GF54.71-P-0004FL Active Lane Keeping Assist, Function

GF54.71-P-0004FL Active Lane Keeping Assist, Function

MODEL 212.0 /2
- with CODE (238) Active Lane Keeping Assist
- as of model year 2011 /YoM 10

Function requirements, general
- Circuit 15 ON
- Function in instrument cluster (A1) enabled
- Vehicle speed:
- Warning at v = 60 to 250 km/h
- Intervention by the brake system at v = 60 up to 200 km/h

- Recognizable lane markings present on both sides (no construction site markings (yellow/white), no snow, not covered up, i.e. 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 km/h to 200 km/h for intervention by the brake system (excepted here are track widths s > 3.9 m, which may be driven on at a speed of v < 100 km/h)

The status of circuit 15 is sent by the electronic ignition lock control unit (N73) over the chassis CAN (CAN E) to the multifunction camera (A40/11) and the video and radar sensor system control unit (N62/2).

Interventions by the brake system only ever take place when:
- an easily visible, uninterrupted line is crossed over
- run-flat tire is not active
- Except model 212.074/077/274/277:
Electronic Stability Program (ESP(R)) not switched to passive mode

- With model 212.074/077/274/277:
- ESP(R) not switched to "ESP Sport" mode (up to 31.5.10)
- ESP(R) not switched to "SPORT HANDLING MODE" (as of 1.6.10)







Active Lane Keeping Assist, in general (Shown on model 221)
The Active Lane Keeping Assist function detects when lane markings are unintentionally crossed over and warns the driver haptically through steering wheel vibrations in certain situations. Crossing over lane markings is recorded and processed by optically the multifunction camera.
The haptic warning is generated by the steering wheel vibration motor (M99).
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.

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 the Active Lane Keeping Assist function is also suppressed or immediately canceled.

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

The Active Lane Keeping Assist function operates on a speed- dependent basis and therefore requires the vehicle speed to be calculated as per the wheel speeds.
The wheel speeds are recorded by the following components:
- Left front axle rpm sensor (L6/1)
- Right front axle rpm sensor (L6/2)
- Left rear axle rpm sensor (L6/3)
- Right rear axle rpm sensor (L6/4)

The Premium Electronic Stability Program control unit (N30/7) reads in the rpm sensor signals directly and sends them over the chassis CAN to the video and radar sensor system control unit and the instrument cluster. The instrument cluster calculates the vehicle speed to be displayed and sends this over the chassis CAN 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, which is mounted at the top center on the front window, visually records the road space in front of the vehicle.
To this end, the multifunction camera uses a fixed scan rate to document pictures of the lane and then sends them to the control unit integrated into the multifunction camera. The multifunction camera measures the lane based on the lane markings.
The image data are also sent over a low voltage differential signaling (LVDS) line to the video and radar sensor system control unit.







Schematic of lane recognition by multifunction camera
The documented picture sequences and measurement values, which are generated from the lane marking pictures, lanes are calculated in the multifunction camera and in the video and radar sensor system control unit independent of each other and using corresponding algorithms.

The algorithm stored in the multifunction camera is used to enable the warning function.
The algorithm in the video and radar sensor system control unit issues a brake function enable following positive verification with the multifunction camera algorithm.

Based on these data, the multifunction camera and video and radar sensor system control unit determine the relative position of the vehicle on the lane. The actions of the Active Lane Keeping Assist function are all derived from this.

No lane information can be issued where there are no lane markings or if they are covered up (e.g. by dirt or snow) or where there is a low contrast between the road surface and 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.
When in construction site areas, the function is unable to issue warnings because of possible multiple lane markings.

The instrument cluster continuously displays the current status, in particular the warning readiness.







Possible displays on vehicles up to 31.5.11:
- Function status
- Symbol off: Active Lane Keeping Assist deactivated
- Symbol activated (1): Active Lane Keeping Assist activated, but not ready to issue warnings
(e.g. v < 60 km/h)

- Warning readiness
- Symbol inverted (2): Active Lane Keeping Assist activated and ready to issue warnings

- Message for brake interventions and function errors in multifunction display (A1p13)







Possible displays on vehicles as of 1.6.11:
- Function status
- Symbol off: Active Lane Keeping Assist deactivated
- Symbol yellow (3): Active Lane Keeping Assist activated, but not ready to issue warnings
(e.g. v < 60 km/h)

- Warning readiness
- Symbol green (4): Active Lane Keeping Assist activated and ready to issue warnings

- Message for brake interventions and 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 or brake intervention:
- Turn signals
- Accelerate
- Brakes
- Steering intervention

Turn signaling:
The steering column tube module control unit (N80) directly reads in the switch position of the combination switch (S4) and transmits it to the multifunction camera and video and radar sensor system control unit via the chassis CAN.

