Economical wide range speed control system
First Claim
Patent Images
1. 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 which may differ in frequency or phase from said modulation frequency signal;
a comparator, coupled between said signal source and said reference frequency signal generator, operative to compare said modulation frequency signal and said reference frequency signal, said comparator generating an error signal as a function of any phase difference between said modulation frequency signal and said reference frequency signal;
a first filter operative to remove distortions at the carrier frequency of said error signal;
a second filter operative to remove distortions at the third frequency harmonic and higher order frequency harmonics of said error signal;
a third filter operative to remove dc distortions produced by said encoder; and
a fourth filter operative to remove viscous effects of said error signal.
18 Assignments
0 Petitions
Accused Products
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.
-
Citations
7 Claims
-
1. 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 which may differ in frequency or phase from said modulation frequency signal; a comparator, coupled between said signal source and said reference frequency signal generator, operative to compare said modulation frequency signal and said reference frequency signal, said comparator generating an error signal as a function of any phase difference between said modulation frequency signal and said reference frequency signal; a first filter operative to remove distortions at the carrier frequency of said error signal; a second filter operative to remove distortions at the third frequency harmonic and higher order frequency harmonics of said error signal; a third filter operative to remove dc distortions produced by said encoder; and a fourth filter operative to remove viscous effects of said error signal. - View Dependent Claims (2, 3, 4, 5, 6)
-
-
7. A speed control system, comprising:
-
a modulation signal source for producing a modulation frequency signal; a brushless dc motor having a shaft, said motor being coupled to said modulation signal source; a magneto resistive encoder coupled to said motor, said encoder generating a phase variable signal having a phase which is varied as a function of 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; a first filter operative to remove distortions at the carrier frequency of said error signal; a second filter operative to remove distortions at harmonics of said error signal frequency; a third filter operative to remove dc distortions produced by said encoder; and a fourth filter operative to remove viscous distortions from said error signal.
-
Specification