System and method for attenuating noise associated with a back electromotive force signal in a motor
AssigneeAgile Systems Inc.
InventorDavid MacKay
Life of this patent
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Abstract
A method for attenuating switching noise from back electromotive force (EMF) observations in a motor is described. The motor is controlled by pulse width modulation (PWM) signals provided at a PWM frequency. The method comprises sampling back EMF observed in the motor at a sampling frequency at least two times greater than the PWM frequency to obtain over-sampled back EMF readings. The oversampled readings may be used in a raw or filtered form to commutate the motor. A system implementing the method is also described.
Claims18
A method for attenuating switching noise from back electromotive force (EMF) values in a motor controlled by pulse width modulation (PWM) signals provided at a PWM frequency, comprising:
- sampling back EMF values on poles in the motor at a sampling frequency that is at least two times greater than the PWM frequency;
- selecting from the back EMF values any two consecutive readings that have a change in sign of the rate of change in current on the poles between the any two consecutive readings;
- and
- during a first state, utilizing the two consecutive readings to commutate the motor, wherein the back EMF values are sampled from a sensing coil in the motor that is not being driven by the PWM signals when two poles of the motor are being driven by the PWM signals.
A system for attenuating switching noise from back electromotive force (EMF) values in a motor controlled by pulse width modulation (PWM) signals provided at a PWM frequency, comprising:
- a sense circuit for sampling back EMF values on poles in the motor from a sensing coil in the motor that is not being driven by the PWM signals when two poles of the motor are being driven by the PWM signals, the back EMF values being at a sampling frequency that is at least two times greater than the PWM frequency;
- a selection module for identifying from the back EMF values any two consecutive readings that have a change in sign of the rate of change in current on the poles between the two consecutive readings;
- a filtering module for filtering the two consecutive readings to remove switching noise to produce filtered values;
- and
- a motor controller for determining a state of the motor to determine whether to use the two consecutives readings to commutate the motor or to use the filtered values to commutate the motor.
Dependencies are inferred from the claim text.