1,476 research outputs found

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

    Get PDF
    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

    A robotic platform for precision agriculture and applications

    Get PDF
    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

    A Changing Landscape:On Safety & Open Source in Automated and Connected Driving

    Get PDF

    Characterising natural ventilation through open windows in the presence of wind: a theoretical and experimental investigation into the interaction between window geometry and environmental forces, and its application to envelope flow models of natural ventilation

    Get PDF
    Natural ventilation systems utilise pressure differentials that arise from wind and buoyancy forces to drive air through buildings. Natural ventilation is typically described using envelope flow models. These are used to size window openings at the design stage, and to predict the annual dynamic thermal performance of buildings. However, envelope flow models rely on highly idealised descriptions of flow through ventilation openings, which do not model realistic window geometries encountered in practice, and assume that ambient air is static. When envelope flow models are applied to building design, inadequate accounting for phenomena relating to wind and opening geometry can lead to under-sized ventilation openings and under-performing buildings. This thesis develops empirical models that characterise the effect of wind and window geometry on ventilation rates through square orifices and square, hinged openings. To ensure that these models can be applied in the design case to an arbitrary building geometry, these models are characterised using conditions local to the opening. Here the effect of wind is accounted for by a simulated cross-flow parallel to the building façade, and dimensional scaling arguments are applied to develop empirical models of wind driven phenomena based on similarity theory. Three experimental conditions are modelled: still-air tests that measure the ventilation capacity of an opening in idealised conditions; local pressure tests that measure the wind-induced static pressure differential over an opening when no flow occurs through that opening; and dynamic flow tests that measure the ventilation capacity of an opening between these limits. To validate the use of these local-scale models in building design, this work is then extended to predict the ventilation in a simple two-zone building. This requires the measurement of the speed and direction of the cross-flow on the building façades, and to that end a novel probe is developed that enables simultaneous measurements of these parameters. Wind-tunnel experiments are then used to measure the ventilation rate achieved in the model building, and the results are compared against the predictions of the local-scale window-characterisation models developed in this thesis. The results show an improvement over current models, which tend to overestimate ventilation rates. This thesis shows that free area models, which are widely used to predict the ventilation capacity of windows, tend to systematically overestimate ventilation rate through simple hinged openings in still air. The Empirical Effective Area Model described in this thesis can be used to predict idealised discharge coefficients with a coefficient of determination of 0.98, compared to 0.57-0.74 for free area models. A wind-driven cross-flow is shown to interact with window geometry to alter the local pressure field over the surface of an opening. This thesis develops experimental techniques to characterise this change in pressure using a local pressure coefficient. This is used to specify a local dimensionless pressure which is shown to describe the transition between inflow and outflow through an opening. Empirical equations are developed that characterise the local pressure coefficient for square hinged windows as a function of flow approach angle and opening angle, with a coefficient of determination of 0.98. The generation of non-zero local pressure coefficients is shown to result in orifice discharge coefficients that tend to ±∞ as the dimensionless room pressure tends to zero. Dimensional analysis is used to suggest the total dimensionless volume flow rate as an alternative metric to characterise the ventilation capacity of an opening. This is shown to tend to the idealised discharge coefficient in still-air conditions, and to tend to zero as the local dimensionless pressure tends to zero. The total dimensionless volume flow rate is shown to be finite across the whole range of potential local dimensionless pressure values, and holds positive values for outflow and negative values for inflow. Empirical models are developed to predict the total dimensionless volume flow rate through a square orifice and a square, hinged window as a function of local dimensionless pressure, flow approach angle and opening angle. Coefficients of determination are between 0.975 and 0.984 for the hinged window and between 0.993 and 0.995 for the square orifice, depending on the opening direction and the direction of flow through the opening. The speed and direction of the cross-flow on the façade of a model cube in a simulated atmospheric boundary layer were measured using the novel cross-flow probe developed in this thesis. Here, mean cross-flow speeds measured with the novel probe agree well with hot-wire measurements. The cross-flow measurements reveal a tetra-modal distribution in façade cross-flow direction, which interacts with a uni-modal variation in cross-flow speed to generate bi-modal distributions in the x and y velocity components at all measured wind angles. This data is used to generate profiles of mean cross-flow speed and mean façade cross-flow direction with wind angle, which are used as inputs to the empirical equations developed to describe the total dimensionless volume flow rate through isolated window openings. The empirical models used to describe the total dimensionless volume flow rate through isolated windows is used to predict measured ventilation rates in a model building with an internal partition, with a coefficient of determination between 0.94 and 0.99, depending on the ventilation configuration. This compares with coefficients of determination between -0.4 and 0.08 found when applying a conventional orifice flow model. Conventional orifice flow models are predicted to provide good estimates of net volume flow rates through buildings with simple orifice-type openings when the internal resistance is lower than that of either of the external openings. As the internal resistance increases, the orifice flow equation is predicted to increasingly overestimate net volume flow rates. This work contributes to knowledge by: quantifying the systematic errors arising from the use of free area models common to natural ventilation design; developing an empirical model that describes an idealised discharge coefficient of a family of hinged openings as a function of geometric parameters; identifying novel dimensionless parameters that characterise the change in static pressure across an opening that results from the interaction between wind and window geometry; developing experimental techniques that provide a simple and unambiguous measurement of the local pressure coefficient; experimentally and empirically describing the aerodynamic performance of a simple, square, hinged window in wind-driven conditions; developing a cross-flow probe that can measure the instantaneous speed and direction of wind-driven flow over the surface of a building; quantifying the systematic errors associated with the use of a range of calculation methodologies used to estimate the ventilation rate in a simple model building; and providing practical design guidance to minimise the effect of calculation errors that arise from the use of conventional envelope flow models in wind-driven conditions, when adequate data to describe the phenomena is unavailable

