38 research outputs found
Scaling Multidimensional Inference for Big Structured Data
In information technology, big data is a collection of data sets so large and complex that it becomes difficult to process using traditional data processing applications [151]. In a
world of increasing sensor modalities, cheaper storage, and more data oriented questions, we are quickly passing the limits of tractable computations using traditional statistical analysis
methods. Methods which often show great results on simple data have difficulties processing complicated multidimensional data. Accuracy alone can no longer justify unwarranted memory
use and computational complexity. Improving the scaling properties of these methods for multidimensional data is the only way to make these methods relevant. In this work we explore methods for improving the scaling properties of parametric and nonparametric
models. Namely, we focus on the structure of the data to lower the complexity of a specific family of problems. The two types of structures considered in this work are distributive
optimization with separable constraints (Chapters 2-3), and scaling Gaussian processes for multidimensional lattice input (Chapters 4-5). By improving the scaling of these methods, we can expand their use to a wide range of applications which were previously intractable
open the door to new research questions
Design, validation and application of wave-to-wire models for heaving point absorber wave energy converters
Ocean waves represent an untapped source of renewable energy which can significantly contribute
to the energy transition towards a sustainable energy mix. Despite the significant potential of this
energy source and the multiple solutions suggested for the extraction of energy from ocean waves,
some of which have demonstrated to be technically viable, no commercial wave energy farm has
yet been connected to the electricity grid. This means that none of the technologies suggested in
the literature has achieved economic viability.
In order to make wave energy converters economically viable, it is essential to accurately understand
and evaluate the holistic behaviour and performance of wave energy converters, including
all the different conversion stages from ocean waves to the electricity grid. This can be achieved
through wave tank or open ocean testing campaigns, which are extremely expensive and, thus,
can critically determine the financial sustainability of the developing organisation, due to the risk
of such large investments. Therefore, precise mathematical models that consider all the important
dynamics, losses and constraints of the different conversion stages (including wave-structure
hydrodynamic interaction and power take-off system), known as wave-to-wire models, are crucial
in the development of successful wave energy converters. Hence, a comprehensive literature review
of the different mathematical approaches suggested for modelling the different conversion
stages and existing wave-to-wire models is presented, defining the foundations of parsimonious
wave-to-wire models and their potential applications.
As opposed to other offshore applications, wave energy converters need to exaggerate their
motion to maximise energy absorption from ocean waves, which breaks the assumption of small
body motion upon which linear models are based. An extensive investigation on the suitability of
linear models and the relevance of different nonlinear effects is carried out, where control conditions
are shown to play an important role. Hence, a computationally efficient mathematical model
that incorporates nonlinear Froude-Krylov forces and viscous effects is presented. In the case
of the power take-off system, mathematical models for different hydraulic transmission system
configurations and electric generator topologies are presented, where the main losses are included
using specific loss models with parameters identified via manufacturers’ data. In order to gain
confidence in the mathematical models, the models corresponding to the different conversion stages
are validated separately against either high-fidelity well-established software or experimental
results, showing very good agreement.
The main objective of this thesis is the development of a comprehensive wave-to-wire model.
This comprehensive wave-to-wire model is created by adequately combining the subsystems corresponding
to the different components or conversion stages. However, time-step requirements
vary significantly depending on the dynamics included in each subsystem. Hence, if the time-step
required for capturing the fastest dynamics is used in all the subsystems, unnecessary computation
is performed in the subsystems with slower dynamics. Therefore, a multi-rate time-integration
scheme is implemented, meaning that each subsystem uses the sample period required to adequately
capture the dynamics of the components included in that conversion stage, which significantly
reduces the overall computational requirements. In addition, the relevance of using a high-fidelity
comprehensive wave-to-wire model in accurately designing wave energy converters and assessing
their capabilities is demonstrated. For example, energy maximising controllers based on excessively
simplified mathematical models result in dramatic consequences, such as negative average
generated power or situations where the device remains stuck at one of the end-stops of the power
take-off system.
