Lane Keeping Assist, function - GF54.71-P-0005FLM

MODEL 212 as of model year 2014 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 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. 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)

Under the following conditions any driving over lane markings is detected, but a warning is not issued:

• For driver activities through evaluation of steering-wheel movement, brake requests and the accelerator pedal position
• For sporty cornering (cutting corners)
• When turn signaling
• For active control intervention functions by the brake assist system
  Fig 2: Overview Of Vehicle Lane Keeping Assist

  Courtesy of MERCEDES-BENZ USA

Illustration of the principle of Lane Keeping Assist 

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 on the basis of the wheel speeds. The Electronic Stability Program control unit or the regenerative braking system control unit sends this to the multifunction camera over chassis CAN 1, front SAM control unit and chassis CAN 2. The Electronic Stability Program control unit or the regenerative braking system control unit also sends the wheel speeds over the 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 

Additional function requirements for lane recognition 

• Recognizable lane markings 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 analyzes 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 zones), the Lane Keeping Assist might not be ready to issue a warning. Tar joints in the road surface might be interpreted as lane markings, which can also lead to a suppression of the readiness to output a warning.

Function sequence for recognition of driver activity 

The following situations suggest driver activity and result in suppression of any pending warning:

• Clearly active steering, braking or accelerating
• Cutting a tight corner
• Turn signals
• Sporty driving at high cornering speeds or with high acceleration

Steering intervention:

Steering movements are detected by the steering angle sensor. The steering column tube module control unit directly reads in the signals of the steering angle sensor directly and sends these over chassis CAN 1, the front SAM control unit and chassis CAN 2 to the multifunction camera.

Brakes:

Operation of the brake pedal is detected by the brake lights switch. The Electronic Stability Program control unit or the regenerative braking system control unit reads in the status of the switch directly and sends it over chassis CAN 1, the front SAM 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, 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.

Rotational speed, lateral and longitudinal acceleration:

The yaw rate sensor for lateral and longitudinal acceleration sends the longitudinal and lateral acceleration vales and the yaw velocity to the Electronic Stability Program control unit or the regenerative braking system control unit over the vehicle dynamics CAN. The Electronic Stability Program control unit or the regenerative braking system control unit evaluates the data and sends the data to the multifunction camera over chassis CAN 1, the front SAM control unit and chassis CAN 2.

If the multifunction camera detects active corner cutting, crossing over the lane markings at an angle of ∠ > 3° or a lateral acceleration of a > 4 m/s² , a pending warning or intervention by the brake system is also suppressed.

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 adjusted to match the control actuating frequency, i.e. the Lane Keeping Assist warns earlier and possibly more often. 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)
  • Steering column adjustment and steering wheel heater switch (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 (523) MB Audio 20 radio or code (510) Audio 20 with CD changer) or the COMAND controller unit (with code (512) COMAND APS incl. DVD changer or code (527) COMAND APS with single DVD drive (with navigation) or code (528) COMAND incl. DVD changer) sends information about control interventions at the audio system to the multifunction camera via interior CAN, front SAM control unit and chassis CAN 2.

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, to account for perceptible influences from 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 interventions or turn signaling).

It is possible to choose between "Standard" or "Adaptive" mode using the corresponding menu in the instrument cluster. The instrument cluster transmits the information on the selected mode to the multifunction camera via chassis CAN 2.

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 high acceleration (e.g. kick-down)
• During strong braking
• During rapid steering movements (e.g. during an evasive maneuver or during a rapid lane change)
• Corner cutting recognized

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.

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.

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-2057-97DAB
	Overview of system components for driver assistance systems		GF54.00-P-9998FLM