    Development of the C-GEN generator technology for vertical axis wind turbines

    Get PDF
    In this thesis, 5 MW, 7.5MWand 10MWat 6 rpm C-GEN generator models were designed and optimized respectively for a vertical axis wind turbine. Although VAWTs have lower rotational speed than HAWTs, the offered C-GEN VAWT generators have significant higher power density compared to conventional PM and superconducting HAWT generators of equivalent power. The inner radius of the 5 MW C-GEN generator is 5.35 m and mass is 41.2 tonnes. The inner radius of the 7.5 MW C-GEN generator is 5.35 m and active mass is 44.1 tonnes. The inner radius of the 10 MW C-GEN generator is 7.50 m and active mass is 41.6 tonnes. Annual generation results show that offshore VAWT can generate as much energy as HAWT of the same power. In addition, by the end of 2022, the most powerful single offshore HAWT is 14 MW and due to the tower head mass of HAWTs, it is limited to increase the power further. Multi-power platform VAWTs can take the power of a single turbine further. The C-GEN model with wavy and comb steel structure has higher power density than the C-GEN model with straight steel structure. In addition, in the multi-stage C-GEN models, the comb steel structure will allow the passage of air between the stages, and since the wavy steel structure has more surface area than straight steel, it can help to increase the thermal performance of the machine. Since machine mass is an important factor in aviation, automotive propulsion systems and renewable energy converters, these structures can provide advantage. The machines are analysed and optimised electromagnetically using 2-D FEA simulations. A software algorithm has been developed for the simulations. This algorithm allows any electrical machine to be modelled and optimized easily and quickly. In addition, this algorithm can be applied to 3-D models and other branches of engineering such as mechanical, civil, naval, aircraft and etc. for use CAD and FEA models

    New Advances in Oil, Gas and Geothermal Reservoirs

    Get PDF
    The demand for global fossil energy continues to be strong, meaning that the exploitation of oil and gas resources is still very important. In addition, due to the continuous reduction in conventional oil and gas recoverable resources, the development of unconventional oil and gas resources and geothermal energy has gradually become an important replacement. Therefore, it is urgent to improve the existing mechanism analysis, research methods and engineering technology to improve the production and development efficiency of oil, gas, and geothermal resources. This reprint presents 11 recent works on the application of new theories and technologies in oil, gas, and geothermal reservoirs. The content covers well-drilling, cementing, hydraulic fracturing, improved oil recovery, conformance control, and geothermal energy development. The new progress presented in this reprint will help scientists and researchers to better understand and master the latest theories and techniques for oil, gas, and geothermal reservoirs, which has important practical significance for the economical and effective development of oil, gas, and geothermal resources

    Updating structural wind turbine blade models via invertible neural networks

    Get PDF
    Wind turbine rotor blades are huge and complex composite structures that are exposed to exceptionally high loads, both extreme and fatigue loads. These can result in damages causing severe downtimes or repair costs. It is thus of utmost importance that the blades are carefully designed, including uncertainty analyses in order to produce safe, reliable, and cost-efficient wind turbines. An accurate reliability assessment should already start during the design and manufacturing phases. Recent developments in digitalization give rise to the concept of a digital twin, which replicates a product and its properties into a digital environment. Model updating is a technique, which helps to adapt the digital twin according to the measured characteristics of the real structure. Current model updating techniques are most often based on heuristic optimization algorithms, which are computationally expensive, can only deal with a relatively small parameter space, or do not estimate the uncertainty of the computed results. This thesis’ objective is to present a computationally efficient model updating method that recovers parameter deviation. This method is able to consider uncertainties and a high fidelity degree of the rotor blade model. A validated, fully parameterized model generator is used to perform a physics-informed training of a conditional invertible neural network. This network finally represents a surrogate of the inverse physical model, which then can be used to recover model parameters based on the structural responses of the blade. All presented generic model updating applications show excellent results, predicting the a posteriori distribution of the significant model parameters accurately.Bundesministerium für Wirtschaft und Klimaschutz/Energietechnologien (BMWi)/0324032C, 0324335B/E

