Active Blind Spot Assist, function - GF54.71-P-0006FQM
MODEL 218 as of model year 2015 with CODE 237 (Active Blind Spot Assist)
Function requirements, general
- No undervoltage or overvoltage
- "Blind Spot Assist" in "Assist" menu in the instrument cluster activated
- Engine running or drive train operational
- Soiling and function test on radar sensor system completed successfully
Object recording (e.g. vehicle ahead) via the radar sensor system is based on the radar measuring procedure.
The front long range radar sensor and the front bumper DISTRONIC (DTR) sensors perform a soiling and function test after each engine start to ensure that they are functioning correctly. The function test requires an object to be located in the respective detection area (this object is used as a reference value). If a malfunction is detected or no objects (for the function test) are present in the detection range, the Active Blind Spot Assist cannot be activated. The radar sensors control unit receives the sensor signals from the front bumper DISTRONIC (DTR) sensors via radar CAN 1 and sends them via the chassis FlexRay to the front long range radar sensor. The front long range radar sensor evaluates them in combination with its own signals and, when all the radar sensors are functioning correctly, sends the "Radar sensor system operational" status via suspension FlexRay to the radar sensors control unit.
- Vehicle moving forward
- Vehicle speed: v ≥30 km/h
- No trailer operation (with CODE 550 (Trailer hitch))
Active Blind Spot Assist, general
The Active Blind Spot Assist monitors the rear and side areas of the vehicle using short range radar and, if necessary, informs the driver that an intentional lane change (turn signal active) is not recommended at this time. Active Blind Spot Assist acts - in a broader sense - as an extension of the outside mirrors. It does not release the driver of his/her obligation to perform lane changes safely on his/her own responsibility.
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
- Blind Spot Assist warning indication in the multifunction display (through "Blind Spot Assist" menu)
When the "Blind Spot Assist" menu is selected, a warning message (vehicle with Active Blind Spot Assist and vehicle detected in the right or left blind spot) is shown in the multifunction display of the instrument cluster in addition to the warning indications in the outside mirrors.
The acoustic warning is emitted through the warning buzzer that is directly actuated by the instrument cluster. Active Blind Spot Assist can additionally perform brake system interventions to correct the course, taking the surroundings of the vehicle into account. The active interventions by the brake system are performed on specific wheels and have a course-correcting effect on the 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 rear-view 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:
- Front long-range radar sensor
- DISTRONIC sensor (DTR)/left front bumper
- DISTRONIC sensor (DTR)/right front bumper
The radar sensors control unit reads in the sensor signals from the front bumper DISTRONIC (DTR) sensors over radar CAN 1, the signals from the rear bumper radar sensors over radar CAN 2 and the signals from the front long-range radar sensor over the chassis FlexRay, and evaluates these signals.
Illustration of the Blind Spot Assist principle
The following information is evaluated by the radar sensors control unit:
- Circuit 15 status
- "Blind Spot Assist" status
- Engine running or drive train operational
- Vehicle moving forward
- Vehicle speed
- Driving stage engaged
- Brake status
- Trailer recognition status (with CODE 550 (Trailer hitch))
Status of circuit 15:
The electronic ignition lock control unit sends the status of circuit 15 to the radar sensors control unit via chassis CAN 1, the chassis gateway control unit and chassis FlexRay.
"Blind Spot Assist" status:
The instrument cluster sends the status of the Blind Spot Assist to the radar sensors control unit via chassis CAN 2, chassis gateway control unit and chassis FlexRay.
Engine running or drive train operational
The CDI control unit or the ME-SFI [ME] control unit sends the "Engine running" or "Drive train operational" signal to the radar sensors control unit via the chassis CAN 1, the chassis gateway control unit and chassis FlexRay.
Vehicle in forward movement, vehicle speed:
Forward movement is defined via the wheel rotation direction. The vehicle speed is calculated from the wheel speed. The Electronic Stability Program control unit sends this information to the radar sensors control unit via chassis CAN 1, the chassis gateway control unit and chassis FlexRay. The radar sensors control unit uses it to calculate the vehicle speed and defines the direction of travel.
Engaged drive position:
The fully integrated transmission control unit sends information about the engaged gear range to the radar sensors control unit over the drive train CAN, CDI control unit or ME-SFI [ME] control unit, chassis CAN 1, chassis gateway control unit and chassis FlexRay.
Brake status:
The Electronic Stability Program control unit sends the status of the brake to the radar sensors control unit via chassis CAN 1, the chassis gateway control unit and chassis FlexRay.
Trailer recognition status (with CODE 550 (Trailer hitch)):
When a trailer is detected, the trailer recognition control unit sends the "Trailer detected" status to the radar sensors control unit via the interior CAN, front SAM control unit, chassis CAN 1, chassis gateway control unit and chassis FlexRay.
