Mechanical design optimization for multi-finger haptic devices applied to virtual grasping manipulation

This paper describes the design of a modular multi-finger haptic device for virtual object manipulation. Mechanical structures are based on one module per finger and can be scaled up to three fingers. Mechanical configurations for two and three fingers are based on the use of one and two redundant axes, respectively. As demonstrated, redundant axes significantly increase workspace and prevent link collisions, which is their main asset with respect to other multi-finger haptic devices. The location of redundant axes and link dimensions have been optimized in order to guarantee a proper workspace, manipulability, force capability, and inertia for the device. The mechanical haptic device design and a thimble adaptable to different finger sizes have also been developed for virtual object manipulation.

Modelling of Topographic Irregularities for Seismic Site Response

Seismic evaluation methodology is applied to an existing viaduct in the south of Spain, near Granada, which is a medium seismicity region. The influence of both geology and topography in the spatial variability of ground motion are studied as well as seismic hazard analysis and ground motion characterization. Artificial hazard-consistent ground motion records are synthesised applying seismic hazard analysis and site effects are estimated through a diffraction study. Direct BEM is used to calculate the valley displacement response to vertically propagating SV waves and transfer functions are generated allowing the transformation of free field motion to motion at each support. A closed formulae is used to estimate these transfer function. Finally, the results obtained are compared.

Bare-tether cathodic contact through thermoionic emission by low work-function materials

A new material, C12A7 : electride, which might present a work function as low as 0.6 eV and moderately high temperature stability, was recently proposed as coating for floating bare tethers. Arising from heating under space operation, current is emitted by thermionic emission along a thus coated cathodic segment. A preliminary study on the space-charge-limited (SCL) double layer in front of the cathodic segment is presented using Langmuir’s SCL electron current between cylindrical electrodes and orbital-motion-limited ion-collection sheath. A detailed calculation of current and bias profiles along the entire tether length is carried out with ohmic effects and the transition from SCL to full Richardson-Dushman emission included. Analysis shows that in the simplest drag mode, under typical orbital and tether conditions, thermionic emission leads to a short cathodic section and may eliminate the need for an active cathodic device and its corresponding gas feed requirements and power subsystem, which results in a truly “propellant-less” tether system for such basic applications as de-orbiting low earth orbit satellites.

Adaptive scheme for Accurate orbit propagation

Two extensions of the fast and accurate special perturbation method recently developed by Peláez et al. are presented for respectively elliptic and hyperbolic motion. A comparison with Peláez?s method and with the very efficient Stiefel- Scheifele?s method, for the problems of oblate Earth plus Moon and continuous radial thrust, shows that the new formulations can appreciably improve the accuracy of Peláez?s method and have a better performance of Stiefel-Scheifele?s method. Future work will be to include the two new formulations and the original one due to Peláez into an adaptive scheme for highly accurate orbit propagation

A 3D multi-objective optimization planning algorithm for wireless sensor networks

The complexity of planning a wireless sensor network is dependent on the aspects of optimization and on the application requirements. Even though Murphy's Law is applied everywhere in reality, a good planning algorithm will assist the designers to be aware of the short plates of their design and to improve them before the problems being exposed at the real deployment. A 3D multi-objective planning algorithm is proposed in this paper to provide solutions on the locations of nodes and their properties. It employs a developed ray-tracing scheme for sensing signal and radio propagation modelling. Therefore it is sensitive to the obstacles and makes the models of sensing coverage and link quality more practical compared with other heuristics that use ideal unit-disk models. The proposed algorithm aims at reaching an overall optimization on hardware cost, coverage, link quality and lifetime. Thus each of those metrics are modelled and normalized to compose a desirability function. Evolutionary algorithm is designed to efficiently tackle this NP-hard multi-objective optimization problem. The proposed algorithm is applicable for both indoor and outdoor 3D scenarios. Different parameters that affect the performance are analyzed through extensive experiments; two state-of-the-art algorithms are rebuilt and tested with the same configuration as that of the proposed algorithm. The results indicate that the proposed algorithm converges efficiently within 600 iterations and performs better than the compared heuristics.

