Traffic Sign Assist, function - GF54.30-P-0010CAM

MODEL 207.3/4 as of model year 2014 with CODE 513 (Road sign recognition system) 

Function requirements, general 

• Circuit 15R ON

The electronic ignition lock control unit sends the status of circuit 15 to the stereo multifunction camera via chassis CAN 1, the chassis gateway control unit and chassis FlexRay or to the multifunction camera via chassis CAN 1, the front SAM control unit and chassis CAN 2.

Traffic Sign Assist, general 

Depending on the equipment installed, the Traffic Sign Assist is implemented in the multifunction camera or the stereo multifunction camera.

The following traffic signs are detected and evaluated by the respective multifunction camera on the stretch of road being driven on by the vehicle:

• Speed limits including additional signs along with the corresponding termination signs
• No overtaking signs and their termination
• No entry signs

The detected traffic signs are shown in the multifunction display of the instrument cluster and also in the Audio/COMAND display. The display in the multifunction display of the instrument cluster can be switched on or off using the "Assistance" menu of the instrument cluster.

A maximum of two speed limits and an additional traffic sign are shown at the same time. If several speed limits are detected, the speed limit with the lowest limit is displayed.

Display in instrument cluster (depiction of the detected traffic sign is country-specific) 

Display in Audio/COMAND display, system language German (depiction of the detected traffic sign is country-specific) 

The display in the Audio/COMAND display is only shown in the Navigation system map view, and it can be switched on or off using the menu in the COMAND controller unit.

The multifunction camera evaluates the following input factors:

• Signal "Engine running" or "Drivetrain operational"
• Navigation data
• Direction of travel, vehicle speed and yaw rate
• Steering wheel angle
• Wiper signal
• Ambient temperature
• Trailer recognition (with code (550) Trailer hitch)

"Engine running" or "Drivetrain operational" signal:

The CDI control unit or the ME-SFI control unit sends the "Engine running" or "Drivetrain operational" signal to the stereo multifunction camera via chassis CAN 1, the chassis gateway control unit and chassis FlexRay or to the multifunction camera via chassis CAN 1, the front SAM control unit and chassis CAN 2.

Navigation data:

The navigation data is sent by the COMAND controller unit to the stereo multifunction camera via the interior CAN, front SAM control unit, chassis CAN 1, the chassis gateway control unit and chassis FlexRay or to the multifunction camera via the interior CAN, front SAM control unit and chassis CAN 2.

Direction of travel, vehicle speed and yaw rate:

Information on direction of travel and vehicle speed are derived from the wheel speed and wheel rotation direction signals. The RPM sensors are read in directly by the Electronic Stability Program control unit. The yaw behavior is registered by the yaw rate sensor for lateral and longitudinal acceleration. The yaw rate sensor for lateral and longitudinal acceleration sends the corresponding values to the Electronic Stability Program control unit via the vehicle dynamics CAN. The Electronic Stability Program control unit sends all relevant information to the stereo multifunction camera via chassis CAN 1, the chassis gateway control unit and chassis FlexRay or to the multifunction camera via chassis CAN 1, the front SAM control unit and chassis CAN 2.

Steering wheel angle:

The steering wheel angle is recorded by the steering wheel sensor. The steering column tube module control unit reads in the signals from the steering angle sensor directly and sends the information about the steering angle to the stereo multifunction camera via chassis CAN 1, the chassis gateway control unit and chassis FlexRay or to the multifunction camera via chassis CAN 1, the front SAM control unit and chassis CAN 2.

Wiper signal:

The front SAM control unit actuates the wiper system. With the wiper switched on, the front SAM control unit sends the "Wiper active" status to the stereo multifunction camera via chassis CAN 1, the chassis gateway control unit and chassis FlexRay or to the multifunction camera via chassis CAN 2.

Outside temperature:

The outside temperature is defined on the basis of the resistance value of the outside temperature sensor. The front SAM control unit reads in the signal from the outside temperature sensor directly, uses it to calculate the outside temperature and sends the outside temperature to the instrument cluster via chassis CAN 2. In order to determine the correct value for the outside temperature, the instrument cluster additionally takes into account other parameters such as vehicle speed or heat radiating from the combustion engine. The instrument cluster sends the displayed outside air temperature to the stereo multifunction camera via chassis CAN 2, the chassis gateway control unit and chassis FlexRay or to the multifunction camera via chassis CAN 2.

