Blind Spot Assist, Function - GF54.71-P-0003FQ
MODEL 218
up to year 2015
with CODE 234 (Blind Spot Monitoring)
except CODE 237 (Active Blind Spot Assist)
with CODE 237 (Active Blind Spot Assist)
except CODE 234 (Blind Spot Monitoring)
Up to 28.02.2013 with CODE 234 (Blind Spot Assist)
As of 01.03.2013 with code 234 (Blind Spot Assist)
Up to 28.02.2013 with code 237 (Active Blind Spot Assist)
As of 01.03.2013 with code 237 (Active Blind Spot Assist)
Function requirements, general
- No undervoltage or overvoltage
- Function "Blind Spot Assist" in "Assistance" menu activated in instrument cluster
- Navigation module plugged in (with code 508 (Navigation box preinstallation) or code 509 (Navigation box))
- Radar sensor system not switched off
- Engine running or drive train operational
- Vehicle moving forward
- Vehicle speed: v ≥ 30 to 250 km/h
- No trailer operation (with CODE 550 (Trailer hitch))
Blind Spot Assist, general
The Blind Spot Assist monitors the rear and side areas of the vehicle using short range radar and, if necessary, informs the driver that an intentional lane change (turn signal active) is not recommended at this time. In a broader sense, the Blind Spot Assist acts as an extension of the outside mirrors. It does not release the driver of his/her obligation to perform lane changes safely on his/her own responsibility. In the respective outside mirror, a visual indicator indicates the status of the Blind Spot Assist and warns of critical situations during a lane change (i.e. a vehicle is in the "blind spot"). In addition, an acoustic warning can also be given.
Visual warnings are issued via the respective Blind Spot Assist warning lamp.
The acoustic warning is output via the warning buzzer in the instrument cluster.
The front SAM control unit is the central interface for data exchange between the connected control units via the various CAN bus systems (gateway).
A distinction is currently made between the following Blind Spot Assist variants:
- Blind Spot Assist (with CODE 234 (Blind Spot Assist))
- Active Blind Spot Assist (with CODE 237 (Active Blind Spot Assist))
Blind Spot Assist (with code 234 (Blind Spot Assist)):
The area which cannot be observed via the outside mirror and inside rear-view mirror is monitored by the following components:
- Left rear bumper radar sensor
- Right rear bumper radar sensor
All relevant data are evaluated by the intelligent radar sensors, whereby the right intelligent radar sensor request the warning output.
The rear bumper radar sensors operate according to the "master-slave" principle. The master or slave function can be determined via the connector coding. The master function is defined for the right rear bumper radar sensor. This means that the left rear bumper radar sensor sends its requests to issue warning and readiness messages via the front-end CAN (up to 28.02.2013) or chassis CAN 1 (as of 01.03.2013) to the right rear bumper radar sensor, which then evaluates the information from both rear bumper radar sensors and sends corresponding requests to the relevant control units via the front-end CAN (up to 28.02.2013) or chassis CAN 1 (as of 01.03.2013).
Active Blind Spot Assist (with code 237 (Active Blind Spot Assist)):
Active Blind Spot Assist builds upon the functionality of Blind Spot Assist.
Active Blind Spot Assist can additionally perform brake system interventions to correct the course, taking the surroundings of the vehicle into account. Active brake application occurs at specific wheels. If a risk of collision is detected with vehicles that are in the blind spot, then an accident can be avoided or the consequences of the accident lessened.
The area which cannot be observed via the outside mirror and inside rear-view mirror is monitored by the following components:
- Left rear bumper radar sensor
- Right rear bumper radar sensor
Course-correcting brake application requires the road space in front of the vehicle to be monitored in order to avoid collisions with other road users (incl. oncoming traffic) as a result of a possible change in direction.
The area in front of the vehicle is monitored by the following components:
- DISTRONIC electric controller unit
- DISTRONIC sensor (DTR)/left front bumper
- DISTRONIC sensor (DTR)/right front bumper
The front bumper DISTRONIC (DTR) sensors and the rear bumper radar sensors communicate with the video and radar sensor system control unit via the sensor CAN.
The DISTRONIC PLUS controller unit communicates via the vehicle dynamics CAN with the video and radar sensor system control unit.
All relevant data are evaluated by the video and radar sensor system control unit.
