Active Lane Keeping Assist, Function - GF54.71-P-0004FG
Model 213 up to model year 2021 with code 238 (Active lane keeping Assist)
except code 243 (Active Lane Keeping Assist (camera))
Function requirements, general
- Engine running or drive train operational: The CDI control unit or the ME-SFI control unit sends the "engine running" or "drivetrain operational" signal via the drive CAN, powertrain control unit and suspension FlexRay to the Mercedes-Benz Intelligent Drive control unit and to the stereo multifunction camera.
- Front radar sensor system soiling and function test completed successfully: Object detection (e.g. vehicle directly ahead) through the radar sensor system is based on the radar measuring procedure. Each time the engine is started, the short-range and long-range radar sensor performs a soiling and function test in order to ensure that the radar sensor is functioning correctly. The function test requires an object to be positioned in the detection range. If a malfunction is established or if there are no objects in the detection area, Active Lane Keeping Assist cannot be activated. The short and long range radar, when functioning properly, transmits the status "Radar sensor system operational" via the suspension FlexRay to the Mercedes-Benz Intelligent Drive control unit.
- Stereo multifunction camera soiling and function test completed successfully: The stereo MFK performs a soiling and function test to ensure proper operation after each engine start. The function test requires an object to be located in the detection area (this object is used 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. The stereo multifunction camera sends its status via the suspension FlexRay to the Mercedes-Benz Intelligent Drive control unit.
Illustration showing principle of Active Lane Keeping Assist; illustration shows model 213.0
Active Lane Keeping Assist, general
The Active Lane Keeping Assist detects when the vehicle crosses lane markings, and issues a haptic warning to the driver in certain situations by initiating vibrations on the steering wheel.
Crossing over lane markings is optically recorded and processed by the stereo multifunction camera.
The haptic warning is generated by the steering wheel vibration motor (up to model year 2019) or by the electric power steering actuator motor (as of model year 2019).
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.
With active regulation of the Electronic Stability Program (ESP®), anti-lock braking system (ABS), anti-slip control (ASR), Active Distance Assist DISTRONIC or Active Brake Assist with cross-traffic function, a brake application of the Active Lane Keeping Assist system is suppressed or immediately aborted.
Warnings are issued as soon as the vehicle is in the direct vicinity of a broken or solid line or crosses over it.
Interventions by the brake system only occur when the vehicle quickly approaches or crosses a continuous line (lane delimitation), when the lane is delimited by two lane markings or, in the case of a broken line, when there is a vehicle in a collision-critical area in the oncoming lane or in a parallel lane.
The Active Lane Keeping Assist comprises the following subfunctions:
- Switch Active Lane Keeping Assist on and off
- Lane recognition
- Recognition of oncoming traffic/parallel traffic
- Detection of driver activity
- Detection of control interventions
- Warning output
- Active brake application
Switch Active Lane Keeping Assist on and off
Active Lane Keeping Assist can be switched on and off by pressing the Lane Keeping Assist button on the driver side instrument panel button group. The front SAM control unit reads in the status of the Lane Keeping Assist button via the instrument panel LIN and sends the status via the interior CAN, electronic ignition lock control unit and suspension FlexRay to the Mercedes-Benz Intelligent Drive control unit and to the stereo multifunction camera. The "Lane Keeping Assist ON/OFF" message is shown in the instrument cluster. The Mercedes-Benz Intelligent Drive control unit sends the request for this to the instrument cluster via the suspension FlexRay, electronic ignition lock control unit and user interface CAN.
The driver also has the option of setting the operating mode of the Active Lane Keeping Assist in the "Assistance" menu of the head unit.
The following operating modes can be selected:
- Standard: sensitivity increased, warnings issued earlier and more frequently.
- Adaptive: sensitivity reduced, warnings issued later and less often. The following options are available for navigating in the control menu:
- Except code 446 (Touchpad only), navigation in the control menu is performed using the Audio/COMMAND control panel. The Audio/COMMAND control panel sends the control signals via telematics CAN to the head unit.
- With code 446 (Touchpad only) or code 448 (Touchpad), navigation is performed using the touchpad. The touchpad sends the operation signals over the telematics CAN to the head unit.
- With code 531 (COMMAND APS), navigation in the control menu can be performed via voice control. For this purpose, the head unit evaluates the voice commands via the driver's hands-free system microphone.