A detailed description of this function can be found in the separate description "Instrument cluster (IC), function".

Trailer recognition (with code (550) Trailer hitch):

If a trailer is detected, the trailer recognition control unit sends the "Trailer detected" status to the stereo multifunction camera via the interior CAN, front SAM control unit, chassis CAN 1, the chassis gateway control unit and chassis FlexRay or to the multifunction camera via the interior CAN, front SAM control unit and chassis CAN 2.

The multifunction camera issues the following initial parameters: 

• Display of traffic sign
• System messages

The multifunction camera sends corresponding requests to display the currently detected traffic sign or a system message to the instrument cluster via chassis CAN 2 and to the COMAND controller unit via chassis CAN 2, the front SAM control unit and interior CAN.

The multifunction camera sends corresponding requests to display the currently detected traffic sign or a system message to the instrument cluster via the chassis FlexRay, chassis gateway control unit, chassis CAN 2 and to the COMAND controller unit via the chassis FlexRay, chassis gateway control unit, chassis CAN 1, the front SAM control unit and interior CAN.

The COMAND controller unit actuates the Audio/COMAND display via the telematics CAN and transmits the corresponding video signals via the LVDS line.

Function sequence for Traffic Sign Assist 

At a horizontal angular coverage of ∠= 46° the multifunction camera records pictures during the journey of the traffic signs over or at the side of the road. Traffic Sign Assist is continuously active in the background. In other words, the corresponding traffic signs are permanently recorded and evaluated by the multifunction camera [MFK]. The recorded picture data are sent to the integrated picture recognition module which compares them against the stored data records and assigns the traffic signs to the respective valid road traffic regulations. The multifunction camera's picture recognition module assigns credibility to all results.

The national regulations for the design and attachment of traffic signs are taken into account for this.

The multifunction camera records all picture objects and evaluates circular as well as square contours. Speed limits, prohibitory and derestriction signs including additional restrictions in countries with signage according to the Vienna convention are accordingly recorded. Non-relevant signs (supplementary signs that, e.g. are relevant for a turnoff lane) are suppressed. If the navigation system is active, supplementary signs will be shown immediately if they are relevant for the currently active navigation.

Possible additional signs include limits in wet conditions or when towing a trailer. If, for example, the wiper signal is received by the multifunction camera and a speed limit with additional restriction "in the wet" is detected, the detected speed limit is shown in the multifunction display of the instrument cluster. The speed limit is not viewed to be relevant as long as a wiper signal is not read in.

Supplementary signs not relevant for passenger cars (e.g. speed limits for trucks) will not be shown. The number of these traffic signs amounts to approx. 10% of all traffic signs. After the data has been evaluated, the detected traffic signs are shown in the multifunction display of the instrument cluster and in the Audio/COMAND display. As a result, information on the currently valid prohibitions or the currently permissible speed is available to the driver.

The multifunction camera also combines the information about speed limit to form an event if the information is contradictory.

If the multifunction camera detects a no entry sign in the entrance to a freeway or expressway in the opposite direction to the direction of travel (scenario whereby the motorist is driving the wrong way along the freeway/expressway), the no entry sign is shown in the multifunction display of the instrument cluster and in the Audio/COMAND display. A "Check direction of travel!" warning message is also shown in the multifunction display and an acoustic warning is issued by the instrument cluster warning buzzer, which is actuated directly by the instrument cluster.

The acoustic warning message can be acknowledged after t = 5 s at the earliest.

In the event of a fault, the following messages are shown in the multifunction display:

• "System currently not available" (e.g. camera field of view fogged up)
• "System nonfunctional" (e.g. multifunction camera or navigation system malfunction)

Traffic signs recognized by the multifunction camera (example displays) 

Visual output of derestriction sign 

The following events cause the derestriction sign to be displayed (picture F):

• Passing by a derestriction sign (picture F)
• Passing by a derestriction sign with a speed value (picture G), if previously no traffic sign with a speed value has been recognized

The following event leads to the display of a derestriction sign (picture H):

• Passing a derestriction sign with speed value (picture G) which deviates from the speed value of the traffic sign recorded in prior history (picture H1)

The following event leads to the display of a derestriction sign (picture I):

• Driving by a derestriction sign for no passing (picture I), if the no passing sign was previously detected (picture I1)

When driving by a derestriction sign (speed limitation or no passing) the derestriction sign is shown for five seconds. After this the valid traffic sign is then shown in the instrument cluster.

