GF54.71-P-0005CA Lane Keeping Assist Function
GF54.71-P-0005CA Lane Keeping Assist Function
MODEL 207
- with CODE (476) Active Lane Keeping Assist
Function requirements, general
^ Circuit 15 ON
^ Function in instrument cluster (A1) enabled
^ Vehicle speed v = 60 to 250 km/h
^ Recognizable lane markings present on both sides (no construction site markings (yellow/white), no snow, not covered up, i.e. contrast too low)
^ Radius of curve r >150 m
^ Track width s = 2.5 up to 4.6 m
The electronic ignition lock control unit (N73) sends the circuit 15 status over the chassis CAN (CAN E) to the multifunction camera (A40/11).
Lane Keeping Assist, general
The Lane Keeping Assist function detects any unintentional driving across lane markings and issues a haptic warning to the driver in certain circumstances through initiating vibrations on the steering wheel.
Crossing over lane markings is optically recorded and processed by the multifunction camera.
The haptic warning is generated by the steering wheel vibration motor (M99). The Lane Keeping Assist function takes the driver's behavior into consideration and decides the point at which a warning is to be issued.
As from 1.6.12 it will be possible for the driver to select the sensitivity of the Lane Keeping Assist in the instrument cluster's "Assistance" menu.
The following operating modes are available for selection:
- Standard (high sensitivity, warnings issued earlier and more frequently)
- Adaptive (reduced sensitivity, warnings issued later and less often)
Under the following conditions any driving over lane markings is detected, but a warning is not issued:
- Driver activities through evaluation of steering-wheel movement, brake requests and the accelerator pedal position
- Sporty cornering (corner cutting)
- Turn signals
- Active control interventions by braking assistance systems
Illustration of Lane Keeping Assist principle
a The vehicle is in the lane
b Vehicle crosses over outer lane marking because driver distracted. Driver is then warned by means of steering-wheel vibration
c The vehicle is steered by the driver back into the lane
The Lane Keeping Assist function operates on a speed-dependent basis. The vehicle speed is calculated on the basis of the wheel speed signals.
The wheel speeds are recorded by the following sensors:
- Left front axle rpm sensor (L6/1)
- Right front axle rpm sensor (L6/2)
- Left rear axle rpm sensor (L6/3)
- Right rear axle rpm sensor (L6/4)
The Electronic Stability Program control unit (N30/4) directly reads in the signals from the rpm sensors and sends them over the chassis CAN to the instrument cluster. The instrument cluster calculates the vehicle speed to be displayed and sends this over the chassis CAN to the multifunction camera.
The Lane Keeping Assist function consists of the following subfunctions:
^ Function sequence for lane recognition
^ Function sequence for recognition of driver activity
^ Function sequence for recognition of control interventions
^ Function sequence for issuing warning
Function sequence for lane recognition
The multifunction camera, which is mounted at the top center of the windshield, visually records the road space in front of the vehicle. For this purpose, the multifunction camera records pictures of the lane at a fixed scanning rate and makes these pictures available to the integrated control unit. The multifunction camera measures the lane based on the lane markings.
Schematic of lane recognition by multifunction camera
Based on the recorded image sequences and the measurement values resulting from the lane markings, the multifunction camera calculates each lane. This calculation is based on a corresponding algorithm.
On the basis of this data, the multifunction camera determines the relative position of the vehicle in the lane. The actions of the Lane Keeping Assist function are all derived from this. 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.
When in construction site areas, the Lane Keeping Assist function is unable to issue warnings because of possible multiple lane markings.
The multifunction display (A1p13) in the instrument cluster continuously displays the current status of the Lane Keeping Assist function, in particular, the warning readiness. This status information is sent by the multifunction camera over the chassis CAN to the instrument cluster.
Possible displays:
- Function status
- Icon OFF: Lane Keeping Assist deactivated
- Icon yellow (1): Lane Keeping Assist activated, but not ready to issue warnings (e.g. v < 60 km/h)
- Warning readiness
- Icon green (2): Lane Keeping Assist activated and ready to issue warnings
- Message for function errors in multifunction display
Function sequence for recognition of driver activity
The following situations suggest driver activity and result in suppression of any pending warning:
- Turn signals
- Accelerate
- Brakes
- Steering intervention
Deliberate driver activity is recorded as follows:
Turn signaling:
The steering column tube module control unit (N80) directly reads in the switch position of the combination switch (S4) and sends it over the chassis CAN to the multifunction camera.
Acceleration:
The accelerator pedal sensor (B37) registers when the accelerator pedal is operated.
The CDI control unit (N3/9) (for diesel engine) or the ME-SFI [ME] control unit (N3/10) (for gasoline engine) directly reads in the accelerator pedal sensor signals and sends them over chassis CAN to the multifunction camera.
