Engineering Optimization and Modeling Center

Engineering, Iceland

Engineering Optimization and Modeling Center

Engineering, Iceland

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Bekasiewicz A.,Reykjavik University | Bekasiewicz A.,Engineering Optimization and Modeling Center | Koziel S.,Reykjavik University | Koziel S.,Engineering Optimization and Modeling Center | Leifsson L.,Iowa State University
Procedia Computer Science | Year: 2015

A methodology for a rapid design optimization of integrated photonic couplers is presented. The proposed technique exploits variable-fidelity electromagnetic (EM) simulation models, additive response correction for accommodating the discrepancies between the EM models of various fidelities, and local response surface approximations for a fine tuning of the final design. A specific example of a 1,555 nm coupler is considered with an optimum design obtained at a computational cost corresponding to about 24 high-fidelity EM simulations of the structure. © The Authors. Published by Elsevier B.V.


Koziel S.,Reykjavik University | Koziel S.,Engineering Optimization and Modeling Center | Bekasiewicz A.,Reykjavik University | Bekasiewicz A.,Engineering Optimization and Modeling Center | Leifsson L.,Iowa State University
Procedia Computer Science | Year: 2015

A procedure for low-cost multi-objective design optimization of antenna structures is discussed. The major stages of the optimization process include: (i) an initial reduction of the search space aimed at identifying its relevant subset containing the Pareto-optimal design space, (ii) construction-using sampled coarse-discretization electromagnetic (EM) simulation data-of the response surface approximation surrogate, (iii) surrogate optimization using a multi-objective evolutionary algorithm, and (iv) the Pareto front refinement. Our optimization procedure is demonstrated through the design of a planar quasi Yagi-Uda antenna. The final set of designs representing the best available trade-offs between conflicting objectives is obtained at a computational cost corresponding to about 172 evaluations of the high-fidelity EM antenna model. © The Authors. Published by Elsevier B.V.


Tesfahunegn Y.A.,Reykjavik University | Tesfahunegn Y.A.,Engineering Optimization and Modeling Center | Koziel S.,Reykjavik University | Koziel S.,Engineering Optimization and Modeling Center | And 4 more authors.
Procedia Computer Science | Year: 2015

This paper presents a space mapping algorithm for airfoil shape optimization enhanced with adjoint sensitivities. The surrogate-based algorithm utilizes low-cost derivative information obtained through adjoint sensitivities to improve the space mapping matching between a high-fidelity airfoil model, evaluated through expensive CFD simulations, and its fast surrogate. Here, the airfoil surrogate model is constructed though low-fidelity CFD simulations. As a result, the design process can be performed at a low computational cost in terms of the number of high-fidelity CFD simulations. The adjoint sensitivities are also exploited to speed up the surrogate optimization process. Our method is applied to a constrained drag minimization problem in two-dimensional inviscid transonic flow. The problem is solved for several low-fidelity model termination criteria. The results show that when compared with direct gradient-based optimization with adjoint sensitivities, the proposed approach requires 49-78% less computational cost while still obtaining a comparable airfoil design. © The Authors. Published by Elsevier B.V.


Koziel S.,Engineering Optimization and Modeling Center | Koziel S.,Reykjavik University | Leifsson L.,Engineering Optimization and Modeling Center | Leifsson L.,Reykjavik University
AIAA Journal | Year: 2013

A surrogate-based optimization algorithm for transonic airfoil design is presented. The approach replaces the direct optimization of an accurate, but computationally expensive, high-fidelity computational fluid dynamics model by an iterative reoptimization of a physics-based surrogate model. The surrogate model is constructed, during each design iteration, using the low-fidelity model and the data obtained from one high-fidelity model evaluation. The lowfidelity model is based on the same governing fluid flow equations as the high-fidelity one, but uses coarser mesh resolution and relaxed convergence criteria. The shape-preserving response prediction technique is utilized to predict the high-fidelity model response, here, the airfoil pressure distribution. In this prediction process, the shapepreserving response prediction employs the actual changes of the low-fidelity model response due to the design variable adjustments. The shape-preserving response prediction algorithm is embedded into the trust region framework that ensures good convergence properties of the optimization procedure. This method is applied to constrained airfoil lift maximization and drag minimization in two-dimensional inviscid transonic flow. The optimized designs are obtained at lower computational cost than that of two comparators. The robustness and scaling properties of the proposed algorithm are investigated. Copyright © 2012 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.


