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

GF82.61-P-2010CEJ 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 30g ON", for global positioning system (GPS) position finding
^ Status "Circuit 15R ON", for basic position finding
^ COMAND controller unit (A40/3) activated via ON button on the COMAND controller unit
^ Navi menu item selected
^ Destination has been entered
^ No error in GPS antenna system
^ Signals available from at least 3 GPS satellites

General
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 multifunction antenna (A28/11) through a direct line: 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
- 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

Basic position finding function sequence
For basic position finding the COMAND control 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 components:
- 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 control unit from the rpm sensors in the following way:
- Direct line
- Electronic Stability Program control unit (N30/4)
- Chassis CAN (CAN E)
- Front SAM control unit with fuse and relay module (/)N10/1
- Interior CAN (CAN B)

The data of the distance traveled is received by the COMAND controller unit from the instrument cluster (A1) via the interior CAN:
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.

Destination-oriented navigation function sequence
The navigation system comprises 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 voice output for the navigation is output over the following speakers by the COMAND controller unit via direct lines:
- Left front door speaker (H4/1)
- Right front door speaker (H4/2)

Destination-oriented navigation function sequence through visual display
The signals for visual display of the navigation (map navigation) are generated by the COMAND controller unit and transmitted to the Audio/COMAND display (A40/8) via a low voltage differential signaling (LVDS) line. The Audio/COMAND display switch-on request is generated by the COMAND controller unit via the telematics CAN (CAN A).

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 travels to the COMAND controller unit as follows:
- Rear window antenna structure
- Direct line
- Rear window antenna amplifier 1 (A2/71) (model 204.2/9) or FM, AM and CL [ZV] (A2/18) antenna amplifier (model 204.0)
- Direct line

The VICS information is processed in the FM multiplexer integrated into the COMAND controller unit. The information is then displayed on the Audio/COMAND display by means of the low voltage differential signaling line. 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)
Dynamic route guidance requires the so-called VICS control unit (A2/37). The VICS control unit contains both the receiver and the antenna. The antenna communicates with the VICS beacons (transmitter masts) installed on the road, which transmit microwave or infrared signals in a reception range of 2.5 GHz. Received signals are sent directly to the COMAND control unit where they are decoded. The traffic messages are stored and relayed to the navigation processor.
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. The voice output for the dynamic route guidance is output over the following speakers by the COMAND controller unit via direct lines:
- Left front door speaker
- Right front door speaker