PRE-SAFE ® Brake, Function - GF30.30-P-3340RF
Model 205
up to model year 2019
with code 271 (Autonomous brake intervention/pedestrian protection)
Model 205
up to model year 2019
with code 300 (PRE-SAFE® Brake)
Model 253 (except 253.99)
up to model year 2020
with code 271 (Autonomous brake intervention/pedestrian protection)
Model 253 (except 253.99)
up to model year 2020
with code 300 (PRE-SAFE® Brake)
Function requirements, general
- No undervoltage or overvoltage
- "BasExtd_Avl" (with code 268 (Brake Assist PLUS)) programmed in electronic ignition lock control unit
- "CMS_Avl" programmed in electronic ignition lock control unit
- PRE-SAFE® brake in "Driving Assist" of instrument cluster switched on:
The status of the PRE-SAFE® brake function is sent by the instrument cluster via the user interface CAN, electronic ignition lock control unit and the chassis FlexRay to the radar sensors control unit.
- Engine running or drivetrain operational:
The CDI control unit or the ME-SFI [ME] control unit sends the "Engine running" or "Drivetrain operational" signal to the radar sensors control unit via the drive train CAN, powertrain control unit and chassis FlexRay.
- Gear range "D" engaged (vehicle not in backward movement):
The fully integrated transmission control unit sends information about the selected gear range via drive train CAN, powertrain control unit and suspension FlexRay to the radar sensors control unit.
- Radar sensor system soiling and function test for the radar sensor system completed successfully:
Object recognition (e.g. vehicle moving directly ahead) via the radar sensor system is based on the radar measuring procedure.
The front long range radar sensor and the front bumper radar sensors run a contamination and function test after each engine start to ensure that they are functioning correctly. The function test requires an object in the respective detection area that is used as a reference object. If a malfunction is established or if there are no objects in the detection area, the PRE-SAFE® brake cannot be activated. The radar sensors control unit receives the signals of the front bumper radar sensors via the radar-CAN 1 and sends them over the chassis FlexRay to the front long range radar sensor. The front long range radar sensor evaluates them in combination with its own signals and, when all the radar sensors are functioning correctly, sends the "Radar sensor system operational" status via chassis FlexRay to the radar sensor control unit.
- Stereo multifunction camera soiling and function test:
The stereo multifunction camera performs a soiling and function test to ensure proper operation after each engine start. The function test requires an object in the respective detection area that is used as a reference object. If a malfunction is established or if there are no objects in the detection area, the PRE-SAFE® brake cannot be activated. The stereo multifunction camera sends the lane data via the chassis FlexRay to the radar sensors control unit.
- Electronic Stability Program (ESP®) not switched to passive mode: The Electronic Stability Program control unit sends the status of the Electronic Stability Program® via the suspension FlexRay to the radar sensors control unit.
- No active ESP® intervention recognized (vehicle not in sliding movement)
- Vehicle speed from v = 7 to 200 km/h:
The vehicle speed is calculated from the wheel speeds, the direction of travel is defined by the wheel rotation direction. The Electronic Stability Program control unit sends this information about wheel speed and wheel rotation direction to the radar sensors control unit via chassis FlexRay.
- Standstill control, enable issued (driver door/driver belt buckle and front passenger door closed):
The acceleration/yaw rate is detected by the acceleration sensor integrated into the Supplemental Restraint System control unit. The supplemental restraint system control unit sends the corresponding values via the vehicle dynamics CAN to the Electronic Stability Program control unit. The Electronic Stability Program control unit transmits these via the suspension FlexRay to the radar sensors control unit.
PRE-SAFE® brake, general points
The PRE-SAFE® brake assesses the traffic situation in front of the vehicle and continuously determines the hazard potential for a rear-end collision. Depending on factors such as the distance from a stationary or moving object, the difference in speed relative to a preceding vehicle as well as driving dynamic factors, a visual (static distance warning) or a visual-acoustic warning (collision-critical distance warning) is output. The distance warning is output up to a speed of v = 250 km/h. To prevent a collision or at least reduce the consequences, an autonomous partial braking is first initiated in the case of a collision-critical situation (driver does not react to the warning messages) followed by a maximum full-stop braking. In the case of stationary obstacles and pedestrians, the PRE-SAFE® brake is only activated if the own vehicle speed is max. v = 72 km/h.