Illustration of the Blind Spot Assist principle
The following information is evaluated by the Blind Spot Assist:
- Status of function "Blind Spot Assist"
- Engine running or drive train operational
- Vehicle moving forward
- Vehicle speed
- Trailer recognition (with CODE 550 (Trailer hitch))
- Status of drive range (with code 237 (Active Blind Spot Assist))
- Status of service brake (with code 237 (Active Blind Spot Assist)
Status of "Blind Spot Assist" status:
The instrument cluster sends the status of the "Blind Spot Assist" function (switched on or switched off) via the chassis CAN (up to 28.02.2013) or chassis CAN 2 (as of 01.03.2013).
Engine running or drive train operational:
The CDI control unit or the ME-SFI control unit sends the "Engine running" or "Drivetrain operational" signal via the chassis CAN (up to 28.02.2013) or chassis CAN 1 (as of 01.03.2013).
Vehicle in forward movement, vehicle speed:
Forward movement is defined via the wheel rotation direction. The vehicle speed is calculated on the basis of the wheel speeds. The wheel rotation directions and the wheel speeds are recorded by the RPM sensors. The Electronic Stability Program control unit reads in the signals from the RPM sensors directly and sends them via the chassis CAN (up to 28.02.2013) or chassis CAN 1 (as of 01.03.2013).
Trailer recognition (with CODE 550 (Trailer hitch)):
The trailer recognition control unit sends the information "Trailer recognized" via the interior CAN, front SAM control unit and chassis CAN (up to 28.02.2013) or chassis CAN 1 (as of 01.03.2013).
Status of drive range (with code 237 (Active Blind Spot Assist)):
The fully integrated transmission control unit sends the status of the drive range via the drive CAN, CDI control unit or ME-SFI control unit and chassis CAN (up to 28.02.2013) or chassis CAN 1 (as of 01.03.2013).
Status of service brake (with code 237 (Active Blind Spot Assist)):
The Electronic Stability Program control unit sends the status of the service brake via the chassis CAN (up to 28.02.2013) or chassis CAN 1 (as of 01.03.2013).
Blind Spot Assist (with code 234 (Blind Spot Assist)):
The rear bumper radar sensors read in all relevant information via the front-end CAN (up to 28.02.2013) or chassis CAN 1 (as of 01.03.2013).
Relevant information from control units which are not connected to any of these CANs is forwarded by the front SAM control unit (gateway).
Active Blind Spot Assist (with code 237 (Active Blind Spot Assist)):
The video and radar sensor system control unit reads in all relevant information via the chassis CAN (up to 28.02.2013) or chassis CAN 1 (as of 01.03.2013) and evaluates it. Relevant information from control units which are not connected to any of these CANs is forwarded by the front SAM control unit (gateway).
The Blind Spot Assist system includes the following subfunctions:
- Measuring procedure function sequence
- Function sequence for system and warning messages
- Function sequence for active brake application (with code 237 (Active Blind Spot Assist))
Measuring procedure function sequence
The vehicles are recorded based on the radar measuring method.
Electromagnetic waves are bundled and sent out as so-called primary signals here by the short and long range radar sensors. If these meet a vehicle, they are reflected by it and received again by the corresponding radar sensor as secondary signals. These signals are used to calculate the distance and the speed of the detected object as well as its angle relative to the vehicle.
The short-range radar sensors are ultra-wide band radar sensors with the following properties:
- Acquisition range s = 0.18 to 30 m
- Detection angle of ∠ = 60° with angle measurement and ∠ = 130° with detection only
- Carrier frequency: f = 24 GHz (up to 28.02.2013) or f = 25 GHz (as of 01.03.2013)
- Operating principle: Short-pulse method with f = 5 GHz bandwidth (up to 28.02.2013) or f = 1.4 GHz bandwidth (as of 01.03.2013)
This is switched off automatically in countries in which the 24 GHz radar sensor system is not approved.
For vehicles with CODE 237 (Active Blind Spot Assist) the range up to maximum s = 200 m in front of the vehicle is monitored by the DISTRONIC (long range radar) controller unit.
The monitoring range distance is flexibly configured and is regulated to match the vehicle speed. The DISTRONIC controller unit sends the corresponding information to the video and radar sensor system control unit via the vehicle dynamics CAN.
