Blind Spot Monitor, function - GF54.71-P-0003LE
MODEL 216.3, 221.0 /1 up to 31.8.10 with CODE (234) Blind Spot Assist as of model year 2009/YoM 08
MODEL 216.3 with CODE (237) Active Blind Spot Assist as of Model Year 2011/YoM 10 model refinement package
MODEL 221.0 /1 (except 221.095 /195) with CODE (237) Active Blind Spot Assist as of Model Year 2011/YoM 10
MODEL 221.095 /195 with CODE (234) Blind Spot Assist as of model year 2010
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 (n > 300 RPM)
- No trailer operation
- Vehicle moving forward
- Vehicle speed ≥30 km/h (without code (494) USA version)
- Vehicle speed ≥20 mph (with code (494) USA version)
- Brake not operated or no active control intervention by brake assist systems (with code (237) Active Blind Spot Assist)
- Driver detected (with code (237) Active Blind Spot Assist)
- Vehicle doors closed (with code (237) Active Blind Spot Assist)
Blind Spot Assist, function (general)
The Blind Spot Assist monitors the rear area of the vehicle by means of short range radar and informs the driver if necessary that an intended lane change (turn signal set) is not recommended at the present 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.
A visual indicator in the left electrically adjustable and heated outside mirror (M21/1) and in the right electrically adjustable and heated outside mirror (M21/2) provides information on the active status of the system and on the critical condition (i.e. a vehicle is in the "blind spot").
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 through the following component:
- Warning buzzer (A1h1) in the IC
A differentiation 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:
The area which cannot be observed via the outside mirror and inside rearview mirror is monitored by the following components:
- Outer right radar sensor, rear bumper (A86/2b1) (as of 1.9.09)
- Inner right radar sensor, rear bumper (A86/2b2) (up to 31.8.09)
- Inner left radar sensor, rear bumper (A86/2b3) (up to 31.8.09)
- Outer left radar sensor, rear bumper (A86/2b4) (as of 1.9.09)
All relevant data is evaluated by the radar sensors control unit (SGR) (N62/1).
Active Blind Spot Assist:
The Active Blind Spot Assist is an extension of the Blind Spot Assist function. The Active Blind Spot Assist can additionally initiate intervention by the brake system, taking the surroundings of the systems vehicle into consideration.
Active brake intervention is performed on a wheel-specific basis and corrects the course of the system vehicle.
If a risk of collision with vehicles located in the blind spot is detected, an accident can thus be avoided or the seriousness of an accident can be lessened.
The area which cannot be observed via the outside mirror and inside rearview mirror is monitored by the following components:
- Right outer radar sensor, rear bumper
- Left outer radar sensor, rear bumper
A prerequisite for course-correcting intervention is the monitoring of the road space in front of the vehicle in order to avoid, for example, collisions with oncoming traffic or stationary obstacles.
Monitoring of the road space in front is implemented by means of the following components:
- s > 0.5 to 3 m in front of the vehicle:
- Inner left radar sensor, front bumper (A86/1b2)
- Inner right radar sensor, front bumper (A86/1b3)
- s > 3 to 27 m in front of the vehicle:
- DTR controller unit (A89)
The signals from the front bumper radar sensors are forwarded via the sensor CAN (CAN S) to the video and radar sensor system control unit (N62/2).
The signal from the DISTRONIC electric controller unit are sent over the dynamics CAN (CAN H) to the video and radar sensor system control unit.
All relevant data is evaluated by the video and radar sensor system control unit.
Illustration of the Blind Spot Assist principle
The following information is read in by the radar sensors control unit (with code (234) Blind Spot Assist) or by the video and radar sensor system control unit (with code (237) Active Blind Spot Assist):
- Status of function "Blind Spot Assist"
- Engine running (n > 300 RPM)
- Vehicle moving forward
- Vehicle speed
- Brake status (with code (237) Active Blind Spot Assist)
- Driver detection and vehicle door status (with code (237) Active Blind Spot Assist)
The instrument cluster sends the status of the "Blind Spot Assist" function via the central CAN (CAN F) to the central gateway control unit (N93). The central gateway control unit forwards the status of the "Blind Spot Assist" function via the chassis CAN (CAN E) to the radar sensors control unit or the video and radar sensor system control unit.
The CDI control unit (N3/9) (with diesel engine) or the ME-SFI [ME] control unit (N3/10) (with gasoline engine) transmits the engine speed via the chassis CAN. The radar sensors control unit or the video and radar sensor system control unit receives the engine speed via the chassis CAN.
The forward movement is defined via the wheel rotation direction and the vehicle speed via the wheel speed.
