Active Blind Spot Assist, Function - GF54.71-P-0006LF
Model 217, 222
up to model year 2018
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 detection (e.g. vehicle directly ahead) through the radar sensor system is based on the radar measuring procedure. The front long range radar sensor and the bumper radar 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 for the function check). 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 front bumper radar sensors send corresponding signals via radar CAN 1, radar sensors control unit and chassis FlexRay to the front long range radar sensor. The front long range radar sensor evaluates these with its own signals and, when all the radar sensors are functioning correctly, sends the "Radar sensor system operational" status via chassis FlexRay to the radar sensors control unit.
- Vehicle moving forward
- Vehicle speed: v ≥ 30 km/h
- No trailer operation (with CODE 550 (Trailer hitch))
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. In a broader sense, Active Blind Spot Assist serves as an extension of the inside rearview mirror. 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 warning lamp
- Right Blind Spot Assist warning lamp
- Blind Spot Assist warning indicator in the instrument cluster
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 instrument cluster in addition to the warning indications in the outside mirrors.
The acoustic warning is output over the instrument cluster speaker 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
- Left front bumper radar sensor
- Right front bumper radar sensor
The radar sensors control unit reads in and evaluates the signals of the front bumper radar sensors over radar CAN 1, the signals of the rear bumper radar sensors over radar CAN 2 and the signals of the front long-range radar sensor over the chassis FlexRay.
Illustration of the principle of Blind Spot Assist, shown on model 222.0
The following information is evaluated by the radar sensors control unit:
- Terminal status of terminal 15
- "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 over the chassis FlexRay.
Blind Spot Assist status
The instrument cluster sends the status of Blind Spot Assist to the radar sensors control unit via user interface CAN, electronic ignition lock 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 drive train CAN, powertrain 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 on the basis of the wheel speeds. The Electronic Stability Program control unit sends this information to the radar sensors control unit via 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 selected gear range via drive train CAN, powertrain control unit and suspension FlexRay to the radar sensors control unit.
Brake status:
The Electronic Stability Program control unit sends the status of the brake to the radar sensors control unit via 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 over the interior CAN, electronic ignition lock control unit and chassis FlexRay.
The Active Blind Spot Assist consists of the following subfunctions:
- Measuring procedure function sequence
- Function sequence for system and warning messages
- Function sequence for active intervention by the brake system
Measuring procedure function sequence
Vehicles are detected based on the radar measuring method. 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 and evaluates the signals of the front bumper radar sensors over radar CAN 1, the signals of the rear bumper radar sensors over radar CAN 2 and the signals of the front long-range radar sensor over the chassis FlexRay.
Detection range of radar sensor system incl. front traffic area monitoring, shown on model 222.0
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 on model 222.0
Function sequence for system and warning messages
When circuit 15 is switched on, the Blind Spot Assist warning lamps light up red until the CDI control unit or the ME-SFI control unit sends the "Engine running" or "Drivetrain operational" signal. Additionally, when the "Assistance" menu is switched on in the instrument cluster, the readiness of the Active Blind Spot Assist is shown in the instrument cluster (gray radar waves appear spreading towards the rear next to the vehicle). If system errors are detected, a corresponding fault message appears instead of the readiness indicator.
The radar sensors control unit sends the request for output of system, fault and warning messages via chassis FlexRay, electronic ignition lock control unit and user interface CAN to the instrument cluster (warning messages output), and via chassis FlexRay, electronic ignition lock control unit and interior CAN to the relevant front door control unit, which then actuates the corresponding Blind Spot Assist warning lamp.
If at a speed of v ≥ 30 km/h a vehicle is located in the detection range of the radar sensor system, the driver is warned by the Blind Spot Assist warning lamp lighting up red in the outside mirror on the side where the vehicle is in the blind spot. In addition, a warning is displayed in 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 instrument cluster speaker. 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 reads in the switch position of the combination switch directly, and sends it over the suspension FlexRay to the radar sensors control unit.
