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Proceedings Paper

Direct-drive digitally commutated filter wheel positioning system for cryogenic optical applications
Author(s): Kenneth R. Lorell; Jean-Noel Aubrun; Walter G. Opyd; Allen D. Wood
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Paper Abstract

A control system is presented for precise and rapid positioning of spectral filters in the multispectral infrared optical system used for the MUlti-Spectral Infrared Camera (MUSIC). A hybrid system employing a stepper motor as a direct-drive brushless servomotor presents an ideal solution, applying high torque at low speed for the optimum response as limited by available torque. As the end of the repositioning transient is approached, closed-loop proportional control of torque provides quick settling to a positioning accuracy of 0.02 degrees. The use of a stepper motor avoids the problems of a brushed DC servomotor, such as brush and bearing failures at high speeds in a cryogenic vacuum, and backlash in reduction gears. The analog servo loop with commutation hardware to optimally switch the current to the stepper motor windings, avoids problems typical of stepper motors, such as limited positioning precision and high power dissipation while holding position.

Paper Details

Date Published: 21 January 1993
PDF: 9 pages
Proc. SPIE 1765, Cryogenic Optical Systems and Instruments V, (21 January 1993); doi: 10.1117/12.140883
Show Author Affiliations
Kenneth R. Lorell, Lockheed Palo Alto Research Lab. (United States)
Jean-Noel Aubrun, Lockheed Palo Alto Research Lab. (United States)
Walter G. Opyd, Lockheed Palo Alto Research Lab. (United States)
Allen D. Wood, Lockheed Palo Alto Research Lab. (United States)

Published in SPIE Proceedings Vol. 1765:
Cryogenic Optical Systems and Instruments V
Ramsey K. Melugin, Editor(s)

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