- document
-
Qiu, Y. (author), Van Gijzen, M.B. (author), Van Winderden, J.W. (author), Verhaegen, M.H.G. (author)This paper presents a class of preconditioners for sparse systems arising from discretized partial differential equations (PDEs). In this class of preconditioners, we exploit the multilevel sequentially semiseparable (MSSS) structure of the system matrix. The off-diagonal blocks of MSSS matrices are of low-rank, which enables fast computations...conference paper 2013
- document
- Verhaegen, M.G. (author), Van der Veen, A.J. (author) conference paper 1993
- document
-
Verstraete, H.R.G.W. (author), Verhaegen, M.H.G. (author), Kalkman, J. (author)In scanning microscopy and optical coherence tomography, aberrations of the wave-front cause a loss in intensity and resolution. Intensity and resolution are quantified using Fresnel propagation, Fraunhofer diffraction, and the calculation of overlap integrals.conference paper 2013
- document
-
Smith, C. (author), Marinica, R. (author), Verhaegen, M. (author)We propose an efficient approximation to the nonlinear phase diversity method for wavefront reconstruction from intensity measurements. The new method, iterative linear phase diversity (ILPD), assumes that the residual phase aberration is small and makes use of a first order Taylor expansion of the point spread function (PSF) performed for an...conference paper 2013
- document
-
Hinnen, K. (author), Doelman, N. (author), Verhaegen, M. (author)The problem of finding the closed-loop optimal controller is formulated in an H2-optimal control framework. This provides a natural way to account for the fact that in many AO systems the wavefront phase cannot be measured directly. Given a multi-variable disturbance model of both wavefront slopes and wavefront phases,3 this provides a general...conference paper 2005
- document
-
Fraanje, R. (author), Doelman, N. (author), Verhaegen, M. (author)Using a matching pursuit (MP) approach to solve least squares problems with a sparsity constraint sparse controllers are computed to compensate for atmospheric turbulence. The method has been validated by simulation of von K´arm´an turbulence with frozen flow for the case of prediction, reconstruction and control.conference paper 2009
- document
-
Ellenbroek, R. (author), Verhaegen, M. (author), Doelman, N. (author), Hamelinck, R. (author), Rosielle, N. (author), Steinbuch, M. (author)Future large optical telescopes require adaptive optics (AO) systems whose deformable mirrors (DM) have ever more degrees of freedom. This paper describes advances that are made in a project aimed to design a new AO system that is extendible to meet tomorrow’s specifications. Advances on the mechanical design are reported in a companion paper ...conference paper 2006
- document
-
Hinnen, K. (author), Verhaegen, M. (author), Doelman, N. (author)Most adaptive optics systems (AO) are based on a simple control law that is unable to account for the temporal evolution of the wavefront. In this paper, a recently proposed data-driven H2-optimal control approach is demonstrated on an AO laboratory setup. The proposed control approach does not assume any form of decoupling and can therefore...conference paper 2006
- document
-
Doelman, N.J. (author), Hinnen, K.J.G. (author), Stoffelen, F.J.G. (author), Verhaegen, M.H. (author)An Adaptive Optics (AO) system for astronomy is analysed from a control point of view. The focus is put on the temporal error. The AO controller is identified as a feedback regulator system, operating in closed-loop with the aim of rejecting wavefront disturbances. Limitations on the performance of feedback regulator systems are discussed. The...conference paper 2004
- document
-
Hamelinck, R. (author), Ellenbroek, R. (author), Rosielle, N. (author), Steinbuch, M. (author), Verhaegen, M. (author), Doelman, N. (author)A new prototype adaptive deformable mirror for future AO-systems is presented that consists of a thin continuous membrane on which push-pull actuators impose out-of-plane displacements. Each actuator has ±10?m stroke, nanometer resolution and only mW’s heat dissipation. The mirror’s modular design makes the mechanics, electronics and control...conference paper 2008
- document
-
Hinnen, K. (author), Verhaegen, M. (author), Doelman, N. (author)Even though the wavefront distortion introduced by atmospheric turbulence is a dynamic process, its temporal evolution is usually neglected in the adaptive optics (AO) control design. Most AO control systems consider only the spatial correlation in a separate wavefront reconstruction step. By accounting for the temporal evolution of the...conference paper 2005
- document
-
Korkiakoski, V.A. (author), Keller, C.U. (author), Doelman, N. (author), Kenworthy, M. (author), Otten, G. (author), Verhaegen, M. (author)We investigate methods to calibrate the non-common path aberrations at an adaptive optics system having a wavefront-correcting device working with an extremely high resolution (larger than 150x150 correcting elements). We use focal-plane images collected successively, the corresponding phase-diversity information and numerically efficient...conference paper 2014
- document
-
Agbana, T.E. (author), Soloviev, O. (author), Bezzubik, V. (author), Patlan, V. (author), Verhaegen, M. (author), Vdovin, G.V. (author)We have implemented an extended depth of field optical system by wavefront coding with a micromachined membrane deformable mirror. This approach provides a versatile extension to standard wavefront coding based on fixed phase mask. First experimental results validate the feasibility of the use of adaptive optics for variable depth wavefront...conference paper 2015
- document
-
Van Engelen, T. (author), Schuurmans, J. (author), Kanev, S. (author), Dong, J. (author), Verhaegen, M.H.G. (author), Hayashi, Y. (author)Extreme environmental conditions as well as system failure are real-life phenomena. Especially offshore, extreme environmental conditions and system faults are to be dealt with in an effective way. The project Sustainable Control, a new approach to operate wind turbines (Agentschap NL, grant EOSLT02013) pro- vides the concepts for an integrated...conference paper 2011
- document
-
Piscaer, P.J. (author), Soloviev, O.A. (author), Verhaegen, M.H.G. (author)This paper discusses various practical problems arising in the design and simulation of predictive control methods for adaptive optics. Although there has been increased attention towards optimal prediction and control methods for AO systems, they are often tested in simplified simulation environments. The use of advanced AO simulators...conference paper 2020
- document
-
Soloviev, O.A. (author), Verhaegen, M.H.G. (author), Vdovin, Gleb (author)Shack-Hartmann (SH) sensor, based on sampling of wavefront tilts in subapertures, is a simple, reliable, and widely used in adaptive optics wavefront sensor. A wavefront curvature sensor has the advantage of providing the results suitable for direct control of membrane and bimorph deformable mirrors [1], but requires linear registration of...conference paper 2015
- document
-
Yu, C. (author), Verhaegen, M.H.G. (author)This paper studies the local identification of large-scale homogeneous systems<br/>with general network topologies. The considered local system identification problem involves unmeasurable signals between neighboring subsystems. Compared with our previous work in Yu et al. (2014) which solves the local identification of 1D homogeneous systems,...conference paper 2015
- document
-
Yu, C. (author), Verhaegen, M.H.G. (author), Hansson, A (author)This paper studies the local subspace identification of 1D homogeneous networked systems. The main challenge lies at the unmeasurable interconnection signals between neighboring subsystems. Since there are many unknown inputs to the concerned local system, the corresponding identification problem is semi-blind. To cope with this problem, a...conference paper 2015
- document
- Hansson, A (author), Verhaegen, M.H.G. (author) conference paper 2014
- document
-
Yu, C. (author), Verhaegen, M.H.G. (author), Kovalsky, S (author), Basri, R (author)The identification of structured state-space model has been intensively studied for a long time but still has not been adequately addressed. The main challenge is that the involved estimation problem is a non-convex (or bilinear) optimization problem. This paper is devoted to developing an identification<br/>method which aims to find the global...conference paper 2015