La metáfora. Herramienta característica de renovación arquitectónica tras el movimiento moderno

Esta tesis estudia el papel de la metáfora como instrumento arquitectónico en el debate y las propuestas para superar la ortodoxia de la arquitectura moderna a partir de mediados del siglo XX. En arquitectura, la utilización del procedimiento que constituye la metáfora se apoya en una consideración semántica de la arquitectura y se ha usado constantemente a lo largo de la historia para desarrollar nuevas propuestas, basándose en la comparación con modelos conocidos. En este trabajo se examina la notable presencia que adquirió este instrumento en las propuestas críticas a la arquitectura moderna ortodoxa, debido a la importancia que tuvieron los aspectos semánticos en el debate sobre la continuidad y vigencia de los postulados de la arquitectura moderna. Con este estudio se ha indagado sobre las razones y la frecuencia con las que aquellos arquitectos que adoptaron una actitud crítica hacia la arquitectura moderna se refirieron a las relaciones metafóricas en sus propuestas alternativas. Para mostrar cómo las metáforas formaron parte de los mecanismos de cambio de la arquitectura en este periodo, recuperando un mayor potencial creativo para abordar los proyectos arquitectónicos, se han estudiado una serie de ejemplos pertinentes y relevantes. En cada uno de los capítulos se han analizado las objeciones más importantes que fueron planteadas frente a la arquitectura moderna por un arquitecto o grupo de arquitectos, seleccionados entre aquéllos que tomaron parte en este debate, y se estudia la inclusión de la metáfora en las alternativas que propusieron en cada caso. Además de una actitud crítica con la arquitectura moderna, todos los arquitectos seleccionados comparten una consideración semántica de la arquitectura y han expuesto sus ideas y posturas tanto en obras proyectadas y construidas, como en escritos o comentarios sobre su manera de entender y proyectar arquitectura. Esta doble producción ha permitido analizar, comparativamente, el papel de la metáfora en sus enfoques y propuestas críticas y en la realización de sus obras como alternativas a las mismas. Al mismo tiempo, la investigación profundiza en el conocimiento de la utilización de la metáfora como herramienta arquitectónica. A través del recorrido por las distintas maneras de entender este instrumento que pueden observarse en algunos de los arquitectos de la segunda mitad del siglo XX, se exponen tanto las posibilidades como los aspectos más críticos de la utilización de la metáfora en arquitectura. La variada utilización de la noción de metáfora en arquitectura se ve reflejada en las diversas consideraciones que hacen de la misma los arquitectos estudiados. La tesis se ha ocupado de distinguir cada uno de estos enfoques, haciéndose eco de la pluralidad con la que puede abordarse el concepto de metáfora de manera general y en arquitectura en particular. Así, algunos arquitectos del Team 10, la utilizan como un instrumento de ampliación y renovación semántica de la arquitectura moderna, que propone una síntesis de lo viejo y lo nuevo. Para Robert Venturi, se trata de un recurso con capacidad de persuadir y recrear, renovando semánticamente la arquitectura. Charles Jencks considera que es un procedimiento semántico esencial de la arquitectura, olvidado por los arquitectos modernos, cuya recuperación supone un rasgo diferencial de la arquitectura posmoderna respecto a la moderna. Para Aldo Rossi, es una manera de materializar las relaciones analógicas que constituyen su propuesta para proyectar una arquitectura de racionalismo exaltado frente a un racionalismo convencional. Peter Eisenman la valora porque inventa otras arquitecturas diferentes a las preconcebidas anteriormente, a pesar de que rechaza su capacidad representativa y expresiva. Rafael Moneo la utiliza para contraponerse al determinismo, como instrumento de innovación de la forma arquitectónica que construye una dinámica entre la contingencia y la necesidad. Finalmente, para Frank Gehry supone un procedimiento creativo y subjetivo con el que enfrentarse tanto a la arquitectura moderna como a la posmoderna con una arquitectura nueva y abierta a referencias inusuales. De esta manera, a través de los distintos capítulos, el estudio pretende componer un mosaico de posturas que manifieste los vínculos y las diferencias existentes entre estos arquitectos con relación a los temas estudiados: crítica y alternativas a la arquitectura moderna, semántica de la arquitectura, metáfora y otros conceptos relacionados. A su vez, la