Braking Assistant (BAS) - Operation - GF42.31-P-0001T
MODEL 211 up to 31.5.06 except CODE (494) USA version except CODE (498) Japan version
MODEL 211 up to 30.6.06 with CODE (494) USA version with CODE (498) Japan version
Brake diagram
Electronic Stability Program (ESP) Function Diagram. Scheme 39
Braking behavior
A distinction is made between
- Hesitant braking, e.g. in the initial phase the driver applies too little pedal force and increases it too slowly.
- Inadequate braking, e.g. the driver applies too little pedal force throughout the entire braking application.
Brake Assist (BAS) has been developed to improve these situations.
Task
Brake Assist (BAS) is part of the active safety system. It becomes active when the driver brakes very quickly in an emergency situation. The system detects whether an emergency braking situation exists on the basis of the speed at which the driver presses the brake pedal. If this is the case, the high-pressure charging pump (A7/3m1) in the traction system hydraulic unit (A7/3) must be activated and as a result the full brake force is reached. If the driver releases the brake, this is detected and the high-pressure charging pump (A7/3m1) is switched off again.
Advantages
- The BAS system reduces the accident risk in dangerous situations by optimum braking deceleration and thus assists the driver considerably.
- The BAS system significantly reduces the brake distance during hesitant or inadequate braking.
Function overview
Brake Assist (BAS) is fully integrated in the Electronic Stability Program (ESP). The electronics are located in the ESP control unit (N47-5). The pressure reservoir in the traction systems hydraulic unit is used for pressure generation (A7/3).
After the driver starts the engine, a vehicle identification and selfcheck of the system takes place.
BAS is operational when no fault exists and the vehicle exceeds a speed of 10 km/h after starting off. BAS can be activated down to a speed of 3 km/h.
Using the speed of the pressure rise in the front axle pre-pressure sensor (A7/3b1) and the signal from the SBC pedal value sensor (B37/1) the ESP control unit (N47-5) calculates the operating speed of the brake pedal. The operating speed of the brake pedal and the vehicle speed are recorded in the ESP control unit (N47-5).
If the pedal speed is greater than the threshold value specified for the respective vehicle speed, the high-pressure charging pump (A7/3m1) in the traction system hydraulic unit (A7/3) is actuated and thus the full brake force is reached.
The is not used in the event of a defect; this is displayed by the multifunction display (A1p13) in the instrument cluster (A1). The normal function of the brake is not affected by this
| Electronic stability program (ESP), driver information | GF42.45-P-0001-04T | ||
|---|---|---|---|
| BAS brake application, function | GF42.31-P-2000T |
Contents - Braking Assistant (BAS) Description of Operation - GF42.31-P-0999T
MODEL 211 up to 31.5.06 except CODE (494) USA version except CODE (498) Japan version
MODEL 211 up to 30.6.06 with CODE (494) USA version with CODE (498) Japan version
| Brake Assist (BAS) function | GF42.31-P-0001T | ||
|---|---|---|---|
| Electronic stability program (ESP), driver information | GF42.45-P-0001-04T | ||
| BAS Braking Assistant - Operation | GF42.31-P-2000T | ||
| Survey of system components, Brake Assist (BAS), location/task/design/function | GF42.31-P-9999T |
BAS Braking Assistant - Operation - GF42.31-P-2000SL
MODELS 230
Function
The brakes for BAS are applied in exactly the same way as with normal brake application, but with BAS the pressure is increased more quickly according to the speed at which the driver presses the brake pedal.
From the operating speed of the brake pedal and the vehicle speed the ESP, SPS [PML] and BAS control unit (N47-5) recognizes that the conditions for switching on the BAS exist.
BAS is switched on when the following conditions exist
- The speed is > 10 km/h.
- The stop lamp switch (S9/1) is operated.
- No current fault is detected.
- The system is released after a self-test.
- The pedal speed threshold is exceeded.
