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US 5,854,877 AGranted
Economical wide range speed control system
AssigneeSeagate Technology LLC
InventorMartyn A. Lewis
Life of this patent
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Abstract
A speed control system is disclosed wherein a brushless DC motor and a magneto resistive encoder are able to rotate a motor at arbitrarily low speeds. The motor is able to rotate at low speeds by having a filtered signal generated by an encoder applied to its inputs. The encoder is coupled to a series of filters which remove DC level and harmonic distortions from the resulting encoder signal. These filtered signals are then applied to the motor to control motor rotation speed.
Claims8
A speed control system, comprising:
- a signal source for producing a modulation frequency signal;
- an encoder having a moveable member operatively connected to a device whose speed is to be controlled, said encoder coupled to said signal source, said encoder including means for converting said modulation frequency signal into a phase variable signal having a phase which is varied as a function of the position of said moveable member;
- a reference frequency signal generator coupled to said modulation frequency signal source for generating a variable reference frequency signal;
- a comparator operatively connected to said modulation frequency signal and said reference frequency signal for generating an error signal;
- and
- a plurality of filters in communication with said encoder, each of said plurality of filters including a notch filter operative to remove DC and frequency based distortions from said error signal, said plurality of filters providing a control signal used to control said device at low speeds.
3 more elements
A speed control system, comprising:
- a modulation signal source for producing a modulation frequency signal;
- a motor having a shaft, said motor being coupled to said modulation signal source;
- an encoder coupled to said motor, said encoder generating a phase variable signal having a phase which is varied as a function of said motor shaft position;
- a reference signal generator coupled to said modulation signal source, said reference signal generator operative to produce a variable reference frequency signal which may differ in frequency or phase from said modulation frequency signal;
- a comparator coupled to said modulation signal source and said reference signal generator, said comparator generating an error signal based on any difference between said modulation signal and said reference signal;
- and
- a series of digital filters, coupled to said comparator, each respective one of said series of filters including a neural network for removing frequency distortions present in said error signal and providing a central signal operative to control said motor at low speeds.
4 more elements
Dependencies are inferred from the claim text.