Blind Spot Assist, function - GF54.71-P-0003FL
MODEL 212.0/2 up to 28.2.13 with CODE (234) Blind Spot Assist
MODEL 212.0/2 up to 28.2.13 with CODE (237) Active Blind Spot Assist as of model year 2011 /AEJ 10
Blind Spot Assist function requirements, general
- No undervoltage or overvoltage
- Function of "Blind Spot Assist" in "Assist" menu activated in IC (A1)
- Radar sensor system not switched off
- Engine running or drivetrain 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 system monitors the rear and side areas of the systems vehicle using a 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 responsibility of safely carrying out the lane change as his own responsibility.
In the left outside mirror (M21/1) and in the right outside mirror (M21/2), a visual indicator indicates when the system is active and when a critical situation occurs during a lane change (i.e. a vehicle is in a "blind spot"). In addition, an acoustic warning can also be given.
The visual warning output takes place via the following components:
- Left Blind Spot Assist readiness and warning indicator (M21/1e2)
- Right Blind Spot Assist readiness and warning indicator (M21/2e2)
The acoustic warning is issued using the warning buzzer (A1h1) in the instrument cluster.
The front SAM control unit with fuse and relay module (N10/1) is the central interface for data exchange between the various CAN-bus systems (gateway).
A differentiation is currently made between the following Blind Spot Assist variants:
- Blind Spot Assist (up to 31.5.10) (with code (234) Blind Spot Assist)
- Blind Spot Assist (as of 1.6.10) (with code (234) Blind Spot Assist)
- Active Blind Spot Assist (with code (237) Active Blind Spot Assist)
Blind Spot Assist (up to 31.5.10):
The area which cannot be observed on the outside mirror and inside rearview mirror (A67) is monitored by the following components:
- Left rear bumper radar sensor (B29/6)
- Right rear bumper radar sensor (B29/7)
The signals of the left rear bumper radar sensor, and the signals of the right rear bumper radar sensor are sent over the sensor CAN (CAN S) to the radar sensors control unit (N62/1).
All relevant data are evaluated by the radar sensors control unit.
Blind Spot Assist (as of 1.6.10):
The area which cannot be observed via the outside mirror and inside rearview mirror is monitored by the following components:
- Intelligent radar sensor for left rear bumper (B29/4)
- Intelligent radar sensor for right rear bumper (B29/5)
All relevant data are evaluated by the intelligent radar sensors, whereby the right intelligent radar sensor request the warning output.
The 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 intelligent radar sensor. In other words, the left intelligent radar sensor sends its information over the front end CAN (CAN G) to the right intelligent radar sensor, which then evaluates the information from both wheel sensors and then forwards corresponding requests or data over the front end CAN to the relevant control units.
Active Blind Spot Assist:
Active Blind Spot Assist builds upon the functionality of Blind Spot Assist. Active Blind Spot Assist can additionally perform course-correcting brake system interventions taking the surroundings of the vehicle with the system into account.
Active interventions by the brake system are conducted on a wheel-specific basis and exert a course-correcting influence on the vehicle with the system.
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 is dependent on the road space in front of the vehicle being monitored to avoid any collisions with other road user (incl. oncoming traffic) because of any change in direction.
Monitoring of the road in front of the vehicle is performed by the following components:
- DISTRONIC electric controller unit (A89)
- Left front bumper DISTRONIC (DTR) sensor (B29/2)
- Right front bumper DISTRONIC (DTR) sensor (B29/3)
The signals of the front bumper DISTRONIC (DTR) sensors and the signals from the rear bumper radar sensors are sent to the video and radar sensor system control unit (N62/2) over the sensor CAN. The signals from the DISTRONIC electric controller unit are read in over the dynamics CAN (CAN H) from 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 drivetrain operational
- Vehicle moving forward
- Vehicle speed
- Trailer recognition status (with code (550) Trailer hitch)
- Status of shift stage (with code (237) Active Blind Spot Assist)
- Status of service brake (with code (237) Active Blind Spot Assist)
The status of the "Blind Spot Assist" function (switched on/off) is sent by the instrument cluster over the chassis CAN (CAN E).
