Active Blind Spot Assist, Function - GF54.71-P-0006RF
Model 205
up to model year 2019
with code 237 (Active Blind Spot Assist)
Model 253 (except 253.99)
up to model year 2020
with code 237 (Active Blind Spot Assist)
Function requirements, general
- No undervoltage or overvoltage
- "Blind Spot Assist" activated in "Assist" menu in the instrument cluster.
- Engine running or drive train operational.
- Front radar sensor system soiling and function test 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 front 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 in the respective detection area to be used for reference. If a malfunction is established or if there are no objects in the detection area, the Active Blind Spot Assist cannot be activated. The radar sensors control unit receives the signals of the front bumper radar sensors via the radar-CAN 1 and sends them over 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 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))
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. In a broader sense, Active Blind Spot Assist acts as an extension of the outside mirrors and 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 readiness and warning indicator
- Right Blind Spot Assist readiness and warning indicator
- Blind Spot Assist warning indication in the multifunction display (via the "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 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 that cannot be observed via the outside mirrors is monitored by the following components:
- Left rear bumper radar sensor
- Right rear bumper radar sensor
To avoid collisions with other road users (incl. oncoming traffic) because of a possible change in course, the course-correcting intervention requires the road space in front of the vehicle to be monitored.
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 Active Blind Spot Assist, shown on model 205.0
The following information is evaluated by the radar sensors control unit:
- Terminal status of terminal 15
- "Active Blind Spot Assist" status
- Engine running or drive train operational
- Vehicle moving forward
- Vehicle speed
- Driving stage engaged
- Brake status
- Status of trailer recognition (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.
Active 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, drivetrain 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 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, drivetrain 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 205.0
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 the rear monitoring range, shown on model 205.0
Function sequence for system and warning messages
When circuit 15 is switched on, the Blind Spot Assist readiness and warning indicators light up red until the CDI control unit or the ME-SFI [ME] control unit sends the "Engine running or drive train 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 multifunction display of 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 to issue system, fault and warning messages over the chassis FlexRay, electronic ignition lock control unit and user interface CAN to the instrument cluster (fault message output) and over the chassis FlexRay, electronic ignition lock control unit and 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 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. 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, despite illumination of the Blind Spot Assist readiness and warning lamp, the driver still attempts to change lane and indicates this by operating the combination switch (turn signal active), a double warning tone is additionally issued once by the instrument cluster speaker. 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 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
The "OFF" functional state display (11) is output when the Active Blind Spot Assist is deactivated and in the case of a fault.
When the Active Blind Spot Assist is switched on via the "Assistance" menu in the instrument cluster, function status "On" (12) is displayed. The Active Blind Spot Assist is activated but not ready to issue warnings, as the additional function requirements such as a vehicle speed of v > 30 km/h are not given. When the function status "Operational" (13) 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 indication in the multifunction display
Blind Spot Assist warning indication (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 indication 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 indication in the outside mirror, red on | Blind Spot Assist warning indication in the outside mirror, flashing red |
|---|---|---|---|---|---|
| Circuit 15 OFF | X | ||||
| Terminal 15 ON | X | ||||
| Engine running or drive train operational | X | ||||
| Active Blind Spot Assist activated via the 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 detected | 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
- 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
- Driving speed v<200 km/h
- 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 internally issues a signal to enable a course-correcting braking torque.
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 lateral and longitudinal acceleration is detected by the acceleration sensor integrated into the supplemental restraint system control unit. The supplemental restraint system control unit sends the corresponding values via the vehicle dynamics CAN to the Electronic Stability Program control unit. 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 the corresponding request to the Electronic Stability Program control unit over the 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 driver 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 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) (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 detected by the acceleration sensor integrated into the supplemental restraint system control unit. The supplemental restraint system control unit sends the acceleration force values over the vehicle dynamics CAN, Electronic Stability Program control unit and chassis FlexRay to the radar sensors control unit.
- 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 steering wheel angle sensor signals 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 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 the drive train CAN and the chassis FlexRay.
Shown: Model 205.0
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.
Shown: Model 205.0
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.
Shown: Model 205.0
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.
Shown: Model 205.0
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.
No warning tone is issued!
Shown: Model 205.0
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.
No warning tone is issued!
Shown: Model 205.0
In the case of oncoming traffic, a course-correcting brake application is limited so that a collision with oncoming traffic (9) is avoided.
| Electrical function schematic, Active Blind Spot Assist | PE54.71-P-2055-97FBA | ||
| Overview of system components for driver assistance systems | Model 205 up to model year 2019 with code 237 (Active Blind Spot Assist) Model 253 (except 253.99) up to model year 2020 with code 237 (Active Blind Spot Assist) |
GF54.00-P-9998RF |