The Active Blind Spot Assist consists of the following subfunctions:
- Measuring procedure function sequence
- System and warning messages function sequence
- Function sequence for active intervention by the brake system
Measuring procedure function sequence
Vehicles are detected based on the radar measuring procedure. The radar sensors emit bundled electromagnetic waves as "primary signals". If these waves hit an object (vehicle in the blind spot), they are reflected by it and received again by the corresponding 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 monitored area is designed to be flexible and is controlled as a function of the vehicle speed. The signals from the front long-range radar sensor are received by the radar sensors control unit over the chassis FlexRay.
The radar sensors control unit reads in the sensor signals from the front bumper DISTRONIC (DTR) sensors over radar CAN 1, the signals from the rear bumper radar sensors over radar CAN 2 and the signals from the front long-range radar sensor over the chassis FlexRay, and evaluates these signals.
Detection range of radar sensor system incl. front traffic area monitoring, shown on model 218.3
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 to calculate the actual monitoring ranges.
Illustration showing actual rear monitoring range; shown is model 218.3
System and warning messages function sequence
When circuit 15 is switched on, the Blind Spot Assist warning lamp lights up red until the CDI control unit or the ME-SFI [ME] control unit sends the "Engine running" or "Drive train operational" signal. If system errors are detected, a corresponding fault message appears instead of the readiness indicator.
The radar sensors control unit sends the request to issue system, fault and warning messages over the chassis FlexRay, chassis gateway control unit and chassis CAN 2 to the instrument cluster (fault message output) and over the chassis FlexRay, chassis gateway control unit, chassis CAN 2, front SAM control unit and the interior CAN to the respective front door control unit, which then actuates the corresponding Blind Spot Assist readiness and warning indicator.
If at a speed of v ≥30 km/h a vehicle is located in the acquisition range of the radar sensor system, the driver is warned by the warning lamp for Blind Spot Assist lighting up red in the in outside mirror, on the side of which the vehicle is in the blind spot. Additionally, a warning is shown in the multifunction display of the instrument cluster. Overtaking vehicles are detected and a warning is issued regardless of their relative speed to the vehicle with Active Blind Spot Assist. Due to the short reaction time when the difference in speed is high, the warning message output sometimes does not have any added value. If the driver attempts to initiate a lane change despite the Blind Spot Assist warning lamp being on, and signals as such by operating the combination switch (setting turn signal), a single dual warning tone is also issued through the warning buzzer. The radar sensors control unit sends the request to issue an acoustic warning via chassis FlexRay, chassis gateway control unit and chassis CAN 2 to the instrument cluster. The instrument cluster actuates the warning buzzer directly. The Blind Spot Assist warning lamp flashes. If the vehicle leaves the acquisition range of the radar sensor system, the red flashing Blind Spot Assist warning lamp is switched off.
The steering column tube module control unit directly reads in the switch position of the combination switch and sends them via the chassis CAN 1, the chassis gateway control unit and chassis FlexRay to the radar sensors control unit.
Blind Spot Assist operational readiness (in outside mirror), shown on left outside mirror
Blind Spot Assist warning (in outside mirror), shown on left outside mirror
The following table contains the requirements for displaying system readiness and for showing the visual warning messages:
| Operating state | Blind Spot Assist warning lamp "Off" | Warning lamp for Blind Spot Assist lights up yellow | Warning lamp of Blind Spot Assist lights up red | Warning lamp for Blind Spot Assist flashes red |
|---|---|---|---|---|
| Circuit 15 OFF | X | |||
| Terminal 15 ON | X | |||
| Engine running or drive train operational | X | |||
| Vehicle accelerates, vehicle speed v ≥30 km/h | X | |||
| Vehicle decelerates, vehicle speed v ≥25 km/h | X | |||
| Trailer recognized (with CODE 550 (Trailer hitch)) | X | |||
| Drive position "R" engaged | X | |||
| Vehicle recognized in blind spot | X | |||
| Turn signal active, vehicle detected in blind spot | X | |||
| Course-correcting intervention by the brake system active | X | |||
| Fault in Blind Spot Assist system | X |
Additional function requirements for active intervention by the brake system
- Electronic Stability Program (ESP®) not switched to passive (except engine 157) or ESP® not shifted to "SPORT HANDLING MODE" (on engine 157)
- ESP® not in active diagnostic or roller dynamometer mode
- ESP® not in RPM/speed control mode
- Anti-lock braking system (ABS), acceleration skid control (ASR), Brake Assist System (BAS), ESP®, PRE-SAFE® brakes, electronic traction system (ETS) inactive
- Driving speed v<200 km/h
- Approval issued for active intervention by the brake system for yawing moment interface
The Electronic Stability Program control unit transmits the status of the ESP® via the chassis CAN 1, chassis gateway control unit and chassis FlexRay to the radar sensors control unit.
