch (S17/3) to the instrument cluster. If as a result of an electrical or mechanical fault "driver door closed" or "driver door open" is detected erroneously, although the driver door is opened or closed, this is detected by the plausibility logic in the instrument cluster and a corresponding fault is entered. The driver cannot activate HOLD any more or receives a warning message in the instrument cluster when HOLD is already activated. In the event of an attempt to activate HOLD a fault is entered in the ESP control unit.

Driver status
A belt tongue plugged into the seat belt buckle or shifting from position "P" when the driver door is closed is interpreted as the presence of the driver. When the driver door is open and a belt tongue is not plugged into the seat belt buckle the driver status is not clear and the driver is thus presumed to be absent. HOLD is not activated when the driver status is not clear.

Additional function

Precharging
The function is constantly active and assists the performance of the brake system by already applying the brake linings (precharging) when the brake pedal is released. As a result the response time of the brake is reduced and the stopping distance shortened during emergency stops.

Function description of precharging
To reduce the response time during panic braking the air gap of the wheel brake system is already overcome when the accelerator pedal is released and the brake linings are applied with a pressure up to 4 bar. If the driver then depresses the brake pedal, a spontaneous braking effect is achieved and thus the stopping distance is shortened. The accelerator pedal release gradient is used in the process to detect a rapid braking requirement. The precharging process is terminated after a short time if the driver does not apply the brake.

Determining the triggering threshold for precharging
If the boundary conditions are met, the associated release gradient is determined each time the accelerator pedal is released completely. The triggering threshold depends on the pedal travel. With small pedal travels before the pedal is released, a smaller pedal release travel is necessary in order to activate precharging than with large pedal travels before the pedal is released.

Precharging is not active, if:
^ ESP faults are present
^ Control intervention function by ABS, ESP or ASR
^ Faults present in the engine control
^ CAN faults are present
^ Precharging is deactivated by coding

Additional function

Dry braking
The function is constantly active and assists the performance of the brake system in the wet. Dry braking the brake disks in cycles reduces the response time of the brake.

Function description of dry braking
To activate dry braking the position of the windshield wiper is read in via the contact "windshield wiper outside park position" by the driver SAM. Dry braking itself is carried out for a few seconds with a very small brake pressure (< 1 bar) on the front axle only.