3,730 research outputs found

    Teleoperation Methods for High-Risk, High-Latency Environments

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    In-Space Servicing, Assembly, and Manufacturing (ISAM) can enable larger-scale and longer-lived infrastructure projects in space, with interest ranging from commercial entities to the US government. Servicing, in particular, has the potential to vastly increase the usable lifetimes of satellites. However, the vast majority of spacecraft on low Earth orbit today were not designed to be serviced on-orbit. As such, several of the manipulations during servicing cannot easily be automated and instead require ground-based teleoperation. Ground-based teleoperation of on-orbit robots brings its own challenges of high latency communications, with telemetry delays of several seconds, and difficulties in visualizing the remote environment due to limited camera views. We explore teleoperation methods to alleviate these difficulties, increase task success, and reduce operator load. First, we investigate a model-based teleoperation interface intended to provide the benefits of direct teleoperation even in the presence of time delay. We evaluate the model-based teleoperation method using professional robot operators, then use feedback from that study to inform the design of a visual planning tool for this task, Interactive Planning and Supervised Execution (IPSE). We describe and evaluate the IPSE system and two interfaces, one 2D using a traditional mouse and keyboard and one 3D using an Intuitive Surgical da Vinci master console. We then describe and evaluate an alternative 3D interface using a Meta Quest head-mounted display. Finally, we describe an extension of IPSE to allow human-in-the-loop planning for a redundant robot. Overall, we find that IPSE improves task success rate and decreases operator workload compared to a conventional teleoperation interface

    Writing in Water

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    Writing is an ancient communication technique dating back at least 30,000 years. While even sophisticated contemporary writing techniques hinge on solid surfaces for engraving or the deposition of ink, writing within a liquid medium requires a fundamentally different approach. We here demonstrate writing of lines, letters and complex patterns in water by assembling lines of colloidal particles. Exploiting gravity, we roll an ion-exchange bead (pen) across a layer of sedimented colloidal particles (ink). The pen evokes a hydrodynamic flow collecting ink-particles into a durable, high-contrast line along its trajectory. Deliberate substrate-tilting sequences facilitate pen-steering and thus to draw and write. We complement our experiments with a minimal model that quantitatively predicts the observed parameter dependence for writing in fluids and highlights the generic character of writing by line-assembly. Overall, our approach opens a versatile route for writing, drawing and patterning fluids, even at the micro-scale.Comment: Article 23 p, 5 figs, 53 refs, Supl. Info with 13 fig

    Direct measurement of coating thermal noise in the AEI 10m prototype

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    A thermal noise interferometer for the characterization of thermal noise in high reflectivity mirrors has been commissioned and first direct measurements of coating thermal noise have been performed. This serves as an important step in the improvement of current and future gravitational wave detectors

    Peering into the Dark: Investigating dark matter and neutrinos with cosmology and astrophysics

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    The LCDM model of modern cosmology provides a highly accurate description of our universe. However, it relies on two mysterious components, dark matter and dark energy. The cold dark matter paradigm does not provide a satisfying description of its particle nature, nor any link to the Standard Model of particle physics. I investigate the consequences for cosmological structure formation in models with a coupling between dark matter and Standard Model neutrinos, as well as probes of primordial black holes as dark matter. I examine the impact that such an interaction would have through both linear perturbation theory and nonlinear N-body simulations. I present limits on the possible interaction strength from cosmic microwave background, large scale structure, and galaxy population data, as well as forecasts on the future sensitivity. I provide an analysis of what is necessary to distinguish the cosmological impact of interacting dark matter from similar effects. Intensity mapping of the 21 cm line of neutral hydrogen at high redshift using next generation observatories, such as the SKA, would provide the strongest constraints yet on such interactions, and may be able to distinguish between different scenarios causing suppressed small scale structure. I also present a novel type of probe of structure formation, using the cosmological gravitational wave signal of high redshift compact binary mergers to provide information about structure formation, and thus the behaviour of dark matter. Such observations would also provide competitive constraints. Finally, I investigate primordial black holes as an alternative dark matter candidate, presenting an analysis and framework for the evolution of extended mass populations over cosmological time and computing the present day gamma ray signal, as well as the allowed local evaporation rate. This is used to set constraints on the allowed population of low mass primordial black holes, and the likelihood of witnessing an evaporation

