Active Brake Assist With Cross-Traffic Function, Function - GF30.30-P-3341RFM

Model 205

as of model year 2019

with code 23P (Driving Assistance Package)

Model 253 (except 253.99)

as of model year 2020

with code 23P (Driving Assistance Package)

Courtesy of MERCEDES-BENZ USA

Function requirements, general

No undervoltage or overvoltage
"CMS_Avl" or "BasPlusQ_Avl" programmed in electronic ignition lock control unit
The electronic ignition lock control unit transmits the signal "Activated Brake Assistant with a intersection function" via the chassis FlexRay to the Mercedes-Benz Intelligent Drive control unit and to the MFK stereo and the signal "Collision mitigation" via the chassis FlexRay to the Mercedes-Benz Intelligent Drive control unit.
Active Brake Assist switched on with a intersection function in the head unit menu:
The status of the Active Brake Assist with cross-traffic function is sent by the head unit via the user interface CAN, electronic ignition lock control unit and the suspension FlexRay to the Mercedes-Benz Intelligent Drive 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 Mercedes-Benz Intelligent Drive control unit via drive CAN, powertrain control unit and suspension FlexRay.
Gear range "N" (only the distance warning active) or "D" engaged (vehicle not in backward movement):
The fully integrated transmission control unit (transmission 722, 724, 725) transmits information about the selected gear range via the drive train CAN, the powertrain control unit and the chassis FlexRay to the Mercedes-Benz Intelligent Drive control unit.
Soiling and function test of the short and long-range radar sensor:
Object recognition (e.g. vehicle moving directly ahead) via the radar sensor system is based on the radar measuring procedure.

The short and long range radar sensor performs a soiling and function test after every engine start to secure its perfect function.

The function test requires an object to be located in the detection area (this object is used as a reference value). If a malfunction is established or if there are no objects in the detection area, the Active Brake Assist cannot be activated.

The short and long range radar, when functioning properly, transmits the status "Radar sensor system operational" via the suspension FlexRay to the Mercedes-Benz Intelligent Drive 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 to be located in the detection area (this object is used as a reference value). If a malfunction is established or if there are no objects in the detection area, the Active Brake Assist cannot be activated. The stereo multifunction camera sends the status via the suspension FlexRay to the Mercedes-Benz Intelligent Drive control unit.
Curve radius > 50 m
Electronic Stability Program (ESP®) not switched to passive mode
The Electronic Stability Program control unit sends the ESP® status over the suspension FlexRay to the Mercedes-Benz Intelligent Drive control unit.
No active ESP® intervention recognized (vehicle not in sliding movement):
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 Mercedes-Benz Intelligent Drive control unit.
Gear range "D" engaged (vehicle not in backward movement):
The fully integrated transmission control unit (transmission 722, 724, 725) transmits information about the selected gear range via the drive train CAN, the powertrain control unit and the chassis FlexRay to the Mercedes-Benz Intelligent Drive control unit.
Vehicle speed of v = 7 to 250 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 the respective signals to the Mercedes-Benz Intelligent Drive control unit via the suspension FlexRay.
Driver and front passenger belt buckle latched (if front passenger detected by seat recognition) and front passenger door closed

Active Brake Assist with intersection function, general points

The Active Brake Assist with intersection function assesses the traffic situation in front of the vehicle and continuously determines the risk potential for a rear-end collision or for a collision with a vehicle intersection its path. In critical accident situations Active Brake Assist with intersection function initiates appropriate measures geared towards avoiding a collision or - at the least - reducing the possible consequences of a collision. Furthermore, there is a distance warning function contained therein which advises the driver about a vehicle driving immediately ahead which is too close. An optical and acoustic warning is issued before any possible collisions with vehicles or stationary obstacles on the vehicle's own lane.

The Active Brake Assist with intersection function can also provide support in the case of possible collisions with intersection traffic at intersections. The pedestrian detection can prevent a collision with pedestrians or reduce the severity of the impact. If the driver does not actuate the brake hard enough in a hazardous situation, the situation-related brake servo assistance automatically increases the brake pressure to ensure effective emergency braking, if necessary up to emergency braking. The brake application which is metered according to the situation is also makes the greatest possible braking distance available for the traffic to the rear.

In a vehicle speed range of v = 7 up to 250 km/h, Active Brake Assist with intersection function is activated in a potentially hazardous situation. In the case of stationary obstacles, pedestrians and crossing vehicles, the Active Brake Assist with cross-traffic function is only activated if the vehicle's own speed is maximum approx. v = 100 km/h.

For pedestrians and crossing vehicles, the max. vehicle speed may be approx. 70 km/h. It is controlled by the Mercedes-Benz Intelligent Drive control unit which actively intervenes in the brake system.