aparición continuada de la metáfora en los diferentes capítulos, y de los temas con los que está relacionada, manifiesta el protagonismo de esta herramienta arquitectónica en las propuestas de evolución y cambio de la arquitectura del periodo estudiado. ABSTRACT This thesis studies the role of the metaphor as an architectural tool in the debate and proposals to overcome the orthodoxy of modern architecture that took place since the middle part of the Twentieth Century. In architecture, the usage of the process which the metaphor constitutes is based in a semantic consideration of architecture and historically it has been used many times to develop new proposals, always based in the comparison with known models. This work examines the significant presence that this tool acquired in the proposals critical with orthodox modern architecture, due to the importance that the semantic aspects had in the debate on the continuity and validity of modern architecture’s postulates. This study also looks into the motives and frequency that those architects which adopted a critical attitude towards modern architecture alluded to the metaphorical relations in their alternative proposals. To demonstrate how during that period metaphors were imbued in the mechanisms of change of architecture, recovering a higher creative potential to approach architectural projects, a series of pertinent and relevant examples are studied. Each chapter examines the most important objections on modern architecture made by an architect or group of architects, selected among those who participated in this debate, and studies the inclusion of metaphor in the alternatives proposed in each case. Besides a critical attitude towards modern architecture, all the selected architects share a semantic consideration of architecture and have exposed their ideas and postures through projected and finalized works as in writings or commentaries on their way of understanding and projecting architecture. This double production allowed to analyse, in a comparatively manner, the role of metaphor in their approaches and critical proposals as in the execution of their works. At the same time, the research conducted further analyses the body of knowledge on the usage of metaphor as an architectural tool. By looking over the different ways some of the architects of the second half of the Twentieth Century understood this tool, both the possibilities and the most critical aspects of the usage of the metaphor in architecture can be exposed. The various usages of the notion of metaphor in architecture are reflected in the multiple considerations done about it by the selected architects. This thesis differentiates each one of those approaches, echoing the plurality with which the concept of metaphor can be addressed both in broader terms and more particularly in architecture. In this sense, some architects of Team 10 used it as a mean of semantic extension and renewal of modern architecture, proposing a synthesis between the old and the new. For Robert Venturi it is a resource with the capacity to persuade and recreate, semantically renewing architecture. Charles Jencks considers it an essential semantic procedure of architecture, forgotten by the modern architects, and which recovery represents a differential trait of post-modern architecture in relation to modern architecture. For Aldo Rossi, is a way of materializing the analogical relations which represent his proposal to project architecture of exalted rationalism as opposed to a more conventional rationalism. Peter Eisenman values it because it invents other architectures different from the preconceived before, even if he refuses its representational and expressive capacity. Rafael Moneo uses it to counter determinism, as an innovation tool of the architectonical form which generates dynamics between contingency and necessity. Finally, for Frank Gehry it supposes a creative and subjective process to face both modern architecture and post-modern architecture with a new architecture open to unusual references. As such, through its different chapters, this study aims to compose a mosaic of postures which expresses the links and the differences between those architects in relation to the topics examined: criticism and alternatives to modern architecture, semantics of architecture, metaphor and other related concepts. At the same time, the continuous presence of the metaphor in the different chapters, and of the issues it relates to, shows the importance of this tool in the proposals of evolution and change of architecture in the period considered.

