A estabilidade do tronco é geralmente desafiada nas sessões do método Pilates. A compreensão da estabilidade/instabilidade, desafiada pela alteração de molas e dependente do nível de treinamento dos executantes, possui grande impacto no controle do tronco. Após uma revisão sistemática foi possível verificar que a principal técnica biomecânica empregada para compreender a estabilidade do tronco é a modelagem. Sendo assim, o objetivo deste estudo foi desenvolver e avaliar um modelo biomecânico para quantificar e comparar a estabilidade do tronco em dois diferentes níveis de praticantes de Pilates e em dois diferentes níveis de intensidade do exercício long stretch front do Pilates. O exercício long stretch front, criado para utilizar o powerhouse e desafiar a estabilidade do tronco, é executado no aparelho reformer na posição de prancha e consiste na extensão de ombros. O movimento foi modelado como um sistema massa-mola sendo a rigidez (K) o parâmetro de estabilidade do tronco. Como dados de entrada foram utilizadas informações cinemáticas, de câmeras infra-vermelho, cinéticas, de células de carga acopladas ao equipamento reformer, e informações antropométricas extraídas da literatura. Foram avaliados 15 praticantes avançados de Pilates e 15 iniciantes. Os indivíduos mais experientes foram mais estáveis durante o exercício do que iniciantes, F(1,28)=7,965; η2=0,22; p=0,009. A execução dos exercícios com duas molas apresentou menor rigidez do que com uma única mola, F(1,28)=67,891; η2=0,71; p<0,001. Não houve interação entre os fatores, F(1,28)=0,587; η2=0,02; p=0,450. Quando os grupos foram comparados separadamente para cada um dos níveis de dificuldade, os mais experientes (K = 272 ± 27 Nm/rad) apresentaram maior rigidez que os iniciantes (K = 171 ± 42 Nm/rad) com uma única mola, e também com o uso de duas molas, com K = 196 ± 17 Nm/rad para os executantes experientes e K = 108 ± 21 Nm/rad para os executantes iniciantes. Conclui-se que o modelo proposto, utilizando o coeficiente de rigidez, foi capaz de quantificar a estabilidade durante o exercício longh stretch front do Pilates. O modelo também identificou as diferenças entre indivíduos mais ou menos experientes, bem como quando o exercício é executado com uma ou com duas molas. / Trunk stability is usually challenged during Pilates method ’sessions. The stability/instability, generated by altering springs or by the practitioner’s experience level during a Pilates exercise, has great impact in trunk control. Following a systematic review, it was observed that modelling is the main biomechanical technique applied for understanding trunk stability. Hence, this study aimed to develop and evaluate a biomechanical model for quantifying and compare trunk stability in two different Pilates practitioners levels and two different intensities of the exercise during Pilates’ long stretch front exercise. The long stretch front exercise, created for using the powerhouse and challenging trunk stability, is performed in the reformer apparatus, keeping the trunk in the plunk position while shoulder extension is performed. The movement was modelled as a spring-mass system using stiffness (K) as the parameter to express trunk stability. Model input consisted of kinematics data, obtained from infrared cameras images, kinetic data, from load cells attached to the reformer equipment, and anthropometric data, obtained from literature. Fifteen experienced and 15 beginner Pilates practitioners, who performed ten repetitions of the exercise in two difficulty levels, with one and two springs, were evaluated. Experienced subjects were more stable during the exercise when compared to beginners F(1.28)=7.965; η2=0.22; p=0.009. The exercise performed using two springs presented a lower rigidity level when compared to one spring F(1.28)=67.891; η2=0.71; p<0.001. There was no interaction between the factors , F(1.28)=0.587; η2=0.02; p=0.450. When groups were compared separately for each difficulty level, experienced (K=272 ± 27 Nm.rad-1) presented higher rigidity than beginners (K=171 ± 42 Nm.rad-1) using one spring, and also using two springs with K=196 ± 17 Nm.rad-1 for experienced performers and K=108 ± 21 Nm.rad-1 for beginners. Concludes that the proposed model is capable of quantifying stability during the Pilates long stretch front exercise using rigidity coefficient. In addition model identifies differences between more or less experienced subjects, as well as when the exercise is performed using one or two springs.