In addition the multifunction camera evaluates information on the area around the vehicle and on the vehicle's own movement.

These include:

• Distance and angle to other road users and objects recorded by the multifunction camera itself
• Vehicle movement and yaw behavior
• Navigation data from COMAND controller unit

The attributes verified in the digital card of the navigation system are also evaluated.

The navigation data serve the plausibility check of objects recorded by the multifunction camera as well as the fading out of speed limits displayed when driving into built-up areas.

The navigation data are also used to evaluate the national availability. The national availability may be able to be extended and therefore it matches the current software release. If the navigation data are not available (e.g. no GPS signals), the Traffic Sign Assist is switched off after traveling a distance of s = 30 km.

If the multifunction camera does not detect any speed limits (e.g. because of soiled windshield), the verified values in the navigation system's digital map are then shown. If this condition is maintained for t > 10 minutes, the multifunction camera changes to "Blockade" mode and the display of traffic signs is disabled. If, later on, a traffic sign is detected again (e.g. owing to a reduction in the degree of windshield fogging), the "Blockade" mode is deactivated again.

Because speed limits are subject to alteration, the digital map data has to be regularly updated.

Information on the classification of roads and regional development are deduced from the navigation data provided by COMAND controller unit. By this means the system recognizes that the vehicle is leaving a road for which a speed limit identified earlier was displayed. Since the picture recognition system is unable to cancel the display of a speed limit identified outside a town/village when passing a town/village entry sign, use is made of the navigation data.

With a change from a non-built-up area to a built-up area as defined by the markings for buildings on the navigation map, the display of the last identified speed limit is canceled. As the town/village limits do not always match the built-up area markings on the navigation map, the result of this is that possibly the display of the last detected speed limit is either masked out too soon or continues to remain displayed in the built-up area.

Situations which lead to a failed cancellation or superfluous cancellation of this display are shown in the pictures which follow.

Visual output of derestriction sign 

Function information and system limits 

Below is a list of example situations in which the pictures recorded by the multifunction camera cannot be evaluated and cannot be used for display in the instrument cluster and the Audio/COMAND display.

Speed limits marked by town/village entry and town/village exit signs or by freeway start and finish signs are not recorded. These traffic signs however, are filed through the road definition feature (e.g. freeway) in the digital navigation map.

Electronically actuated changing traffic signs can be "missed" or interpreted incorrectly. In the event of changing traffic signs that are actuated by pulses or flashes, there may be difference to the picture recording's permanent cycle time, depending on the actuated frequency of the changing traffic signs. As a result only fragments of the changing traffic signs will be recognized. If the picture cannot be fully recognized as a traffic sign it is not shown on the display.

It may not be possible to detect changing traffic signs on which the outer circle is missing.

The horizontal angle of vision of the multifunction camera is limited. Traffic signs erected immediately after junctions, turnoffs which the vehicle takes, can be "missed" by the multifunction camera. The horizontal detection angle of the multifunction camera is ∠ a = 45°.

The vertical angle of vision of the multifunction camera is limited. Traffic signs on sign gantries are only interpreted reliably up to a vehicle speed of v = 160 km/h. In order to keep recognition certainty homogeneous over all vehicle speed ranges, the evaluation window of the multifunction camera is downsized as the vehicle speed increases. The consequence of limiting the evaluation window of the multifunction camera is that traffic signs installed low down, as used in construction sites, are "missed" if they are passed at high speed.

The resolution of the multifunction camera is limited. Traffic signs on wide or multilane roads can be "missed" as they do not reach the size required for clear identification in the evaluation window of the multifunction camera.

The sensitivity and dynamics of the multifunction camera are limited. This results in traffic signs not being recognized under the following conditions:

• Traffic signs with low contrast
• Extreme oncoming lights or lights from the rear
• Low levels of lighting, darkness

The focus and alignment of the multifunction camera are fixed. As a result recorded objects are represented with a movement blur depending on the exposure time. This movement blur and sensitivity of the multifunction camera limit its usefulness at night. The result of the fixed focus and static alignment is that the traffic signs to be recorded must be completely visible in a small observation time window.

Unfavorably designed back-end sections of commercial vehicles may be interpreted as derestriction signs by mistake.

Signage on the back-end section of commercial vehicles may be interpreted as traffic signs by mistake.

	Electrical function schematic, traffic sign assist		PE54.30-P-2066-97EAA
	Overview of system components for driver assistance systems		GF54.00-P-9998CAM