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Rotary Positioning with Linear Positioner

IP.com Disclosure Number: IPCOM000109209D
Original Publication Date: 1992-Aug-01
Included in the Prior Art Database: 2005-Mar-23
Document File: 2 page(s) / 65K

Publishing Venue

IBM

Related People

Suzuki, H: AUTHOR [+2]

Abstract

Disclosed is a technique for rotary positioning with a linear positioner. This technique is applicable to devices which require accurate rotary positioning.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 89% of the total text.

Rotary Positioning with Linear Positioner

       Disclosed is a technique for rotary positioning with a
linear positioner.  This technique is applicable to devices which
require accurate rotary positioning.

      Gap control servo system is the key function in this technique
which is composed of non-contact position sensor (capacitance probe
shown as an example) and motor of the device as a driver.

      The key technique of this article is the shape of the cam which
is a part of the rod in Fig. 1.  The cam must always face a
capacitance probe with a right angle (90 degrees) during the whole
stroke of the linear positioner in order to keep the gap between the
probe and the cam a constant length.

      If the cam surface is shaped as an arc drawn by radius DA, the
capacitance probe always faces the cam with right angle (Point E is
the cross of A'D and the circle by radius DA) because E' is on the
line AC when DA moved to D'A' as shown in Fig. 2.  Two kinds of
compensation are required on this technique.  First, point D moves to
D' through arc DD' by radius OD instead of straight line DD';
therefore, the cam surface is slightly out of right angle to the
capacitance probe.  This will cause the error of the gap length in
the gap control servo system.  Secondly, the capacitance probe moves
straight against the head moving rotary.  Thus, track pitch must be
compensated according to the head's track pitch.

      The magnitude of these errors can be...