Speed Limit Assist, function - GF54.30-P-0012LE

MODEL 216.3 with CODE (513) Speed Limit Assist as of model year 2011 /YoM 10 model refinement package

MODEL 221.0 /1 with CODE (513) Speed Limit Assist as of Model Year 2010 /modification year 09 model refinement package

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 through supplementary signs (as of 1.6.10)
Derestriction signs (as of 1.6.10)

As of 1.6.10, the attributes verified in the digital map of the navigation system are also evaluated.

The appropriate traffic signs are shown in the multifunction display (A1p13) and in the COMAND display (A40/8) (without code (867) SPLITVIEW) or in the SPLITVIEW display (A40/10) (with code (867) SPLITVIEW).

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 manner in which the traffic signs are shown depends on the settings in the "Speed Limit Asst." menu in the instrument cluster (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) signals.

These are read in and evaluated by the COMAND control unit (A40/3). The navigation data is sent from the COMAND controller unit via the central CAN (CAN F) to the central gateway control unit (N93) which forwards the data via the chassis CAN to the multifunction camera.

The Speed Limit Assist function is not available in the event of failure of the COMAND controller unit.

In the event of a temporary failure, the Speed Limit Assist function is only maintained for a travel distance of s = 30 km.

The Speed Limit Assist function is permanently active, but must be activated in the "Assistance" menu of the instrument cluster in order for information to be displayed. The instrument cluster sends the status via the central CAN to the central gateway control unit which forwards the appropriate status via the chassis CAN to the multifunction camera.

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 ∠ = 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 from COMAND controller unit
Vehicle's intrinsic motion and yaw behavior, provided via chassis CAN by ESP control unit (N47-5) (without model 221.095/195) or by regenerative braking system control unit (N30/6) (model 221.095/195)

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 behavior of the vehicle and transmits this via the vehicle dynamics CAN (CAN H) to the ESP control unit or to the regenerative braking system control unit which passes on this information to the multifunction camera via the chassis CAN.

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 camera does not detect any speed limits, the values verified in the digital card of the navigation system are displayed. 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 evaluation of the data, the multifunction camera sends a request to control the display of the currently detected speed limit, to the instrument cluster and the COMAND controller unit via the chassis CAN, central gateway control unit and central CAN.

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 to form a result even when the individual items of information are contradictory.

Traffic signs recognized by multifunction camera:

Fig 1: Identifying Traffic Signs Recognized By Multifunction Camera

Courtesy of MERCEDES-BENZ USA

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.

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) are not shown. The number of these traffic signs amounts to approx. 10% of all traffic signs.

Situations are listed as an example in the following, in which pictures recorded by the multifunction camera are not usable and are not 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. These traffic signs however, are filed through the road definition feature (e.g. freeway) in the digital navigation map.

Fig 2: Identifying Town/Village Entry And Exit Signs

Courtesy of MERCEDES-BENZ USA

Electronically actuated changing traffic signs can be "missed" or interpreted incorrectly. With alternating traffic signs that pulse or flash, there may be a difference in the fixed cycle time for picture recording with regard to the frequency of the alternating traffic sign, which in turn leads to only fragments of such alternating traffic signs being detected.

If the picture cannot be fully recognized as a traffic sign it is not shown on the display.

Fig 3: Identifying Traffic Sign In Red Color

Courtesy of MERCEDES-BENZ USA

Changing traffic signs on which the outer circle is missing are not shown either.

Fig 4: Identifying Traffic Sign (Outer Circle Missing)

Courtesy of MERCEDES-BENZ USA

The horizontal angle of vision of the multifunction camera is limited.

Traffic signs erected immediately after junctions, turn-offs which the vehicle takes, can be "missed" by the multifunction camera.

The horizontal recording angle of the multifunction camera is a = 34°.

Fig 5: Identifying Horizontal Recording Angle Of Multifunction Camera

Courtesy of MERCEDES-BENZ USA

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 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, as used in construction sites, are "missed" if they are passed at high speed.

Fig 6: Identifying Dimensions Of Evaluation Window At Vehicle Speed

Courtesy of MERCEDES-BENZ USA

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.

Fig 7: Identifying Display - Resolution Of Multifunction Camera

Courtesy of MERCEDES-BENZ USA

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 viewing direction 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 destriction signs by mistake (left picture).

