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

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

MODEL 216.3
- with CODE (238) Active Lane Keeping Assist
- as of Model Year 2011 /YoM 10 model refinement package
MODEL 221.0 /1(except 221.095 /195)
- with CODE (238) Active Lane Keeping Assist
- as of model year 2011 /YoM 10

Function requirements, general
- Circuit 15 ON
- Function enabled via the instrument cluster (A1)
- Radius of curve r >150 m
- Track width:
- s = 2.2 to 4.6 m for warning
- s = 2.6 up to 3.9 m and v < 100 km/h for intervention by the brake system
- s = 2.6 up to 4.4 m and v > 100 km/h for intervention by the brake system

- Recognizable lane markings present (not covered, no construction site markings (yellow/white), no snow, etc., i.e. contrast too low)
- Vehicle speed:
- Warning at v = 60 to 270 km/h
- Intervention by the brake system at v = 60 up to 200 km/h

The Active Lane Keeping Assist function is activated in the "Assistance" menu in the instrument cluster.

The instrument cluster sends the vehicle speed over the chassis CAN (CAN E). The status of circuit 15 is transmitted by the EZS control unit (N73) via the chassis CAN.

Intervention by the brake system only takes places if:
- No trailer detected on vehicle
- Electronic Stability Program (ESP) not passively connected
- No run-flat mode is active







Active Lane Keeping Assist, general
The Active Lane Keeping Assist system detects when lane markings are crossed over and warns the driver in certain situations by means of a warning system in the steering wheel when the lane is exited. If the driver does not react to the warning, intervention by the brake system is authorized in order to move the vehicle back into the lane.
If the driver indicates to the system that he/she is "active" before the intervention by the brake system, the intervention by the brake system is suppressed or 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.







Schematic display of multifunction camera (A40/11) lane recognition
The Active Lane Keeping Assist function consists of the following subfunctions:
- Function sequence for lane recognition
- Function sequence for recognition of control interventions
- Function sequence for recognition of driver activity
- Function sequence for issuing warning
- Function sequence for suppression of warning output
- Function sequence for active intervention by the brake system
- Function sequence for suppression of active intervention by the brake system
- Function sequence for cancellation of active intervention by the brake system

Function sequence for lane recognition
The multifunction camera, which is attached to the windshield below the inside rearview mirror unit (A67), monitors the road in front of the vehicle. To this end the multifunction camera records pictures at a fixed scan rate and sends them to the control unit integrated into the multifunction camera and over the low voltage differential signal (LVDS) to the video and radar sensor system control unit (N62/2) for further processing.

In doing so, measurements are made of the lane markings. From the recorded picture sequences and the measurements on the road lane markings, a lane is then calculated in the multifunction camera and the video and radar sensor system control unit independent of each other and using different algorithms.
The algorithm stored in the multifunction camera is used solely for checking the plausibility of the warning function.
The combination of both algorithms is used for checking the plausibility of the braking function.
The data is 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 system measures are then all derived from this position.

No lane information can be output if there are no lane markings or if they are covered (e.g. by dirt or snow), if there is insufficient contrast between the road surface and the lane markings or if 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 area the system is unable to issue warnings because of multiple markings.

The instrument cluster continuously displays the current status, in particular the warning readiness.
Possible displays:
- System status
- On (icon visible)
- Off (icon hidden)

- Warning readiness
- Icon yellow: Active Lane Keeping Assist activated but not yet in warning readiness. (e.g. v < 60 km/h)
- Icon green: Active Lane Keeping Assist activated with warning and braking readiness.

- Message for brake intervention shown in multifunction display (A1p13)

Function sequence for recognition of control interventions
All controls in the driver's immediate vicinity are monitored. If a control intervention is detected, the Active Lane Keeping Assist system regards the driver to be "distracted" and an active warning is issued as soon as the vehicle crosses over the lane marking. The control interventions are recorded by the multifunction camera. The warning threshold is adapted 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:
- Rotary light switch (S1)
- Left front seat operation switch group (S22) or switch group for power windows, outside mirrors and trunk lid on driver side (S20/1)
- COMAND control unit
- Combination switch (S4) (except left and right turn signal switch (S4s1))
- Roof system switch (N70s1) (on model 221 with code (413) Panoramic glass sunroof with top sliding sunroof or code (414) Power glass tilting/sliding roof or on model 216) in overhead control panel control unit (N70)
- via the steering column adjustment switch (S59) (without code (443) steering wheel heater)
- steering column adjustment/steering wheel heater switch (S59/1) (with code (443) Steering wheel heater)
- Left multifunction steering wheel button group (S110) and right multifunction steering wheel button group (S111)

The signals from the combination switch (except from the left and right turn signal switch) and from the steering column adjustment switch are read in by the steering column tube module (N80) and transmitted to the multifunction camera via the chassis CAN.
The signals from the multifunction steering wheel button groups are read in by the steering wheel electronics (N135) and forwarded via the steering LIN (LIN E1) to the steering column tube module. The steering column tube module sends the information to the multifunction camera via the chassis CAN.

