Lane Keeping Assist function - GF54.71-P-0005FL
MODEL 212.0/2 28.2.13 with CODE (476) Park Assist
Function requirements, general
- Circuit 15 ON
- Function enabled via the instrument cluster (A1)
- Vehicle speed:
Warning at v = 60 to 270 km/h
- Recognizable lane markings present on both sides (no construction site markings (yellow/white), no snow, not covered up, i.e. contrast too low)
- Radius of curve r >150 m
- Track width s = 2.5 up to 4.6 m
The electronic ignition lock control unit (N73) sends the circuit 15 status over the chassis CAN (CAN E) to the multifunction camera (A40/11).
Lane Keeping Assist, general
The Lane Keeping Assist function detects any unintentional driving across lane markings and issues a haptic warning to the driver in certain circumstances through 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 (M99). The Lane Keeping Assist function takes the driver's behavior into consideration and decides the point at which a warning is to be issued.
For vehicles as of 1.6.12 an option is available to the driver to configure the sensitivity of the Lane Keeping Assist in the instrument cluster's "Assistance" menu.
The following operating modes are available for selection:
- Standard
(Sensitivity increased, warnings issued earlier and more frequently)
- Adaptive
(Sensitivity reduced, warnings issued later and less often)
Under the following conditions any driving over lane markings is detected, but a warning is not issued:
- Driver activity through evaluation of steering wheel movements, brake requests and accelerator pedal position
- Sporty cornering (corner cutting)
- Turn signals
- Active control interventions by braking assistance systems
Illustration of the Lane Keeping Assist principle, shown on model 212.0
The Lane Keeping Assist function operates on a speed-dependent basis and therefore requires calculation of the vehicle speed, which is defined by the wheel speeds.
The wheel speeds are recorded by the following components:
- Left front axle rpm sensor (L6/1)
- Right front axle rpm sensor (L6/2)
- Left rear axle rpm sensor (L6/3)
- Right rear axle rpm sensor (L6/4)
The rpm sensors are read in directly by the following control units on a model-specific basis and then sent by them over the chassis CAN to the instrument cluster:
- Electronic Stability Program control unit (N30/4) (except model 212.074/077/095/098/274/277/298)
- Regenerative braking system control unit (N30/6) (model 212.095/098/298)
- Premium Electronic Stability Program control unit (N30/7) (model 212.074/077/274/277)
The instrument cluster calculates the listed vehicle speed and sends this over the chassis CAN to the multifunction camera.
The Lane Keeping Assist function encompasses 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 lane recognition
The multifunction camera, which is mounted at the top center on the front window, registers the road space in front of the vehicle. To this end, the multifunction camera uses a fixed scan rate to document pictures of the lane and then sends them to the control unit integrated into the multifunction camera.
The multifunction camera then measures the lane based on the lane markings.
Schematic of lane recognition by multifunction camera
The recorded video sequences and the measurement values that result from the lane marking pictures are used by the multifunction camera to calculate each lane. This calculation is based on a corresponding algorithm.
The multifunction camera uses this data to calculate the relative position of the vehicle in the lane. The actions of the Lane Keeping Assist function are all derived from this.
No lane information can be issued where there are no lane markings or if they are covered up (e.g. by dirt or snow) or where there is a low contrast between the road surface and lane marking 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.
When in a construction site area the Lane Keeping Assist function is unable to issue warnings because of possible multiple lane markings.
The instrument cluster's multifunction display (A1p13) continuously displays the current status of the Lane Keeping Assist function, in particular with regard to warning readiness. This status information is sent by the multifunction camera over the chassis CAN to the instrument cluster.
Possible displays:
- Function status
- Icon off: Lane Keeping Assist deactivated
- Icon yellow (1): Lane Keeping Assist activated, but not ready to issue warnings. (e.g. v < 60 km/h)
- Warning readiness
- Icon green (2): Lane Keeping Assist activated and ready to issue warnings.
- Message for brake interventions and system errors in multifunction display
Function sequence for recognition of driver activity
The following situations suggest driver activity and result in suppression of any pending warning:
- Turn signals
- Accelerate
- Brakes
- Steering intervention
Deliberate driver activity is recorded as follows:
Turn signaling:
The steering column tube module control unit (N80) directly reads in the position of the combination switch (S4) and sends it over the chassis CAN to the multifunction camera.
Acceleration:
The accelerator pedal sensor (B37) registers any operation of the accelerator pedal.
The CDI control unit (N3/9) (for diesel engine) or the ME-SFI [ME] control unit (N3/10) (for gasoline engine) directly reads in the accelerator pedal sensor signals and sends them over the chassis CAN to the multifunction camera.
Brakes:
Operation of the brake pedal is detected by the brake lights switch (S9/1). The Electronic Stability Program control unit or the brake system control unit directly reads in the status of the brake lights switch.
In addition to this, the data of the yaw rate sensor for lateral and longitudinal acceleration (B24/15) are recorded, which sends its data over the vehicle dynamics CAN to the Electronic Stability Program control unit or the brake system control unit.
The Electronic Stability Program control unit or the brake system control unit sends the data on the vehicle's self-movement and the status of the brake lights switch over the chassis CAN to the multifunction camera.
