Putting the feel in ’look and feel‘

Haptic devices are now commercially available and thus touch has become a potentially realistic solution to a variety of interaction design challenges. We report on an investigation of the use of touch as a way of reducing visual overload in the conventional desktop. In a two-phase study, we investigated the use of the PHANToM haptic device as a means of interacting with a conventional graphical user interface. The first experiment compared the effects of four different haptic augmentations on usability in a simple targeting task. The second experiment involved a more ecologically-oriented searching and scrolling task. Results indicated that the haptic effects did not improve users performance in terms of task completion time. However, the number of errors made was significantly reduced. Subjective workload measures showed that participants perceived many aspects of workload as significantly less with haptics. The results are described and the implications for the use of haptics in user interface design are discussed

Railway overhead contact wire monitoring system by means of FBG sensors

Safety of infrastructures represents one of the most significant concerns for governments and service providers to preserve people's well-being. One of the main ways to keep in safe facilities (buildings, bridges, railways, etc.) involves the use of monitoring sensor systems in charge of measuring critical operating conditions. Those measurements together with periodical maintenance, contribute to minimize potential risks that the infrastructure faces. The paper aims at designing, developing, and testing a monitoring system for mechanical stresses acting on the overhead contact wire (OCW) to ensure the operational safety of the railway network. In this regard, the paper proposes two Fiber Bragg Grating (FBG) sensors-based solutions, relying on the ability of these sensors to allow real-time and continuous data acquisition. The first one consists in a polyimide-coated sensor bonded on an OCW clamp, the second one is a copper-coated sensor hanging between the two separated halves of an OCW clamp. Significant results have been obtained mechanically testing both solutions, trying to simulate the operative conditions

Improvement of control and analysis techniques of a SPM model

Bakalářská práce se zabývá zdokonalováním výukového modelu mikroskopu atomárních sil (AFM). Součástí práce je rešerše stávajících analogii mezi makroskopickými jevy a fenomény spojenými s mikroskopii rastrovací sondou. Dále byla vybrána vhodná analogie, která byla následně implementována do již existujícího modelu mikroskopu atomárních sil. Do modelu byl integrován i jednodeskový počítač, který zajistí ovládání i bez nutnosti připojení externího počítače. Na závěr byly vyhodnoceny vlastnosti použité sondy a analogie mezi modelem a skutečnými mikroskopy atomárních sil.This Bachelor Thesis is focused on development of a model of an atomic force microscope (AFM). First part of the thesis is research of already existing analogies between macroscopic phenomena and phenomena connected to scanning probe microscopy. A suitable analogy was chosen and implemented into an existing AFM model. A single-board computer was integrated into the model to enable control without connecting an external computer. In final chapters, probe behaviour and analogies between the model and real atomic force microscopes are discussed.

Vertical ship motions in shallow water

Bibliography: pages 124-135.With the increase in ship sizes, there has been an increased interest in the prediction of ship motions in shallow water, where the possibility of grounding becomes a problem. Theoretical equations governing the ship's motions have been formulated involving various hydrodynamic coefficients. In this thesis these coefficients have been found experimentally for a range of water depths and wave periods. The methods for solving the equations of motion theoretically are introduced and discussed. The equations of motion are solved using the coefficients, found experimentally, to give results in the form of motion response amplitude operators. These are compared against other authors' results derived either theoretically or experimentally. It was found that the hydrodynamic coefficients increase rapidly with decrease in water depth. Relatively good agreement between the empirical results of this thesis and results of other authors would indicate that the theoretical formulae do represent the coefficients to which they are claimed to approximate, for at least the case of zero or low forward speeds

Design and Evaluation of Pediatric Gait Rehabilitation Robots

Gait therapy methodologies were studied and analyzed for their potential for pediatric patients. Using data from heel, metatarsal, and toe trajectories, a nominal gait trajectory was determined using Fourier transforms for each foot point. These average trajectories were used as a basis of evaluating each gait therapy mechanism. An existing gait therapy device (called ICARE) previously designed by researchers, including engineers at the University of Nebraska-Lincoln, was redesigned to accommodate pediatric patients. Unlike many existing designs, the pediatric ICARE did not over- or under-constrain the patient’s leg, allowing for repeated, comfortable, easily-adjusted gait motions. This design was assessed under clinical testing and deemed to be acceptable. A gait rehabilitation device was designed to interface with both pediatric and adult patients and more closely replicate the gait-like metatarsal trajectory compared to an elliptical machine. To accomplish this task, the nominal gait path was adjusted to accommodate for rotation about the toe, which generated a new trajectory that was tangent to itself at the midpoint of the stride. Using knowledge of the bio-mechanics of the foot, the gait path was analyzed for its applicability to the general population. Several trajectory-replication methods were evaluated, and the crank-slider mechanism was chosen for its superior performance and ability to mimic the gait path adequately. Adjustments were made to the gait path to further optimize its realization through the crank-slider mechanism. Two prototypes were constructed according to the slider-crank mechanism to replicate the gait path identified. The first prototype, while more accurately tracing the gait path, showed difficulty in power transmission and excessive cam forces. This prototype was ultimately rejected. The second prototype was significantly more robust. However, it lacked several key aspects of the original design that were important to matching the design goals. Ultimately, the second prototype was recommended for further work in gait-replication research. Advisor: Carl A. Nelso