BAS is switched off when one of the following conditions is present
- The brake pedal pressure is reduced by the driver to such an extent that emergency braking is no longer required.
- The stop lamp switch (S9/1) is not operated.
- The speed is < 3 km/h.
- A fault is detected which leads to the actuation of the left multifunction display (A1p13) and right multifunction display in the A1 instrument cluster (A1).
| ESP control unit, location/task/function | GF42.45-P-4500SL | ||
|---|---|---|---|
| Location/task/function of stop lamp switch | GF42.10-P-4000A | ||
| Location/task/design/function of traction systems hydraulic unit | GF42.50-P-4000S |
Table of contents: Functional description, Electronic Stability Program (ESP) - GF42.45-P-0999E
MODEL 211 up to 31.5.06 except CODE (494) USA version except CODE (498) Japan version
MODEL 211 up to 30.6.06 with CODE (494) USA version with CODE (498) Japan version
Notes on towing AH42.00-P-0001-05B Notes on testing electronic components and systems for damage resulting from an accident AH42.00-P-0001-06B Electronic stability program (ESP) function GF42.45-P-0001T Electronic stability program (ESP) driver information GF42.45-P-0001-04T Electronic stability program (ESP), location of electronic components GF42.45-P-0001-03EE ESP braking moment control circuit, function GF42.45-P-2000TX ASC drive torque control circuit, function GF42.40-P-2100T ABS closed-loop operation function GF42.45-P-3000TX ASC control mode, function GF42.45-P-3500TX ESP control mode, function GF42.45-P-3700TX Braking Assistant (BAS) - Operation GF42.31-P-0001T Survey of electronic stability program (ESP) system components, location/task/design/function GF42.45-P-9999E
ABS closed-loop operation function - GF42.45-P-3000SL
MODEL 230
MODEL 240
Scheme 40
ABS closed-loop operation, pressure buildup (shown on model 230)
Each ABS control phase begins with normal application of the brakes when the driver presses the brake pedal. The SBC control unit calculates the brake pressure and begins the control phase.
The ESP, SPS [PML] and BAS control unit (N47-5) detects the brake application via signals (pedal value sensor, wheel speeds, brake pressure) from the SBC control unit.
The left and right front separation valves (y1 and y2) are closed at the start of the braking application. They only remain closed during the control and are otherwise (de-energized).
All outlet control valves (y7, y9, y11, y13) are also closed. All inlet control valves (y6, y8, y10, y12) are opened. The front axle and rear axle balance valves (y3 and y4) remain open.
The pressure from the pressure reservoir (3) can now be increased at the brake calipers of the front axle via the front left and right dividing pistons (7 and 8). The pressure is increased directly at the rear axle.
Identifying ESP Control Module Location. Scheme 41
ABS closed-loop operation pressure holding
The control process shown in the example and the valve positions refer to the FR brake.
If a wheel shows a tendency to lock during the brake application, the ABS prevents a further buildup of pressure. The ESP, SPS [PML] and BAS control unit (N47-5) introduces the pressure holding phase from the slip values of the braked wheels.
The pressure holding phase is introduced by actuating the solenoid valves (y8 and y3). In this control phase the solenoid valves (y3, y8 and y9) remain closed; the pressure in the FR brake caliper remains constant as a result.
Identifying Wheel RPM Sensor Components Location - Shown On Model 230. Scheme 42
ABS closed-loop operation, depressurization
The control process shown in the example and the valve positions refer to the FR brake .
The ESP, SPS [PML] and BAS control unit (N47-5) introduces the pressure reduction phase from the slip values of the braked wheels.
The pressure reduction phase is introduced by actuating (opening) the solenoid valve (y9). The solenoid valve (y8) remains actuated (closed) in this control phase.
