Lane Keeping Assist, Function - GF54.71-P-0005RD

Model 172.4 up to model year 2017 

with code 476 (Lane Keeping Assist)/YoM 12 

Shown on model 172.4 

Courtesy of MERCEDES-BENZ USA

Function requirements, general 

• Circuit 15 ON

Lane Keeping Assist, general 

• Function enabled in instrument cluster
• Vehicle speed v = 60 to 250 km/h
• Detectable lane marking present on both sides (no construction site markings (yellow/white), no snow, not covered etc., i.e. not enough contrast)
• Radius of curve r gt 150 m
• Track width s = 2.5 up to 4.6 m

The electronic ignition lock control unit sends the status of circuit 15 to the multifunction camera via the chassis CAN.

The Lane Keeping Assist function 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 function takes the driver's behavior into consideration and decides the point at which a warning is to be issued. The driver also has the option of adjusting the sensibility of the Lane Keeping Assist function in the "Assist." menu of the instrument cluster. The following modes are available for selection:

• Standard, high sensitivity (warnings are issued earlier and more frequently)
• Adaptive, reduced sensitivity (warnings are 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 principle of Lane Keeping Assist 

Courtesy of MERCEDES-BENZ USA

The Lane Keeping Assist function operates on a speed-dependent basis. The vehicle speed is calculated from the wheel speed signals o the RPM sensors.

The Electronic Stability Program control unit reads in the signals from the RPM sensors directly and sends them to the instrument cluster via the chassis CAN. 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, 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 on the basis of the lane markings.

Schematic of lane recognition by multifunction camera 

Courtesy of MERCEDES-BENZ USA

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 actions of the Lane Keeping Assist function are all derived from this. 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 zones, the Lane Keeping Assist function may be unable to issue warnings due to multiple markings.

The current status of the Lane Keeping Assist function, especially the warning readiness, is indicated continuously in the multifunction display of the instrument cluster. This status information is sent by the multifunction camera over the chassis CAN to the instrument cluster.

Courtesy of MERCEDES-BENZ USA

Possible displays:

• Function status
• Symbol off: Lane Keeping Assist deactivated
• Symbol yellow (1): Lane Keeping Assist activated, but not ready to issue warnings

  (e.g. v lt 60 km/h)

• Warning readiness
• Icon green (2): Lane Keeping Assist activated and ready to issue warnings
• Message for function 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 reads in the position of the combination switch directly and sends it to the multifunction camera via the chassis CAN.

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 sends them via the chassis CAN to the multifunction camera.

Brakes:

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. In addition, the Electronic Stability Program control unit evaluates the data for the inherent motion of the vehicle (yawing moment) and sends this data as well as the status of the brake light switch to the multifunction camera via the chassis CAN.

The yaw behavior of the vehicle is detected by the yaw rate sensor for lateral and longitudinal acceleration. On vehicles with code 233 (DISTRONIC PLUS) up to model year 2016 or code 239 (DISTRONIC PLUS) model year 2016 or for model 172.475, this is designed as a separate component and it communicates over the vehicle dynamics CAN with the Electronic Stability Program control unit. On vehicles for which the above-mentioned limitation does not apply, the yaw rate sensor for lateral and longitudinal acceleration is integrated in the Electronic Stability Program control unit.

Steering intervention:

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 them via the chassis CAN to the multifunction camera.

• COMMAND controller unit (with code 527 (COMMAND APS with single DVD drive) or code 512 (COMMAND APS incl. DVD changer))
• Comfort function controls:

If the multifunction camera detects active corner cutting, crossing over of the lane marking at an angle of 4 ∠ 3° or a lateral acceleration of a gt 4 m/s² , a pending warning is suppressed here too.

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.

Evaluation of control interventions is carried out 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 (with code 523 (Audio 20 CD) or code 510 (Audio 20 CD with 6-disk CD-changer))
  • 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))
  • 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 at the audio system buttons are sent by the radio or the COMMAND controller unit via the interior CAN, front SAM control unit and chassis CAN to the multifunction camera.

Control interventions on comfort functions:

The steering column tube module control unit reads in the control interventions at the steering column adjuster, at the cruise control lever and at the multifunction steering wheel button groups and sends them via the chassis CAN 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.

The left door control unit reads in the control interventions at the driver-side power window and outside mirror adjustment switch group via the left door LIN and sends them via the interior CAN, front SAM control unit and chassis CAN to the multifunction camera.

Interior illumination control interventions:

The overhead control panel control unit reads in the status of the interior lamp automatic function switch and the front reading lamp switch directly and sends the status via the wiper/inside rear-view mirror LIN, front SAM control unit and 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 sends the request to actuate the steering wheel vibration motor over the chassis CAN 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 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 and braking 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

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 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.

	Electrical function schematic for Lane Keeping Assist		PE54.71-P-2057-97TAA
	Overview of system components for driver assistance systems		GF54.00-P-9998RD