1. A method for controlling an internal combustion engine, comprising determining a combustion characteristic of an individual combustion event of the engine by: concurrently sampling an ionization signal and determining at least one engine operating parameter during a combustion event of the internal combustion engine, transforming the ionization signal with a wavelet filter, extracting at least one critical signal feature from the ionization signal that has been transformed by the wavelet filter; and processing the at least one critical signal feature and the at least one engine operating parameter through an artificial neural network; and controlling the internal combustion engine based upon the combustion characteristic.