94 research outputs found

    다중 센서 항법시스템을 위한 연합형 불변 확장칼만필터

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    학위논문(석사) -- 서울대학교대학원 : 공과대학 항공우주공학과, 2022.2. 박찬국.This thesis presents the federated invariant extended Kalman filter (IEKF) using multiple measurements. IEKF has superior estimation performance compared to EKF through the definition of state variables on matrix Lie group while using the framework of the EKF. The IEKF enables trajectory independent estimation when left- or right-invariant measurements are used with proper invariant error selection. As a result, the IEKF ensures the convergence and accuracy of estimation, even when the estimation error is large. Most IEKF studies assumed the use of single aiding measurement. However, navigation systems often use multiple aiding sensors to improve estimation performance in applications. When left- and right-invariant measurements are used simultaneously, implementing the LIEKF or RIEKF with a centralized filter structure causes some terms of the measurement matrix dependent on the current estimates, which results in IEKF losing its trajectory independent advantage. On the other hand, when a decentralized filter structure, especially a federated filter structure, is applied, the estimation becomes trajectory independent through separate update of each measurement in the local filters. This thesis proposes a fusion method of IEKF using the federated filter structure for simultaneous use of left- and right-invariant measurements. The performance of the proposed fusion method is validated through simulations. The error convergence and accuracy of the proposed method and the centralized IEKF are compared.본 논문에서는 다수의 보정 센서를 사용하는 항법 시스템을 위한 연합형 불변 확장 칼만필터의 구현을 제안한다. 불변 확장 칼만필터는 일반적인 확장 칼만필터의 프레임워크는 그대로 사용하면서 상태변수를 행렬 리 그룹 상에서 정의하여 확장 칼만필터 대비 우수한 추정 성능을 가진다. 좌불변 혹은 우불변 측정치를 사용할 때 이에 적합한 불변 오차 정의를 선택하여 구현한다면 궤적 독립적인 추정이 가능하다. 대부분의 불변 확장 칼만필터에 대한 연구들은 단일 보정 센서의 사용을 가정한다. 그런데 실제 적용에 있어, 항법 시스템은 추정 성능을 향상하기 위해 다수의 보정 센서를 사용하는 경우가 많다. 좌불변 측정치와 우불변 측정치가 모두 사용되는 상황이라면, 중앙집중형 좌불변 확장 칼만필터와 우불변 확장 칼만필터는 모두 추정치에 영향을 받는 측정치 행렬을 사용하게 된다. 이로 인해 불변 확장칼만필터가 갖는 가장 큰 장점인 궤적 독립 특성을 잃는다. 반면에 연합형 필터 구조를 사용하면 각 측정치에 할당된 국소 필터에서 적절한 필터로 각 측정치를 처리할 수 있다. 따라서 이 논문에서는 불변 확장 칼만필터의 연합형 구조 구현을 제안한다. 리 그룹의 성질을 고려하는 적절한 융합 방식을 사용한 구조를 제안하며, 그 성능을 시뮬레이션을 통해 확인한다. 제안한 방식과 중앙집중형 불변 확장 칼만필터를 수렴성과 추정 정확도의 관점에서 비교하였다.Chapter 1 Introduction 1 1.1 Motivation 1 1.2 Objectives and contributions 3 Chapter 2 Related Works 5 2.1 Invariant extended Kalman filter (IEKF) 5 2.2 Federated filter 7 Chapter 3 Framework of invariant EKF 9 3.1 Mathematical preliminaries 9 3.2 States and model 10 3.2.1 Matrix Lie group states 10 3.2.2 Process model 12 3.2.3 Measurement model 15 3.2.4 Adjoint 16 3.3 IEKF for inertial navigation 17 3.3.1 IMU states and error states 17 3.3.2 Process model 20 3.3.3 Measurement model 22 3.3.4 Adjoint transformation 27 Chapter 4 IEKF Using Multiple Measurements 28 4.1 Centralized filter implementation 29 4.1.1 Centralized LIEKF 30 4.1.2 Centralized RIEKF 32 4.2 Federated filter implementation 34 4.2.1 Overall structure 34 4.2.2 Fusion process 39 4.3 Numerical simulations 40 4.3.1 Convergence test 43 4.3.2 Comparison of centralized IEKF and EKF 48 4.3.3 Comparison of IEKF and the proposed method 52 Chapter 5 Conclusion 60 5.1.1 Conclusion and summary 60 5.1.2 Future works 61 Bibliography 62 국문초록 68석