The wheel speed and the wheel rotation direction are detected by the following components:
- Left front RPM sensor (L6/1)
- Right front RPM sensor (L6/2)
- Left rear RPM sensor (L6/3)
- Right rear RPM sensor (L6/4)
On vehicles as of 1.9.10, the wheel rotation direction is detected by the following components:
- Left front RPM sensor
- Right front RPM sensor
The ESP control unit (N47-5) (without model 221.095 /195) or the regenerative braking system control unit (N30/6) (with model 221.095/195) reads in the signals from the RPM sensors and transmits them via the chassis CAN.
The radar sensors control unit or the video and radar sensor system control unit receives the signals from the RPM sensors via the chassis CAN and calculates the vehicle speed.
The brake status is transmitted by the ESP control unit or regenerative braking system control unit via the chassis CAN. The radar sensors control unit or the video and radar sensor system control unit receives the brake status via the chassis CAN.
The "driver detected" and "vehicle doors closed" status (with code (237) Active Blind Spot Assist) is determined by the standstill coordinator function which is defined by the following parameters:
- Doors closed
- Seat belt applied
The ESP control unit sends the status of the standstill coordinator via the chassis CAN to the video and radar sensor system control unit.
The standstill coordinator function is implemented in the ESP control unit or in the regenerative braking system control unit. A detailed function description is given in a separate section.
The Blind Spot Assist function consists of 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. In the process, electromagnetic waves from radar sensors are bundled and sent out 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 calculate the distance and the speed of the detected object.
The radar sensors are ultra wideband radar sensors with the following properties:
- Acquisition range s = 0.5 to 3 m
- Acquisition angle ∠ = 80° with angle determination and ∠ = 140° only detection (track)
- Radar sensor with f = 24 GHz carrier frequency
- Method of operation: Short pulse method with f = 5 GHz band width
Schematic diagram of monitoring range with code (234) Blind Spot Assist (up to 31.8.09)
Schematic diagram of monitoring range with code (234) Blind Spot Assist (as of 1.9.09)
Schematic display of monitoring range with code (237) Active Blind Spot Assist
Automatic deactivation of short-range radar sensor system: In the vicinity of radio astronomy stations, the short-range radar sensor system is automatically deactivated to comply with legal requirements governing the 24 GHz radar system (short range radar). In other words the Blind Spot Assist is not functional in these ranges.
The protection zones around radio astronomy stations are stored in the radar sensors control unit or in the video and radar sensor system control unit.
The COMAND controller unit (A40/3) transmits location data from the navigation system via the central CAN, central gateway control unit and chassis CAN.
The radar sensors control unit or the video and radar sensor system control unit receives this information via the chassis CAN and deactivates the radar sensor system.
When the Blind Spot Assist is active the message "Radar sensor system automatically switched off, see operating instructions" is displayed in 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.
When the vehicle leaves the protection zone, the short-range radar sensor system is automatically reactivated.
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: The "Vehicle" menu in the instrument cluster enables the 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".
Schematic representation of automatic shutoff of radar sensor system, shown on model 221
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. When a vehicle speed of v > 30 km/h (v > 20 mph) is reached, the Blind Spot Assist readiness and warning indicators disappear again and the Blind Spot Assist is ready to issue warnings. If a system fault is found, a corresponding message appears in the multifunction display and the readiness and warning indicators for the Blind Spot Assist light up yellow.
The status of circuit 15 is transmitted by the EZS control unit (N73) via the chassis CAN.
The system readiness status and the request to output fault messages are sent by the radar sensors control unit (with code (234) Blind Spot Assist) or the video and radar sensor system control unit (with code (237) Active Blind Spot Assist) to the central gateway control unit via the chassis CAN. The instrument cluster receives the request to output fault messages via the central CAN (provided by the central gateway control unit).
The central gateway control unit receives the system readiness status and the request to output fault messages via the chassis CAN and forwards them via the interior CAN to the following control units which, in turn, actuate the appropriate Blind Spot Assist readiness and warning indicator:
- Left front door control unit (N69/1) (model 221) or left door control unit (N69/1) (model 216)
- Right front door control unit (N69/2) (model 221) or right door control unit (N69/2) (model 216)
Blind Spot Assist ready
If at a speed of v ≥30 km/h (v ≥20 mph) a vehicle is located within the detection range of the radar sensor system, the driver is alerted by the Blind Spot Assist readiness and warning indicator lighting up red in the outside mirror on the side on which the vehicle is in the blind spot.
Overtaking vehicles are detected reliably up to a relative speed of v = 35 km/h (v = 22 mph).
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 the driver tries to initiate a lane change despite the lighting up of the readiness and warning indicator for the Blind Spot Assist and signals this by operating the combination switch (S4) (set flasher), in addition the output of a one-time dual warning tone takes place by the warning buzzer in the IC. 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 issue of warning messages corresponds to that of the display for system readiness.
