Active Blind Spot Assist, Function - GF54.71-P-0006RFM
Model 205
as of model year 2019
with code 23P (Driving Assistance package)
Model 253 (except 253.99)
as of model year 2020
with code 23P (Driving Assistance package)
Function requirements, general
- No undervoltage or overvoltage
- 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 close and long range radar sensor and the rear outer 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 (long range only) in the detection area. If a malfunction is established or if there are no objects in the detection area, the Active Blind Spot Assist cannot be activated. The Mercedes-Benz Intelligent Drive control unit receives the signals of the outer rear bumper radar sensors via the radar CAN 2 and sends them via the suspension FlexRay to the short and long-range radar sensor. The short and 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 over the suspension FlexRay to the Mercedes-Benz Intelligent Drive control unit.
- No trailer operation (with code 550 (Trailer hitch))
- Applies to all functions except exit warning:
- Engine running or drive train operational.
- Vehicle moving forward
- Vehicle speed: v > 12 km/h (approx.)
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, the Active Blind Spot Assist also acts as an extension of the outside mirrors and the inside rearview mirror. It does not release the driver of his/her obligation to perform lane changes safely on his/her own responsibility.
When the vehicle is stationary, the Active Blind Spot Assist also monitors the rear and side areas of the vehicle using short range radar and issues exit warnings when necessary. This, too, does not release the vehicle occupants from their obligation to exit safely on their own responsibility.
Active Blind Spot Assist is activated through the head unit. The following options are available for navigating in the control menu:
- Except code 446 (Touchpad only), navigation can be performed using the Audio/COMAND control panel. The Audio/COMAND control panel transmits the relevant control signals via the telematics CAN to the head unit.
- With code 446 (Touchpad only) or code 448 (Touchpad), navigation can be performed using the touchpad. The touchpad sends the relevant operation signals to the head unit via the telematics CAN.
- The navigation can occur with code 531 (COMAND APS) per voice control. The driver hands-free system microphone is read directly by the head unit.
- Navigation can be performed via the head unit finger navigation pad and the "Back" button on the steering wheel. The head unit finger navigation pad and the "Back" button transmit the relevant control signals via the steering wheel electronics, the steering wheel CAN, the steering column tube module control unit, the suspension FlexRay, the electronic ignition lock control unit and the user interface CAN to the head unit.
- The operating menu can be called up on the upper control panel control unit via the vehicle button. The status of the Vehicle button is sent by the upper control panel control unit over the LCP-LIN, the Audio/COMAND control panel (except code 446 (Touchpad only)) or touchpad (with code 446 (Touchpad only)) and the telematics CAN to the head unit.
The head unit sends the status of the Active Blind Spot Assist over the user interface CAN, electronic ignition lock control unit and the suspension FlexRay to the Mercedes-Benz Intelligent Drive control unit.
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
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. The readiness indicator is shown on 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:
- Right outer rear bumper radar sensor
- Left outer rear bumper radar sensor
To avoid collisions with other road users (incl. oncoming traffic) as a result of a possible change in direction, monitoring of the road space in front of the vehicle is a mandatory requirement for course-correcting interventions.
Monitoring of the road in front of the vehicle is performed by the following components:
- Short and long-range radar sensor
- Stereo multifunction camera (only with availability)
The Mercedes-Benz Intelligent Drive control unit reads in the signals from the left and right outer rear bumper radar sensors over radar CAN 2, the signals from the short and long-range radar sensor and stereo multifunction camera over the suspension FlexRay and evaluates them. The short-range and long-range radar sensor is heated by a radome heater that it actuates directly.
Illustration of the principle of Blind Spot Assist, shown on model 205.0
The following information is evaluated by the Mercedes-Benz Intelligent Drive control unit and other control units:
- Terminal status of terminal 15
- "Active Blind Spot Assist" status
- Engine running or drive train operational
- Vehicle moving forward
- Vehicle speed
- Steering wheel angle and steering wheel velocity
- Driving stage engaged
- Brake status
- Trailer operation status (with code 550 (Trailer hitch))
Status of circuit:
The electronic ignition lock control unit sends the status of circuit 15 over the suspension FlexRay to the Mercedes-Benz Intelligent Drive control unit.