Koziel S.,Engineering Optimization and Modeling Center | Ogurtsov S.,Engineering Optimization and Modeling Center | Bandler J.W.,McMaster University | Bandler J.W.,Bandler Corporation | Cheng Q.S.,McMaster University
IEEE Transactions on Microwave Theory and Techniques | Year: 2013

We present a robust space mapping (SM) algorithm exploiting electromagnetic (EM)-based adjoint sensitivities for microwave design optimization. Our approach utilizes low-cost EM-based adjoint sensitivities and trust region methods to improve an SM algorithm at three levels, which are: 1) to build a better overall surrogate while ensuring convergence; 2) to speed up and safeguard the parameter extraction steps; and 3) to speed up and safeguard the surrogate optimization process. We describe the implementation at each level in detail. We review relevant adjoint sensitivity analysis methods. We also review prior SM methods that exploit both sensitivity and adjoint sensitivity. We summarize these methods in four categories. We compare our proposed approach with them. Efficiency, robustness, and versatility of our method are demonstrated by three design examples: an antenna, a planar filter, and a 3-D resonator filter. We compare the results with those obtained by SM without using adjoint sensitivity information and by direct optimization of the high-fidelity EM models. © 2013 IEEE.


Koziel S.,Engineering Optimization and Modeling Center | Bekasiewicz A.,Engineering Optimization and Modeling Center
International Journal of RF and Microwave Computer-Aided Engineering | Year: 2016

Geometry scaling of compact microwave structures is a challenging problem because of complex relationships between the physical dimensions of the circuit and its electrical characteristics, which is mostly caused by considerable cross-couplings in densely arranged layouts. Yet, possibility of rapid redesign of a structure for various sets of design specification is important from practical point of view. In this article, we develop a procedure for expedited dimension scaling of compact microwave couplers with respect to two independent criteria. Our approach exploits inverse surrogates constructed at the level of equivalent circuit model and correction techniques that permits low-cost re-design of the coupler structure (at the level of EM-simulation model) for a required operating frequency and power split ratio. The procedure is demonstrated using a folded microstrip rat-race coupler. The scaling range for the considered example is from 0.5 to 2.0 GHz for the operating frequency, and from -6 dB to 0 dB for the power split ratio. © 2016 Wiley Periodicals, Inc.


Koziel S.,Engineering Optimization and Modeling Center | Bekasiewicz A.,Engineering Optimization and Modeling Center
International Journal of RF and Microwave Computer-Aided Engineering | Year: 2016

In this article, we describe a procedure for reliable and computationally efficient design optimization of miniaturized impedance matching transformers. Our approach exploits a concept of feature-based optimization (FBO). According to FBO, considerable reduction of the computational cost of the simulation-driven design process can be achieved-compared to conventional methods-by reformulating given performance requirements (typically, minimization of reflection over a frequency range of interest) in terms of suitably defined response features. For impedance transformer circuits, the feature points are defined as local maxima of the reflection characteristic, as well as the points defining the -20 dB bandwidth. As the feature point coordinates (i.e., their frequencies and levels) depend on the geometry parameters of the structure in less nonlinear manner than the original responses (S-parameters versus frequency), the optimization algorithm exhibits faster convergence. Further reduction of the optimization cost is obtained by utilization of variable-fidelity electromagnetic simulations. Our technique is demonstrated using two design cases of an example miniaturized three-section 50-to-100 ohm microstrip transformer. © 2016 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2016. © 2016 Wiley Periodicals, Inc.