The switch position of the combination switch is read in directly by the steering column tube module (N80) and transmitted via the chassis CAN. The radar sensors control unit or the video and radar sensor system control unit receives the switch position of the combination switch via the chassis CAN.
Vehicle in blind spot (in detection range of radar sensor system)
The following table contains the requirements for displaying system readiness and for outputting 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 (n > 300 RPM) | X | |||
| Vehicle accelerates, Vehicle speed v ≥30 km/h (v ≥20 mph) | X | |||
| Vehicle decelerates, Vehicle speed v≤25 km/h (v ≥16 mph) | X | |||
| Trailer detected (with code (550) Trailer hitch) | X | |||
| Drive position "R" engaged | 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 switched to passive mode (except model 221.074/174)
- ESP up to 31.8.10 not switched to "ESP-Sport" mode, as of 1.6.10 not switched to "SPORT HANDLING MODE" (with model 221.074/174)
- Anti-locking brake system (ABS), acceleration skid control (ASR), active Brake Assist (BAS), ESP, PRE-SAFE brake inactive
- Vehicle speed v < 200 km/h or v < 120 mph
The status information from the driving assistance and driving safety systems ABS, ASR, BAS, ESP and PRE-SAFE brake is sent by the ESP 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 an intended lane change, a course-correcting intervention by the brake system is requested.
For this purpose, the video and radar sensor system control unit sends appropriate requests via the chassis CAN to the ESP control unit which then implements these requests accordingly. The ESP control unit brakes individual wheels selectively and sets the vehicle back on 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 driving assistance and driving safety systems ABS, ASR, BAS, ESP and PRE-SAFE brake have a higher priority than the Active Blind Spot Assist and cause active intervention by the brake system to be canceled.
If the ABS is actively intervening, brake intervention by the Blind Spot Assist is not initiated.
During such an intervention by the brake system, the ABS may reduce the intensity of the brake intervention; the brake intervention itself is, however, continued.
Course-correcting interventions by the brake system are always suppressed, when one of the following conditions occurs:
- Pressure loss at a tire
- Risk of frontal collision with a vehicle or obstacle in the direction of travel within t = 2.6 s (with constant motion conditions)
- Acceleration or deceleration of the vehicle in longitudinal direction and also lateral acceleration of a = 0.4 g to 0.6 g.
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.
The steering movements are detected by the steering angle sensor (N49) and read in by the steering column tube module which sends the information regarding steering angle speed via the chassis CAN to the video and radar sensor system control unit.
The diagrams below show situations in which course-correcting interventions by the brake system are suppressed.
If, on both sides of the systems vehicle (1), vehicles are located 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!
| Blind Spot Assist, location of components | GF54.71-P-0003-02LE | ||
| Electrical function schematic, blind spot assistant | Model 216 up to 31.8.10 with code (234) Blind Spot Assist | PE54.71-P-2051-97CAB | |
| Model 216 with code (237) Active Blind Spot Assist | PE54.71-P-2051-97CAC | ||
| Blind Spot Assist block diagram | GF54.71-P-0003-01LE | ||
| Component description for instrument cluster | A1 Model 216.3, 221.0/1 (except 221.095/195) |
GF54.30-P-6000LE | |
| Component description for COMAND controller unit | A40/3 With code (527) COMAND APS with single DVD drive (with navigation system) |
GF82.85-P-3136LE | |
| With code (530) COMAND APS USA (with navigation system) | GF82.85-P-3136LEU | ||
| DTR controller unit, component description | A89 With code (237) Active Blind Spot Assist |
GF30.30-P-3210LED | |
| Yaw rate sensor for lateral and longitudinal acceleration, component description | B24/15 | GF42.45-P-4810LE | |
| Component description for ME-SFI [ME] control unit | With engine 273 | GF07.61-P-6000MLS | |
| Component description for ESP control unit | N47-5 Model 216.3, 221.0/1 (except model 221.095/195) |
GF42.45-P-5118LE | |
| Component description for radar sensors control unit | N62/1 For code (234) Blind Spot Assist |
GF30.30-P-3301LEB | |
| Video and radar sensor system control unit, component description | N62/2 With code (237) Active Blind Spot Assist |
GF30.30-P-3304LE | |
| Component description for left door control unit | N69/1 Model 216 |
GF72.29-P-4124LA | |
| Component description for right door control unit | N69/2 Model 216 |
GF72.29-P-4128LA | |
| EZS control unit, component description | N73 | GF80.57-P-6003LE | |
| Component description for steering column tube module | N80 | GF54.21-P-6050LE | |
| Component description for central gateway control unit | N93 | GF54.21-P-4170LE | |