Vertical ship motions in shallow water

Bibliography: pages 124-135.With the increase in ship sizes, there has been an increased interest in the prediction of ship motions in shallow water, where the possibility of grounding becomes a problem. Theoretical equations governing the ship's motions have been formulated involving various hydrodynamic coefficients. In this thesis these coefficients have been found experimentally for a range of water depths and wave periods. The methods for solving the equations of motion theoretically are introduced and discussed. The equations of motion are solved using the coefficients, found experimentally, to give results in the form of motion response amplitude operators. These are compared against other authors' results derived either theoretically or experimentally. It was found that the hydrodynamic coefficients increase rapidly with decrease in water depth. Relatively good agreement between the empirical results of this thesis and results of other authors would indicate that the theoretical formulae do represent the coefficients to which they are claimed to approximate, for at least the case of zero or low forward speeds

Pantograph-Catenary Dynamic Models and their Implementation in Hardware-in-the-Loop Tests

Tesis por compendio[ES] Existe una extensa red de líneas ferroviarias electrificadas en todo el mundo. La mayoría de ellas utilizan líneas aéreas de contacto o catenarias para suministrar electricidad a los trenes. Las catenarias son estructuras de cables ubicadas sobre las vías ferroviarias, diseñadas para ser contactadas por los pantógrafos que se encuentran sobre la parte superior de los trenes. El correcto funcionamiento del sistema requiere un alto nivel de exigencia, especialmente a alta velocidad, cuando la continuidad del contacto se ve comprometida. La herramienta más empleada el sistema pantógrafo-catenaria es el uso de simulaciones numéricas. En particular, el Método de los Elementos Finitos (MEF) es la técnica más extendida para modelar y simular la interacción dinámica del pantógrafo con la catenaria. Después de la etapa de simulación, el pantógrafo y la catenaria tienen que ser testados mediante ensayos experimentales en vía. Sin embargo, existe una alternativa que puede reemplazar esos ensayos con una reducción significativa de costes. Dicha alternativa, llamada Hardware In the Loop (HIL), permite testar pantógrafos en el laboratorio mediante un banco de ensayos que emula la interacción con una catenaria virtual. Diferentes grupos de investigación han implementado HIL; sin embargo, en todos los intentos se han adoptado soluciones de compromiso, lo que demuestra el reto que supone la aplicación de HIL. Esta Tesis pretende avanzar en el campo de ensayos HIL, impulsando las capacidades de la técnica y solventando algunas de las limitaciones encontradas en la literatura. Para ello se proponen dos tipos diferentes de modelos de catenaria para su uso en ensayos HIL. El primero es un modelo analítico basado en un cable tensado con perfil geométrico periódico que proporciona la solución estacionaria del sistema. Este enfoque reduce la complejidad de la catenaria, pero mantiene las principales características que intervienen en la dinámica. El modelo ha demostrado ser útil para explicar el comportamiento fundamental de la catenaria, ayudando a comprender el fenómeno de interferencia entre dos pantógrafos. Este modelo analítico es adecuado para HIL debido a su bajo coste computacional. En el presente trabajo se propone un algoritmo iterativo para utilizar el modelo analítico en HIL. El hecho de que el modelo sea periódico permite la aplicación de una estrategia específica para compensar el retraso del lazo de control. Esta estrategia tiene un excelente rendimiento y precisión, validados al comparar ensayos HIL con simulaciones. La validación se realiza con un peso en el lugar del pantógrafo para eliminar las potenciales diferencias en el modelo. Si bien la precisión alcanzada es buena, el modelo analítico de catenaria carece de fidelidad, lo que ha motivado el desarrollo del siguiente modelo. El segundo modelo de catenaria para ensayos HIL es el Modelo Periódico de Elementos Finitos (MPEF), discretizado con el MEF para evitar adicionales simplificaciones topológicas y estructurales. En la formulación se incluye la condición de periodicidad y la dinámica se resuelve mediante análisis en frecuencia. Además, las no linealidades de la catenaria se consideran en la formulación. Un algoritmo iterativo, similar al utilizado para los ensayos HIL con catenaria analítica, es usado para realizar ensayos HIL con catenarias MPEF. La estrategia anterior de utilización de un peso se emplea para validar el sistema de ensayos, resultando tener una gran precisión. Los resultados son gratificantes debido a la sofisticación del modelo de catenaria, la precisión de los ensayos y la cancelación del retraso. Los ensayos realizados simulan la respuesta de catenarias realistas con la hipótesis simplificativa de periodicidad. Son adecuados para la dinámica de catenarias de vanos iguales en la zona central de cada cantón, sin embargo es necesario seguir realizando esfuerzos para eliminar la condición de periodicidad sin comprometer la precisión de los resultados.[CA] Existeix una extensa xarxa de línies ferroviàries electrificades a tot el món. La majoria d'elles utilitzen Línies Aèries de Contacte o catenàries per a subministrar electricitat als trens. Les catenàries són estructures de cables situades sobre les vies ferroviàries, dissenyades per a ser contactades pels pantògrafs que es troben sobre la part superior de la locomotora. El correcte funcionament del sistema requereix un alt nivell d'exigència, especialment a alta velocitat, quan la continuïtat del contacte es veu compromesa. L'eina majoritària per el sistema pantògraf-catenària és l'ús de simulacions numèriques. En particular, el Mètode dels Elements Finits (MEF) és la tècnica més usada per a modelar i simular la interacció dinàmica del pantògraf amb la catenària. Aquest mètode permet modelar catenàries. Després de l'etapa de simulació, el pantògraf i les catenàries han de ser testats en assajos experimentals en via. No obstant això, existeix una alternativa que pot reemplaçar eixos assajos amb una reducció significativa de costos. Aquesta alternativa, anomenada Hardware in the Loop (HIL), permet testar pantògrafs en el laboratori amb un banc d'assajos que emula la interacció amb una catenària virtual. Diferents grups d'investigació han implementat HIL; no obstant això, en tots els intents s'han adoptat solucions de compromís, la qual cosa demostra el repte que suposa l'aplicació de HIL. Aquesta Tesi pretén avançar en el camp dels assajos HIL, impulsant les capacitats de la tècnica i solucionant algunes de les limitacions trobades