GF54.30-P-0012FL Speed Limit Assist, Function
GF54.30-P-0012FL Speed Limit Assist, Function
- with CODE (513) Speed Limit Assist
Function requirements, general
^ Circuit 61 ON
^ Vehicle moving forward
The CDI control unit (N3/9) (with diesel engine) or ME-SFI control unit (N3/10) (with gasoline engine) transmits the "Circuit 61 ON" status to the multifunction camera (A40/11) via the chassis CAN (CAN E).
Speed Limit Assist, general
The following traffic signs are recorded and evaluated by the multifunction camera on the stretch of road covered by the vehicle:
- Speed limits
- Speed limits, restricted through supplementary signs (as of 1.6.10)
- Derestriction signs (as of 1.6.10)
The attributes verified in the navigation system's digital map are also evaluated.
The corresponding traffic signs are shown in the multifunction display (A1p13) and Audio/COMAND display (A40/8).
The driver is then shown information about the current permissible speed limit.
The Speed Limit Assist function is permanently active in the background.
In other words, the corresponding traffic signs are permanently recorded and evaluated by the multifunction camera. The manner in which the traffic signs are shown depends on the setting of the "Speed Limit" menu in the instrument cluster (A1).
The Speed Limit Assist function is currently available for the following countries:
- Andorra
- Belgium
- Denmark
- Germany
- Great Britain
- Gibraltar
- France
- Italy
- Ireland
- Luxembourg
- Liechtenstein
- Monaco
- Netherlands
- Austria
- San Marino
- Switzerland
- Spain
In which of the countries listed the vehicle is located is defined by way of Global Positioning System (GPS) signals
These are read in and evaluated by the radio with Auto Pilot System (A2/56) (with code (511) 50 APS Audio incl. DVD changer or code (525) MB Audio 50 APS radio) or by the COMAND controller unit (A40/3) (with code (512) COMAND APS incl. DVD changer or code (527) COMAND APS with Single DVD drive (with navigation)).
The navigation data are sent over the body CAN (CAN B) to the front SAM control unit with fuse and relay module (N10/1), which forwards the navigation data over the chassis CAN to the multifunction camera.
If the radio malfunctions with the Auto Pilot System or the COMAND controller unit, the Speed Limit Assist function is no longer available. The Speed Limit Assist function is only maintained for a travel distance of s = 30 km in the event of a temporary failure.
Function sequence of Speed Limit Assist
The Speed Limit Assist function consists of the following partial functions:
^ Picture recognition and evaluation function sequence
^ Function sequence for control and display concept
Picture recognition and evaluation function sequence
During a journey, the multifunction camera records - at a horizontal detection angle of Angular = 34° - pictures of the traffic signs mounted above or at the side of the road.
The recorded pictures are transmitted to the integrated picture recognition module which compares these with the stored data records and assigns the traffic signs to the respective valid road traffic regulations.
The 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.
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
- Navigation data of radio with Auto Pilot System or COMAND controller unit
- Natural movement and yaw characteristics of the vehicle prepared via chassis CAN by the Electronic Stability Program control unit (N30/4) (without code (233) DISTRONIC PLUS) or by Electronic Stability Program Premium control unit (N30/7) (with code (233) DISTRONIC PLUS)
Information on the vehicle' own movement is derived from the wheel speeds as an indicator of vehicle speed
The yaw rate sensor for lateral and longitudinal acceleration (B24/15) provides information on the yaw characteristics of the vehicle and transmits these via the vehicle dynamics CAN (CAN H) to the Electronic Stability Program control unit which passes on this information via the chassis CAN to the MFK (multifunction camera).
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.
If the multifunction camera does not detect any speed limits, the verified values in the navigation system's digital map are then shown. It is not necessary to actuate the navigation function (navigation system "sleep-mode").
Because speed limits are subject to alteration, the digital map data has to be regularly updated.
Generally valid speed limits in built-up areas, on expressways and freeways are not displayed.
After evaluating the data the multifunction camera transmits a corresponding request to control the display of the currently recognized traffic sign over the chassis CAN to the instrument cluster and the front SAM control unit. The front SAM control unit forwards the request over the body CAN to the radio with Auto Pilot System or to the COMAND controller unit.
The radio with Auto Pilot System or the COMAND controller unit then actuates the Audio/COMAND display through the telematics CAN (CAN A) and by way of a low voltage differential signal (LVDS) line to show the currently-detected traffic sign.
If a data source (picture recognition, vehicle data or navigation data) fails, the most credible result is deduced from the remaining data together with the stored past history data.
The multifunction camera combines this information into a result when the individual references to a speed limit are contradictory.