The yaw rate sensor for lateral and longitudinal acceleration transmits the values on vehicle longitudinal/lateral acceleration and yaw rate to the Electronic Stability Program control unit via vehicle dynamics CAN. The Electronic Stability Program control unit evaluates this data and sends it via chassis CAN 1, chassis gateway control unit and chassis FlexRay to the radar sensors control unit.
Function sequence for active intervention by the brake system
If the radar sensors control unit detects the threat of an imminent side collision with a vehicle in the blind spot, in particular during a lane change, a course-correcting intervention by the brake system is requested. For this purpose, the radar sensors control unit sends corresponding requests to the Electronic Stability Program control unit via the chassis FlexRay, chassis gateway control unit and chassis CAN 1. The Electronic Stability Program control unit then selectively brakes individual wheels and moves the vehicle back onto a collision-free course using 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 or driving safety systems ASR, BAS, ESP®, ETS, ESP® trailer stabilization (with CODE 550 (Trailer hitch)) and PRE-SAFE® brake are of a higher priority than the Active Blind Spot Assist and result in the termination of the active brake intervention.
If the ABS system is actively intervening, an Active 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
In vehicles with CODE 475 (Tire pressure monitor (premium)) Schrader, the respective tire pressure is evaluated by the tire pressure monitor control unit. The tire pressure monitor control unit sends the information about the respective tire pressure to the radar sensors control unit via chassis CAN 2, the chassis gateway control unit and chassis FlexRay. In vehicles with CODE 477 (Tire pressure loss warning (RDW)), the tire pressure is determined based on the rolling circumference. The tire pressure loss warning (RDW) system is functionally integrated in the Electronic Stability Program control unit.
- Risk of frontal collision of vehicle with vehicle or obstacle in the direction of travel with output of a collision-critical distance warning (with constant movement conditions).
- Acceleration or deceleration of the vehicle in the longitudinal direction as well as lateral acceleration of a = 4 m/s2
(at a vehicle speed of v > 120 km/h) to 6 m/s2
(at a vehicle speed of v < 80 km/h).
The acceleration forces are recorded by the yaw rate sensor for lateral and longitudinal acceleration. The yaw rate sensor for lateral and longitudinal acceleration sends the acceleration force values to the radar sensors control unit over the vehicle dynamics CAN, Electronic Stability Program control unit or the regenerative braking system control unit, chassis CAN 1, chassis gateway control unit and chassis FlexRay.
- Jerky steering motion by the driver with a steering wheel velocity > 300 °/s.
Steering movements are recorded by the steering wheel angle sensor. The steering column tube module control unit reads in the signals of the steering angle sensor directly and sends information about the steering wheel angle and the steering wheel velocity to the radar sensors control unit via chassis CAN 1, chassis gateway control unit and chassis FlexRay.
- Course-correcting steering interventions by the driver (change in steering wheel angle > 5 °) or change in specified torque as a result of depressing the accelerator pedal (change in accelerator pedal position > 10%).
The CDI control unit or the ME-SFI [ME] control unit transmits information about the accelerator pedal position to the radar sensors control unit via chassis CAN 1, chassis gateway control unit and chassis FlexRay.
Shows model 218.3
If vehicles are located very close in the blind spot on both sides of the vehicle with Active Blind Spot Assist, a course-correcting brake intervention is suppressed.
Shows model 218.3
If an obstacle is located at the side next to the vehicle with Active Blind Spot Assist, the position of which cannot be determined, a course-correcting intervention by the brake system in the direction of the obstacle is suppressed.
Shows model 218.3
If a stationary obstacle is detected very close on one side of the vehicle with Active Blind Spot Assist, a course-correcting intervention by the brake system in the direction of the obstacle is suppressed.
Shows model 218.3
In the event of an imminent risk of collision with a vehicle in front and a vehicle in the blind spot, a course-correcting intervention by the brake system is suppressed.
An acoustic warning is not issued!
Shows model 218.3
In the event of an imminent risk of collision with a stationary obstacle and a vehicle in the blind spot, a course-correcting intervention by the brake system is suppressed.
An acoustic warning is not issued!
Shows model 218.3
In the case of oncoming traffic, course-correcting intervention by the brake system is limited so that any collision with oncoming traffic is avoided.
| Electrical function schematic, Active Blind Spot Assist | PE54.71-P-2055-97XAA |
| Overview of system components for driver assistance systems | GF54.00-P-9998FQM |