Active Lane Keeping Assist, function - GF54.71-P-0004GR

MODEL 166 up to model year 2016 with CODE 238 (Active lane keeping Assist) 

Function requirements, general 

• Terminal 15 ON
• Active Lane Keeping Assist is enabled using instrument cluster.
• Vehicle speed:
  • Warning at v ≥60 km/h
  • Brake intervention at v = 60 to 200 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):
• s = 2.5 to 4.6 m for warning
• s = 2.6 to 4.4 m and v = 60 to 200 km/h for brake intervention (excepted are lane widths of s > 3.9 m that are driven at a speed of v < 100 km/h)

Interventions by the brake system only ever take place when:

• An easily visible, uninterrupted line is crossed over
• No trailer was detected on the vehicle (with CODE 550 (Trailer hitch))
• The Electronic Stability Program (ESP®) is not switched to passive (except model 166.074/874) or the ESP® is not switched to "SPORT HANDLING MODE" (on model 166.074/874).
• Run-flat tire is not active

The electronic ignition lock control unit sends the status of circuit 15 via chassis CAN 1 to the video and radar sensor system control unit and via chassis CAN 2 to the multifunction camera.

The instrument cluster sends the status of Active Lane Keeping Assist to the video and radar sensor system control unit via chassis CAN 2, electronic ignition lock control unit and chassis CAN 1 and to the multifunction camera via chassis CAN 2.

The "Trailer detected" status is transmitted by the trailer recognition control unit to the video and radar sensor system control unit over the interior CAN, electronic ignition lock control unit and chassis CAN 1. The Electronic Stability Program control unit sends the status of ESP® to the video and radar sensor system control unit via chassis CAN 1.

Active Lane Keeping Assist, general (shown on model 221) 

The Active 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. Active Lane Keeping Assist takes the driver's behavior into consideration and decides the point at which a warning is to be issued. If the driver fails to react to the warning, specific interventions by the brake system are authorized from the video and radar sensor system control unit to return the vehicle to the road lane.

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 Active Lane Keeping Assist system in the "Assistance" menu in the instrument cluster.

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)

If the driver indicates that he/she is "active" before or during the intervention by the brake system, the intervention by the brake system is suppressed or canceled. If the video and radar sensor system control unit detects activity of the anti-lock braking system (ABS), acceleration skid control (ASR), Brake Assist System (BAS), PRE-SAFE® system or the Active Blind Spot Assist system which requires an intervention by the brake system, a brake intervention by Active Lane Keeping Assist is also suppressed or immediately canceled.

Interventions by the brake system only occur when a solid line is crossed over (lane barrier) at an angle of ≤ < 3° and only when the lane is restricted by two lane markings. A warning is also issued when a broken line is crossed over.

Active 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 rpm sensor signals and sends these over the chassis CAN 1 to the video and radar sensor system control unit and over 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 video and radar sensor system control unit calculates the vehicle speed itself.

The Active Lane Keeping Assist function includes 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 active intervention by the brake system 

Function sequence for lane recognition 

The multifunction camera is mounted at the top center of the windshield and visually 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. In addition, the multifunction camera transmits the picture data over an LVDS line to the video and radar sensor system control unit. The multifunction camera measures the lane based on the lane markings.

Schematic of lane recognition by multifunction camera 

Based on the recorded image sequences and the measurement values resulting from the lane markings, the multifunction camera and the video and radar sensor system control unit each calculate a lane independently of each other. These calculations are based on corresponding algorithms. The data are then used by the multifunction camera and the video and radar sensor system control unit to determine the relative position of the vehicle in the lane. The actions of the Active 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 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 Active Lane Keeping Assist function may not be able to issue warnings due to multiple markings.

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 or pending brake intervention:

• 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 reads in the switch position of the combination switch directly and transmits this over chassis CAN 1 to the video and radar sensor system control unit and over chassis CAN 1, 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 reads in the signals of the accelerator pedal sensor directly and transmits these over chassis CAN 1 to the video and radar sensor system control unit and over chassis CAN 1, 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 sends the status of the brake lights switch and the information on the vehicle's self-movement over the chassis CAN 1 to the video and radar sensor system control unit and 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 reads in the signals of the steering wheel angle sensor directly and transmits these over chassis CAN 1 to the video and radar sensor system control unit and over chassis CAN 1, electronic ignition lock control unit and chassis CAN 2 to the multifunction camera.

