GF82.61-P-2010LE Position Finding and Destination-Oriented Navigation, Function
GF82.61-P-2010LE Position Finding And Destination-oriented Navigation, Function
- with CODE (527) COMAND APS with single DVD drive (with navigation)
- with CODE (530) COMAND APS USA (with navigation)
Function requirements, general
^ C. 30g ON or c. 15R ON
^ The Cockpit Management and Data System (COMAND) is authorized and working correctly.
^ Signals from at least three Global Positioning System (GPS) satellites present
Position finding and destination-oriented navigation, general
The position finding function and navigation consists of the following subfunctions:
^ Function sequence for GPS position finding
^ Basic position finding function sequence
^ Destination-oriented navigation function sequence
^ Function sequence for dynamic route guidance
^ Function sequence for navigation with lane recomendations
Function sequence for GPS position finding
The GPS is a satellite-based positioning system. It is available worldwide. The GPS satellites permanently transmit time and position data (longitude and latitude). GPS position finding is irretrievable after vehicle transport (e.g. by train or ferry or after towing). A new GPS position (after interruption of the satellite reception) can take several minutes (up to t = 20 minutes when the equipment is commissioned).
The accuracy of the position finding and the actual calculation are essentially based on the measurement of the runtimes of the signals transmitted synchronously by the various satellites. An important prerequisite is the synchronicity of the clocks of the satellites and the receiver. To this end the receiver is equipped with an automatic time correction, which in turn is made possible with the aid of the satellite signals.
Since GPS operates in the giga hertz (GHz) range (microwaves) and the signals are weak, reception interference can occur as a result of the following events:
- Atmospheric interference, e.g. inclement weather, water vapor, fog
- Multi-path reception due to signal reflections, e.g. from building walls
- Signal shadowing, e.g. in built-up areas and in tunnels, by high buildings, by trees
The GPS signals are received by the GPS receiver integrated into the COMAND controller unit (A40/3) directly from the telephone and GPS roof antenna (A2/49) (model 221) or from the telephone and GPS antenna (A2/49) (model 216). For vehicles with code (359) TELE AID emergency call system, the GPS signals are relayed to the COMAND controller unit via the antenna splitter (A2/5).
The GPS signals are used by the COMAND controller unit to calculate the current vehicle position (receiver).
In addition, the vehicle's direction of travel is determined with the aid of the sequence of the locations calculated with GPS.
Basic position finding function sequence
Basic position finding runs parallel to GPS position finding. For basic position finding the COMAND control unit requires the following information:
- Wheel speeds
- Distance traveled data
- Vehicle alignment (cardinal points)
- Direction of travel data (forwards or backwards)
The wheel speeds are recorded by the following components:
- Left front rpm sensor (L6/1)
- Right front rpm sensor (L6/2)
- Left rear rpm sensor (L6/3)
- Right rear rpm sensor (L6/4)
The rpm sensor signals are provided over the following route:
- Direct line
- Regenerative braking system control unit (N30/6) (model 221.095/195) or
- ESP control unit (N47-5) model 216.3, 221.0/1 (except model 221.095/195))
- Chassis CAN (CAN E)
- Central gateway control unit (N93)
- Central CAN (CAN F)
- COMAND controller unit
Information on the vehicle direction is sensed and processed internally by the turn rate sensor (gyrosensor) in the COMAND control unit.
Information on direction of travel is provided over the following route:
- Regenerative braking system control unit or ESP control unit
- Chassis CAN
- Central gateway control unit
- Central CAN
- COMAND controller unit
The COMAND control unit uses the distance traveled, the vehicle alignment and the direction of travel to determine the vehicle's current position (longitude and latitude).
This computation is performed approx. every t =1/s.
Location finding errors during position finding can occur by rolling backwards with c. 15 OFF (ignition switched off) or when a vehicle is transported. In both cases, the deviation is automatically corrected by the navigation processor integrated in the radio with auto pilot system.
