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Distributed Force Control of Deformable Mirrors

MacMynowski, Douglas G. and Heimsten, Rikard and Andersen, Torben (2011) Distributed Force Control of Deformable Mirrors. European Journal of Control, 17 (3). pp. 249-260. ISSN 0947-3580. https://resolver.caltech.edu/CaltechAUTHORS:20110804-102505616

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Abstract

Large (>1m) deformable mirrors are attractive for adaptive optics on ground-based telescopes; the mirrors typically have hundreds or thousands of actuators. The use of force actuators instead of position actuators has the potential to significantly reduce total system cost. However, the use of force actuators results in many lightly-damped structural resonances within the desired bandwidth of the control system. We present a robust control approach for this problem and demonstrate its performance in simulation. First, we demonstrate that high-bandwidth active damping using velocity feedback from mirror sensors that are not quite collocated with the actuators can be robustly implemented, because at sufficiently high frequencies the structural dynamics enter an “acoustic” limit, where the half power bandwidth of a mode exceeds the modal spacing. This is important, because the system can be made less expensive using sensors placed in between actuators rather than collocated with each actuator. Introduction of active damping leads to a much easier problem for subsequent position control. It is known that a position control system in which each of the actuators is controlled using feedback from a collocated sensor can be made robustly stable. However, the resulting performance at high spatial frequencies is poor because there is no shared information between neighbouring actuators. In contrast, global control gives excellent performance but lacks robustness to model uncertainty. We introduce an innovative local control approach, which significantly improves the high spatial frequency performance without the robustness challenges associated with a global control approach. The overall approach is demonstrated to provide excellent command response suitable for an adaptive optics outer loop.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.3166/ejc.17.249-260 DOIArticle
http://ejc.e-revues.com/article.jsp?articleId=16335PublisherArticle
ORCID:
AuthorORCID
MacMynowski, Douglas G.0000-0003-1987-9417
Additional Information:© 2011 EUCA. Received November 30 2009; Accepted September 30 2010.
Subject Keywords:Adaptive optics, deformable mirror, distributed control, active damping, local control
Issue or Number:3
Record Number:CaltechAUTHORS:20110804-102505616
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20110804-102505616
Official Citation:Distributed Force Control of Deformable Mirrorsg D.MACMYNOWSKI, .HEIMSTEN, .ANDERSEN - pp.249-260
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:24677
Collection:CaltechAUTHORS
Deposited By: Ruth Sustaita
Deposited On:04 Aug 2011 17:54
Last Modified:03 Oct 2019 02:58

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