GF82.61-P-2010CWJ Position Finding and Destination-Oriented Navigation, Function

GF82.61-P-2010CWJ Position finding and destination-oriented navigation, function
- with CODE (498) Japan version


Function requirements
^ Status "circuit 30 ON", for the Global Positioning System (GPS) position finding
^ Status "circuit 15R ON", for the basic position finding
^ COMAND 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 subfunctions:
^ GPS position finding function sequence
^ 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 multifunction antenna (A28/11) in the following way:
^ Discrete 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.

Basic position finding function sequence
For basic position finding the COMAND controller unit requires the following information:
^ Wheel speed signals
^ Data on the distance traveled
^ Vehicle alignment (cardinal points)
^ Direction of travel data (forwards or backwards)

The wheel speed signals are recorded by the following rpm sensors:
^ Left front axle rpm sensor (L6/1)
^ Right front axle rpm sensor (L6/2)
^ Left rear axle rpm sensor (L6/3)
^ Right rear axle rpm sensor (L6/4)

The wheel speed signals are received by the COMAND controller unit from the rpm sensors in the following way:
^ Discrete line
^ Electronic Stability Program control unit (N30/4)
^ Chassis CAN
^ Front SAM control unit with fuse and relay module (N10/1)
^ Interior CAN

The distance traveled data is received by the COMAND controller unit from the instrument cluster (A1) in the following way:
^ Interior CAN
^ COMAND controller unit

The vehicle alignment data (cardinal points) is internally processed by the COMAND controller unit's integrated turn rate sensor (gyro sensor).
The direction of travel data (forwards or backwards) is received by the COMAND controller unit over the interior CAN from the front SAM control unit with fuse and relay module.
After this the COMAND controller unit uses the distance traveled, the vehicle alignment and the direction of travel to calculate the vehicle position (degree of longitude and degree of latitude) at any given time.

Calculation of the basic position finding takes approx. 1/s.

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.

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
^ Multi-path reception due to signal reflections, e.g. from building walls
^ Signal blocking, e.g. in built-over areas and in tunnels, through high-rise buildings, trees

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 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 voice output for destination-oriented navigation is placed on the Media Oriented System Transport (MOST) via the COMAND controller unit and then amplified in the sound system amplifier control unit (N40/3) (with code (810) Sound system).

The voice signals are transmitted on discrete lines via the sound
system amplifier control unit to the following speakers:
^ Left front door speaker (H4/1)
^ Right front door speaker (H4/2)
^ Center instrument panel speaker (H4/27)

In vehicles except code (810) Sound system, the voice output takes place on discrete lines via the COMAND control unit to the following speakers:
^ Left front door speaker
^ Right front door speaker
^ Center instrument panel speaker

Destination-oriented navigation function sequence through visual display
The signals for destination-oriented navigation visual display (map navigation) are generated by the COMAND controller unit and forwarded over a low voltage differential signaling (LVDS) line to the Audio/COMAND display (A40/8).

The Audio/COMAND display switch-on request is generated by the COMAND controller unit over the telematics CAN.

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:
^ Rear window antennas
^ Discrete line
^ Rear window antenna amplifier 1 (A2/71)
^ Discrete line
^ COMAND controller unit

The VICS information is processed in the FM multiplexer integrated into the COMAND controller unit. Next, the information is shown on the Audio/COMAND display. Apart from this, the FM multiplexer can also receive additional information, e.g. on the weather or earthquakes.

Dynamic route guidance function sequence, VICS (dealer option) Dynamic route guidance requires the so-called VICS control unit (A2/37) (dealer option). The VICS control unit contains both the receiver and the antenna. The antenna communicates with the VICS beacons (transmission rods) installed on the roads, which transmit FM or infrared signals. Received signals are sent directly to the COMAND controller unit where they are decoded. The traffic messages are stored and made available to the navigation processor in the following way:
^ VICS antenna
^ VICS control unit
^ Discrete line

The traffic data recorder decodes the traffic information and forwards it 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 via the vehicle speaker.