en la literatura. Aquesta Tesi proposa dos tipus diferents de models de catenària per al seu ús en assajos HIL. El primer és un model analític basat en un cable tens amb perfil geomètric periòdic que proporciona la solució estacionària del sistema. Aquest model redueix la complexitat de la catenària, però manté les principals característiques que intervenen en la dinàmica. El model ha demostrat ser útil per a explicar la dinàmica fonamental de la catenària, ajudant a comprendre el fenomen d'interferència entre dos pantògrafs. Aquest model analític és adequat per a realitzar assajos HIL a causa del seu baix cost computacional. Aquest treball proposa un algoritme iteratiu per a utilitzar el model analític en assajos HIL de pantògrafs. El fet que el model siga periòdic permet l'aplicació d'una estratègia específica per a compensar el retard del llaç de control. Aquesta estratègia té un excel·lent rendiment i precisió, validats en comparar assajos HIL amb simulacions numèriques. La validació es realitza amb una massa en el lloc del pantògraf per a eliminar les potencials diferències en el model. Si bé la precisió aconseguida és bona, el model analític de catenària manca de fidelitat, la qual cosa ha motivat el desenvolupament d'un model periòdic més avançat. El segon model de catenària per a assajos HIL és el Model Periòdic d'Elements Finits MPEF, discretitzat amb el MEF per a evitar simplificacions topològiques i estructurals addicionals. El model inclou la condició de periodicitat i la dinàmica es resol mitjançant anàlisi en freqüència. A més, les no linealitats de la catenària es consideren en la formulació. Un algoritme iteratiu, similar a l'utilitzat per als assajos HIL amb catenària analítica, és usat per a realitzar assajos HIL amb catenàries MPEF. L'estratègia anterior d'utilització d'una massa s'empra per a validar el sistema d'assajos, resultant tindre una gran precisió. Els resultats són gratificants a causa de la sofisticació del model de catenària, la precisió dels assajos i la cancel·lació del retard. Els assajos realitzats simulen la resposta de catenàries realistes amb la hipòtesi simplificativa de periodicitat. Són adequats per a la dinàmica de catenàries de vans iguals en la zona central dels seccionaments, no obstant això és necessari continuar fent esforços per a eliminar la condició de periodicitat sense comprometre la precisió dels res[EN] There is an extensive network of electrified railway lines over the world. Most of them use overhead contact lines or catenaries to provide the trains with electrical power. Catenaries consist of electrified wires placed over the rail track, designed to contact the pantograph placed on the roof of the train. The proper operation of the system is very demanding, especially at high speed, when the continuity of the contact is compromised. The most predominant tool for studying and designing the pantograph-catenary system is the use of numerical simulations. Notably, the Finite Element Method (FEM) is the most popular technique for modelling and simulating the dynamic interaction of the pantograph and the catenary. This method allows modelling catenaries with outstanding fidelity and without any loss of generality. After the simulation stage, the pantograph and the catenaries have to be assessed by in-line experimental tests. However, there is an alternative that can replace those tests with a significant reduction in costs. The alternative method, called Hardware In the Loop (HIL), allows testing pantographs in the laboratory with a test rig that emulates the interaction with a virtual catenary. Different research groups have implemented HIL; however, in every attempt, a compromise solution has been adopted, demonstrating the challenging nature of HIL. This Thesis aims to advance in the field of HIL tests, pushing forward the capabilities of the technique and solving some of the limitations found in the literature. This Thesis proposes two different kinds of catenary models for their use in HIL tests. The first is an analytical model based on a string of periodic geometric profile that accounts for the steady state. It reduces the complexity of the catenary but keeps the main features involved in the dynamic. The model has proven useful in explaining the fundamental dynamics of the catenary, helping understand the interference between two pantographs. This analytical model is suitable for HIL because of its low computational cost. An iterative algorithm is proposed to use the analytical model in HIL. The fact that the model is periodic permits a specific strategy to compensate the control loop delay. This strategy has excellent performance and accuracy, validated by comparing HIL tests with numerical simulations and getting an agreement. This agreement will not be possible if the pantograph model of the simulations is inaccurate. Therefore, the validation is carried out with a weight or mass model in place of the pantograph to eliminate potential differences. Even though the precision achieved is good, the analytical catenary model lacks fidelity, which has motivated the development of a more advanced periodic model. The second catenary model for HIL tests is the Periodic Finite Element Model (PFEM), discretised with FEM to avoid further topological and structural simplifications. The model includes the periodicity condition, and the dynamics are solved by frequency analysis. Furthermore, the catenary non-linearities are considered in the formulation. An iterative algorithm, similar to the one used for the HIL tests with the analytical catenary, is used to realise HIL tests with PFEM catenaries. The previous strategy with a mass model is used to validate the test, confirming great precision. The results are gratifying due to the sophistication of the model, the accuracy of the tests and the cancellation of the delay. The tests simulate the response of realistic catenaries with the simplifying periodicity hypothesis. They are adequate for the dynamic of equal-span catenary at the central zone of every section, but future efforts have to be made to get rid of the periodicity condition while keeping the accuracy of the results.The authors would like to acknowledge the financial support received from the State Research Agency of the Spanish Science and Innovation Ministry (PID2020- 113458RB-I00) and from the Valencian Regional Government (PROMETEO/2021/046) (PROMETEO/2016/007) and the Spanish Ministry of Economy, Industry and Competitiveness (TRA2017-84736-R), also the funds received jointly from the Regional Government of Valencia and the Euro- pean Social Fund, under Grant APOSTD/2019/205Gil Romero, J. (2022). Pantograph-Catenary Dynamic Models and their Implementation in Hardware-in-the-Loop Tests [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/191501Compendi

