Blind Spot Assist, function - GF54.71-P-0003LE
MODEL 216.3, 221.0/1 as of model year 2009 up to model year 2011 with CODE 234 (Blind Spot Monitoring)
MODEL 216.3 as of model year 2011 with CODE 237 (Active Blind Spot Assist)
MODEL 221.0 (except 221.095), 221.1 (except 221.195) as of model year 2011 with CODE 237 (Active Blind Spot Assist)
MODEL 221.095/195 as of model year 2011 with CODE 234 (Blind Spot Monitoring)
Function requirements, general
- No undervoltage or overvoltage
- Function of "Blind Spot Assist" in "Assist" menu activated in IC (A1)
- Radar sensor system not shut off (model 216 up to 31.5.13, model 221)
- Engine running or drivetrain operational
- Vehicle moving forward
- Vehicle speed v ≥ 30 up to 250 km/h (without code (494) USA version) or v ≥ 20 up to 200 mph (with code (494) USA version)
- 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 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 electrically adjustable and heated outside mirror (M21/1) and the right electrically adjustable and heated outside mirror (M21/2), a visual indicator signals the status of the Blind Spot Assist and warns of critical situations when changing lanes (i.e. a vehicle is in the "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 output via the warning buzzer (A1h1) in the instrument cluster.
A differentiation is currently made between the following Blind Spot Assist variants:
- Blind Spot Assist (for 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:
- Rear bumper outer right radar sensor (A86/2b1) (as of 1.9.09)
- Rear bumper inner right radar sensor (A86/2b2) (up to 31.8.09)
- Rear bumper inner left radar sensor (A86/2b3) (up to 31.8.09)
- Rear bumper outer left radar sensor (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 based on the functionality of the Blind Spot Assist. The Active Blind Spot Assist can also initiate course-correcting interventions by the brake system, taking the vehicle's surroundings into account using the Active Blind Spot Assist. The active interventions by the brake system are performed on specific wheels and have a course-correcting effect. 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:
- Right outer radar sensor, rear bumper
- Left outer radar sensor, rear bumper
The course-correcting intervention requires the road space in front of the vehicle to be monitored to avoid any collisions with other road users caused by any change in direction.
Monitoring of the road in front of the vehicle is performed by the following components:
- DTR controller unit (A89)
- Front bumper inner left radar sensor (A86/1b2)
- Front bumper inner right radar sensor (A86/1b3)
The front bumper radar sensors send the corresponding data via the sensor CAN (CAN S) to the video and radar sensor system control unit (N62/2). The DTR controller unit sends the corresponding data via the vehicle dynamics CAN (CAN H) to 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:
- Terminal status of terminal 15
- Status of function "Blind Spot Assist"
- Engine running or drivetrain operational
- Vehicle moving forward
- Vehicle speed
- Trailer recognition (with code (550) Trailer hitch)
- Gear (with code (237) Active Blind Spot Assist)
- Status of service brake (with code (237) Active Blind Spot Assist)
Status of circuit 15:
The EZS control unit (N73) sends the status of circuit 15 via the chassis CAN (CAN E) to 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).
Status of "Blind Spot Assist" status:
The instrument cluster sends the status of the "Blind Spot Assist" function via the central CAN (CAN F), central gateway control unit (N93) and chassis CAN to 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).
Engine running or drivetrain operational
The CDI control unit (N3/9) (with diesel engine) or the ME-SFI control unit (N3/10) (with gasoline engine) sends the "Engine running" or "Drivetrain operational" signal via the chassis CAN to 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).
Vehicle in forward movement/vehicle speed:
Forward movement is defined via the wheel rotation direction. The vehicle speed is calculated on the basis of the wheel speeds. The wheel rotation directions and wheel speeds are recorded by the following sensors:
- 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 sensors:
- Left front rpm sensor
- Right front rpm sensor
The ESP control unit (N47-5) (except model 221.095/195) or the regenerative braking system control unit (N30/6) (on model 221.095/195) reads in the signals from the rpm sensors and sends the signals via the chassis CAN to 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).