Developing transferable skills through academic motivation activities

The purpose of this study is to work out how a clear and motivated task goal set for the students can develop several skills that are not only useful in their specific academic contexts but also serve to reinforce links and cooperation with the labor market. The following research on skills was taken during one academic year. The students collected advertisements likely to be selected in a near future by themselves as possibilities to apply for a job. The advertisements selected were 120, and all of them were published on the internet either in jobs links or located by the students themselves in the web-practices of their choice. All the advertisements chosen by the students provided us with a skill list focused on architectural profiles. To conclude, academic research skills versus future motivation jobs positions are fruitful paths to conduct successful students´response at job interviews.

Long-term dynamics of fast rotating tethers around planetary satellites

We derive a semi-analytic formulation that enables the study of the long-term dynamics of fast-rotating inert tethers around planetary satellites. These equations take into account the coupling between the translational and rotational motion, which has a non-negligible impact on the dynamics, as the orbital motion of the tether center of mass strongly depends on the tether plane of rotation and its spin rate, and vice-versa. We use these governing equations to explore the effects of this coupling on the dynamics, the lifetime of frozen orbits and the precession of the plane of rotation of the tether.

On the application of meshfree methods to the nonlinear dynamics of multibody systems

Esta tesis propone una completa formulación termo-mecánica para la simulación no-lineal de mecanismos flexibles basada en métodos libres de malla. El enfoque se basa en tres pilares principales: la formulación de Lagrangiano total para medios continuos, la discretización de Bubnov-Galerkin, y las funciones de forma libres de malla. Los métodos sin malla se caracterizan por la definición de un conjunto de funciones de forma en dominios solapados, junto con una malla de integración de las ecuaciones discretas de balance. Dos tipos de funciones de forma se han seleccionado como representación de las familias interpolantes (Funciones de Base Radial) y aproximantes (Mínimos Cuadrados Móviles). Su formulación se ha adaptado haciendo sus parámetros compatibles, y su ausencia de conectividad predefinida se ha aprovechado para interconectar múltiples dominios de manera automática, permitiendo el uso de mallas de fondo no conformes. Se propone una formulación generalizada de restricciones, juntas y contactos, válida para sólidos rígidos y flexibles, siendo estos últimos discretizados mediante elementos finitos (MEF) o libres de malla. La mayor ventaja de este enfoque reside en que independiza completamente el dominio con respecto de las uniones y acciones externas a cada sólido, permitiendo su definición incluso fuera del contorno. Al mismo tiempo, también se minimiza el número de ecuaciones de restricción necesarias para la definición de uniones realistas. Las diversas validaciones, ejemplos y comparaciones detalladas muestran como el enfoque propuesto es genérico y extensible a un gran número de sistemas. En concreto, las comparaciones con el MEF indican una importante reducción del error para igual número de nodos, tanto en simulaciones mecánicas, como térmicas y termo-mecánicas acopladas. A igualdad de error, la eficiencia numérica de los métodos libres de malla es mayor que la del MEF cuanto más grosera es la discretización. Finalmente, la formulación se aplica a un problema de diseño real sobre el mantenimiento de estructuras masivas en el interior de un reactor de fusión, demostrando su viabilidad en análisis de problemas reales, y a su vez mostrando su potencial para su uso en simulación en tiempo real de sistemas no-lineales. A new complete formulation is proposed for the simulation of nonlinear dynamic of multibody systems with thermo-mechanical behaviour. The approach is founded in three main pillars: total Lagrangian formulation, Bubnov-Galerkin discretization, and meshfree shape functions. Meshfree methods are characterized by the definition of a set of shape functions in overlapping domains, and a background grid for integration of the Galerkin discrete equations. Two different types of shape functions have been chosen as representatives of interpolation (Radial Basis Functions), and approximation (Moving Least Squares) families. Their formulation has been adapted to use compatible parameters, and their lack of predefined connectivity is used to interconnect different domains seamlessly, allowing the use of non-conforming meshes. A generalized formulation for constraints, joints, and contacts is proposed, which is valid for rigid and flexible solids, being the later discretized using either finite elements (FEM) or meshfree methods. The greatest advantage of this approach is that makes the domain completely independent of the external links and actions, allowing to even define them outside of the boundary. At the same time, the number of constraint equations needed for defining realistic joints is minimized. Validation, examples, and benchmarks are provided for the proposed formulation, demonstrating that the approach is generic and extensible to further problems. Comparisons with FEM show a much lower error for the same number of nodes, both for mechanical and thermal analyses. The numerical efficiency is also better when coarse discretizations are used. A final demonstration to a real problem for handling massive structures inside of a fusion reactor is presented. It demonstrates that the application of meshfree methods is feasible and can provide an advantage towards the definition of nonlinear real-time simulation models.

