Blind Spot Assist, function - GF54.71-P-0003CE
MODEL 204.0/2 as of model year 2012 with CODE 234 (Blind Spot Assist) without CODE 237 (Active Blind Spot Assist)
MODEL 204.0/2 as of model year 2012 with CODE 237 (Active Blind Spot Assist) without CODE 234 (Blind Spot Assist)
MODEL 204.3 with CODE 234 (Blind Spot Assist) without CODE 237 (Active Blind Spot Assist)
MODEL 204.3 with CODE 237 (Active Blind Spot Assist) without CODE 234 (Blind Spot Assist)
MODEL 204.9 as of model year 2013 with CODE 234 (Blind Spot Assist) without CODE 237 (Active Blind Spot Assist)
MODEL 204.9 as of model year 2013 with CODE 237 (Active Blind Spot Assist) without CODE 234 (Blind Spot Assist)
With code (234) Blind Spot Assist
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 (with code (509) Navigation box) inserted in cradle for navigation module (with code (508) Navigation box preinstallation or code (509) Navigation box)
- Radar sensor system not switched off
- Engine running or drivetrain operational
- Vehicle moving forward
- Vehicle speed v30 km/h
- No trailer operation (with code (550) Trailer hitch)
Blind Spot Assist, general
The Blind Spot Assist monitors the rear and side area of the vehicle using short range radar and, if necessary, informs the driver that an intentional lane change (turn signal set) is not recommended at a given point in time. In the wider sense, the Blind Spot Assist serves as an extension of the rearview mirror; under no circumstances is the driver relieved of his/her responsibility of safely carrying out the lane change. 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.
The visual warning is issued via the Blind Spot Assist readiness and warning indicator in the respective outside mirror.
The acoustic warning is output via the warning buzzer in the instrument cluster.
The front SAM control unit forms the central interface (gateway) for data exchange between the connected control units over the various CAN buses.
A distinction is currently made between the following Blind Spot Assist variants:
- Blind Spot Assist (for code (234) Blind Spot Assist)
- Active Blind Spot Assist (with code (237) Active Blind Spot Assist)
Blind Spot Assist:
The area which cannot be observed on the outside mirror and inside rearview mirror (A67) is monitored by the following components:
- Left rear bumper intelligent radar sensor
- Right rear bumper intelligent radar sensor
All relevant data is evaluated by the rear bumper intelligent radar sensors, whereby the right rear bumper intelligent radar sensor requests the warning output.
The rear bumper intelligent 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 intelligent radar sensor. This means that the left rear bumper intelligent radar sensor sends its requests to issue warning and standby messages to the right rear bumper intelligent radar sensor via the front end CAN. This sensor evaluates the information from both rear bumper radar sensors and sends corresponding requests via the front-end CAN, front SAM control unit and interior CAN to the corresponding front door control unit and to the instrument cluster.
Active Blind Spot Assist:
Active Blind Spot Assist builds upon the functionality of Blind Spot Assist. The Active Blind Spot Assist can additionally perform brake interventions to correct the course, taking the surroundings of the vehicle with Blind Spot Assist into account. The active interventions by the brake system are performed on specific wheels and have a course-correcting effect.
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 rearview mirror is monitored by the following components:
- Left rear bumper radar sensor
- Right rear bumper radar sensor
The course-correcting intervention requires the road space in front of the vehicle to be monitored to avoid any collisions with other road users caused by any change in direction.
Monitoring of the road in front of the vehicle is performed 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 send the corresponding data over the sensor CAN to the video and radar sensor system control unit. The DISTRONIC electric controller unit sends the corresponding data via the vehicle dynamics CAN to the video and radar sensors control unit. All relevant data are evaluated by the video and radar sensor system control unit.
Illustration of the principle of Blind Spot Assist; illustration shows model 204.0
The following information is read in by the rear bumper intelligent radar sensors (with code (234) Blind Spot Assist) or by the video and radar sensor system control unit (with code (237) Active Blind Spot Assist):
- Terminal status of terminal 15
- "Blind Spot Assist" function status (function requirement)
- "Engine running" or "Drivetrain operational" signal (function requirement)
- Vehicle moving forward (function requirement)
- Vehicle speed (function requirements)
- Gear range status (with code (237) Active Blind Spot Assist)
- Trailer recognition (with code (550) trailer hitch)
- Status of yawing moment interface (with code (237) Active Blind Spot Assist)
- Status of service brake (with code (237) Active Blind Spot Assist)
Status of circuit 15:
The electronic ignition lock control unit sends the status of circuit 15 via the chassis CAN, front SAM control unit and front end CAN to the rear bumper intelligent radar sensors or via the chassis CAN to the video and radar sensor system control unit.
