US 9,000,710 B2 · Method and apparatus for measuring speed of a brush motor

Abstract

A system for determining motor speed of a brush DC motor in an apparatus, including a first filter for receiving a substantially DC component of the motor current and parameters corresponding to the brush DC motor, for calculating a speed estimate thereof; an adaptive bandpass filter having a center frequency corresponding to the speed estimate of the first filter, for receiving the motor current and substantially isolating a periodic current fluctuation thereof; a block for determining a frequency of the periodic current fluctuation, the current fluctuation corresponding to motor speed of the brush DC motor. The adaptive bandpass filter uses debounce filtering to reduce rapid filter passband switching, and a run-in period prior to passband switching to obviate transient effects of filter switching.

Claims19

Dependent claims

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.

4 more elements

A system for determining motor speed of a brush DC motor in an apparatus, comprising:

a first filter for receiving a low frequency component of a current signal of the brush DC motor and parameters corresponding to the brush DC motor, and calculating a speed estimate thereof;
an adaptive bandpass filter having a center frequency corresponding to the speed estimate of the first filter, for receiving the current signal and substantially isolating a periodic current fluctuation thereof;
and
a frequency detect block for determining a frequency of the periodic current fluctuation, a frequency of the periodic current fluctuation corresponding to motor speed of the brush DC motor;
wherein the first filter substantially regularly calculates speed estimates of the brush DC motor, and the center frequency of the adaptive bandpass filter is switched to a new center frequency following a determination that each of a plurality of most recent speed estimates by the first filter falls outside of a predetermined central portion of a passband of the adaptive bandpass filter.

2 more elements

Dependencies are inferred from the claim text.

Method and apparatus for measuring speed of a brush motor

Life of this patent

Method and apparatus for measuring speed of a brush motor

Life of this patent

Abstract

Claims19