The optical warning and the warning tones of the Active Brake Assist with cross-traffic function can be selected and set via the operating level in the head unit. For navigation in the operating menu the following options are available:

Except with code 446 (Touchpad only) it is possible to navigate with the audio/COMAND® control panel. The Audio/COMAND® control panel sends the corresponding control signals (except code 446 (Touchpad only)) to the head unit via the Telematics CAN.
With code 446 (Touchpad only) or code 448 (Touchpad), the navigation takes place with the Touchpad. The touchpad (with code 446 (Touchpad only)) or code 448 (Touchpad)) transmits the respective control signals via the Telematics CAN to the head unit.
The navigation can occur with code 531 (COMAND® APS) per voice control. The driver FSE microphone is directly read in by the head unit.
The navigation can occur over the head unit finger navigation pad and the "Back" button on the steering wheel. The head unit finger navigation pad and the "Back" button transmit the relevant control signals via the steering wheel electronics, the steering wheel CAN, the steering column tube module control unit, the suspension FlexRay, the electronic ignition lock control unit and the user interface CAN to the head unit.
The operating menu can be called up on the upper control panel control unit via the vehicle button. The upper control panel control unit transmits the status of the vehicle button via LCP-LIN, audio/COMAND® control panel (except code 446 (Touchpad only)) or touchpad (with code 446 (Touchpad only) or code 448 (Touchpad)) and Telemachus CAN to the head unit.

The head unit sends the status of the Active Brake Assist with cross-traffic function via the user interface CAN, electronic ignition lock control unit and the suspension FlexRay to the Mercedes-Benz Intelligent Drive control unit.

The driver can select the following operating modes:

Default
The standard operating mode is set in the as-delivered state. When the Active Brake Assist with intersection function is switched off, the operating mode Standard is automatically active after a renewed ignition cycle.
ADAPTIVE
The visual warning and warning tones are output later (dynamic warning), for sporty driving.
Sensitive
The visual warning via the DISTRONIC warning lamp (static distance warning) and the warning tones (collision-critical distance warning) take place in a more sensitive and earlier manner that in the standard operating mode.

Illustration of the principle of Active Brake Assist with intersection function with one stationary or significantly slower vehicle on one's own lane

Courtesy of MERCEDES-BENZ USA

After autonomous emergency braking up to vehicle standstill the vehicle remains stalled.

The Active Brake Assist with intersection function consists of the following subfunctions:

Function sequence for distance warning
Function sequence for brake force boosting
Function sequence for autonomous brake application
Function sequence for emergency braking in the case of pedestrians crossing in front of the vehicle
Function sequence for turn-off function
Function sequence for the traffic jam emergency braking function

Function sequence for distance warning

Detection ranges for radar sensor system/stereo multifunction camera, shown on model 205.0

Courtesy of MERCEDES-BENZ USA

The front short and long range radar sensor operates according to the pulse modulated Doppler radar concept, which enables the distances and speeds of individual objects (e. g. vehicles) to be measured independently of each other.

The short and long-range radar sensor sends corresponding information via the suspension FlexRay to the Mercedes-Benz Intelligent Drive control unit. The short and long-range radar sensor is heated by a radiation dome heater, which actuates it directly.

Persons and crossing objects are detected by the MFK stereo camera and the front and long range radar sensor.

The stereo multifunction camera is located in the upper area of the windshield and supplies the following data:

Relative position of an object and pedestrians crossing the driving lane corridor
Side closing speed
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 laterally 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 corresponding data via the the suspension FlexRay to the Mercedes-Benz Intelligent Drive control unit.

If objects in your lane (vehicle speed range of v = 7 to 250 km/h) or crossing objects and pedestrians (vehicle speed range of v = 7 up to 70 km/h) are detected by the radar sensor system or the stereo multifunction camera, the Mercedes-Benz Intelligent Drive control unit outputs a static or collision-critical distance warning.

Static distance warning (not for code 494 (USA version)):

Output of the static distance warning takes place purely optically.

In standard operating mode, the static distance warning is triggered (at a vehicle speed of v > 30 km/h) when the time interval between the vehicle and the vehicle ahead is less than t = 0.8 s (e. g. in moving traffic). The DISTRONIC warning lamp lights up in the IC.

The Mercedes-Benz Intelligent Drive control unit sends the corresponding request via the suspension 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, at a vehicle speed of v > 7 km/h to 250 km/h, a moving or stationary obstacle or, at a vehicle speed of v > 7 km/h to 70 km/h, a crossing obstacle in the detection range of the radar sensor system or stereo multifunction camera is classified as accident-critical, the DISTRONIC warning lamp lights up and the instrument cluster speaker also emits an intermittent warning tone.

The warning is switched off again automatically one the situation is no longer critical.

The Mercedes-Benz Intelligent Drive control unit sends the corresponding request to actuate the instrument cluster speaker via the suspension 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

Courtesy of MERCEDES-BENZ USA

This is shown inversely on the IC, i. e. the distance warning readiness indicator is hidden when the distance warning function is active. If the distance warning function is deactivated, the distance warning readiness indicator and the "OFF" lettering are shown.

Function sequence for brake force boosting

If the driver reacts to the collision-critical distance warning with maximum full-stop braking, the Brake Assist provides support for the best possible utilization of the braking distance to the obstacle. Brake force boosting is available in a vehicle speed range of v ≥ 7 km/h to 250 km/h.

Maximum full-stop braking is defined over the current vehicle deceleration and the change in wheel speed.