The calibration following a tire replacement is performed automatically. Because of the tire abrasion, a constant recalibration of the tire circumference is required. It is carried out automatically and uses the difference between the calculated and actually traveled distance between turning points calculated with the aid of map-based position finding.
Destination-oriented navigation function sequence
The integrated navigation processor continuously compares the route calculation data with the position finding data and uses the data to deduce measures for further destination-oriented navigation.
The audio signals for navigation voice output are transmitted by the COMAND controller unit via the Media Oriented System Transport (MOST) to the audio tuner control unit (N93/1), which amplifies them and outputs them over the speakers listed below.
Model 216:
- Left door speaker group (H4/1)
(without code (810) Sound system)
- Right door speaker group (H4/2)
(without code (810) Sound system)
- Left door rear speaker (H4/3)
- Right door rear speaker (H4/4)
- Bass module speaker (H4/17
- Center cockpit speaker (centerfill) (H4/27)
- Left door Sound tweeter (H4/68)
(with code (810) Sound system)
- Right door Sound tweeter (H4/69)
(with code (810) Sound system)
- Left door Sound woofer and midrange speaker group (H4/72)
(with code (810) Sound system)
- Right door Sound woofer and midrange speaker group (H4/73)
(with code (810) Sound system)
Model 221:
- Left front door speaker group (H4/1)
(without code (810) Sound system)
- Right front door speaker group (H4/2)
(without code (810) Sound system)
- Left rear door speaker group (H4/3)
- Right rear door speaker group (H4/4)
- Bass module speaker
- Center cockpit speaker (centerfill)
- Left front door Sound tweeter (H4/68)
(with code (810) Sound system)
- Right front door Sound tweeter (H4/69)
(with code (810) Sound system)
- Left front door Sound woofer and midrange speaker group (H4/72)
(with code (810) Sound system)
- Right front door Sound woofer and midrange speaker group (H4/73)
(with code (810) Sound system)
The signals for visually displaying the navigation (map navigation) are generated by the COMAND controller unit and transmitted over a low voltage differential signaling (LVDS) line to the COMAND display (A40/8) (without code (867) SPLITVIEW) or to the SPLITVIEW display (A40/10) (with code (867) SPLITVIEW) where they are displayed.
In addition, arrow pictograms for navigation are displayed in the multifunction display (A1p13) of the instrument cluster (A1). The instrument cluster receives the signals for this from the COMAND controller unit via the central CAN.
Function sequence for dynamic route guidance
The dynamic route guidance considers the current traffic situation. The information concerning the traffic situation is transmitted via FM on a regional basis by specially equipped radio stations and is received by the radio data system (RDS) function or the traffic message channel (TMC) via the FM radio.
A suitable FM/RDS transmitter must be tuned in.
The traffic data recorder decodes the traffic information and forwards it internally to the navigation processor upon request. The navigation processor makes the decision whether the route should be changed. If necessary, a message that the route was changed is output over the speakers.
The FM receiver in the audio tuner control unit receives the traffic messages via the rear window antenna amplifier module (A2/12) and routes them to the traffic data recorder in the COMAND controller unit. The traffic messages are stored in the traffic data recorder of the COMAND controller unit and made available to the integrated navigation processor.
Function sequence for navigation with lane recommendations
In certain turnoff situations (e.g. multilane exits or freeway intersections), lane recommendations are given in the footer of the COMAND display or the SPLITVIEW display. Along with a turnoff recommendation, the distance to the actual turnoff point is also displayed by means of a bar graph. The lanes have arrows assigned to them, which indicate the lane by which the destination can be reached or the best way to reach it.
The following colors apply to the representation on the COMAND display or SPLITVIEW display:
Midnight blue: Best or recommended lane
Light blue: Lane is correct, but a lane change will soon be required
Gray: Lane will not take you to the destination
Only dark blue arrows are displayed in the instrument cluster's multifunction display.
Map display is always controlled by the COMAND controller unit. The following display functions are supported:
- Destination-oriented navigation map
- Position map (with geo coordinates, altitude and number of receivable satellites)
- Route map
- Scrollable map
- Destination entry map