Acceleration:
Acceleration is recorded by the accelerator pedal sensor (B37).
The CDI control unit (N3/9) (with diesel engine) or the ME-SFI [ME] control unit (N3/10) (with gasoline engine) reads in the signals of the accelerator pedal sensor directly and forwards them on to the multifunction camera and video and radar sensor system control unit via the chassis CAN.

Brakes:
The brake light switch (S9/1) is supplied using circuit 15 by the front SAM control unit. When the service brake is being operated, the voltage that is present is switched through to the Premium Electronic Stability Program control unit (N30/7).
In addition, the Electronic Stability Program control unit evaluates the data from the yaw rate sensor for lateral and longitudinal acceleration (B24/15). These are sent by the yaw rate sensor for lateral and longitudinal acceleration to the Electronic Stability Program control unit via the vehicle dynamics CAN (CAN H).

The Electronic Stability Program control unit sends the status of the service brake system via the chassis CAN to the multifunction camera and video and radar sensor system control unit.

Steering intervention:
Steering movements are recorded by the steering angle sensor (N49). The steering column tube module control unit directly reads in the data of the steering angle sensor and transmits them to the multifunction camera and video and radar sensor system control unit via the chassis CAN.

If the video and radar sensor system control unit detects active corner cutting by the driver, crossing of the lane marking at an angle of angle > 3° or lateral acceleration of a > 4 m/s2, 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 inversely 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. The control interventions are evaluated by the multifunction camera. The multifunction camera adapts the warning threshold to match the control actuating frequency, i.e. the Automatic Lane Recognition system warns earlier and possibly more often.

The following controls are monitored:
- Audio system controls:
- Radio (A2) (with code (523) MB Audio 20 radio or code (510) Audio 20 incl. CD changer) or
- Radio with auto pilot system (A2/56) (with code (525) MB Audio 50 APS radio or code (511) Audio 50 APS incl. DVD changer) or
- COMAND controller unit (A40/3) (with code (527) COMAND APS with single DVD drive (with navigation) or code (528) COMAND incl. DVD changer or code (512) COMAND APS with DVD changer)

- Comfort function controls:
- Cruise control lever (S40/4)
- Driver-side power window and outside mirror adjustment switch group (S20) (only the outside mirror adjustment is monitored)
- Steering column adjustment switch (S59) (with code (275) Memory package for electrically adjustable front seats and without code (443) Steering wheel heater) or steering column adjustment and steering wheel heater switch (S59/1) (with code (275) Memory package for electrically adjustable front seats and code (443) Steering wheel heater)
- Left multifunction steering wheel button group (S110) or right multifunction steering wheel button group (S111)

- Interior illumination controls
- Front dome lamp switch (N70s4) (with code 414) Power glass tilting/sliding roof)
- Left front reading lamp switch (N70s6) (with code (414) Power glass tilting/sliding roof)
- Right front reading lamp switch (N70s7) (with code (414) Power glass tilting/sliding roof)
- Front dome lamp switch (N70/3s4) (without code 414) Power glass tilting/sliding roof)
- Left front reading lamp switch (N70/3s6) (without code (414) Power glass tilting/sliding roof)
- Right front reading lamp switch (N70/3s7) (without code (414) Power glass tilting/sliding roof)

Control interventions are recorded as follows:
Control interventions on audio system:
Control interventions on the control buttons of the audio system are transmitted by the radio or COMAND controller unit via interior CAN (CAN B), the front SAM control unit with fuse and relay module (N10/1) and chassis CAN to the multifunction camera.

Control interventions on comfort functions:
Control interventions at the steering column adjustment controls, cruise control lever and multifunction steering wheel button groups are read in by the steering column tube module control unit and transmitted via chassis CAN to the multifunction camera.

Control interventions at the multifunction steering wheel button groups are read in directly by the steering wheel electronics (N135) and transmitted via the steering LIN (LIN E1) to the steering column tube module control unit.