La ciudad editada: de Las Vegas a Nueva York (1972-1978): Venturi / Scott Brown / Koolhaas

Si hubiese un denominador común entre todas las artes en lo que ha venido llamándose postmodernidad, éste tendría mucho que ver con el final del origen de la obra. Desde la literatura y la música hasta las artes plásticas y la arquitectura, la superación de la modernidad ha estado caracterizada por la sustitución del concepto de creación por el de intervención artística, o lo que es lo mismo, la interpretación de lo que ya existe. A principios del siglo XX los conceptos modernos de creación y origen implicaban tener que desaprender y olvidar todo lo anterior con el ánimo de partir desde cero; incluso en un sentido material Mies sugería la construcción literal de la materia y su movimiento de acuerdo a unas leyes. A partir de la segunda mitad de siglo los planteamientos historicistas empezaron a surgir como reacción ante la amnesia y la supuesta originalidad de los modernos. En este contexto surgen los libros Learning from Las Vegas, 1972 y Delirious New York, 1978, ambos deudores en muchos aspectos con el anterior libro de Venturi, Complexity and Contradiction in Architecture, 1966. Estos dos libros sobre ciudades, alejándose decididamente de las tendencias historicistas de la época, proponían utilizar el análisis crítico de la realidad existente como vehículo para la teoría y el proyecto de manera simultánea, convirtiéndose indirectamente en Manifiestos. Si en un primer momento Venturi, Rossi y otros planteaban acabar con los límites formales establecidos por la modernidad, así como por cualquiera de los cánones anteriores, tomando la totalidad de la obra construida como sistema de referencia, - al igual que hiciera Eliot en literatura, - los libros de Las Vegas y Nueva York sugerían directamente borrar los límites de la propia disciplina, llegando a poner en duda ¿Qué puede ser considerado arquitectura? Sin embargo, debido precisamente a la ausencia total de límites y a la inmensidad del sistema referencial planteado, “todo puede ser arquitectura”, como apuntaba Hans Hollein en 1968, los libros proponen al mismo tiempo definir el campo de actuación de cada cual de manera individual. Los escritos sobre Las Vegas y Nueva York suponen por un lado la eliminación de los limites disciplinares y por otro, la delimitación de ámbitos de trabajo concretos para sus autores: los propios de cada una de las ciudades interpretadas. La primera parte de la Tesis, Lecciones, se ocupa del necesario proceso de aprendizaje y experimentación previo a la acción crítica propiamente dicha. Los arquitectos contemporáneos necesitan acumular material, conocimiento, documentación, experiencias... antes de lanzarse a proponer mediante la crítica y la edición; y al contrario que ocurría con los modernos, cuanto más abundante sea ese bagaje previo más rica será la interpretación. Las ciudades de Roma, Londres y Berlín se entienden por tanto como experiencias capaces de proporcionar a Venturi, Scott Brown y Koolhaas respectivamente, sus “personales diccionarios”, unas interminables imaginerías con las que posteriormente se enfrentarían a los análisis de Las Vegas y Nueva York. La segunda parte, Críticas, se centra en la producción teórica en sí: los dos libros de ciudades analizados en estrecha relación con el Complexity and Contradiction. El razonamiento analógico característico de estos libros ha servido de guía metodológica para la investigación, estableciéndose relaciones, no entre los propios escritos directamente, sino a través de trabajos pertenecientes a otras disciplinas. En primer lugar se plantea un importante paralelismo entre los métodos de análisis desarrollados en estos libros y los utilizados por la crítica literaria, observando que si el new criticism y el nuevo periodismo sirvieron de guía en los escritos de Venturi y Scott Brown, la nouvelle critique y su propuesta de identificación poética fueron el claro referente de Koolhaas al abordar Nueva York. Por otro lado, la relevancia ganada por la actividad de comisariado artístico y la aparición de la figura del curator, como autoridad capaz de utilizar la obra de arte por encima de las intenciones de su propio autor, sirve, al igual que la figura del editor, como reflejo de la acción transformadora y de apropiación llevada a cabo tanto en Learning from Las Vegas, como en Delirious New York. Por último y a lo largo de toda la investigación las figuras de Bergson y Baudelaire han servido como apoyo teórico. A través de la utilización que de sus ideas hicieron Venturi y Koolhaas respectivamente, se ha tratado de mostrar la proximidad de ambos planteamientos desde un punto