    To Compute or not to Compute? Adaptive Smart Sensing in Resource-Constrained Edge Computing

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    We consider a network of smart sensors for edge computing application that sample a signal of interest and send updates to a base station for remote global monitoring. Sensors are equipped with sensing and compute, and can either send raw data or process them on-board before transmission. Limited hardware resources at the edge generate a fundamental latency-accuracy trade-off: raw measurements are inaccurate but timely, whereas accurate processed updates are available after computational delay. Also, if sensor on-board processing entails data compression, latency caused by wireless communication might be higher for raw measurements. Hence, one needs to decide when sensors should transmit raw measurements or rely on local processing to maximize overall network performance. To tackle this sensing design problem, we model an estimation-theoretic optimization framework that embeds computation and communication delays, and propose a Reinforcement Learning-based approach to dynamically allocate computational resources at each sensor. Effectiveness of our proposed approach is validated through numerical simulations with case studies motivated by the Internet of Drones and self-driving vehicles.Comment: 14 pages, 14 figures; submitted to IEEE TNSM; revised versio

    Distributed cloud-edge analytics and machine learning for transportation emissions estimation

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    (English) In recent years IoT and Smart Cities have become a popular paradigm of computing that is based on network-enabled devices connected providing different functionalities, from sensor measures to domotic actions. With this paradigm, it is possible to provide to the stakeholders near-realtime information of the field, e.g. the current pollution of the city. Along with the mentioned paradigms, Fog Computing enables computation near the sensors where the data is produced, i.e. Edge nodes. This paradigm provides low latency and fault tolerance given the possible independence of the sensor devices. Moreover, pushing this computation enables derived results in a near-realtime fashion. This ability to push the computation to where the data is produced can be beneficial in many situations, however it also requires to include in the Edge the data preparation processes that ensure the fitness for use of the data as the incoming data can be erroneous. Given this situation, Machine Learning can be useful to correct data and also to produce predictions of the future values. Even though there have been studies regarding on the uses of data at the Edge, to our knowledge there is no evaluation of the different modeling situations and the viability of the approach. Therefore, this thesis aims to evaluate the possibility of building a distributed system that ensures the fitness for use of the incoming data through Machine Learning enabled Data Preparation, estimates the emissions and predicts the future status of the city in a near-realtime fashion. We evaluate the viability through three contributions. The first contribution focuses on forecasting in a distributed scenario with road traffic dataset for evaluation. It provides a robust solution to build a central model. This approach is based on Federated Learning, which allows training models at the Edge nodes and then merging them centrally. This way the models in the Edge can be independent but also can be synchronized. The results show the trade-off between accuracy versions training time and a comparison between low-powered devices versus server-class machines. These analyses show that it is viable to use Machine Learning with this paradigm. The second contribution focuses on a particular use case of ship emission estimation. To estimate exhaust emissions data must be correct, which is not always the case. This contribution explores the different techniques available to correct ship registry data and proposes the usage of simple Machine Learning techniques to do imputation of missing or erroneous values. This contribution analyzes the different variables and their relationship to provide the practitioners with guidelines for correction and data treatment. The results show that with classical Machine Learning it is possible to improve the state-of-the-art results. Moreover, as these algorithms are simple enough, they can be used in an Edge device if required. The third contribution focuses on generating new variables from the ones available with a ship trace dataset obtained from the Automatic Identification System (AIS). We use a pipeline of two different methods, a Neural Networks and a