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

Model 205 

as of model year 2019 

with code 22P (Lane tracking package) 

except code 23P (Driving Assistance package) 

Model 253 (except 253.99) 

as of model year 2020 

with code 22P (Lane tracking package) 

except code 23P (Driving Assistance package) 

Courtesy of MERCEDES-BENZ USA

Function requirements, general 

• Drive train operational:

  The CDI control unit or the ME-SFI [ME] control unit sends the "Drive-train operational" signal over the drive-train CAN, powertrain control unit and periphery CAN to the mono multifunction camera.

• Soiling and function test of mono multifunction camera completed: The mono multifunction camera performs a soiling and function test to ensure proper operation after each engine start. This requires an object to be positioned in the detection range as a reference value. If a malfunction is established or if there are no objects in the detection area, Active Lane Keeping Assist cannot be activated.

Active Lane Keeping Assist, general 

Active Lane Keeping Assist detects when the vehicle crosses lane markings, and issues a haptic warning to the driver through vibrations of the steering gear.

Crossing over of lane markings is optically recorded and processed by the mono multifunction camera.

If the vehicle unintentionally crosses a solid lane marking and the driver does not respond to the warning, the Active Lane Keeping Assist will correct the vehicle's course through targeted brake interventions on one side.

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.

In the case of an active control of the Electronic Stability Program (ESP®), the anti-lock braking system (ABS), the anti-slip control (ASR), the Distance Pilot DISTRONIC or the Active Brake Assist, a brake application of the Active Lane Keeping Assist is suppressed and/or immediately canceled.

Warnings are issued as soon as the vehicle is in the direct vicinity of a broken or solid line or crosses over it.

Brake intervention only occurs when the vehicle drives over an unbroken line (lane boundary) at an angle of ∠ < 3°.

Active Lane Keeping Assist operation is speed-dependent. The mono multifunction camera calculates the vehicle speed based on the wheel speeds. The Electronic Stability Program control unit sends this via the suspension FlexRay, electronic ignition lock control unit and peripherals CAN to the mono multifunction camera.

Courtesy of MERCEDES-BENZ USA

Illustration showing principle of Active Lane Keeping Assist, shown on model 205.0 

The Active Lane Keeping Assist comprises the following subfunctions:

• Function sequence for switching Active Lane Keeping Assist on and off 
• Function sequence for lane recognition 
• Function sequence for recognition of driver activity 
• Function sequence for detection of driver distraction 
• Function sequence for issuing warning 
• Function sequence for brake intervention 

Function sequence for switching Active Lane Keeping Assist on and off 

Active Lane Keeping Assist can be switched on and off by pressing the Active Lane Keeping Assist button in the driver side instrument panel button group. The front SAM control unit reads in the status of the Active Lane Keeping Assist button over the instrument panel LIN and sends this over the interior CAN, electronic ignition lock control unit and the peripherals CAN to the mono multifunction camera. The "Active Lane Keeping Assist ON/OFF" message is shown in the instrument cluster. For this purpose, the mono multifunction camera sends the request to the instrument cluster over the periphery CAN, the electronic ignition lock control unit and the user interface CAN.

• Navigation can be performed via the head unit finger navigation pad and the "Back" button on the steering wheel. The head unit finger navigation pad and the "Back" button transmit the relevant control signals via the steering wheel electronics, the steering wheel CAN, the steering column tube module control unit, the suspension FlexRay, the electronic ignition lock control unit and the user interface CAN to the head unit.
• The operating menu can be called up on the upper control panel control unit via the vehicle button. The status of the Vehicle button is sent by the upper control panel control unit over the LCP LIN, the Audio/COMAND control panel (except code 446 (Touchpad only)) or the touchpad (with code 446 (Touchpad only) or code 448

The driver also has the option of configuring the sensitivity of the Active Lane Keeping Assist in the head unit's "Assistance" menu. The following options are available for navigating in the control menu:

• Except with code 446 (Touchpad only), navigation can be performed using the Audio/COMAND control panel. The corresponding control signals are sent by the Audio/COMAND control panel (except code 446 (Touchpad only)) over the telematics CAN to the head unit.
• With code 446 (Touchpad only) or code 448 (Touchpad), navigation can be performed using the touchpad. The corresponding control signals are sent by the touchpad (with code 446 (Touchpad only) or code 448 (Touchpad)) over the telematics CAN to the head unit.
• The navigation can occur with code 531 (COMAND APS) per voice control. The driver hands-free system microphone is read directly by the head unit.

(Touchpad)) and the telematics CAN to the head unit.

The head unit sends the selected operating mode over the user interface CAN, electronic ignition lock control unit and the periphery CAN to the mono multifunction camera.