Model 205
up to model year 2019
with code 271 (Autonomous brake intervention/pedestrian protection)
with code 299 (PRE-SAFE® system)
Model 205
up to model year 2019
with code 299 (PRE-SAFE® system)
with code 300 (PRE-SAFE® Brake)
Model 253 (except 253.99)
up to model year 2020
with code 271 (Autonomous brake intervention/pedestrian protection)
with code 299 (PRE-SAFE® system)
Model 253 (except 253.99)
up to model year 2020
with code 299 (PRE-SAFE® system)
with code 300 (PRE-SAFE® Brake)
The PRE-SAFE® brake feature also supports the PRE-SAFE® safety concept.
Illustration of principle of the PRE-SAFE® brake function at v ≥ 30 km/h, shown on model 205.0
After autonomous maximum full-stop braking, the vehicle will remain stalled for a time period of approx. t = 1 s.
Function sequence for PRE-SAFE® brake
The PRE-SAFE® brake requires the following input factors to implement the distance warning and autonomous partial and emergency braking functions:
- Object recognition in the long range
- Object recognition in the short range
- Object detection of stationary and slow moving pedestrians by the stereo multifunction camera (with code 271 (Autonomous intervention by the brake system/pedestrian protection))
Detection ranges for radar sensor system/stereo multifunction camera, shown on model 205.0
Object recognition in the long range:
The front long-range radar sensor monitors the traffic area in front of the vehicle up to a distance of s = 200 m in a corridor of ∠ = 18°.
Objects up to a distance of s = 0 to 60 m are detected in a corridor of ∠ = 60°.
The front long range radar sensor operates according to the pulse modulated Doppler principle, which enables the distances and speeds of individual objects (e.g. vehicles) to be measured independently of each other.
The front long-range radar sensor sends corresponding information via the chassis FlexRay to the radar sensors control unit.
Object recognition in the short range:
Up to a distance of s = 30 m, objects are also detected by the front bumper radar sensors (short-range radar sensor system). The object detection by the short range radar sensor system simply serves to allow plausibility checking.
The front bumper radar sensors send information via the radar CAN 1 to the radar sensors control unit.
Detection of stationary and slow-moving pedestrians (with code 271 (Autonomous intervention by the brake system/pedestrian protection)): Pedestrians, who are located in the lane area, can be detected in a vehicle speed range up to v = 72 km/h.
People are detected by the stereo multifunction camera, the front long range radar sensor and the front bumper radar sensors.
The radar sensor system detects people or objects, and it can conduct positioning within a defined range - dependent on the distance from the person or object involved and the vehicle speed. It is not however capable of performing exact positioning in the transverse direction. This is why redundant detection by the stereo multifunction camera is required.
The stereo multifunction camera consists of two high-resolution mono cameras and an integrated control unit for evaluation and a plausibility check of the supplied picture data. The offset location of the two mono cameras creates a difference in perspective (parallax displacement) between the left and right optical path. The distance to the object ahead and other variables such as the height, sized and scope or the speed of movement thereof are calculated on the basis of the differences between the image data.
The stereo multifunction camera sends the lane data via the chassis FlexRay to the radar sensors control unit.
If objects are detected in the vehicle's lane (vehicle speed range from v = 7 to 200 km/h) by the radar sensor system and/or by the stereo multifunction camera, the radar sensors control unit outputs a static or collision-critical distance warning.
Static distance warning:
Output of the static distance warning takes place purely optically. The static distance warning is triggered (at a vehicle speed of v > 30 km/h) if the time interval between the vehicle and the preceding vehicle falls below t = 0.8 s (e.g. in moving traffic). The DISTRONIC warning lamp lights up in the IC.
The radar sensors control unit sends the corresponding request via the chassis FlexRay, electronic ignition lock control unit and the user interface CAN to the instrument cluster.
