132 research outputs found

    LIPIcs, Volume 274, ESA 2023, Complete Volume

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    LIPIcs, Volume 274, ESA 2023, Complete Volum

    Robust Approaches to Nonlinear Filtering with Applications to Navigation

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    Linear estimators, like the extended Kalman filter (EKF), find continual use (especially in the field of navigation) mostly for their familiarity and computational efficiency. Often, these estimations must be safeguarded from the realistic elements of physical systems, such as nonlinearities, non-Gaussian noises, and unmodeled effects. To this end, existing linear estimators are frequently outfitted with procedure-first robustness techniques—ad hoc mechanisms designed specifically to prevent filter failure—such as measurement editing, gain underweighting, filter resets, and more. As an alternative, this dissertation elects a model-first ethos, proposing nonlinear Gaussian mixture (GM) filters that are derived from first principles to be robust. These inherently robust algorithms are split into two approaches—1) non-Bayesian filters and 2) fault-cognizant filters—the end result being a collection of filters that challenge the status quo of current practical estimation; instead of reusing preexisting filter frameworks for the sake of ease, customized filters can be designed specifically for the system at hand. 1) Bayes’ rule, while the archetypal basis for measurement fusion, relies on a fundamental assumption; all specified models, such as prior distributions and measurement likelihoods, are presumed to exactly reflect reality. In practice, this is rarely the case, warranting an investigation into non-Bayesian alternatives to traditional measurement updates. Fortunately, generalized variational inference (GVI) provides an established foundation for such updates and is used in this work to prototype several robust non-Bayesian filters. As closed-form filters are usually preferred, an iterative confidence-based update is derived, which, through Monte Carlo analyses, is shown to be selectively conservative, such that a desired level of robustness can be user-appointed. 2) Whereas traditional filtering screens out undesirable, or faulty, measurements, fault-cognizant filtering attempts to directly model these erroneous measurements, yielding estimators inherently capable of processing returns that conflict with the conventional model of a sensor. As the nature of both valid and faulty measurements can differ significantly between systems, several different fault-cognizant updates (FCUs) are derived, each purposed for a specific application. Subsequent analyses illustrate the robustness of the FCU to faulty measurements, both known and unknown

    CNN-based local features for navigation near an asteroid

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    This article addresses the challenge of vision-based proximity navigation in asteroid exploration missions and on-orbit servicing. Traditional feature extraction methods struggle with the significant appearance variations of asteroids due to limited scattered light. To overcome this, we propose a lightweight feature extractor specifically tailored for asteroid proximity navigation, designed to be robust to illumination changes and affine transformations. We compare and evaluate state-of-the-art feature extraction networks and three lightweight network architectures in the asteroid context. Our proposed feature extractors and their evaluation leverages both synthetic images and real-world data from missions such as NEAR Shoemaker, Hayabusa, Rosetta, and OSIRIS-REx. Our contributions include a trained feature extractor, incremental improvements over existing methods, and a pipeline for training domain-specific feature extractors. Experimental results demonstrate the effectiveness of our approach in achieving accurate navigation and localization. This work aims to advance the field of asteroid navigation and provides insights for future research in this domain

    2021 GREAT Day Program

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    SUNY Geneseo’s Fifteenth Annual GREAT Day.https://knightscholar.geneseo.edu/program-2007/1015/thumbnail.jp

    Micro-Electro Discharge Machining: Principles, Recent Advancements and Applications

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    Micro electrical discharge machining (micro-EDM) is a thermo-electric and contactless process most suited for micro-manufacturing and high-precision machining, especially when difficult-to-cut materials, such as super alloys, composites, and electro conductive ceramics, are processed. Many industrial domains exploit this technology to fabricate highly demanding components, such as high-aspect-ratio micro holes for fuel injectors, high-precision molds, and biomedical parts.Moreover, the continuous trend towards miniaturization and high precision functional components boosted the development of control strategies and optimization methodologies specifically suited to address the challenges in micro- and nano-scale fabrication.This Special Issue showcases 12 research papers and a review article focusing on novel methodological developments on several aspects of micro electrical discharge machining: machinability studies of hard materials (TiNi shape memory alloys, Si3N4–TiN ceramic composite, ZrB2-based ceramics reinforced with SiC fibers and whiskers, tungsten-cemented carbide, Ti-6Al-4V alloy, duplex stainless steel, and cubic boron nitride), process optimization adopting different dielectrics or electrodes, characterization of mechanical performance of processed surface, process analysis, and optimization via discharge pulse-type discrimination, hybrid processes, fabrication of molds for inflatable soft microactuators, and implementation of low-cost desktop micro-EDM system

    Late breakdown behaviour of 72.5 kV vacuum interrupters during capacitive switching with a synthetic test method