Koziel S.,Engineering Optimization and Modeling Center | Jacobs J.P.,Electronic and Computer Engineering
International Journal of RF and Microwave Computer-Aided Engineering | Year: 2016

We present a computationally efficient method for detecting faulty elements in a small linear microstrip patch array from samples of the array's far-field magnitude radiation pattern (here represented by realistic EM simulations). Regardless of the array size, our method requires only one expensive full-wave entire-array simulation-compared to, e.g., the 696 required by the previous best method (Patnaik et al., IEEE Trans Antennas Propag 55 (2007), 775-777) for a 16-element array. This one simulation gives the accurate far-field magnitude pattern of the original defect-free array, and is used in conjunction with the defect-free array's analytical array factor to formulate a response correction function, which can then be used to construct an accurate approximation of the EM-simulated pattern of any arbitrary faulty array at very low cost. The low cost and high accuracy of these approximations make possible an enumeration strategy for identifying the faulty elements, which would have been computationally prohibitive were EM-simulated patterns to be used. Our method was robust in handling arrays of double the size considered in Patnaik et al., IEEE Trans Antennas Propag 55 (2007), 775-777, while expanding on (Patnaik et al., IEEE Trans Antennas Propag 55 (2007), 775-777) by also addressing partial faults and measurement noise. Accuracies in detecting up to three faults (including partial ones) in arrays of 16 and 32 elements exceeded 97% under noise-free conditions, and were above 93% in the presence of 2 dB measurement noise. © 2016 Wiley Periodicals, Inc.


Koziel S.,Engineering Optimization and Modeling Center | Bekasiewicz A.,Engineering Optimization and Modeling Center | Kurgan P.,Engineering Optimization and Modeling Center
International Journal of RF and Microwave Computer-Aided Engineering | Year: 2015

In this article, fast electromagnetic (EM) simulation-driven design optimization of compact microwave couplers is addressed. The main focus is on explicit reduction of the circuit footprint. Our methodology relies on the penalty function approach, which allows us to minimize the circuit area while ensuring equal power split between the output ports and providing a sufficient bandwidth with respect to the return loss and isolation around the operating frequency. Computational efficiency of the design process is achieved by exploiting variable-fidelity EM simulations, local response surface approximation models, as well as suitable response correction techniques for design tuning. The technique described in this work is demonstrated using two examples of compact rat-race couplers. The size-reduction-oriented designs are compared with performance-oriented ones to illustrate available design trade-offs. Final design solutions of the former case illustrate ∼92% of miniaturization for both coupler examples (with corresponding fractional bandwidths of 16%). Alternative design solutions pertaining to the latter case show a lesser size reduction (∼90% for both examples), but present a much wider bandwidths (∼25% for both couplers). The overall computational cost of the design procedure corresponds to about 20 and 10 high-fidelity coupler simulations for the first and second design example, respectively. Numerical results are also validated experimentally. © 2015 Wiley Periodicals, Inc.


Koziel S.,Engineering Optimization and Modeling Center | Bekasiewicz A.,Engineering Optimization and Modeling Center
International Journal of RF and Microwave Computer-Aided Engineering | Year: 2015

Design of miniaturized microwave components is a challenging task. On one hand, due to considerable electromagnetic (EM) cross-couplings in highly compressed layouts full-wave EM analysis is necessary for accurate evaluation of the structure performance. Conversely, high-fidelity EM simulation is computationally expensive so that automated determination of the structure dimensions may be prohibitive when using conventional numerical optimization routines. In this article, computationally efficient simulation-driven design of a miniaturized dual-band microstrip branch-line coupler is presented. The optimization methodology relies on suitably extracted features of a highly nonlinear response of the coupler structure under design. The design objectives are formulated in terms of the feature point locations, and the optimization is carried out iteratively with the linear model of the features utilized as a fast predictor. The entire process is embedded in the trust-region framework as convergence safeguard. Owing to only slightly nonlinear dependence of the features on the geometry parameters of the circuit at hand, the optimized design satisfying prescribed performance requirements is obtained at the low computational cost of only 24 high-fidelity EM simulations of the structure. Experimental validation of the fabricated coupler prototype is also provided. © 2015 Wiley Periodicals, Inc.

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