    Estratégias passivas de baixo custo para habitação pobre no Brasil: uma investigação em Research by Design

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    Resumo A habitação pobre é uma realidade em expansão num planeta com mais de 50% da sua população pobre. Estas habitações contemporâneas já não são feitas com base no conhecimento vernacular que as fazia adaptadas ao contexto, sendo ineficazes no controlo das condições de conforto interiores. Se os efeitos do sobreaquecimento interno das habitações são prejudiciais à saúde dos seus residentes, no contexto das alterações climáticas, o efeito das ondas de calor, que se prevêem mais intensas e mais frequentes, colocam esta população vulnerável, em risco. Esta pesquisa procura e desenha estratégias passivas de baixo custo, num sistema do-it-yourself, para serem implementadas nas habitações pelos seus residentes, para mitigar os efeitos do sobreaquecimento interno, no clima quente semiárido do Brasil. A Metodologia utilizada é a de Research by Design (RbD) e é caraterizada por duas fases distintas e complementares da investigação. A primeira fase foi efetuada in-situ, permitindo uma análise interpretativa através de trabalho de campo para contextualizar o estudo, orientando, assim, a definição das estratégias. Nesta fase foi selecionada uma primeira estratégia de melhoria da ventilação natural, através do dispositivo da chaminé solar. Esta foi estudada e redesenhada, sendo sucessivamente construída, instalada e testada numa habitação pobre no Brasil, habitada. A análise dos resultados obtidos sugeriu o desenvolvimento de uma nova campanha de experiências, alargando o espectro das estratégias a implementar, ensaiando-as em ambiente controlado. Na segunda fase, que decorreu em Lisboa, foram determinadas as estratégias complementares, construídas e ensaiadas, individualmente e de modo combinado, em ambiente controlado em célula teste, construída a semelhança das habitações pobres no Brasil. O painel de isolamento térmico, construído com embalagens recicladas de Tetra Pak (ReTIBS), apresentou o melhor resultado de arrefecimento da célula teste, ao menor custo. Os dados mesurados durante a experiência com o ReTIBS, foram utilizados para calibrar um modelo de simulação termodinâmica, que foi sucessivamente aplicado às cidades mais quentes do Brasil e da América Latina, em clima semiárido e em outros climas tropicais, no presente e num cenário futuro de alterações climáticas para 2050. A investigação termina com a compilação de um manual de construção, aplicação e uso do ReTIBS. Por outro lado, o processo e o resultado, desta investigação demonstraram a eficácia da metodologia RbD, que permitiu a utilização alternada de aproximações qualitativas e quantitativas, para a formulação da pergunta e para a legitimação da resposta; Abstract: Poor housing is an expanding reality on a planet with more than 50% of its population poor. These contemporary dwellings are no longer made based on the vernacular knowledge that made them adapted to their climate context, being ineffective in controlling the interior comfort conditions. If the effects of internal overheating of homes are harmful to the health of its residents, in the context of climate change, the impact of heat waves, expected to be more intense and more frequent, put this vulnerable population at risk. This research seeks to design low-cost passive strategies in a do-it-yourself system, to be implemented in houses by its residents to mitigate the effects of internal overheating in the hot semi-arid climate of Brazil. The methodology used is Research by Design (RbD), characterized by two distinct and complementary phases of research. The first phase was carried out in situ, allowing an interpretative analysis through fieldwork to contextualize the study, thus guiding the strategy's definition. At this stage, the first selected strategy was a solar chimney device to improve natural ventilation. This device was studied, redesigned, successfully built, installed, and tested in a poor inhabited house in Brazil. The analysis of the results suggested the development of a new experimental campaign, expanding the spectrum of strategies to be implemented to be tested in a controlled environment. In the second phase, which took place in Lisbon, complementary strategies were determined, built, and tested, individually and combined, in a controlled environment in a test cell, built similarly to a poor house in Brazil. The thermal insulation panel, built with recycled Tetra Pak packaging (ReTIBS), presented the best cooling result in the test cell at the lowest cost. The data, measured during the experience with ReTIBS, were used to calibrate a thermodynamic simulation model, which was applied to the climate of the hottest cities in Brazil and Latin America, in semi-arid climates and other tropical climates, in the present and future scenarios of climate change for 2050. The investigation ends with the edition of a manual for the construction, application, and use of ReTIBS. On the other hand, the process and the result of this investigation demonstrated the effectiveness of the RbD methodology, which allowed the alternate use of qualitative and quantitative approaches, both for the formulation of the question and the legitimation of the answer