The engine running or the drivetrain operational status is sent by the CDI control unit (N3/9) (for diesel engine) or the ME-SFI [ME] control unit (N3/10) (for gasoline engine) over the chassis CAN.
The status of the AHE is sent by the trailer recognition control unit (N28/1) over the interior CAN (CAN B), front SAM control unit, chassis CAN and front end CAN.
The forward movement is defined via the wheel rotation direction and the vehicle speed via the wheel speed.
The wheel rotation direction and wheel speed are recorded by the following sensors:
- Left front axle rpm sensor (L6/1)
- Right front axle rpm sensor (L6/2)
- Left rear axle rpm sensor (L6/3)
- Right rear axle rpm sensor (L6/4)
The rpm sensor signals are read in directly by the following control units on a model and equipment-specific basis and then sent by them over the chassis CAN:
- Electronic Stability Program control unit (N30/4) (with code (234) Blind Spot Assist, except model 212.074/077/095/098/274/277/298)
- Regenerative braking system control unit (N30/6) (model 212.095/098/298 with code (234) Blind Spot Assist or code (237) Active Blind Spot Assist)
- Premium Electronic Stability Program control unit (N30/7) (with code (237) Active Blind Spot Assist, except model 212.095/098/298)
The status of the stage with code (237) Active Blind Spot Assist is sent by the following control units over the drive train CAN (CAN C) to the CDI control unit or the ME-SFI [ME] control unit:
- Fully integrated transmission control unit (Y3/8n4) (transmission 722.9 or 724.2) or
- Electronic transmission-control control unit (N15/3) (transmission 722.6)
The CDI control unit or the ME-SFI [ME] control unit sends the gear status over the chassis CAN to the video and radar sensor system control unit.
The status of the service brake (with code (237) Active Blind Spot Assist) is sent by the Electronic Stability Program control unit or the brake system control unit over the chassis CAN to the video and radar sensor system control unit.
Blind Spot Assist (up to 31.5.10):
The radar sensors control unit reads in all relevant information over the chassis CAN and evaluates it.
To this end, the front SAM control unit routes all information sent over the body CAN from the body CAN to the chassis CAN.
Blind Spot Assist (as of 1.6.10):
The intelligent radar sensors read in all relevant information over the front end CAN.
For this purpose, the front SAM control unit routes the corresponding information from the chassis CAN to the front end CAN.
Active Blind Spot Assist:
The video and radar sensor system control unit reads in all relevant information over the chassis CAN and evaluates it.
To this end, the front SAM control unit routes all information sent over the body CAN from the body CAN to the chassis CAN.
The Blind Spot Assist system includes the following subfunctions:
- Measuring procedure function sequence
- System and warning messages function sequence
- Function sequence for active intervention by the brake system (with code (237) Active Blind Spot Assist)
Measuring procedure function sequence
The acquisition of vehicles which are located in the blind spot is based on the radar measuring procedure. The radar sensors emit pooled electromagnetic waves as so-called primary signals.
If these impact with a vehicle that is located in the blind spot, they are reflected from it and received again by the corresponding wheel sensor as secondary signals.
These signals are used to determine the distance and the speed of the recorded object as well as its angle relative to the systems vehicle.
The short-range radar sensors are ultra-wideband radar sensors and have the following properties:
- Acquisition range s = 0.18 to 3 m
- Acquisition angle ∠ = 60° with angle determination and ∠ = 130° only detection (track)
- Radar sensor with f = 24 GHz carrier frequency
- Method of operation: short pulse method with f = 5 GHz band width
The range up to a maximum s = 200 m in front of the vehicle with code (237) Active Blind Spot Assist is monitored by the DISTRONIC controller unit (long range radar).
The monitoring range distance is flexibly configured and is regulated to match the vehicle speed.
The signals from the DISTRONIC controller unit are sent over the vehicle dynamics CAN to the video and radar sensor system control unit.
