Active Blind Spot Assist, function - GF54.71-P-0006CAM
MODEL 207.3/4 as of model year 2014 with CODE 237 (Active Blind Spot Assist)
Function requirements, general
The units and values given in the following text for the speed must be assigned to the possible national versions. The details in "miles per hour (mph)" refer to vehicles with a miles indicator.
- No undervoltage or overvoltage
- "Blind Spot Assist" in "Assist" menu in the instrument cluster activated
- Engine running or drivetrain operational
- Vehicle moving forward
- Vehicle speed v ≥30 km/h (v ≥20 mph)
- No trailer operation (with code (550) trailer hitch)
Blind Spot Assist, general
The Active Blind Spot Assist monitors the rear and side area of the vehicle using 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 broader sense, the Active 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.
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 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 in 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. Active interventions by the brake system are conducted on a wheel-specific basis and exert a course-correcting influence 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 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:
- 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 signals from the front bumper DISTRONIC (DTR) sensors via radar CAN 1, the signals from the rear bumper radar sensors via radar CAN 2 and the signals from the front long-range radar sensor via 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:
- Terminal status of terminal 15
- "Blind Spot Assist" status
- Engine running or drivetrain 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, the chassis gateway control unit and chassis FlexRay.
Engine running or drivetrain operational
The CDI control unit or the ME-SFI control unit sends the "Engine running" or "Drivetrain operational" signal to the radar sensors control unit via 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 on the basis of the wheel speeds. 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 via the drive train CAN, CDI control unit or ME-SFI 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
The vehicles are recorded based on the radar measuring method. The radar sensors emit pooled electromagnetic waves as so-called primary signals. If these waves hit an object (e.g. a vehicle in the blind spot), they are reflected from 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 front bumper DISTRONIC (DTR) sensors are designed as ultra-wideband radar sensors with the following properties:
- Acquisition range s = 0.18 to 30 m
- Detection angle: ∠= 80° with angle measurement and ∠= 130° only detection (tracking)
- Carrier frequency: f = 25 GHz
- Method of operation: Short pulse method with f = 1.4 GHz band width
The area up to a maximum of s = 200 m in front of the vehicle is monitored by the front long-range radar sensor. The long-range radar sensor operates based on the pulse Doppler principle with the following properties:
- Detection range: s = 0 to 200 m
- Detection angle: ∠= 18° (medium range) and ∠= 60° (long range)
- Carrier frequency: f = 77 GHz
The detection range is designed to be flexible and is controlled as a function of the vehicle speed.
The radar sensors control unit reads in the signals from the front bumper DISTRONIC (DTR) sensors via radar CAN 1, the signals from the rear bumper radar sensors via radar CAN 2 and the signals from the front long-range radar sensor via the chassis FlexRay, and evaluates these signals.
Recording range of radar sensor system incl. front road space monitoring
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
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 error is detected, a corresponding message is shown on the instrument cluster and the Blind Spot Assist readiness and warning indicators light up yellow.
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.
The request to issue system and warning messages is sent by the radar sensors control unit to the instrument cluster via the chassis FlexRay, chassis gateway control unit and chassis CAN 2 and to the left front door control unit or the right front door control unit via the chassis FlexRay, chassis gateway control unit, chassis CAN 2, front SAM control unit and interior CAN. The left front door control unit or the right front door control unit then actuates the corresponding Blind Spot Assist readiness and warning indicator.
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 by means of illumination of the red Blind Spot Assist readiness and warning indicator in the outside mirror on the side of the vehicle on which the vehicle is in the blind spot. Additionally, a warning is shown in the multifunction display of the instrument cluster. When vehicles are passing, they are recognized 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, 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 double warning tone is additionally issued once by the 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 switch position of the combination switch is read in directly by the steering column tube module control unit and sent to the radar sensors control unit via chassis CAN 1, the chassis gateway control unit and chassis FlexRay.
Blind Spot Assist readiness indicator; illustration shows left outside mirror
Blind Spot Assist warning indicator, shown on left outside mirror
The requirements for display of system readiness and for output of visual warning messages are listed 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 or drivetrain operational | X | |||
| Vehicle accelerates, vehicle speed v ≥30 km/h (v ≥20 mph) | X | |||
| Vehicle decelerates, vehicle speed v ≤25 km/h (v ≤15 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 | 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 mode
- ESP® not in active diagnostic or roller dynamometer mode
- Anti-lock braking system (ABS), acceleration skid control (ASR), Brake Assist System (BAS), ESP ®, PRESAFE brake inactive
- Vehicle speed v < 200 km/h (v < 120 mph)
- No active control intervention function in brake assistance systems
- Approval issued for active intervention by the brake system for yawing moment interface
The yawing-moment interface is integrated in the Electronic Stability Program control unit and sends out a status signal to enable a course-correcting braking torque.
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 and the driving safety systems ASR, BAS, ESP®, ETS, ESP® trailer stabilization 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), 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.
Detailed 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)) or "Tire pressure loss warning, function" (with code (477) Tire pressure loss warning).
- 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 (v > 75 mph)) to 6 m/s2
(at a vehicle speed of v < 80 km/h (v > 50 mph)).
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, Electronic Stability Program 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 angle sensor. The steering column tube module control unit reads in the signals from the steering angle sensor directly and sends the information about the steering angle and the steering wheel velocity to the radar sensors control unit via chassis CAN 1, the chassis gateway control unit and chassis FlexRay.
- Course-correcting steering interventions by the driver (change in steering wheel angle of > 5 °) or change in specified torque as a result of depressing the accelerator pedal (change in accelerator pedal position of > 10%)
The accelerator pedal changes are recorded by the accelerator pedal sensor. The CDI control unit or the ME-SFI control unit reads in the signals from the accelerator pedal sensor directly and sends them to the radar sensors control unit via chassis CAN 1, the chassis gateway control unit and chassis FlexRay.
If vehicles are located very close in the blind spot (2) on both sides of the vehicle with Active Blind Spot Assist (1), a course-correcting brake intervention is suppressed.
If an obstacle (8) is located at the side next to the vehicle with Active 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 detected very close on one side of the vehicle with Active Blind Spot Assist (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 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-2055-97EAA | ||
| Overview of system components for driver assistance systems | GF54.00-P-9998CAM |