GF54.71-P-0003CA Blind Spot Assist, Function
GF54.71-P-0003CA Blind Spot Assist, Function
MODEL 207
- with CODE (234) Blind Spot Assist
- with CODE (237) Active Blind Spot Assist
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
- Circuit 61 ON or "PT_Rdy" (drivetrain ready) signal set
- Vehicle moving forward
- Vehicle speed: v = ≥30 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 (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
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 (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:
- 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 masterslave 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.
Interventions by the brake system are conducted on a wheel-specific basis and exert a course-correcting influence on the systems vehicle. 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 (B29/6)
- Right rear bumper radar sensor (B29/7)
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 transmitted to the video and radar sensor system control unit (N62/2) over the sensor CAN (CAN S).
The signals from the DISTRONIC controller unit are read in over the vehicle dynamics CAN (CAN H) by 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
A Lane with vehicle in blind spot during passing maneuver
B Lane with systems vehicle
t1 Vehicle moves into blind spot
t2 Vehicle in blind spot detected, acoustic and visual warning messages issued
t3 Initiation of course-correcting intervention by the brake system (with code (237) Active Blind Spot Assist)
t4 Course-correcting intervention by the brake system completed, collision avoided (with code (237) Active Blind Spot Assist)
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 (CAN E).
The status of circuit 61 or the status of the "PT_Rdy" signal is sent by the CDI control unit (N3/9) (with diesel engine) or the ME-SFI [ME] control unit (N3/10) (with gasoline engine) 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 directions and wheel speeds 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 signals from the listed rpm sensors are read in directly by the following control unit depending on the model and equipment and then sent over the chassis CAN:
- Electronic Stability Program control unit (N30/4) (with code (234) Blind Spot Assist)
- Premium Electronic Stability Program control unit (N30/7) (with code (237) Active Blind Spot Assist)
The gear range status on vehicles with code (237) Active Blind Spot Assist is sent by the following control unit 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)
- Electronic transmission-control control unit (N15/3) (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 yawing-moment interface that is integrated into the Electronic Stability Program control unit sends out a status signal to enable course-correcting brake system interventions.
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 provided via the interior CAN (CAN B) from the interior CAN to the chassis CAN.
The Blind Spot Assist system comprises 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 angle = 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 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.
Schematic display of monitoring range with code (234) Blind Spot Assist
1 Systems vehicle
2 Vehicle in blind spot
3 Left rear monitoring range
4 Right rear monitoring range
Diagram of monitoring range incl. front road space monitoring with code (237) Active Blind Spot Assist
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 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)
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).
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 radio with Auto Pilot System (A2/56) (with code (511) Audio 50 APS incl. DVD changer or code (525) MB Audio 50 APS radio) or the COMAND controller unit (A40/3) (with code (512) COMAND APS incl. DVD changer or code (527) COMAND APS with single DVD drive (with navigation)) transmits corresponding position data from the navigation system over the body CAN.
Blind Spot Assist:
The intelligent radar sensors read in the positioning data from the navigation system over the front end CAN and switch off the integrated radar sensor system. To this end, the front SAM control unit routes this information over the body CAN to the front-end CAN.
Active Blind Spot Assist:
The video and radar sensor system control unit reads in the positioning data from the navigation system over the chassis CAN and switches off the radar sensor system. To this end, the front SAM control unit routes this information over the body CAN to the chassis 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: 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 display of automatic radar sensor system shutoff
A1p13 Multifunction display
A2/56 Radio with auto pilot system (with code (511) Audio 50 APS with DVD changer or code (525) MB Audio 50 APS radio)
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
SB 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. 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 depending on the request from the left front door control unit (N69/1) or right front door control unit (N69/2).
The electronic ignition lock control unit (N73) transmits the circuit status of circuit 15 via 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 (S4) (operates flasher), a one-time double-warning tone is 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:
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 mode
- ESP(R) not in active diagnosis or roller dynamometer mode
- Anti-lock braking system (ABS), acceleration skid control (ASR), Brake Assist System (BAS), ESP(R), 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 driving assistance or driving safety systems ABS, ASR, BAS, ESP(R) and PRE-SAFE brake is sent by the Premium 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 Premium Electronic Stability Program control unit, which then implements them accordingly. The Premium 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(R) and PRE-SAFE brake have a higher priority than the Active Blind Spot Assist system 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/s2
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 coursecorrecting 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 close up 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 coursecorrecting 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
7 Front monitoring range
9 Oncoming traffic
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.
