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Proceedings Paper

Main axes servo systems of the VLT
Author(s): Martin Ravensbergen
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Paper Abstract

The altitude and azimuth axes of the VLT telescopes will be controlled by special designed servo controllers. These controllers are designed to minimize the effect of disturbances. The properties of all elements of these servo systems: mechanical system, motors, amplifiers, tachometer, encoder and finally the servo controller itself will be presented. Aspects like sensor noise, hysteresis, friction and bandwidth limits are described and the effect of each of them on the servo performance is evaluated. A systematic analysis of the effect of external disturbances to the servo system, mainly the wind, is included. The frequency spectrum of the wind that can be expected in the VLT enclosure is compared with disturbance sensitivity of the servo system. This analysis provides the power spectral density of the axial rotation. The reduction of this rotation with an autoguider and/or field stabilization (a fast servo system, which includes a tip/tilt of the secondary mirror) can then be judged. The data for the analysis has been derived from the present status of the VLT main structure design. The servo elements as described above are now in a well-defined state.

Paper Details

Date Published: 1 June 1994
PDF: 9 pages
Proc. SPIE 2199, Advanced Technology Optical Telescopes V, (1 June 1994); doi: 10.1117/12.176158
Show Author Affiliations
Martin Ravensbergen, European Southern Observatory (Germany)

Published in SPIE Proceedings Vol. 2199:
Advanced Technology Optical Telescopes V
Larry M. Stepp, Editor(s)

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