Rotational Mobility Analysis of the 3-RFR Class of Spherical Parallel Robots

none4noSpherical parallel manipulators (SPMs) are used to orient a tool in the space with three degrees of freedom exploiting the strengths of a multi-limb architecture. On the other hand, the performance of parallel kinematics machines (PKMs) is often affected by the occurrence of different kinds of singular configurations. The paper aims at characterizing a class of SPMs for which all singularities come to coincide and a single expression is able to describe all the singular configurations of the machines. The study is focused on a class of SPMs with 3-RFR topology (Revolute-Planar-Revolute pairs for each of the three limbs) addressing the mobility and singularity analysis by means of polynomial decomposition and screw theory. The neatness of the equations that are worked out, expressed in a robust formulation based on rotation invariants, allows a straightforward planning of singularity free tasks and simplifies the synthesis of dexterous machines.openCorinaldi, David; Carbonari, Luca; Palpacelli, Matteo-Claudio; Callegari, MassimoCorinaldi, David; Carbonari, Luca; Palpacelli, Matteo-Claudio; Callegari, Massim

Symmetric Subspace Motion Generators

When moving an object endowed with continuous symmetry, an ambiguity arises in its underlying rigid body transformation, induced by the arbitrariness of the portion of motion that does not change the overall body shape. The functional redundancy caused by continuous symmetry is ubiquitously present in a broad range of robotic applications, including robot machining and haptic interface (revolute symmetry), remote center of motion devices for minimal invasive surgery (line symmetry), and motion modules for hyperredundant robots (plane symmetry). In this paper, we argue that such functional redundancy can be systematically resolved by resorting to symmetric subspaces (SSs) of the special Euclidean group SE(3), which motivates us to systematically investigate the structural synthesis of SS motion generators. In particular, we develop a general synthesis procedure that allows us to generate a wide spectrum of novel mechanisms for use in the applications mentioned

Molecular dynamics of nanometric layers of glass formers in interaction with solid substrates

Broadband Dielectric Spectroscopy (BDS) in combination with a nanostructured electrode arrangement – which circumvents the conventional need to evaporate metal electrodes onto soft matter – is used to study the molecular dynamics of several glass forming materials confined in nanometric (> 5 nm) layers. Other complementary experimental tools employed in this work include spectroscopic vis-Ellipsometry (SE), AC-chip calorimetry (ACC), X-ray reflectrometry (XRR), Differential Scanning Calorimetry (DSC) and Atomic Force Microscopy (AFM). The latter is used to characterize the topography of the samples and to determine their thicknesses. Under the conditions of annealing samples (Tg + 50K) in high oil-free vacuum (10E-6 mbars) for at least 12 h and carrying out measurements in inert (dry nitrogen or argon) atmosphere, it is found for all studied thin layers that the structural relaxation, and hence the dynamic glass transition – in its mean relaxation times – remains within a margin ±3 K from the respective bulk behaviour. It is revealed, inter alia, that the one-dimensional confinement of thin films introduces restrictions on other (slower) molecular relaxation processes which manifest, depending on the specific system under investigation, as (i) an interruption of the end-to-end (normal mode) fluctuation of the chains, or (ii) a slowing down of the delta-relaxation when the system is cooled towards glass-formation. Furthermore, (iii) evidence is provided to show that the dimensionality of confinement plays a significant role in determining the resulting dynamics. A molecular understanding of these findings is given, and the discussion presented with respect to the on-going international debate about dynamics in confinement.:1. Introduction 2. The glass transition and chain dynamics 2.1 The phenomenology of the glass transition 2.2 Theories of the glass transition 2.2.1 Free volume theories 2.2.2 Cooperative concepts 2.2.3 Mode-coupling theory 2.3 Dynamics of polymer chains in melt 2.4 The dynamic glass transition in confinement 2.4.1 Experiments: state-of-the-art 2.4.2 Theoretical attempts at explaining dynamics in confinement 3. Sample preparation and experimental techniques 3.1 Thin-film preparation by spin-coating 3.1.1 Films on glass slides 3.1.2 Films on silicon wafers 3.1.3 Reproducibility of sample preparation 3.1.4 Stability of thin film samples 3.1.5 Film thickness determination 3.1.6 Sample annealing experiments 3.2 Use of nanostructured electrodes – a novel approach 3.3 Poly(cis-1,4-isoprene) (PI) in porous media 3.4 Experimental techniques 3.4.1 Broadband Dielectric Spectroscopy (BDS) 3.4.1.1 Polarization 3.4.1.2 Dielectric relaxation 3.4.1.3 Debye relaxation 3.4.1.4 Non-Debye relaxation 3.4.1.5 Dielectric data in the time domain 3.4.1.6 Conductivity contribution 3.4.1.7 The distribution of relaxation times 3.4.1.8 BDS – summary 3.4.2 Spectroscopic Ellipsometry (SE) 3.4.3 AC-chip calorimetry (ACC) 4. Results and Discussion 4.1 Effect of sample geometry on measured dynamics 4.1.1 Introduction 4.1.2 Experimental details 4.1.3 Results and discussion 4.1.4 Summary 4.2 Dynamics of polystyrene in a wide range of molecular weights 4.2.1 Introduction 4.2.2 Experimental details 4.2.3 Results and discussion 4.2.4 Summary 4.3 Molecular dynamics of itraconazole confined in thin supported layers 4.3.1 Introduction 4.3.2 Experimental details 4.3.3 Results and discussion 4.3.4 Summary 4.4 Segmental and chain dynamics in nanometric layers of poly(cis-1,4-isoprene) 4.4.1 Introduction 4.4.2 Experimental details and data analysis 4.4.2.1 Sample preparation 4.4.2.2 Data analysis 4.4.3 Results and discussion 4.4.3.1 1- versus 2-D confinement of poly(cis-1,4-isoprene) 4.4.4 Summary 5 Conclusions 5.1 Dynamics in confinement – a wider perspectiv

