Distributed control in adaptive optics: deformable mirror and turbulence modeling

Ellenbroek, Rogier; Verhaegen, Michel; Doelman, Niek; Hamelinck, Roger; Rosielle, Nick; Steinbuch, M Maarten

doi:10.1117/12.671688

Cited by 11 publications

(8 citation statements)

References 14 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…If the mass of the reflective membrane is placed on top, this reduces to approximately 1 kHz. This result is independent of the mirror size; if the mirror 'grows' not only mass is added but also stiffness [3].…”

Section: Actuator Analysismentioning

confidence: 72%

“…It determines the influence function, the local and global resonance frequencies of the mirror and the force needed for a displacement, and thereby the power dissipation. Effects are described in [2,3]. An increase in actuator stiffness will result in a more local influence function and higher resonance frequencies, but also lead to increased actuator forces and power dissipation.…”

Section: Actuator Analysismentioning

confidence: 99%

See 1 more Smart Citation

Actuator tests for a large deformable membrane mirror

et al. 2006

Self Cite

View full text Add to dashboard Cite

In the design of a large adaptive deformable membrane mirror, variable reluctance actuators are used. These consist of a closed magnetic circuit in which a strong permanent magnet provides a static magnetic force on a ferromagnetic core which is suspended in a membrane. By applying a current through the coil which is situated around the magnet, this force is influenced, providing movement of the ferromagnetic core. This movement is transferred via a rod imposing the out-ofplane displacements in the reflective deformable membrane. In the actuator design a match is made between the negative stiffness of the magnet and the positive stiffness of the membrane suspension. If the locality of the influence functions, mirror modes as well as force and power dissipation are taken into account, a resonance frequency of 1500 Hz and an overall stiffness of 1000 N/m for the actuators is needed. The actuators are fabricated and the dynamic response tested in a dedicated setup. The Bode diagram shows a first eigenfrequency of 950 Hz. This is due to a lower magnetic force than expected. A Helmholtz coil setup was designed to measure the differences in a large set of permanent magnets. With the same setup the 2 nd quadrant of the B-H curve is reconstructed by stacking of the magnets and using the demagnetization factor. It is shown that the values for H c and B r of the magnets are indeed lower than the values used for the initial design. New actuators, with increased magnet thickness, are designed and currently fabricated.

show abstract

Section: Actuator Analysismentioning

confidence: 72%

Section: Actuator Analysismentioning

confidence: 99%

Actuator tests for a large deformable membrane mirror

et al. 2006

Self Cite

View full text Add to dashboard Cite

show abstract

“…The WF correction performance was tested for different amounts of actuator couplings. Low couplings of 20% and 30% see inferior Strehl ratios than the strong couplings of 40% and 50% throughout, due to inadequate actuator spacing for the considered Fried parameter of r 0 15 cm [22]. This also leads to large variances in the low-coupling results, which are magnified by a small number of outliers occurring for all tested versions.…”

Section: Influence Of Actuator Couplingmentioning

confidence: 97%

GPU implementation for spline-based wavefront reconstruction

et al. 2018

Self Cite

View full text Add to dashboard Cite

This paper presents an adaptation of the distributed-spline-based aberration reconstruction method for Shack-Hartmann (SH) slope measurements to extremely large-scale adaptive optics systems and the execution on graphics processing units (GPUs). The introduction of a hierarchical multi-level scheme for the elimination of piston offsets between the locally computed wavefront (WF) estimates solves the piston error propagation observed for a large number of partitions with the original version. To obtain a fully distributed method for WF correction, the projection of the phase estimates is locally approximated and applied in a distributed fashion, providing stable results for low and medium actuator coupling. An implementation of the method with the parallel computing platform CUDA exploits the inherently distributed nature of the algorithm. With a standard off-the-shelf GPU, the computation of the adaptive optics correction updates is accomplished in under 1 ms for the benchmark case of a 200×200 SH array.

show abstract

“…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.…”

mentioning

confidence: 99%

Modeling and state-space identification of deformable mirrors

Haber

Verhaegen

2020

Opt. Express

Self Cite

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

Distributed control in adaptive optics: deformable mirror and turbulence modeling

Cited by 11 publications

References 14 publications

Actuator tests for a large deformable membrane mirror

Actuator tests for a large deformable membrane mirror

GPU implementation for spline-based wavefront reconstruction

Modeling and state-space identification of deformable mirrors

Contact Info

Product

Resources

About