Lane Keeping Assist, Function - GF54.71-P-0005KJ
MODEL 453.0/3/4 with CODE 238 (Lane keeping assist)
Function requirements, general
- Circuit 15 ON
- Function is not deactivated using the Lane Keeping Assist button
- Vehicle speed: v ≥ 70 km/h (approx. 43 mph) up to the maximum design speed
- Recognizable lane markings present (i.e. sufficient contrast because no construction site markings (yellow/white), no snow, not covered up, etc.)
- Track width of road surface s = 2.3 to 4.5 m (Europe), s = 2.8 to 5.5 m (approx. 9.19 to 18.04 ft) (USA, Australia), s = 2.8 to 5.5 m (Russia), s = 2.8 to 4.8 m (Japan, China, Arab States of the Gulf, Taiwan)
The circuit 15 ON status and therefore the power supply are received by the multifunction camera over the vehicle interior fuse and relay module. The ignition lock switches a relay in the vehicle interior fuse and relay module which then connects circuit 15g to the multifunction camera.
Lane Keeping Assist, general
The Lane Keeping Assist detects when road lame markings are unintentionally crossed over and warns the driver in certain situations, visually with a warning symbol and acoustically through the instrument cluster's warning buzzer. Crossing over lane markings is optically recorded and processed by the multifunction camera. The Lane Keeping Assist takes the driver's behavior into consideration and decides the point at which a warning is to be issued. Under the following conditions any driving over lane markings is detected, but a warning is not issued:
- Turn signals
- Crossing over lane markings at high speed
- Cutting tight corners
Lane Keeping Assist operation is speed-dependent. The vehicle speed is calculated from the wheel speed signals. The wheel speeds are recorded by the following sensors:
- Left front axle rpm sensor
- Right front axle rpm sensor
- Left rear axle rpm sensor
- Right rear axle rpm sensor
The Electronic Stability Program control unit reads in the rpm sensor signals directly, uses them to calculate the vehicle speed and sends this over the interior CAN to the multifunction camera.
The Lane Keeping Assist function encompasses the following subfunctions:
- Self-test function sequence
- Function sequence for lane recognition
- Lane Keeping Assist displays in the instrument cluster multifunction display
- Function sequence for recognition of driver activity
- Function sequence for issuing warning
Self-test function sequence
After switching on the ignition (Circuit 15 ON) or activating its after pressing the Lane Keeping Assist button, the Lane Keeping Assist then runs a self-test. During this self-test, the system components are checked for proper operation and the multifunction camera or the windshield for soiling. The status-LED in the Lane Keeping Assist button is actuated fort the self-test. If the test is passed, the system switches the LED off again whereupon the Lane Keeping Assist system is then operational. If the system detects a fault, the status-LED in the Lane Keeping Assist button remains actuated and the Lane Keeping Assist symbol in the instrument cluster multifunction display flashes on and off. On vehicles with code K36 (Instrument cluster with color 8.9 cm (3.5") display) the "Lane Keeping Assist nonfunctional" fault message is also issued. A warning tone is also issued through the warning buzzer in the instrument cluster.
Detailed information on display messages issued by the Lane Keeping Assist is available in the "Lane Keeping Assist displays in instrument cluster multifunction display". Detailed information on possible reasons for a fault message is available in the operator's manual.
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. For this purpose, the multifunction camera records pictures of the lane at a fixed scanning rate and makes these pictures available to the integrated control unit. The multifunction camera measures the lane based on the lane markings.
Schematic of lane recognition by multifunction camera
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 may be unable to issue warnings due to multiple markings. The instrument cluster multifunction display continuously shows the current status of the Lane Keeping Assist, in particular its warning readiness. This status information is sent by the multifunction camera over the interior CAN to the instrument cluster.
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. On the basis of this data, the multifunction camera determines 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.
