Blind Spot Assist, function - GF54.71-P-0003CE
MODEL 204.0/2
with CODE (234) Blind Spot Assist
with CODE (237) Active Blind Spot Assist
as of model year 2012
/YoM 11 model refinement package
MODEL 204.3
with CODE (234) Blind Spot Assist
with CODE (237) Active Blind Spot Assist
Vehicles with code (234) Blind Spot Assist
Vehicles with code (237) Active Blind Spot Assist
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
- Circuit 61 ON or "PT_Rdy" (drivetrain ready) signal set
- Vehicle moving forward
- Vehicle speed: v = ≥ E30 to 250 km/h
- No trailer operation
Blind Spot Assist, general
The Blind Spot Assist using short range radar to monitor the left and right rear sides to the rear of the driver's field of vision, which cannot be seen in the outside mirror ("blind spot").
If a vehicle is in this area the driver is notified that any intended lane change (flasher operated) is not advisable at that particular moment.
In the broader sense, the Blind Spot Assist system acts as an extension of the rearview mirrors. It does not release the driver of his/her obligation to perform lane changes safely on his/her own responsibility. In the left outside mirror (M21/1) and in the right outside mirror (M21/2) a visual indicator provides information about the active condition of the system and about 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
- Right Blind Spot Assist readiness and warning indicator
The acoustic warning is output via the warning buzzer (A1h1) in the instrument cluster.
The from SAM control unit is the central interface for data exchange between the different 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:
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 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 established over the plug coding. The "master function" is defined for the right intelligent radar sensor. In other words, the left intelligent radar sensor sends its requests to output warning and readiness messages over the front end CAN to the right intelligent radar sensor, which evaluates the information of both intelligent radar sensors, and then forwards corresponding requests over the front end CAN to the front SAM control unit.
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 controller unit
- DISTRONIC sensor (DTR)/left front bumper
- DISTRONIC sensor (DTR)/right front bumper
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 over the sensor CAN. The signals of the DISTRONIC electric controller unit are received by the video and radar sensor system control unit over the vehicle dynamics CAN.
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"
- Circuit 61 ON or signal "PT_Rdy" (drivetrain ready)
- Vehicle moving forward
- Vehicle speed
- Gear range status (with code (237) Active Blind Spot Assist)
- Status of yawing moment interface (with code (237) Active Blind Spot Assist)
- Brake status (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).
The status of circuit 61 or the "PT_Rdy" signal status is sent by the CDI control unit or the ME-SFI [ME] control unit over the chassis 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 components:
- Left front axle speed sensor
- Right front axle speed sensor
- Left rear axle speed sensor
- Right rear axle speed sensor
The wheel rotation direction is determined to match the drive variant. Details on its function are available in the separate description for the "Electronic Stability Program (ESP) function".
The Electronic Stability Program control unit reads in the signals from the RPM sensors and send them over the chassis CAN.
The front SAM control unit and the video and radar sensor system control unit receive the RPM sensor signals over the chassis CAN. The intelligent radar sensors receive the RPM sensor signals over the front end CAN from the front SAM control unit.
The video and radar sensor system control unit or the intelligent radar sensors use the RPM sensor signals to calculate the vehicle speed and direction of travel.
Blind Spot Assist:
The intelligent radar sensors read in all relevant information over the front end CAN.
To this end, the front SAM control unit routes this 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 status of the brake (with code (237) Active Blind Spot Assist) is sent by the Electronic Stability Program control unit over the chassis CAN to the video and radar sensor system control unit.
The gear range status with code (237) Active Blind Spot Assist is sent by the following control unit over the drive train CAN to the CDI control unit or the ME-SFI [ME] control unit:
- Fully integrated transmission-control control unit (with transmission 722.9)
- Electronic transmission-control control unit (on transmission 722.6)
The CDI control unit or the ME-SFI [ME] control unit sends the gear range status over the chassis CAN to the video and radar sensor system control unit.
The status of the brake and the yawing-moment interface (with code (237) Active Blind Spot Assist) is sent by the Electronic Stability Program control unit over the chassis CAN to the video and radar sensor system control unit.
The Blind Spot Assist is made up 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.
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 with 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 monitoring range travel 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.
Diagram of monitoring range with code (234) Blind Spot Assist, shown on model 204.0
Diagram of monitoring range incl. monitoring of front road space with code (237) Active Blind Spot Assist, shown on model 204.0
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)
Automatic shutoff of short-range radar sensor system:
In the vicinity of radio-astronomy stations the short-range radar sensor system is switched off automatically due to the legal requirements on the 24-GHz radar system.
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 navigation module adapted to the telematics CAN, permanently sends the current GPS coordinates over the interior CAN to the front SAM control unit.
The front SAM control unit sends the corresponding position information from the navigation system over the chassis CAN and front end CAN. The video and radar sensor system control unit receives this information over the chassis CAN and switches off the radar sensor system.
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.
When Blind Spot Assist is active, the message "Radar sensor system automatically switched off, see operator's manual" 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 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 "Vehicle" menu in the instrument cluster enables the short-range radar sensor system to be manually switched off and on again. 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
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 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 electronic ignition lock control unit transmits the status of circuit 15 over the chassis CAN.
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 ≥ 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
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
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:
| 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 | |||
| Circuit 61 ON or "PT_Rdy" (drivetrain ready) signal set | 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 204.077/277/375) or ESP not shifted to "SPORT HANDLING MODE" (model 204.077/277/375)
- ESP not in active diagnosis 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 or v < 120 mph
- Approval issued for active intervention by the brake system for yawing moment interface
- No active control intervention function in brake assistance systems
The status information from the driver assistance or driving-safety systems ABS, ASR, BAS, ESP and PRE-SAFE brake is sent by the Electronic Stability Program control unit over 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, 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 Electronic Stability Program control unit, which then implements them accordingly. The Electronic Stability Program control unit selectively brakes individual wheels and moves 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 driving 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/s2
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.
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!
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.
| Electrical function schematic, blind spot assistant | For code (234) Blind Spot Assist | PE54.71-P-2051-97FAA | |
| With code (237) Active Blind Spot Assist | PE54.71-P-2051-97FAB | ||
| Overview of system components for driver assistance systems | GF54.00-P-9998CE |