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Reykjavík University, Iceland

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15 Papers

Computationally Efficient Multi-Objective Optimization of and Experimental Validation of Yagi-Uda Antenna

Authors: Adrian Bekasiewicz ¹ , Slawomir Koziel ² and Leifur Leifsson ²

Affiliations: ¹ Gdansk University of Technology, Poland , ² Reykjavik University, Iceland

Digital Object Identifier: 10.5220/0005136607980805

Proceedings of SDDOM 2014/SIMULTECH, ISBN: 978-989-758-038-3

Quick Abstract

In this paper, computationally efficient multi-objective optimization of antenna structures is discussed. As a design case, we consider a multi-parameter planar Yagi-Uda antenna structure, featuring a driven element, three directors, and a feeding structure. Direct optimization of the high-fidelity electromagnetic (EM) antenna model is prohibitive in computational terms. Instead, our design methodology exploits response surface approximation (RSA) models constructed from sampled coarse-discretization EM simulation data. The RSA model is utilized to determine the Pareto optimal set of the best possible trade-offs between conflicting objectives. In order to alleviate the difficulties related to a large number of designable parameters, the RSA model is constructed in the initially reduced design space, where the lower/upper parameter bounds are estimated by solving appropriate single-objective problems resulting in identifying the extreme point of the Pareto set. The main optimization engine is multi-objective evolutionary algorithm (MOEA). Selected designs are subsequently refined using space mapping technique to obtain the final representation of the Pareto front at the high-fidelity EM antenna model level. The total design cost corresponds to less than two hundred of EM antenna imulations.

Low-cost EM-Simulation-based Multi-objective Design Optimization of Miniaturized Microwave Structures

Authors: Slawomir Koziel ¹ , Adrian Bekasiewicz ² , Piotr Kurgan ² and Leifur Leifsson ¹

Affiliations: ¹ Reykjavik University, Iceland , ² Gdansk University of Technology, Poland

Digital Object Identifier: 10.5220/0005127107670774

Proceedings of SDDOM 2014/SIMULTECH, ISBN: 978-989-758-038-3

Quick Abstract

In this work, a simple yet reliable technique for fast multi-objective design optimization of miniaturized microwave structures is discussed. The proposed methodology is based on point-by-point identification of a Pareto-optimal set of designs representing the best possible trade-offs between conflicting objectives such as electrical performance parameters as well as the size of the structure of interest. For the sake of computational efficiency, most operations are performed on suitably corrected equivalent circuit model of the structure under design. Model correction is implemented using a space mapping technique involving, among others, frequency scaling. Our approach is demonstrated using a compact rat-race coupler. For this specific example, a set of ten designs representing a Pareto set for two objectives (electrical performance and the layout area) is identified at the cost corresponding to less than thirty high-fidelity EM simulations of the structure.

Trawl-door Shape Optimization with 3D CFD Models and Local Surrogates

Authors: Elvar Hermannsson ¹ , Leifur Leifsson ² , Slawomir Koziel ² , Piotr Kurgan ² and Adrian Bekasiewicz ³

Affiliations: ¹ KTH Royal Institute of Technology, Sweden , ² Reykjavik University, Iceland , ³ Gdansk University of Technology, Poland

Digital Object Identifier: 10.5220/0005131307750784

Proceedings of SDDOM 2014/SIMULTECH, ISBN: 978-989-758-038-3

Quick Abstract

Design and optimization of trawl-doors are key factors in minimizing the fuel consumption of fishing vessels. This paper discusses optimization of the trawl-door shapes using high-fidelity 3D computational fluid dynamic (CFD) models. The accurate 3D CFD models are computationally expensive and, therefore, the direct use of traditional optimization algorithms, which often require a large number of evaluations, may be prohibitive. The design approach presented here is a variation of sequential approximate optimization exploiting low-order local response surface models of the expensive 3D CFD simulations. The algorithm is applied to the design of modern and airfoil-shaped trawl-doors.

Simulation of Self Organized Electron Beams in Vacuum Microdiodes

Topics: Non-Linear Systems; Electronics Design and Manufacturing; Computer Simulation Techniques

Authors: Marjan Ilkov ¹ , Andreas Pedersen ² , Andrei Manolescu ¹ and Ágúst Valfells ¹

Affiliations: ¹ Reykjavík University, Iceland , ² University of Iceland, Iceland

Digital Object Identifier: 10.5220/0004595502240228

Proceedings of SIMULTECH 2013, ISBN: 978-989-8565-69-3

Quick Abstract

Simulation of vacuum micro-diodes can be done quite effectively using molecular dynamics methods. This results in much higher fidelity simulations than can be obtained using the particle-in-cell method (PIC), which is most common for plasma and particle beam simulations. In particular, this method is superior to the PIC method when treating systems where collisional effects are important. In this paper we present some results concerning electron beam structure in a vacuum micro-diode obtained using a molecular dynamics code developed at Reykjavík University.