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    The interruption of capacitive currents involves a demanding dielectric stress for high voltage vacuum interrupters. Dielectric breakdowns up to several hundreds of milliseconds after current interruption are possible, which may result in harmful voltage escalations. Additionally, high inrush currents prestress the vacuum interrupter especially during the energisation of capacitor banks. A synthetic test method is applied to study the late breakdown behaviour of vacuum interrupters of 72.5 kV rated voltage during capacitive switching. The first part of this work focuses on factorial experiments that are applied to determine the influence of different test circuit parameters on the breakdown behaviour in an efficient way. The results confirm the significant impact of inrush currents on the breakdown rate. However, a relevant effect of the other tested parameters, e.g. breaking current and arcing time, cannot be ascertained for the investigated range. In the second part of this work measured pre-breakdown phenomena are presented and discussed. While field emission currents are measured with a commonly applied sense resistor, the detection of charged microparticles is conducted by utilising a partial discharge measurement technique. With a contact stroke set to 38 mm field emission currents occur only rarely and only during the beginning of the recovery voltage with preceding late contact separation, when the full contact gap has not yet been established. For a reduced contact stroke of 20 mm high field emission currents can be present for long periods of time with magnitudes up to several tens of milliamperes. The phenomenon of self-limiting current pulses, often referred to as microdischarges, has also been observed repeatedly. Field emission currents and microdischarges are more likely to appear after the vacuum interrupter is stressed by an inrush current. However, the majority of breaking tests with late breakdowns include neither significant preceding field emission current nor microdischarges. Moreover, the mere presence of the highest field emission currents does not necessarily result in a disruptive discharge. This result supports the hypothesis that field emission at larger contact gaps has a negligible influence on the late breakdown behaviour. In the case of the microparticle detection measurement, a recurring current pulse pattern was detected that is likely to be linked to microparticles impacting with the contact surface. However, no correlation can be drawn between the frequency of occurrence of this pulse pattern and the occurrence of late breakdowns. Therefore, it is concluded that the breakdown process is not triggered by multiple microparticle collisions but rather by a singular event supplying sufficient energy for the release of electrons and gaseous matter for the fast development of dielectric breakdown inside the vacuum interrupter

    Project based-learning based on I-STEM (Islamic, Science, Technology, and Mathematics) to facilitate the development of geometric critical thinking skills of first middle students

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    In line with the 21st century, mathematics learning innovations continue to be developed to facilitate students' critical thinking skills by adjusting the context of their religious life. The purpose of this study is to provide ideas that teachers can do to implement Project Based Learning (PjBL) with a STEM (I-STEM) approach that is used to facilitate the development of students' critical thinking skills. The pattern of integration that is designed lies in the flat plane geometry material with the integration of the verses of the Koran and the internalization of Islamic values, with the hope of being able to create meaningful learning activities for students. This research is a qualitative research with library research. Data collection techniques are carried out through reviewing the literature, both from articles, books, and other documents that can be used to describe theories and information needed in research. The data analysis technique used is content analysis (content analysis). The results of this study are the I-STEM-based PjBL syntax includes 1) basic questions (integration with the verses of the Koran presented in the LKPD); 2) designing project plans (miniature Kaaba); 3) draw up a project completion schedule; 4) monitor project progress; 5) test project results (and compare with other problems); and 6) evaluate the learning experience. I-STEM-based PjBL was developed to facilitate the development of students' critical thinking skills through syntax and LKPD which were developed adapted to the context of Islamic life and the Koran at the junior high school level

    Project based-learning based on I-STEM (Islamic, Science, Technology, and Mathematics) to facilitate the development of geometric critical thinking skills of first middle students

    Get PDF
    In line with the 21st century, mathematics learning innovations continue to be developed to facilitate students' critical thinking skills by adjusting the context of their religious life. The purpose of this study is to provide ideas that teachers can do to implement Project Based Learning (PjBL) with a STEM (I-STEM) approach that is used to facilitate the development of students' critical thinking skills. The pattern of integration that is designed lies in the flat plane geometry material with the integration of the verses of the Koran and the internalization of Islamic values, with the hope of being able to create meaningful learning activities for students. This research is a qualitative research with library research. Data collection techniques are carried out through reviewing the literature, both from articles, books, and other documents that can be used to describe theories and information needed in research. The data analysis technique used is content analysis (content analysis). The results of this study are the I-STEM-based PjBL syntax includes 1) basic questions (integration with the verses of the Koran presented in the LKPD); 2) designing project plans (miniature Kaaba); 3) draw up a project completion schedule; 4) monitor project progress; 5) test project results (and compare with other problems); and 6) evaluate the learning experience. I-STEM-based PjBL was developed to facilitate the development of students' critical thinking skills through syntax and LKPD which were developed adapted to the context of Islamic life and the Koran at the junior high school level
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