Contribuições para a enumeração e para a análise de mecanismos e manipuladores paralelos

Tese (doutorado) - Universidade Federal de Santa Catarina, Centro Tecnológico, Programa de Pós-Graduação em Engenharia Mecânica, Florianópolis, 2010A fase de projeto conceitual demecanismos emanipuladores paralelos, i.e. estruturas cinematicas, destina-se ao desenvolvimento da concepçao da cadeia cinematica. As etapas fundamentais para o desenvolvimento da concepao da cadeia cinematica sao sintese e analise. A sintese corresponde à enumeraçao de concepcoes e a analise corresponde `a seleçao das concepçoes mais promissoras considerando os requisitos de projeto. O objetivo deste trabalho é aplicar ferramentas da teoria de grupos e teoria de grafos para a enumeraçao e para a analise de estruturas cinematicas. A enumeraçao sera desenvolvida de forma sistematica em tres niveis: enumeraçao de cadeias cinematicas, enumeraçao de mecanismos e enumeraçao de manipuladores paralelos. A aplicaçao de ferramentas da teoria de grafos e grupos permite desenvolver novos metodos para enumeraçao e, consequentemente, obter novos resultados. A analise sera simplificada considerando um novo metodo que avalia as simetrias das cadeias cinematicas. Uma cadeia cinematica é representada de forma univoca atraves de um grafo. A representaçao atraves do grafo permite a manipulaçao computacional do problema de enumeraçao de cadeias cinematicas. A aplicaçao de ferramentas integradas da teoria de grafos e teoria de grupos permite identificar as simetrias das cadeias cinematicas atraves do grupo de automorfismos do grafo e, assim, é possivel identificar quais são as possiveis escolhas de base para novos mecanismos e avaliar quais sao as possiveis escolhas de base e efetuador final para manipuladores paralelos. O primeiro nivel da sintese corresponde à enumeraçao de cadeias cinematicas com determinada mobilidade, numero de elos, numero de juntas que operam num determinado sistema de helicoides. O segundo nivel da sintese corresponde a enumeraçao de mecanismos. Um mecanismo é uma cadeia cinematica com um elo escolhido para ser a base. Assim, a enumeraçao de mecanismos consiste em determinar todas as possiveis escolhas de bases para uma determinada cadeia cinematica. O principal conceito empregado neste nivel é o de simetria de grafos não coloridos e orbitas do grupo de automorfismos. O terceiro nivel da sintese corresponde `a enumeraçao de manipuladores paralelos. Um manipulador paralelo é uma cadeia cinematica com um elo escolhido para ser a base e outro para ser o efetuador final. Em outras palavras, um manipulador paralelo é um mecanismo com um elo escolhido para ser o efetuador final. Assim, a enumeraçao de manipuladores paralelos consiste em determinar todas as possiveis escolhas de efetuador final para um determinado mecanismo. O principal conceito empregado neste nivel é a simetria de grafos coloridos e orbitas do grupo de automorfismos de grafos coloridos. Na etapa de analise das concepcoes enumeradas serao abordadas propriedades bem estabelecidas na literatura: mobilidade, variedade, conectividade, grau de controle, redundancia e simetria. Mobilidade e variedade sao propriedades globais das estruturas cinematicas. Conectividade, grau de controle e redundancia sao propriedades locais, i.e. entre dois elos da estrutura cinematica e sao dadas por matrizes n×n, onde n é o número de elos da cadeia. A simetria pode ser considerada uma propriedade global e/ou local da estrutura cinem´atica. A aplicaçao de ferramentas integradas da teoria de grafos e teoria de grupos permite demonstrar que as propriedades locais sao invariantes pela acao do grupo de automorfismos do grafo, i.e. elas sao propriedades simetricas. Desta forma, a representaçao matricial é reduzida de n×n para o×n, onde o é o numero de orbitas do grupo de automorfismos do grafo aassociado à estrutura cinematica. Essa abordagem permite simplificar a analise de estruturas cinematicas apenas considerando as simetrias das cadeia associadas

