Patent ID: 9000710
Filing Date: 2015-04-07
Classification: G01P,Y10S

Abstract:
1. A method of determining motor speed of a brush DC motor, comprising: sensing a current from the brush DC motor; low pass filtering the sensed current to produce a low frequency current signal; filtering the low frequency current signal to substantially regularly estimate motor speed based in part upon model parameters of the brush DC motor; bandpass filtering, by a bandpass filter, the sensed current to generate a bandpass filtered signal, wherein the bandpass filter uses the motor speed estimate as a center frequency thereof; detecting zero crossings of the bandpass filtered signal, wherein a frequency of the detected zero crossings corresponds to the motor speed of the brush DC motor; and determining whether each of a plurality of the most recent motor speed estimates falls outside a passband of the bandpass filter, and switching the center frequency of the bandpass filter based upon the determination.