Detection range of radar sensor system with code (234) Blind Spot Assist
Detection range of radar sensor system incl. front traffic area monitoring with code (237) Active Blind Spot Assist
The diagram of the monitoring range refers to the radar sensor system's radiation angle. The actual monitoring range of the "blind spot" however, is "extrapolated" in the radar sensors control unit, each rear bumper intelligent radar sensor or in the video and radar sensor system control unit.
This yields the actual monitoring range, which is graphically represented as follows:
Display of actual monitoring range at rear (with code (234) Blind Spot Assist or code (237) Active Blind Spot Assist)
Automatic shutoff of radar sensor system
In the vicinity of radio-astronomy stations the radar sensor system is automatically switched on and off due to the legal requirements of the 24-GHz-Radar system (short range radar).
For vehicles with code (494) USA version the automatic activation/deactivation of the short range radar sensors is discontinued.
In other words the Blind Spot Assist is not functional in these ranges.
The restricted areas around radio astronomy stations are filed in each control unit.
The navigation system of the following control units receives the global positioning system (GPS) signals over the multifunction antenna (A28/11):
- Radio (A2) (with code (523) MB Audio 20 radio or code (510) Audio 20 incl. CD changer), in combination with telematics CAN adapted navigation module (with code (509) Navigation box)
- Radio with auto pilot system (A2/56) (with code (511) Audio 50 APS with DVD changer or code (525) MB Audio 50 APS radio)
- COMAND controller unit (A40/3) (with code (512) COMAND APS with DVD changer or with code (527) COMAND APS with single DVD drive (with navigation))
The listed control units send the GPS signals over the interior CAN.
Blind Spot Assist (up to 31.5.10):
The radar sensors control unit receives the GPS signals over the front SAM control unit and the chassis CAN. The radar sensors control unit then sends a request to switch off the radar sensor system over the sensor-CAN.
Blind Spot Assist (as of 1.6.10):
The intelligent radar sensors read in the GPS signals over the front SAM control unit and the front end CAN, which then switch off the integrated radar sensor system.
Active Blind Spot Assist:
The video and radar sensor system control unit receives the GPS signals over the front SAM control unit and the chassis CAN. The video and radar sensor system control unit then sends a request to switch off the radar sensor system over the sensor-CAN.
For an active Blind Spot Assist, the "Radar sensor system automatically switched off, see operator's manual" message is shown on the multifunction display (A1p13) 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 Global Positioning System (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 readiness and warning indicator lamps are switched off.
Manual switching on/off of the radar sensor system:
There is also the possibility of switching the radar sensor system off and on again manually via the "Vehicle" menu in the IC.
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".
System and warning messages function sequence
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.
The status of circuit 15 is sent by the electronic ignition lock control unit (N73) over the chassis CAN.
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.
As from a v > 250 km/h the Blind Spot Assist readiness and warning indicators also go out, the Blind Spot Assist function is not yet functional.
If a system error is determined, a corresponding message is shown on the instrument cluster's multifunction display and the Blind Spot Assist readiness and warning indicators light up in yellow.
The Blind Spot Assist readiness and warning indicators are actuated by the corresponding front door control unit.
The system readiness status or the request to issue warning and fault messages is sent by the respective control unit.
Blind Spot Assist (up to 31.5.10):
The radar sensors control unit sends the system readiness status or the request to issue warning and fault messages over the chassis CAN, front SAM control unit and the body CAN to the corresponding front door control unit and over the chassis CAN to the instrument cluster.
Blind Spot Assist (as of 1.6.10):
The intelligent radar sensors sends the system readiness status over the front end CAN, front SAM control unit and the body CAN to the corresponding front door control unit.
The request to issue warning and fault messages is sent by the right intelligent radar sensor as a master over the front end CAN, front SAM control unit and the body CAN to the corresponding front door control unit and over the front end CAN, front SAM control unit and chassis CAN to the instrument cluster.
Active Blind Spot Assist:
The video and radar sensor system control unit sends the system readiness status or the request to issue warning and fault messages over the chassis CAN, front SAM control unit and the body CAN to the corresponding front door control unit and over 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.
