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Proceedings Paper

Adaptive periodic error correction for Heidenhain tape encoders
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Paper Abstract

Heidenhain position tape encoders are in use on almost all modern telescopes with excellent results. Performance of these systems can be limited by minor mechanical misalignments between the tape and read head causing errors at the grating period. The first and second harmonics of the measured signal are the dominant errors, and have a varying frequency dependant on axis rate. When the error spectrum is within the mount servo bandwidth it results in periodic telescope pointing jitter. This paper will describe an adaptive error correction using elliptic interpolation of the raw signals, based on the well known compensation technique developed by Heydemann [1]. The approach allows the compensation to track in real time with no need of a large static look-up table, or frequent calibrations. This paper also presents the results obtained after applying this approach on data measured on the SOAR telescope.

Paper Details

Date Published: 10 July 2008
PDF: 8 pages
Proc. SPIE 7012, Ground-based and Airborne Telescopes II, 70123N (10 July 2008); doi: 10.1117/12.787462
Show Author Affiliations
Michael Warner, Cerro Tololo Inter-American Observatory (Chile)
Victor Krabbendam, LSST Telescope Project (United States)
German Schumacher, Cerro Tololo Inter-American Observatory (Chile)

Published in SPIE Proceedings Vol. 7012:
Ground-based and Airborne Telescopes II
Larry M. Stepp; Roberto Gilmozzi, Editor(s)

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