- Navigation in the control menu can also be performed using the finger navigation pad head unit and the "Back" button on the steering wheel. The steering wheel electronics read in the operation signals from the finger navigation pad heat unit and the "Back" button and transmit the signals to the head unit via the steering LIN (up to model year 2019) or steering wheel CAN (as of model year 2019), the steering column tube module control unit, the suspension FlexRay, the electronic ignition lock control unit and the user interface CAN.
- With code 246 (Analog clock), the control menu can be called up with the Vehicle button in the upper control panel control unit. The upper control panel control unit reads in the status of the vehicle button and sends it to the head unit via the LCP-LIN, Audio/COMMAND control panel (except 446 (Touchpad only)) or touchpad (with code 446 (Touchpad only)) and telematics CAN.
The head unit sends the status of the Active Lane Keeping Assist via the user interface CAN, electronic ignition lock control unit and the suspension FlexRay to the Mercedes-Benz Intelligent Drive control unit and to the stereo multifunction camera. The Mercedes-Benz Intelligent Drive control unit stores this and, when restarted, sends it via the suspension FlexRay, electronic ignition lock control unit and user interface CAN to the head unit.
Active Lane Keeping Assist operation is speed-dependent. The vehicle speed is calculated from the wheel speed. The Electronic Stability Program control unit sends it via the suspension FlexRay to the Mercedes-Benz Intelligent Drive control unit and to the stereo multifunction camera. The Mercedes-Benz Intelligent Drive control unit and the stereo multifunction camera use the wheel speed signals to calculate the vehicle speed.
Additional function requirements for lane recognition
- Recognizable lane markings present on both sides (no construction site markings (ambiguous markings), no snow, not covered, etc.)
- Forward travel recognized and gear range "D" selected: The direction of travel is defined using the wheel rotation direction. The Electronic Stability Program control unit sends the corresponding information via the suspension FlexRay to the Mercedes-Benz Intelligent Drive control unit and to the stereo multifunction camera.
The fully integrated transmission control unit sends information on the engaged drive range via the drive train CAN, powertrain control unit and suspension FlexRay to the Mercedes-Benz Intelligent Drive control unit and to the stereo multifunction camera.
Lane recognition
The stereo multifunction camera is mounted at the top center of the windshield and records the road space in front of the vehicle. The stereo multifunction camera documents images of the lane at a fixed scanning rate, uses them to calculate the lane data and sends this data via the suspension FlexRay to the Mercedes-Benz Intelligent Drive control unit.
Schematic of lane recognition by stereo multifunction camera
The stereo multifunction camera calculates the lane on the basis of two different lane algorithms that are implemented in the stereo multifunction camera. If a comparison of the two lane algorithms results in a match, the stereo multifunction camera uses it to generate a safe lane.
The stereo multifunction camera uses this data to calculate 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.
Recognition of oncoming traffic/parallel traffic
Vehicles that are in the oncoming lane or on the lane running parallel are detected by the short-range and long-range radar sensor, by the stereo multifunction camera and by the outer rear bumper radar sensors. The Mercedes-Benz Intelligent Drive control unit receives the signals from the short-range and long-range radar sensor, the stereo multifunction camera and the outer rear bumper radar sensors and evaluates them.
The short-range and long-range radar sensor is heated by a radome heater that it actuates directly.
The Mercedes-Benz Intelligent Drive control unit reads in the signals from the short-range and long-range radar sensor via the suspension FlexRay. The Mercedes-Benz Intelligent Drive control unit reads in the signals from the outer rear bumper radar sensors via the radar CAN.
The stereo multifunction camera determines the values for the width and course of the lane and sends them via the suspension FlexRay to the Mercedes-Benz Intelligent Drive control unit.
Based on the evaluation of the speed of the two vehicles, their respective relative position on the lane and the course of the lane, the Mercedes-Benz Intelligent Drive control unit determines whether a course-correcting wheel-specific brake application is required.
