Lane Keeping Assist, function - GF54.71-P-0005FQM
MODEL 218 as of model year 2015 with CODE 476 (Lane keeping assist)
Function requirements, general
- Engine running or drive train operational
- Lane Keeping Assist function switched on
The CDI control unit or the ME-SFI [ME] control unit sends the "Engine running" or "Drive train operational" signal over the chassis CAN 1, front SAM control unit and chassis CAN 2 to the multifunction camera.
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.
An option is available here 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)
The instrument cluster sends the selected operating mode to the multifunction camera via chassis CAN 2.
Illustration showing principle of Lane Keeping Assist; illustration shows model 218.3
Warnings are issued as soon as the vehicle is in the direct vicinity of a broken or solid line or crosses over it.
Lane Keeping Assist operation is speed-dependent. The vehicle speed is calculated from the wheel speed. The Electronic Stability Program control unit sends this to the multifunction camera via chassis CAN 1, front SAM control unit and chassis CAN 2. In addition, the Electronic Stability Program control unit sends the wheel speed to the instrument cluster via chassis CAN 1, the front SAM control unit and chassis CAN 2.
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
Additional function requirements for lane recognition
- Detectable lane marking present on both sides (no construction site markings (ambiguous markings), no snow, not covered etc., i.e. not enough contrast)
- Two lane dividers present
Function sequence for lane recognition
The multifunction camera is mounted at the top center of the windshield and it records the road space in front of the vehicle. The multifunction camera records pictures of the lane at a fixed scanning rate and makes these pictures available to the integrated control unit.
Schematic of lane recognition by multifunction camera
The multifunction camera calculates the lane based on two different lane algorithms that are implemented in the multifunction camera. If the comparison between the two lane algorithms results in a match, the multifunction camera uses the data to generate a safe lane. 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 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. If there are several markings present (e.g. in construction site zones), the Lane Keeping Assist may not be ready to issue a warning. If tar joints in the road surface are interpreted as lane markings, a warning is suppressed.
Function sequence for recognition of driver activity
The following situations suggest driver activity and result in suppression of any pending warning:
- Clearly active steering (steering intervention), braking or accelerating
- Turn signals
- Sporty driving (high cornering speeds or heavy acceleration)
- Cutting a tight corner
Steering:
Steering movements are recorded by the steering wheel angle sensor.
The steering column tube module control unit reads in the signals from the steering wheel angle sensor directly and sends information about the steering angle to the multifunction camera via chassis CAN 1, the front SAM control unit and chassis CAN 2.
Brakes:
The Electronic Stability Program control unit sends the status of the brake pedal to the multifunction camera via chassis CAN 1, the front SAM control unit and chassis CAN 2.
Acceleration:
The CDI control unit or the ME-SFI control unit sends information about the accelerator pedal position via chassis CAN 1, the front SAM control unit and chassis CAN 2 to the multifunction camera.
Turn signaling:
The steering column tube module control unit directly reads in the switch position of the combination switch and sends this to the multifunction camera via chassis CAN 1, front SAM control unit and chassis CAN 2.
Turn rate, lateral acceleration and longitudinal acceleration (sporty driving):
The acceleration/yaw rate is detected by the yaw rate sensor for lateral and longitudinal acceleration. The yaw rate sensor for lateral and longitudinal acceleration transmits appropriate values via the dynamics CAN to the Electronic Stability Program control unit. The Electronic Stability Program control unit evaluates the data and sends the data to the multifunction camera via chassis CAN 1, front SAM control unit and chassis CAN 2.
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 suppressed here too.
Function sequence for recognition of control interventions
Controls located in close proximity of the driver and that affect the attention of the driver when they are operated are monitored. If a control intervention is registered, the Lane Keeping Assist deems the driver to be "distracted". Control interventions are evaluated 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. An active warning is output as soon as the vehicle is in the direct proximity of or crosses over the lane marking.
The following controls are monitored:
- Audio system controls
- Comfort function controls:
- Cruise control lever
- Steering column adjustment switch (without code (443) Steering wheel heater) or steering column adjustment switch and steering wheel heater (with code (443) Steering wheel heater)
- Left multifunction steering wheel button group or right multifunction steering wheel button group
- Driver-side power window and outside mirror adjustment switch group (only the outside mirror adjustment is monitored)
- Interior illumination controls:
- Interior lamp automatic function switch
- Left front reading lamp switch
- Right front reading lamp switch
Control interventions on audio system:
The radio (with code (505) 20 NTG5 radio without navigation capability or code (522) Audio 20 radio) or the COMAND controller unit (with code (531) COMAND APS) sends information about control interventions at the audio system via the interior CAN, front SAM control unit and chassis CAN 2 to the multifunction camera.
Control interventions on comfort functions:
The steering column tube module control unit sends information about control interventions at the CC lever, steering column adjustment switch (without code (443) Steering wheel heater) or steering column adjustment switch and steering wheel heater (with code (443) Steering wheel heater) and at the multifunction steering wheel button groups to the multifunction camera via chassis CAN 1, front SAM control unit and chassis CAN 2.
The steering wheel electronics reads in the control signals on the multifunction steering wheel button groups directly and transmit them to the steering column tube module control unit over the steering LIN.
Control signals at the driver-side power window and outside mirror adjustment switch group are read in by the left front door control unit over the left front door LIN and sent over the interior CAN, front SAM control unit and chassis CAN 2 to the multifunction camera.
Interior illumination control interventions:
Control interventions on the interior illumination (with code (414) Power glass tilting/sliding roof):
The status of the front dome lamp switch and the front reading lamp switch are directly read in by the overhead control panel control unit and it sends them over the interior CAN, front SAM control unit and the chassis CAN 2 to the multifunction camera.
Control interventions on the interior illumination (without code (414) Power glass tilting/sliding roof):
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 the status over the chassis CAN 2 to the multifunction camera.
Additional function requirements for warning output
- Lane recognition by the multifunction camera
- Vehicle speed v = 60 to 200 km/h
- Radius of curve = r > 150 m
- Leaving of lane recognized
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 over chassis CAN 2, the front SAM control unit and chassis CAN 1 to the steering column tube module control unit. The steering column tube module control unit sends this request over the steering LIN to the steering wheel electronics, which then actuates 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 in order to allow for the perceivable effects of the suspension at high speeds.
The warning is suppressed when the triggering conditions are no longer given or when driver activity is detected (braking, accelerating, steering or turn signaling).
In "Standard" mode, a haptic warning is suppressed under the following prerequisites:
- Turn signaling recognized (the warnings are suppressed for a certain period of time)
- Intervention of a driving safety system recognized (e.g. by Electronic Stability Program (ESP®))
In "Adaptive" mode, a haptic warning is suppressed under the following prerequisites:
- Turn signaling recognized (the warnings are suppressed for a certain time period)
- Intervention of a driving safety system recognized (e.g. by ESP®)
- During heavy acceleration (e.g. kickdown)
- During strong braking
- During rapid steering movements (e.g. during an evasive maneuver or during a rapid lane change)
- Corner cutting recognized
Following suppression (driver activity, triggering condition not given), a new 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.
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.
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. Afterwards, a warning is output.
| Electrical function schematic for Lane Keeping Assist | PE54.71-P-2057-97XAC |
| Overview of system components for driver assistance systems | GF54.00-P-9998FQM |