Detection range of radar sensor system with code 234 (Blind Spot Assist), shown on model 218.3
The detection range of the rear bumper radar sensors is based on the angle of reflection of the radar waves. These are extrapolated by the respective rear bumper radar sensor to produce the actual monitoring ranges.
Detection range of radar sensor system incl. front road space monitoring with code 237 (Active Blind Spot Assist), shown on model 218.3
The rear and front radar sensor system coverage areas are based on the angles of the radar waves These are extrapolated by the video and radar sensor system control unit to calculate the actual monitoring ranges.
Display of actual rear monitoring range (with code 234 (Blind Spot Assist) or code 237 (Active Blind Spot Assist)) shown on model 218 3
Automatic deactivation of radar sensor system (up to 28.02.2013):
Due to legal requirements on the 24 GHz radar system (short range radar) in Western Europe, the short range radar sensor system is automatically switched off in certain protected areas around radio astronomy stations. In other words the Blind Spot Assist is not functional in these ranges. The restricted areas around radio astronomy stations are stored in each rear bumper radar sensor or video and radar sensor system control unit. The radio in combination with the adapted navigation module or the radio with Auto Pilot System or the COMAND controller unit receives global positioning system (GPS) signals via the multifunction antenna.
The radio or the COMAND controller unit sends the GPS signals via the interior CAN, front SAM control unit and front-end CAN or chassis CAN.
On vehicles with code 234 (Blind Spot Assist), the rear bumper radar sensors receive the GPS signals via the front-end CAN and switch off the integrated radar sensor system.
On vehicles with code 237 (Active Blind Spot Assist), the video and radar sensor system control unit receives the GPS signals via the chassis CAN and sends the "Switch off short-range radar sensor system" request via the sensor CAN to the radar sensors, which then switch off the radar sensor system.
If the Blind Spot Assist is active, the message "Radar sensor system automatically deactivated, see operator's manual" is shown in the multifunction display of the instrument cluster. The warning lamps for Blind Spot Assist light up yellow.
If the vehicle is parked in a restricted area, then when it is started up again the GPS coordinates are used for position finding. The driver is notified again that the radar sensor system was automatically switched off. When the vehicle leaves the protected area, the short-range radar sensor system is switched on again automatically. The "Radar sensor system automatically switched off, see operator's manual" message is canceled and the yellow Blind Spot Assist warning lamps are switched off at vehicle speeds of v > 30 km/h.
As of 01.03.2013, the radar sensor system will no longer be automatically deactivated. Use of the reduced frequency band range means that this is no longer necessary. Both the NATO band and the radio astronomy band are left out. Operation of the radar sensor system within the restricted areas of the radio astronomy stations is thereby rendered possible. Consequentially, localization of the vehicle through GPS is no longer required.
Manual switching off and on of radar sensor system: There is also the possibility of switching the short-range radar sensor system off and on again manually via the "Vehicle" menu in the instrument cluster. If the radar sensor system was automatically switched off within a restricted area, the manual switch-on option is no longer available and the following message is shown "Radar sensor system automatically switched off, see operator's manual".
Function sequence for system and warning messages
When circuit 15 is switched on the Blind Spot Assist warning lamps light up red for t = 1.5 s and then yellow. When a vehicle speed of v > 30 km/h is reached, the Blind Spot Assist warning lamps go out again and the Blind Spot Assist is ready to issue warnings.
On vehicles up to 28.02.2013, the electronic ignition lock control unit sends the status of circuit 15 to the rear bumper radar sensors via the chassis CAN, front SAM control unit and front-end CAN or to the video and radar sensor system control unit via the chassis CAN. On vehicles as of 01.03.2013, the electronic ignition lock control unit sends the status of circuit 15 to the rear bumper radar sensors or to the video and radar sensor system control unit via chassis CAN 1.
If function errors are found, a corresponding message appears on the multifunction display of the instrument cluster, and the Blind Spot Assist warning lamps light up yellow. The status of functional readiness is sent by the rear bumper radar sensors or the video and radar sensor system control unit. The request to issue fault messages is sent by the rear bumper radar sensors or the video and radar sensor system control unit.
The Blind Spot Assist warning lamps are actuated by the corresponding front door control unit.
