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

MODEL 218 as of model year 2015 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 

A camera on the inside of the windshield detects the signposted speed limits, e.g. at the edge of the road, on overhead signs or at construction sites. Their data is compared with the information of the navigation system and displayed both in the instrument cluster and in the navigation map view. "No passing" zones and the associated derestriction signs are also recorded and displayed. In the case of restricted access with corresponding signage, a visual and acoustic warning is additionally output in the instrument cluster.

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 recorded and evaluated 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.

If the display is switched on in the multifunction display, the view is not shown in the Audio/COMAND display.

Shown in multifunction display (country-specific) 

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

Shown in Audio/COMAND display, system language German (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.

If the display is switched on in the Audio/COMAND display, the view is not shown in the multifunction display of the instrument cluster.

The multifunction camera or the stereo multifunction camera evaluates the following input factors: 

• Signal "Engine running" or "Drive train operational"
• Data from navigation system
• Direction of travel, vehicle speed and yaw rate
• Steering wheel angle
• Windshield wiper active
• Outside temperature
• Trailer recognition (with code (550) Trailer hitch)

"Engine running" or "Drive train operational" signal:

The CDI control unit or the ME-SFI control unit sends the "Engine running" or "Drive train 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.

Data from navigation system:

The data from the navigation system is used for the plausibility check on objects captured by the multifunction camera as well as for fading out speed limits displayed when driving into built-up areas. The data from the navigation system 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 yaw behavior is registered by the yaw rate sensor for lateral and longitudinal acceleration. The yaw rate sensor for lateral and longitudinal acceleration transmits appropriate values via the dynamics CAN to the Electronic Stability Program control unit.

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 angle is recorded by the steering wheel angle sensor. The steering column tube module control unit reads in the signals from the steering wheel angle sensor directly and sends the information about the steering wheel 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.

Windshield wiper active:

The front SAM control unit controls the windshield wiper system. With the windshield wiper switched on, the front SAM control unit sends the "Windshield 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 recorded by 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. The instrument cluster calculates the displayed outside air temperature and sends it 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.

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.

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 "Windshield wiper active" status 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 instrument cluster. The speed limit is not regarded as relevant as long as the "Windshield wiper active" status 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. Information about the currently permissible speed or the currently valid prohibitions is thus 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 if the vehicle is driven onto a freeway or expressway in the opposite direction to the direction of travel (wrong-way driver scenario), 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 warning buzzer, which is actuated directly by the instrument cluster.

The multifunction camera sends corresponding requests to display the currently detected traffic sign or a warning 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 stereo multifunction camera sends corresponding requests to display the currently detected traffic sign and a warning 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 telematics CAN and transmits the corresponding data via the LVDS line.

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) 

Representation of derestriction signs 

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 events cause the derestriction sign to be displayed (picture G):

• Passing by a derestriction sign with a speed value (picture G)
• Passing by a derestriction sign restricted by a supplementary sign (picture G1) with speed value

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 past a derestriction sign (speed limitation or no passing), the derestriction sign is shown for t = 5 s. 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:

• Distances and angles to other road users and objects which are detected by the multifunction camera itself
• Vehicle movement and yaw behavior
• Data from the navigation system of the head unit

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

The data from the navigation system is used for the plausibility check on objects captured by the multifunction camera as well as for fading out speed limits displayed when driving into built-up areas.

The data from the navigation system is 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 data from the navigation system cannot be evaluated (e.g. no GPS signals), the Traffic Sign Assist is switched off after a travel distance of s = 30 km.

If the multifunction camera does not detect any speed limits (e.g. if the windshield is dirty), the values verified in the digital map of the navigation system are shown. If this condition is maintained for t > 10 minutes, the multifunction camera changes to the "Blockade" mode and the traffic signs display is deactivated. 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 about the classification of roads and regional development is derived from the navigation system data provided by the 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 data from the navigation system. 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 from the navigation map, the display showing the last detected speed limit may disappear too soon or may continue to be shown in the built-up area.

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

Representation of town/village limits and built-up area limits 

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 uniquely identified as a traffic sign, the speed value that is filed in the digital navigation map is then shown.

To enable the detection of changing traffic signs on which the outer circular ring is missing, special detectors have been implemented in the multifunction camera. This type of display is mainly used in the United Kingdom, the Netherlands and Belgium.

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 angular coverage of the multifunction camera is ∠ a = 46°.

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 (left picture). Signage on the back-end section of commercial vehicles may be interpreted as traffic signs by mistake (right picture).

Navigation system data are not available during an update or reset procedure for the COMAND controller unit, which may lead to fault messages occurring in some cases.

Electrical function schematic, traffic sign assist	MODEL 218 as of model year 2015 with CODE 513 (Road sign recognition system) without CODE 23P (Driving Assistance package Plus)	PE54.30-P-2066-97XAA
	MODEL 218 as of model year 2015 with CODE 23P (Driving Assistance package Plus) with CODE 513 (Road sign recognition system)	PE54.30-P-2066-97XAB
Overview of system components for driver assistance systems		GF54.00-P-9998FQM