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Economical wide range speed control system

  • US 5,642,461 A
  • Filed: 11/14/1994
  • Issued: 06/24/1997
  • Est. Priority Date: 11/14/1994
  • Status: Expired due to Term
First Claim
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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.

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