Lane Keeping Assist, Function - GF54.71-S-0005TRA
Model 447.6/7/8
With Code JW5 (Lane keeping assist)
except code XM0 (Facelift)
Model 448.8
With Code JW5 (Lane keeping assist)
Shown: model 447.8 (with engine 651)
Shown on model 447.6/7 (with engine 622, 651)
Function requirements in general
- Engine running or drive train operational
The CDI control unit or ME-SFI control unit (N3/34) sends the "Engine running" or the "Drivetrain ready" signal via chassis CAN to the electronic ignition lock control unit (EZS), from there, via front end CAN to the multifunction camera (MFK) control unit.
Leaving lane with warning, schematic diagram
Lane Keeping Assist, general
The Lane Keeping Assist detects when the vehicle crosses lane markings, and issues a haptic warning to the driver in certain situations by means of vibrations at the steering wheel.
Crossing over lane markings is optically recorded and processed by the multifunction camera (MFK) control unit.
The haptic warning is generated by the steering wheel vibration motor. The Lane Keeping Assist takes the driver's behavior into consideration and decides the point at which a warning is to be issued.
Warnings are issued as soon as the vehicle is in the direct vicinity of a broken or solid line or crosses over it.
The Lane Keeping Assist consists of the following subfunctions:
- Function sequence for Lane Keeping Assist ON and OFF
- Function sequence for lane recognition
- Function sequence for recognition of driver activity
- Function sequence for recognition of control interventions
- Function sequence for issuing warning
Lane Keeping Assist, shown on model 447.8
Function sequence for Lane Keeping Assist ON and OFF
The Lane Keeping Assist can be switched off and on by pressing the Lane Keeping Assist button in the driver assistance systems operating panel control unit. The signal acquisition and actuation module (SAM) control unit reads in the status of the Lane Keeping Assist button via the instrument panel LIN and sends it via the interior CAN, electronic ignition lock (EIS) control unit and front end CAN to the multifunction camera (MFK) control unit.
The message "Lane Keeping Assist ON/OFF" is displayed in the multifunction display of the instrument cluster (IC) control unit. Here, the multifunction camera (MFK) control unit transmits the request via:
- Model 447.8 or model 448.8
- Front end CAN, electronic ignition lock (EZS) control unit, chassis CAN, gateway for user interface CAN and user interface CAN to the instrument cluster (IC) control unit.
- Model 447.6/7
- Front end CAN, electronic ignition lock (EZS) control unit and chassis CAN to the instrument cluster (IC) control unit.
In addition the driver can adjust the sensitivity of the Lane Keeping Assist in the "Assistance" menu of the instrument cluster (IC) control unit.
The following operating modes are available for selection:
- Standard (Sensitivity increased, warnings issued earlier and more frequently)
- Adaptive (reduced sensitivity, warnings issued later and less often)
The instrument cluster (IC) control unit transmits the selected operating mode via:
- Model 447.8 or model 448.8
- User interface CAN, gateway for user interface CAN, chassis CAN, electronic ignition lock (EZS) control unit and front end CAN to the multifunction camera (MFK) control unit.
- Model 447.6/7
- Chassis CAN, electronic ignition lock (EZS) control unit and front end CAN to the multifunction camera (MFK) control unit.
Lane Keeping Assist operation is speed-dependent. The vehicle speed is calculated on the basis of the wheel speeds. The Electronic Stability Program (ESP) control unit sends the vehicle speed via the chassis CAN, electronic ignition lock (EIS) control unit and the front end CAN to the multifunction camera (MFK control unit. In addition, the Electronic Stability Program (ESP) control unit transmits the vehicle speed via:
- Model 447.8 or model 448.8
- Chassis CAN, gateway for user interface CAN and user interface CAN to the instrument cluster (IC) control unit.
- Model 447.6/7
- Chassis CAN to the instrument cluster (IC) control unit.