Status of "Blind Spot Assist" status:
The instrument cluster sends the status of the "Blind Spot Assist" function (on or off) via the chassis CAN, front SAM control unit and front end CAN to the rear bumper radar sensors or via the chassis CAN to the video and radar sensor system control unit.
"Engine running" or "drivetrain operational" signal:
The CDI control unit or the ME-SFI control unit sends the "Engine running" or "Drivetrain operational" signal via the chassis CAN, front SAM control unit and front-end CAN to the rear bumper intelligent radar sensors or via the chassis CAN to the video and radar sensor system control unit.
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 directions and the wheel speeds are recorded by rpm sensors and their signals are read in directly by the Electronic Stability Program control unit.
The Electronic Stability Program control unit sends the signals from the rpm sensors via the chassis CAN, front SAM control unit and front end CAN to the rear bumper intelligent radar sensors or via the chassis CAN to the video and radar sensor system control unit.
The wheel rotation direction is determined dependent on the drive version. Detailed information on the function can be found in the separate description "Adaptive Brake (ABR), function".
Gear range status (with code (237) Active Blind Spot Assist):
On vehicles with code (237) Active Blind Spot Assist, the electronic transmission control control unit (with transmission 722.6) or the fully integrated transmission control unit (with transmission 722.9) sends the gear range via the drive train CAN, CDI control unit or ME-SFI control unit and chassis CAN to the video and radar sensor system control unit.
Trailer recognition (with code (550) Trailer hitch):
The trailer recognition control unit sends trailer recognition information via the interior CAN, front SAM control unit and front end CAN to the rear bumper intelligent radar sensors or via the chassis CAN to the video and radar sensor system control unit.
Status of service brake, status of yawing moment interface (with code (237) Active Blind Spot Assist):
The Electronic Stability Program control unit send the status of the service brake and the yawing moment interface via the chassis CAN to the video and radar sensor system control unit.
The Blind Spot Assist system includes the following subfunctions:
- Measuring procedure function sequence
- Function sequence for displaying system and warning messages
- Function sequence for active intervention by the brake system (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 waves hit a vehicle, they are reflected by it and are received again by the corresponding radar sensor as a secondary signal. 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-wideband 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 (model 204.0/2/3 up to 30.11.12, model 204.9 up to 31.5.13) or f = 25 GHz (model 204.0/2/3 as of 1.12.12, model 204.9 as of 1.6.13)
- Mode of operation: short pulse method with f = 5 GHz bandwidth (model 204.0/2/3 up to 30.11.12, model 204.9 up to 31.5.13) or f = 1.4 GHz bandwidth (model 204.0/2/3 as of 1.12.12, model 204.9 as of 1.6.13)
The 24 GHz radar sensor system is deactivated automatically in countries where it is not approved.
The range up to max. s = 200 m in front of the vehicle is monitored on vehicles with code (237) Active Blind Spot Assist by the DISTRONIC electric controller unit (long range radar). The design of the travel distance for the monitoring range is variable and matched to the vehicle speed. The DISTRONIC electric controller unit sends the corresponding data via the vehicle dynamics CAN to the video and radar sensors control unit.
Detection range of radar sensor system with code (234) Blind Spot Assist; illustration shows model 204.0
The rear radar sensor system coverage area is based on the angles of the radar waves. They are extrapolated by the respective rear bumper intelligent 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; illustration shows model 204.0
The detection ranges of the rear and front intelligent radar sensor systems are based on the angle at which the radar waves are emitted. These are extrapolated by the video and radar sensor system control unit to calculate the actual monitoring ranges.
