Active Lane Keeping Assist, Function - GF54.71-P-0004FHA
Model 238
Up To Model Year 2021
with code 243 (Active Lane Keeping Assist (camera))
except code 23P (Drive package)
Shown on model 238 Up To Model Year 2019
Model 238 from model year 2019
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 on the steering wheel.
Crossing over of lane markings is optically recorded and processed by the mono multifunction camera.
The haptic warning is generated by the steering wheel vibration motor (up to model year 2019) or from 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), acceleration skid control (ASR), the Distance Pilot DISTRONIC or the Active Brake Assist with cross-traffic function, an intervention by the brake system of the Active Lane Keeping Assist 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.
Brake applications are only made 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 chassis FlexRay, electronic ignition lock control unit and periphery CAN to the mono multifunction camera.
Illustration of Active Lane Keeping Assist principle, shown on model 238.3
The Active Lane Keeping Assist comprises the following subfunctions:
- Switch Active Lane Keeping Assist on and off
- Lane recognition
- Detection of driver activity
- Detection of driver distraction
- Warning output
- Brake system intervention
Switch 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.
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.
- Navigation can be operated by voice control. The driver hands-free system microphone sends the signals directly to the head unit.
- Navigation can be performed via the head unit finger navigation pad and the "Back" button on the steering wheel. The corresponding operation signals are sent by the head unit finger navigation pad and the "Back" button over the steering wheel electronics, steering LIN (up to model year 2019) or the steering wheel CAN (as of model year 2019), steering column tube module control unit, suspension FlexRay, electronic ignition lock control unit and the user interface CAN to the head unit.
- With code 246 (Analog clock), the control menu can be called up with the Vehicle button in the upper control panel control unit. 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 touchpad (with code 446 (Touchpad only)) 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.
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
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.
Detection 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 chassis FlexRay, electronic ignition lock control unit and periphery CAN to the mono multifunction camera.
Brakes:
The Electronic Stability Program control unit sends the status of the brake pedal via the chassis FlexRay, electronic ignition lock control unit and periphery 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 chassis FlexRay, electronic ignition lock control unit and periphery 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.
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:
- CRUISE CONTROL lever (up to model year 2019)
- 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 read in the operation signals from the multifunction steering wheel button groups directly and send them over the steering LIN (up to model year 2019) or the steering wheel 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 TEMPOMAT lever directly and sends information to the control interventions over the suspension FlexRay to the mono multifunction camera (up to model year 2019).
The steering column tube module control unit directly reads in the operation signals of the steering column adjustment switch and transmits information on the user interventions to the steering column adjustment switch and the multifunction steering wheel button groups via the suspension FlexRay 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 greater than 150 m
- Leaving of lane
Warning output
Model 238 Up To Model Year 2019
The mono multifunction camera starts the warning sequence as soon as the vehicle crosses the lane markings (broken or solid lines).
The warning is issued haptically by the steering wheel vibration motor, which is integrated into the multifunction steering wheel. The mono multifunction camera transmits the request to actuate the steering wheel vibration motor to the steering column tube module control unit over the periphery CAN, electronic ignition lock control unit and 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.
Model 238 as of model year 2019
The warning is issued haptically by the electric power steering system through 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 mono multifunction camera sends the request to issue a warning and the vibration period over the suspension FlexRay to the electrical power steering control unit, which then actuates 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 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 recognized (e.g. by Electronic Stability Program (ESP®))
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 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 2.6 up to 4.4 m (vehicle speed 60 up to 200 km/h)
- Curve radius greater than 500 m (inner radius), via 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.
Brake system 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-mentioned function requirements are no longer given.
| Electrical function schematic for Active Lane Keeping Assist | Model 238 up to model year 2019 with code 243 (Active Lane Keeping Assist (camera)) except code 23P (Drive package) |
PE54.71-P-2053-97DCB | |
| Model 238 as of model year 2019 up to model year 2021 with code 243 (Active Lane Keeping Assist (camera)) except code 23P (Drive package) | PE54.71-P-2053-97DCD | ||
| Overview of system components for driver assistance systems | GF54.00-P-9998FH |