GF54.30-P-0012CA Speed Limit Assist, Function
GF54.30-P-0012CA 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 the ME-SFI control unit (N3/10) (with gasoline engine) transmits the status of terminal 61 ON via the chassis CAN (CAN E) to the MFK [multifunction camera] (A40/11).
Speed Limit Assist, general
The following traffic signs are recorded and evaluated on the stretch of road being driven on by the vehicle. :
- Speed limits
- Speed limits, restricted by additional signs (model 207.3 as of 1.6.10 and model 207.4)
- Derestriction signs (model 207.3 as of 1.6.10 and model 207.4)
In addition the attributes verified in the digital card of the navigation system are evaluated.
The corresponding traffic signs are shown in the multifunction display (A1p13) and Audio/COMAND display (A40/8).
As a result information on the current permissible speed is available to the driver.
The function Speed Limit Assist is permanently active in the background.
In other words, the corresponding traffic signs are permanently recorded and evaluated by the MFK [multifunction camera]. The way in which traffic symbols are displayed depends on the setting of the "Speed limit" menu of the IC A1
The function Speed Limit Assist is currently available for the following countries:
- Andorra (AD)
- Belgium (BE)
- Denmark (DK)
- Germany (DE)
- Great Britain (GB)
- Gibraltar (GI)
- France (FR)
- Italy (IT)
- Ireland (IE)
- Luxembourg (LU)
- Liechtenstein (LI)
- Monaco (MC)
- Netherlands (NL)
- Austria (AT)
- San Marino (SM)
- Switzerland (CH)
- Spain (ES)
In which of the countries listed the vehicle is located is defined by way of Global Positioning System (GPS) signal 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 transmitted via the body CAN (CAN B) to the front SAM control unit with fuse and relay module (N10/1) which passes on the navigation data via the chassis CAN to the multifunction camera (MFK).
In the event of failure of the radio with Auto Pilot System or the COMAND controller unit the Speed Limit Assist function is not available. Only in the event of a temporary failure is the Speed Limit Assist function maintained for a distance s = 30 km.
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
While driving the MFK records at a horizontal recording angle of Angular = 34° pictures of the traffic signs mounted above or next to the road.
The pictures recorded are transferred to the integrated picture recognition module which compares these with the stored data records and thus assigns the traffic signs to the respective 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
- The vehicle's own movement and yaw behavior of the vehicle via chassis CAN, provided by the Electronic Stability Program control unit (N30/4) (without code (233) DISTRONIC PLUS) or by the Electronic Stability Program Premium (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 the objects recorded by the MFK as well as masking out of speed limits displayed when driving into built-up areas.
If the camera does not detect any speed limits, the values verified in the digital card of the navigation system are displayed. An activation of the navigation function is not required for this ("sleep-mode" of navigation system).
As speed limits are subject to possible changes, regular updating of the digital card material is necessary.
Generally valid speed limits in built-up areas, on expressways and freeways are not displayed.
After evaluating the data the MFK transmits a corresponding request to control the display of the currently recognized traffic sign via chassis CAN to the IC and the front SAM control unit. The front SAM control unit passes on the request via the interior 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 uses the Telematics CAN (CAN A) and a Low Voltage Differential Signal (LVDS) line to actuate the Audio-/COMAND display to display 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 also combines this information into a result when the individual information on the speed limit contradicts.
Component Identification:
The MFK records all picture objects and evaluates circular as well as square contours.
Speed limits and derestriction symbols including additional restrictions in countries with signage according to the Vienna convention are accordingly recorded.
Signs which are not relevant (additional signs which for example are valid for a turning off lane) are suppressed.
With active navigation the additional sign is nevertheless displayed immediately, if it is of relevance to active navigation.
Additional signs which are not relevant for cars (e.g.speed limits for trucks) are not displayed. The number of these traffic signs amounts to approx. 10% of all traffic signs.
In the following, situations are listed as an example in which the pictures recorded by the MFK are not usable and cannot be used for the 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. However these traffic signs are stored via the road definition (e.g. freeway) in the digital navigation map.
Electronically actuated changing traffic signs can be "missed" or interpreted incorrectly. With alternating traffic signs which are actuated to pulse or flash, then depending on the actuated frequency of the alternating traffic sign there will be a potential difference from the fixed cycle time of the image which leads to only fragments of the alternating traffic sign being detected. If the picture cannot clearly be identified as a traffic sign, it is not displayed.
Alternating traffic signs, on which the outer annulus is missing, are likewise not recorded.
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°.
Component Identification:
The vertical angle of vision of the multifunction camera is limited.
Traffic signs on sign bridges are only interpreted reliably up to a vehicle speed von 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 fixed focus and the static alignment result in the traffic sign 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.
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 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 graphic display of the Speed Limit Assist takes place via the multifunction display and in addition via the Audio/COMAND display.
The control and display concept is divided up into the following subfunctions:
^ Operating concept
^ Display concept
Operating concept
Operation takes place via the "Speed limit" menu level of the IC via the following controls:
- Left multifunction steering wheel button group (S110)
- Scroll back and forward button (S110s1)
- System selection button (S110s3)
- OK button (S110s6)
The control signals of the multifunction steering wheel button group are transmitted by the steering wheel electronics (N135) via the steering LIN (LIN E1) to the steering column tube module control unit (N80).
The steering column tube module control unit transmits the control signals via the chassis CAN to the IC.
The function Speed Limit Assist is selected in the menu of the IC in the following manner:
- Selection of "Assist" main menu
- Selection of "Speed Limit" submenu
- Activate and deactivate selection possibility between information mode
Display concept
The display concept in the multifunction display distinguishes between the following variants:
^ Information mode
^ Permanent display
^ Error messages
Information mode
In information mode the recognized traffic sign can be displayed on any menu of the IC for the duration of t = 5 s and can be acknowledged within this period via the OK button.
The information mode can be switched on and off via the "Speed limit" [speed limit] submenu in the "Assist" menu.
The status is displayed by the fading in of the appropriate pictogram.
Permanent display
When selecting the "Speed limit" submenu in the "Assist" menu in the IC the recognized traffic sign is displayed until this submenu is exited again.
When the information mode is switched off no permanent display of recognized road signs takes place.
The display in the Audio/COMAND display takes place independent of the selected display in the multifunction display. In the navigation menu "Speed limit information" of the radio with Auto-Pilot-System or the COMAND controller unit, the display can be activated or deactivated in the map view.
The following events cause the change in or cancelation of the display:
- 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 in type of road (turning off process)
Afterwards, provided available, a limit of the digital road map of the NAV is displayed.
Error messages
In the event of a failure of the system the cause takes place corresponding to the message "System not currently available" (e.g. fogging of MFK) or "System nonfunctional" (e.g. failure of MFK or NAV) in multifunction display.
In countries in which the function Speed Limit Assist is basically not available the following message is issued: "Speed limit assist not available in this country".
Visual output of derestriction sign
The following events lead to the display of the derestriction sign (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 lead to the display of the derestriction sign (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).
