Part 2
Detection range of radar sensor system incl. front road space monitoring with code (237) Active Blind Spot Assist, shown on model 204.0
1 Systems vehicle
2 Vehicle in blind spot
3 Left rear monitoring range
4 Right rear monitoring range
5 Left front monitoring range
6 Right front monitoring range
7 Front monitoring range
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 each 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)
1 Systems vehicle
3 Left rear monitoring range
4 Right rear monitoring range
C 0.5 m
D 3.0 m
Automatic shutoff of radar sensor system
In the vicinity of radio-astronomy stations the radar sensor system is switched off automatically due to the legal requirements on the 24-GHz-Radar system (short range radar).
On vehicles with code (494) USA version, automatic deactivation of the short-range radar sensors is not provided.
In other words the Blind Spot Assist is not functional in these ranges.
The protected areas around radio astronomy stations are stored in the video and radar sensor system control unit or in the right intelligent radar sensor and left intelligent radar sensor.
The navigation system of the COMAND controller unit or the radio in combination with the navigation module adapted via the telematics CAN receives the global positioning system (GPS) signals via the multifunction antenna. The radio or the COMAND controller unit permanently sends the current GPS coordinates via the interior CAN to the front SAM control unit.
The front SAM control unit sends the GPS signals via the chassis CAN and front end CAN.
The video and radar sensor system control unit receives this information via the chassis CAN and sends a corresponding request to deactivate the short-range radar sensors via the sensor CAN.
The intelligent radar sensors receive this information over the front end CAN, as sent by the front SAM control unit, which then shuts off the integrated radar sensor systems.
If the Blind Spot Assist is active, the message "Radar sensor system autom. deactivated, see operator's manual" is shown in 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.
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 readiness and warning indicator lamps are switched off.
Manual switching on/off of the radar sensor system:
The short-range radar sensor system can be switched off and on again manually via the "Vehicle" menu in the instrument cluster. If the short-range radar sensor system was automatically switched off within a restricted area, the manual switch-on option is no longer available and the following message "Radar sensor system automatically switched off, see operator's manual" is shown.
Schematic representation of automatic shutoff of radar sensor system, shown on model 204.0
A1p13 Multifunction display
A2 Radio (with code (523) MB Audio 20 radio or code (510) Audio 20 with CD changer)
A2/30 Navigation module (with code (509) Navigation box)
A2/30-1 Cradle for navigation module (with code (508) Navigation box preinstallation or code (509) Navigation box)
A28/11 Multifunction antenna
A40/3 COMAND controller unit (with code (512) COMAND APS incl. DVD changer or code (527) COMAND APS with single DVD drive (with navigation))
B29/2 Left front bumper DISTRONIC (DTR) sensor (with code (237) Active Blind Spot Assist)
B29/3 Right front bumper DISTRONIC (DTR) sensor (with code (237) Active Blind Spot Assist)
B29/4 Left rear bumper intelligent radar sensor (with code (234) Blind Spot Assist)
B29/5 Right rear bumper intelligent radar sensor (with code (234) Blind Spot Assist)
B29/6 Left rear bumper radar sensor (with code (237) Active Blind Spot Assist)
B29/7 Right rear bumper radar sensor (with code (237) Active Blind Spot Assist)
N62/2 Video and radar sensor system control unit (with code (237) Active Blind Spot Assist)
GPS Global Positioning System
RAS Radio astronomy station
Std. Restricted area for a radio astronomy station
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 via the chassis CAN, front SAM control unit and front end CAN to the intelligent radar sensors.
On vehicles with code (237) Active Blind Spot Assist, the electronic ignition lock control unit sends the status of circuit 15 via the chassis CAN to the video and radar sensor system control unit.
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:
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 greater than or equal to 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 (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 displaying system readiness corresponds to that of the warning display.
The steering column tube module control unit reads in the switch position of the combination switch and sends it over the chassis CAN.
Blind Spot Assist:
The intelligent radar sensors receive the switch position of the combination switch over the front end CAN from the front SAM control unit.
Blind Spot Assist readiness display
M21/1e2 Left Blind Spot Assist readiness and warning indicator
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 warning indicator
M21/1e2 Left Blind Spot Assist readiness and warning indicator
The left Blind Spot Assist readiness and warning indicator corresponds to the right Blind Spot Assist readiness and warning indicator.
The following table contains the requirements for displaying system readiness and for showing the visual warning messages:
Additional function requirements for active intervention by the brake system (with code (237) Active Blind Spot Assist)
^ Electronic Stability Program (ESP(R)) not switched to passive (except model 204.077 277/377) or ESP(R) not switched to "SPORT HANDLING MODE" (model 204.077/277/377)
^ ESP(R) not in active diagnostic or roller dynamometer mode
^ Antilock brake system (ABS), acceleration skid control (ASR), active Brake Assist (BAS), ESP, PRE-SAFE brake inactive
^ Vehicle speed v < 200 km/h (metric display) or v < 120 mph (miles display)
^ 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.
The Electronic Stability Program control unit selectively brakes individual wheels and moves the vehicle back onto a collision-free course.
For this purpose, the video and radar sensor system control unit sends a corresponding request via 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.
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 systems and driving safety systems ABS, ASR, BAS, ESP(R) and PRE-SAFE brake are of a higher priority than the Active Blind Spot Assist and result in termination of active brake intervention.
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. 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 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.
1 Systems vehicle
2 Vehicle in blind spot
3 Left rear monitoring range
4 Right rear monitoring range
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.
1 Systems vehicle
2 Vehicle in blind spot
3 Left rear monitoring range
8 Obstacle
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.
1 Systems vehicle
2 Vehicle in blind spot
3 Left rear monitoring range
4 Right rear monitoring range
6 Right front monitoring range
7 Front monitoring range
8 Obstacle
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.
1 Systems vehicle
2 Vehicle in blind spot
3 Left rear monitoring range
7 Front monitoring range
10 Vehicle in front
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!
1 Systems vehicle
2 Vehicle in blind spot
3 Left rear monitoring range
7 Front monitoring range
8 Obstacle
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!
1 Systems vehicle
2 Vehicle in blind spot
4 Right rear monitoring range
7 Front monitoring range
9 Oncoming traffic
In the case of oncoming traffic, course-correcting intervention by the brake system is limited so that any collision with oncoming traffic is avoided.
