Mecanismos flexíveis, nos quais a deformação elástica é aproveitada na atuação cinemática, têm grande empregabilidade em dispositivos de mecânica de precisão, engenharia biomédica, e mais recentemente em microeletromecanismos (MEMS). Entre as diversas técnicas empregadas para o seu projeto, a otimização topológica tem se mostrado a mais genérica e sistemática. A grande dificuldade destes projetos é conciliar os requisitos cinemáticos com a resistência mecânica da estrutura. Neste trabalho, é implementado um critério de resistência dentro da formulação do problema de otimização, com o intuito de gerar mecanismos que cumpram a tarefa cinemática desejada mas ao mesmo tempo não ultrapassem limites de tensão predeterminados. Esta restrição adicional também visa aliviar o problema bastante conhecido do aparecimento de articulações. Não linearidade geométrica e de material (hiperelasticida de compressível) são implementadas na solução das equações através do método dos elementos finitos para levar em conta os grandes deslocamentos do mecanismo. O método das assíntotas móveis é usado para a atualização das variáveis de projeto. As derivadas do problema de otimização são calculadas analiticamente, pelo método adjunto. Técnicas de projeção são aplicadas para a garantia de topologias livres de instabilidades numéricas comuns em otimização topológica, e projetos otimizados mais próximos de um espaço 0/1 para as densidades físicas. / Compliant me hanisms, in whi h the elasti strain is the basis for kinemati a tua- tion are widely used in pre ision me hani s devi es, biomedi al engineering, and re ently in mi roele trome hani al systems (MEMS). Among several te hniques applied in ompliant me hanisms design, topology optimization has been one of the most general and systemati . The great hallenge in these designs is to ouple both the kinemati s and the me hani al strength riteria requirements. In this work, a strength riteria for the optimization problem is applied, with the aim of generating ompliant me hanisms that ful ll the desired kine- mati tasks while omplying with a stress threshold. The addition of a stress onstraint to the formulation for ompliant me hanisms in topology optimization also aims to allevi- ate the appearan e of hinges in the optimized topology, a well known issue in the design of ompliant me hanisms. Geometri al and material ( ompressible hyperelasti ity) nonlin- earities are applied to the nite element equilibrium equations, to take into a ount large displa ements. The method of moving asymptotes is applied for design variables updating. The derivatives are al ulated analyti ally, by the adjoint method. Proje tion ltering te h- niques are applied, in order to guarantee topologies free of ommon numeri al instabilities in topology optimization, and optimized designs near the 0/1 solution for the physi al densities.

Learning from Demonstration (LfD) has been used in robotics research for the last decades to solve issues pertaining to conventional programming of robots. This framework enables a robot to learn a task simply from a human demonstration. However, it is unfeasible to teach a robot all possible scenarios, which may lead to e.g. the robot getting stuck. In order to solve this, a search is necessary. However, no current work is able to provide a search approach that is both simple and general. This thesis develops and evaluates a new framework based on LfD that combines both of these aspects. A single demonstration of a human search is made and a model of it is learned. From this model a search trajectory is sampled and optimized. Based on that trajectory, a prediction of the encountered environmental forces is made. An impedance controller with feed-forward of the predicted forces is then used to evaluate the algorithm on a Peg-in-Hole task. The final results show that the framework is able to successfully learn and reproduce a search from just one single human demonstration. Ultimately some suggestions are made for further benchmarks and development.

abstract: Myoelectric control is lled with potential to signicantly change human-robot interaction. Humans desire compliant robots to safely interact in dynamic environments associated with daily activities. As surface electromyography non-invasively measures limb motion intent and correlates with joint stiness during co-contractions, it has been identied as a candidate for naturally controlling such robots. However, state-of-the-art myoelectric interfaces have struggled to achieve both enhanced functionality and long-term reliability. As demands in myoelectric interfaces trend toward simultaneous and proportional control of compliant robots, robust processing of multi-muscle coordinations, or synergies, plays a larger role in the success of the control scheme. This dissertation presents a framework enhancing the utility of myoelectric interfaces by exploiting motor skill learning and exible muscle synergies for reliable long-term simultaneous and proportional control of multifunctional compliant robots. The interface is learned as a new motor skill specic to the controller, providing long-term performance enhancements without requiring any retraining or recalibration of the system. Moreover, the framework oers control of both motion and stiness simultaneously for intuitive and compliant human-robot interaction. The framework is validated through a series of experiments characterizing motor learning properties and demonstrating control capabilities not seen previously in the literature. The results validate the approach as a viable option to remove the trade-o between functionality and reliability that have hindered state-of-the-art myoelectric interfaces. Thus, this research contributes to the expansion and enhancement of myoelectric controlled applications beyond commonly perceived anthropomorphic and \intuitive control" constraints and into more advanced robotic systems designed for everyday tasks. / Dissertation/Thesis / Doctoral Dissertation Mechanical Engineering 2015