"Active Blind Spot Assist" status:
The head unit sends the status of the Active Blind Spot Assist over the user interface CAN, electronic ignition lock control unit and the suspension FlexRay to the Mercedes-Benz Intelligent Drive control unit.
Engine running or drive train operational:
The CDI control unit or the ME-SFI control unit sends the "Engine running" or "Drivetrain operational" signal to the Mercedes-Benz Intelligent Drive control unit via drive CAN, powertrain control unit and suspension 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 Mercedes-Benz Intelligent Drive control unit over the suspension FlexRay. The Mercedes-Benz Intelligent Drive control unit uses it to calculate the vehicle speed and define the direction of travel.
Steering wheel angle and steering wheel velocity:
The steering wheel angle sensor measures the steering wheel angle and the steering wheel velocity. The steering column tube module control unit directly reads in the signals of the steering wheel angle sensor and sends information to the Mercedes-Benz Intelligent Drive control unit over the suspension FlexRay.
Engaged drive position:
The fully integrated transmission control unit (transmission 722, 724, 725) transmits information about the selected gear range via the drive train CAN, the powertrain control unit and the chassis FlexRay to the Mercedes-Benz Intelligent Drive control unit.
Brake status:
The Electronic Stability Program control unit sends the status of the brake to the Mercedes-Benz Intelligent Drive control unit over the suspension FlexRay.
Trailer recognition (with code 550 (Trailer hitch)):
When a trailer is detected, the trailer recognition control unit sends the "Trailer detected" status to the Mercedes-Benz Intelligent Drive control unit over the interior CAN, electronic ignition lock control unit and suspension 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
- Exit warning function sequence
Measuring procedure function sequence
Vehicles are detected based on the radar measuring method and the video data from the stereo multifunction camera.
Bike riders are also detected.
The radar sensors emit bundled electromagnetic waves as "primary signals". If these impact on an object they are then reflected by it and received by the 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 Mercedes-Benz Intelligent Drive control unit reads in the signals from the rear bumper radar sensors over radar CAN 2 and the signals from the short and long-range radar sensor over the suspension FlexRay and evaluates them.
The stereo multifunction camera consists of two high-resolution mono cameras and an integrated control unit. The laterally offset location of the two mono cameras creates a difference in perspective (parallax displacement) between the left and right optical path. The distance to the object ahead recorded by the camera and other variables such as the height thereof are calculated on the basis of the differences between the image data.
The stereo multifunction camera detects objects and tracks. Objects are classified as types of object and their speed and elongation are determined.
The integrated control unit evaluates image data from the two mono cameras, processes it and sends the corresponding data over the suspension FlexRay to the Mercedes-Benz Intelligent Drive control unit. The Mercedes-Benz Intelligent Drive control unit compares the image data with the signals from the radar sensor system.
Detection range of radar sensor system incl. front traffic area monitoring, shown on model 205.0
Function sequence for system and warning messages
With the activation of circuit 15, the Blind Spot Assist warning indicators illuminate in red until the "Engine running" or "Drivetrain operational" signal is received. 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 Mercedes-Benz Intelligent Drive control unit transmits the request to output system, fault and warning messages via the suspension FlexRay, electronic ignition lock control unit and user interface CAN to the instrument cluster (fault messages output) and via the suspension FlexRay, electronic ignition lock control unit and interior CAN to the respective front door control unit, which then actuates the relevant Blind Spot Assist readiness and warning display. The request to issue warning tones is sent by the Mercedes-Benz Intelligent Drive control unit via the suspension FlexRay, the electronic ignition lock control unit and the user interface CAN to the instrument cluster, which directly actuates the instrument cluster speaker.
If a vehicle is located in the left rear (3) or right rear (4) detection range of the radar sensor system, the driver is warned by the readiness and warning display for the Blind Spot Assist lighting up red in the outside mirror on the side where the vehicle is located 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 readiness and warning display lighting up, and signals this by operating the combination switch (operating the turn signal indicator), a single dual warning tone is also issued via the instrument cluster speaker when the vehicle is in the immediate vicinity of the systems vehicle. 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 Mercedes-Benz Intelligent Drive 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 as long as not all function requirements are fulfilled. The Active Blind Spot Assist is active, but not ready to issue a warning. 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 indicator in the multifunction display, shown on model 205.0
Blind Spot Assist readiness and warning display, 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 readiness and warning display 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 readiness and warning display in the outside mirror lights up red | Blind Spot Assist readiness and warning display in the outside mirror flashes 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 ≥ 7 km/h (approx.) | 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 set, vehicle in immediate vicinity to systems vehicle | 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: The Electronic Stability Program control unit sends the ESP® status over the suspension FlexRay to the Mercedes-Benz Intelligent Drive control unit.
