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DC Band Servo Drive

IP.com Disclosure Number: IPCOM000109877D
Original Publication Date: 1992-Sep-01
Included in the Prior Art Database: 2005-Mar-24
Document File: 4 page(s) / 116K

Publishing Venue

IBM

Related People

Arnold, RW: AUTHOR [+2]

Abstract

The basic functions of the DC Band Servo Drive are shown broken down into its major parts in Fig. 1. The encoder output 36 is a digital signal whose period represents the band velocity. The signal is compared to the Band Oscillator signal by the phase detector 1. If the band is running at the desired velocity, as set by the Band Oscillator signal, there is no phase difference and no output generated by the phase detector. When the band velocity differs from the Band Oscillator signal, the band is running either too slow or too fast. A polarized signal is then generated by the phase detector. The filter block F1 converts the phase detector signal into a DC voltage which is compared to a fixed frequency triangular wave oscillator.

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DC Band Servo Drive

       The basic functions of the DC Band Servo Drive are shown
broken down into its major parts in Fig. 1.  The encoder output 36 is
a digital signal whose period represents the band velocity.  The
signal is compared to the Band Oscillator signal by the phase
detector 1.  If the band is running at the desired velocity, as set
by the Band Oscillator signal, there is no phase difference and no
output generated by the phase detector.  When the band velocity
differs from the Band Oscillator signal, the band is running either
too slow or too fast.  A polarized signal is then generated by the
phase detector.  The filter block F1 converts the phase detector
signal into a DC voltage which is compared to a fixed frequency
triangular wave oscillator.  As the filter voltage level changes, due
to band velocity variations, the comparator 33 output changes the
percentage of motor drive 34.  This is known as pulse width
modulation.  If the band velocity is too low, the motor drive pulse
width is increased to speed up the band.  When the band velocity is
too fast, the pulse width is decreased, slowing down the band.  The
filter design (F1, F2, F3, F4, F5) combines such that it stabilizes
the control loop with maximum bandwidth and phase margin to provide
improved compliance and dynamic performance.

      The Band Oscillator signal is a square-wave reference that
dictates the desired band velocity.  The - band reference signal
(Fig. 1B), or encoder output, represents the actual band velocity.
Both signals are inputted to the phase detector 1.  The output of the
phase detector represents the phase and frequency error between the
two input signals.  The digital outputs of the phase detec...