Mecanismos flexíveis, nos quais a deformação elástica é aproveitada na atuação cinemática, têm grande empregabilidade em dispositivos de mecânica de precisão, engenharia biomédica, e mais recentemente em microeletromecanismos (MEMS). Entre as diversas técnicas empregadas para o seu projeto, a otimização topológica tem se mostrado a mais genérica e sistemática. A grande dificuldade destes projetos é conciliar os requisitos cinemáticos com a resistência mecânica da estrutura. Neste trabalho, é implementado um critério de resistência dentro da formulação do problema de otimização, com o intuito de gerar mecanismos que cumpram a tarefa cinemática desejada mas ao mesmo tempo não ultrapassem limites de tensão predeterminados. Esta restrição adicional também visa aliviar o problema bastante conhecido do aparecimento de articulações. Não linearidade geométrica e de material (hiperelasticida de compressível) são implementadas na solução das equações através do método dos elementos finitos para levar em conta os grandes deslocamentos do mecanismo. O método das assíntotas móveis é usado para a atualização das variáveis de projeto. As derivadas do problema de otimização são calculadas analiticamente, pelo método adjunto. Técnicas de projeção são aplicadas para a garantia de topologias livres de instabilidades numéricas comuns em otimização topológica, e projetos otimizados mais próximos de um espaço 0/1 para as densidades físicas. / Compliant me hanisms, in whi h the elasti strain is the basis for kinemati a tua- tion are widely used in pre ision me hani s devi es, biomedi al engineering, and re ently in mi roele trome hani al systems (MEMS). Among several te hniques applied in ompliant me hanisms design, topology optimization has been one of the most general and systemati . The great hallenge in these designs is to ouple both the kinemati s and the me hani al strength riteria requirements. In this work, a strength riteria for the optimization problem is applied, with the aim of generating ompliant me hanisms that ful ll the desired kine- mati tasks while omplying with a stress threshold. The addition of a stress onstraint to the formulation for ompliant me hanisms in topology optimization also aims to allevi- ate the appearan e of hinges in the optimized topology, a well known issue in the design of ompliant me hanisms. Geometri al and material ( ompressible hyperelasti ity) nonlin- earities are applied to the nite element equilibrium equations, to take into a ount large displa ements. The method of moving asymptotes is applied for design variables updating. The derivatives are al ulated analyti ally, by the adjoint method. Proje tion ltering te h- niques are applied, in order to guarantee topologies free of ommon numeri al instabilities in topology optimization, and optimized designs near the 0/1 solution for the physi al densities.

Mecanismos flexíveis, nos quais a deformação elástica é aproveitada na atuação cinemática, têm grande empregabilidade em dispositivos de mecânica de precisão, engenharia biomédica, e mais recentemente em microeletromecanismos (MEMS). Entre as diversas técnicas empregadas para o seu projeto, a otimização topológica tem se mostrado a mais genérica e sistemática. A grande dificuldade destes projetos é conciliar os requisitos cinemáticos com a resistência mecânica da estrutura. Neste trabalho, é implementado um critério de resistência dentro da formulação do problema de otimização, com o intuito de gerar mecanismos que cumpram a tarefa cinemática desejada mas ao mesmo tempo não ultrapassem limites de tensão predeterminados. Esta restrição adicional também visa aliviar o problema bastante conhecido do aparecimento de articulações. Não linearidade geométrica e de material (hiperelasticida de compressível) são implementadas na solução das equações através do método dos elementos finitos para levar em conta os grandes deslocamentos do mecanismo. O método das assíntotas móveis é usado para a atualização das variáveis de projeto. As derivadas do problema de otimização são calculadas analiticamente, pelo método adjunto. Técnicas de projeção são aplicadas para a garantia de topologias livres de instabilidades numéricas comuns em otimização topológica, e projetos otimizados mais próximos de um espaço 0/1 para as densidades físicas. / Compliant me hanisms, in whi h the elasti strain is the basis for kinemati a tua- tion are widely used in pre ision me hani s devi es, biomedi al engineering, and re ently in mi roele trome hani al systems (MEMS). Among several te hniques applied in ompliant me hanisms design, topology optimization has been one of the most general and systemati . The great hallenge in these designs is to ouple both the kinemati s and the me hani al strength riteria requirements. In this work, a strength riteria for the optimization problem is applied, with the aim of generating ompliant me hanisms that ful ll the desired kine- mati tasks while omplying with a stress threshold. The addition of a stress onstraint to the formulation for ompliant me hanisms in topology optimization also aims to allevi- ate the appearan e of hinges in the optimized topology, a well known issue in the design of ompliant me hanisms. Geometri al and material ( ompressible hyperelasti ity) nonlin- earities are applied to the nite element equilibrium equations, to take into a ount large displa ements. The method of moving asymptotes is applied for design variables updating. The derivatives are al ulated analyti ally, by the adjoint method. Proje tion ltering te h- niques are applied, in order to guarantee topologies free of ommon numeri al instabilities in topology optimization, and optimized designs near the 0/1 solution for the physi al densities.

