Traffic Sign Assist, Function - GF54.30-P-0010RDM
Model 172.4 as of model year 2017
with code 513 (Traffic Sign Assist)
Shown on model 172.4
Function requirements, general
- "Engine running" or "Drive train operational" signal on
- Vehicle moving forward
The CDI control unit (with diesel engine) or the ME-SFI control unit (with gasoline engine) sends the "Engine running" or "Drivetrain operational" signal via chassis CAN 1, the front SAM control unit and chassis CAN 2 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. In the case of restricted access with corresponding signage, a visual and acoustic warning is additionally output in the instrument cluster.
The Traffic Sign Assist is implemented in the 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/COMMAND 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.
Display in instrument cluster (depiction of the detected traffic sign is 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.
Display in Audio/COMMAND display, system language German (depiction of the detected traffic sign is country-specific)
The display in the Audio/COMMAND display is only shown in the map view of the navigation system and can be switched on/off via the menu of the radio (with code 505 (20 NTG5 radio without navigation capability) or code 522 (Audio 20 radio)) or of the COMMAND controller unit (with code 531 (COMMAND APS)).
The multifunction camera evaluates the following input factors:
- Signal "Engine running" or "Drive train operational"
- Map data
- Direction of travel, vehicle speed and yaw rate
- Steering wheel angle
- Windshield wiper active
- Outside temperature
"Engine running" or "Drive train operational" signal:
The CDI control unit (with diesel engine) or the ME-SFI control unit (with gasoline engine) sends the "Engine running" or "Drivetrain operational" signal via chassis CAN 1, the front SAM control unit and chassis CAN 2 to the multifunction camera.
Map data:
The map data is used for checking the plausibility of the object detected by the multifunction camera as well as for fading out displayed speed limits when the vehicle is driven into built-up areas. The map data is sent by the radio (with code 505 (20 NTG5 radio without navigation capability) or code 522 (Audio 20 radio)) or by the COMMAND controller unit (with code 531 (COMMAND APS)) via the interior CAN, front SAM control unit and chassis CAN 2 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 yaw rate sensor for lateral and longitudinal acceleration (with code 239 (DISTRONIC PLUS) or model 172.466) supplies information regarding the yaw behavior of the vehicle and sends this information over the vehicle dynamics CAN to the Electronic Stability Program control unit.
The Electronic Stability Program control unit sends all relevant information to the multifunction camera via chassis CAN 1, the front SAM control unit and chassis CAN 2.
Steering wheel angle:
The steering wheel angle sensor detects/records the steering wheel angle. The steering column tube module control unit reads in the signals from the steering wheel angle sensor directly and sends information about the steering wheel angle via chassis CAN 1, the front SAM control unit and chassis CAN 2 to the multifunction camera.
Windshield wiper active:
The front SAM control unit controls the windshield wiper system. With the windshield wipers switched on, the front SAM control unit sends the "windshield wipers active" status via chassis CAN 2 to the multifunction camera.
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 the interior CAN. The instrument cluster calculates the displayed outside temperature and sends it via chassis CAN 2 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 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.
The multifunction camera sends corresponding requests to display the currently detected traffic sign and a warning message via chassis CAN 2 to the instrument cluster and via chassis CAN 2, the front SAM control unit and interior CAN to the radio (with code 505 (20 NTG5 radio without navigation capability) or code 522 (Audio 20 radio)) or the COMMAND controller unit (with code 531 (COMMAND APS)).
The radio (with code 505 (20 NTG5 radio without navigation capability) or code 522 (Audio 20 radio)) or the COMMAND controller unit (with code 531 (COMMAND APS)) actuates the Audio/COMMAND display via the telematics CAN and transmits the corresponding data via the LVDS line.
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/COMMAND 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 acoustic warning message can be acknowledged after t = 5 s at the earliest.
Possible additional signs include limits in wet conditions. 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 the data has been evaluated, the detected traffic signs are shown in the multifunction display of the instrument cluster and in the Audio/COMMAND 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.
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)
Derestriction signs
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
- Vehicle movement and yaw behavior
- Map data of radio (with code 505 (20 NTG5 radio without navigation capability) or code 522 (Audio 20 radio)) or of COMMAND controller unit (with code 531 (COMMAND APS))
The attributes verified in the digital card of the navigation system are also evaluated.
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. The applicable traffic sign is then shown in the multifunction display and in the Audio/COMMAND display.
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, detected by the multifunction camera
The map data is used for checking the plausibility of the object detected by the multifunction camera as well as for fading out displayed speed limits when the vehicle is driven into built-up areas.
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.
If the map data 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 on the classification of roads and regional development is derived from the map data provided by the radio (with code 505 (20 NTG5 radio without navigation capability) or code 522 (Audio 20 radio)) or by the COMMAND controller unit (with code 531 (COMMAND APS)). 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.
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 multifunction display and the Audio/COMMAND display:
Freeway signs
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
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.
Changing traffic signs without circular ring
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.
Horizontal angle of vision of multifunction camera
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°.
Vertical angle of vision of multifunction camera
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, for example signs used in construction sites, are "missed" if they are passed at high speed.
Resolution of multifunction camera
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.
Misinterpretation of back-end sections of commercial vehicles
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).
The data from the navigation system is not available during updating or resetting of the radio (with code 505 (20 NTG5 radio without navigation capability) or code 522 (Audio 20 radio)) or the COMMAND controller unit (with code 531 (COMMAND APS)); this may lead to fault messages occurring in some cases.
| Electrical function schematic, traffic sign assist | PE54.30-P-2066-97TAA | ||
| Overview of system components for driver assistance systems | GF54.00-P-9998RDM |