The following operating modes can be selected:

• Standard, sensitivity high (warnings issued earlier and more frequently)
• Adaptive, sensitivity low (warnings issued later and less often)

Additional function requirements for lane recognition 

• Recognizable lane markings present at both sides (no construction site markings (ambiguous markings), no snow, not covered, etc.)
• Forward travel detected

The direction of travel is defined using the wheel rotation direction. The Electronic Stability Program control unit sends corresponding information over the chassis FlexRay, powertrain control unit and the periphery CAN to the mono multifunction camera.

Function sequence for lane recognition 

The mono multifunction camera is mounted at the top center of the windshield and records the road space in front of the vehicle. The mono multifunction camera records pictures of the lane at a fixed scanning rate and makes these pictures available to the integrated control unit.

Schematic of lane recognition by mono multifunction camera 

Courtesy of MERCEDES-BENZ USA

The mono multifunction camera calculates the lane based on two different lane algorithms that are implemented in the mono multifunction camera. If the comparison between the two lane algorithms results in a match, the mono multifunction camera uses the data to generate a safe lane.

On the basis of this data, the mono multifunction camera determines 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. If there are several markings present (e.g. in construction site zones), the Active Lane Keeping Assist may not be ready to issue a warning. If tar seams in the road surface are interpreted as lane markings, a warning is suppressed or an unauthorized warning is output.

Function sequence for recognition of driver activity 

The following situations suggest driver activity and result in suppression of any pending warning:

• Clearly active steering (steering intervention), braking or accelerating
• Cutting a tight corner
• Turn signals
• Sporty driving at high cornering speeds or with high acceleration

Steering: 

Steering movements are recorded by the steering wheel angle sensor. The steering column tube module control unit reads in the signals from the steering wheel angle sensor directly and sends information regarding the steering angle via the suspension FlexRay, electronic ignition lock control unit and peripherals CAN to the mono multifunction camera.

Brakes: 

The Electronic Stability Program control unit sends the status of the brake pedal via the suspension FlexRay, electronic ignition lock control unit and peripherals CAN to the mono multifunction camera.

Acceleration: 

The powertrain control unit sends information on the accelerator pedal position over the periphery CAN to the mono multifunction camera.

Turn signaling: 

The steering column tube module control unit directly reads in the switch position of the combination switch and sends it to the mono multifunction camera over the chassis FlexRay, electronic ignition lock control unit and periphery CAN.

Turn rate, lateral acceleration and longitudinal acceleration: 

The acceleration/yaw rate is detected by the acceleration sensor integrated into the Supplemental Restraint System control unit. The supplemental restraint system control unit sends the corresponding values via the vehicle dynamics CAN to the Electronic Stability Program control unit. The Electronic Stability Program control unit evaluates the data and sends it via the suspension FlexRay, electronic ignition lock control unit and peripherals CAN to the mono multifunction camera.

If the mono multifunction camera detects active corner cutting, crossing over of the lane marking at an angle of more than 3° or a lateral acceleration of more than 4 m/s² , a pending warning is suppressed here too.

Function sequence for detection of driver distraction 

Controls located in close proximity of the driver and that affect the attention of the driver when they are operated are monitored by the Active Lane Keeping Assist. If a control intervention is registered, the Active Lane Keeping Assist deems the driver to be "distracted". Control interventions are evaluated by the mono multifunction camera. The warning threshold is adjusted to match the control actuating frequency, i.e. the Active Lane Keeping Assist warns earlier and possibly more often.

The following controls are monitored:

• Audio system controls
• Comfort function controls:
  • Steering column adjustment switch (with CODE 275 (Memory package))
  • Instrument cluster multifunction steering wheel button group or head unit multifunction steering wheel button group
  • Driver-side power window and outside mirror adjustment switch group (only the outside mirror adjustment is monitored)
• Interior illumination controls:
  • Interior lamp automatic function button
  • Left front reading lamp button
  • Right front reading lamp button

Control interventions on audio system: 

The head unit sends information on the control interventions on the audio system to the mono multifunction camera over the user interface CAN, electronic ignition lock control unit and periphery CAN.

Control interventions on comfort functions: 

The steering wheel electronics reads in the control signals on the multifunction steering wheel button groups directly and transmit them to the steering column tube module control unit via the steering wheel CAN. The steering column tube module control unit reads in the control signals from the steering column adjustment switch directly, and sends information about the control interventions on the steering column adjustment switch (with code 275 (Memory package)) and the multifunction steering wheel button groups via the chassis FlexRay, electronic ignition lock control unit and the periphery CAN to the mono multifunction camera.

The left front door control unit reads in the control signals of the driver-side power window and outside mirror adjustment switch group over the left front door LIN and sends them to the mono multifunction camera over the interior CAN, electronic ignition lock control unit and periphery CAN.

Interior illumination control interventions: 

The overhead control panel control unit reads in the status of the interior lamp automatic function button and the front reading lamp buttons directly and sends this over the interior CAN, electronic ignition lock control unit and the periphery CAN to the mono multifunction camera.

