Active Lane Keeping Assist, Function - GF54.71-P-0004LF
Model 217, 222
up to model year 2018
with code 238 (Active lane keeping Assist)
Function requirements, general
- Engine running or drive train operational
- Soiling and function test on radar sensor system completed successfully
Object detection (e.g. vehicle directly ahead) through the radar sensor system is based on the radar measuring procedure. The front long range radar sensor and the front bumper radar sensors perform a soiling and function test after each engine start to ensure that they are functioning correctly. The function test requires an object to be located in the respective detection area (this object is used as a reference for the function check). If a malfunction is detected or no objects (for the function test) are present in the detection range, the Active Lane Keeping Assist cannot be activated. The front bumper radar sensors send corresponding signals via radar CAN 1, radar sensors control unit and chassis FlexRay to the front long range radar sensor. The front long range radar sensor evaluates these with its own signals and, when all the radar sensors are functioning correctly, sends the "Radar sensor system operational" status via chassis FlexRay to the radar sensors control unit.
The CDI control unit or the ME-SFI [ME] control unit sends the "Engine running" or "Drive train ready" signal to the radar sensors control unit and to the stereo multifunction camera via drive train CAN, powertrain control unit and chassis FlexRay.
Shown model 222.0
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. 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 fails to react to this warning, the radar sensors control unit initiates specific interventions by the brake system to return the vehicle to the traffic 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.
During active control of the Electronic Stability Program (ESP®), anti-lock braking system (ABS), acceleration skid control (ASR), Brake Assist System PLUS (BAS+) and Brake Assist System PLUS cross-traffic (BAS+Q), or during brake intervention by PRE-SAFE or by the Active Blind Spot Assist, brake intervention by the Active Lane Keeping Assist is suppressed or canceled immediately.
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 it via interior CAN, electronic ignition lock control unit and chassis FlexRay to the radar sensors control unit and to the stereo multifunction camera. The "Lane Keeping Assist ON/OFF" message is shown in the instrument cluster. For this purpose, the stereo multifunction camera sends the request to the instrument cluster via the chassis FlexRay, electronic ignition lock control unit and user interface CAN.
The driver also has option of configuring the sensitivity of the Active Lane Keeping Assist in the instrument cluster's "Assistance" menu.
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)
The instrument cluster transmits the selected operating mode via the user interface CAN, the electronic ignition lock control unit and the suspension FlexRay to the stereo multifunction camera.
Active Lane Keeping Assist operation is speed-dependent. The vehicle speed is calculated on the basis of the wheel speeds. The Electronic Stability Program control unit sends it to the radar sensors control unit and to the stereo multifunction camera via chassis FlexRay. In addition, the Electronic Stability Program control unit sends the wheel speeds to the instrument cluster via chassis FlexRay, electronic ignition lock control unit and user interface CAN. The instrument cluster calculates the vehicle speed to be displayed and sends it to the stereo multifunction camera via user interface CAN, electronic ignition lock control unit and chassis FlexRay. The radar sensors control unit calculates the vehicle speed itself.
Additional function requirements for lane recognition
- Detectable lane marking present on both sides (no construction site markings (ambiguous markings), no snow, not covered etc., i.e. not enough contrast)
- Forward travel recognized and gear range "D" selected
- Two lane dividers present
The direction of travel is defined using the wheel rotation direction. The Electronic Stability Program control unit sends corresponding information to the radar sensors control unit and to the stereo multifunction camera via chassis FlexRay.
The fully integrated transmission control unit sends information on the engaged gear range to the radar sensors control unit and to the stereo multifunction camera via drive train CAN, powertrain control unit and chassis FlexRay.
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 analyzes pictures of the lane at a fixed scanning rate and makes these available to the integrated control unit.
Additionally, the stereo multifunction camera sends processed lane data to the radar sensors control unit via the chassis FlexRay.
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 road construction areas), then Active Lane Keeping Assist may not be ready to issue a warning. If tar joints in the road surface are interpreted as lane markings, a warning is suppressed.