Related Ontology Subjects/Areas/Topics (7)

Application Domains	Formal Methods	Simulation and Modeling
Computer Simulation Techniques	Non-Linear Systems	Simulation Tools and Platforms
Electronics Design and Manufacturing

Attention Capabilities for AI Systems

Topics: Environmental Monitoring and Control; Robot Design, Development and Control; Real-Time Systems Control; Software Agents for Intelligent Control Systems; Perception and Awareness; Intelligent Components for Control

Authors: Helgi Páll Helgason ¹ and Kristinn R. Thórisson ²

Affiliations: ¹ Reykjavik University, Iceland , ² Reykjavik University and Icelandic Institute for Intelligent Machines, Iceland

Digital Object Identifier: 10.5220/0004120502810286

Proceedings of ICINCO 2012, ISBN: 978-989-8565-21-1

Quick Abstract

Much of present AI research is based on the assumption of computational systems with infinite resources, an assumption that is either explicitly stated or implicit in the work as researchers ignore the fact that most real-world tasks must be finished within certain time limits, and it is the role of intelligence to effectively deal with such limitations. Expecting AI systems to give equal treatment to every piece of data they encounter is not appropriate in most real-world cases; available resources are likely to be insufficient for keeping up with available data in even moderately complex environments. Even if sufficient resources are available, they might possibly be put to better use than blindly applying them to every possible piece of data. Finding inspiration for more intelligent resource management schemes is not hard, we need to look no further than ourselves. This paper explores what human attention has to offer in terms of ideas and concepts for implementing intelligent resource management and how the resulting principles can be extended to levels beyond human attention. We also discuss some ideas for the principles behind attention mechanisms for artificial (general) intelligences.

Related Ontology Subjects/Areas/Topics (10)

Environmental Monitoring and Control	Perception and Awareness	Robotics and Automation
Informatics in Control, Automation and Robotics	Real-Time Systems Control	Signal Processing, Sensors, Systems Modeling and Control
Intelligent Components for Control	Robot Design, Development and Control	Software Agents for Intelligent Control Systems
Intelligent Control Systems and Optimization

Low-speed Modeling and Simulation of Torpedo-shaped AUVs

Topics: Vehicle Control Applications; Space and Underwater Robotics; Modeling, Simulation and Architecture

Authors: Bjarni Helgason ¹ , Leifur Leifsson ¹ , Indridi Rikhardsson ¹ , Helgi Thorgilsson ² and Slawomir Koziel ¹

Affiliations: ¹ Reykjavik University, Iceland , ² Teledyne Gavia ehf, Iceland

Digital Object Identifier: 10.5220/0004047103330338

Proceedings of ICINCO 2012, ISBN: 978-989-8565-22-8

Quick Abstract

Autonomous underwater vehicles (AUVs) have become important in many marine engineering applications, such as environmental monitoring, pipeline inspections, or oceanography. For these types of applications, most of the AUVs available in both academia and industry are shaped like a torpedo and travel at speeds of 3 knots or higher. There is an growing interest in AUVs that are capable of performing tasks at both low-speed as well as high speeds. Currently, many torpedo-shaped AUVs are not capable of controlled low-speed motion. This paper presents a simulation model for the low-speed motion of torpedo-shaped AUVs. The model is capable of simulating the surge, sway, heave, and yaw motions. The hydrodynamic forces acting on the AUV hull are modelled using strip theory, experimental data, and computational fluid dynamics. The simulation model was implemented using a commercially available software and validated using experimental data obtained from the Gavia AUV. The results show that the simulation model captures the AUV motion at low-speed and agrees well with the experimental data.