Additional function requirements for warning output 

• Lane recognition by the mono multifunction camera
• Vehicle speed 60 to 250 km/h
• Curve radius > 150 m
• Exiting of lane detected (by mono multifunction camera)

Function sequence for issuing warning 

The mono multifunction camera starts the warning sequence as soon as the vehicle crosses the lane markings (broken or solid lines).

For the haptic warning on the steering wheel, the electrical power steering control unit acts on the rack-and-pinion steering gear via the electric power steering actuator motor. The mono multifunction camera sends the warning request over the peripherals CAN, electronic ignition lock control unit and the suspension FlexRay to the electric power steering control unit. The intensity of the haptic warning is adapted to the vehicle speed to cover for perceptible influences from the suspension at high speeds.

The warning is suppressed when the triggering conditions are no longer given or when driver activity is detected (braking, accelerating, steering or turn signaling).

In "Standard" operating mode, a haptic warning is suppressed under the following prerequisites:

• Turn signaling recognized (the warnings are suppressed for a certain period of time)
• Intervention of a driving safety system recognized (e.g. by Electronic Stability Program (ESP®))

In "Adaptive" operating mode, a haptic warning is suppressed under the following prerequisites:

• Turn signaling recognized (the warnings are suppressed for a certain time period)
• Intervention of a driving safety system recognized (e.g. by Electronic Stability Program (ESP®))
• During heavy acceleration (e.g. kickdown)
• During strong braking
• During rapid steering movements (e.g. during an evasive maneuver or during a rapid lane change)
• Corner cutting recognized

Following suppression (driver activity, triggering condition not given), a new warning can be issued in "Standard" mode only after approx. 3 s, in "Adaptive" mode only after approx. 5 s and following turn signaling only after 10 s.

By means of lane recognition and the current vehicle position, the mono 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.

The corresponding information for suppression of the warning is received by the mono multifunction camera over the periphery CAN. If "corner cutting" is detected, the warning is delayed until a defined threshold (lateral acceleration depending on ground speed) is reached. Afterwards, a warning is output.

Additional function requirements for brake intervention 

• Lane width s = 2.6 to 4.4 m (vehicle speed v = 60 to 200 km/h)
• Radius of curve r > 500 m (inner radius), r > 150 m (outer radius)
• ESP® not switched passively
• ESP® not in active diagnostic or roller dynamometer mode
• No active brake intervention detected (e.g. through ABS, ESP®):

  The Electronic Stability Program control unit sends the status of the brake system via the chassis FlexRay, electronic ignition lock control unit and periphery CAN to the mono multifunction camera.

• Tire pressure of all wheels within the tolerance range (run-flat mode not active) (with code 475 (Tire pressure monitor) or code 477 (Tire pressure loss warning)):

  On vehicles with code 475 (Tire pressure monitor), the tire pressure monitor control unit sends the information on the respective tire pressure to the mono multifunction camera via the user interface CAN, electronic ignition lock control unit and periphery CAN.

  On vehicles with CODE 477 (Tire pressure loss warning), the tire pressure is determined based on the rolling circumference. The tire pressure loss warning (RDW) system is functionally integrated in the Electronic Stability Program control unit. The Electronic Stability Program control unit sends the tire pressure information via the chassis FlexRay, electronic ignition lock control unit and periphery CAN to the mono multifunction camera.

• No trailer operation recognized (with code 550 (Trailer hitch)):

  If a trailer is detected, the trailer recognition control unit (with code 550 (Trailer hitch)) sends the "Trailer detected" status via the interior CAN, electronic ignition lock control unit and periphery CAN to the mono multifunction camera.

• 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 it sends out a status signal to enable a course-correcting braking torque.

Function sequence for brake intervention 

If the vehicle crosses a solid lane marking, the mono multifunction camera starts the warning sequence. If the driver fails to respond, the mono multifunction camera calls for brake intervention. To do so, the mono multifunction camera sends the request for active brake intervention via the periphery CAN, electronic ignition lock control unit, and chassis FlexRay to the Electronic Stability Program control unit. The Electronic Stability Program control unit implements this request and actuates the traction system hydraulic unit accordingly.

At the same time as the wheel-specific intervention by the brake system, the driver is visually notified of this activity. The mono multifunction camera sends the corresponding request to the instrument cluster over the periphery CAN, the electronic ignition lock control unit and the user interface CAN. The brake intervention is canceled immediately as soon as driver activity is detected (e.g. if the driver steers against the brake intervention (overrides the brake intervention)) or if the above function requirements are no longer given.

	Electrical function schematic for Active Lane Keeping Assist		PE54.71-P-2053-97FBC
	Table of contents for function description of driver assistance systems		GF54.00-P-0998RFM