Steering intervention:
Steering movements are recorded by the steering angle sensor (N49). The steering column tube module control unit directly reads in the steering angle sensor signals and sends them over the chassis CAN to the multifunction camera.
If the multifunction camera detects active corner cutting by the driver, crossing over the lane marking at an angle of ∠ > 3° or a lateral acceleration of a > 4 m/s 2, then a pending warning is also suppressed.
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 function deems the driver to be "distracted". As soon as the vehicle drives over the lane marking, an active warning is output.
Control interventions are evaluated by the multifunction camera. The warning threshold is adjusted to match the control actuating frequency, i.e. the Lane Keeping Assist system warns earlier and possibly more often.
The following controls are monitored:
- Audio system controls
- Radio (A2) (with code (510) Audio 20 with CD changer or code (523) MB Audio 20 radio) or
- Radio with auto pilot system (A2/56)
(with code (511) Audio 50 APS with DVD changer or code (525) MB Audio 50 APS radio) or
- COMAND controller unit (A40/3)
(with code (512) COMAND APS incl. DVD changer or code (526) COMAND with single DVD drive (without navigation) or code (527) COMAND APS with single DVD drive (with navigation) or code (528) COMAND incl. DVD changer)
- Comfort function controls
- Cruise control lever (S40/4)
- Driver-side power window and outside mirror adjustment switch group (S20)
(only the outside mirror adjustment is monitored)
- Steering column adjustment switch (S59) (with code (275) Memory package for electrically adjustable front seats and without code (443) steering wheel heater) or steering column adjustment switch (S59/1) (with code (275) Memory Package for electrically adjustable front seats and code (443) steering wheel heater)
- Left multifunction steering wheel button group (S110) and right multifunction steering wheel button group (S111)
- Interior illumination controls
- Front dome lamp switch (N70s4) (with code 414) Power glass tilting/sliding roof)
- Left front reading lamp switch (N70s6) (with code (414) Power glass tilting/sliding roof)
- Right front reading lamp switch (N70s7) (with code (414) Power glass tilting/sliding roof)
- Front dome lamp switch (N70/3s4) (without code 414) Power glass tilting/sliding roof)
- Left front reading lamp switch (N70/3s6) (without code (414) Power glass tilting/sliding roof)
- Right front reading lamp switch (N70/3s7) (without code (414) Power glass tilting/sliding roof)
Control interventions are recorded as follows:
Control interventions on audio system:
The control interventions on the audio system control buttons are sent by the radio or the radio with autopilot system or the COMAND controller unit over the interior CAN (CAN B), front SAM control unit with fuse and relay module (N10/1) and the chassis CAN to the multifunction camera.
Control interventions on comfort functions:
Control interventions at the steering column adjuster switch, at the cruise control lever and at the multifunction steering wheel button groups are read in by the steering column tube module control unit, and they are sent over the chassis CAN to the multifunction camera.
The steering wheel electronics (N135) directly read in the control interventions at the multifunction steering wheel button groups, and send them over the steering LIN (LIN E1) to the steering column tube module control unit.
Control interventions at the driver-side power window and outside mirror adjustment switch group (outside mirror adjustment only) are read in by the left front door control unit (N69/1) over the left front door (LIN B5) and they are sent over the interior CAN, front SAM control unit and the chassis CAN to the multifunction camera.
Control interventions on the interior illumination (with code (414) Power glass tilting/sliding roof):
The statuses of the dome lamp switch and the front reading lamp switch are directly read in by the overhead control panel control unit (N70) and then sent over the interior CAN, front SAM control unit and the chassis CAN to the multifunction camera.
Control interventions on the interior illumination (without code (414) Power glass tilting/sliding roof):
The statuses of the dome lamp switch and the front reading lamp switch are directly read in by the front SAM control unit over the electronic OCP (N70/3). The front SAM control unit then sends them over the chassis CAN to the multifunction camera.
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 then sends the request to activate the steering wheel vibration motor over the chassis CAN, steering column tube module control unit and the steering LIN to the steering wheel electronics, which then 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 warning is terminated when the triggering conditions are no longer given or when driver activity is detected (braking, accelerating or turn signaling).
The warning is also terminated if, during a warning, a driver response is detected (e.g. steering back into the lane or turn signaling).
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 30.5.12:
The next possible warning output, after a warning output has been suppressed, takes place after approx. t = 3 s and generally after turn signaling for t = 10 s.
Vehicles as of 1.6.12:
After a warning is suppressed, the next possible warning can be issued in "Standard" mode after approx. t = 3 s, in the "Adaptive" mode after approx. t = 5 s and following turn signaling always after t = 10 s.
The corresponding information for suppression of the warning is received by the multifunction camera over the chassis CAN. If corner cutting is detected, the warning is delayed until a defined threshold (lateral acceleration depending on ground speed) is reached. Only then is the warning issued.
| Lane Keeping Assist, location of components | GF54.71-P-0005-01FL | ||
| Electrical function schematic for Lane Keeping Assist | PE54.71-P-2057-97DAA | ||
| Lane Keeping Assist block diagram | GF54.71-P-0005-02FL | ||
| Overview of system components for Lane Keeping Assist | GF54.71-P-9995FL |