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 detected and gear range "D" (with transmission 722.9) selected
- 2 lane dividers present
The direction of travel is defined using the wheel rotation direction. The Electronic Stability Program (ESP) control unit sends corresponding information via the chassis CAN, electronic ignition lock (EIS) control unit and the front end CAN to the multifunction camera (MFK) control unit.
The fully integrated transmission (VGS) control unit (with transmission 722 9) transmits information on the engaged gear range via the drive train CAN, CDI control unit or ME-SFI control unit chassis CAN, electronic ignition lock (EZS) control unit and front end CAN to the multifunction camera (MFK) control unit.
Function sequence for lane recognition
The multifunction camera (MFK) control unit is mounted at the top center of the windshield and records the road space in front of the vehicle. The multifunction camera (MFK) control unit records pictures of the lane at a fixed scanning rate and makes these pictures available to the integrated control unit.
Schematic diagram showing lane recognition by multifunction camera (MFK) control unit
Based on the recorded picture sequences and the measurement values resulting from the lane markings, the multifunction camera (MFK) control unit calculates each lane. This calculation is based on a corresponding algorithm.
From this data, the multifunction camera (MFK) control unit 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 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 driver activity
The following situations suggest driver activity and result in suppression of any pending warning:
- Clearly active steering
- Brakes
- Accelerate
- Cutting a tight corner
- Turn signals
- Sporty driving at high cornering speeds or with high acceleration
Clearly active steering:
Steering movements are detected by the steering angle sensor. The steering column tube module (MRM) control unit reads in the signals from the steering angle sensor directly and sends information about the steering wheel angle and the steering wheel velocity to the multifunction camera (MFK) control unit via the chassis CAN, electronic ignition lock (EIS) control unit and front end CAN.
Brakes:
The Electronic Stability Program (ESP) control unit sends the status of the brake pedal via the chassis CAN, electronic ignition lock (EIS) control unit and the front end CAN to the multifunction camera (MFK) control unit.
Acceleration:
The CDI control unit or ME-SFI control unit sends information regarding the accelerator pedal position via chassis CAN, electronic ignition lock (EIS) control unit and the front end CAN to the multifunction camera (MFK) control unit.
Cutting a tight corner:
Cutting a tight corner is detected by the multifunction camera (MFK) control unit when the vehicle crosses the lane marking at a angle ∠ > 3°.
Turn signaling:
The steering column tube module (MRM) control unit reads in the switch position of the combination switch directly and sends it via the chassis CAN, electronic ignition lock (EIS) control unit and front end CAN to the multifunction camera (MFK) control unit.
Sporty driving, with high cornering speeds or heavy acceleration:
The acceleration/yaw rate is detected by the acceleration sensor integrated in the Electronic Stability Program (ESP) control unit. The Electronic Stability
Program (ESP) control unit evaluates the data and sends it via the chassis CAN, electronic ignition lock (EIS) control unit and front end CAN to the multifunction camera (MFK) control unit.
If the multifunction camera (MFK) control unit detects a lateral acceleration of a > 4 m/s2
, a pending warning is also suppressed here.
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 Lane Keeping Assist deems the driver to be "distracted". Control interventions are evaluated by the multifunction camera (MFK) control unit. The warning threshold is adjusted to match the control actuating frequency, i.e. the Lane Keeping Assist warns earlier and possibly more often. A warning is issued as soon as the vehicle is in the direct proximity of or crosses over the lane marking.
The following controls are monitored:
- Controls of the audio system (model 447.8 or model 448.8).
- Controls of the audio system (model 447.6/7).