    A robotic platform for precision agriculture and applications

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    Agricultural techniques have been improved over the centuries to match with the growing demand of an increase in global population. Farming applications are facing new challenges to satisfy global needs and the recent technology advancements in terms of robotic platforms can be exploited. As the orchard management is one of the most challenging applications because of its tree structure and the required interaction with the environment, it was targeted also by the University of Bologna research group to provide a customized solution addressing new concept for agricultural vehicles. The result of this research has blossomed into a new lightweight tracked vehicle capable of performing autonomous navigation both in the open-filed scenario and while travelling inside orchards for what has been called in-row navigation. The mechanical design concept, together with customized software implementation has been detailed to highlight the strengths of the platform and some further improvements envisioned to improve the overall performances. Static stability testing has proved that the vehicle can withstand steep slopes scenarios. Some improvements have also been investigated to refine the estimation of the slippage that occurs during turning maneuvers and that is typical of skid-steering tracked vehicles. The software architecture has been implemented using the Robot Operating System (ROS) framework, so to exploit community available packages related to common and basic functions, such as sensor interfaces, while allowing dedicated custom implementation of the navigation algorithm developed. Real-world testing inside the university’s experimental orchards have proven the robustness and stability of the solution with more than 800 hours of fieldwork. The vehicle has also enabled a wide range of autonomous tasks such as spraying, mowing, and on-the-field data collection capabilities. The latter can be exploited to automatically estimate relevant orchard properties such as fruit counting and sizing, canopy properties estimation, and autonomous fruit harvesting with post-harvesting estimations.Le tecniche agricole sono state migliorate nel corso dei secoli per soddisfare la crescente domanda di aumento della popolazione mondiale. I recenti progressi tecnologici in termini di piattaforme robotiche possono essere sfruttati in questo contesto. Poiché la gestione del frutteto è una delle applicazioni più impegnative, a causa della sua struttura arborea e della necessaria interazione con l'ambiente, è stata oggetto di ricerca per fornire una soluzione personalizzata che sviluppi un nuovo concetto di veicolo agricolo. Il risultato si è concretizzato in un veicolo cingolato leggero, capace di effettuare una navigazione autonoma sia nello scenario di pieno campo che all'interno dei frutteti (navigazione interfilare). La progettazione meccanica, insieme all'implementazione del software, sono stati dettagliati per evidenziarne i punti di forza, accanto ad alcuni ulteriori miglioramenti previsti per incrementarne le prestazioni complessive. I test di stabilità statica hanno dimostrato che il veicolo può resistere a ripidi pendii. Sono stati inoltre studiati miglioramenti per affinare la stima dello slittamento che si verifica durante le manovre di svolta, tipico dei veicoli cingolati. L'architettura software è stata implementata utilizzando il framework Robot Operating System (ROS), in modo da sfruttare i pacchetti disponibili relativi a componenti base, come le interfacce dei sensori, e consentendo al contempo un'implementazione personalizzata degli algoritmi di navigazione sviluppati. I test in condizioni reali all'interno dei frutteti sperimentali dell'università hanno dimostrato la robustezza e la stabilità della soluzione con oltre 800 ore di lavoro sul campo. Il veicolo ha permesso di attivare e svolgere un'ampia gamma di attività agricole in maniera autonoma, come l'irrorazione, la falciatura e la raccolta di dati sul campo. Questi ultimi possono essere sfruttati per stimare automaticamente le proprietà più rilevanti del frutteto, come il conteggio e la calibratura dei frutti, la stima delle proprietà della chioma e la raccolta autonoma dei frutti con stime post-raccolta