clustering algorithm, to group movements into movement patterns or \emph{behaviors}. We test the predicting power of these behaviors to predict ship type, main engine power, and navigational status. The prediction of the main engine power is compared against the standard technique used in ship emission estimation when the ship registry is missing. Our approach was able to detect 45\% of the otherwise undetected emissions if the baseline method was to be used. As ship navigational status is prone to error, the behaviors found are proposed as an alternative variable based in robust data. These contributions build a framework that can distribute the learning processes and that resists network failures in low-powered devices.(Español) En los últimos años, IoT y las Smart Cities se han convertido en un paradigma popular de computación que se basa en dispositivos conectados a la red que proporcionan diferentes funcionalidades, desde medidas de sensores hasta acciones domóticas. Con este paradigma, es posible tener información en casi tiempo real, como por ejemplo la contaminación actual de la ciudad. Junto con los paradigmas mencionados, Fog Computing permite computar cerca de donde se producen los datos, es decir, los nodos Edge. Este paradigma proporciona baja latencia y tolerancia a fallos dada la posible independencia de los dispositivos sensores. Esta posibilidad puede ser beneficiosa en muchas situaciones, sin embargo, requiere incluir en el Edge los procesos de preparación de datos que aseguran la idoneidad para su uso, ya que los datos entrantes pueden ser erróneos. Ante esta situación, el Machine Learning es útil para corregir datos y también para producir predicciones de los valores futuros. A pesar de que se han realizado estudios sobre los usos de los datos en el Edge, hasta donde sabemos, no hay una evaluación de las diferentes situaciones de modelado y la viabilidad del enfoque. Por lo tanto, esta tesis tiene como objetivo evaluar la posibilidad de construir un sistema distribuido que garantice que los datos sean correctos a través de su preparación con Machine Learning. También el sistema deberá estimar las emisiones y predecir el estado futuro de la ciudad de una manera casi en tiempo real. La viabilidad se evalúa a través a través de tres contribuciones. La primera contribución se centra en escenario distribuido con un conjunto de datos de tráfico vial que proporciona una solución robusta para construir un modelo central. Este enfoque se basa en Federated Learning, que permite entrenar modelos en los nodos Edge y luego fusionarlos de forma centralizada. De esta manera, los modelos en el Edge pueden ser independientes, pero también se pueden sincronizar. Los resultados muestran la comparación de la precisión con un modelo central y uno distribuido y una comparación con dispositivos de bajo consumos contra servidores. Estos análisis muestran que es viable utilizar el Machine Learning en este paradigma. La segunda contribución se centra en un caso de uso particular de estimación de las emisiones de barcos. Para estimar las emisiones, los datos deben ser correctos, cosa que no siempre pasa. Esta contribución explora las diferentes técnicas disponibles para corregir los datos del registro de barcos y propone el uso de técnicas simples de Machine Learning para hacer imputación de valores faltantes o erróneos. Esta contribución analiza las diferentes variables y su relación para proporcionar a los profesionales pautas para la corrección y el tratamiento de datos. Los resultados muestran que con el Machine Learning clásico es posible mejorar los resultados frente a métodos del estado del arte. Además, como estos algoritmos son lo suficientemente simples como para poder utilizarse en dispositivos Edge. La tercera contribución se centra en generar nuevas variables a partir de las disponibles con un conjunto de datos de trazabilidad de barcos obtenido del Sistema AIS. Esto se hace utilizando en conjunto una red neuronal y un algoritmo de agrupación para agrupar los movimientos en patrones de movimiento o comportamientos. Se evalúa su funcionamiento para predecir el tipo de barco, la potencia del motor principal y el estado de navegación. Con esta predicción, nuestro sistema es capaz de detectar el 45% de las emisiones que no se detectan con métodos standard. Como el estado de navegación del barco es propenso a errores, los comportamientos encontrados se proponen como una variable alternativa basada en datos robustos. Estas contribuciones constituyen un marco para distribuir los procesos de aprendizaje y que resiste errores en la red con dispositivos de bajo consumo.Arquitectura de computador

    Traffic Prediction using Artificial Intelligence: Review of Recent Advances and Emerging Opportunities

