Active Lane Keeping Assist, Function - GF54.71-P-0004FQ
MODEL 218
up to year 2015
with CODE 238 (Active lane keeping Assist)
Up to 28.02.2013
As of 01.03.2013
Function requirements, general
- Terminal 15 ON
- Function enabled in instrument cluster
- Vehicle moving forward
- Vehicle speed v = 60 bis 270 km/h
- Recognizable lane markings present on both sides (no construction site markings (yellow/white), no snow, not covered up, etc.; in other words, contrast too low)
- Radius of curve r >150 m
- Track width s = 2.5 to 4.6 m (excepted are track widths of s > 3.9 m, that are driven at a speed of v < 100 km/h)
On vehicles up to 28.02.2013, the electronic ignition lock control unit sends the status of circuit 15 to the multifunction camera and to the video and radar sensor system control unit via the chassis CAN. On vehicles as of 01.03.2013, the electronic ignition lock control unit sends the status of circuit 15 to the video and radar sensor system control unit via chassis CAN 1 and to the multifunction camera via chassis CAN 1, the front SAM control unit and chassis CAN 2.
shown on model 221
Active Lane Keeping Assist, general
The Active Lane Keeping Assist detects any unintentional driving across lane markings and issues a haptic warning to the driver in certain situations by initiating vibrations on the steering wheel. Crossing over lane markings is optically recorded and processed by the multifunction camera. The haptic warning is generated by the steering wheel vibration motor. Active Lane Keeping Assist takes the driver's behavior into consideration and decides the point at which a warning is to be issued. If the driver fails to react to the warning, specific interventions by the brake system are authorized from the video and radar sensor system control unit to return the vehicle to the road lane.
On model 218.9 and model 218.3 as of 01.06.2012, the driver has the option of setting the sensitivity of the Active Lane Keeping Assist system in the "Assistance" menu in the instrument cluster.
The following operating modes can be selected:
- Standard (sensitivity high, warnings issued earlier and more frequently)
- Adaptive (sensitivity low, warnings issued later and less often)
If the driver indicates that he/she is "active" before or during the intervention by the brake system, the intervention by the brake system is suppressed or canceled.
During active control of the anti-lock braking system (ABS), acceleration skid control (ASR) and Brake Assist System (BAS), or during brake intervention by PRE-SAFE® or by the Active Blind Spot Assist, brake intervention by the Active Lane Keeping Assist is suppressed or canceled immediately.
Warnings are issued as soon as the vehicle is in the direct vicinity of a broken or solid line or crosses over it.
Brake application only occurs when a solid line is crossed over (lane barrier) at an angle of ∠ < 3° and if the lane is restricted by two lane markings. By contrast, a warning is always issued when a broken line is crossed over.
Active Lane Keeping Assist operates on a speed-dependent basis and therefore requires the vehicle speed to be calculated. The vehicle speed is calculated on the basis of the wheel speeds. The direction of travel is defined using the wheel rotation direction. The wheel speeds and the wheel rotation directions are detected by the RPM sensors. On vehicles up to 28.02.2013, the Electronic Stability Program control unit reads in the signals from the RPM sensors directly and sends them to the instrument cluster and to the video and radar sensor system control unit via the chassis CAN. On vehicles as of 01.03.2013, the Electronic Stability Program control unit sends the signals from the RPM sensors to the video and radar sensor system control unit via chassis CAN 1 and to the instrument cluster via chassis CAN 1, front SAM control unit and chassis CAN 2. The instrument cluster calculates the vehicle speed and sends it to the multifunction camera via the chassis CAN (up to 28.02.2013) or chassis CAN 2 (as of 01.03.2013). The video and radar sensor system control unit calculates the vehicle speed itself and defines the direction of travel.
The Active Lane Keeping Assist comprises the following subfunctions:
- Function sequence for lane recognition
- Function sequence for recognition of driver activity
- Function sequence for recognition of control interventions
- Function sequence for issuing warning
- Function sequence for active intervention by the brake system
Function sequence for lane recognition
The multifunction camera is attached at the top center of the windshield. It optically captures the road area in front of the vehicle. For this purpose, the multifunction camera records images of the lane at a fixed scanning rate and makes these images available to the integrated control unit. When doing so, the multifunction camera measures the lane based on the lane markings. The multifunction camera also sends the picture data to the video and radar sensor system control unit via a low voltage differential signal (LVDS) line.
