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Device for controlling rotational speed of motor

  • US 5,130,626 A
  • Filed: 11/29/1990
  • Issued: 07/14/1992
  • Est. Priority Date: 11/30/1989
  • Status: Expired due to Fees
First Claim
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1. A device for controlling the rotational speed of a motor which carries out feedback control of the motor on the basis of a speed difference control value based on the difference between a command speed and rotational speed and a phase difference control value based on the phase difference between a command pulse and a detection pulse, comprising:

  • detection pulse output means for outputting a detection pulse proportional to the rotational speed of the motor;

    command pulse output means for outputting a command pulse proportional to the command speed;

    reference time point setting means for setting a reference time point;

    detection pulse counting means for counting a number of detection pulses outputted;

    period measuring means for measuring the period of the command pulse;

    first time period calculating means for calculating a time period from the reference time point to the time when a newest detection pulse is outputted every time a predetermined number of detection pulses are counted by the detection pulse counting means;

    second time period calculating means for calculating a time period from the reference time point to the time when a command pulse, which is assigned an ordinal number equal to the ordinal number of the newest detection pulse, and which corresponds to the newest detection pulse is outputted on the basis of the total number of pulses counted by the detection pulse counting means in the time period from the reference time point to the time when the newest detection pulse is outputted, and the period of the command pulse measured by the period measuring means;

    phase difference calculating means for calculating the phase difference between the newest detection pulse and the command pulse corresponding thereto on the basis of the time period calculated by the first time period calculating means and the time period calculated by the second time period calculating means and the period of the command pulse; and

    phase difference control value output means for outputting a phase difference control value proportional to the phase difference when the phase difference calculated by the phase difference calculating means is within a predetermined range and continuing to output a control value in a critical state when the phase difference is outside the range.

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