Browse Prior Art Database

Velocity Control Systems

IP.com Disclosure Number: IPCOM000078834D
Original Publication Date: 1973-Mar-01
Included in the Prior Art Database: 2005-Feb-26
Document File: 2 page(s) / 46K

Publishing Venue

IBM

Related People

Ottesen, HH: AUTHOR

Abstract

In magnetic tape or other member transports, velocity control is an important factor for reliable operation. By using appropriate velocity control circuits, a constant rate of the data signals read from magnetic media through read circuits is provided. Accordingly, a data detector can more reliably detect the data because it does not then have to track velocity, i.e., frequency variations in a readback signal.

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Velocity Control Systems

In magnetic tape or other member transports, velocity control is an important factor for reliable operation. By using appropriate velocity control circuits, a constant rate of the data signals read from magnetic media through read circuits is provided. Accordingly, a data detector can more reliably detect the data because it does not then have to track velocity, i.e., frequency variations in a readback signal.

Read circuits supply either data or a clock tone to the FM discriminator for detecting velocity. The FM discriminator may be constructed as shown, or may use any known radio or video techniques for detecting whether or not the frequency of the readback signal is such to provide a desired constant-data rate. The FM discriminator employed in the present illustration uses two off-frequency narrow-band filter~, one being tuned to f0 and the second being tuned to f0 + Delta f. The frequency response curves show the overlapping tails of the signal response of these two filters. The desired velocity V0 occurs at the intersection of the overlap of the two filter frequency response curves. The output of the filters is supplied to a compare circuit which supplies the error signal to motor control, for adjusting the velocity of a capstan driving the media. It should be noted that motor control responds to a negative signal to adjust the velocity downward toward V0, and to a positive signal to adjust it upward toward V0.

When recording on the media without a prerecorded tone or data signal, velocity can be kept constant by moving the switch to the W position. Tachometer signals from motor control are supplied through a multiplier to equal the frequency of the control tone, or of the fundamental of the consta...