de vista ideológico. La Inclusión propuesta por Venturi y la ironía utilizada por Koolhaas, la contradicción y la paradoja, no son sino el reflejo de lógicas que en ambos casos reaccionan al mismo tiempo contra idealismo y materialismo, contra modernidad y antimodernidad, en un continuo intento de ser lo uno y lo otro simultáneamente. ABSTRACT If there was a common denominator among all the arts in what has been called postmodernism, it would have much to do with the end of the origin of the artwork. From literature and music to fine arts and architecture, overcoming modernity has been characterized by replacing the concept of artistic creation by the one of intervention, in other words, the interpretation of what already exists. In the early twentieth century modern concepts of creation and origin involved unlearning and forgetting everything before with the firm intention of starting from scratch. Even in a material sense Mies suggested the literal construction of matter and its motion according to laws. From the mid-century historicist approaches began to emerge in response to the amnesia and originality alleged by moderns. In this context appeared the books Learning from Las Vegas, 1972 and Delirious New York, 1978, both debtors in many respects to the previous book by Venturi, Complexity and Contradiction in Architecture, 1966. These two books on cities, which broke away decidedly with the historicist trends of the time, proposed using critical analysis of the existing reality as a vehicle for theory and projecting at the same time, indirectly becoming manifests. If at first Venturi, Rossi and others pose to erase the formal limits set by modernity, as well as any of the canons before, taking the entire work built as a reference system, - as did Eliot in literature - the books on Las Vegas and New York proposed directly erasing the boundaries of the discipline itself, coming to question what could be considered architecture? However, and precisely because of the absence of limits and the immensity of the established framework, - “everything could be architecture” as Hans Hollein pointed in 1968, - the books suggested at the same time the definition of a field of action for each one individually. The cities of Las Vegas and New York represented on the one hand the elimination of disciplinary limits and on the other, the delimitation of specific areas of work to its authors: Those on each of the cities interpreted. The first part of the thesis, Lessons, attend to the necessary process of learning and experimentation before the critical action itself. Contemporary architects need to accumulate material, knowledge, information, experiences... before proposing through criticism and editing; and unlike happened with moderns, the most abundant this prior baggage is, the richest will be the interpretation. Rome, London and Berlin are therefore understood as experiences capable of providing Venturi, Scott Brown and Koolhaas respectively, their “personal dictionaries”, interminable imageries with which they would later face the analysis of Las Vegas and New York. The second part, Critiques, focuses on the theoretical production itself: the two books on both cities analyzed closely with the Complexity and Contradiction. The analogical reasoning characteristic of these books has served as a methodological guide for the research, establishing relationships, not directly between the writings themselves, but through works belonging to other disciplines. First, an important parallel is set between the methods of analysis developed in these books and those used by literary criticism, noting that if the new criticism and new journalism guided Venturi and Scott Brown´s writings, the nouvelle critique and its poetic identification were clear references for Koolhaas when addressing New York. On the other hand, the relevance gained by curating and the understanding of the figure of the curator as an authority capable to use artworks above the intentions of their authors, like the one of the Editor, reflects the appropriation and processing actions carried out both in Learning from Las Vegas, and Delirious New York. Finally and over all the research Bergson and Baudelaire figures resonate continuously. Through the use of their ideas done by Venturi and Koolhaas respectively, the research has tried to show the proximity of both approaches from an ideological point of view. Inclusion, as posed by Venturi and irony, as used by Koolhaas, contradiction and paradox are reflections of the logic that in both cases allow them to react simultaneously against idealism and materialism, against modernism and anti-modernism.