Active Lane Keeping Assist, Function - GF54.71-D-0004TSA

Model 907 

with code JB4 (Active lane keeping Assist) 

Shown on model 907 

Function requirements, general 

• Engine running or drive train operational:

  The CDI control unit or the ME-SFI control unit sends the signal "Engine running" or "Drivetrain operational" via the powertrain CAN, the powertrain control unit and the peripherals CAN to the multifunction camera.

• No undervoltage or overvoltage
• Soiling and function test of multifunction camera completed: The 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 lane markings is optically recorded and processed by the multifunction camera.

The haptic warning is generated by the electric power steering actuator motor.

If the vehicle unintentionally crosses a solid lane marking and the driver does not respond to the warning, 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 canceled.

If there is active regulation by the ESP®, the Active Distance Assist DISTRONIC electric controller unit or the Active Brake Assist with cross-traffic function controller unit Active Lane Keeping Assist immediately suppresses or cancels the brake application.

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 occur when pulling up to or when crossing a continuous line (lane delimitation) 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.

Active Lane Keeping Assist operation is speed-dependent. The ESP® control unit uses the wheel speeds to calculate the vehicle speed. The ESP® control unit sends this via the suspension FlexRay, the EZS control unit and the peripherals CAN to the multifunction camera.

Schematic view of an intervention by Active Lane Keeping Assist 

The Active Lane Keeping Assist comprises the following subfunctions:

• Function sequence for Active Lane Keeping Assist ON and OFF 
• Function sequence for lane recognition 
• Schematic of lane recognition by multifunction camera 
• Function sequence for recognition of driver activity 
• Detection of driver distraction 
• Warning output 
• Brake system intervention 

Active Lane Keeping Assist is switched off and on in the multimedia system in the "Settings" menu under the menu item "Assistance". The instrument cluster sends the status over the user interface CAN, EZS control unit and the periphery CAN to the multifunction camera. The "Lane Keeping Assist ON/OFF" message is shown in the multifunction display of the instrument cluster.

speed is calculated from the wheel speed. The ESP® control unit sends this via the suspension FlexRay to the EZS control unit and via the peripherals CAN to the multifunction camera.

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 detected

  The direction of travel is defined using the wheel rotation direction.

  The ESP® control unit sends corresponding information via the suspension FlexRay to the EZS control unit and to the multifunction camera.

  The fully integrated transmission control (VGS) electric controller unit in model 907 with code GK8 (9G-TRONIC) sends information about the engaged drive range via the powertrain CAN, the powertrain control unit and the peripherals CAN to the multifunction camera.

Function sequence for lane recognition 

The multifunction camera is mounted at the top center of the windshield and it records the road space in front of the vehicle.

Schematic of lane recognition by multifunction camera 

The multifunction camera calculates the lane based on two different lane algorithms that are implemented in the multifunction camera. If the comparison between the two lane algorithms results in a match, the multifunction camera uses the data to generate a safe lane. The 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. Lane information cannot be issued in the following cases:

• No lane marking
• Lane marking concealed (e.g. through soiling or snow).
• Low contrast between road surface and lane marking
• Strong sunlight 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 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 (MRM) control unit reads in the signals of the steering wheel angle sensor directly and sends information about the steering angle over the suspension FlexRay, EZS control unit and the periphery CAN to the multifunction camera.

Brakes: 

The ESP® control unit sends the status of the brake pedal over the suspension FlexRay, EZS control unit and the periphery CAN to the multifunction camera.

Acceleration: 

The powertrain control unit sends information about the accelerator pedal position via the periphery CAN to the multifunction camera.

Turn signaling: 

The steering column tube module (MRM) control unit reads in the switch position of the combination switch directly and sends it over the suspension FlexRay, EZS control unit and the periphery CAN to the multifunction camera.

