Traffic Sign Assist, function

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Function requirements in general

 No undervoltage or overvoltage

 Terminal 15R On:

The electronic ignition lock (EZS) control unit transmits the status of terminal 15 via the peripherals CAN to the multifunction camera.

Traffic Sign Assist, general

The multifunction camera mounted to the inside of the windshield detects the speed limits posted, for example at the edge of the road, on sign gantries or in 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. For no-entry zones with corresponding signage, a visual warning and warning tone are also issued in the instrument cluster.

A visual and acoustic warning can also be issued when a speed limit is exceeded, and can be selected and configured using the head unit. The following options are available for navigating in the control menu:

 Navigation can be performed using the head unit control panel control unit. The corresponding control signals are sent via the telematics CAN to the head unit.

 Navigation can be performed by voice control. The driver hands-free system microphone (B25/20) s read in directly by the head unit.

 Navigation can be performed via the head unit finger navigation pad and the "Back" button in the head unit multifunction steering wheel button group. The corresponding control signals are sent via the steering wheel electronics, the steering wheel CAN, the steering column tube module control unit, the suspension FlexRay, the EZS control unit and the user interface CAN to the head unit.

The head unit sends the status of the operating mode via the user interface CAN, the EZS control unit and the peripherals CAN to the multifunction camera.

The driver can select the following operating modes:

 "Visual warning"

 "Visual warning and warning tone"

 "Off"

Traffic Sign Assist is implemented in the multifunction camera depending on the equipment installed.

The following traffic signs are recorded and evaluated on the stretch of road being driven on by the vehicle. :

 Speed limits including additional signs

 No overtaking signs and their termination

 No entry signs

The registered traffic signs are shown on the multifunction display of the instrument cluster and on the Audio/COMAND display. The display in the instrument cluster can switched on or off on the head unit.

 Only one traffic sign is shown in the multifunction display, as well as, if necessary, one supplementary sign (e.g. "wet weather restriction").

 During an update or a reset procedure for the head unit, the navigation system data are not available so that fault messages may occur in an individual case.

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

 The display of the detected traffic signs is country-specific.

Input factors for multifunction camera

The multifunction camera evaluates among others the following input factors:

 "Engine running" or "Drivetrain operational" signal.

 Map data

 Direction of travel, vehicle speed and yaw rate

 Steering wheel angle

 Windshield wiper active

 Outside temperature

 Trailer recognition

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

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.

Map data:

The GPS data (the data from the global navigation system) are 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 GPS data are sent by the head unit via the user interface CAN, the EZS control unit and the peripherals CAN to the multifunction camera.

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 yawing-moment interface is integrated in the ESP® control unit. The ESP® control unit sends all the relevant information via the suspension FlexRay, the EZS control unit and the peripherals CAN to the multifunction camera.

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 of the steering wheel angle sensor directly and sends information about the steering wheel angle via the suspension FlexRay, the EZS control unit and the peripherals CAN to the multifunction camera.

Windshield wiper active:

The SAM control unit controls the windshield wiper system. When the windshield wiper is switched on, the SAM control unit sends the status "Windshield wiper active" via the interior CAN, the EZS control unit and the peripherals CAN to the multifunction camera.

Outside temperature:

The outside temperature is recorded by the outside temperature sensor. The SAM control unit reads in the signal of the outside temperature sensor directly, uses it to calculate the outside temperature and sends this via the interior CAN, the EZS control unit and the user interface CAN to the instrument cluster. The instrument cluster calculates the displayed outside temperature and sends it via the user interface CAN, the EZS control unit and the peripherals CAN to the multifunction camera.

Trailer recognition:

If a trailer is detected, the trailer recognition control unit (with code E40 (Trailer socket, 7-pin) or with code E43 (Trailer socket,13-pin)) sends the status "Trailer detected" via the interior CAN, the EZS control unit and the peripherals CAN to the multifunction camera.

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, in the USA and Canada are accordingly detected. 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 supplementary signs can be . Restrictions in the wet or for trailer operation. If, for example, the "windshield wipers active" status is received by the multifunction camera and a permissible maximum speed with additional restriction "in the wet" is registered, the detected permissible maximum speed is shown in the instrument cluster. The permissible maximum speed is not viewed to be relevant as long as the "windshield wipers 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 evaluating the data, the detected traffic signs are shown in the multifunction display of the instrument cluster and in the Audio/COMAND display control unit. 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.

The multifunction camera sends corresponding requests to display the currently detected traffic sign and a warning message via the peripherals CAN, the EZS control unit and the user interface CAN to the instrument cluster and the head unit.

The head unit actuates the Audio/COMAND display control unit via the telematics CAN and transmits the relevant data.

If the multifunction camera detects a no-entry sign when entering a freeway or expressway in the opposite direction to the direction of travel (motorist driving the wrong way), the no-entry sign is shown in the multifunction display of the instrument cluster and in the Audio/COMAND display control unit. In addition, the warning message "Check direction of travel!" is displayed in the multifunction display and a warning tone is also output via the 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 instrument cluster:

 "System currently not available" (e.g. camera field of view fogged up)

 "System nonfunctional" (e.g. multifunction camera or navigation system malfunction)

 "Field of view camera blocked, Traffic Sign Assist nonfunctional"

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Representation of derestriction signs

The following event results in the derestriction signs being displayed (picture J):

 Passing by a derestriction sign (picture F) and no further speed limit

 In no passing areas, the prohibition sign is removed from the display when a no passing derestriction signs is passed (picture I).

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.

 Vehicle movement and yaw behavior

 GPS data of head unit

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

 The map data are used to evaluate the national availability. The national availability may be able to be extended and therefore it matches the current software release.

 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 is deduced from the map data provided by the head 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 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 map data.

When changing from an undeveloped area to a built-up area, the speed limit of the map data is used. As the town/village limits do not always match the built-up area markings from the navigation map, the display of the last detected speed limit may be faded out 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:

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Function information and system limits

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

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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.

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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 image cannot be uniquely identified as a traffic sign, the speed value that is stored in the digital navigation map is then shown.

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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 Netherlands and Belgium.

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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°.

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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.

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

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