The design of a lathe attachment for grinding non-circular cross- section shafts suitable for torque transmission

PhD ThesisThe principle concern of this work is the design of a lathe attachment for grinding non-circular 'polygonal' shaped workpieces suitable for use as torque transmitting machine elements. In the course of the work substantial attention is also given to the general theory and development of computer aided error analysis procedures for planar linkage mechanisms. A further smaller part of the work investigates the torsion of polygonal shafts. The non-circular shapes considered here may be loosely defined as polygonal profiles. Their application is in torque transmitting couplings for which they represent an alternative to keyed and splined couplings, although, in comparison to keys and splines, their application has been limited, mainly due to the specialised nature of their manufacture. The main objective of this work is to investigate suitable profiles and the means for their production using an attachment which can be mounted on a conventional machine tool, such as a lathe or grinding machine. The work progresses from initial consideration of shapes produced by various geometric generating methods and conception of an 'ideal' profile generating linkage mechanism through to detailed design of a precision, polygonal profile grinding, lathe attachment, and final assessment of its feasibility based on a profile precision criterion. In order to assess the precision of the attachment, computer-aided procedures are developed, after consideration of existing error analysis methods and their limitations for use in this case. These consider the various effects of tolerances, clearances and deflections upon mechanism output. As a coincidental investigation, the mechanical behaviour and strength of polygonal shaft-hub connections is reported. In particular, the torsion of a polygonal bar is theoretically analysed, using a stress function method, to determine maximum shear stresses