Depiction of actual rear monitoring range (with code (234) Blind Spot Assist or code (237) Active Blind Spot Assist); illustration shows model 204.0
Automatic shutoff of radar sensor system (model 204.0/2/3 up to 30.11.12, model 204.9 up to 31.5.13):
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 protected areas around radio astronomy stations are stored in the respective rear bumper intelligent radar sensor or in the video and radar sensor system control unit. The radio (with code (523) MB Audio 20 radio or code (510) Audio 20 with CD changer) in combination with the adapted navigation module, or the COMAND controller unit (with code (512) COMAND APS incl. DVD changer or code (527) COMAND APS with single DVD drive (with navigation)) receives global positioning system (GPS) signals via the multifunction antenna. Ultimately the radio or the COMAND controller unit sends the GPS coordinates over the interior CAN.
Vehicles with code (234) Blind Spot Assist:
The rear bumper intelligent radar sensors receive the GPS coordinates via the front end CAN. To this end, the front SAM control unit sends this data via the front end CAN to the rear bumper intelligent radar sensors. The rear bumper radar sensors then switch off the integrated radar sensor system.
Vehicles with code (237) Active Blind Spot Assist:
The video and radar sensor system control unit receives the GPS coordinates via the chassis CAN. To this end, the front SAM control unit sends the data over the chassis CAN to the video and radar sensor system control unit. The video and radar sensor system control unit then sends the "Shutoff radar sensor system" request over the sensor CAN to all the radar sensors. The radar sensor system is then shutoff.
With Blind Spot Assist active, the message "Radar sensor system automatically switched off, see operator's manual" is shown on the multifunction display of the instrument cluster. The Blind Spot Assist readiness and warning indicators light up in 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. If the vehicle leaves the restricted area, the radar sensor system is automatically switched on again. The "radar sensor system automatically switched off, see operator's manual" message is canceled and the yellow Blind Spot Assist ready and warning indicators are switched off at vehicle speeds of v > 30 km/h. On model 204.0/2/3 as of 1.12.12, model 204.9 as of 1.6.13, the radar sensor system is no longer deactivated automatically. Use of the reduced frequency band range from f = 24.25 GHz to 25.65 GHz means that this is no longer necessary. Both the NATO band and the radio astronomy band are blanked 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 on/off of the radar sensor system:
The "Vehicle" menu in the instrument cluster enables the short-range radar sensor system to be manually switched off and on again. 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 displaying system and warning messages
When circuit 15 is switched on, the Blind Spot Assist readiness and warning indicators are switched on for t = 1.5 s turning first red then yellow. When a speed of v > 30 km/h is reached the Blind Spot Assist readiness and warning indicators are switched off and the Blind Spot Assist is ready for warning.
If a function error is detected, a corresponding message is shown on the multifunction display of the instrument cluster and the Blind Spot Assist readiness and warning indicators light up yellow. The status of functional readiness is sent by the rear bumper intelligent radar sensors or the video and radar sensor system control unit. The request to issue fault messages is sent by the rear bumper intelligent radar sensors or the video and radar sensor system control unit. The Blind Spot Assist readiness and warning indicators are actuated by the corresponding front door control unit.
Vehicles with code (234) Blind Spot Assist:
The rear bumper intelligent radar sensors send the functional readiness status via the front end CAN, front SAM control unit and interior CAN to the corresponding front door control unit. The request to issue fault messages is sent by the right rear bumper intelligent radar sensor as the master via the front end CAN, front SAM control unit and interior CAN to the corresponding front door control unit and via the front end CAN, front SAM control unit and chassis CAN to the instrument cluster.
Vehicles with code (237) Active Blind Spot Assist:
The video and radar sensor system control unit sends the functional readiness status and the request to issue fault messages via the chassis CAN, front SAM control unit and interior CAN to the corresponding front door control unit and via the chassis CAN to the instrument cluster.
If, at a speed of v ≥30 km/h, a vehicle is located in the radar sensor system sensing range, the driver is notified of it by the Blind Spot Assist readiness and warning indicator turning read in the outside mirror on the side of the vehicle on 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 readiness and warning lamp lighting up, the driver still attempts to change lane and indicates this by operating the combination switch (operates turn signal), a one-time double-warning tone is also issued by the instrument cluster's warning buzzer. The Blind Spot Assist readiness and warning indicator flashes on and off. If the vehicle leaves the radar sensor system's sensing range, the red flashing Blind Spot Assist readiness and warning indicator is switched off.
The signal curve for issuing warning messages corresponds to the signal curve for displaying functional readiness.
