GF82.61-P-2010RCJ Position Finding and Destination-Oriented Navigation, Function
GF82.61-P-2010RCJ Position Finding And Destination-oriented Navigation, Function
- with CODE (527) COMAND APS with single DVD drive (with navigation)
- with CODE (498) Japan version
Function requirements
^ Status "Circuit 30 ON" for Global Positioning System (GPS)position finding
^ Status "Circuit 15R ON", for basic position finding
^ COMAND operating, display and controller unit (A40/3) activated via "ON" button
^ "Navi" menu selected
^ Current navigation data loaded
^ Destination has been entered
^ No error in GPS antenna system
^ Signals available from at least 3 GPS satellites
General position finding
GPS 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 20 minutes when the equipment is commissioned).
Basic position finding runs parallel to GPS position finding. The position finding function consists of the following component functions:
^ Function sequence for GPS position finding
^ Basic position finding function sequence
^ Destination-oriented navigation function sequence
Function sequence for GPS position finding
The global positioning system receiver is integrated into the COMAND controller unit. It receives the GPS signals from the GPS antenna (A2/23) over the following path:
- Direct line
- COMAND controller unit
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.
Possible problems in GPS signal reception
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
- Multiple path reception due to reflection of the signals
- Signal blocking, e.g. in built-over areas and in tunnels, through high-rise buildings, trees
Basic position finding function sequence
For basic position finding the COMAND controller unit requires the
following information:
- Wheel speed signals
- Distance traveled data
- Vehicle alignment (cardinal points)
- Direction of travel data (forwards or backwards)
The wheel speed signals are recorded by the following rpm sensors:
- 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 wheel speed signals are received by the COMAND controller unit from the rpm sensors in the following way:
- Direct line
- ESP and BAS control unit (N47-5)
- Engine compartment CAN
- Central gateway control unit (N93)
- Interior CAN
The travel distance data is also determined from the wheel speeds.
The vehicle alignment data (change in angle) is processed internally by the COMAND controller unit's integrated turn rate sensor (gyro sensor).
The direction of travel data (forward or backward) is transferred to the COMAND controller unit by the central gateway control unit via the interior CAN. The COMAND controller unit then calculates the coupled position from the distance traveled and taking the vehicle alignment and direction of travel into consideration.
This coupled position is compared with the GPS data (longitude, latitude, direction). This position data is then compared with the map data (map matching). In order to identify the street level (elevated highway), the vertical angle (from the 3D gyro) as well as the data from ETC gates and VICS beacons are taken into consideration (dealer option).
Error during position finding
Basic position finding is falsified when a vehicle rolls backwards with "circuit 15 OFF" (ignition switched off) or if it is transported somewhere. In both instances the deviation is automatically corrected by the COMAND controller unit's integrated navigation processor upon reception of GPS data.
Destination-oriented navigation function sequence
The destination-oriented navigation consists of the following subfunctions:
^ Destination-oriented navigation function sequence through voice output
^ Destination-oriented navigation function sequence through visual display
^ Function sequence for Vehicle Information and Communication System (VICS) over FM multiplexer
^ Dynamic route guidance function sequence, VICS (dealer option)
Destination-oriented navigation function sequence through voice output
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 destination-oriented navigation voice output is emitted over discrete lines to the following speakers:
- Left door speaker group (H4/1)
- Right door speaker group (H4/2)
- Center cockpit speaker (centerfill) (H4/27)
Destination-oriented navigation function sequence through visual display
The signals for visually displaying navigation (map navigation) are generated by the COMAND controller unit and shown on the display on the COMAND controller unit.
VICS function sequence over FM multiplexer
The driver is provided with vital information by the VICS on the current traffic situation. Traffic impairments and traffic jams are shown on the map, however they are not incorporated into the dynamic route guidance. The radio antenna signal path is as follows:
- Rod antenna (A28)
- Direct line
- Left antenna amplifier module (A2/64)
- Direct line
- COMAND controller unit
The VICS information is processed in the FM multiplexer integrated into the COMAND controller unit. The information is then shown on the display on the COMAND controller unit. In addition, the FM multiplexer can also receive additional information, e.g. on the weather or earthquakes
Dynamic route guidance function sequence, VICS (dealer option)
For dynamic route guidance, it is necessary to retrofit the VICS antenna (A2/96) (dealer option). The VICS function is integrated into the COMAND controller unit. The VICS antenna communicates in the microwave range (2.5 GHz) with the VICS beacons installed along the road (transmission antennas). Received signals are sent directly to the COMAND controller unit where they are decoded. The traffic messages are stored and provided to the integrated navigation processor. The navigation processor makes the decision whether the route should be changed. If necessary, a message that the route was changed is output via the vehicle speaker. The VICS signals are routed as follows:
- VICS antenna
- Direct line
- COMAND controller unit