Brakes:
The brake lights switch (S9/1) registers when the brake pedal is operated. The Electronic Stability Program control unit directly reads in the status of the brake lights switch. The Electronic Stability Program control unit also evaluates the data for the vehicle's movement (yawing moment) and sends it along with the status of the brake lights switch over the chassis CAN to the multifunction camera.
The vehicle's yaw behavior is recorded by the yaw rate sensor for lateral and longitudinal acceleration (B24/15), which communicates over the dynamics CAN (CAN H) with the Electronic Stability Program control unit.
Steering intervention:
The steering movements are recorded by the steering angle sensor (N49).
The steering column tube module control unit directly reads in the signals of the steering angle sensor and sends them over the chassis CAN to the multifunction camera.
If the multifunction camera detects active corner cutting by the driver, crossing over the lane marking at an angle of > 3° or a lateral acceleration of a > 4 m/s 2, then a pending warning is also suppressed.
Function sequence for recognition of control interventions
All controls in the driver's immediate vicinity are monitored. If a control intervention is registered, the Lane Keeping Assist function deems the driver to be "distracted". As soon as the vehicle drives over the lane marking, an active warning is output.
Evaluation of control interventions is carried out by the multifunction camera. The warning threshold is adjusted to match the control actuating frequency, i.e. the Lane Keeping Assist function warns earlier and possibly more often.
The following controls are monitored:
- Audio system controls:
- Radio (A2) (with code (510) Audio 20 incl. CD-changer or with code (523) MB Audio 20 radio) or Radio with Auto Pilot System (A2/56) (with code (511) Audio 50 APS incl. DVD changer or with code (525) MB Audio 50 APS radio) or COMAND controller unit (A40/3) (with code (512) COMAND APS incl. DVD changer or code (526) COMAND with single DVD drive (without navigation) or code (527) COMAND APS with single DVD drive (with navigation) or code (528) COMAND incl. DVD changer)
- Comfort function controls:
- Cruise control lever (S40/4)
- Driver-side power window and outside mirror adjustment switch group (S20) (only the outside mirror adjustment is monitored)
- Steering column adjustment switch (S59) (with code (275) Memory package (driver seat, steering column, mirrors))
- Left multifunction steering wheel button group (S110) or right multifunction steering wheel button group (S111)
- Interior illumination controls:
- Front dome lamp switch (N70/3s4)
- Left front reading lamp switch (N70/3s6)
- Right front reading lamp switch (N70/3s7)
Control interventions are recorded as follows:
Control interventions on audio system:
The control interventions on the control buttons of the audio system are sent by the radio or the COMAND controller unit over the interior CAN (CAN B), front SAM control unit with fuse and relay module (N10/1) and the chassis CAN to the multifunction camera.
Control interventions on comfort functions:
Control interventions on the steering column adjustment switch, on the CRUISE CONTROL lever and at the multifunction steering wheel button groups are read in by the steering column tube module control unit, and they are sent over the chassis CAN, electronic ignition lock control unit and front end CAN to the multifunction camera.
The steering wheel electronics (N135) directly read in the control interventions on the multifunction steering wheel button groups and send them over the steering LIN (LIN E1) to the steering column tube module control unit.
Control interventions at the driver-side power window and outside mirror adjustment switch group are read in by the left front door control unit (N69/1) over the left door-LIN (LIN B5) and sends them over the interior CAN, front SAM control unit and the chassis CAN to the multifunction camera.
Interior illumination control interventions:
The status of the front dome lamp switch and the front reading lamp switch in the Electronic overhead control panel (N70/3) are directly read in by the front SAM control unit and they are sent over the chassis CAN to the multifunction camera.
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 sends the request to actuate the steering wheel vibration motor over the chassis CAN to the steering column tube module control unit.
The steering column tube module control unit forwards the request over the steering LIN to the steering wheel electronics which actuate 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 cover for perceptible influences from the suspension at high speeds.
The warning is terminated when the triggering conditions are no longer given or when driver activity is detected (braking, accelerating, steering intervention or turn signaling).
The warning is also terminated if, during a warning, a driver response is detected (e.g. steering back into the lane or turn signaling).
The following situations will result in suppression of a warning output, because it is assumed that the driver activity is intentional:
- Status changes of steering wheel, brake or accelerator pedal
- Recognized "corner cutting" (by means of lane recognition and the current vehicle position the 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.
- Active flashing function (corresponding turn signaling)
- Active or passive safety functions active
For vehicles up to 31.5.12, a warning can only be output again after a warning suppression after approx. t = 3 s or after t = 10 s in the case of turn signaling.
For vehicles as of 1.6.12, the next warning after a suppression 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.
The corresponding information for suppression of the warning is received by the multifunction camera over the chassis CAN. If "corner cutting" is detected, the warning is delayed until a defined threshold (lateral acceleration depending on ground speed) is reached. Only then is the warning issued.
