Active Lane Keeping Assist, Function - GF54.71-P-0004RFM
Model 205
as of model year 2019
with code 23P (Driving Assistance package)
Model 253 (except 253.99)
as of model year 2020
with code 23P (Driving Assistance package)
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. If the short-range and long range radar sensor is functioning correctly, it sends the "radar sensor system operational" status via the suspension FlexRay to the Mercedes-Benz Intelligent Drive control unit.
- Stereo multifunction camera soiling and function test:
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 the status via the suspension FlexRay to the Mercedes-Benz Intelligent Drive control unit.
Schematic diagram, shown on model 205.0
Active Lane Keeping Assist, general
The Active Lane Keeping Assist detects when lane markings are driven over and issues a haptic warning to the driver in certain situations via steering gear vibrations.
Crossing over lane markings is optically recorded and processed by the stereo multifunction camera.
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 does not react to the warning, the Mercedes-Benz Intelligent Drive control unit initiates targeted brake interventions in order to move the vehicle back into lane.
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.
Brake intervention by the Active Lane Keeping Assist is suppressed or immediately aborted if there is active control by one of the following systems:
- Electronic Stability Program (ESP®)
- Anti-lock braking system (ABS)
- Acceleration slip regulation (ASR)
- Active Brake Assist with intersection function
- Active Blind Spot Assist
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 crosses a continuous line (lane delimitation) at an angle of 3°, when the lane is delimited by two lane markings or, in the case of a broken line, when there is a vehicle in the oncoming lane or on a lane running in parallel in a collision-critical area.
The Active Lane Keeping Assist comprises the following subfunctions:
- Function sequence for Active Lane Keeping Assist ON and OFF
- Function sequence for lane recognition
- Function sequence for recognition of oncoming traffic/parallel traffic
- 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 Active Lane Keeping Assist ON and OFF
The Active Lane Keeping Assist can be switched off and on 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 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 multifunction display of the instrument cluster. For this purpose, the Mercedes-Benz Intelligent Drive control unit sends the request via the suspension FlexRay, electronic ignition lock control unit and user interface CAN to the instrument cluster.
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 code 446 (Touchpad only), navigation can be performed using the Audio/COMAND control panel. The Audio/COMAND control panel transmits the relevant control signals via the telematics CAN to the head unit.
- With code 446 (Touchpad only) or code 448 (Touchpad), navigation can be performed using the touchpad. The touchpad sends the relevant operation signals to the head unit via the telematics CAN.
- 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.
- 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 upper control panel control unit transmits the "Vehicle" button status via the LCP-LIN, Audio/COMAND control panel (except code 446 (Touchpad only)) or the touchpad (with code 446 (Touchpad only)) and telematics CAN to the head unit.
The head unit sends the selected operating mode via the user interface CAN, electronic ignition lock control unit and suspension FlexRay to the Mercedes-Benz Intelligent Drive control unit and to the stereo multifunction camera. The Mercedes-Benz Intelligent Drive control unit stores the current operating mode and, when restarted, sends it via the suspension FlexRay, electronic ignition lock control unit and user interface CAN to the head unit.
The following operating modes can be selected:
- Standard (Sensitivity increased, warnings issued earlier and more frequently)
- Adaptive (reduced sensitivity, warnings issued later and less often)
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 (transmission 722, 724, 725) transmits information on the engaged drive range via the drive CAN, powertrain control unit and suspension FlexRay to the Mercedes-Benz Intelligent Drive control unit and the stereo multifunction camera.
Function sequence for 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. going 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 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 and the stereo multifunction camera. The Mercedes-Benz Intelligent Drive control unit receives the signals of the short and long range radar sensor and the stereo multifunction camera, subjects these to a plausibility check 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 rear outer bumper radar sensors on the left and right via radar CAN 2.
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 values such as the speed of the two vehicles, the 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 the oncoming lane, shown on model 205.0
Vehicles in the oncoming lane are detected by the following radar sensors 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 passed in the parallel lane, shown on model 205.0
Vehicles in the right or left parallel lane in the area ahead are recognized by the following radar sensors 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
Passing vehicle in the parallel lane, shown on model 205.0
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 the parallel lane is at approximately the same level as the vehicle with Active Lane Keeping Assist, shown on model 205.0
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 your lane (e.g. bicycle).
- Moving obstacle detected behind lane delimitation (hard shoulder) in case of narrow lane.
Function sequence for recognition 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 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 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 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 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 over of the lane marking at an angle of
> 3° or lateral acceleration of a > 4 m/s2
, then here too a pending warning or a brake application is suppressed.
Function sequence for recognition 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:
- 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 the control interventions on the audio system to the stereo multifunction camera via user interface CAN, electronic ignition lock control unit, chassis FlexRay.
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 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
- Radius of curve r > 150 m
- Exiting of lane detected (detected by stereo multifunction camera)
Function sequence for issuing warning
The stereo multifunction camera starts the warning sequence once the vehicle has driven over the lane markings (broken or solid white 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 stereo multifunction camera transmits the warning request via the suspension FlexRay to the electrical power steering control unit.
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:
- 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 certain time period)
- Intervention of a driving safety system detected (e.g. through 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
Another warning issued after a suppression (driver activity, trigger condition not given) is only possible in the "Standard" ode after approx. t = 3 s, in the "Adaptive" mode only after approx. t = 5 s, and after a turn signal indication only after t = 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
- Lane warner is ready to intervene.
- No driver activities detected.
- No obstacle detected within your lane.
- The lane marking crossed is a continuous line.
- The lane marking crossed is a broken line and oncoming traffic/parallel traffic is recognized by the radar sensor system or the stereo multifunction camera.
- Lane width s = 2.6 to 4.7 m (vehicle speed v = 60 to 210 km/h)
- Radius of curve r > 500 m (inner radius), r > 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 interventions 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)):
For vehicles with code 475 (Tire pressure monitoring), the tire pressure monitoring control unit transmits the information on the respective tire pressure via the user interface CAN, electronic ignition lock control unit and suspension FlexRay to the stereo multifunction camera and the Mercedes-Benz Intelligent Drive control unit.
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 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.
Function sequence for active intervention by the brake system
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.
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.
In the event of brake intervention, a visual warning message is shown in the multifunction display of the instrument cluster. The stereo multifunction camera sends the request to output a warning to the instrument cluster via the chassis FlexRay, electronic ignition lock control unit and user interface CAN.
Appearance of warning indication
| Electrical function schematic for Active Lane Keeping Assist | PE54.71-P-2053-97FBB | ||
| Table of contents for function description of driver assistance systems | GF54.00-P-0998RFM |