    Microwave Induced Optical Nonlinearities in Cuprous Oxide

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    This thesis presents an experimental study of the transmission spectrum of cuprous oxide in the presence of a microwave field. Using one photon spectroscopy an excitonic population is created which can then be modified by the application of a microwave field. This was achieved using a combination of microwave antennae and high-resolution spectroscopy. The main results presented in this thesis are: (1) Using photoluminescence and transmission spectroscopy the quality of natural and synthetic samples was measured, finding natural samples to be far superior. This was attributed to the presence of copper vacancies in the synthetic material. These vacancies were removed through thermal annealing, but this did not improve the quality of synthetic samples. (2) Determination of temperature as the limiting factor to observe higher nP states. This was carried out through spectroscopy of cuprous oxide over a range of temperatures. (3) Observation of large optical nonlinearities in the presence of a microwave field. These manifest as changes in absorption which is stronger for higher nn states, where for sufficiently strong fields it is no longer possible to resolve them. An additional impact of the microwave field is an increase in the absorption between states. These observations were modelled by treating excitons as spinless hydrogen enabling an extraction of the nonlinear susceptibility using an atomic physics approach. The change in absorption is well described by this model. Alongside this, a large cross-Kerr nonlinearity is estimated which is several orders of magnitude larger than that seen in conventional media. These results cement cuprous oxide as a viable platform for Rydberg physics wherein strong coupling to external fields can be detected. This also highlights the need to develop high-quality synthetic material to remove the reliance on naturally occurring samples

    Superhydrophilic and superoleophobic meshes for on-site oil-water separation

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    Oil spills are becoming a major cause of environmental damage on a worldwide scale. Effective ways to separate oil from water are needed to solve this issue. Meshes and membranes that are superhydrophilic/superoleophobic are promising materials for oil-water separation, but their actual utilisation still confronts several obstacles. In this work, we made oleophobic TiO₂ and SiO₂ nanoparticle-coated superhydrophilic stainless steel meshes. The coating was made by electrophoretically depositing positively charged nanoparticles of TiO₂ and SiO₂ on stainless steel meshes after treating of TiO₂ and SiO₂ with iodine in acetyl acetone solutions. To increase stability and oil-water separation performance, four different mesh counts (80, 120, 200, and 400) were created and put through sintering operations at various temperatures. X-ray diffraction (XRD), scanning electron microscopy (SEM), and contact angle (CA) measurements were used to explore the specific microscopic structural characteristics of these meshes. These meshes were evaluated for their ability to separate oil from water using gas florescence and ultraviolet-visible (UV-vis) spectroscopic methods. Our research has shown that the mesh created with 1% concentration of SiO₂ (SiO₂/TiO₂ = 0.01), mesh spacing 400, and sintering temperature 800 °C had the optimal oil-water separation performance. It is important to note that for hexane and Terra-Nova oil, this mesh exhibits outstanding surface hydrophilicity/oleophobicity with static contact angles greater than 170°. In this experiment Terranova oil used in prepared emulsion for oil-water separation tests and the efficiency calculated was 91%. Also, these coated meshes can be reused for at least five cycles, according to durability testing, which also minimises the cost of treating oily wastewater

    Dexterity, workspace and performance analysis of the conceptual design of a novel three-legged, redundant, lightweight, compliant, serial-parallel robot

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    In this article, the mechanical design and analysis of a novel three-legged, agile robot with passively compliant 4-degrees-of-freedom legs, comprising a hybrid topology of serial, planar and spherical parallel structures, is presented. The design aims to combine the established principle of the Spring Loaded Inverted Pendulum model for energy efficient locomotion with the accuracy and strength of parallel mechanisms for manipulation tasks. The study involves several kinematics and Jacobian based analyses that specifically evaluate the application of a non-overconstrained spherical parallel manipulator as a robot hip joint, decoupling impact forces and actuation torques, suitable for the requirements of legged locomotion. The dexterity is investigated with respect to joint limits and workspace boundary contours, showing that the mechanism stays well conditioned and allows for a sufficient range of motion. Based on the functional redundancy of the constrained serial-parallel architecture it is furthermore revealed that the robot allows for the exploitation of optimal leg postures, resulting in the possible optimization of actuator load distribution and accuracy improvements. Consequently, the workspace of the robot torso as additional end-effector is investigated for the possible application of object manipulation tasks. Results reveal the existence of a sufficient volume applicable for spatial motion of the torso in the statically stable tripodal posture. In addition, a critical load estimation is derived, which yields a posture dependent performance index that evaluates the risks of overload situations for the individual actuators
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