Main State Variable (Energy Requirement Level)

Main State Variable (Energy Requirement Level)

When the air conditioning system is in operation, all control functions for the system are dependent on this main state variable, ERL.

The main state variable to determine the thermal energy requirement level in the vehicle, in the form of the ERL signal, is derived from the key influencing variables:
- Set interior temperature
- Actual interior temperature
- Outside temperature
- Solar radiation energy
- A/c compressor on/off

The main state variable for determining the thermal energy requirement in the vehicle - the ERL signal - is derived. The ERL state variable varies as a digital number in the range from 0 to 255 (8 bit). This corresponds to the extreme cases of "0" for maximum cooling requirement and "255" for maximum heating requirement.

The influencing variables 'coolant temperature' and 'engine running time' serve as additional reference values to adapt the control functions in special cases, e.g. start-up of the air conditioning, cold start, hot start of the vehicle.