- CRUISE CONTROL lever (With Code MS1 (Cruise control) and with or without CODE ET4 (DISTRONIC PLUS ))
- Left multifunction steering wheel button group and right multifunction steering wheel button group
- Driver door control panel (only the outside mirror adjustment is monitored)
- Interior lamp automatic function button and left front reading lamp button
Controls of the audio system (model 447.8 or model 448.8):
The audio system is operated using the central operating unit (COU) control unit. The control interventions at the central operating unit (COU) control unit are received by the radio (Audio/COMAND) via the telematics CAN. The radio (Audio/COMAND) sends information on control interventions at the audio system via the user interface CAN, gateway for the user interface CAN, chassis CAN, electronic ignition lock (EIS) control unit and front end CAN to the multifunction camera (MFK) control unit.
Controls of the audio system (model 447.6/7) :
The radio (Audio) transmits information on operating interventions in the audio system via the interior CAN, electronic ignition lock (EZS) control unit, front end CAN to the multifunction camera (MFK) control unit.
CRUISE CONTROL lever (With Code MS1 (Cruise control) and with or without CODE ET4 (DISTRONIC PLUS) ):
The steering column tube module (MRM) control unit sends information on control interventions at the cruise control lever via the chassis CAN, electronic ignition lock (EIS) control unit and front end CAN to the multifunction camera (MFK) control unit.
Left multifunction steering wheel button group and right multifunction steering wheel button group :
The steering column tube module (MRM) control unit receives the control signals from the left and right multifunction steering wheel button group from the steering wheel electronics via the steering LIN and sends this information via the chassis CAN, electronic ignition lock (EIS) control unit and front end CAN to the multifunction camera (MFK) control unit.
Driver door control panel (only the outside mirror adjustment is monitored) :
The left front door control unit reads in the control signals from the left front door control panel via the left front door LIN and sends them via the interior CAN, electronic ignition lock (EIS) control unit and front end CAN to the multifunction camera (MFK) control unit.
Interior lamp automatic function button and left front reading lamp button:
The overhead control panel (OCP) control unit reads in the control signals from the interior lamp automatic function button and the left front reading lamp button directly and sends them via the roof LIN to the signal acquisition and actuation module (SAM) control unit. The signal acquisition and actuation module (SAM) control unit sends them via the interior CAN, electronic ignition lock (EIS) control unit and front end CAN to the multifunction camera (MFK) control unit.
Additional function requirements for warning output
- Lane recognition by multifunction camera (MFK) control unit
- Vehicle speed v = 60 to 200 km/h
- Radius of curve = r > 150 m
- Exiting of lane detected (detected by multifunction camera (MFK) control unit)
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 multifunction camera (MFK) control unit sends the request to actuate the steering wheel vibration motor via the front end CAN, electronic ignition lock (EIS) control unit and chassis CAN to the steering column tube module (MRM) control unit. The steering column tube module (MRM) control unit sends this request 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 in order to allow for the perceivable effects of the suspension at high speeds.
The warning is suppressed when the triggering conditions are no longer given or when driver activity is detected (braking, accelerating, steering or turn signaling).
In "Standard" 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 the Electronic Stability Program (ESP) control unit or Blind Spot Assist (with CODE JA7 I 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. by the Electronic Stability Program (ESP) control unit or Blind Spot Assist (with CODE JA7 Blind Spot Assist))
- Heavy acceleration (e.g. kickdown)
- Strong braking
- Rapid steering movement (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 = 10s.
By means of lane recognition and the current vehicle position, the multifunction camera (MFK) control unit 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 multifunction camera (MFK) control unit via the front end 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.
| Electrical function schematic for Lane Keeping Assist | Model 448.8 with code JW5 (Lane keeping assist) | PE54.71-S-2057-97VDA | |
| Model 447.8 with code JW5 (Lane keeping assist) except code XM0 (Facelift) | PE54.71-S-2057-97TRA | ||
| Model 447.8 with code JW5 (Lane keeping assist) except code XM0 (Facelift) | PE54.71-S-2057-97TRB | ||
| Overview of system components for driver assistance systems | Model 447.6/7/8 with code JW5 (Lane Keeping Assist) Model 448.8 with code JW5 (Lane Keeping Assist) | GF54.00-S-9998TRA |