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Proceedings Paper

Main axis control of the Large Millimeter Telescope
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Paper Abstract

The initial operation of the Large Millimeter Telescope/Gran Telescopio Milimetrico (LMT) main axis servo system showed promising results, with subarcsecond RMS performance even without a complete drive system. Since that time, there has been substantial progress in the commissioning of the system. For example, the alignment and grouting of the elevation axis gear rims is completed and all motors have been installed. This has allowed full-speed operation in both axes and has enabled some tuning of the servo system. The digital control architecture of the LMT allows direct measurement of the frequency response function of the system. Further, it allows the rate loop and position loop to be configured either as a classical proportional-integral (PI) controller or as a model-based (e.g., LQG) state-space controller. Finally, the architecture permits additional special-purpose control features to be implemented, including friction compensation and lookup table feedforward to reduce nonlinear effects. The measured FRF results are presented, and have been applied to tuning of the control system, with a resulting improvement in performance. Results are presented for the LMT main axis slewing, pointing, and tracking performance. Additionally, results are presented from initial experiments in applying lookup table feedforward to improve performance in crossing joints in the azimuth track.

Paper Details

Date Published: 4 August 2010
PDF: 8 pages
Proc. SPIE 7733, Ground-based and Airborne Telescopes III, 77332M (4 August 2010); doi: 10.1117/12.857501
Show Author Affiliations
David R. Smith, MERLAB, P.C. (United States)
Kamal Souccar, Large Millimeter Telescope, Univ. of Massachusetts Amherst (United States)

Published in SPIE Proceedings Vol. 7733:
Ground-based and Airborne Telescopes III
Larry M. Stepp; Roberto Gilmozzi; Helen J. Hall, Editor(s)

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