Optimization of a Parallel Mechanism Design with Respect to a Stewart Platform Control Design

Předkládaná práce se zabývá návrhem modelu dynamiky paralelního manipulátoru optimálního pro účely návrhu řízení. Zvolený přístup je založen na modelování dynamiky systému v simulačním prostředí Matlab SimMechanics následovaném linearizací modelu. Výsledný stavový lineární model mimo jiné umožňuje snadné posouzení řiditelnosti a pozorovatelnosti modelu. Díky své relativní jednoduchosti je model také výpočetně nenáročný. Přístup je demonstrován na návrhu dvouvrstvého řízení SimMechanics modelu Stewartovy platformy, na kterém bylo následně navržené řízení úspěšně testováno. Podstatná část práce obsahuje přístup k modelování neurčitých parametrů dynamického modelu Stewartovy platformy a stejnosměrného motoru Maxon RE 35 a jeho výsledky. Předložený přístup je založen na modelování parametrické neurčitosti způsobem, kdy je neurčitost definována individuálně pro jednotlivé prvky stavových matic modelu. Samotná neurčitost je potom určena rozdílem mezi jednotlivými parametry příslušných matic nominálního modelu a modelu se stanovenou maximální neurčitostí parametrů. Výsledný neurčitostní model je vzhledem ke své stavové reprezentaci vhodný pro návrh regulátoru založeném na metodách návrhu robustního řízení, například minimalizaci normy H-nekonečno. Popsaná metoda byla použita pro kompenzaci posunu mezi pracovními body, okolo kterých je prováděna linearizace a pro kompenzaci nepřesnosti modelování vybraných parametrů modelů Stewartovy platformy a stejnosměrného motoru. Získané modely (v prostředí SimMechanics a neurčitostní model) byly experimentálně porovnány s chováním jednoho z lineárních pohonů Stewartovy platformy. Rozdíl v datech obdržených ze simulace v prostředí SimMechanics a naměřených na reálném stroji byl téměř kompletně pokryt neurčitostním modelem. Prezentovaná metoda neurčitostního modelování je velice univerzální a aplikovatelná na libovolný stavový model.The proposed work is dealing with an optimal model of a parallel manipulator dynamics for a control design purposes. The approach is based on modeling of the system dynamics in Matlab Simmechanics followed by the model linearization. The obtained linear model may be simply inspected from the controllability and observability point of view. It is also computational modest thanks to its simplicity. This is demonstrated on designing of a two – layer control for a model of a Stewart platform. The control based on such a linear model was successfully tested on the original nonlinear model. The essential part of the the work is dealing with modeling of uncertain parameters in the dynamic model of the Stewart platform and DC motor Maxon RE 35. The proposed approach is based on modeling of a parametric uncertainty where the uncertainty is defined individually for particular elements of the model state matrices. The uncertainty itself is set by the difference between parameters of corresponding matrices of the nominal linear model and model with maximally perturbed parameters. The obtained uncertain model is for its form suitable for the robust control design methods, for example via minimizing an H-infinity norm. The method was used for a compensation of the shifting of the linearization operating points in the Stewart platform and for compensation of the modeling inaccuracy of selected parameters in the Stewart platform and the DC motor model. The obtained models (SimMechanics and uncertain state - space) were compared with the single linear actuator of the Stewart platform. The difference between the simulated SimMechanics model and measured data was almost completely covered by the uncertain model. The method is highly versatile and applicable on any state-space model.

