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High Speed Search and Step Distance on a Web Wrapped Capstan

IP.com Disclosure Number: IPCOM000085603D
Original Publication Date: 1976-May-01
Included in the Prior Art Database: 2005-Mar-02
Document File: 2 page(s) / 49K

Publishing Venue

IBM

Related People

Arter, NK: AUTHOR [+4]

Abstract

The device as schematically shown in the diagram provides a method of obtaining a constant fixed length step distance on tape in a magnetic tape drive, whose capstan diameter varies as the tape builds up on it and adjusts to step after a search.

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High Speed Search and Step Distance on a Web Wrapped Capstan

The device as schematically shown in the diagram provides a method of obtaining a constant fixed length step distance on tape in a magnetic tape drive, whose capstan diameter varies as the tape builds up on it and adjusts to step after a search.

The control system 10 is comprised of a basic control loop which utilizes move counter 12 which is updated with a proper count to advance capstan 14, upon which magnetic media 16 is wrapped to the next step position. The count from move counter 12 is converted by digital-to-analog converter 18 and amplified by power amplifier 20, after some compensation is applied to move capstan 14 by motor 22. Digital tachometer 24 decrements the count in move counter 12 as capstan 14 nears the desired stop position.

During normal stepping operation, a step command on terminal 24 triggers move counter 12 to accept a count from move distance generator (MDC) 26. This count is then modified by a servo error read from the tape 16 after it has been limited to a maximum of +/- 3 bits by limited magnitude control 28. For example, if the servo information indicates the position of tape 16 is short by 2 bits, the next forward step will be made longer by 2 bits. The count is also modified by the return signal from tachometer 24 so that step distance will self- correct small errors in the capstan position control loops.

At the end of a step servo, data is again read from the tape 16 and this data is u...