The following situations can lead to a course-correcting brake intervention when changing to the parallel lane/oncoming lane:
- Approaching vehicle in the oncoming lane
- Slower vehicle to be passed in the parallel lane
- Overtaking vehicle in the parallel lane
- Vehicle in the parallel lane (at approximately the same level)
- Guardrails or a series of stationary vehicles behind the lane markings
Approaching vehicle in oncoming lane, shown on model 213.0
Vehicles in the oncoming lane are detected by the following components depending on the distance and the angle to the vehicle with Active Lane Keeping Assist:
- Short and long-range radar sensor
- Stereo multifunction camera
Slow vehicle to be overtaken in parallel lane, shown on model 213.0
Vehicles in the right or left parallel lane in the area ahead are recognized by the following components depending on the side of the lane, the distance and the angle to the vehicle with Active Lane Keeping Assist:
- Short and long-range radar sensor
- Stereo multifunction camera
Overtaking vehicle in parallel lane, shown on model 213.0
Vehicles approaching from behind with a high relative speed compared to the vehicle with Active Lane Keeping Assist are detected by the following radar sensors depending on which lane and on the distance and angle to the vehicle with Active Lane Keeping Assist:
- Right outer rear bumper radar sensor
- Left outer rear bumper radar sensor
Vehicle in parallel lane at approximately same level as vehicle with Active Lane Keeping Assist, shown on model 213.0
Vehicles in the right or left parallel lane level with the vehicle with Active Lane Keeping Assist are detected by the following radar sensors depending on which lane and on the distance and angle to the vehicle with Active Lane Keeping Assist:
- Right outer rear bumper radar sensor
- Left outer rear bumper radar sensor
The following situations can lead to a cancellation of the course-correcting brake intervention:
- Vehicle detected with short distance in the rear area in own lane (tailgating scenario)
- Obstacle detected in own lane (e.g. bicycle)
- Driving obstacle detected behind the lane delimitation (hard shoulder) with narrow lane
Detection of driver activity
The following situations suggest driver activity and result in suppression of any pending warning or brake intervention:
- Clearly active steering, braking or accelerating
- Cutting a tight corner
- Turn signals
- Sporty driving (e.g. high cornering speeds or heavy 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 on the steering wheel angle and on the steering wheel velocity via the suspension FlexRay to the Mercedes-Benz Intelligent Drive control unit and to the stereo multifunction camera. Brakes:
The Electronic Stability Program control unit sends the status of the brake pedal via the suspension FlexRay to the Mercedes-Benz Intelligent Drive control unit and to the stereo multifunction camera.
Acceleration:
The powertrain control unit sends information on the accelerator pedal position via the suspension FlexRay to the Mercedes-Benz Intelligent Drive control unit and to the stereo multifunction camera.
Turn signaling:
The steering column tube module control unit reads in the switch position of the combination switch directly and sends it via the suspension FlexRay to the Mercedes-Benz Intelligent Drive control unit and to the stereo multifunction camera.
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 corresponding values over 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 to the Mercedes-Benz Intelligent Drive control unit and to the stereo multifunction camera.
If the stereo multifunction camera and the Mercedes-Benz Intelligent Drive control unit detect active corner cutting, crossing of the lane markings at a large angle or a high lateral acceleration, a pending warning or brake application is also suppressed here.
Detection of control interventions
Controls located in close proximity of the driver and that affect the attention of the driver when they are operated are monitored. If a control intervention is registered, the Active Lane Keeping Assist deems the driver to be "distracted". Control interventions are evaluated by the stereo 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. An active warning is output as soon as the vehicle is in the direct proximity of or crosses over the lane marking. The following controls are monitored:
- Audio system controls
- Comfort function controls:
- CRUISE CONTROL lever (up to model year 2019)
- Steering column adjustment switch
- 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 user interventions at the audio system to the mono multifunction camera via the user interface CAN, electronic ignition lock control unit and suspension FlexRay. Control interventions on comfort functions:
The steering wheel electronics read in the operation signals from the multifunction steering wheel button groups directly and send them via the steering LIN (up to model year 2019) or steering CAN (as of model year 2019) to the steering column tube module control unit. The steering column tube module control unit reads in the operation signals from the CRUISE CONTROL lever directly and sends information on the control intervention via the suspension FlexRay to the stereo multifunction camera (up to model year 2019). The steering column tube module control unit reads in the operation signals of steering column adjustment switch directly and sends information on the control interventions at the steering column adjustment switch and at the multifunction steering wheel button groups to the stereo multifunction camera via the suspension FlexRay. The left front door control unit reads in the control signals of the driver-side power window and outside mirror adjustment switch group via left front door LIN and sends them to the stereo multifunction camera via interior CAN, electronic ignition lock control unit and chassis FlexRay. Interior illumination control interventions:
The overhead control panel control unit reads in the operation signals of the interior lamp automatic function button and the front reading lamp buttons directly and sends them via the interior CAN, electronic ignition lock control unit and the chassis FlexRay to the stereo multifunction camera.