Despite the reasonably high-fidelity of the results provided by this comprehensive wave-towire
model, some applications require the highest possible fidelity level and have no limitation
with respect to computational cost. Hence, the simulation platform HiFiWEC, which couples a
numerical wave tank based on computational fluid dynamics to the high-fidelity power take-off
model, is created. In contrast, low computational cost is the main requirement for other applications
and, thus, a systematic complexity reduction approach is suggested in this thesis, significantly
reducing the computational cost of the HiFiWEC platform, while retaining the adequate fidelity
level for each application. Due to the relevance of the nonlinearity degree when evaluating
the complexity of a mathematical model, two nonlinearity measures to quantify this nonlinearity
degree are defined. Hence, wave-to-wire models specifically created for each application are generated
via the systematic complexity reduction approach, which provide the adequate trade-off
between computational cost and fidelity level required for each application
Proceedings of the ECCOMAS Thematic Conference on Multibody Dynamics 2015
This volume contains the full papers accepted for presentation at the ECCOMAS Thematic Conference on Multibody Dynamics 2015 held in the Barcelona School of Industrial Engineering, Universitat Politècnica de Catalunya, on June 29 - July 2, 2015. The ECCOMAS Thematic Conference on Multibody Dynamics is an international meeting held once every two years in a European country. Continuing the very successful series of past conferences that have been organized in Lisbon (2003), Madrid (2005), Milan (2007), Warsaw (2009), Brussels (2011) and Zagreb (2013); this edition will once again serve as a meeting point for the international researchers, scientists and experts from academia, research laboratories and industry working in the area of multibody dynamics. Applications are related to many fields of contemporary engineering, such as vehicle and railway systems, aeronautical and space vehicles, robotic manipulators, mechatronic and autonomous systems, smart structures, biomechanical systems and nanotechnologies. The topics of the conference include, but are not restricted to: ● Formulations and Numerical Methods ● Efficient Methods and Real-Time Applications ● Flexible Multibody Dynamics ● Contact Dynamics and Constraints ● Multiphysics and Coupled Problems ● Control and Optimization ● Software Development and Computer Technology ● Aerospace and Maritime Applications ● Biomechanics ● Railroad Vehicle Dynamics ● Road Vehicle Dynamics ● Robotics ● Benchmark ProblemsPostprint (published version
Multibody dynamics 2015
This volume contains the full papers accepted for presentation at the ECCOMAS Thematic Conference on Multibody Dynamics 2015 held in the Barcelona School of Industrial Engineering, Universitat Politècnica de Catalunya, on June 29 - July 2, 2015. The ECCOMAS Thematic Conference on Multibody Dynamics is an international meeting held once every two years in a European country. Continuing the very successful series of past conferences that have been organized in Lisbon (2003), Madrid (2005), Milan (2007), Warsaw (2009), Brussels (2011) and Zagreb (2013); this edition will once again serve as a meeting point for the international researchers, scientists and experts from academia, research laboratories and industry working in the area of multibody dynamics. Applications are related to many fields of contemporary engineering, such as vehicle and railway systems, aeronautical and space vehicles, robotic manipulators, mechatronic and autonomous systems, smart structures, biomechanical systems and nanotechnologies. The topics of the conference include, but are not restricted to: Formulations and Numerical Methods, Efficient Methods and Real-Time Applications, Flexible Multibody Dynamics, Contact Dynamics and Constraints, Multiphysics and Coupled Problems, Control and Optimization, Software Development and Computer Technology, Aerospace and Maritime Applications, Biomechanics, Railroad Vehicle Dynamics, Road Vehicle Dynamics, Robotics, Benchmark Problems. The conference is organized by the Department of Mechanical Engineering of the Universitat Politècnica de Catalunya (UPC) in Barcelona. The organizers would like to thank the authors for submitting their contributions, the keynote lecturers for accepting the invitation and for the quality of their talks, the awards and scientific committees for their support to the organization of the conference, and finally the topic organizers for reviewing all extended abstracts and selecting the awards nominees.Postprint (published version
Modeling and Simulation in Engineering
This book provides an open platform to establish and share knowledge developed by scholars, scientists, and engineers from all over the world, about various applications of the modeling and simulation in the design process of products, in various engineering fields. The book consists of 12 chapters arranged in two sections (3D Modeling and Virtual Prototyping), reflecting the multidimensionality of applications related to modeling and simulation. Some of the most recent modeling and simulation techniques, as well as some of the most accurate and sophisticated software in treating complex systems, are applied. All the original contributions in this book are jointed by the basic principle of a successful modeling and simulation process: as complex as necessary, and as simple as possible. The idea is to manipulate the simplifying assumptions in a way that reduces the complexity of the model (in order to make a real-time simulation), but without altering the precision of the results
MS FT-2-2 7 Orthogonal polynomials and quadrature: Theory, computation, and applications
Quadrature rules find many applications in science and engineering. Their analysis is a classical area of applied mathematics and continues to attract considerable attention. This seminar brings together speakers with expertise in a large variety of quadrature rules. It is the aim of the seminar to provide an overview of recent developments in the analysis of quadrature rules. The computation of error estimates and novel applications also are described
Generalized averaged Gaussian quadrature and applications
A simple numerical method for constructing the optimal generalized averaged Gaussian quadrature formulas will be presented. These formulas exist in many cases in which real positive GaussKronrod formulas do not exist, and can be used as an adequate alternative in order to estimate the error of a Gaussian rule. We also investigate the conditions under which the optimal averaged Gaussian quadrature formulas and their truncated variants are internal