Browse Prior Art Database

Stepping Motor Head Positioning

IP.com Disclosure Number: IPCOM000087045D
Original Publication Date: 1976-Dec-01
Included in the Prior Art Database: 2005-Mar-03
Document File: 2 page(s) / 35K

Publishing Venue

IBM

Related People

Janssen, DM: AUTHOR

Abstract

Disk storage apparatus usually employs a head H for signal recording and reading operations. Head H is usually supported on a carriage enabling radial movements across the surface of the disk for accessing one of a plurality of record tracks. In low-cost disk apparatus, it is desired to have a low-cost, but accurate, head-positioning mechanism.

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Stepping Motor Head Positioning

Disk storage apparatus usually employs a head H for signal recording and reading operations. Head H is usually supported on a carriage enabling radial movements across the surface of the disk for accessing one of a plurality of record tracks. In low-cost disk apparatus, it is desired to have a low-cost, but accurate, head-positioning mechanism.

This goal can be achieved by using a differential drive having a pair of stepping motors A and B, which, respectively and selectively, drive drive-pulleys A' and B' in both senses of rotation. Both pulleys A' and B' are gearingly engaged to a differential drive mechanism having an output pulley C differentially coupled to drive pulleys A' and B'.

Drive pulley A' is smaller in diameter than drive pulley B'. If both stepping motors A and B step in the same direction, the angular output of output pulley C is related to the sum of the angular rotations of A' and B'. The angular rotation is equal to the equation (D1 alpha + D2 beta) divided by (2 x D3). Wherein D1 is the diameter of A', D2 is the diameter of B', and D3 is the diameter of C. Alpha and beta are the angular displacements of A' and B'; i.e., Beta is a negative of alpha.

In stepping from track to track motors A and B are stepped together in the same direction. For track-following adjustments, motors A and B are stepped in opposite directions or only one motor is stepped at a time. Output pulley C, in turn, drives an endless belt which...