Browse Prior Art Database

Azimuth and Position Detection Method for a Magnetic Read/Write Head

IP.com Disclosure Number: IPCOM000047724D
Original Publication Date: 1983-Dec-01
Included in the Prior Art Database: 2005-Feb-08
Document File: 4 page(s) / 38K

Publishing Venue

IBM

Related People

Baasch, HJ: AUTHOR [+4]

Abstract

In flexible file diskette drives there are three critical axes along or around which the magnetic transducing gap must be aligned. These are: 1. Along a radial axis through the center of rotation of the diskette (radial alignment). 2. Along the axis perpendicular to the radial axis and parallel to the plane of diskette rotation (tangential alignment). 3. Rotationally around an axis mutually perpendicular to the radial and tangential axes (azimuthal alignment). The method developed to detect each of the above alignment modes is to write, on a slightly modified diskette, a precise set of magnetic patterns which, when read back by a head to be aligned, produce error signals proportional to the degree of misalignment. Fig. 1 is a schematic representation of the pattern written on the diskette.

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Azimuth and Position Detection Method for a Magnetic Read/Write Head

In flexible file diskette drives there are three critical axes along or around which the magnetic transducing gap must be aligned. These are: 1. Along a radial axis through the center of rotation of the diskette (radial alignment). 2. Along the axis perpendicular to the radial axis and parallel to the plane of diskette rotation (tangential

alignment). 3. Rotationally around an axis mutually perpendicular to the radial and tangential axes (azimuthal alignment). The method developed to detect each of the above alignment modes is to write, on a slightly modified diskette, a precise set of magnetic patterns which, when read back by a head to be aligned, produce error signals proportional to the degree of misalignment. Fig. 1 is a schematic representation of the pattern written on the diskette. The alignment record is repeated an even number of times (usually several hundred times) around the diskette so that each record has a complement spaced 180OE away. The large number of records of relatively short duration allows the error signals to be averaged over a full revolution of the diskette, thus minimizing the effects of changes in flying height, varying particle concentration and orientation in the media and speed variations in the spinner. The alignment records are written, with Segments 1 and 3 which have zero or substantially equal amounts of azimuth, offset equally and in opposite directions such that they overlap approximately one-half of a track positioned at the desired location of the head to be aligned.

Segments 2 and 4 are written approximately on the desired track center line but with equal and opposite amounts of azimuthal misalignment. The amount of azimuthal misalignment is selected so that the signal from the head to be aligned has maximum sensitivity to slight variations in azimuth, in our case +/- 0 degrees 30'. See the IBM Technical Disclosure Bulletin 20, 1897-1901 (October 1977) for a discussion of the dependency of head signal on azimuth angle. The procedure for writing the alignment diskette and calibrating the alignment tool will be described below. The standards to which the alignment tool is calibrated are two specially designed and precisely inspected head/carriage assemblies. The essential features of this head, as shown in Fig. 2, are the two gap extension surfaces which are coplanar with one pole face of the gap and allow the head/carriage azimuth to be measured within 0OE degrees 0'20". The head is made up of six components, (a) a body 5 which contains one face of the gap 6 and the gap extension surfaces 8, 9 and which is made of a soft magnetic material, (b) a core 11 which has a width substantially equal to the core width in the heads to be aligned and which is also a soft magnetic material, and (c) outriggers 12, 13 which provide support for the core and, along with the body, form the air bearing surface and which are made of a nonmag...