Schematic of lane recognition by multifunction camera
Based on the recorded image sequences and the measurement values resulting from the images of the lane markings, the multifunction camera and the video and radar sensor system control unit each calculate a lane independently of each other. These calculations are based on corresponding algorithms. This data is then used by the multifunction camera and the video and radar sensor system control unit to determine the relative position of the vehicle in the lane. The Active Lane Keeping Assist measures are all derived from this position. No lane information can be issued in cases where there are no lane markings or if they are not visible (e.g. owing to dirt or snow), where there is a low contrast between the road surface and the lane markings or where there is a high level of glare.
For multiple markings on the traffic lane, the inner marking is always taken as the reference point.
In construction site areas, the Active Lane Keeping Assist function may not be able to issue warnings due to multiple markings.
The instrument cluster multifunction display continuously shows the current status of the Active Lane Keeping Assist, in particular its warning readiness. This status information is sent by the multifunction camera to the instrument cluster via the chassis CAN (up to 28.02.2013) or chassis CAN 2 (as of 01.03.2013).
Possible displays:
- Function status
- Icon off: Active Lane Keeping Assist deactivated
- Icon yellow (1): Active Lane Keeping Assist activated, but not ready to issue warnings (e.g. v < 60 km/h)
- Warning readiness
- Icon green (2): Active Lane Keeping Assist activated and ready to issue warnings
- Message in multifunction display for faults
Function sequence for recognition of driver activity
The following situations suggest driver activity and result in suppression of any pending warning or brake intervention:
- Turn signals
- Accelerate
- Brakes
- Steering intervention
Turn signaling:
The steering column tube module control unit reads in the switch position of the combination switch directly and, on vehicles up to 28.02.2013, sends it to the video and radar sensor system control unit and to the multifunction camera via the chassis CAN. On vehicles as of 01.03.2013, the steering column tube module control unit sends the switch position of the combination switch to the video and radar sensor system control unit via chassis CAN 1 and to the multifunction camera via chassis CAN 1, the front SAM control unit and chassis CAN 2.
Acceleration:
The accelerator pedal sensor registers any accelerator pedal actuation. The CDI control unit or the ME-SFI control unit reads in the signals from the accelerator pedal sensor directly and, on vehicles up to 28.02.2013, sends them to the video and radar sensor system control unit and to the multifunction camera via the chassis CAN. On vehicles as of 01.03.2013, the CDI control unit or the ME-SFI control unit sends the signals from the accelerator pedal sensor to the video and radar sensor system control unit via chassis CAN 1 and to the multifunction camera via chassis CAN 1, the front SAM control unit and chassis CAN 2.
Brakes:
Operation of the brake pedal is detected by the brake lights switch. The Electronic Stability Program control unit reads in the status of the brake lights switch directly and uses it to generate the "Brake" request. The Electronic Stability Program control unit also evaluates the data from the yaw rate sensor for lateral and longitudinal acceleration. The yaw rate sensor for lateral and longitudinal acceleration communicates with the Electronic Stability Program control unit via the vehicle dynamics CAN. On vehicles up to 28.02.2013, the Electronic Stability Program control unit sends the information on the status of the service brake and on the vehicle's natural dynamics to the video and radar sensor system control unit and to the instrument cluster via the chassis CAN. On vehicles as of 01.03.2013, the Electronic Stability Program control unit sends the information on the status of the service brake and on the vehicle's natural dynamics to the video and radar sensor system control unit via chassis CAN 1 and to the multifunction camera via chassis CAN 1, the front SAM control unit and chassis CAN 2.
Steering intervention:
Steering movements are detected by the steering angle sensor. The steering column tube module control unit reads in the signals from the steering angle sensor directly and, on vehicles up to 28.02.2013, sends them to the video and radar sensor system control unit and to the multifunction camera via the chassis CAN. On vehicles as of 01.03.2013, the steering column tube module control unit sends the signals from the steering angle sensor to the video and radar sensor system control unit via chassis CAN 1 and to the multifunction camera via chassis CAN 1, the front SAM control unit and chassis CAN 2.
If the video and radar sensor system control unit detects active corner cutting by the driver, crossing over of the lane marking at an angle of ∠ >3° or lateral acceleration of a > 4 m/s2
, a pending warning is suppressed here too. The lateral acceleration is evaluated by the video and radar sensor system control unit inversely proportional to the vehicle speed.
