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Actuator Friction and Bias Force Measurement

IP.com Disclosure Number: IPCOM000036924D
Original Publication Date: 1989-Nov-01
Included in the Prior Art Database: 2005-Jan-29
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Grundy, AJ: AUTHOR [+2]

Abstract

In a disk file, a carriage supporting a connecting cable is driven by a linear voice coil actuator. This disclosure gives a technique for the separation of carriage friction from cable bias forces acting along the travel of the actuator. During testing, the force required to move the actuator through its entire travel in both directions is measured, giving two graphs of force against distance from which the friction and bias forces may be separated. This is possible because friction always acts against the direction of motion while cable bias acts in one direction only.

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Actuator Friction and Bias Force Measurement

In a disk file, a carriage supporting a connecting cable is driven by a linear voice coil actuator. This disclosure gives a technique for the separation of carriage friction from cable bias forces acting along the travel of the actuator. During testing, the force required to move the actuator through its entire travel in both directions is measured, giving two graphs of force against distance from which the friction and bias forces may be separated. This is possible because friction always acts against the direction of motion while cable bias acts in one direction only.

Cable bias is derived by numerically averaging the graphs point by point. The friction is extracted by subtracting the graphs pointby-point and dividing by two. As a result, two graphs of force against distance are obtained, one of friction and the other of cable bias.

For testing, the actuator is suspended horizontally to eleminate gravitational forces and the linear proximity probe mounted on a precision slide placed in front of the carriage as a sensor. A servo loop is closed around the actuator such that it maintains a fixed air gap from the sensor; the force is measured from the servo drive applied to the actuator, calculated from the measured servo stiffness, scaled in volts/gram.

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