Component Identification:
The multifunction camera records all picture objects and evaluates circular as well as cornered contours
Therefore speed limit signs and derestriction signs including supplementary signs are recorded in countries which have signs in accordance with the Vienna Convention.
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.
Supplementary signs not relevant for passenger cars (e.g. speed limits for trucks) will not be shown. These traffic signs account for approx. 10% of all traffic signs.
Situations are listed below as an example, in which the pictures recorded by the multifunction camera cannot be evaluated and cannot be used for display in the multifunction 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. With changing traffic signs that are pulse or flash actuated, there may be a difference in the fixed cycle time for picture recording with regard to the frequency of the changing traffic signs, which in turn leads to only fragments of such changing traffic signs being recognizable If the picture cannot be fully recognized as a traffic sign it is not shown on the display.
Changing traffic signs on which the outer circle is missing are not shown either.
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 recording angle of the multifunction camera is a = Angular 34°.
Evaluation window at vehicle speed v = 144 km/h (b)
Evaluation window at vehicle speed v = 72 km/h (c)
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 the recognition safety homogenous over all speed ranges, the evaluation window is reduced in size as the vehicle speed reduces. 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 is 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.
Recognition is not possible if the traffic sign is concealed by other objects within this observation 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).
Information on the classification of roads and on built-up areas is derived from the radio with Auto-Pilot-System or from the navigation 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 navigation data.
If you switch from a non-built-up area to a built-up area, as defined by the built-up area marking on the navigation map the display of the last speed limit detected is canceled.
Since the town/village borders do not always coincide with the markings for buildings on the navigation map, it may happen that the display of the last identified speed limit is either removed too early or continues to show inside the official town/village area.
Situations resulting in the display not being removed or being removed unnecessarily are shown in the following pictures.
Component Identification:
Function sequence for control and display concept
The Speed Limit Assist is shown graphically on the multifunction display and the Audio/COMAND display.
The control and display concept is split up into the following subfunctions:
^ Operating concept
^ Display concept
Operating concept
Operation is done using the "Speed Limit"menu on the instrument cluster and using the following controls:
- Left multifunction steering wheel button group (S110)
- Scroll forward/back button (S110s1)
- System selection button (S110s3)
- OK button (S110s6)
The control signals of the multifunction steering wheel button group are sent via the steering wheel electronics (N135) through the steering LIN (LIN E1) to the steering column tube module control unit (N80).
The steering column tube module control unit forwards the control signals via the chassis CAN to the instrument cluster.
The Speed Limit Assist function is selected as follows in the instrument cluster:
- "Assist" main menu selection
- "Speed Limit" submenu selection
- Selection option between activate and deactivate information mode
Display concept
The display concept in the multifunction display differentiates between the following variants:
^ Information mode
^ Permanent display
^ Error messages
Information mode
In the information mode a recognized traffic sign can be shown on any menu level on the instrument cluster for a duration of t = 5 s and it can be acknowledged within this period by pressing the OK button.
The information mode can be switched on and off in the "Speed Limit" submenu in the "Assist" menu.
The status is indicated by showing the corresponding pictogram.
Permanent display
If "Speed Assist" in the "Assist" menu on the instrument cluster is selected, the recognized traffic sign is shown until the submenu is exited again.
If the information mode is switched off, recognized traffic signs are not shown permanently either.
The display in the Audio/COMAND display is shown irrespective of the display selected in the multifunction display. In the "Speed Limit Information" navigation menu in the radio with Auto Pilot System or COMAND controller unit, the display in the map view can be activated or deactivated.
The following events induce a display change or cancellation:
- Recognition of a new speed limit
- Recognition of a derestriction sign
- No identification of a new road sign for a certain distance, depending on the type of road.
- Passing recognized local limits
- Change of road type (turnoff procedure)
Following this, a limit of the navigation system's digital road map is shown where available.
Error messages
If the system malfunctions a message is shown to match the cause such as "System currently unavailable" (e.g. fogging of multifunction camera) or "System nonfunctional" (e.g. failure of multifunction camera or the navigation system) in the multifunction display.
In countries in which the Speed Limit Assist function is never available, the following message is issued: "Speed Limit Assist not available in this country".
Visual display of derestriction signs
The following events cause the derestriction sign to be displayed (picture F):
- Passing a derestriction sign (picture F).
- Passing a derestriction sign with speed limit value (picture G), when previously no traffic sign with speed limit value was detected.
The following events cause the derestriction sign to be displayed (picture G):
- Passing a derestriction sign with speed limit value (picture G).
- Passing a limited derestriction sign with supplementary sign (picture G1) with speed limit value.
The following event will cause the derestriction sign to be displayed (picture H):
- Passing a derestriction sign with speed limit value (picture G), which deviates from the speed limit value of the traffic sign as previously documented (picture H1).