Lane Keeping Assist displays in the instrument cluster multifunction display
Depending on the instrument cluster involved, the displays may differ:
- Possible displays in multifunction display (A1p13) of instrument cluster (A1) for vehicles with code K35 (Instrument cluster with monochrome display)
- Possible displays in multifunction display (A1p13) of instrument cluster (A1) for vehicles with code K36 (Instrument cluster with color 8.9 cm (3.5") display)
Possible displays in multifunction display (A1p13) of instrument cluster (A1) on vehicles with code K35 (Instrument cluster with monochrome display) (shown on instrument cluster for vehicles with engine 281)
Function status:
- Symbol off: Lane Keeping Assist deactivated
- Symbol (3): Lane Keeping Assist activated, but not ready for warning (e.g. v < 70 km/h (approx. 43 mph))
- Symbol (3) flashes for 3 s at a frequency of 1 Hz: System error, Lane Keeping Assist activated but warning readiness not active. A warning tone is also issued through the warning buzzer in the instrument cluster.
The status of the deactivated Lane Keeping Assist is also indicated by the red status LED in the Lane Keeping Assist button lighting up.
Warning readiness:
- Readiness symbol (4): Lane Keeping Assist activated and ready for warning (v < 70 km/h (approx. 43 mph))
- Warning symbol (5) flashes for 5 s at a frequency of 1 Hz: Lane Keeping Assist warning because lane markings crossed over, 4 warning tones are also issued through the warning buzzer on the instrument cluster.
Possible displays in multifunction display (A1p13) of instrument cluster (A1) for vehicles with code K36 (Instrument cluster with color 8.9 cm (3.5") display)
Function status:
- Symbol off: Lane Keeping Assist deactivated
- Neutral symbol (1): Lane Keeping Assist activated, but without warning readiness (e.g. v < 70 km/h (approx. 43 mph))
- Neutral symbol (1), flashes for 3 s at a frequency of 1 Hz for system errors: Lane Keeping Assist is activated, but warning readiness not active. The multifunction display also shows the message "Lane Keeping Assist nonfunctional" and a warning tone is issued on the instrument cluster.
Warning readiness:
- Green symbol (2): Lane Keeping Assist activated and ready for warning (v < 70 km/h (approx. 43 mph))
- Green symbol (2) flashes for 5 s at a frequency of 1 Hz: Lane Keeping Assist warning because lane markings crossed over, 4 warning tones are also issued through the warning buzzer on the instrument cluster.
All in all, on vehicles with code K36 (Instrument cluster with color 8.9 cm (3.5") display) and depending on the system status, 3 different pop-up displays are shown on the instrument cluster multifunction display:
- "Lane Keeping Assist nonfunctional" for system errors
- "Lane Keeping Assist ON" when switching on
- "Lane Keeping Assist OFF" when switching off
The status of the deactivated Lane Keeping Assist is also indicated by the red status LED in the Lane Keeping Assist button lighting up. Detailed information on Lane Keeping Assist display messages and possible reasons for a fault message are available in the operator's manual.
Function sequence for recognition of driver activity
The following situations suggest driver activity and result in suppression of any pending warning:
- Turn signals
- Crossing over lane markings at high speed
- Cutting tight corners
Turn signaling:
The center SAM control unit reads in the switch position of the combination switch directly, and sends the status of the set turn signal over the interior CAN to the multifunction camera.
Crossing over lane markings at high speed or cutting tight corners:
If the multifunction camera detects active corner cutting by the driver or crossing over of the lane marking at an angle of > 3° or a high lateral acceleration of approx._a_>_4_m/s2 , a pending warning is suppressed here too.
Function sequence for issuing warning
The warning is issued visually through the green symbol (2) on vehicles with Code K36 (Instrument cluster with color 8.9 cm (3.5") display) or on vehicles with code K35 (Instrument cluster with monochrome display) on the warning symbol (5) in the instrument cluster multifunction display. Here, each symbol flashes for 5 s at a frequency of 1 Hz. The acoustic warning is issued using the warning buzzer in the instrument cluster. When the lane marking is crossed over here, 4 warning tones are issued through the warning buzzer in the instrument cluster. The multifunction camera sends a request to issue the warning over the interior CAN to the instrument cluster.
| Electrical function schematic for Lane Keeping Assist | PE54.71-P-2057-97BBA | ||
| Overview of system components for driver assistance systems | GF54.00-P-9998KJ |