Collision critical distance warning:
Output of the collision-critical distance warning takes place optically and acoustically.
If a moving or stationary obstacle is classified as accident critical in the radar sensor system detection range at a vehicle speed of v > 7 km/h, the DISTRONIC warning lamp lights up and the instrument cluster speaker also outputs an intermittent warning tone.
The warning is switched off again automatically one the situation is no longer critical.
The radar sensors control unit sends a corresponding request to actuate the instrument cluster speaker via the chassis FlexRay, electronic ignition lock control unit and the user interface CAN to the instrument cluster. The instrument cluster directly actuates the instrument cluster speaker.
Optical warning messages in instrument cluster
This is shown inversely in the multifunction display, i.e. the distance warning readiness display is hidden for an active distance warning function. If the distance warning function is deactivated, the distance warning readiness indicator and the "OFF" lettering are shown.
If the driver does not react to the warnings, the PRE-SAFE® brake initiates autonomous partial braking. To do this the radar sensors control unit calculates a corresponding braking torque while taking account of the driving dynamics input factors.
The radar sensors control unit sends the corresponding request via the suspension FlexRay to the Electronic Stability Program control unit which then directly actuates the traction system hydraulic unit. If the driver responds with emergency braking, BAS PLUS is activated. To optimally use the braking distance up to the obstacle, the BAS PLUS supports the driver during a maximum full-stop braking.
The Electronic Stability Program control unit the braking request of the driver about the increasing brake pressure in the master brake cylinder.
The brake pressure is registered by the front axle brake pressure sensor.
The Electronic Stability Program control unit directly reads in the signal from the front axle brake pressure sensor, calculates the braking torque requested by the driver and sends this information via the chassis FlexRay to the radar sensors control unit.
Model 205.012/047/147/212/247
up to model year 2019
with code 271 (Autonomous brake intervention/pedestrian protection)
Model 205.012/047/147/212/247
up to model year 2019
with code 300 (PRE-SAFE® Brake)
Model 253.354/954
up to model year 2020
with code 271 (Autonomous brake intervention/pedestrian protection)
Model 253.354/954
up to model year 2020
with code 300 (PRE-SAFE® Brake)
The kinetic energy is converted within defined limits into electrical energy (regenerative braking). If the requested braking torque exceeds the deceleration through recuperation (for example in a case of a emergency braking), the Electronic Stability Program control unit additionally actuates the traction system hydraulic unit and therefore the service brake.
To prevent a collision or reduce the possible accident effects, the radar sensors control unit initiates a maximum full-stop braking if the driver does not react to the partial braking (evasive maneuver, BAS PLUS supported maximum full-stop braking).
Emergency braking is only triggered if the driver and the front passenger have their seat belts on.
Model 205
up to model year 2019
with code 271 (Autonomous brake intervention/pedestrian protection)
with code 299 (PRE-SAFE® system)
Model 205
up to model year 2019
with code 299 (PRE-SAFE® system)
with code 300 (PRE-SAFE® Brake)
Model 253 (except 253.99)
up to model year 2020
with code 271 (Autonomous brake intervention/pedestrian protection)
with code 299 (PRE-SAFE® system)
Model 253 (except 253.99)
up to model year 2020
with code 299 (PRE-SAFE® system)
with code 300 (PRE-SAFE® Brake)
In parallel, the PRE-SAFE® function implemented in the Electronic Stability Program control unit evaluates the currently requested braking torque and initiates appropriate measures to protect the vehicle occupants if necessary.
| Electrical function schematic for PRE-SAFE® brake | PE30.30-P-2060-97FBA | ||
| Overview of system components for driver assistance systems | Model 205 up to model year 2019 with code 271 (Autonomous brake intervention pedestrian protection) Model 205 up to model year 2019 with code 300 (PRE-SAFE® Brake) Model 253 (except 253.99) up to model year 2020 with code 271 (Autonomous brake intervention pedestrian protection) Model 253 (except 253.99) up to model year 2020 with code 300 (PRE-SAFE® Brake) |
GF54.00-P-9998RF |