Speed Limit Assist, Function - GF54.30-P-0012FQ
MODEL 218
up to year 2015
with CODE 513 (Speed Limit Assist)
Up to 28.02.2013
As of 01.03.2013
Function requirements, general
- Engine running or drive train operational
- Vehicle moving forward
On vehicles up to 28.02.2013, the CDI control unit or the ME-SFI control unit sends the "Engine running" or "Drivetrain operational" signal to the multifunction camera via the chassis CAN. On vehicles as of 01.03.2013, the CDI control unit or the ME-SFI control unit sends the "Engine running" or "Drivetrain operational" signal to the multifunction camera via chassis CAN 1, the front SAM control unit and chassis CAN 2.
Speed Limit Assist, general
The Speed Limit Assist uses the multifunction camera to detect the speed limits as declared by the traffic signs for the stretch of road covered by the vehicle.
The speed limits are shown as traffic sign symbols on the multifunction display of the instrument cluster and on the Audio/COMMAND display.
The following traffic signs are recorded by the multifunction camera and evaluated:
- Speed limits
- Supplementary sign
- Derestriction signs
The attributes verified in the digital card of the navigation system are also evaluated.
As a result information on the current permissible speed is available to the driver.
The Speed Limit 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 way in which traffic symbols are displayed depends on the settings of the "Speed limit" menu of the "IC Limit" menu in instrument cluster.
The Speed Limit Assist consists of the following subfunctions:
- Picture recognition and evaluation function sequence
- Function sequence for control and display concept
Picture recognition and evaluation function sequence
With a horizontal detection angle of ∠ = 45°, the multifunction camera captures images of the traffic signs above or at the side of the roadway while the vehicle is in motion. The image data is transmitted to the integrated image recognition module, which compares them 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
- Map data from the radio with Auto Pilot System or from the COMMAND controller unit
- Vehicle movement and yaw behavior, sent by the Electronic Stability Program control unit
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. 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 activate navigation mode (navigation system "sleep-mode").
The map data is additionally used to evaluate the national availability. The national availability may be able to be extended and therefore it matches the current software release. If no map data is available (e.g. no GPS signals), the Speed Limit Assist is switched off after a travel distance of s = 30 km.
The map data is sent by the radio with Auto Pilot System or by the COMMAND controller unit to the multifunction camera via the interior CAN, front SAM control unit and chassis CAN (up to 28.02.2013) or chassis CAN 2 (as of 01.03.2013).
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.
Information on vehicle movement (direction of travel and vehicle speed) is derived from the wheel speed and wheel rotation direction signals. The yaw behavior is detected by the turn rate, lateral acceleration and longitudinal acceleration sensor. The yaw rate sensor for lateral and longitudinal acceleration sends corresponding data to the Electronic Stability Program control unit via the vehicle dynamics CAN. The Electronic Stability Program control unit sends all relevant information to the multifunction camera via the chassis CAN (on vehicles up to 28.02.2013) or via chassis CAN 1 (on vehicles as of 01.03.2013), the front SAM control unit and chassis CAN 2.
The multifunction camera also combines the information about speed limit to form an event if the information is contradictory. After evaluation of the data, the multifunction camera sends corresponding requests to control the display of the currently detected speed limit to the instrument cluster via the chassis CAN (up to 28.02.2013) or chassis CAN 2 (as of 01.03.2013) and to the radio with Auto Pilot System or to the COMMAND controller unit via the chassis CAN (up to 28.02.2013) or chassis CAN 2 (as of 01.03.2013), the front SAM control unit and interior CAN. The radio with Auto Pilot System or the COMMAND controller unit processes these requests, activates the Audio/COMMAND display via the telematics CAN and generates the picture signals for displaying the speed limit. The radio with Auto Pilot System or the COMMAND controller unit then transmits the picture signals to the Audio/COMMAND display via the LVDS line.
Traffic signs recognized by the multifunction camera
The multifunction camera records all picture objects and evaluates circular as well as square contours. Speed limits and de-restriction symbols 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. 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.
Function information and system limits
Situation are listed as an example in the following, in which the pictures recorded by the multifunction camera cannot be evaluated and therefore 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. 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 clearly identified as a traffic sign, it is not displayed.
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 detection angle of the multifunction camera is ∠ a = 45°.
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, for example signs 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. 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 de-restriction 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 about the classification of roads and regional development is derived from the map data provided by the radio with Auto Pilot System or by the COMMAND 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 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 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.
Function sequence for control and display concept
The Speed Limit Assist is shown graphically on the multifunction display and the Audio/COMMAND display.
The control and display concept is split up into the following functions:
- 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
- Scroll forward/back button
- System selection button
- OK button
The steering wheel electronics read in the control signals on the multifunction steering wheel button group directly and transmit them to the steering column tube module control unit over the steering LIN. The steering column tube module control unit sends the operation signals to the instrument cluster via the chassis CAN (on vehicles up to 28.02.2013) or via chassis CAN 1 (on vehicles as of 01.03.2013), the front SAM control unit and chassis CAN 2.
The Speed Limit Assist is selected in the menu of the instrument cluster as follows:
- "Assist" main menu selection
- "Speed Limit" submenu selection
- Possibility of selecting between activate and deactivate information mode
The instrument cluster sends the status of the function to the multifunction camera via the chassis CAN (up to 28.02.2013) or chassis CAN 2 (as of 01.03.2013).
Display concept
The display concept in the multifunction display differentiates between the following variants:
- Information mode
- Permanent display
- Fault messages
Information mode
In information mode, the detected traffic sign is shown on an optional menu level on the instrument cluster for a period of t = 5 s and can be acknowledged during this period using 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.
The display in the Audio/COMMAND display is shown irrespective of the display selected in the multifunction display. The display in the map view can be activated or deactivated in the "Speed limit information" navigation menu of the radio with Auto Pilot System or the COMMAND controller unit.
The following events induce a display change or cancellation:
- Recognition of a new speed limit
- Recognition of a de-restriction 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 maximum speed for the navigation system's digital road map is shown (if available).
Fault messages
If the Speed Limit Assist fails, the message "System currently not available" (e.g. fogging of the multifunction camera caused by air humidity) or "System nonfunctional" (e.g. failure of the multifunction camera or navigation system) is shown on the multifunction display. For this purpose, the multifunction camera sends corresponding requests to the instrument cluster via the chassis CAN (up to 28.02.2013) or chassis CAN 2 (as of 01.03.2013).
In countries where the Speed Limit Assist is not available, the following message is output: "Speed Limit Assist unavailable in this country".
Display in multifunction display (depiction of the detected traffic sign is country-specific)
Display in Audio/COMMAND display, system language German (depiction of the detected traffic sign is country-specific)
Displays on multifunction display, system language German
The following events cause the de-restriction sign to be displayed (picture F):
- Passing by a de-restriction sign (picture F)
- Passing by a de-restriction sign with a speed value (picture G), if previously no traffic sign with a speed value has been recognized, the following events cause the de-restriction sign to be displayed (picture G):
- Passing by a de-restriction sign with a speed value (picture G)
- Passing by a de-restriction sign restricted by a supplementary sign (picture G1) with speed value, the following event leads to the display of a de-restriction sign (picture H):
- Passing a de-restriction sign with speed value (picture G) which deviates from the speed value of the traffic sign recorded in prior history (picture H1)
| Electrical function schematic, Speed Limit Assist | PE54.30-P-2059-97XAA | ||
| Overview of system components for driver assistance systems | GF54.00-P-9998FQ |