Function sequence for recognition of oncoming traffic/parallel traffic
Vehicles in the oncoming lane or the lane running parallel are recognized by the long range and/or short range sensor system. The radar sensors control unit receives the signals of the corresponding radar sensors, checks their plausibility and evaluates them, taking the data of the stereo multifunction camera into account.
The radar sensors control unit reads in the signals of the front long-range radar sensor via the chassis FlexRay. The radar sensors control unit reads in the signals of the front bumper radar sensor via radar CAN 1. The radar sensors control unit reads in the signals of the rear bumper radar sensor via radar CAN 2.
The stereo multifunction camera determines values for the width and the course of the lane and sends these to the radar sensors control unit via the chassis FlexRay.
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 radar sensors control unit determines whether a course-correcting wheel-specific brake intervention 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
- Passing vehicle in the parallel lane
- Vehicle in the parallel lane (at approximately the same level)
Further information on the brake intervention can be found in the "active brake intervention" chapter.
The following diagrams illustrate the situations described above:
Approaching vehicle in the oncoming lane, shown on model 222.0
Vehicles in the oncoming lane are recognized by the following radar sensors using the Active Lane Keeping Assist depending on the distance and the angle to the vehicle:
- Front long-range radar sensor
- Left front bumper radar sensor
Slow vehicle to be passed in the parallel lane, shown on model 222.0
Vehicles in the right or left parallel lane in the area ahead 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:
- Front long-range radar sensor
- Right front bumper radar sensor or left front bumper radar sensor
Passing vehicle in the parallel lane, shown on model 222.0
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:
- Center rear bumper radar sensor
- Left rear bumper radar sensor or right 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 222.0
Vehicles, that are in the right or left lane parallel to and 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 from the vehicle with Active Lane Keeping Assist:
- Right front bumper radar sensor
- Left front bumper radar sensor
- Left rear bumper radar sensor or right 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
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
- Turn signals
- Sporty driving, driving at high cornering speeds or heavy acceleration (vehicle longitudinal and lateral acceleration)
- Cutting a tight corner
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 wheel angle and regarding the steering wheel velocity via the chassis FlexRay to the radar sensors control unit and to the stereo multifunction camera.
Brakes:
The Electronic Stability Program control unit sends the status of the brake pedal via the chassis FlexRay to the radar sensors control unit and to the stereo multifunction camera.
Acceleration:
The CDI control unit or the ME-SFI control unit sends information regarding the accelerator pedal position via the drive train CAN and chassis FlexRay to the radar sensors control unit and to the stereo 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 radar sensors control unit and to the stereo multifunction camera via the chassis FlexRay.
Turn rate, lateral acceleration and longitudinal acceleration:
The turn rate, lateral acceleration and longitudinal acceleration sensor sends the values for vehicle longitudinal and lateral acceleration and yaw rate to the Electronic Stability Program control unit via the vehicle dynamics CAN. The Electronic Stability Program control unit evaluates the data and sends them to radar sensors control unit and to the stereo multifunction camera via the chassis FlexRay.
If the stereo multifunction camera and the radar sensors control unit detect active corner cutting, crossing of the lane markings at an angle ∠ > 3° or a lateral acceleration of a > 4 m/s2
, then a pending warning or an intervention by the brake system 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:
- Cruise control lever
- Steering column adjustment switch (without CODE 443 (Steering wheel heater)) or steering column adjustment and steering wheel heater switch (with CODE 443 (Steering wheel heater))
- Left multifunction steering wheel button group or right 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 audio system is operated using the audio/COMAND control panel. The control interventions on the Audio/COMAND control panel are received by the COMAND controller unit via telematics CAN. The COMAND controller unit sends information on control interventions at the audio system to the stereo multifunction camera via user interface CAN, electronic ignition lock control unit and chassis FlexRay.
Control interventions on comfort functions:
The steering column tube module control unit sends information on the control interventions on the CRUISE CONTROL lever, on the steering column adjustment switch and on the multifunction steering wheel button group to the stereo multifunction camera via the chassis FlexRay.
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 over the steering LIN. 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, the electronic ignition lock control unit and the suspension FlexRay.