Function sequence for recognition of control interventions
All controls in the driver's immediate vicinity are monitored. If a control intervention is registered, the Lane Keeping Assist deems the driver to be "distracted". As soon as the vehicle drives over the lane marking, an active warning is output. Evaluation of control interventions is carried out by the multifunction camera. The warning threshold is adapted according to the frequency at which the control elements are actuated. In other words, the Lane Keeping Assist warns earlier and possibly also more frequently.
The following controls are monitored:
- Audio system controls
- Radio (with code 523 (Audio 20 CD) or code 510 (Audio 20 CD with 6-disk CD-changer)) or
Radio with Auto Pilot System (with code 525 (MB Audio 50 APS radio) or code 511 (Audio 50 APS incl. DVD changer)) or COMAND controller unit (with code 512 (COMAND APS incl. DVD changer), code 526 (COMAND with single DVD drive (without navigation)), code 527 (COMAND APS with single DVD drive (with navigation)) or code 528 (COMAND incl. DVD changer))
- Radio (with code 523 (Audio 20 CD) or code 510 (Audio 20 CD with 6-disk CD-changer)) or
- Comfort function controls
- Cruise control lever
- Driver-side power window and outside mirror adjustment switch group (only the outside mirror adjustment is monitored)
- Steering column adjustment switch (with code 275 (Memory package), without code 443 (Steering wheel heater)) or steering column adjustment switch and steering wheel heater (with code 275 (Memory package) and code 443 (Steering wheel heater))
- Left multifunction steering wheel button group
- Right multifunction steering wheel button group
- Interior illumination controls
- Front dome lamp switch
- Left front reading lamp switch
- Right front reading lamp switch
Control interventions on audio system:
The radio or the COMAND controller unit sends information on control interventions at the audio systems to the multifunction camera via the interior CAN, front SAM control unit and chassis CAN (up to 28.02.2013) or chassis CAN 2 (as of 01.03.2013).
Control interventions on comfort functions:
The steering column tube module control unit reads in the control interventions at the steering column adjustment switch, at the cruise control lever and at the multifunction steering wheel button group, and sends this information to the multifunction camera via the chassis CAN on vehicles up to 28.02.2013 or via chassis CAN 1, the front SAM control unit and chassis CAN 2 on vehicles as of 01.03.2013.
The steering wheel electronics read in the control interventions at the multifunction steering wheel button groups directly and sends this information to the steering column tube module control unit via the steering LIN.
The left front door control unit reads in the control interventions at the driver-side power window assembly and outside mirror adjustment switch group (outside mirror adjustment only) via the left front door LIN and sends this information to the multifunction camera via the interior CAN, front SAM control unit and chassis CAN (up to 28.02.2013) or chassis CAN 2 (as of 01.03.2013).
Control interventions at interior lighting (with code 414 (Sliding sunroof)): The overhead control panel control unit reads in the status of the front dome lamp switch and of the front reading lamp switch directly and sends this information to the multifunction camera via the interior CAN, front SAM control unit and the chassis CAN (up to 28.02.2013) or chassis CAN 2 (as of 01.03.2013).
Control interventions at interior lighting (without code 414 (Sliding sunroof)):
The status of the front dome lamp switch and the front reading lamp switch is read in directly by the front SAM control unit via the overhead control panel electronics. The front SAM control unit sends this information to the multifunction camera via the chassis CAN (up to 28.02.2013) or chassis CAN 2 (as of 01.03.2013).
Function sequence for issuing warning
The warning is issued haptically by the steering wheel vibration motor, which is integrated into the multifunction steering wheel. The multifunction camera sends the request to actuate the steering wheel vibration motor to the steering column tube module control unit via the chassis CAN (on vehicles up to 28.02.2013) or via chassis CAN 2 (on vehicles as of 01.03.2013), the front SAM control unit and chassis CAN 1. The steering column tube module control unit sends this request via the steering LIN to the steering wheel electronics which actuate the steering wheel vibration motor. The steering wheel vibration motor is actuated for a duration of t = 1.5 s. The intensity of the haptic warning is adapted to the vehicle speed, to cover for perceptible influences from the suspension at high speeds.
The following situations will result in suppression of a warning output, because it is assumed that the driver activity is intentional:
- Status changes of steering wheel, brake or accelerator pedal
- Recognized "corner cutting" (by means of lane recognition and the current vehicle position the multifunction camera recognizes a road with bends and concludes "corner cutting"). Warnings about corner cutting are not issued until a defined lateral acceleration is reached.