Blind Spot Assist readiness indicator (in instrument cluster), shown on model 222
The function status "Off" display is shown when the Active Blind Spot Assist is deactivated and in the event of a fault.
When the Active Blind Spot Assist is switched on via the "Assistance" menu in the instrument cluster, function status "On" is displayed. Active Blind Spot Assist is activated, but not ready to issue warnings, as additional function requirements, such as e.g. a vehicle speed of v > 30 km/h, are not satisfied. When the function status "Operational" is issued by instrument cluster, the Active Blind Spot Assist is switched on and all additional function requirements are met. The Active Blind Spot Assist is ready to issue a warning.
Blind Spot Assist warning indicator in instrument cluster, shown on model 222.0
Blind Spot Assist warning lamp (in the 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 lamps in the outside mirror "Off" | Blind Spot Assist readiness indicator in the instrument cluster, function status "On" | Blind Spot Assist readiness indicator in the instrument cluster, function status "Operational" | Blind Spot Assist warning lamp in outside mirror lights up red | Blind Spot Assist warning lamp in outside mirror flashes red |
|---|---|---|---|---|---|
| Circuit 15 OFF | X | ||||
| Terminal 15 ON | X | ||||
| Engine running or drive train operational | X | ||||
| Blind Spot Assist function activated via instrument cluster | X | ||||
| Vehicle accelerates, vehicle speed v ≥ 30 km/h | X | X | |||
| Vehicle decelerates, vehicle speed v ≤ 25 km/h | X | X | |||
| Trailer recognized (with CODE 550 (Trailer hitch)) | X | ||||
| Drive position "R" engaged | X | X | |||
| Vehicle recognized in blind spot | X | X | |||
| Turn signal active, vehicle detected in blind spot | X | 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 passively connected (except model 222.077/177/178/179) or ESP® not shifted to "SPORT HANDLING MODE" (model 222.077/177/178/179)
- 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® brake, electronic traction system (ETS) or Trailer Stability Assist (TSA) not active
- Vehicle speed v < 200 km/h
- Approval issued for active intervention by the brake system for yawing moment interface
The Electronic Stability Program control unit sends the status of the Electronic Stability Program® via the suspension FlexRay to the radar sensors control unit.
The turn rate, lateral acceleration and longitudinal acceleration sensor sends the values for vehicle longitudinal and lateral acceleration and yaw rate to the Electronic Stability Program control unit via the vehicle dynamics CAN. The Electronic Stability Program control unit evaluates this data and sends it over the 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. The radar sensors control unit sends corresponding requests to the Electronic Stability Program control unit via chassis FlexRay. 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
On vehicles with CODE 475 (Tire pressure monitor), the respective tire pressure is evaluated by the tire pressure monitor control unit. The tire pressure monitor control unit sends the information on the respective tire pressure to the radar sensors control unit over the user interface CAN, electronic ignition lock control unit and chassis FlexRay. On vehicles with CODE 477 (Tire pressure loss warning), the tire pressure is determined based on the rolling circumference. The Electronic Stability Program control unit sends the relevant tire pressure loss warning to the radar sensors control unit via chassis FlexRay. The tire pressure loss warning 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 and lateral acceleration of a = 4 m/s2
(at a vehicle speed v > 120 km/h) to 6 m/s2
(at a vehicle speed 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 via the vehicle dynamics CAN, the Electronic Stability Program control unit and the suspension FlexRay.
- Sudden steering movements 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 steering wheel angle sensor data directly and sends information on the steering wheel angle and steering wheel velocity to the radar sensors control unit via chassis FlexRay.
- Course-correcting steering interventions by the driver (change in steering wheel angle > 5°) or change in specified torque by pressing the accelerator pedal (accelerator pedal change > 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 the drive train CAN and the chassis FlexRay.
Shown model 222.0
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.
Shown model 222.0
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.
Shown model 222.0
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.
Shown model 222.0
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.
No warning tone is issued!
Shown model 222.0
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.
No warning tone is issued!
Shown model 222.0
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-2055-97SEA | ||
| Overview of system components for driver assistance systems | GF54.00-P-9998LF |