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Minimizing motor cogging and vibration for the Thirty Meter Telescope

Thompson, Peter M. and MacMartin, Douglas G. and Thompson, Hugh A. and Sirota, Mark J. (2017) Minimizing motor cogging and vibration for the Thirty Meter Telescope. In: 2017 IEEE Aerospace Conference. IEEE , Piscataway, NJ, pp. 1-15. ISBN 978-1-5090-1613-6. http://resolver.caltech.edu/CaltechAUTHORS:20170614-164715990

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Abstract

The Thirty Meter Telescope (TMT) needs to maintain precise positioning of the optical elements to deliver unprecedented image quality. Any vibration from observatory sources must therefore be minimized; model-based analysis leads to maximum allowable forces from any individual source typically of order a Newton or less in the most sensitive frequency band. Careful attention throughout the design process is needed to ensure that these challenging requirements are satisfied. We focus here in particular on cogging forces from the azimuth motor drive. Each motor yields periodic tangential and vertical forces of order 100's of Newtons, with higher harmonics of the waveform potentially exciting telescope structural resonances. There are 56 drive motors, and appropriate phasing between them can ideally cancel most of the net torque or net vertical force. However, the moment created between non-collocated forces still produces image motion even if the net force cancels, and further, small errors in forcer positioning result in imperfect cancellation. We provide a general methodology for estimating total cogging forces and then present an example of the expected TMT performance impact from motor cogging placed in context with the larger challenge of demanding vibration requirement.


Item Type:Book Section
Related URLs:
URLURL TypeDescription
https://doi.org/10.1109/AERO.2017.7943747DOIArticle
http://ieeexplore.ieee.org/document/7943747/PublisherArticle
ORCID:
AuthorORCID
MacMartin, Douglas G.0000-0003-1987-9417
Additional Information:© 2017 IEEE. The TMT Project gratefully acknowledges the support of the TMT collaborating institutions. They are the California Institute of Technology, the University of California, the National Astronomical Observatory of Japan, the National Astronomical Observatories of China and their consortium partners, the Department of Science and Technology of India and their supported institutes, and the National Research Council of Canada. This work was supported as well by the Gordon and Betty Moore Foundation, the Canada Foundation for Innovation, the Ontario Ministry of Research and Innovation, the Natural Sciences and Engineering Research Council of Canada, the British Columbia Knowledge Development Fund, the Association of Canadian Universities for Research in Astronomy (ACURA), the Association of Universities for Research in Astronomy (AURA), the U.S. National Science Foundation, the National Institutes of Natural Sciences of Japan, and the Department of Atomic Energy of India.
Group:Thirty Meter Telescope
Funders:
Funding AgencyGrant Number
Gordon and Betty Moore FoundationUNSPECIFIED
Canada Foundation for InnovationUNSPECIFIED
Ontario Ministry of Research and InnovationUNSPECIFIED
Natural Sciences and Engineering Research Council of Canada (NSERC)UNSPECIFIED
British Columbia Knowledge Development FundUNSPECIFIED
Association of Canadian Universities for Research in Astronomy (ACURA)UNSPECIFIED
Association of Universities for Research in Astronomy (AURA)UNSPECIFIED
NSFUNSPECIFIED
National Institutes of Natural Sciences of JapanUNSPECIFIED
Department of Atomic Energy (India)UNSPECIFIED
Record Number:CaltechAUTHORS:20170614-164715990
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20170614-164715990
Official Citation:P. M. Thompson, D. G. MacMartin, H. A. Thompson and M. J. Sirota, "Minimizing motor cogging and vibration for the Thirty Meter Telescope," 2017 IEEE Aerospace Conference, Big Sky, MT, USA, 2017, pp. 1-15. doi: 10.1109/AERO.2017.7943747
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:78225
Collection:CaltechAUTHORS
Deposited By: Kristin Buxton
Deposited On:15 Jun 2017 01:13
Last Modified:02 Jan 2018 15:59

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