Control Module

Fig 1: Identifying Global Positioning System Module (GPS)

Courtesy of VOLVO CARS CORPORATION

The global positioning system module (GPS) has a built-in 12 channel GPS receiver. The receiver is optimized for a frequency of 1575.42 MHz.

The global positioning system module (GPS) transmits two signals:

• A signal to the infotainment control module (ICM) indicating that the control module is awake.
• A combination signal to the Phone module (PHM). Current, received position is transmitted when it is available, otherwise a calculated position is transmitted, based on the last known received position.

If there is no, or poor communication, with the GPS satellites, for example when in a tunnel, the global positioning system module (GPS) uses the information from other control modules for dead reckoning (i. e. to calculate the position of the vehicle).

The global positioning system module (GPS) requires the following to calculate the actual position:

• the information from the wheel rotation counters stored in the brake control module (BCM)
• information about back-up (reverse) gear from the transmission control module (TCM)
• information about whether the parking brake is applied from the driver information module (DIM)
• information about whether the brake pedal is pressed or not from the brake control module (BCM)
• information about the extent to which the traction control system is activated from the brake control module (BCM)
• information about wheel size from the central electronic module (CEM).

All information is transmitted via the infotainment control module (ICM).

The navigation system needs signals from at least three GPS satellites to calculate the position of the vehicle in two planes.

For three dimensional position reckoning, signals are required from at least four satellites.

The position is measured both vertically and horizontally. The antenna continuously transmits information about the position of the vehicle to the GPS receiver. The position is accurate to within a maximum of 25 meters from the position calculated by both the GPS signal and dead reckoning. The accuracy is somewhat reduced when only dead reckoning is used. The fault increases with distance driven since position lost.

If there is signal interference, when traveling in tunnels or high rise areas for example, the accuracy may be reduced slightly.

For the system to determine the position as exactly as possible, the system must differentiate between signals coming directly the GPS satellites or those reflected by a high rise building for example.

When the ignition is switched off the power consumption of the GPS receiver must not exceed 0.1 mA. The receiver stores important information, such as the last GPS signal received if the power is cut.

The system can endure temperatures between -40 °C and 85 °C.

The global positioning system module (GPS) checks the input and output signals through an integrated diagnostic system.