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METHOD AND APPARATUS FOR DYNAMICALLY CONTROLLING ROLL, TWIST and PITCH OF A READ/WRITE HEAD IN A DISK STORAGE DEVICE

IP.com Disclosure Number: IPCOM000020348D
Original Publication Date: 2003-Nov-14
Included in the Prior Art Database: 2003-Nov-14
Document File: 9 page(s) / 57K

Publishing Venue

IBM

Abstract

Disclosed are a method and apparatus for dynamically controlling roll, twist and pitch of a read/write head in a rotating disk storage device comprising a suspension system where the read/write head is mounted on a slider that is attached to the suspension system, preferably by means of a gimbal mounting.

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  METHOD AND APPARATUS FOR DYNAMICALLY CONTROLLING ROLL, TWIST and PITCH OF A READ/WRITE HEAD IN A DISK STORAGE DEVICE

Magnetic disk storage devices known in the prior art comprise an air-bearing head slider on which an electromagnetic transducer is mounted. The slider itself is mounted on the distal end of a so-called suspension arm system which essentially functions as a load beam and which comprises a rigid portion, in most cases a base plate, and an elastic portion, the mentioned load beam.

    The base plate is configured to attach the load beam to an actuator of a disk drive. The elastic portion generates a load for urging the slider towards a recording medium, so that the slider is pushed to the recording medium with a certain necessary load. A gimbal mechanically isolates the slider from the other parts of the suspension arm system facilitating the slider to roll and pitch about a pivot. A static attitude is defined in general as the position of the head assembly at rest, i.e. without a rotating medium.

    When the recording medium, for example a magnetic recording disk, is rotating, a load exerted on the slider and a flying force exerted on a flying surface of the slider due to an air flow are balanced to each other, so that the slider is flying above the recording medium with a very fine gap, the so-called "flying height". The head assembly reaches a so-called dynamic attitude, this means a defined position relative to the media's surface.

    The flying height of a slider carrying a magnetic read/write head above a rotating magnetic hard disk currently is in the range of nanometer and will likely decrease in the future. In known hard disk devices the flying height is substantially determined by the particular design of an air bearing surface of the slider and by the static attitude of the head gimbal assembly (HGA).

    The track width of written information on a disk surface is already less than a micrometer, with a further substantial decrease expected in the future. Controlling the correct position of the slider above the track thus becomes ever more sensitive to fluctuations in slider orientation relative to the disk, since small amounts of misorientation cause severe signal degradation during read/write operations of an underlying disk storage.

    However, ideally, disks would be absolutely flat and the dynamic attitude would be constant in all cases. But in practice, disks suffer from surface imperfections and vibrations, known as "disk flutter".

    Thereupon, sliders are mounted with manufacturing tolerances onto the suspension system which, in turn, in most cases is non-ideally fixed to a mounting device. Examples of such errors are tilted/twisted sliders on the suspension. This results in static roll and pitch torque. Another possible source of slider-disk misalignment is an insufficient parallelism between mounting plane of the head stack assembly and the disks, for instance due to an imperfect disk drive assembly. In addition, load...