GF82.61-P-3006T Basic Position Finding, Function

GF82.61-P-3006T Basic Position Finding, Function
- with CODE (525) MB Audio 50 APS radio
- with CODE (527) COMAND APS (with navigation)






The navigation processor for the radio control panel and navigation unit (A2/56), with code (525) MB Audio 50 APS radio, is integrated into the operating unit. With the COMAND operating, display and control unit (A40/3), with code (527) COMAND APS (with navigation), the external navigation module is referred to as a navigation processor (N41/1).

Function diagram on example of COMAND system, code (527) COMAND APS (with navigation)
Basic position finding is the basic function of continuous position finding. It is carried out continuously by the navigation processor (N41/1) with "Circuit 15R ON" and is independent of the CD-ROM map. After "Circuit 15R OFF" the current position is stored. The following information is calculated with the aid of basic position finding:
^ Travel distance covered
^ Direction of travel (backwards or forwards)
^ Vehicle alignment

Distance traveled
Through the wheel direction of rotation signal, which is determined by the left front rpm sensor (L6/1), right front rpm sensor (L6/2), left rear rpm sensor (L6/3) and right rear rpm sensor (L6/4) and is read in discretely by the ESP control unit (N47-5). This message is transmitted to the CAN engine compartment (CAN-C) and transferred from the central gateway control unit (N93) on the CAN interior (CAN-B). As a result, the navigation processor (N41/1) detects the direction of travel (forward or reverse).

Direction of travel
The navigation processor (N41/1) receives the wheel speed signals from the ESP control unit (N47-5) as described above. Evaluation of the wheel speed signals results in the travel distance covered.

The basic position finding is performed approx. every 1 s.

Vehicle orientation
From the data of the yaw rate sensor (gyro sensor) and the sequence of the locations calculated using GPS, the navigation processor (N41/1) calculates the orientation (compass direction) of the vehicle. The difference between the calculated and actual distance traveled between two turns is used for the automatic recalibration of the tire circumference.

Errors with basic position finding
Rolling with the ignition switched off or transport of the vehicle also make the position finding result erroneous. In both cases, this deviation is automatically corrected by the navigation processor (N41/1) on receipt of GPS data.

Calibration
Wheel calibration is necessary following a tire change. To this end, it is necessary to enter the tire size, e.g. 225/060/016 and the coding as to whether new (depth of tread approx. 5 to 10 mm) or used tires (depth of tread approx. 3 to 5 mm) have been fitted. Entries are made using STAR DIAGNOSIS or directly on the COMAND operating, display and control unit (A40/3). A special calibration journey is not required.