Brake fluid flows back into the reservoir via the return line during the pressure reduction phase.
| ESP control unit, location/task/function | GF42.45-P-4500SL | ||
|---|---|---|---|
| Traction system hydraulic unit/ location/task/design/function | Model 230 | GF42.50-P-4000S | |
| Model 240 | GF42.50-P-4000MB |
ABS closed-loop operation function - GF42.45-P-3000TX
MODEL 211, 219.3 up to 31.5.06 except CODE (494) USA version except CODE (498) Japan version
MODEL 211, 219.3 up to 30.6.06 with CODE (494) USA version with CODE (498) Japan version
Wheel Speed Sensor Function Diagram. Scheme 43
ABS control mode - pressure buildup
Antilock brake system (ABS) closed-loop operation
ABS control mode - pressure buildup
Each ABS control phase begins with normal application of the brakes when the driver presses the brake pedal. The SBC control unit (A7/3n1) calculates the brake pressure and starts with the control.
The ESP control unit (N47-5) detects the brake application from the SBC control unit via signals (SBC pedal value sensor, wheel speeds, brake pressure)
The left front separation valve and right front separation valve are closed. They only remain closed during the control and are otherwise opened (de-energized).
The left front outlet control valve, right front outlet control valve, left rear outlet control valve and right rear outlet valve are likewise closed. The left front inlet control valve, right front inlet control valve, left rear inlet control valve and right rear inlet control valve are open. The front axle and rear axle balance valves remain open.
The pressure from the pressure reservoir (3) can now be built up at the brake calipers of the front axle via the left front dividing piston (7) and right front dividing piston (8). The pressure is increased directly at the rear axle.
Identifying Steering Angle Sensor And Steering Column Module. Scheme 44
ABS closed-loop operation pressure holding, shown on the right front wheel brake (FR)
ABS closed-loop operation pressure holding
The control process shown in the example and the valve positions refer to the right front wheel brake (FR).
If a wheel shows a tendency to lock during the brake application, the ABS prevents a further buildup of pressure. The ESP control unit introduces the pressure holding phase from the slip values of the braked wheels.
The pressure holding phase is introduced by actuating the right front inlet control valve and front axle balance valve. In this control phase the right front inlet control valve, front axle balance valve and right front outlet control valve remain closed, as a result the pressure in the brake caliper of the right front wheel brake (FR) remains constant.
ABS Closed-Loop Operation Diagram - Pressure Reduction, Shown On Right Front Wheel Brake (RF). Scheme 45
ABS closed-loop operation pressure reduction, shown on right front wheel brake (RF)
ABS closed-loop operation, depressurization
The control process shown in the example and the valve positions refer to the right front wheel brake (FR).
The ESP control unit introduces the pressure reduction phase from the slip values of the braked wheels.
The pressure reduction phase is introduced by actuating (opening) the right front outlet control valve. The right front inlet control valve remains actuated (closed) in this control phase.
Brake fluid flows back into the reservoir via the return line during the pressure reduction phase.
| Electronic stability program (ESP) driver information | Model 219 | GF42.45-P-0001-04TX | |
|---|---|---|---|
| Model 211 | GF42.45-P-0001-04T | ||
| Wheel rpm sensor, component description | Model 219 | GF42.45-P-5134TX | |
| Location / task / design / function of wheel speed sensor | Model 211 | GF42.45-P-4550S | |
| Stop lamp switch - Description of components | Model 219 | GF42.10-P-2010TX | |
| Stop lamp switch. location/task/function | Model 211 | GF42.10-P-4000A | |
