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

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 

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

IMPORTANT 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.

IMPORTANT Intervention by the brake system only takes places if:

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.

IMPORTANT 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.

Fig 1: View Of Active Lane Keeping Assist System
G07629268Courtesy of MERCEDES-BENZ USA

Schematic display of multifunction camera (A40/11) lane recognition 

Fig 2: Identifying Schematic Display Of Multifunction Camera (Lane Recognition)
G07629250Courtesy of MERCEDES-BENZ USA

The Active Lane Keeping Assist function consists of the following subfunctions:

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.

IMPORTANT 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:

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:

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/s 2. 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:

Additional function requirements for warning output 

Function sequence for issuing warning 

The warning output function consists of the following subfunctions:

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).

IMPORTANT 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:

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

IMPORTANT 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 

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.

IMPORTANT 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:

  Automatic lane recognition, location of components   GF54.71-P-0002-01LE 
REFER TO SYSTEM WIRING DIAGRAMS Electrical function schematic for Active Lane Keeping Assist On model 216 PE54.71-P-2053-97CAA
  Automatic lane recognition, block diagram   GF54.71-P-0002-02LE 
  Component description for instrument cluster A1 GF54.30-P-6000LE 
  Component description for COMAND controller unit A40/3
With code (526) COMAND with single DVD drive (without navigation)
With code (527) COMAND APS with single DVD drive (with navigation system)		 GF82.85-P-3136LE
With code (530) COMAND APS USA (with navigation system) GF82.85-P-3136LEU
  Component description for multifunction camera A40/11 GF54.21-P-3300LE
Component description for ME-SFI [ME] control unit With engine 273 GF07.61-P-6000MLS
  Component description for ESP control unit N47-5 GF42.45-P-5118LE
  Video and radar sensor system control unit, component description N62/2 GF30.30-P-3304LE
  Component description for left door control unit N69/1
On model 216		 GF72.29-P-4124LA
  Component description for overhead control panel control unit N70 GF82.20-P-5216LE
  Upper control panel control unit, component description N72/1 GF54.21-P-6040LE
  EZS control unit, component description N73 GF80.57-P-6003LE
  Component description for steering column tube module N80 GF54.21-P-6050LE
  Component description for central gateway control unit N93 GF54.21-P-4170LE
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