The change in the wheel speeds (deceleration of the vehicle) tells the Mercedes-Benz Intelligent Drive control unit that the driver wishes to brake. The Electronic Stability Program control unit reads in the signals from the RPM sensors directly and sends this information via the suspension FlexRay to the Mercedes-Benz Intelligent Drive control unit.

The Mercedes-Benz Intelligent Drive control unit uses the data from the short and long range radar sensor and the stereo multifunction camera, calculates the required braking torque and transmits the request via the suspension FlexRay to the Electronic Stability Program control unit which reacts by directly activating the traction system hydraulic unit.

If a collision is unavoidable, occupant protection measures are taken in addition to intervention by the brake system.

If actuation is discontinued or the intensity of brake pedal operation by the driver decreases significantly, the driver actuates the accelerator pedal or evades the collision, brake force boosting for driver brake application is reduced, and brake force boosting is canceled.

Brake force boosting can respond to stationary obstacles at a vehicle speed of approx. v = 100 km/h and to crossing obstacles at approx. v = 70 km/h.

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.

Additional function requirements for autonomous braking

Vehicle speed: approx. v = 7 to 250 km/h (with moving obstacles), approx. v = 7 to 100 km/h (with stationary obstacles) or approx. v = 7 to 70 km/h (with crossing obstacles)
Driver seat belt fastened

Function sequence for autonomous brake application

If the driver does not react to the collision-critical warning, the Active Brake Assist with intersection function initiates autonomous partial braking. To do this, the Mercedes-Benz Intelligent Drive control unit calculates the corresponding braking torque while taking account of the following driving dynamics input factors:

Speed difference relative to the vehicle or obstacle
Distance from vehicle or obstacle

The Mercedes-Benz Intelligent Drive control unit sends the corresponding request via the the suspension FlexRay to the Electronic Stability Program control unit which then directly actuates the traction system hydraulic unit.

Brake force boosting

Emergency braking is only triggered if the driver and the front passenger have their seat belts on.

Parallel to this the Electronic Stability Program control unit evaluates the currently requested braking torque and initiates appropriate measures for OCCUP.PROT.SYS, if necessary.

Additional function requirements for emergency braking in the case of pedestrians crossing in front of the vehicle

Vehicle speed: approx. v = 7 to 70 km/h
Driver seat belt fastened

Function sequence for emergency braking in the case of pedestrians crossing in front of the vehicle

If a crossing pedestrian is detected by the radar sensor system or by the MFK stereo the Mercedes-Benz Intelligent Drive control unit issues a static or collision-critical distance warning.

Details about this are described in "Function sequence for distance warning".

To optimally use the braking distance up to the obstacle, the driver is supported by the Active Brake Assist with cross-traffic function if he/she reacts to the collision-critical distance warning with an emergency braking.

Emergency braking is defined over the current vehicle deceleration and the change in wheel speed.

Speed differential to the pedestrian
Distance to the pedestrian

To optimally use the braking distance up to the obstacle, the situation-appropriate brake force boosting supports the driver if he/she reacts with a maximum full-stop braking.

Emergency braking is defined over the current vehicle deceleration and change.

Emergency braking is only triggered if the driver and the front passenger have their seat belts on.

Parallel to this the Electronic Stability Program control unit evaluates the currently requested braking torque and initiates appropriate measures for OCCUP.PROT.SYS, if necessary.

Additional function requirements for the turn-off function

Vehicle speed: up to 15 km/h
Driver seat belt fastened

Function sequence for turn-off function

If the radar sensor system or stereo multifunction camera detect the potential for a collision with an oncoming vehicle when the driver is attempting to turn off across the oncoming lane, autonomous braking can be initiated before the vehicle leaves its lane. The Mercedes-Benz Intelligent Drive control unit calculates the respective braking torque while taking account of driving dynamics input factors and sends the corresponding request via the the suspension FlexRay to the Electronic Stability Program control unit which then directly actuates the traction system hydraulic unit.

Additional function requirements for the traffic jam emergency braking function

Vehicle speed: approx. v = 7 to 30 km/h
Driver seat belt fastened

Function sequence for the traffic jam emergency braking function

If the radar sensor system and the stereo multifunction camera detect a traffic jam scenario without any option to avoid it (e. g. due to vehicles on the neighboring lanes or due to guardrails), the Mercedes-Benz Intelligent Drive control unit issues a static or collision-critical distance warning.

Details about this are described in "Function sequence for distance warning".

Furthermore the Active Brake Assistant with intersection function initiates early emergency braking. The Mercedes-Benz Intelligent Drive control unit calculates the respective braking torque while taking account of driving dynamics input factors and sends the corresponding request via the the suspension FlexRay to the Electronic Stability Program control unit which then directly actuates the traction system hydraulic unit.

Parallel to this the Electronic Stability Program control unit evaluates the currently requested braking torque and initiates appropriate measures for OCCUP.PROT.SYS, if necessary.

	Electrical function schematic of Active Brake Assist with cross-traffic function		PE30.30-P-2073-97FBA
	Overview of system components for driver assistance systems		GF54.00-P-9998RFM