Related Ontology Subjects/Areas/Topics (5)

Informatics in Control, Automation and Robotics		Robotics and Automation		Vehicle Control Applications
Modeling, Simulation and Architectures		Space and Underwater Robotics

Managing Model Fidelity for Efficient Optimization of Antennas using Variable-resolution Electromagnetic Simulations

Authors: Slawomir Koziel , Stanislav Ogurtsov and Leifur Leifsson

Affiliation: Reykjavik University, Iceland

Digital Object Identifier: 10.5220/0004147404570465

Proceedings of SDDOM 2012/SIMULTECH, ISBN: 978-989-8565-20-4

Quick Abstract

Electromagnetic (EM) simulation has become an important tool in the design of contemporary antenna structures. However, accurate simulations of realistic antenna models are expensive and therefore design automation by employing EM solver within an optimization loop may be prohibitive because of its high computational cost. Efficient EM-driven antenna design can be performed using surrogate-based optimization (SBO). A generic approach to construct surrogate models of antennas involves the use of coarse-discretization EM simulations (low-fidelity models). A proper selection of the surrogate model fidelity is a key factor that influences both the performance of the design optimization process and its computational cost. Despite its importance, this issue has not yet been investigated in the literature. Here, we focus on a problem of proper surrogate model management. More specifically, we carry out a numerical study that aims at finding a trade-off between the design cost and reliability of the SBO algorithms. Our considerations are illustrated using several antenna design cases. Furthermore, we demonstrate that the use of multiple models of different fidelity may be beneficial to reduce the design cost while maintaining the robustness of the optimization process.

Microwave Design Optimization Exploiting Adjoint Sensitivity

Authors: Slawomir Koziel , Leifur Leifsson and Stanislav Ogurtsov

Affiliation: Reykjavik University, Iceland

Digital Object Identifier: 10.5220/0004164104990506

Proceedings of SDDOM 2012/SIMULTECH, ISBN: 978-989-8565-20-4

Quick Abstract

Adjustment of geometry and material parameters is an important step in the design of microwave devices and circuits. Nowadays, it is typically performed using high-fidelity electromagnetic (EM) simulations, which might be a challenging and time consuming process because accurate EM simulations are computationally expensive. In particular, design automation by employing an EM solver in an numerical optimization algorithm may be prohibitive. Recently, adjoint sensitivity techniques become available in commercial EM simulation software packages. This makes it possible to speed up the EM-driven design optimization process either by utilizing the sensitivity information in conventional, gradient-based algorithms or by combining it with surrogate-based approaches. In this paper, we review several recent methods and algorithms for microwave design optimization using adjoint sensitivity. We discuss advantages and disadvantages of these techniques and illustrate them through numerical examples.

Transonic Wing Optimization by Variable-resolution Modeling and Space Mapping

Authors: Eirikur Jonsson , Leifur Leifsson and Slawomir Koziel

Affiliation: Reykjavik University, Iceland

Digital Object Identifier: 10.5220/0004164004890498

Proceedings of SDDOM 2012/SIMULTECH, ISBN: 978-989-8565-20-4

Quick Abstract

This paper presents an efficient aerodynamic design optimization methodology for wings in transonic flow. The approach replaces the computationally expensive high-fidelity CFD model in an iterative optimization process with a corrected polynomial approximation model constructed by a cheap low-fidelity CFD model. The output space mapping technique is used to correct the approximation model to yield an accurate predictor of the high-fidelity one. Both CFD models employ the RANS equations with the Spalart-Allmaras turbulence model, but the low-fidelity one uses a coarse mesh resolution and relaxed convergence criteria. Our method is applied to a constrained lift maximization of a rectangular wing at transonic conditions with 3 design variables. The optimized designs are obtained by using 50 low-fidelity CFD model evaluations to set up the approximation model and 7 to 8 high-fidelity model evaluations, equivalent to around 10 high-fidelity CFD model evaluations.

Trawl-door Performance Analysis and Design Optimization with CFD

Authors: Eirikur Jonsson , Leifur Leifsson and Slawomir Koziel

Affiliation: Reykjavik University, Iceland

Digital Object Identifier: 10.5220/0004163904790488

Proceedings of SDDOM 2012/SIMULTECH, ISBN: 978-989-8565-20-4

Quick Abstract

Rising fuel prices and inefficient fishing gear are hampering the fishing industry. In this paper, we present a computational fluid dynamic (CFD) model to analyse the hydrodynamic performance of trawl-doors, which are a major contributor to the high fuel consumption of fishing vessels. Furthermore, we couple the CFD model with an efficient design optimization technique and demonstrate how to redesign the trawl-door shapes for minimum drag at a given lift. The optimization techinique is surrogate-based and employs a coarse discritization CFD model with relaxed convergence criteria. The surrogate model is constructed using the physics based low-fidelity model and space mapping. The CFD model is applied to the analysis of current trawl-door shapes and reveals that they are operated at low efficiency (with lift-to-drag ratios lower than 1), mainly due to massively separated flow. An example design optimization case study reveals that the angle of attack can be reduced significantly by re-positioning and tilting the leading-edge slats. The performance can be improved by as much as 24 times (attaining lift-ro-drag ratios around 24).

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