The signals from the switch group for power windows, outside mirrors and trunk lid on the driver side and the left front seat operation switch group are read in via the front door LIN (LIN B1) by the left door control unit (N69/1) (on model 216) or by the left front door control unit (N69/1) (on model 221) and sent to the central gateway control unit (N93) via the interior CAN (CAN B).
The central gateway control unit sends the signals via the chassis CAN to the multifunction camera.
The signal from the rotary light switch is read in via the instrument panel LIN (LIN 1) by the upper control panel control unit (N72/1) and sent via the interior CAN to the central gateway control unit. The central gateway control unit sends the signal via the chassis CAN to the multifunction camera.
The signal from the roof system switch is sent by the overhead control panel control unit via the interior CAN to the central gateway control unit and from there it is forwarded via the chassis CAN to the multifunction camera.
The signal from the COMAND controller unit is sent via the interior CAN to the central gateway control unit and from there via the chassis CAN to the multifunction camera.

Function sequence for recognition of driver activity
Signals that indicate detected driver activity (e.g. accelerating, braking, steering, turn signals) cause immediate cancellation of the pending warning or intervention by the brake system. Any pending warning or intervention by the brake system is also canceled if the multifunction camera and the video and radar sensor system control unit detect active corner cutting by the driver, crossing of the lane marking at an angle of > 3° or lateral acceleration of g > 4 m/s2. Operation of the accelerator pedal is sent by the CDI control unit (N3/9) (for diesel engine) or the ME-SFI [ME] control unit (N3/10) (for gasoline engine) over the chassis CAN to the multifunction camera.
The ESP control unit (N47-5) additionally sends wheel speed signals, the yaw rate and the status of the service brake via the chassis CAN to the multifunction camera and to the video and radar sensor system control unit. The signal from the steering angle sensor (N49) is sent by the steering column tube module via the chassis CAN to the multifunction camera and to the video and radar sensor system control unit.

The current data from the steering angle sensor are evaluated by the multifunction camera and the video and radar sensor system control unit for driver activity. The sequence for warning comes into force accordingly.
The signals from the left and right turn signal switch are read in by the steering column tube module and sent via the chassis CAN to the multifunction camera and to the video and radar sensor system control unit.
If the multifunction camera and the video and radar sensor system control unit detect activities of the following systems, a pending warning or intervention by the brake system is canceled immediately:
- Antilock brake system (ABS)
- Acceleration Slip Regulation (ASR)
- Brake Assist (BAS)
- PRESAFE
- Active Blind Spot Assist (with code (237) Active Blind Spot Assist)

Additional function requirements for warning output
- Recognized leaving of lane
- No currently applied suppression of warning output

Function sequence for issuing warning
The warning output function consists of the following subfunctions:
- Function sequence for haptic warning
- Function sequence for warning cancellation

Function sequence for haptic warning
The multifunction camera sends the request via the chassis CAN to the steering column tube module. This passes on the request via the steering LIN to the steering wheel electronics which actuates the steering wheel vibration motor (M99). Three pulses (warning duration t = 1.5 s) are issued and perceived by the driver as a vibration. The intensity of the warning is adapted to the vehicle speed to make sure that it can be perceived despite feedback from the suspension at high speeds.

Function sequence for warning cancellation
The warning is canceled if the triggering conditions no longer exist or if driver activity is detected (braking, accelerating and braking or turn signaling). If, during a warning, a driver response is detected, e.g. by steering back or by flashing, then only two pulses are issued (warning duration t = 1.0 s).

Any cancellation of a warning always results in an intervention by the brake system also being canceled.

Function sequence for suppression of warning output
If the multifunction camera receives at least one of the following pieces of information, a warning is suppressed, as 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"). Corner-cutting warnings are not output until a defined lateral acceleration is reached
- Active flashing function (corresponding turn signaling)
- Active or passive safety systems active

The individual pieces of information for suppression of the warning are received by the multifunction camera over the chassis CAN.

If "corner cutting" is detected, the output of a warning is delayed until a defined threshold (lateral acceleration in relation to vehicle speed) is reached; a warning is then issued.

Additional function requirements for active intervention by the brake system
- Two lane barriers (lines, one of which may be broken) must be present
- A crossed over lane barrier must be a lane divider line
- Recognition that a lane has been exited (calculated in multifunction camera and video and radar sensor system control unit)
- Driver warning by multifunction camera currently pending
- No driver activity detected

Function sequence for active intervention by the brake system
The video and radar sensor system control unit compares its calculated lane with the multifunction camera lane. If the comparison of the lanes matches to a sufficient degree, the video and radar sensor system control unit uses the comparison to generate a secured lane.
The driver activities detected by the multifunction camera and its emitted warning status to the driver are also drawn on by the video and radar sensor system control unit. This data and the secured lane are used by the video and radar sensor system control unit together with a defined algorithm to decide whether and to what extent a lane-correcting intervention by the brake system should take place.

If lane-correcting intervention by the brake system is required, this request is sent by the video and radar sensor system control unit via the chassis CAN to the multifunction camera and the ESP control unit. The ESP control unit then initiates appropriate selective brake intervention.

If during an intervention by the brake system the driver steers opposite to the intervention by the brake system (i.e. overrides the intervention by the brake system), the intervention by the brake system is immediately canceled.

Function sequence for suppression of active intervention by the brake system
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 > 3° or any lateral acceleration of g > 4 m/s2 an intervention by the brake system is suppressed.

Function sequence for cancellation of active intervention by the brake system
Intervention by the brake system is canceled if one of the following conditions occurs:
- Engine switched off
- No forward travel detected
- Lane data cannot be acquired correctly
- Multifunction camera and the video and radar sensor system control unit calculate different lane data
- Driver activity (e.g. accelerating, driver braking, steering, flashing) detected
- ESP passively connected
- ABS, ASR, BAS, ESP, PreSafe or Active Blind Spot Assist request an intervention by the brake system