Additional function requirements for warning output
- Lane recognition by the stereo multifunction camera
- Vehicle speed 60 to 250 km/h
- Curve radius greater than 150 m
- Exiting of lane detected (detected by stereo multifunction camera) Warning output
Up to model year 2019
- Turn signaling recognized (the warnings are suppressed for a certain period of time)
- Intervention of a driving safety system detected (e.g. by Electronic Stability Program (ESP®), Active Brake Assist with intersection function or Active Blind Spot Assist)
In "Adaptive" mode, a haptic warning is suppressed under the following prerequisites:
Turn signaling recognized (the warnings are suppressed for a
The warning is issued haptically by the steering wheel vibration motor, which is integrated into the multifunction steering wheel. The stereo multifunction camera sends the request to actuate the steering wheel vibration motor to the steering column tube module control unit via the chassis FlexRay. The steering column tube module control unit sends this request over the steering LIN to the steering wheel electronics, which then actuates the steering wheel vibration motor.
The steering wheel vibration motor is actuated for a period of 1.5 s.
The intensity of the haptic warning is adapted to the vehicle speed in order to allow for the perceivable effects of the suspension at high speeds.
As of model year 2019
The warning is issued haptically by the electric power steering system via the multifunction steering wheel. The intensity of the haptic warning is adapted to the vehicle speed in order to allow for the effects of the suspension at high speeds. The stereo multifunction camera sends the request to output a warning and the vibration time via the suspension FlexRay to the electrical power steering control unit, which reacts by actuating the electric power steering actuator motor.
The warning is suppressed when the triggering conditions are no longer given or when driver activity is detected (braking, accelerating, steering and/or turn signaling).
In "Standard" mode, a haptic warning is suppressed under the following prerequisites:
- Certain period of time)
- Intervention of a driving safety system detected (e.g. by Electronic Stability Program (ESP®), Active Brake Assist with intersection function or Active Blind Spot Assist)
- Heavy acceleration (e.g. kickdown)
- Strong braking
- 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 stereo 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 stereo multifunction camera via the chassis FlexRay. 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 active intervention by the brake system
- Stereo multifunction camera ready to operate
- No driver activity detected
- No obstacle detected within own lane
- The lane delimitation crossed is a continuous line
- The lane delimitation crossed is a broken line and oncoming traffic/parallel traffic is recognized by the radar sensor system or the stereo multifunction camera
- Lane width 2.6 up to 4.7 m (vehicle speed 60 up to 200 km/h)
- Curve radius greater than 500 m (inner radius), greater than 150 m (outer radius)
- ESP® not switched to passive:
The Electronic Stability Program control unit sends the status of the ESP® via the suspension FlexRay to the stereo multifunction camera and to the Mercedes-Benz Intelligent Drive control unit
- ESP® not in active diagnostic or roller dynamometer mode
- No autonomous brake applications detected (e.g. by ESP®, Active Brake Assist with cross-traffic function or Active Blind Spot Assist)
- 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 monitoring system), the tire pressure monitoring system control unit sends the information on the respective tire pressure to the stereo multifunction camera and to the Mercedes-Benz Intelligent Drive control unit via the user interface CAN, electronic ignition lock control unit and suspension FlexRay
On vehicles with CODE 477 (Tire pressure loss warning), the tire pressure is determined based on the rolling circumference. The tire pressure loss warning system is functionally integrated in the Electronic Stability Program control unit. The Electronic Stability Program control unit sends the information on the tire pressure via the suspension FlexRay to the stereo multifunction camera and to the Mercedes-Benz Intelligent Drive control unit
- 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 suspension FlexRay to the stereo multifunction camera and to the Mercedes-Benz Intelligent Drive control unit
- 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.
Active brake application
If the vehicle, for example, crosses over a continuous line on the right side of the vehicle, the Mercedes-Benz Intelligent Drive control unit decides whether and with which intensity a course-correcting brake application is to take place.
When the stereo multifunction camera does not detect any driver activity or any obstacles in the vehicle surroundings, the Mercedes-Benz Intelligent Drive control unit enables brake application.
The Mercedes-Benz Intelligent Drive control unit sends the request for wheel-specific (active) braking on the wheel side opposite the line via the suspension 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.
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.
The stereo multifunction camera sends the corresponding request to the instrument cluster via the chassis FlexRay, electronic ignition lock control unit and 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.
Appearance of warning indication
| Electrical function schematic for Active Lane Keeping Assist | Model 213 up to model year 2019 with code 238 (Active lane keeping Assist) except code | PE54.71-P-2053-97DBA | |
| 243 (Active Lane Keeping Assist (camera)) Model 213 as of model year 2019 up to model year 2021 with code 238 (Active lane keeping Assist) except code 243 (Active Lane Keeping Assist (camera)) | PE54.71-P-2053-97DBC | ||
| Overview of system components for driver assistance systems | GF54.00-P-9998FG |