    Design and Development of Biofeedback Stick Technology (BfT) to Improve the Quality of Life of Walking Stick Users

    Get PDF
    Biomedical engineering has seen a rapid growth in recent times, where the aim to facilitate and equip humans with the latest technology has become widespread globally. From high-tech equipment ranging from CT scanners, MRI equipment, and laser treatments, to the design, creation, and implementation of artificial body parts, the field of biomedical engineering has significantly contributed to mankind. Biomedical engineering has facilitated many of the latest developments surrounding human mobility, with advancement in mobility aids improving human movement for people with compromised mobility either caused by an injury or health condition. A review of the literature indicated that mobility aids, especially walking sticks, and appropriate training for their use, are generally prescribed by allied health professionals (AHP) to walking stick users for rehabilitation and activities of daily living (ADL). However, feedback from AHP is limited to the clinical environment, leaving walking stick users vulnerable to falls and injuries due to incorrect usage. Hence, to mitigate the risk of falls and injuries, and to facilitate a routine appraisal of individual patient’s usage, a simple, portable, robust, and reliable tool was developed which provides the walking stick users with real-time feedback upon incorrect usage during their activities of daily living (ADL). This thesis aimed to design and develop a smart walking stick technology: Biofeedback stick technology (BfT). The design incorporates the approach of patient and public involvement (PPI) in the development of BfT to ensure that BfT was developed as per the requirements of walking stick users and AHP recommendations. The newly developed system was tested quantitatively for; validity, reliability, and reproducibility against gold standard equipment such as the 3D motion capture system, force plates, optical measurement system for orientation, weight bearing, and step count. The system was also tested qualitatively for its usability by conducting semi-informal interviews with AHPs and walking stick users. The results of these studies showed that the newly developed system has good accuracy, reported above 95% with a maximum inaccuracy of 1°. The data reported indicates good reproducibility. The angles, weight, and steps recorded by the system during experiments are within the values published in the literature. From these studies, it was concluded that, BfT has the potential to improve the lives of walking stick users and that, with few additional improvements, appropriate approval from relevant regulatory bodies, and robust clinical testing, the technology has a huge potential to carve its way to a commercial market

    The American Multi-modal Energy System: Model Development with Structural and Behavioral Analysis using Hetero-functional Graph Theory

    Get PDF
    In the 21st century, infrastructure is playing an ever greater role in our daily lives. Presidential Policy Directive 21 emphasizes that infrastructure is critical to public confidence, the nation\u27s safety, and its well-being. With global climate change demanding a host of changes across at least four critical energy infrastructures: the electric grid, the natural gas system, the oil system, and the coal system, it is imperative to study models of these infrastructures to guide future policies and infrastructure developments. Traditionally these energy systems have been studied independently, usually in their own fields of study. Therefore, infrastructure datasets often lack the structural and dynamic elements to describe the interdependencies with other infrastructures. This thesis refers to the integration of the aforementioned energy infrastructures into a singular system-of-systems within the context of the United States of America as the American Multi-modal Energy System (AMES). This work develops an open-source structural and behavioral model of the AMES using Hetero-functional Graph Theory (HFGT), a data-driven approach, and model-based systems engineering practices in the following steps. First, the HFGT toolbox code is made available on GitHub and advanced to produce HFGs of systems on the scale of the AMES using the languages Python and Julia. Second, the analytical insights that HFGs can provide relative to formal graphs are investigated through structural analysis of the American Electric Power System which demonstrates how HFGs are better equipped to describe changes in system behavior. Third, a reference architecture of the AMES is developed, providing a standardized foundation to develop future models of the AMES. Fourth, the AMES reference architecture is instantiated into a structural model from which structural properties are investigated. Finally, a physically informed Weighted Least Squares Error Hetero-functional Graph State Estimation analysis of the AMES\u27 socio-economic behavior is implemented to investigate the behavior of the AMES with asset level granularity. These steps provide a reproducible and reusable structural and behavioral model of the AMES for guiding future policies and infrastructural developments to critical energy infrastructures
    • …
    corecore