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Servo design and analysis for the Thirty Meter Telescope primary mirror actuators

Thompson, Peter M. and MacMynowski, Douglas G. and Regehr, Martin W. and Colavita, M. Mark and Sirota, Mark J. (2010) Servo design and analysis for the Thirty Meter Telescope primary mirror actuators. In: Ground-based and Airborne Telescopes III. Proceedings of SPIE. No.7733. Society of Photo-Optical Instrumentation Engineers (SPIE) , Bellingham, WA, Art. No. 77332F. ISBN 978-0-81948-223-5. https://resolver.caltech.edu/CaltechAUTHORS:20161108-074211133

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Abstract

The Thirty Meter Telescope has 492 primary mirror segments, each incorporated into a Primary Segment Assembly (PSA), each of which in turn has three actuators that control piston, tip, and tilt, for a total of 1476 actuators. Each actuator has a servo loop that controls small motions (nanometers) and large motions (millimeters). Candidate actuators were designed and tested that fall into the categories of "hard" and "soft," depending on the offload spring stiffness relative to the PSA structural stiffness. Dynamics models for each type of actuator are presented, which respectively use piezo-electric transducers and voice coils. Servo design and analysis are presented that include assessments of stability, performance, robustness, and control structure interaction. The analysis is presented for a single PSA on a rigid base, and then using Zernike approximations the analysis is repeated for 492 mirror segments on a flexible mirror cell. Servo requirements include low-frequency stiffness, needed for wind rejection; reduced control structure interaction, specified by a bound on the sensitivity function; and mid-frequency damping, needed to reduce vibration transmission. The last of these requirements, vibration reduction, was found to be an important distinguishing characteristic for actuator selection. Hard actuators have little inherent damping, which is improved using PZT shunt circuits and force feedback, but still these improvements were found to result in less damping than is provided by the soft actuator. Results of the servo analysis were used for an actuator down-select study.


Item Type:Book Section
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1117/12.857371DOIArticle
http://proceedings.spiedigitallibrary.org/proceeding.aspx?articleid=750369PublisherArticle
ORCID:
AuthorORCID
MacMynowski, Douglas G.0000-0003-1987-9417
Additional Information:© 2010 SPIE The International Society for Optical Engineering. The TMT Project gratefully acknowledges the contribution of the following actuator manufactures: The Pilot Group for the Piezo Pump Actuator (inquiries@the-pilot-group.com), Marjan Research (mvjean@marjanresearch.com) for the voice-coil soft actuators, and the Jet Propulsion Laboratory (www.jpl.nasa.gov) for the CT actuator. The work described in this paper was carried out in part at the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration. The authors wish to thank the Thirty Meter Telescope Observatory Corporation for funding this work. The TMT Project gratefully acknowledges the support of the TMT partner institutions. They are the Association of Canadian Universities for Research in Astronomy (ACURA), the California Institute of Technology and the University of California. 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 National Research Council of Canada, the Natural Sciences and Engineering Research Council of Canada, the British Columbia Knowledge Development Fund, the Association of Universities for Research in Astronomy (AURA) and the U.S. National Science Foundation.
Group:Thirty Meter Telescope
Funders:
Funding AgencyGrant Number
NASA/JPL/CaltechUNSPECIFIED
Thirty Meter Telescope Observatory CorporationUNSPECIFIED
Association of Canadian Universities for Research in Astronomy (ACURA)UNSPECIFIED
CaltechUNSPECIFIED
University of CaliforniaUNSPECIFIED
Gordon and Betty Moore FoundationUNSPECIFIED
Canada Foundation for InnovationUNSPECIFIED
Ontario Ministry of Research and InnovationUNSPECIFIED
National Research Council of CanadaUNSPECIFIED
Natural Sciences and Engineering Research Council of Canada (NSERC)UNSPECIFIED
British Columbia Knowledge Development FundUNSPECIFIED
Association of Universities for Research in Astronomy (AURA)UNSPECIFIED
NSFUNSPECIFIED
Subject Keywords:Extremely large telescopes, Primary mirror control system, Dynamic models, Control systems
Series Name:Proceedings of SPIE
Issue or Number:7733
Record Number:CaltechAUTHORS:20161108-074211133
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20161108-074211133
Official Citation:Peter M. Thompson ; Douglas G. MacMynowski ; Martin W. Regehr ; M. Mark Colavita ; Mark J. Sirota; Servo design and analysis for the Thirty Meter Telescope primary mirror actuators. Proc. SPIE 7733, Ground-based and Airborne Telescopes III, 77332F (August 04, 2010); doi:10.1117/12.857371.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:71796
Collection:CaltechAUTHORS
Deposited By: Ruth Sustaita
Deposited On:08 Nov 2016 17:14
Last Modified:03 Oct 2019 16:11

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