Browse Prior Art Database

Detection of Servo Off-Track for Data Integrity

IP.com Disclosure Number: IPCOM000047458D
Original Publication Date: 1983-Nov-01
Included in the Prior Art Database: 2005-Feb-07
Document File: 2 page(s) / 26K

Publishing Venue

IBM

Related People

Mueller, FE: AUTHOR

Abstract

Described here is a technique for use with a servo pattern of the Quadrature type which has a null pattern and a peak pattern at each track center. For illustration, the Quad-Burst servo pattern is shown in the IBM Technical Disclosure Bulletin 21, 804-805 (July, 1978), but the concept could be applied to other patterns. In that publication, the servo head is shown at a track location for which A-B is the track following signal, and C-D is the off-track signal. It is proposed here that a new multiplier be added to provide an off-track detector. It would be gated to demodulate the null pattern - the C burst, in this example. The gate would change according to the track type the servo is following.

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Detection of Servo Off-Track for Data Integrity

Described here is a technique for use with a servo pattern of the Quadrature type which has a null pattern and a peak pattern at each track center. For illustration, the Quad-Burst servo pattern is shown in the IBM Technical Disclosure Bulletin 21, 804-805 (July, 1978), but the concept could be applied to other patterns. In that publication, the servo head is shown at a track location for which A-B is the track following signal, and C-D is the off-track signal. It is proposed here that a new multiplier be added to provide an off-track detector. It would be gated to demodulate the null pattern - the C burst, in this example. The gate would change according to the track type the servo is following. The output of this multiplier would be null over track center, and increase with the same polarity for head motion in either direction. Noise on this signal would be primarily dropouts rather than spikes, thus allowing the signal to be filtered with a relatively wide bandwidth, without false error indication. The extra hardware to detect the null pattern is a redundant detection path which increases data security. Failures of this path can be detected relatively easily as shown below.

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Level detector 1 provides the write inhibit signal that shows that the servo has moved off track. It can be tested with each seek. Level detector 2 shows that the detector or the amplifier has drifted. It could be tested by sum...