Turn rate, lateral acceleration and longitudinal acceleration: The yawing-moment interface is integrated in the Supplemental Restraint System (SRS) control unit. The SRS control unit sends the signals over the vehicle dynamics CAN to the ESP® control unit. This evaluates the data and sends the data over the suspension FlexRay, EZS control unit and the periphery CAN to the multifunction camera.

If the multifunction camera detects intentional corner cutting, crossing over of the lane marking at a large angle or a lateral acceleration, 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 multifunction camera. The warning threshold is adjusted to match the control actuating frequency, i.e. Active Lane Keeping Assist warns earlier and possibly more often. The following controls are monitored:

• Audio system controls
• Comfort function controls:
• Button groups on multifunction steering wheel
• Driver's door switch module (only outside mirror adjustment is monitored)
• Interior illumination controls

Control interventions on comfort functions: 

The steering wheel electronics read in the operation signals of the button groups on the multifunction steering wheel directly and sends them via the steering wheel CAN to the steering column tube module (MRM) control unit. The steering column tube module (MRM) control unit reads in the operation signals directly and sends information about the control interventions over the suspension FlexRay, EZS control unit and the periphery CAN to the multifunction camera.

The driver's door control unit reads in the operation signals of the driver's door switch module over the driver door LIN and sends them over the interior CAN, EZS control unit and the periphery CAN to the multifunction camera.

Interior illumination control interventions: 

The overhead control panel (OCP) control unit sends the status of the interior illumination over the roof LIN, SAM control unit, interior CAN, EZS control unit and the periphery CAN to the multifunction camera.

Additional function requirements for warning output 

• Lane recognition by the multifunction camera
• Vehicle speed 60 to 250 km/h
• Curve radius > 150 m
• Leaving of lane

Warning output 

The 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 electric power steering actuator motor. The multifunction camera sends the request to actuate the electric power steering actuator motor over the periphery CAN, EIS control unit and the suspension FlexRay to the electrical power steering (ES) control unit. This then actuates the electric power steering actuator motor directly.

The electric power steering actuator 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.

The warning is suppressed if the triggering conditions are not present or when driver activity is detected (braking, accelerating, steering interventions 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 ESP®) In "Adaptive" 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 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 a suppression, a new warning can only be issued in "Standard" mode 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 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 multifunction camera via the peripherals 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 to 4.4 m
• Vehicle speed 60 to 200 km/h
• Outer curve radius > 500 m, inner curve radius > 150 m
• ESP® not switched passively
• ESP® not in active diagnostic or roller dynamometer mode
• No active brake intervention detected (e.g. through ABS, ESP®):

  The ESP® control unit sends the status of the brake system via the suspension FlexRay, the EZS control unit and the peripherals CAN to the multifunction camera.

• No trailer operation detected (with code E40 (Trailer socket, 7-pin) or with code E43 (Trailer socket, 13-pin))
• Tire pressure of all wheels within the tolerance range:

  In vehicles with code RY2 (Tire pressure monitor), the tire pressure monitor control unit sends the information about the respective tire pressure via the user interface CAN, the EZS control unit and the peripherals CAN to the multifunction camera.

• Approval issued for active intervention by the brake system for yawing moment interface

  The yawing-moment interface is integrated into the SRS control unit. The SRS control unit sends the signals over the vehicle dynamics CAN to the ESP® control unit. This issues approval for any course-correcting braking torque.

Brake system intervention 

If the vehicle crosses a solid lane marking, the multifunction camera starts the warning sequence. If the driver fails to respond, the multifunction camera calls for brake intervention. To do this, the multifunction camera sends the request for active brake application via the peripherals CAN, the EZS control unit and the suspension FlexRay to the ESP® control unit.

At the same time as the wheel-specific intervention by the brake system, the driver is visually notified of this activity. The multifunction camera sends the corresponding request via the peripherals CAN, the EZS control unit and the user interface CAN to the instrument cluster. 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	PE54.71-D-2053-97TSA
Overview of system components for driver assistance systems	GF54.00-D-9998TSA