Patent ID: 8903668
Filing Date: 2014-12-02
Classification: B60W,B60Y,G01P,H02J

Abstract:
1. A method for determining a speed of an alternator, said method comprising: determining an output current or voltage signal of the alternator, where the output current or voltage signal includes a ripple current frequency as a result of an AC-to-DC conversion; filtering the current or voltage signal to remove known harmonic frequencies; performing a Fast Fourier Transform (FFT) operation to identify a frequency spectrum signal of the filtered current or voltage signal, including performing an FFT operation having a limited number of data points; identifying a peak detection search range within the frequency spectrum signal within which the ripple current frequency is known to exist; determining if a previous ripple current frequency determination has been made and if so identifying a peak detection search range includes identifying the search range as a predetermined limited number of data points around that ripple current frequency; identifying a highest peak frequency within the search range as the ripple current frequency; and converting the highest peak frequency to the alternator speed.