This dissertation presents new concepts and methodology in designing shape-morphing structures using bistable elements. Developed using the Pseudo-Rigid-Body Model (PRBM), linear bistable compliant mechanism elements produce predictable and controllable length changes. Step-by-step design procedures are developed to guide the design process of these bistable elements. Two different examples of Shape-Morphing Space Frames (SMSFs) were designed and prototyped utilizing the bistable linear elements in a single-layer grid, in addition to flexures and rigid links, to morph a cylindrical space frame into both a hyperbolic and a spherical space frame. Moreover, bistable unit-cell compliant-mechanism elements were also developed to morph a compact structure from a specific initial shape to a final specific shape. The detailed design of those unit cells were done using Computer-aided design (CAD) software following a novel design procedure to transform a one-degree-of-freedom mechanism into a structure with sufficient compliance within its links to toggle between two chosen stable positions. Two different design examples were investigated in this research and prototyped to demonstrate the ability to morph disks into a hemisphere or a sphere with the structure being stable in both states (disk and sphere).

Additive manufacturing offers a manufacturing technique to produce complex geometry prototypes at a rapid pace and low cost. These advantages advocate additive manufacturing for the design and production of cellular structures. Cellular structures are interesting because they contain a large amount of porosity (void space of air) to manifest a lightweight structure. Designs of cellular structures generate a periodic pattern; often of complex geometry, called a lattice. There has been a significant amount of research to maximize specific stiffness of lattice structures but little to evaluate low-stiffness lattices. Low-stiffness structures benefit energy absorbance through bending of the lattice. This research seeks to assess diamond lattices as low stiffness, bending structures. The research involves PA2200 (Nylon 12) laser sintered diamond lattices with experimental compression testing and direct FEA model comparison. A correction factor is applied for a design offset of laser sintered lattices. Once applied, the experimental and FEA data agree in validating the diamond lattice as a bending-dominated structure. Diamond lattices show a 4th order relationship between stiffness and parameters of thickness and unit cell length. For density, stiffness maintains a 2nd order relationship, as predicted by bending dominated structures. The resulting stiffness can be tuned over a stiffness range of four orders of magnitude. Further research shows the results for modifying the diamond lattice and scaling stiffness and density using other materials (like metals) to expand the range of stiffness and compare diamond lattices on material property charts. Lastly, the effective Poisson’s ratio varies from 0.5 to 0.4 depending on the (t/L) ratio.

My work has been focused on compliant mechanisms, origami engineering, and rapid prototyping. Two of the projects that I worked on were focused on compliant mechanisms and origami engineering. The similar goal of both of those projects was to create an origami membrane whose kinematics mimic that of an existing mechanism. The first project created an origami membrane to mimic the kinematics of a planar shape-changing mechanism. This mechanism was a square shaped unit-cell which could shear, compress, and expand in its own plane. In addition to waterproofing the mechanism, the first project also sought to optimize the dimensions of the mechanism in order to reduce internal stresses during actuation. The results of the optimization portion of this project were a reduction of internal stresses by more than 22%. The results of the origami synthesis portion of the project was the creation of a membrane with an origami pattern whose kinematics mimic that of the shape-shifting surface. The origami membrane is capable of being folded into each of the various positions that the shape-shifting surface is able to fold into. The second project sought to create a similar type of origami fold pattern, but for a Shape Morphing Space Frame (SMSF). This project created an origami membrane designed to mimic the kinematics of a mechanism that had been developed in a different previous project. The mechanism consisted of a series of Linear Bistable Elements (LBEs) which were assembled to form a cylinder. When the LBEs were actuated the cylinder would deform to a hyperboloid. This project created an origami membrane whose kinematics mimic that of the shape-morphing space frame and was able to change side length by more than 30%. The origami membrane was able to fold to each of the SMSF’s states. This project also developed a method for synthesizing an origami fold pattern with shape-morphing triangles. Both of the first two projects that comprise this dissertation sought to develop an origami fold pattern whose kinematics mimic that of an existing mechanism. In each of these projects one of the future goals for the project was to create a prototype where the mechanism and the origami are fabricated together as one integrated prototype. Possible methods of accomplishing this goal include rapid prototyping. Thus, the mechanics of rapid prototyping are of concern for future work on these projects. The third project developed a part which could be printed from a Fused Deposition Modeling (FDM) machine to test certain material properties (yield strength and elastic modulus) after it had been processed through the FDM. This would allow the material properties to be tested without the use of expensive test equipment. This project developed eight parts which could be used to bracket certain material properties of rapid prototyped parts after processing. The parts developed in this project were capable of bracketing the material properties of the materials in question, and were able to do so when tested across multiple FDM machines. The results of this work were stress-strain data which indicates the behavior of the part under load, and a method for inexpensively testing the material properties of rapid prototyped parts after processing.

