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Browse Prior Art Database

Track Following Servo System

IP.com Disclosure Number: IPCOM000085329D
Original Publication Date: 1976-Mar-01
Included in the Prior Art Database: 2005-Mar-02
Document File: 2 page(s) / 29K

Publishing Venue

IBM

Related People

Oswald, RK: AUTHOR

Abstract

A track following servo system for a disk file employs a reference magnetization pattern as shown in part. Pairs of aligned narrow radial bands of reversed magnetization S1 and S2 provide synchronizing information in every servo track. A unique time interval between zero crossings of the signal read back from the bands S1 and S2 provides unambiguous identification of synchronizing information.

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Track Following Servo System

A track following servo system for a disk file employs a reference magnetization pattern as shown in part. Pairs of aligned narrow radial bands of reversed magnetization S1 and S2 provide synchronizing information in every servo track. A unique time interval between zero crossings of the signal read back from the bands S1 and S2 provides unambiguous identification of synchronizing information.

A repeated pattern of broader reversed magnetization pulses A,B,C and D is written between adjacent pairs of synchronizing pulses to provide position reference information. The different contributions of the pulses A,B,C and D to the read-back signal are separated and preserved by gating circuitry, not shown.

The operation of this circuitry is controlled by the output of a phase-locked oscillator synchronized with zero crossings of the read-back signal from pulses S2. Read-back signals from A and B are combined to give a first position error signal and read-back signals from C and D are combined to give a second position error signal in quadrature phase relationship. Quadrature error signals permit the head to be positioned at any radial position but, in practice, the system is designed to follow the boundaries between pulses A and B (head position H1) and the boundaries between pulses C and D (head position H2).

The lines of these boundaries (shown dotted) correspond to the data track centers and the system seeks the respective null points of c...