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Quadrature Servo Generation With Side-By-Side Data Heads

IP.com Disclosure Number: IPCOM000046511D
Original Publication Date: 1983-Jul-01
Included in the Prior Art Database: 2005-Feb-07
Document File: 2 page(s) / 44K

Publishing Venue

IBM

Related People

Jones, DM: AUTHOR

Abstract

Quadrature servo patterns were developed for disk file products to provide a more linear position error signal (PES) in the extreme offtrack and track crossing areas. Most direct-access storage device sector servo systems have the servo head track follow between two "Normal" servo tracks, and use a variety of methods to gain position information from those two tracks. As seen in Fig. 1, existing quadrature schemes use fields which are shifted 1/2 track from the normal fields. As the servo head moves radially, it starts moving across two adjacent quadrature tracks which allow it to develop a quadrature PES while the normal PES starts to degenerate.

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Quadrature Servo Generation With Side-By-Side Data Heads

Quadrature servo patterns were developed for disk file products to provide a more linear position error signal (PES) in the extreme offtrack and track crossing areas. Most direct-access storage device sector servo systems have the servo head track follow between two "Normal" servo tracks, and use a variety of methods to gain position information from those two tracks. As seen in Fig. 1, existing quadrature schemes use fields which are shifted 1/2 track from the normal fields. As the servo head moves radially, it starts moving across two adjacent quadrature tracks which allow it to develop a quadrature PES while the normal PES starts to degenerate.

Acquiring quadrature information by this method, however, means twice as many servo tracks as data tracks must be written. The addition of the quadrature capability also means twice as much servo information must be written linearly along the track compared to Normal- only PES schemes, with the resulting loss in data storage capability.

A solution to these disadvantages can be found by using sliders with dual read/write elements. Though sliders having dual elements have been proposed before, their use was intended for continuous servo systems. Under this scheme, one element would be a servo head element which would track follow on buried servo information written uniformly around the data disk. The other head element was proposed to be used only for reading out wr...