Yes / Background: Individuals with lower-limb amputation can use running specific prostheses (RSP) that store and then return elastic energy during stance. However, it is unclear whether varying the stiffness category of the same RSP affects spring-mass behaviour during self-selected, submaximal speed running in individuals with unilateral transtibial amputation. Research question: The current study investigates how varying RSP stiffness affects limb stiffness, running performance, and associated joint kinetics in individuals with a unilateral transtibial amputation. Methods: Kinematic and ground reaction force data were collected from eight males with unilateral transtibial amputation who ran at self-selected submaximal speeds along a 15 m runway in three RSP stiffness conditions; recommended habitual stiffness (HAB) and, following 10-minutes of familiarisation, stiffness categories above (+1) and below (-1) the HAB. Stance-phase centre of mass velocity, contact time, limb stiffness’ and joint/RSP work were computed for each limb across RSP stiffness conditions. Results: With increased RSP stiffness, prosthetic limb stiffness increased, whilst intact limb stiffness decreased slightly (p

In this thesis we present a computational study of “ion crystals”, the interesting patterns in which ions arrange themselves in ion traps such as Paul and Penning traps. In ion crystals the ions are in equilibrium due to the balance of the repulsive forces between the ions and the overall tendency of the ion trap to pull ions towards the trap centre. We have carried out a detailed investigation of ion crystals in Paul traps by solving their equations of motion numerically. We also propose a model called the spring–mass model to explain the formation of ion crystals. This model is far more efficient than direct numerical simulation for predicting ion crystal structures. Finally, we demonstrate that there is a power law relating distance of an ion from the trap centre in ion crystals to the applied RF voltage amplitude.

We present a novel control strategy for running which is robust to disturbances, and makes excellent use of passive dynamics for energy economy. The motivation for our control strategy is based on observations of animals, which are able to economically walk and run over varying terrain and ground dynamics. It is well-known that steady-state animal running can be approximated by spring-mass models, but these passive dynamic models describe only steady-state running and are sensitive to disturbances that animals can accommodate. While animals rely on their passive dynamics for energy economy, they also incorporate active control for disturbance rejection. The same approach can be used for spring-mass walking and running, but an active controller is needed that interferes minimally with the passive dynamics of the system. We demonstrate, in simulation, how force control combined with a leg spring stiffness tuned for the desired hopping frequency provides robustness to disturbances on a model for robot hopping, while maintaining the energy economy of a completely passive system during steady-state operation. Our strategy is promising for robotics applications, because there is a clear distinction between the passive dynamic behavior of the model and the active controller, it does not require sensing of the environment, and it is based on a sound theoretical background that is compatible with existing high-level controllers for ideal spring-mass models. / Graduation date: 2012

京都大学 / 0048 / 新制・課程博士 / 博士(人間・環境学) / 甲第18353号 / 人博第666号 / 新制||人||160(附属図書館) / 25||人博||666(吉田南総合図書館) / 31211 / 京都大学大学院人間・環境学研究科共生人間学専攻 / (主査)准教授 神﨑 素樹, 教授 森谷 敏夫, 准教授 久代 恵介, 教授 小田 伸午 / 学位規則第4条第1項該当 / Doctor of Human and Environmental Studies / Kyoto University / DFAM

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In vibration-based damage detection in structures, often changes in the dynamic properties such as natural frequencies, modeshapes, and derivatives of modeshapes are used to identify the damaged elements. If only a partial list of natural frequencies is known, optimization methods may need to be used to identify the damage. In this research, the algorithm proposed by Podlevskyi & Yaroshko (2013) is used to determine the stiffness distribution in shear building models. The lateral load resisting elements are presented as a single equivalent spring, and masses are lumped at floor levels. The proposed method calculates stiffness values directly, i.e., without optimization, from the known partial list of natural frequency data and mass distribution. It is shown that if the number of stories with reduced stiffness is smaller than the number of known natural frequencies, the stories with reduced stiffnesses can be identified. Numerical studies on building models with two stories and four stories are used to illustrate the solution method. Effect of error or noise in given natural frequencies on stiffness estimates and, conversely, sensitivity of natural frequencies to changes in stiffness are studied using 7-, 15-, 30-, and 50-story numerical models. From the studies, it is learnt that as the number of stories increases, the natural frequencies become less sensitive to stiffness changes. Additionally, eight laboratory experiments were conducted on a five-story aluminum structural model. Ten slender columns were used in each story of the specimen. Damage was simulated by removing columns in one, two, or three stories. The method can locate and quantify the damage in cases presented in the experimental studies. It is also applied to a 1/3 scaled 18-story steel moment frame building tested on an earthquake simulator (Suita et al., 2015) to identify the reduction in the stiffness due to fractures of beam flanges. Only the first two natural frequencies are used to determine the reductions in the stiffness since the third mode of the tower is torsional and no reasonable planar spring-mass model can be developed to present all of the translational modes. The method produced possible cases of the softening when the damage was assumed to occur at a single story.

