11 research outputs found
Análise cinemática via quatérnios duais aplicada a um sistema veículo-manipulador subaquático
Tese (doutorado) - Universidade Federal de Santa Catarina, Centro Tecnológico, Programa de Pós-Graduação em Engenharia de Automação e Sistemas, Florianópolis, 2011Este trabalho propõe metodologias para a análise cinemática de sistemas veículo-manipulador subaquáticos (UVMS) através de quatérnios duais com o intuito de impor menor variação de torque nas juntas durante o seguimento de trajetória. Em adição a isso, evita-se a ocorrência de singularidades cinemáticas e obtém-se menor custo computacional. A abordagem é apresentada inicialmente como uma alternativa à representação tradicional dos movimentos aplicada na cinemática direta de mecanismos através da convenção de Denavit-Hartenberg e do método dos helicoides sucessivos. O benefício dessa representação está no menor custo computacional, mas principalmente, no desacoplamento dos ângulos de orientação de forma a evitar as singularidades cinemáticas. Os quatérnios duais também são aplicados na cinemática inversa em uma metodologia interativa através do método de Davies como uma modalidade de realimentação livre de singularidades. Por fim, a principal contribuição deste trabalho está na proposta da aplicação dos quatérnios duais na cinemática inversa diferencial em por uma metodologia analítica, através da apresentação do Jacobiano dual-quaterniônico. Essas abordagens são aplicadas a um sistema subaquático, onde o amortecimento imposto pela imersão no fluido dissipa grandes variações de torque e agrega erros no seguimento da trajetória.This work proposes a methodology for kinematic analysis of underwater vehicle-manipulator systems (UVMS) using dual-quaternions. The objective is to provide a less joint torque variation to trajectory tracking, avoidance of kinematic singularities occurrence and a lower computational cost. The approach is initially presented as an alternative representation of movements applied to direct kinematics through the Denavit- Hartenberg convention and the successive screws method. The benefit of this representation is a lower computational cost, but mainly, the decoupling of orientation angles in order to avoid kinematic singularities. The dual quaternions also are applied in the inverse kinematics in an interactive approach through Davies method as a feedback without singularities. Finally, the main contribution of this work is the proposal of dual quaternions application in an analytical approach of differential inverse kinematics through of the dual-quaternionic Jacobian. These approaches are applied to an underwater system, where the damping imposed by fluid immersion dissipates large torque variations adding errors in trajectory tracking
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
Notes in Pure Mathematics & Mathematical Structures in Physics
These Notes deal with various areas of mathematics, and seek reciprocal
combinations, explore mutual relations, ranging from abstract objects to
problems in physics.Comment: Small improvements and addition
Twistor actions for gauge theory and gravity
This is a review of recent developments in the study of perturbative gauge
theory and gravity using action functionals on twistor space. It is intended to
provide a user-friendly introduction to twistor actions, geared towards
researchers or graduate students interested in learning something about the
utility, prospects, and shortcomings of this approach. For those already
familiar with the twistor approach, it should provide a condensed overview of
the literature as well as several novel results of potential interest. This
work is based primarily upon the author's D.Phil. thesis. We first consider
four-dimensional, maximally supersymmetric Yang-Mills theory as a gauge theory
in twistor space. We focus on the perturbation theory associated to this
action, which in an axial gauge leads to the MHV formalism. This allows us to
efficiently compute scattering amplitudes at tree-level (and beyond) in twistor
space. Other gauge theory observables such as local operators and null
polygonal Wilson loops can also be formulated twistorially, leading to proofs
for several correspondences between correlation functions and Wilson loops, as
well as a recursive formula for computing mixed Wilson loop / local operator
correlators. We then apply the twistor action approach to general relativity,
using the on-shell equivalence between conformal and Einstein gravity. This can
be extended to N=4 supersymmetry. The perturbation theory of the twistor action
leads to formulae for the MHV amplitude with and without cosmological constant,
yields a candidate for the Einstein twistor action, and induces a MHV formalism
on twistor space. Appendices include discussion of super-connections and
Coulomb branch regularization on twistor space.Comment: 178 pages, 30 figures. Review based on the author's D.Phil. thesis.
v2: references adde
Quantum brane cosmology
This thesis deals with the interaction of quantum mechanical models and cosmologies
based on brane universes, an area of active theoretical speculation over the last five years.For convenience, the material has been split into two parts. Part 1 deals with a selection
of background topics which are necessary and relevant to the original research. This
research is presented in Part 2. In addition, some auxiliary topics, both more elementary
and more advanced, are described in the appendices. The selection of background topics has
been influenced by the various techniques, physical theories and mathematical technologies
which play a major role in the work presented in Part 2. Although the exposition is ad
hoc, an attempt has been made to systematically develop portions where the technique (or
use of it) may be unfamiliar.A fairly complete treatment of the necessary mathematical scaffolding is supplied. Although important, this material is familiar or strongly mathematical, and is deferred to
the appendices. This includes an elementary survey of functional analysis in Appendix A,
sufficient to support a discussion of the path integral. The path integral formalism is used
extensively throughout this thesis, and, where available, constitutes our preferred representation of quantum mechanics. The discussion is limited to the relevant portions of the
theory: functions in Banacli spaces, and the Sturm-Liouville basis (technology which appears many times in Part 2); direct evaluation of Gaussian functional integrals, ubiquitous
in field theory calculations; and ((-function regularization of the operator determinants to
which such Gaussian integrals give rise, which has a direct application in Chapter 9. In
Appendix B we describe the necessary framework of differential geometry which supports
general relativity, and low-energy discussions of string theory. All calculations in metric
gravity are based on differential geometry, together with a good proportion of the technology which buttresses quantum field theory on curved space time, string theory, and some
more advanced representations of quantum mechanics (see below). All of this is used extensively throughout both parts of the thesis. We include some more advanced topological
technology which supports the discussion of string compactification. General results from
compactification theory, when appropriately interpreted in the brane context, contribute
important stability results for zero-modes of the Kaluza—Klein fields, and provide a natural
home for the spectral KK technology used (in one form or another) throughout Part 2,
but most especially in Chapter 7 and Chapter 8. Einstein gravity and Yang-Mills theory
are set in context as examples of connexions on fibre bundles
New Directions for Contact Integrators
Contact integrators are a family of geometric numerical schemes which
guarantee the conservation of the contact structure. In this work we review the
construction of both the variational and Hamiltonian versions of these methods.
We illustrate some of the advantages of geometric integration in the
dissipative setting by focusing on models inspired by recent studies in
celestial mechanics and cosmology.Comment: To appear as Chapter 24 in GSI 2021, Springer LNCS 1282
Report / Institute für Physik
In this report the Institutes of Physics of the Universität Leipzig present their scientific activities and major achievements in the year 2003