Trailer recognition (with code (550) Trailer hitch):
The trailer recognition control unit (N28/1) sends information for trailer recognition via the interior CAN (CAN B), central gateway control unit and chassis CAN to 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).
Gear (with code (237) Active Blind Spot Assist):
The EGS control unit (N15/3) (with transmission 722.6) or the fully integrated transmission control (VGS) control unit (Y3/8n4) (with transmission 722.9) sends information about the stage via the drive train CAN (CAN C), CDI control unit or ME-SFI control unit and chassis CAN to the video and radar sensor system control unit.
Status of service brake (with code (237) Active Blind Spot Assist): The status of the service brake is sent by the ESP control unit via the chassis CAN to the video and radar sensor system control unit.
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 vehicles are recorded based on the radar measuring method. The bumper radar sensors emit bundled electromagnetic waves as "primary signals". If these waves hit a vehicle, they are reflected by it and are received again by the corresponding bumper radar sensor as a secondary signal. These signals are used to calculate the distance and the speed of the detected object as well as its angle relative to the vehicle.
The bumper radar sensors are designed as ultra-wideband radar sensors with the following properties:
- Detection range: s = 0.5 to 3 m
- Detection angle of ∠ = 80° with angle measurement and ∠ = 140° detection only
- Carrier frequency: f = 24 GHz (model 216 up to 31.5.13, model 221) or f = 25 GHz (model 216 as of 1.6.13)
- Mode of operation: short pulse method with f = 5 GHz bandwidth (model 216 up to 31.5.13, model 221) or f = 1.4 GHz bandwidth (model 216 as of 1.6.13)
The 24 GHz radar sensor system is deactivated automatically in countries where it is not approved.
On vehicles with code (237) Active Blind Spot Assist, the range up to maximum s = 27 m in front of the vehicle is monitored by the DTR controller unit (long range radar). The design of the travel distance for the monitoring range is variable and matched to the vehicle speed. The DTR controller unit sends the corresponding data via the vehicle dynamics CAN to 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).
Detection range of radar sensor system with code (234) Blind Spot Assist (up to 31.8.09)
Detection range of radar sensor system with code (234) Blind Spot Assist (as of 1.9.09)
Detection range of radar sensor system with code (237) Active Blind Spot Assist
The detection ranges of the radar sensor system are based on the angle at which the radar waves are emitted. These are extrapolated 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) and give the actual monitoring ranges.
Automatic shutoff of radar sensor system (model 216 up to 31.5.13, model 221):
Due to legal requirements on the 24 GHz radar system (short range radar) in Western Europe, the short range radar sensor system is automatically switched off in certain protected areas around radioastronomy stations. In other words the Blind Spot Assist is not functional in these ranges. The protected areas around radioastronomy stations are stored in the radar sensors control unit (with code (234) Blind Spot Assist) or in the video and radar sensor system control unit (with code (237) Active Blind Spot Assist).
On model 216 as of 1.6.13, the radar sensor system is no longer deactivated automatically. Use of the reduced frequency band range from f = 24.25 GHz to 25.65 GHz means that this is no longer necessary. Both the NATO band and the radio astronomy band are blanked out. Operation of the radar sensor system within the restricted areas of the radio astronomy stations is thereby rendered possible. Localization of the vehicle via global positioning system (GPS) is therefore also no longer necessary.
The COMAND controller unit (A40/3) sends position information from the navigation system via the central CAN, central gateway control unit and chassis CAN to 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).
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.
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) sends the "Shut off radar sensor system" request via the sensor CAN to the rear bumper radar sensors.
The request to issue the message is 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) via the chassis CAN, central gateway control unit and central CAN to the instrument cluster.
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 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". The instrument cluster sends information about the menu setting via the central CAN, central gateway control unit and chassis CAN to 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).
