Lane Keeping Assist, function - GF54.71-P-0005GR
MODEL 166 up to model year 2016 with CODE 476 (Lane keeping assist)
Function requirements, general
- Terminal 15 ON
- Lane Keeping Assist enabled over instrument cluster
- Vehicle speed v ≥60 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 up to 4.6 m
The electronic ignition lock control unit transmits the circuit status of circuit 15 over chassis CAN 2 to the multifunction camera.
The instrument cluster transmits the status of the Lane Keeping Assist to the multifunction camera via the chassis CAN 2.
Lane Keeping Assist, general
The 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. The Lane Keeping Assist takes the driver's behavior into consideration and decides the point at which a warning is to be issued.
On model 166.8 and on model 166.0 as of 01.07.2012, the driver has the option to set the sensitivity of the automatic lane recognition function in the instrument cluster's "Assistance" menu. The instrument cluster sends the status of the automatic lane recognition via chassis CAN 2 to the multifunction camera.
The following operating modes are available for selection:
- Standard (high sensitivity, warnings issued earlier and more frequently)
- Adaptive (reduced sensitivity, 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 Lane Keeping Assist principle, shown on model 166.0
Lane Keeping Assist operation is speed-dependent. The vehicle speed is calculated from the wheel speed signals of the rpm sensors. The Electronic Stability Program control unit directly reads in the signals from the rpm sensors and sends them over the chassis CAN 1, electronic ignition lock control unit and chassis CAN 2 to the instrument cluster. The instrument cluster calculates the vehicle speed to be displayed and sends this over chassis CAN 2 to the multifunction camera.
The Lane Keeping Assist consists of 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, visually records the road space in front of the vehicle. To this end, the multifunction camera uses a fixed scan rate to analyze pictures of the lane and then sends them to the control unit integrated into the multifunction camera. The multifunction camera measures the lane based on the lane markings.
Schematic of lane recognition by multifunction camera
Based on the recorded picture sequences and the measurement values resulting from the lane markings, the multifunction camera calculates 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 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 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.
In construction site areas, the Lane Keeping Assist function may not be able to issue warnings due to multiple markings. The instrument cluster continuously displays the current status, in particular the warning readiness.
Possible displays in the multifunction display of the instrument cluster, model 166.0 up to 30.06.2012
Possible displays in the multifunction display of the instrument cluster, model 166.8, model 166.0 as of 01.07.2012
the multifunction camera sends the corresponding request for issuing a warning or readiness message via the chassis CAN 2 to the instrument cluster. The instrument cluster directly controls the multifunction display over which the corresponding messages are displayed.
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/turn rate, lateral acceleration and longitudinal acceleration
- Steering intervention
Deliberate driver activity is recorded as follows:
Turn signaling:
The steering column tube module control unit directly reads in the switch position of the combination switch and sends this via chassis CAN 1, the electronic ignition lock control unit and chassis CAN 2 to the multifunction camera.
Acceleration:
The accelerator pedal sensor registers any accelerator pedal actuation. The CDI control unit or ME-SFI [ME] control unit directly reads in the signals of the accelerator pedal sensor and sends these via chassis CAN 1, the electronic ignition lock control unit and chassis CAN 2 to the multifunction camera.
Brakes/turn rate, lateral acceleration and longitudinal acceleration:
Operation of the brake pedal is detected by the brake lights switch. The Electronic Stability Program control unit directly reads in the status of the brake lights switch. The Electronic Stability Program control unit also evaluates the data from the yaw rate sensor for lateral and longitudinal acceleration. This is sent by the yaw rate sensor for lateral and longitudinal acceleration via vehicle dynamics CAN to the Electronic Stability Program control unit. The Electronic Stability Program control unit transmits the status of the brake light switch and information about the vehicle's self-movement over chassis CAN 1, electronic ignition lock control unit and chassis CAN 2 to the multifunction camera.
Steering intervention:
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 sends these via chassis CAN 1, the electronic ignition lock control unit and chassis CAN 2 to the multifunction camera.
If the multifunction camera detects active corner cutting, crossing over of the lane marking at an angle of ∠ > 3° or a lateral acceleration of a > 4 m/s2
, 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 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 to the frequency with which the controls are actuated, i.e. the Lane Keeping Assist provides warnings sooner and more frequently if necessary.
The following controls are monitored:
- Audio system controls:
- Radio or COMAND controller unit
- 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 or steering column adjustment and steering wheel heater switch
- Left multifunction steering wheel button group or right multifunction steering wheel button group
- Interior illumination controls:
- Interior lamp automatic function switch
- Left front reading lamp switch
- Right front reading lamp switch
Control interventions are recorded as follows:
Control interventions on audio system:
Control interventions on the audio system buttons are sent to the multifunction camera by the radio or the COMAND controller unit over interior CAN, electronic ignition lock control unit and chassis CAN 2. Control interventions on comfort functions:
The control interventions at the steering column adjuster, 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 transmitted via chassis CAN 1, the electronic ignition lock control unit and chassis CAN 2 to the multifunction camera.
The steering wheel electronics read in the control interventions on the multifunction steering wheel button groups directly and transmit them to the steering column tube module control unit over the steering LIN.
Control interventions at the driver-side power window and outside mirror adjustment switch group are read in by the left front door control unit via the left front door LIN and transmitted via interior CAN, electronic ignition lock control unit and chassis CAN 2 to the multifunction camera.
Interior illumination control interventions:
The status of the interior lights automatic function switch and the front reading light switch are read in directly by the overhead control panel control unit and transmitted via roof LIN to the SAM control unit. The SAM control unit transmits these via interior CAN, the electronic ignition lock control unit and chassis CAN 2 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 transmits the request to actuate the steering wheel vibration motor via chassis CAN 2, the electronic ignition lock control unit and chassis CAN 1 to the steering column tube module control unit. The steering column tube module control unit forwards the request over 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 account 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 recognized (braking, accelerating and braking or turn signaling).
If during a warning a driver response is detected, e.g. steering back into the lane or turn signaling, the warning is also terminated.
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 systems active
Model 166.0 up to 30.06.2012:
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.
Model 166.8 and model 166.0 as of 01.07.2012:
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 warning suppression is received by the multifunction camera over the chassis CAN 2. If corner cutting is detected the warning time is postponed until a defined threshold (lateral acceleration dependent on vehicle speed) has been reached and then a warning is issued.
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