- Active flashing function (corresponding turn signaling)
- Active or passive safety functions active
Vehicles up to 31.05.2012:
After warning suppression, a warning can only be output again after approx. t = 3 s or after t = 10 s in the case of turn signaling.
Vehicles as of 01.06.2012:
Following suppression, the next warning can be issued in "Standard" mode only after approx. t = 3 s, in "Adaptive" mode only after approx. t = 5 s and following turn signaling only after t = 10 s.
The corresponding information on suppression of the warning is received by the multifunction camera via the chassis CAN (up to 28.02.2013) or chassis CAN 2 (as of 01.03.2013). If corner cutting is detected, the warning is delayed until a defined threshold (lateral acceleration depending on vehicle speed) is reached. Only then is the warning issued.
Additional function requirements for active intervention by the brake system
- Two lane barriers (lines, one of which may be broken) must be present
- A crossed over lane barrier must be a lane divider line
- Recognition that a lane has been exited (calculated in multifunction camera and video and radar sensor system control unit)
- Driver warning by multifunction camera currently pending
- No driver activity detected
- No stationary object between the vehicle and lane marking on the vehicle side facing away from the intervention detected by the radar sensor system of the DISTRONIC PLUS or Active Blind Spot Assist functions (e.g. warning beacons in construction sites)
- 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
The video and radar sensor system control unit receives the picture data from the multifunction camera over the LVDS line. The picture data are used by the video and radar sensor system control unit to calculate a lane. Parallel to this the multifunction camera also calculates its own lane.
The multifunction camera sends this lane data to the video and radar sensor system control unit via the chassis CAN (on vehicles up to 28.02.2013) or via chassis CAN 2 (on vehicles as of 01.03.2013), the front SAM control unit and chassis CAN 1. The video and radar sensor system control unit compares the calculated lane with the lane data from the multifunction camera. If the comparison matches to a sufficient degree, the video and radar sensor system control unit uses the comparison to generate a "trusted" lane.
If, for example, the vehicle crosses over a continuous line on the right side of the vehicle, the video and radar sensor system control unit decides whether and with which intensity course-correcting brake application is to take place.
If the multifunction camera does not detect any driver activity at the same time and also does not detect any stationary objects on the vehicle side facing away from the intervention, the video and radar sensor system control unit issues approval for the intervention by the brake system. The video and radar sensor system control unit sends the request for wheel-specific (active) braking of the left side of the vehicle over the dynamics CAN to the Electronic Stability Program control unit. The Electronic Stability Program control unit implements this request and actuates the traction system hydraulic unit accordingly. The vehicle is "guided back" into the lane. At the same time as the wheel-specific intervention by the brake system, the driver is visually notified of this activity. For this purpose, the video and radar sensor system control unit sends the request to issue a notification message to the multifunction camera via the chassis CAN (on vehicles up to 28.02.2013) or via chassis CAN 1 (on vehicles as of 01.03.2013), the front SAM control unit and chassis CAN 2. The multifunction camera sends this request via the chassis CAN (up to 28.02.2013) or chassis CAN 2 (as of 01.03.2013) to the instrument cluster, which then outputs this request on the multifunction display.
If the driver countersteers against the intervention by the brake system (overrides the intervention by the brake system), the intervention by the brake system is immediately canceled. Information on active intervention by the brake system function:
If the video and radar sensor system control unit detects active corner cutting, crossing over of the lane marking at an angle of ∠ >3° or lateral acceleration of a > 4 m/s2 , brake application is suppressed.
Active interventions by the brake system are canceled, when one of the following situations occurs:
- Engine switched off
- No forward travel detected
- Lane data cannot be recorded correctly
- Multifunction camera and the video and radar sensor system control unit calculate different lanes
- Driver steers back into the lane
- ESP® passively engaged (except with engine 157)
- ESP® switched to "SPORT HANDLING MODE" (with engine 157)
- ABS, ASR, BAS, ESP®, PRE-SAFE® or Active Blind Spot Assist request brake application
- Driver activity recognized:
- Turn signaling
- Accelerate
- Brakes
- Steering intervention
| Electrical function schematic for Active Lane Keeping Assist | Model 218 up to model year 2014 with code 238 (Active lane keeping Assist) | PE54.71-P-2053-97XAA | |
| Model 218 as of model year 2014 up to model year 2015 with code 238 (Active lane keeping Assist) | PE54.71-P-2053-97XAB | ||
| Overview of system components for driver assistance systems | GF54.00-P-9998FQ |