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CORRECTED CURRENT INTEGRATION FOR VELOCITY

IP.com Disclosure Number: IPCOM000023977D
Original Publication Date: 1979-Jun-30
Included in the Prior Art Database: 2004-Apr-01
Document File: 2 page(s) / 280K

Publishing Venue

Xerox Disclosure Journal

Abstract

A magnetic transducer used for position information in a disk drive has an inherent distortion as a function of spacing, geometry and design of the primary and secondary ma-etic circuits (windings). More specifically, the flux patterns are not equal or at 90 as seen by the secondary winding(s) for all relative radial locations of the moving and stationary portions of the transducer system. Further, when this

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XEROX DISCLOSURE JOURNAL

CORRECTED CURRENT INTEGRATION FOR VELOCITY
Martin 0, Halfhill

Proposed Classification
U.S. CL 318/608

mt. CL G05b 1/02

VCM

VCM

Volume 4 Number 3 May/3une 1979 343

,~CORRECTED FOR

J ivc~ OFFSET VELOC1TY~KV

A magnetic transducer used for position information in a disk drive has an inherent distortion as a function of spacing, geometry and design of the primary and secondary ma~etic circuits (windings). More specifically, the flux patterns are not equal or at 90 as seen by the secondary winding(s) for all relative radial locations of the moving and stationary portions of the transducer system. Further, when this

non~4ineartransducer signal is differentiated to form a velocity signal for motion

control, the non~.linearity of the magnetic system is enhanced. The result of differentiation is a distorted and incorrect velocity signal whose errors are

significant to the system and limit the speed and bandwidth of the head actuator system.

However, the integral of motor current is proportional to velocity and suffers only from the practical problem of integrating (enhancing) the error in the integration process. A combination of the integral of VCM current corrected by the DC and

low frequency components of the transducer tachometer signal overcomes the problems of both the integral and differentiation processes and results in a smooth velocity signal without the error of integration. A preferred circuit is shown in

Figure 1 which includes a magneti...