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    Traffic prediction plays a crucial role in alleviating traffic congestion which represents a critical problem globally, resulting in negative consequences such as lost hours of additional travel time and increased fuel consumption. Integrating emerging technologies into transportation systems provides opportunities for improving traffic prediction significantly and brings about new research problems. In order to lay the foundation for understanding the open research challenges in traffic prediction, this survey aims to provide a comprehensive overview of traffic prediction methodologies. Specifically, we focus on the recent advances and emerging research opportunities in Artificial Intelligence (AI)-based traffic prediction methods, due to their recent success and potential in traffic prediction, with an emphasis on multivariate traffic time series modeling. We first provide a list and explanation of the various data types and resources used in the literature. Next, the essential data preprocessing methods within the traffic prediction context are categorized, and the prediction methods and applications are subsequently summarized. Lastly, we present primary research challenges in traffic prediction and discuss some directions for future research.Comment: Published in Transportation Research Part C: Emerging Technologies (TR_C), Volume 145, 202

    Advances in Batteries, Battery Modeling, Battery Management System, Battery Thermal Management, SOC, SOH, and Charge/Discharge Characteristics in EV Applications

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    The second-generation hybrid and Electric Vehicles are currently leading the paradigm shift in the automobile industry, replacing conventional diesel and gasoline-powered vehicles. The Battery Management System is crucial in these electric vehicles and also essential for renewable energy storage systems. This review paper focuses on batteries and addresses concerns, difficulties, and solutions associated with them. It explores key technologies of Battery Management System, including battery modeling, state estimation, and battery charging. A thorough analysis of numerous battery models, including electric, thermal, and electro-thermal models, is provided in the article. Additionally, it surveys battery state estimations for a charge and health. Furthermore, the different battery charging approaches and optimization methods are discussed. The Battery Management System performs a wide range of tasks, including as monitoring voltage and current, estimating charge and discharge, equalizing and protecting the battery, managing temperature conditions, and managing battery data. It also looks at various cell balancing circuit types, current and voltage stressors, control reliability, power loss, efficiency, as well as their advantages and disadvantages. The paper also discusses research gaps in battery management systems.publishedVersio

    Applications in Electronics Pervading Industry, Environment and Society

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    This book features the manuscripts accepted for the Special Issue “Applications in Electronics Pervading Industry, Environment and Society—Sensing Systems and Pervasive Intelligence” of the MDPI journal Sensors. Most of the papers come from a selection of the best papers of the 2019 edition of the “Applications in Electronics Pervading Industry, Environment and Society” (APPLEPIES) Conference, which was held in November 2019. All these papers have been significantly enhanced with novel experimental results. The papers give an overview of the trends in research and development activities concerning the pervasive application of electronics in industry, the environment, and society. The focus of these papers is on cyber physical systems (CPS), with research proposals for new sensor acquisition and ADC (analog to digital converter) methods, high-speed communication systems, cybersecurity, big data management, and data processing including emerging machine learning techniques. Physical implementation aspects are discussed as well as the trade-off found between functional performance and hardware/system costs

    Sensors Fault Diagnosis Trends and Applications

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    Fault diagnosis has always been a concern for industry. In general, diagnosis in complex systems requires the acquisition of information from sensors and the processing and extracting of required features for the classification or identification of faults. Therefore, fault diagnosis of sensors is clearly important as faulty information from a sensor may lead to misleading conclusions about the whole system. As engineering systems grow in size and complexity, it becomes more and more important to diagnose faulty behavior before it can lead to total failure. In the light of above issues, this book is dedicated to trends and applications in modern-sensor fault diagnosis

    A Two-Level Information Modelling Translation Methodology and Framework to Achieve Semantic Interoperability in Constrained GeoObservational Sensor Systems