Cette these examine deux aspects des theories conformes des champs (TCC) en d dimensions.Sa premiere parti est dediee aux blocs conformes, des fonctions speciales qui contribuent au developpement en ondes partielles des fonctions a quatre points dans les TCC. On montre que ces blocs admettent un developpement en coordonnees polaires dont les coecients se calculent par une recurrence. Les blocs conformes sont naturellement denis sur le plan complexe : on considere alors leur restriction a l'axe r eel, an de montrer qu'ils obeissent une equation dierentielle sur ce domaine, ce qui mene a un algorithme ecace pour calculer les blocs conformes et leurs derivees pour tout d. Quelques applications au programme de bootstrap sont developpees. La seconde partie de cette these examine les perturbations d'une TCC par des operateurs pertinents. On etudie de tels ots du groupe de renormalisation en utilisant la Methode de Troncature Conforme (MTC) de Yurov et Zamolodchikov, une methode numerique qui permet de faire des calculs non-perturbatifs en theorie quantique des champs. Deux theories derentes sont considerees : le boson libre avec un terme de masse, et la theorie 4. Pour le dernier cas, les resultats de la MTC mettent en evidence la brisure de symetrie Z2. Finalement, on developpe une methode pour reduire les erreurs de troncature en ajoutant des contre-termes a l'action \nue" de la MTC, suivant des travaux anterieurs en d = 2 dimensions. / This thesis investigates two aspects of Conformal Field Theories (CFTs) in d dimensions. Its rst part is devoted to conformal blocks, special functions that arise in the partial wave expansion of CFT four-point functions. We prove that these conformal blocks admit an expansion in terms of polar coordinates and show that the expansion coecients are determined by recursion relations. Conformal blocks are naturally dened on the complex plane: we study their restriction to the real line, and show that they obey a fourth-order dierential equation there. This ODE can be used to eciently compute conformal blocks and their derivatives in general d. Several applications to the conformal bootstrap program are mentioned. The second half of this thesis investigates RG ows that are dened by perturbing a CFT by a number of relevant operators. We study such ows using the Truncated Conformal Space Approach (TCSA) of Yurov and Zamolodchikov, a numerical method that allows for controlled computations in strongly coupled QFTs. Two dierent RG ows are considered: the free scalar feld deformed by a mass term, and 4 theory. The former is used as a benchmark, in order to compare numerical TCSA results to exact predictions. TCSA results for 4 theory display spontaneous Z2 symmetry breaking at strong coupling: we study the spectrum of this theory both in the Z2-broken and preserved phase, and we compare the critical exponents governing the phase transition to known values. In a separate chapter, we show how truncation errors can be reduced by adding suitable counterterms to the bare TCSA action, following earlier work in d = 2 dimensions.

A compliant force/torque sensor for robot force control has been developed. This thesis presents methods of designing, testing, and implementing the sensor on a robotic system. The sensor uses an orthoplanar spring equipped with Hall-effect sensors to measure one component of force and two moment components. Its unique design allows for simple and cost effective manufacturing, high reliability, and compactness. The device may be used in applications where a robot must control contact forces with its environment, such as in surface cleaning tasks, manipulating doors, and removing threaded fasteners. The compliant design of the sensor improves force control performance and reduces impact forces. Sensor design considerations are discussed, followed by a discussion of the proposed design concept. Theoretical compliance and stress analysis of the orthoplanar spring is presented that allows for rapid design calculations; these calculations are validated via finite element analysis. A mechanical design method is given which uses the results of the compliance and stress analysis. Transducer design is then addressed by developing a model of the sensor. The design methods are used to design a prototype sensor which is tested to determine its instrument uncertainty. Finally, the sensor is implemented on a robotic platform to test its performance in force control.