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

Fig 8: Identifying Display - Unfavorably Designed Back-End Sections Of Commercial Vehicle

Courtesy of MERCEDES-BENZ USA

Fig 9: Identifying Display - Signage On Back-End Section Of Commercial Vehicle

Courtesy of MERCEDES-BENZ USA

Information on the classification of roads and regional development are deduced from the navigation data provided by 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.

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.

Fig 10: Identifying Display - Information On Classification Of Roads And Regional Development

Courtesy of MERCEDES-BENZ USA

Function sequence for control and display concept

The graphical display of the Speed Limit Assist function is output via the multifunction display and also via the COMAND display (without code (867) SPLITVIEW) or SPLITVIEW display (with code (867) SPLITVIEW). Operation is via the menu of the instrument cluster using the left multifunction steering wheel button group (S110). The control and display concept is split up into the following subfunctions:

Operating concept
Display concept

Operating concept

Operation is via the "Speed Limit Asst." menu level of the instrument cluster using the following controls:

Left multifunction steering wheel button group
- Scroll forward/back button (S110s1)
- System selection button (S110s3)
- OK button (S110s6)

The control signals of the left multifunction steering wheel button group are sent by the steering wheel electronics (N135) via the steering LIN (LIN E1) to the steering column tube module (N80). The steering column tube module sends the control signals via the chassis CAN to the central gateway control unit which forwards the control signals to the instrument cluster via the central CAN.

The Speed Limit Assist function is selected as follows in the instrument cluster:

Selection of "Assistance" main menu (using scroll forward and back button and system selection button)
Confirmation of selection (using OK button)
- Selection option: permanent display or information model

Display concept

The display concept distinguishes between the following variants:

Information mode
Permanent display
Error messages

Information mode

In the information mode, a detected traffic sign can be shown on any menu level on the instrument cluster for a duration of t = 5 s and can be acknowledged within this time using the OK button.

The information mode can be switched on and off in the "Speed Limit Asst." submenu in the "Assistance" menu.

The status is displayed by the fading in of the appropriate pictogram.

Permanent display

When the "Speed Limit" submenu in the "Assist" menu in the instrument cluster is selected, the detected 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 traffic signs are shown in the map view of the COMAND display regardless of the display selected in the instrument cluster. This can be activated or deactivated in the "Speed Limit Information" navigation menu of the COMAND controller unit.

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 relating to 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) is shown in the multifunction display.

The Speed Limit Assist pictogram also disappears in the 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".

Display in multifunction display

Fig 11: Identifying Display - Speed Limit Assist Pictogram And Recognized Speed Limit

Courtesy of MERCEDES-BENZ USA

Visual output of derestriction sign

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.

The following events cause the derestriction sign to be displayed (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).

Fig 12: Identifying Visual Output Of Derestriction Sign
Courtesy of MERCEDES-BENZ USA

	Speed Limit Assist, location of components		GF54.30-P-0012-01LE
	Electrical function schematic, Speed Limit Assist	Model 216	PE54.30-P-2059-97CAA
	Electrical function schematic, Speed Limit Assist	Model 221	PE54.30-P-2059-97SAA
	Speed Limit Assist, block diagram		GF54.30-P-0012-02LE
	Component description for instrument cluster	A1 Model 216.3, model 221 (except 221.095/195)	GF54.30-P-6000LE
	Component description for instrument cluster	Model 221.095/195	GF54.30-P-6000LEH
	Component description for COMAND controller unit	A40/3	GF82.85-P-3136LE
	COMAND display, component description	A40/8 Without code (867) SPLITVIEW	GF54.0P-6110LE
	SPLITVIEW display, component description	A40/10 with code (867) SPLITVIEW as of 1.6.09	GF54.30-P-6120LE
	Component description for multifunction camera	A40/11	GF54.21-P-3300LE
	Yaw rate sensor for lateral and longitudinal acceleration, component description	B24/15	GF42.45-P-4810LE
Component description for ME-SFI [ME] control unit		With engine 275	GF07.61-P-6000MOS
On model 221 with engine 276	GF07.61-P-6000MMB
	Component description for regenerative braking system control unit	N30/6 On model 221.095/195	GF42.22-P-1100LEH
	Component description for ESP control unit	N47-5 Model 216.3, model 221 (except 221.095/195)	GF42.45-P-5118LE
	Component description for steering column tube module	N80	GF54.21-P-6050LE
	Component description for central gateway control unit	N93	GF54.21-P-4170LE