- 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), Active Brake Assist with cross-traffic function, ESP®, electronic traction system (ETS) or Trailer Stability Assist (TSA) not active
- Vehicle speed v > 30 km/h and v < 200 km/h:
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 these data and transmits them via the suspension FlexRay to the Mercedes-Benz Intelligent Drive control unit.
- 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.
Function sequence for active intervention by the brake system
If the Mercedes-Benz Intelligent Drive 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 brake application is requested.
The Mercedes-Benz Intelligent Drive control unit sends the corresponding request to the Electronic Stability Program control unit over the suspension 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 against 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 the driving safety systems "acceleration slip regulation (ASR)", "Active Brake Assist with cross-traffic function", "ESP®" and "electronic traction system (ETS)" have a higher priority than the Active Blind Spot Assist and they cancel an active intervention by the brake system.
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 monitoring system control unit sends information on the respective tire pressure to the Mercedes-Benz Intelligent Drive control unit over the user interface CAN, electronic ignition lock control unit and suspension 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 system is functionally integrated into the Electronic Stability Program control unit, which sends the information on tire pressure over the suspension FlexRay to the Mercedes-Benz Intelligent Drive 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).
- Strong vehicle acceleration or strong deceleration in longitudinal direction as well as lateral acceleration.
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 suspension FlexRay to the Mercedes-Benz Intelligent Drive control unit.
- Abrupt steering maneuvers by driver with a steering wheel velocity. Steering movements are recorded by the steering wheel angle sensor. The steering column tube module control unit directly reads in the signals of the steering wheel angle sensor and transmits information on the steering wheel angle and the steering wheel velocity via the suspension FlexRay to the Mercedes-Benz Intelligent Drive control unit.
- Course correcting steering interventions by driver or change in specified torque through operation of the accelerator pedal.
The CDI control unit or the ME-SFI control unit transmits information about the accelerator pedal position to the Mercedes-Benz Intelligent Drive control unit over the drive CAN, powertrain control unit and the suspension FlexRay.
Additional function requirements for exit warning
- Active Blind Spot Assist is activated.
- Vehicle stationary
- The parked vehicle is not locked.
- The run-on time of 3 min after the engine is switched off (circuit 15 OFF) has not yet passed.
Before the system is switched off, the Blind Spot Assist warning displays flash 3 times.
Exit warning function sequence
The exit warning function is deactivated as soon as the vehicle comes to a standstill. The system remains operational for 3 min after the engine is switched off.
The respective Blind Spot Assist readiness and warning display lights up as soon and for as long as a vehicle is detected in the core zone of the detection range (warning level 1). If a door is opened on the corresponding side during this time, the respective Blind Spot Assist readiness and warning display flashes and a warning tone is output (warning level 2). With code 877 (Ambient lighting), the ambient lighting of the respective door is switched on and flashes red at warning level 2 in addition. Closing the respective door ends warning level 2.
The rear bumper radar sensors transmit object recognition signals in the respective detection range via radar CAN 2 to the Mercedes-Benz Intelligent Drive control unit.
The front door control units and the rear door control units transmit the door status via the interior CAN, electronic ignition lock control unit and suspension FlexRay to the Mercedes-Benz Intelligent Drive control unit. The Mercedes-Benz Intelligent Drive control unit transmits the request to output the warning messages via the suspension 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 display. The request to issue warning tones is sent by the Mercedes-Benz Intelligent Drive control unit via the suspension FlexRay, the electronic ignition lock control unit and the user interface CAN to the instrument cluster, which directly actuates the instrument cluster speaker. The Mercedes-Benz Intelligent Drive control unit transmits the request to switch on the ambient lighting in the door via the suspension FlexRay, electronic ignition lock control unit and interior CAN to the ambient lighting control unit (with code 877 (Ambient lighting)).
| Electrical function schematic, Active Blind Spot Assist | PE54.71-P-2055-97FBB | ||
| Overview of system components for driver assistance systems | GF54.00-P-9998RFM |