Importance

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Abstract

A motor control for a printer carriage using a DC motor includes a phase-locked loop speed control circuit having an encoder detecting motor speed, a reference oscillator, a phase comparator for detecting the phase difference between the encoder signal and oscillator output signal, and a switching circuit for voltage to be applied to the motor based upon the phase comparator output. Additionally, the motor control includes a feedback circuit having a low pass filter converting the phase comparator output signal into an analog speed signal, and a differentiating circuit converting the filter output signal into a quasi-acceleration signal. The feedback circuit effects frequency modulation of the reference oscillator using the output signal from the differentiating circuit. A speed setting switch means adjusts the selected rotational speed of the motor by changing the oscillator frequency. A mode selection circuit controls signals from the phase comparator to apply braking by reversal of motor current, and to provide reverse motor operation for shifting the carriage.

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First Claim