If the multifunction camera or the video and radar sensor system control unit detects active corner cutting, crossing of the lane marking at an angle of ≤ > 3° or lateral acceleration of g > 4 m/s ² , any pending warning or intervention by the brake system is also suppressed. The lateral acceleration is evaluated by the video and radar sensor system control unit negatively proportional to the vehicle speed.

Function sequence for recognition of control interventions 

All controls in the driver's immediate vicinity are monitored. If a control intervention is registered, the Active 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 Active Lane Keeping Assist system warns earlier and possibly more often.

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 a 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.

Additional function requirements for active intervention by the brake system 

• Two lane markings present (lines, one of which may be broken)
• The lane marking crossed is a continuous line.
• Exiting of lane detected (recorded by multifunction camera and video and radar sensor system control unit)
• Active warning by multifunction camera

For this purpose, the video and radar sensor system control unit transmits the request to output a notification message over chassis CAN 1, electronic ignition lock control unit and chassis CAN 2 to the multifunction camera. The multifunction camera sends this request over chassis CAN 2 to the instrument cluster, which outputs it on the multifunction display.

• No driver activity detected
• No stationary objects detected by radar sensor system on the vehicle side opposite the intervention (e.g. warning beacons in construction sites)
• Approval issued for active intervention by the brake system for yawing moment interface

The yawing moment interface that is integrated in the Electronic Stability Program control unit sends out a status signal to enable a track-aligning braking torque.

Function sequence for active intervention by the brake system 

The video and radar sensor system control unit receives the picture data from the multifunction camera over the LVDS line. The picture data are used by the video and radar sensor system control unit to calculate a lane. Parallel to this the multifunction camera also calculates its own lane.

The lane data are sent by the multifunction camera over chassis CAN 2, electronic ignition lock control unit and chassis CAN 1 to the video and radar sensor system control unit.

The video and radar sensor system control unit compares the calculated lane with the lane data from the multifunction camera. If the comparison matches to a sufficient degree, the video and radar sensor system control unit uses the comparison to generate a "trusted" lane. If the vehicle, for example, crosses over a continuous line on the right side of the vehicle, the video and radar sensor system control unit decides whether and with which intensity a course-correcting intervention by the brake system is to take place. If the multifunction camera does not detect any driver activity at the same time and also does not detect any stationary objects on the vehicle side facing away from the intervention, the video and radar sensor system control unit issues approval for the intervention by the brake system.

The video and radar sensor system control unit sends the request for wheel-specific (active) braking of the left side of the vehicle over the dynamics CAN to the Electronic Stability Program control unit. The Electronic Stability Program control unit implements this request and actuates the traction system hydraulic unit accordingly.

The vehicle is "guided back" into the lane.

At the same time as the wheel-specific intervention by the brake system, the driver is visually notified of this activity.

If the driver countersteers against the intervention by the brake system (overrides the intervention by the brake system), the intervention by the brake system is immediately canceled.

Information on active intervention by the brake system function:

If the video and radar sensor system control unit detects active corner >3° or cutting, crossing over of the lane marking at an angle of ∠ or lateral acceleration of a > 4 m/s 2, an intervention by the brake system is suppressed.

Active interventions by the brake system are canceled, when one of the following conditions occurs:

• Engine switched off
• No forward travel

  The direction of travel is defined using the wheel rotation direction. The Electronic Stability Program control unit directly reads in the signals of the rpm sensors and sends them via chassis CAN 1 to the video and radar sensor system control unit.

• Vehicle lane data cannot be recorded.
• Multifunction camera and the video and radar sensor system control unit calculate different lanes.
• Driver activity recognized:
  • Turn signals
  • Accelerate
  • Brakes
  • Steering intervention
• ESP switched to passive mode
• ABS, ASR, BAS, ESP®, PRE-SAFE® or Active Blind Spot Assist requests an intervention by the brake system.

Electrical function schematic for Active Lane Keeping Assist	PE54.71-P-2053-97NAA
Overview of system components for driver assistance systems	GF54.00-P-9998GR