Every movement has a goal. For reaching, the goal is to move the hand to a specific location. For locomotion, however, goals for each step cycle are unclear and veiled by the automatic nature of lower limb control. What mechanical variables does the nervous system "care" about during locomotion? Abundant evidence from the biomechanics literature suggests that the force generated on the ground, or endpoint force, is an important task variable during hopping and running. Hopping and running are called bouncing gaits for the reason that the endpoint force trajectory is like that of bouncing on a pogo stick. In this work, I captured kinematics and kinetics of human bouncing gaits, and tested whether structure in the inherent step-to-step variability is consistent with control of endpoint force. I found that joint torques covary from step to step to stabilize only peak force. When two limbs are used to generate force on the ground at the same time, individual forces of the limbs are not stabilized, but the total peak force is stabilized. Moreover, passive dynamics may be exploited during forward progression. These results suggest that the number of kinetic goals is minimal, and this simple control scheme involves goals for discrete times during the gait cycle. Uncovering biomechanical goals of locomotion provides a functional context for understanding how complex joints, muscles, and neural circuits are coordinated.

CoordenaÃÃo de AperfeiÃoamento de Pessoal de NÃvel Superior / A animaÃÃo de tecido vem sendo estudada abundantemente nas Ãltimas dÃcadas por haver demanda na indÃstria do entretenimento bem como no comÃrcio eletrÃnico de roupas. Esse tipo de animaÃÃo, na maioria das vezes, à feita com base em simulaÃÃo fÃsica, havendo muito gasto computacional. Esse trabalho tenta usufruir de vÃrios modelos para diminuir esse gasto. à feito uma modelagem do tecido com uma malha triangular e usa-se um modelo massa-mola-amortecedor para simular as forÃas entre as partÃculas, que sÃo os vÃrtices dessa malha. Dependendo da disposiÃÃo do modelo do tecido e dos objetos da cena, sÃo detectadas colisÃes entre eles. A malha à discretizada ou simplificada, levando em consideraÃÃo a compressÃo, a colisÃo e a curvatura das molas, para que seja usada uma malha boa em cada passo ao longo da animaÃÃo. Portanto, o objetivo principal desse trabalho à estudar o comportamento do tecido utilizando o modelo de remalhamento para adaptar essa malha. / In the last decades, cloth animation has been the focus of much research, due to demands from the entertainment industry and from e-commerce. That type of animation is most often the result of a physics-based simulation and has a great computational cost. This work investigates how to reduce the computational cost of the simulation, by refining the mesh only in regions that need a fine level of detail. The fabric model consists of a triangular mesh and uses a spring-mass-damper system to compute the forces among the particles, which are located at the meshâs vertices. The collision detection depends on the arrangement of the cloth model and the objects in the scene. The mesh is refined or simplified, taking into account the spring compression, collision and curvature, so the simulation uses a better mesh every time step. Therefore, this workâs main objective is to study the dynamic behavior of cloth, using a remeshing procedure in order to adapt the mesh.

This thesis deals with the design of two-axis displacement-amplifying compliant mechanisms (DaCMs) using topology optimization. The two-axis compliant mechanisms considered here are XY positioners and two-axis inertial sensors. A building block approach, with several single-axis DaCMs as building blocks, is used to conceive designs of compliant platforms that provide two orthogonal and independent movement of a common platform. Spring-mass-lever (SML) models of these designs are developed to simplify the analysis and design of the complicated arrangements of building blocks. The XY positioners designed in this work have perfectly de-coupled motion without compromising on the frequency; the best design of the stage has a displacement amplification of five resulting in the enhanced range of 4.2 % of the mechanism size–a significant improvement from the 1.67 %, the maximum range of the designs reported so far. Nearly 100% improvement is observed in the sensitivity of the two-axis accelerometer as compared with an existing design that occupied the same area. Multiple prototypes of XY positioners were fabricated on polypropylene sheets using CNC machining; and on spring steel and aluminium using wire-cut electro discharge machining. Mask layouts for two-layer two-axis accelerometers are designed for micro-fabrication using reactive ion etching and wafer bonding.