| Description of components in ESP control unit | Model 219 | GF42.45-P-5118TX | |
| ESP control unit, location/task/function | Model 211 | GF42.45-P-4500SL | |
| SBC control unit, component description | Model 219 | GF42.46-P-5132TX | |
| SBC control unit, location/task/function | Model 211 | GF42.46-P-4500SL | |
| SBC hydraulic unit, component description | Model 219 | GF42.50-P-5119TX | |
| Traction systems hydraulic unit, location/task/design/function | Model 211 | GF42.50-P-4000S | |
| Operating unit, component description | Model 219 | GF42.46-P-5130TX | |
| Operating unit, location/task/design/function | Model 211 | GF42.46-P-4200SL | |
| SBC pedal value sensor, component description | Model 219 | GF42.46-P-5133TX | |
| SBC pedal value sensor, location/task/design/function | Model 211 | GF42.46-P-4210SL |
Sensotronic Brake Control (SBC), contents, function description - GF42.46-P-0999E
MODEL 211 up to 31.5.06 except CODE (494) USA version except CODE (498) Japan version
MODEL 211 up to 30.6.06 with CODE (494) USA version with CODE (498) Japan version
Notes on towing AH42.00-P-0001-05B Notes on testing electronic components and systems for damage resulting from an accident AH42.00-P-0001-06B Sensotronic Brake Control (SBC), function up to 31.5.04 Models 211.004 /006 /016 /023 /026 / 028 /042 /043 /056 /061 /065 /070 /076 / 206 /216 /223 /226 /242 /243 /256 /261 / 265 /270 /276 /606 /616 up to 30.11.04 Model 211.080 /082 /083 /087 /280 / 282 /283 GF42.46-P-0001T Sensotronic Brake Control (SBC), function as of 1.12.04 up to 31.5.06 model 211.004 /006 /016 /023 /026 / 028 /042 /043 /056 /061 /065 /070 /076 / 206 /216 /223 /226 /242 /243 /256 /261 / 265 /270 /276 /606 /616 as of 1.6.04 to 31.5.06 except code (494) USA version except CODE (498) Japanese version As of 1.12.04 to 31.5.06 Model 211.080 /082 /083 /087 /280 / 282 /283 except code (494) USA version except CODE (498) Japanese version as of 1.6.04 up to 30.6.06 Models 211.004 /006 /016 /023 /026 / 028 /042 /043 /056 /061 /065 /070 /076 / 206 /216 /223 /226 /242 /243 /256 /261 / 265 /270 /276 /606 /616 with code (494) USA version with code (498) Japanese version As of 1.12.04 up to 30.6.06 Model 211.080 /082 /083 /087 /280 /282 /283 with code (494) USA version with code (498) Japanese version GF42.46-P-0001TA Sensotronic Brake Control (SBC) function, location of electrical components GF42.46-P-0001-03E Sensotronic Brake Control (SBC) function, location of hydraulic components GF42.46-P-0001-02E Electronic stability program (ESP), driver information GF42.45-P-0001-04T SBC normal braking, function GF42.46-P-1000T SBC additional functions, function up to 31.5.04 Models 211.004 /006 /016 /023 /026 / 028 /042 /043 /056 /061 /065 /070 /076 / 206 /216 /223 /226 /242 /243 /256 /261 / 265 /270 /276 /606 /616 up to 30.11.04 Model 211.080 /082 /083 /087 /280 / 282 /283 GF42.46-P-2000T SBC additional functions, function as of 1.12.04 up to 31.5.06 model 211.004 /006 /016 /023 /026 / 028 /042 /043 /056 /061 /065 /070 /076 / 206 /216 /223 /226 /242 /243 /256 /261 / 265 /270 /276 /606 /616 as of 1.6.04 to 31.5.06 except code (494) USA version except CODE (498) Japanese version As of 1.12.04 to 31.5.06 Model 211.080 /082 /083 /087 /280 / 282 /283 except code (494) USA version except code (498) Japanese version as of 1.6.04 up to 30.6.06 Models 211.004 /006 /016 /023 /026 / 028 /042 /043 /056 /061 /065 /070 /076 / 206 /216 /223 /226 /242 /243 /256 /261 / 265 /270 /276 /606 /616 with code (494) USA version with code (498) Japanese version As of 1.12.04 up to 30.6.06 Model 211.080 /082 /083 /087 /280 / 282 /283 with code (494) USA version with code (498) Japanese version GF42.46-P-2000TA SBC function brake application in the event of system fault GF42.46-P-3000T Sensotronic Brake Control (SBC), survey of system components, location/task/design/function GF42.46-P-9999E