E-ELT optomechanics: overview

Cayrel, Marc

doi:10.1117/12.925175

Cited by 29 publications

(9 citation statements)

References 17 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…We incorporate models of electromechanical actuators (voice coils) in our model. The presented modeling approach can be applied to actuators with moving rods attached to the faceplate [48,49] or to actuators with permanent magnets attached to the faceplate [42,50]. The actuator stiffness can be tuned during the design phase, and is provided by an elastic suspension [49] or using some other mechanisms.…”

Section: Damping and Actuator Modelingmentioning

confidence: 99%

Modeling and state-space identification of deformable mirrors

Haber

Verhaegen

2020

Opt. Express

View full text Add to dashboard Cite

To develop high-performance controllers for adaptive optics (AO) systems, it is essential to first derive sufficiently accurate state-space models of deformable mirrors (DMs). However, it is often challenging to develop realistic large-scale finite element (FE) state-space models that take into account the system damping, actuator dynamics, boundary conditions, and multi-physics phenomena affecting the system dynamics. Furthermore, it is challenging to establish a modeling framework capable of the automated and quick derivation of state-space models for different actuator configurations and system geometries. On the other hand, for accurate model-based control and system monitoring, it is often necessary to estimate state-space models from the experimental data. However, this is a challenging problem since the DM dynamics is inherently infinite-dimensional and it is characterized by a large number of eigenmodes and eigenfrequencies. In this paper, we provide modeling and estimation frameworks that address these challenges. We develop an FE state-space model of a faceplate DM that incorporates damping and actuator dynamics. We investigate the frequency and time domain responses for different model parameters. The state-space modeling process is completely automated using the LiveLink for MATLAB toolbox that is incorporated into the COMSOL Multiphysics software package. The developed state-space model is used to generate the estimation data. This data, together with a subspace identification algorithm, is used to estimate reduced-order DM models. We address the model-order selection and model validation problems. The results of this paper provide essential modeling and estimation tools to broad AO and mechatronics scientific communities. The developed Python, MATLAB, and COMSOL Multiphysics codes are available online.There are various types of DM architectures and design concepts used in AO systems. Depending on how the reflective surface is designed, we can distinguish between segmented, faceplate, and membrane DMs [1,7,8]. Due to their widespread usage, in this manuscript, we consider DMs with continuous faceplates. The results can easily be extended to other mirror concepts. A typical continuous faceplate DMs is composed of a thin faceplate that is deformed by spatially distributed actuators placed on its backside.Modeling and control problems for large-scale DMs have been considered in [5,[9][10][11][12][13][14][15][16][17][18]. Distributed control and estimation problems or problems of efficient implementation of control and estimation algorithms for large-scale DMs and AO systems have been considered in [4,[18][19][20][21][22][23]. Before these methods can be used, it is necessary to develop sufficiently accurate DM models. Furthermore, it is preferable that these models are in a state-space form that can be used for the design of advanced model-based control algorithms. Analytical mirror models that are based on the biharmonic plate equation and its modifications have been developed in [7,10,11,24,25]. Howev...

show abstract

Section: Damping and Actuator Modelingmentioning

confidence: 99%

Modeling and state-space identification of deformable mirrors

Haber

Verhaegen

2020

Opt. Express

View full text Add to dashboard Cite

show abstract

“…The range of tolerances for ELT M2 and M3 have been discussed by [5] and [6] and although these numbers could slightly vary from mirror to mirror, we assume the same values also for M4 and M5. The assumption is driven by the comparable size of the mirrors and by the interest of assessing the response to an equal-amplitude perturbation:…”

Section: Elt Tolerances and Distortionmentioning

confidence: 99%

“…A delicate point of the astrometry error budget control strategy in this case is the assessment the level of distortion introduced by this correction from MAORY in comparison with other options internal to the ELT like the modification of the M3 piston. The ELT tertiary mirror in fact is a crucial component of the telescope control strategy and performs a critical function in permitting the telescope to achieve a variable focal length [6]. Also this latter case needs to be studied both for feasibility at a telescope control strategy level and for the additional distortion introduced.…”

Section: Preliminary Astrometric Error Budget and Worst Offendersmentioning

confidence: 99%

Towards an overall astrometric error budget with MICADO-MCAO

Rodeghiero

Pott

Massari

et al. 2017

Proceedings of the Adaptive Optics for Extremely Large Telescopes 5

View full text Add to dashboard Cite

MICADO is the Multi-AO Imaging Camera for Deep Observations, and it will be one of the first light instruments of the Extremely Large Telescope (ELT). Doing high precision multi-object differential astrometry behind ELT is particularly effective given the increased flux and small diffraction limit. Thanks to its robust design with fixed mirrors and a cryogenic environment, MICADO aims to provide 50 µas absolute differential astrometry (measure star-to-star distances in absolute µas units) over a 53" FoV in the range 1.2-2.5 µm. Tackling high precision astrometry over large FoV requires Multi Conjugate Adaptive Optics (MCAO) and an accurate distortion calibration. The MICADO control scheme relies on the separate calibration of the ELT, MAORY and MICADO systematics and distortions, to ensure the best disentanglement and correction of all the contributions. From a system perspective, we are developing an astrometric error budget supported by optical simulations to assess the impact of the main astrometric errors induced by the telescope and its optical tolerances, the MCAO distortions and the opto-mechanical errors between internal optics of ELT, MAORY and MICADO. The development of an overall astrometric error budget will pave the road to an efficient calibration strategy complementing the design of the MICADO calibration unit. At the focus of this work are a number of opto-mechanical error terms which have particular relevance for MICADO astrometry applications, and interface to the MCAO design.

show abstract

“…An off-axis aspheric mirror is a well-established form for largescale telescope mirrors, and many of the recently developed telescopes employ a large number of segmented off-axis aspheric mirrors. Some examples include the Giant Magellan Telescope (GMT), 1,2 the Thirty Meter Telescope (TMT), 3 the European Extremely Large Telescope (EELT), 4 the James Webb Space Telescope (JWST), 5 and the Daniel K. Inouye Solar Telescope. 6 In addition to the radius of curvature R and conic constant K to represent the aspheric surface, each segment mirror requires two additional parameters: (i) the size of the mirror and (ii) the distance from the reference optical axis (ROA) of the aspheric surface to the center of the mirror.…”

Section: Introductionmentioning

confidence: 99%

Methods of defining circular off-axis aspheric mirrors

Han

Lee

2018

J. Astron. Telesc. Instrum. Syst.

View full text Add to dashboard Cite

We investigated the definition for circular off-axis aspheric mirrors (COAMs). The clear opening of the COAM obtained by projecting a circular aperture on the aspheric surface does not form a plane but a curved surface. To solve this problem, we propose to use a plane to cut the aspheric surface to obtain a COAM. The COAM has three characteristics: (i) an elliptical opening; (ii) the major axis of the opening lies on the meridional plane containing the original optical axis of the aspheric surface and the minor axis lies on the sagittal plane perpendicular to the meridian plane; and (iii) it is not deepest at the center of the ellipse. The third characteristic suggests two methods for defining the COAM using a plane: (i) with the center of the elliptical opening as a reference and (ii) with the deepest point of the mirror as a reference. All the formulas required to obtain the desired COAM using the two methods are presented. © The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.

show abstract

E-ELT optomechanics: overview

Cited by 29 publications

References 17 publications

Modeling and state-space identification of deformable mirrors

Modeling and state-space identification of deformable mirrors

Towards an overall astrometric error budget with MICADO-MCAO

Methods of defining circular off-axis aspheric mirrors

Contact Info

Product

Resources

About