The steering column tube module control unit reads in the switch position of the combination switch directly and sends the position via the chassis CAN, front SAM control unit and front end CAN to the rear bumper intelligent radar sensors or via the chassis CAN to the video and radar sensor system control unit.
Blind Spot Assist readiness indicator shown on the left side of the vehicle
Blind Spot Assist warning indicator shown on the left side of the vehicle
The requirements for displaying functional readiness and for issuing visual warning messages are listed in the following table.
| Operating state | Blind Spot Assist readiness and warning indicator off | Blind Spot Assist readiness and warning indicator, yellow on | Blind Spot Assist readiness and warning indicator, red on | Blind Spot Assist readiness and warning indicator, flashing red |
|---|---|---|---|---|
| Circuit 15 OFF | X | |||
| Circuit 15 ON (t < 1.5 s) | X | |||
| Circuit 15 ON (t > 1.5 s) | X | |||
| Engine running or drivetrain operational | X | |||
| Vehicle accelerates, vehicle speed v ≥30 km/h 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 | |||
| Flasher set, vehicle recognized in blind spot | X | |||
| Active course-correcting intervention by the brake system (with code (237) Active Blind Spot Assist) | X | |||
| Radar sensor system automatically shut down (model 204.0/2/3 up to 30.11.12, model 204.9 up to 31.5.13) | X | |||
| Fault in Blind Spot Assist system | X |
Additional function requirements for active intervention by the brake system (with code (237) Active Blind Spot Assist)
- Electronic Stability Program (ESP ®) not passively switched (except model 204.077/277/377) or
- ESP® not switched to "SPORT HANDLING MODE" (model 204.077/277/377)
- ESP ® not in active diagnostic or roller dynamometer mode
- Anti-lock braking system (ABS), acceleration skid control (ASR), Brake Assist System (BAS), ESP, PRE-SAFE brake inactive
- Vehicle speed v < 200 km/h
- Approval issued for active intervention by the brake system for yawing moment interface
The status information for the driving assistance and driving safety systems ABS, ASR, BAS, ESP ® and PRE-SAFE brake as well as for the yawing moment interface is sent by the Electronic Stability Program control unit via the chassis CAN to the video and radar sensor system control unit.
Function sequence for active intervention by the brake system (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, a 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 interventions by the brake system are always suppressed, when one of the following conditions occurs:
- Rapid or greater loss of pressure in a tire
Information on the tire pressure monitoring system can be found in the separate description "Tire pressure monitor, function" (with code (470) Tire pressure monitor (standard) or code (475) Tire pressure monitor (premium)) or "Tire pressure loss warning, function" (with code (477) Tire pressure loss warning).
- 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 to 6 m/s 2
The acceleration forces are recorded by the yaw rate sensor for lateral and longitudinal acceleration. This sends the information over the dynamics CAN to the video and radar sensor system control unit.
- Jerky steering motion 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 steering angle sensor data directly and sends the data over the chassis CAN to the video and radar sensor system control unit.
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.
Shows model 204.0
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.
Shows model 204.0
If an obstacle (8) is located on one side of a vehicle with Blind Spot Assist (1), course-correcting intervention by the brake system in the direction of the obstacle (8) is suppressed.
Shows model 204.0
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!
Shows model 204.0
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!
Shows model 204.0
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 204.0/2 as of model year 2012 with CODE 234 (Blind Spot Assist) without CODE 237 (Active Blind Spot Assist) MODEL 204.3 with CODE 234 (Blind Spot Assist) without CODE 237 (Active Blind Spot Assist) MODEL 204.9 as of model year 2013 with CODE 234 (Blind Spot Assist) without CODE 237 (Active Blind Spot Assist) | PE54.71-P-2051-97FAA | |
| MODEL 204.0/2 as of model year 2012 with CODE 237 (Active Blind Spot Assist) without CODE 234 (Blind Spot Assist) MODEL 204.3 with CODE 237 (Active Blind Spot Assist) without CODE 234 (Blind Spot Assist) MODEL 204.9 as of model year 2013 with CODE 237 (Active Blind Spot Assist) without CODE 234 (Blind Spot Assist) | PE54.71-P-2051-97FAB | ||
| Overview of system components for driver assistance systems | GF54.00-P-9998CE |