Industrial Robotics

This book covers a wide range of topics relating to advanced industrial robotics, sensors and automation technologies. Although being highly technical and complex in nature, the papers presented in this book represent some of the latest cutting edge technologies and advancements in industrial robotics technology. This book covers topics such as networking, properties of manipulators, forward and inverse robot arm kinematics, motion path-planning, machine vision and many other practical topics too numerous to list here. The authors and editor of this book wish to inspire people, especially young ones, to get involved with robotic and mechatronic engineering technology and to develop new and exciting practical applications, perhaps using the ideas and concepts presented herein

Synthesis and characterization of cyclic polysthers with controlled orientation of the dipolar moment along the chain contour

239 p.En esta tesis, se estudia la síntesis de poli (glicidil fenil éter) cíclico. Se emplearon diferentes sistemas de iniciación para generar precursores lineales con características moleculares controladas y microestructuras dipolares controladas. Usando estos precursores lineales, se obtuvieron las cadenas cíclicas correspondientes mediante la técnica de "ring closure". Se realizó una optimización cuidadosa de las condiciones de síntesis para generar cadenas cíclicas puras. Los polímeros obtenidos se caracterizaron por NMR, SEC, MALDI-ToF MS. Finalmente, se estudió la microestructura dipolar de los diferentes polímeros sintetizados utilizando espectroscopía dieléctrica de banda ancha. Esta técnica permitió probar las características topológicas de las cadenas de polímeros y dio resultados sobre la dinámica de los anillos para cadenas con pesos moleculares por debajo del enredo

Synthesis and characterization of cyclic polysthers with controlled orientation of the dipolar moment along the chain contour

239 p.En esta tesis, se estudia la síntesis de poli (glicidil fenil éter) cíclico. Se emplearon diferentes sistemas de iniciación para generar precursores lineales con características moleculares controladas y microestructuras dipolares controladas. Usando estos precursores lineales, se obtuvieron las cadenas cíclicas correspondientes mediante la técnica de "ring closure". Se realizó una optimización cuidadosa de las condiciones de síntesis para generar cadenas cíclicas puras. Los polímeros obtenidos se caracterizaron por NMR, SEC, MALDI-ToF MS. Finalmente, se estudió la microestructura dipolar de los diferentes polímeros sintetizados utilizando espectroscopía dieléctrica de banda ancha. Esta técnica permitió probar las características topológicas de las cadenas de polímeros y dio resultados sobre la dinámica de los anillos para cadenas con pesos moleculares por debajo del enredo