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

GF54.71-P-0004CA Active Lane Keeping Assist, Function
MODEL 207
- with CODE (238) Active Lane Keeping Assist

Function requirements, general
^ Circuit 15 ON
^ Function in instrument cluster (A1) enabled
^ Vehicle speed v = 60 to 250 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 = 2.5 to 4.6 m (excepted are track widths of s > 3.9 m, that are driven at a speed of v < 100 km/h)
The electronic ignition lock control unit (N73) sends the circuit 15 status over the chassis CAN (CAN E) to the video and radar sensor system control unit (N62/2) and the multifunction camera (A40/11).





Active Lane Keeping Assist, in general (Shown on model 221)
Active Lane Keeping Assist detects any unintentional driving across lane markings and issues a haptic warning to the driver in certain circumstances 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 (M99). 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.
As from 1.6.12 it will be possible for the driver to select the sensitivity of the active Lane Keeping Assist in the instrument cluster's "Assistance" menu.
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 antilock 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 lane divider line is crossed over (lane barrier) at an angle of < 3° and only when the lane is restricted through two lane markings. By contrast, a warning is always issued when a broken line is crossed over.
Active Lane Keeping Assist operation is speed-dependent. The vehicle speed is calculated on the basis of the wheel speed signals.
The wheel speeds are recorded by the following sensors:
- 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) directly reads in the signals from the rpm sensors direct and sends them over the chassis CAN to the instrument cluster and to the video and radar sensor system control unit.
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 is mounted at the top center of the windshield and visually records the road space in front of the vehicle.
The multifunction camera records lane images. at a fixed scan rate and makes them available to the integrated control unit.
The multifunction camera also sends the picture data over a low voltage differential signal (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 documented 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 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.
In construction site areas, the Active Lane Keeping Assist function may not be able to issue warnings due to multiple markings.
The current status, especially the warning readiness, is indicated continuously in the instrument cluster's multifunction display (A1p13).
The multifunction camera sends the corresponding requests over the chassis CAN to the instrument cluster.





Possible displays:
- Status
- Icon OFF: Active Lane Keeping Assist deactivated
- Icon yellow (1): Active Lane Keeping Assist activated, but not ready to issue warnings (e.g. v < 60 km/h)
- Warning readiness
- Icon green (2): Active Lane Keeping Assist activated and ready to issue warnings
- Message for interventions by brake system 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
Deliberate driver activity is recorded as follows:

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

Acceleration:
The accelerator pedal sensor (B37) registers when the accelerator pedal is operated.
The CDI control unit (N3/9) (for diesel engine) or the ME-SFI [ME] control unit (N3/10) (for gasoline engine) directly reads in the signals from the accelerator pedal sensor and sends them over the chassis CAN to the video and radar sensor system control unit and to the multifunction camera.

Brakes:
The brake lights switch (S9/1) registers when the brake pedal is operated. The Electronic Stability Program control unit directly reads in the status of the brake lights switch. The Electronic Stability Program control unit also reads in the data from the yaw rate sensor for lateral and longitudinal acceleration (B24/15). The yaw rate sensor for lateral and longitudinal acceleration sends the values for the vehicle longitudinal and lateral acceleration, and the yaw velocity over the dynamics CAN (CAN H) to the Electronic Stability Program control unit.
The Electronic Stability Program control unit sends the values for the vehicle longitudinal and lateral acceleration, the yaw velocity and the status of the brake lights switch over the dynamics CAN to the video and radar sensor system control unit and the multifunction camera.

Steering intervention:
The steering movements are recorded by the steering angle sensor (N49).
The steering column tube module control unit reads in the signals from the steering angle sensor and transmits this via the chassis CAN to the video and radar sensor system control unit and the multifunction camera.
If the multifunction camera or the video and radar sensor system control unit detect active corner cutting, crossing of the lane marking at an angle of > 3° or lateral acceleration of g > 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 antiproportional 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 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 (A2) (with code (510) Audio 20 incl. CD-changer or with code (523) MB Audio 20 radio) or Radio with Auto Pilot System (A2/56) (with code (511) Audio 50 APS incl. DVD changer or with code (525) MB Audio 50 APS radio) or COMAND controller unit (A40/3) (with code (512) COMAND APS incl. DVD changer or code (526) COMAND with single DVD drive (without navigation) or code (527) COMAND APS with single DVD drive (with navigation) or code (528) COMAND incl. 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 (driver seat, steering column, mirrors))
- Left multifunction steering wheel button group (S110) or right multifunction steering wheel button group (S111)
- Interior illumination controls:
- Front dome lamp switch (N70/3s4)
- Left front reading lamp switch (N70/3s6)
- Right front reading lamp switch (N70/3s7)

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

Control interventions on comfort functions:
Control interventions on the steering column adjustment switch, on the CRUISE CONTROL lever and at the multifunction steering wheel button groups are read in by the steering column tube module control unit, and they are sent over the chassis CAN, electronic ignition lock control unit and front end CAN to the multifunction camera.
The steering wheel electronics (N135) directly read in the control interventions on the multifunction steering wheel button groups and send them over 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 are read in by the left door control unit (N69/1) over the left door-LIN (LIN B5) and sends them over the interior CAN, front SAM control unit and the chassis CAN to the multifunction camera.

Interior illumination control interventions:
The status of the front dome lamp switch and the front reading lamp switch in the Electronic overhead control panel (N70/3) are directly read in by the front SAM control unit and they are sent over the 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 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 detected (braking, accelerating, steering intervention 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 systems active

Vehicles up to 31.5.12:
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.

Vehicles as of 1.6.12:
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. After this a warning is issued.

Additional function requirements for active intervention by the brake system
^ Two lane delimitations present (lines, one of which may be broken)
^ The lane delimitation 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
^ No driver activity detected
^ Vehicle speed v = 60 to 200 km/h
^ Track width s = 2.6 to 4.4 m (excepted are track widths of s > 3.9 m, that are driven at a speed of v < 100 km/h)
^ No stationary objects detected by radar sensor system on the vehicle side facing away from the intervention (e.g. warning beacons in construction sites)
^ Electronic Stability Program (ESP(R)) not switched to passive mode
^ ESP(R) not in active diagnostic or roller dynamometer mode
^ Antilock braking system (ABS), acceleration skid control (ASR), Brake Assist System (BAS), ESP(R), PRE-SAFE brake inactive
^ Enable for active intervention by the brake system issued by the yaw moment interface
The yaw moment interface is integrated into the Electronic Stability Program control unit and it issues the enable for a course-correcting braking torque.

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 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 (A7/3) 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.
To this end, the video and radar sensor system control unit sends the request to issue an obligatory information over the chassis CAN to the multifunction camera.
The multifunction camera then sends this request over the chassis CAN to the instrument cluster, which then issues the obligatory information in the multifunction display.
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 cutting, crossing over of the lane marking at an angle of >3° or any 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 situations occurs:
- Engine switched off
- No forward travel detected
- Lane data cannot be recorded correctly
- Multifunction camera and the video and radar sensor system control unit calculate different lanes
- Driver steers back into the lane
- ESP switched to passive mode
- ABS, ASR, BAS, ESP(R), PRE-SAFE brake or Active Blind Spot Assist requests intervention by the brake system
- Driver activity recognized:
- Turn signaling
- Acceleration
- Brakes
- Steering intervention