Control interventions at the driver-side power window and outside mirror adjustment switch group (outside mirror adjustment only) are read in by the left front door control unit (N69/1) via the front door LIN (LIN B5) and transmitted via interior CAN, front SAM control unit and chassis CAN to the multifunction camera.

Control interventions on the interior illumination (with code (414) Power glass tilting/sliding roof):

The overhead control panel control unit (N70) reads in control interventions on the interior illumination directly and sends them to the multifunction camera via the interior CAN, front SAM control unit and chassis CAN.

Control interventions on the interior illumination (without code (414) Power glass tilting/sliding roof):
Control interventions at the interior illumination are read in directly by the front SAM control unit and transmitted via chassis CAN to the multifunction camera.

The overhead control panel electronics (N70/3) are connected directly to the front SAM control unit.

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 the request to actuate the steering wheel vibration motor via chassis CAN to the steering column tube module control unit and steering LIN to the steering wheel electronics. The steering wheel electronics then actuate the steering wheel vibration motor.
The steering wheel vibration motor is actuated for a duration of t = 1.5 s. This is felt by the driver as a vibration.
The intensity of the warning is adapted to the vehicle speed, to account for perceptible influences from the suspension at high speeds.

The warning is terminated if the triggering condition is no longer met 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

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.

The corresponding information for suppression of the warning is received by the multifunction camera over the chassis CAN.
If "corner cutting" is recognized a warning period delay occurs, until a defined threshold (lateral acceleration dependent on ground speed) is reached, whereupon a warning is then issued.

Additional function requirements for active intervention by the brake system
- Lane markings present (one of which may be a broken line)
- A lane marking which is crossed over must be an unbroken line
- Exiting of lane detected (calculated in multifunction camera and in video and radar sensor system control unit)
- Warning of driver currently issued
- No driver activity detected
- No stationary object detected on the side away from the intervention between the vehicle and the lane marking through the radar sensor system of the DISTRONIC PLUS or Active Blind Spot Assist functions (e.g. warning beacons in construction sites)
- Approval issued for active intervention by the brake system for yawing moment interface

The yawing-moment interface is integrated into the Electronic Stability Program control unit and sends out a status signal to enable a course-correcting brake system intervention.

Function sequence for active intervention by the brake system
The video and radar sensor system control unit receives the pictures 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 multifunction camera sends the lane data over the chassis CAN to the video and radar sensor system control unit.
The video and radar sensor system control unit compares both lanes with each other. 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 dividing line on the right side of the vehicle, the video and radar sensor system control unit uses a defined algorithm to decide whether and with which intensity a track-aligning intervention by the brake system is to take place.
If the multifunction camera does not detect any driver activities and, simultaneously, the radar sensor system does not detect any stationary objects on the vehicle side away from the intervention, the video and radar sensor system control unit enables a course- correcting brake system intervention.
The video and radar sensor system control unit sends a request over the vehicle dynamics CAN for wheel-specific (active) braking of the left side of the vehicle to the Electronic Stability Program control unit.
The Electronic Stability Program control unit then initiates wheel- specific interventions by the brake system, which are implemented by the traction system hydraulic unit.

The vehicle is "guided back" into the lane.
At the same time as the wheel-specific interventions by the brake system, the driver is visually notified of this activity.
To this end, the video and radar sensor system control unit sends a corresponding request to issue information over the chassis CAN to the multifunction camera.
The multifunction camera transmits this request to the instrument cluster via the chassis CAN. The notification is then output on the multifunction display.

If, during an intervention by the brake system, 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 cutting by the driver, any crossing over of the lane marking at an angle of angle >3° or any lateral acceleration of a > 4 m/s2 an intervention by the brake system is suppressed.

Active interventions by the brake system are canceled, when one of the following conditions occurs:
- Driver steers back into the lane (as of 1.6.11)
- Engine switched off
- No forward travel detected
- Lane data not recorded properly
- Multifunction camera and the video and radar sensor system control unit calculate different lane data
- Except mode 212.074/077/274/277:
ESP(R) switched to passive mode

- With model 212.074/077/274/277:
- ESP(R) switched to "ESP Sport" mode (up to 31.5.10)
- ESP(R) switched to "SPORT HANDLING MODE" (as of 1.6.10)

- ABS, ASR, BAS, ESP, PRE-SAFE or Active Blind Spot Assist request an intervention by the brake system
- Driver activity recognized:
- Turn signaling
- Acceleration
- Brakes
- Steering intervention