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 go out 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 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) sends the system readiness status or the request to issue fault messages via the chassis CAN, central gateway control unit and central CAN to the instrument cluster as well as via the chassis CAN, central gateway control unit and interior CAN to the following control units:
- Left door control unit (N69/1) (model 216) or left front door control unit (N69/1) (model 221)
- Right door control unit (N69/2) (model 216) or right front door control unit (N69/2) (model 221)
The door control units then actuate the corresponding Blind Spot Assist readiness and warning indicator.
Blind Spot Assist ready, shown on left outside mirror
If, at a speed of v ≥ 30 km/h (v ≥ 20 mph), a vehicle is located in the radar sensor system detection range, the driver receives a warning stating on which side the vehicle is in the blind spot by means of the Blind Spot Assist readiness and warning indicator lighting up red in the outside mirror. Overtaking vehicles are reliably detected 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. 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 steering column tube module (N80) reads in the switch position of the combination switch directly and sends the position via the chassis CAN to 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).
Blind Spot Assist warning indicator, shown on left outside mirror
The requirements for displaying system readiness and for issuing visual warning messages are shown in the following table:
| Operating state | 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 recognized (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 (except model 221.074/174) or 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)
- ESP® 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 or v < 120 mph
- Approval issued for active intervention by the brake system for yawing moment interface
The yawing-moment interface is integrated in the ESP control unit and it sends out a status signal to enable a 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, it requests course-correcting intervention by the brake system. The video and radar sensor system control unit sends this request via the vehicle dynamics CAN to the ESP control unit which then implements the request by actuating the traction system hydraulic unit (A7/3) accordingly. The ESP control unit selectively brakes individual wheels and guides the vehicle back onto the collision-free course.
If the driver countersteers against the intervention by the brake system (overrides the intervention by the brake system) or accelerates the vehicle, 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. Active control intervention functions from these systems result in cancellation of the 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:
- Rapid or greater loss of pressure in a tire.
Information about the tire pressure monitoring system can be found in the separate description "Tire pressure monitor, function" (with code (475) Tire pressure monitor (premium), Schrader) or "Tire pressure loss warning, function" (without code (494) USA version).
- Risk of frontal collision of vehicle with vehicle or obstacle in direction of travel within t = 2.6 s (with constant movement conditions).
- Acceleration or deceleration of vehicle in longitudinal direction and lateral acceleration of a = 4 to 6 m/s2
.
The acceleration forces are recorded by the yaw rate sensor for lateral and longitudinal acceleration (B24/15). This sensor sends the information via the vehicle dynamics CAN, ESP control unit and chassis 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). The steering column tube module reads in the data from the steering angle sensor directly and sends this data via the chassis CAN to the video and radar sensor system control unit.
The following graphics show situations in which course-correcting interventions by the brake system are suppressed.
If vehicles are in the blind spot (2) on both sides of a vehicle with Blind Spot Assist (1), a course-correcting intervention by the brake system is suppressed.
If an obstacle (8) is located at the side next to the vehicle with Blind Spot Assist (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 located on one side of a vehicle (1) with Blind Spot Assist, 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 221.0/1 as of model year 2009 up to model year 2011 with CODE 234 (Blind Spot Monitoring) MODEL 221.095/195 as of model year 2011 with CODE 234 (Blind Spot Monitoring) | PE54.71-P-2051-97SAB | |
| MODEL 221.0 (except 221.095), 221.1 (except 221.195) as of model year 2011 with CODE 237 (Active Blind Spot Assist) | PE54.71-P-2051-97SAC | ||
| MODEL 216.3 as of model year 2009 up to model year 2011 with CODE 234 (Blind Spot Monitoring) | PE54.71-P-2051-97CAB | ||
| MODEL 216.3 as of model year 2011 with CODE 237 (Active Blind Spot Assist) | PE54.71-P-2051-97CAC | ||
| Blind Spot Assist block diagram | GF54.71-P-0003-01LE | ||
| Overview of system components for Blind Spot Assist | GF54.71-P-9997LE |