Interior illumination control interventions:
The overhead control panel control unit directly reads in the control signals of the interior lamp automatic function button and the front reading lamp buttons and sends them to the stereo multifunction camera via roof LIN, front SAM control unit, interior CAN, electronic ignition lock control unit and chassis FlexRay.
Additional function requirements for warning output
- Lane recognition by the stereo multifunction camera
- Vehicle speed v = 60 to 200 km/h
- Radius of curve r > 150 m
- Exiting of lane detected (by stereo multifunction camera)
- Oncoming traffic, overtaking vehicles or parallel traffic detected in critical area by the radar sensor system when the vehicle crosses a broken line
Function sequence for issuing warning
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 duration of t = 1.5 s. The intensity of the haptic warning is adapted to the vehicle speed, to account 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 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 time period)
- Intervention of a driving safety system recognized (e.g. by the Electronic Stability Program (ESP®), PRE-SAFE® brake 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 by a driving safety system detected (e.g. by ESP®, PRE-SAFE® brake 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. t = 3 s, in "Adaptive" mode only after approx. t = 5 s and following turn signaling 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.
When the "Lane Keeping Assist" menu is activated, a visual warning message is shown in the instrument cluster in addition to the haptic warning. For this purpose, the stereo multifunction camera sends the request to the instrument cluster via the chassis FlexRay, electronic ignition lock control unit and user interface CAN.
Illustration of the warning indicator in instrument cluster, model 222.0
Additional function requirements for active intervention by the brake system
- Active warning by stereo multifunction camera
- No driver activities recognized following a warning
- The lane delimitation crossed is a continuous line
- The lane delimitation crossed is a broken line and oncoming traffic/parallel traffic is detected by the radar sensor system
- Lane width s = 2.6 to 4.4 m (vehicle speed v = 60 to 200 km/h) (exceptions are lane widths of s > 3.9 m where a speed of v < 100 km/h is permitted)
- Radius of curve r > 500 m (inner radius), r > 150 m (outer radius)
- No stationary objects detected by radar sensor system on the vehicle side opposite the intervention (e.g. warning beacons in construction sites)
- ESP® not passively connected (except model 222.077/177/178/179) or ESP® not connected in "SPORT HANDLING MODE" (with model 222.077/177/178/179)
- ESP® not in active diagnostic or roller dynamometer mode
- No autonomous brake interventions recognized (e.g. by ESP®, PRE-SAFE® brake 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))
- No driving with a trailer recognized (for code 550 (Trailer hitch))
- Approval issued for active intervention by the brake system for yawing moment interface
The Electronic Stability Program control unit sends the status of ESP® to the stereo multifunction camera and to the radar sensors control unit via chassis FlexRay.
On vehicles with CODE 475 (Tire pressure monitor), the tire pressure monitor control unit sends the information on the respective tire pressure to the stereo multifunction camera and to the radar sensors control unit via user interface CAN, electronic ignition lock control unit and chassis 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 (RDW) system is functionally integrated in the Electronic Stability Program control unit.
The Electronic Stability Program control unit sends information on tire pressure to the stereo multifunction camera and to the radar sensors control unit via chassis FlexRay.
When a trailer is recognized, the trailer recognition control unit (with code (550) (Trailer hitch)) sends the status "Trailer recognized" to the stereo multifunction camera and to the radar sensors control unit via the interior CAN, the electronic ignition lock control unit and the suspension FlexRay.
Function sequence for active intervention by the brake system
If the vehicle crosses over a continuous line on the right side of the vehicle, for example, the radar sensors control unit decides whether and with which intensity a course-correcting intervention by the brake system is to take place.
If the stereo multifunction camera does not detect any driver activity at the same time and also does not detect any stationary objects on the vehicle side facing away from the intervention, the radar sensors control unit issues approval for the intervention by the brake system. The radar sensors control unit sends the request for wheel-specific (active) braking of the left side of the vehicle to the Electronic Stability Program control unit via chassis FlexRay. 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.
| Electrical function schematic for Active Lane Keeping Assist | PE54.71-P-2053-97SEA | ||
| Overview of system components for driver assistance systems | GF54.00-P-9998LF |