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Gain Adjustment of Data Surface Embedded Servo

IP.com Disclosure Number: IPCOM000036580D
Original Publication Date: 1989-Oct-01
Included in the Prior Art Database: 2005-Jan-29
Document File: 2 page(s) / 49K

Publishing Venue

IBM

Related People

Arai, K: AUTHOR [+2]

Abstract

Described is a method for having compensation values for a uniform servo open-loop gain, head by head, for an embedded servo system of hard disk drives. It is to select gain value for each head which is used for a positioning servo.

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Gain Adjustment of Data Surface Embedded Servo

Described is a method for having compensation values for a uniform servo open-loop gain, head by head, for an embedded servo system of hard disk drives. It is to select gain value for each head which is used for a positioning servo.

Since the data surface embedded servo uses each data head to get servo information, the track width varies from one head to the other. This leads to a difference of servo gain and, hence, a difference of servo characteristics. The difference of the gain due to the head track width tolerance is described in the figure.

As shown in the figure a head with a narrower track width has a higher servo gain.

Also for drives with higher tracks per inch (or with more tracks), the tolerance of head track width allows relatively greater tolerance of servo gain, because the absolute tolerance remains the same due to the restraint of cost. Thus, a large gain margin becomes necessary for stability of the servo system.

To eliminate this difficulty, the proposed method is to adjust the open loop servo gain, head by head, by having gain compensation values inside the drive.

By adopting this method, the servo characteristics become more insensitive to the difference of gain produced by each head.

The gain parameters for each head can be measured during the manufacturing process and can be stored into the media of the drive itself, which are loaded every time the drive is powered on and used thereafter for he...