Tyre Pressure Control

Many types of tyre damage is indicated by a loss of tyre pressure. Tyre pressure control warns the driver when tyre pressure is lost on one or more wheels. This can also prevent preliminary damaged to a tyre.
Tyre pressure control is a system for monitoring the tyre pressure when driving. Tyre pressure control does not mean that the driver does not need to check the tyre pressure regularly. Initialization of the tyre pressure monitoring system must be triggered following each change in tyre inflation pressure as well as after every tyre changes.

Component description
The tyre pressure monitoring system functionality has now been integrated in the Dynamic Stability Control (DSC) system.
The remote control receiver reveives the radio signals from the wheel electronics. The remote control receiver is connected via LIN bus to the Body Domain Controller. The BDC forwards the signals via the bus connection to the DSC control unit.
The DSC control unit processes the messages transmitted by the wheel electronics. Above a speed of 20 - 30 km/h, the following messages are sent by the electronics on each wheel:

• Tyre pressure
• Tyre air temperature
• Remaining service life of the battery
• Data from the acceleration sensor and Identification Feature (ID) of the wheel electronics
• Transmission mode (passive, standby, learning)

The DSC control unit transmits information to the instrument cluster and headunit. The instrument cluster indicates tyre pressure loss via a warning and indicator light and issues a Check Control Message.

Wheel electronics
In all wheels, wheel electronics systems are installed in the wheel drop centre. The wheel electronics systems are bolted onto the filling valves (made of metals). All wheels electronics systems are common parts. The wheel electronics monitor the actual temperature in the tyre.
Each wheel electronics unit incorporated an acceleration sensor. The acceleration sensor recognizes whether the wheel is stationary or rotating. When the wheels are stationary the remote receiver does not transmit messages to the DSC. The wheel electronics are in their passive state. This extends the service life of the batteries in the wheel electronics. Once the vehicle reaches 30 km/h the wheel electronics switch to their standby mode. The wheel electronics start to transmit in defined cycles.
The wheel electronics measure the tyre inflation pressure and temperature at regular periodic intervals. The remote receiver relays these monitored data from the tyre to the DSC in periodic cycles.
The DSC control unit relies on the identification number that accompanies the transmissions to assign the information to individual wheels.

Wheel assignment
During the wheel assignment identification process the wheel electronics are in the learning mode. Wheel rotation generates centrifugal force. The acceleration sensor starts to recognize this centrifugal force at a vehicle speed of approximately 30 km/h. The acceleration sensor relies on the earth's gravitational force to identify the wheel electronics' vertical position (12 o'clock).
This position is needed for the learning mode.
In the learning mode the DSC identifies the positions of the four individual wheels with assistance from wheel sensors.

Remote control receiver
The messages of the wheel electronics are transmitted via high-frequency transmission path (433 Mhz) to the remote control receiver. The measuring cycle of the wheel electronics is 3 seconds. Transmission to the remote control receiver takes place every 30 seconds. The current status of the messages is forwarded on the LIN bus to the BDC. BDC control unit forwards the mesages via the Flexray to the DSC control unit. The DSC control unit evaluates the messages.