Track Guidance, Basic Function - GF54.71-S-9900A

Model All (Light transporter) 

Overview 

This document contains information on:

• General 
• Function requirements 
• Function 
  • Function sequence for switching 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 

General 

The track guidance function evaluates the course of the road in front of the vehicle using the multifunction camera (lane recognition).

The multifunction camera calculates the lane based on two lane algorithms. If comparison of these lane algorithms results in a match, the multifunction camera generates a safe lane. The multifunction camera uses this data to calculate the relative position of the vehicle in the lane.

If the track guidance function detects that the vehicle has left the lane, it warns the driver with noticeable vibrations at the steering wheel generated by the steering system. The system also evaluates the driving behavior of the driver and decides the point at which a warning is to be issued.

In addition, the track guidance function can guide the vehicle back into the lane by means of targeted course-correction steering interventions by the brake system. The track guidance function can be switched on and off manually.

Function requirements 

• Engine running or drivetrain operational.

Leaving lane with warning, schematic diagram 

Courtesy of MERCEDES-BENZ USA

Function 

Warnings are issued as soon as the vehicle is in the direct vicinity of a broken or solid line or crosses over it.

If the crossing of lane markings is detected by a camera, corrective steering intervention takes place to return the vehicle to the lane. If there is no driver response, a haptic warning is also issued in the form of pulsed vibrations at the steering wheel.

The Lane Keeping Assist consists of the following subfunctions:

• Function sequence for switching 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 

Courtesy of MERCEDES-BENZ USA

Function sequence for switching Lane Keeping Assist on and off 

Lane Keeping Assist can be switched on and off via the multimedia system.

The message "Lane Keeping Assist ON/OFF" is shown.

In addition an option is available to the driver to configure the Lane Keeping Assist sensitivity in the multimedia system'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)

Lane Keeping Assist operation is speed-dependent. The vehicle speed is calculated on the basis of the wheel speeds.

Additional function requirements for lane recognition

• Recognizable lane markings present on both sides (no construction site markings (ambiguous markings) no snow not covered up, etc., i.e. insufficient degree of contrast).
• Forward travel recognized and drive range "D" selected
• 2 lane dividers present

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

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. The multifunction camera records pictures of the lane at a fixed scanning rate.

Schematic of lane recognition by multifunction camera 

Courtesy of MERCEDES-BENZ USA

Schematic of lane recognition by multifunction camera 

Courtesy of MERCEDES-BENZ USA

The multifunction camera calculates each lane on the basis of the recorded picture sequences and the measurement values resulting from the lane markings. 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 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.

In the event of multiple markings on the roadway, the inner marking is always taken as the reference point. If there are several markings present (e.g. in construction site zones), 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
• Braking
• Accelerating
• Cutting a tight corner
• Turn signaling
• Sporty driving, at high cornering speeds or with high acceleration

If the multifunction camera detects lateral acceleration > 4 m/s² a pending warning is suppressed here too

Function sequence for recognition of control interventions 

Control elements 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. The warning threshold is adjusted to match the control element 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.

Depending on the equipment, the following control elements are monitored:

• Audio system control elements
• Left multifunction steering wheel button group and right multifunction steering wheel button group
• Driver door operating unit (only the outside mirror adjustment is monitored)
• Interior lamp automatic function button and left front reading lamp button

Additional function requirements for warning output

• Lane recognition by the multifunction camera
• Vehicle speed 60 to 200 km/h
• Curve radius > 150 m
• Exiting of lane detected (recorded by multifunction camera)

Function sequence for issuing warning 

The warning is issued haptically through pulsed vibrations at the steering wheel.

The warning is suppressed when the triggering conditions are no longer present or when driver activity is detected (braking, accelerating, steering or turn signaling).

In "Standard" mode, a haptic warning is suppressed if the following prerequisites are met:

• Turn signaling recognized (the warnings are suppressed for a certain period of time)
• Intervention of a driving safety system detected (e.g. by ESP® or Blind Spot Assist (depending on equipment))

In "Adaptive" mode, a haptic warning is suppressed if the following prerequisites are met:

• Turn signaling recognized (the warnings are suppressed for a certain time period)
• Intervention of a driving safety system detected (e.g. by ESP® or Blind Spot Assist (depending on equipment))
• Heavy acceleration
• Strong braking
• Rapid steering movements (e.g. during an evasive maneuver or during a rapid lane change)
• Corner cutting

Following suppression (driver activity, triggering condition not present), a new warning can be output 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 multifunction camera recognizes a road with bends and concludes "corner cutting". Warnings about corner cutting are not issued until a defined lateral acceleration has been reached.

If "corner cutting" is detected the warning is delayed until a defined threshold (lateral acceleration depending on ground speed) is reached Afterward, a warning is output.

On vehicles with Blind Spot Assist, in the event of a track-aligning steering intervention, the track guidance function takes the oncoming/parallel traffic in the adjacent lane into consideration and guides the vehicle back onto a collision-free course.

On vehicles with Active Steering Assist, lateral guidance with small steering torques takes place continuously in the vehicle speed range from 0 to 210 km/h based on the lane making detected by the multifunction camera.

When driving straight ahead, lateral guidance is also supported if the lane marking is on one side. In this case, even if there are briefly no lane markings, the vehicle in front is followed up to a speed of 130 km/h.

	Function schematics
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		Model 447 with code XM7 (MOPF II)	PE54.71-S-2501-97A
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