As a consequence, any warning may then come 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 (S4) (operates turn signal), a 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 displaying system readiness corresponds to that of the warning display.
Combination switch signal curve:
The steering column tube module control unit (N80) reads in the switch position of the combination switch and sends it over the chassis CAN.
Blind Spot Assist (up to 31.5.10):
The radar sensors control unit receives the switch position of the combination switch through the chassis CAN.
Blind Spot Assist (as of 1.6.10):
The intelligent radar sensors receive the switch position of the combination switch over the front end CAN from the front SAM control unit.
Active Blind Spot Assist:
The video and radar sensor system control unit receives the switch position of the combination switch over the chassis CAN.
Blind Spot Assist readiness display
Blind Spot Assist warning indicator
The right Blind Spot Assist readiness and warning indicator corresponds to the left Blind Spot Assist readiness and warning indicator.
The following table contains the requirements for displaying system readiness and for showing the visual warning messages:
| Operating condition | 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 up 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 | |||
| Course-correcting intervention by the brake system 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 intervention by the brake system (with code (237) Active Blind Spot Assist)
- Electronic Stability Program (ESP) not shifted to passive (except model 212.074/077/274/277) or ESP not shifted to "SPORT HANDLING MODE" (model 212.074/077/274/277)
- ESP not in active diagnosis or roller dynamometer mode
- Antilock braking system (ABS), acceleration skid control (ASR), Active Brake Assist System (BAS), ESP, PRE-SAFE brake inactive
- Vehicle speed v < 200 km/h or v < 120 mph
- No active control intervention function in brake assistance systems
- Enabling of active brake intervention issued by yawing moment interface
The yawing moment interface, which is integrated in the Electronic Stability Program control unit or the brake system control unit, internally issues an enabling signal for course-correcting braking torque.
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, a course-correcting intervention by the brake system is requested. To this end, the video and radar sensor system control unit sends corresponding requests over the vehicle dynamics CAN to the brake system control unit or the Electronic Stability Program control unit, which then implements them accordingly. The brake system control unit or the Electronic Stability Program control unit selectively brakes individual wheels and guides the vehicle back onto a collision-free course.
If during an intervention by the brake system the driver steers opposite to the intervention by the brake system (i.e. overrides the intervention by the brake system) or if the vehicle is accelerated, 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 and they result in cancellation of an 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:
- Faster or greater pressure loss at a tire
Information on tire pressure monitoring is available in the separate "Tire pressure monitor function" or "Tire pressure loss warning (RDW) function" description.
- Risk of frontal collision of vehicle with vehicle or obstacle in the direction of travel within t = 2.6 s (with constant movement conditions)
- Vehicle acceleration or deceleration in longitudinal direction as well as lateral acceleration of a = 4 m/s 2
up to 6 m/s 2
The acceleration forces are recorded by the yaw rate sensor for lateral and longitudinal acceleration (B24/15). 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 (N49). The steering column tube module control unit reads in the steering angle sensor data 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, on both sides of the systems vehicle (1), vehicles are located close up in the blind spot (2), a course-correcting intervention by the brake system is suppressed.
If an obstacle (8) is located at the side next to the systems vehicle (1), the position of which cannot be determined, a course-correcting intervention by the brake system in the direction of the obstacle (8) is suppressed.
If a stationary obstacle (8) is detected on one side of the systems vehicle (1), a 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 event of oncoming traffic a course-correcting intervention by the brake system is limited so that any collision with oncoming traffic is avoided.
| Blind Spot Assist, location of components | GF54.71-P-0003-02FL | ||
| Electrical function schematic, blind spot assistant | Up to 31.5.10 with code (234) Blind Spot Assist | PE54.71-P-2051-97DAA | |
| As of 1.6.10 with code (234) Blind Spot Assist | PE54.71-P-2051-97DAB | ||
| As of 1.6.10 with code (237) Active Blind Spot Assist | PE54.71-P-2051-97DAC | ||
| Blind Spot Assist block diagram | GF54.71-P-0003-01FL | ||
| Table of contents for system components, Blind Spot Assist | GF54.71-P-9997FL |