Blind Spot Assist (with code 234 (Blind Spot Assist)):
The rear bumper radar sensors send the functional readiness status to the corresponding front door control unit via the front-end CAN (up to 28.02.2013) or chassis CAN 1 (as of 01.03.2013), front SAM control unit and interior CAN. The right rear bumper radar sensor as the master sends the requests to issue warning and fault messages to the corresponding front door control unit via the front-end CAN (up to 28.02.2013) or chassis CAN 1 (as of 01.03.2013), front SAM control unit and interior CAN and to the instrument cluster via the front-end CAN (up to 28.02.2013) or chassis CAN 1 (as of 01.03.2013), front SAM control unit and chassis CAN (up to 28.02.2013) or chassis CAN 1 (as of 01.03.2013).
Active Blind Spot Assist (with code 237 (Active Blind Spot Assist)):
The video and radar sensor system control unit sends the functional readiness status or the requests to issue warning and fault messages to the corresponding front door control unit via the chassis CAN (up to 28.02.2013) or chassis CAN 1 (as of 01.03.2013), front SAM control unit and interior CAN.
The video and radar sensor system control unit additionally sends requests to issue warning and fault messages to the instrument cluster via the chassis CAN (on vehicles up to 28.02.2013) or via chassis CAN 1 (on vehicles as of 01.03.2013), front SAM control unit and chassis CAN 2.
If at a speed of v ≥ 30 km/h a vehicle is located in the acquisition range of the radar sensor system, the driver is warned by the warning lamp for Blind Spot Assist lighting up red in the in outside mirror, on the side of which the vehicle is in the blind spot. Overtaking vehicles are reliably detected up to a relative speed of v = 35 km/h. Vehicles with a higher relative speed may-under certain circumstances - be detected too late or not at all. If, despite the Blind Spot Assist warning lamps lighting up, the driver still attempts to change lane and indicates this by operating the combination switch (activation of turn signal indicator), a double warning tone is also issued by the instrument cluster's warning buzzer. The corresponding Blind Spot Assist warning lamp flashes. If the vehicle leaves the acquisition range of the radar sensor system, the red flashing Blind Spot Assist warning lamp is switched off.
The signal path for issuing the warning corresponds to that for displaying functional readiness.
Blind Spot Assist (with code 234 (Blind Spot Assist)):
The steering column tube module control unit reads in the switch position of the combination switch directly and sends this to the rear bumper radar sensors via the chassis CAN, front SAM control unit and front-end CAN on vehicles up to 28.02.2013 or via chassis CAN 1 on vehicles as of 01.03.2013.
Active Blind Spot Assist (with code 237 (Active Blind Spot Assist)):
The steering column tube module control unit sends the switch position of the combination switch to the video and radar sensor system control unit via the chassis CAN (up to 28.02.2013) or chassis CAN 1 (as of 01.03.2013).
Blind Spot Assist readiness
Blind Spot Assist warning
The following table contains the requirements for displaying system readiness and for showing the visual warning messages:
| Operating state | Blind spot assist warning lamp | |||
|---|---|---|---|---|
| Off | Lights up yellow | Lights up red | Flashes red | |
| Circuit 15 OFF | x | |||
| Circuit 15 ON (t < 1.5 s) | x | |||
| Circuit 15 ON (t > 1.5 s) | x | |||
| Engine running or drive train operational | x | |||
| Vehicle accelerates, vehicle speed v ≥ 30 to 250 km/h | x | |||
| Vehicle speed v > 250 km/h | x | |||
| Vehicle decelerates, vehicle speed v ≤ 25 km/h | x | |||
| Trailer recognized (with CODE 550 (Trailer hitch)) | x | |||
| Vehicle recognized in blind spot | x | |||
| Turn signal active, vehicle detected in blind spot | x | |||
| Course-correcting brake application active (with code 237 (Active Blind Spot Assist)) | x | |||
| Radar sensor system switched off automatically | x | |||
| Fault in Blind Spot Assist system | x | |||
Additional function requirements for active brake application (with code 237 (Active Blind Spot Assist))
- Electronic Stability Program (ESP®) not passively switched (except with engine 157) or ESP® not switched into "SPORT HANDLING MODE" (for engine 157)
- ESP® not in active diagnostic or roller dynamometer mode
- Anti-lock braking system (ABS), anti-slip control (ASR), Brake Assist System (BAS), ESP®, PRE-SAFE® brake inactive
- Vehicle speed v < 200 km/h (v < 120 mph)
- No active control intervention function in brake assistance systems
- Approval issued for active intervention by the brake system for yawing moment interface
The yawing moment interface is integrated in the Electronic Stability Program control unit and internally issues a signal to enable a course-correcting braking torque.