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    As geographical observational data capture, storage and sharing technologies such as in situ remote monitoring systems and spatial data infrastructures evolve, the vision of a Digital Earth, first articulated by Al Gore in 1998 is getting ever closer. However, there are still many challenges and open research questions. For example, data quality, provenance and heterogeneity remain an issue due to the complexity of geo-spatial data and information representation. Observational data are often inadequately semantically enriched by geo-observational information systems or spatial data infrastructures and so they often do not fully capture the true meaning of the associated datasets. Furthermore, data models underpinning these information systems are typically too rigid in their data representation to allow for the ever-changing and evolving nature of geo-spatial domain concepts. This impoverished approach to observational data representation reduces the ability of multi-disciplinary practitioners to share information in an interoperable and computable way. The health domain experiences similar challenges with representing complex and evolving domain information concepts. Within any complex domain (such as Earth system science or health) two categories or levels of domain concepts exist. Those concepts that remain stable over a long period of time, and those concepts that are prone to change, as the domain knowledge evolves, and new discoveries are made. Health informaticians have developed a sophisticated two-level modelling systems design approach for electronic health documentation over many years, and with the use of archetypes, have shown how data, information, and knowledge interoperability among heterogenous systems can be achieved. This research investigates whether two-level modelling can be translated from the health domain to the geo-spatial domain and applied to observing scenarios to achieve semantic interoperability within and between spatial data infrastructures, beyond what is possible with current state-of-the-art approaches. A detailed review of state-of-the-art SDIs, geo-spatial standards and the two-level modelling methodology was performed. A cross-domain translation methodology was developed, and a proof-of-concept geo-spatial two-level modelling framework was defined and implemented. The Open Geospatial Consortium’s (OGC) Observations & Measurements (O&M) standard was re-profiled to aid investigation of the two-level information modelling approach. An evaluation of the method was undertaken using II specific use-case scenarios. Information modelling was performed using the two-level modelling method to show how existing historical ocean observing datasets can be expressed semantically and harmonized using two-level modelling. Also, the flexibility of the approach was investigated by applying the method to an air quality monitoring scenario using a technologically constrained monitoring sensor system. This work has demonstrated that two-level modelling can be translated to the geospatial domain and then further developed to be used within a constrained technological sensor system; using traditional wireless sensor networks, semantic web technologies and Internet of Things based technologies. Domain specific evaluation results show that twolevel modelling presents a viable approach to achieve semantic interoperability between constrained geo-observational sensor systems and spatial data infrastructures for ocean observing and city based air quality observing scenarios. This has been demonstrated through the re-purposing of selected, existing geospatial data models and standards. However, it was found that re-using existing standards requires careful ontological analysis per domain concept and so caution is recommended in assuming the wider applicability of the approach. While the benefits of adopting a two-level information modelling approach to geospatial information modelling are potentially great, it was found that translation to a new domain is complex. The complexity of the approach was found to be a barrier to adoption, especially in commercial based projects where standards implementation is low on implementation road maps and the perceived benefits of standards adherence are low. Arising from this work, a novel set of base software components, methods and fundamental geo-archetypes have been developed. However, during this work it was not possible to form the required rich community of supporters to fully validate geoarchetypes. Therefore, the findings of this work are not exhaustive, and the archetype models produced are only indicative. The findings of this work can be used as the basis to encourage further investigation and uptake of two-level modelling within the Earth system science and geo-spatial domain. Ultimately, the outcomes of this work are to recommend further development and evaluation of the approach, building on the positive results thus far, and the base software artefacts developed to support the approach

    Symmetry-Adapted Machine Learning for Information Security

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    Symmetry-adapted machine learning has shown encouraging ability to mitigate the security risks in information and communication technology (ICT) systems. It is a subset of artificial intelligence (AI) that relies on the principles of processing future events by learning past events or historical data. The autonomous nature of symmetry-adapted machine learning supports effective data processing and analysis for security detection in ICT systems without the interference of human authorities. Many industries are developing machine-learning-adapted solutions to support security for smart hardware, distributed computing, and the cloud. In our Special Issue book, we focus on the deployment of symmetry-adapted machine learning for information security in various application areas. This security approach can support effective methods to handle the dynamic nature of security attacks by extraction and analysis of data to identify hidden patterns of data. The main topics of this Issue include malware classification, an intrusion detection system, image watermarking, color image watermarking, battlefield target aggregation behavior recognition model, IP camera, Internet of Things (IoT) security, service function chain, indoor positioning system, and crypto-analysis
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