Function sequence for active brake application (with code 237 (Active Blind Spot Assist))
If the video and radar sensor system control unit detects the threat of an imminent side collision with a vehicle during a lane change, it requests course-correcting intervention by the brake system. The video and radar sensor system control unit sends this request over the vehicle dynamics CAN to the Electronic Stability Program control unit which then implements this request accordingly by directly actuating the traction system hydraulic unit. The Electronic Stability Program control unit selectively brakes individual wheels and moves the vehicle back onto a collision-free course.
If the driver countersteers against the intervention by the brake system (overrides the intervention by the brake system) or accelerates the vehicle, the intervention by the brake system is immediately canceled. The driver assistance or driving-safety systems ABS, ASR, BAS, ESP® and PRE-SAFE® brakes are of a higher priority than the Active Blind Spot Assist. Active control intervention functions from these systems result in cancellation of the active intervention by the brake system.
If the ABS system is actively intervening, an Active Blind Spot Assist intervention by the brake system is not initiated. During such an intervention by the brake system, the ABS may reduce the intensity of the intervention by the brake system, the intervention by the brake system itself however is continued with.
Course-correcting brake application is always suppressed if one of the following situations occurs:
- Rapid or greater loss of pressure in a tire
- Risk of frontal collision of vehicle with vehicle or obstacle in the direction of travel within t = 2.6 s (with constant movement conditions)
- Acceleration or deceleration of vehicle in longitudinal direction as well as lateral acceleration of a = 4 m/s2 to 6 m/s2 . The acceleration forces are recorded by the yaw rate sensor for lateral and longitudinal acceleration. This sends the corresponding information over the vehicle dynamics CAN to the video and radar sensor system control unit.
- Jerky steering movements by the driver with a steering wheel velocity > 300 °/s.
Steering movements are recorded by the steering angle sensor. The steering column tube module control unit reads in the data from the steering angle sensor directly and sends it to the video and radar sensor system control unit via the chassis CAN (up to 28.02.2013) or chassis CAN 1 (as of 01.03.2013).
The following graphics demonstrate situations in which course-correcting interventions by the brake system are suppressed.
If vehicles are in the blind spot (2) on both sides of a vehicle with Blind Spot Assist (1), a course-correcting intervention by the brake system is suppressed.
If an obstacle (8) whose position cannot be determined is located to the side of the vehicle with Blind Spot Assist (1), course-correcting brake intervention in the direction of the obstacle (8) is suppressed.
If a stationary obstacle (8) is located on one side of a vehicle (1) with Blind Spot Assist, course-correcting intervention by the brake system in the direction of the obstacle (8) is suppressed.
In the event of an imminent risk of collision with a preceding vehicle (10) and a vehicle in the blind spot (2) a course-correcting intervention by the brake system is suppressed.
An acoustic warning is not issued!
In the event of an imminent risk of collision with a stationary obstacle (8) and a vehicle in the blind spot (2) a course-correcting intervention by the brake system is suppressed.
An acoustic warning is not issued!
In the case of oncoming traffic, course-correcting intervention by the brake system is limited so that any collision with oncoming traffic is avoided.
| Electrical function schematic, blind spot assistant | Model 218 up to model year 2014 with code 234 (Blind Spot Monitoring) except code 237 (Active Blind Spot Assist) | PE54.71-P-2051-97XAA | |
| Electrical function schematic, blind spot assistant | Model 218 as of model year 2014 up to model year 2015 with code 234 (Blind Spot Monitoring) except code 237 (Active Blind Spot Assist) | PE54.71-P-2051-97XAC | |
| Electrical function schematic, blind spot assistant | Model 218 up to model year 2014 with code 237 (Active Blind Spot Assist) except code 234 (Blind Spot Monitoring) | PE54.71-P-2051-97XAB | |
| Electrical function schematic, blind spot assistant | Model 218 as of model year 2014 up to model year 2015 with code 237 (Active Blind Spot Assist) except code 234 (Blind Spot Monitoring) | PE54.71-P-2051-97XAD | |
| Overview of system components for driver assistance systems | GF54.00-P-9998FQ |