73 research outputs found
Composite Disturbance Filtering: A Novel State Estimation Scheme for Systems With Multi-Source, Heterogeneous, and Isomeric Disturbances
State estimation has long been a fundamental problem in signal processing and
control areas. The main challenge is to design filters with ability to reject
or attenuate various disturbances. With the arrival of big data era, the
disturbances of complicated systems are physically multi-source, mathematically
heterogenous, affecting the system dynamics via isomeric (additive,
multiplicative and recessive) channels, and deeply coupled with each other. In
traditional filtering schemes, the multi-source heterogenous disturbances are
usually simplified as a lumped one so that the "single" disturbance can be
either rejected or attenuated. Since the pioneering work in 2012, a novel state
estimation methodology called {\it composite disturbance filtering} (CDF) has
been proposed, which deals with the multi-source, heterogenous, and isomeric
disturbances based on their specific characteristics. With the CDF, enhanced
anti-disturbance capability can be achieved via refined quantification,
effective separation, and simultaneous rejection and attenuation of the
disturbances. In this paper, an overview of the CDF scheme is provided, which
includes the basic principle, general design procedure, application scenarios
(e.g. alignment, localization and navigation), and future research directions.
In summary, it is expected that the CDF offers an effective tool for state
estimation, especially in the presence of multi-source heterogeneous
disturbances
Path-based splitting methods for SDEs and machine learning for battery lifetime prognostics
In the first half of this Thesis, we present the numerical analysis of splitting methods for
stochastic differential equations (SDEs) using a novel path-based approach. The application
of splitting methods to SDEs can be viewed as replacing the driving Brownian-time path
with a piecewise linear path, producing a ‘controlled-differential-equation’ (CDE). By Taylor
expansion of the SDE and resulting CDE, we show that the global strong and weak errors of
splitting schemes can be obtained by comparison of the iterated integrals in each. Matching
all integrals up to order p+1 in expectation will produce a weak order p+0.5 scheme, and in
addition matching the integrals up to order p+0.5 strongly will produce a strong order p
scheme. In addition, we present new splitting methods utilising the ‘space-time’ L´evy area
of Brownian motion which obtain global strong Oph1.5q and Oph2q weak errors for a class
of SDEs satisfying a commutativity condition. We then present several numerical examples
including Multilevel Monte Carlo.
In the second half of this Thesis, we present a series of papers focusing on lifetime prognostics
for lithium-ion batteries. Lithium-ion batteries are fuelling the advancing renewable-energy
based world. At the core of transformational developments in battery design, modelling and
management is data. We start with a comprehensive review of publicly available datasets.
This is followed by a study which explores the evolution of internal resistance (IR) in cells,
introducing the original concept of ‘elbows’ for IR. The IR of cells increases as a cell degrades
and this often happens in a non-linear fashion: where early degradation is linear until an
inflection point (the elbow) is reached followed by increased rapid degradation. As a follow up
to the exploration of IR, we present a model able to predict the full IR and capacity evolution
of a cell from one charge/discharge cycle. At the time of publication, this represented a
significant reduction (100x) in the number of cycles required for prediction. The published
paper was the first to show that such results were possible.
In the final paper, we consider
experimental design for battery testing. Where we focus on the important question of how
many cells are required to accurately capture statistical variation
Data driven techniques for on-board performance estimation and prediction in vehicular applications.
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Data-Driven Methods for the State of Charge Estimation of Lithium-Ion Batteries: An Overview
In recent years, there has been a noticeable shift towards electric mobility and an increasing emphasis on integrating renewable energy sources. Consequently, batteries and their management have been prominent in this context. A vital aspect of the BMS revolves around accurately determining the battery pack’s SOC. Notably, the advent of advanced microcontrollers and the availability of extensive datasets have contributed to the growing popularity and practicality of data-driven methodologies. This study examines the developments in SOC estimation over the past half-decade, explicitly focusing on data-driven estimation techniques. It comprehensively assesses the performance of each algorithm, considering the type of battery and various operational conditions. Additionally, intricate details concerning the models’ hyperparameters, including the number of layers, type of optimiser, and neuron, are provided for thorough examination. Most of the models analysed in the paper demonstrate strong performance, with both the MAE and RMSE for the estimation of SOC hovering around 2% or even lower
Robust Approaches to Nonlinear Filtering with Applications to Navigation
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
Resilient dynamic state estimation for power system using Cauchy-kernel-based maximum correntropy cubature Kalman filter
Accurate estimation of dynamic states is the key to monitoring power system operating conditions and controlling transient stability. The inevitable non-Gaussian noise and randomly occurring denial-of-service (DoS) attacks may, however, deteriorate the performance of standard filters seriously. To deal with these issues, a novel resilient cubature Kalman filter based on the Cauchy kernel maximum correntropy (CKMC) optimal criterion approach (termed CKMC-CKF) is developed, in which the Cauchy kernel function is used to describe the distance between vectors. Specifically, the errors of state and measurement in the cost function are unified by a statistical linearization technique, and the optimal estimated state is acquired by the fixed-point iteration method. Because of the salient thick-tailed feature and the insensitivity to the kernel bandwidth (KB) of Cauchy kernel function, the proposed CKMC-CKF can effectively mitigate the adverse effect of non-Gaussian noise and DoS attacks with better numerical stability. Finally, the efficacy of the proposed method is demonstrated on the standard IEEE 39-bus system under various abnormal conditions. Compared with standard cubature Kalman filter (CKF) and maximum correntropy criterion CKF (MCC-CKF), the proposed algorithm reveals better estimation accuracy and stronger resilience
Design and implementation of resilient attitude estimation algorithms for aerospace applications
Satellite attitude estimation is a critical component of satellite attitude determination and control systems, relying on highly accurate sensors such as IMUs, star trackers, and sun sensors. However, the complex space environment can cause sensor performance degradation or even failure. To address this issue, FDIR systems are necessary. This thesis presents a novel approach to satellite attitude estimation that utilizes an InertialNavigation System (INS) to achieve high accuracy with the low computational load. The algorithm is based on a two-layer Kalman filter, which incorporates the quaternion estimator(QUEST) algorithm, FQA, Linear interpolation (LERP)algorithms, and KF. Moreover, the thesis proposes an FDIR system for the INS that can detect and isolate faults and recover the system safely. This system includes two-layer fault detection with isolation and two-layered recovery, which utilizes an Adaptive Unscented Kalman Filter (AUKF), QUEST algorithm, residual generators, Radial Basis Function (RBF) neural
networks, and an adaptive complementary filter (ACF). These two fault detection layers aim
to isolate and identify faults while decreasing the rate of false alarms. An FPGA-based FDIR
system is also designed and implemented to reduce latency while maintaining normal resource
consumption in this thesis. Finally, a Fault Tolerance Federated Kalman Filter (FTFKF) is proposed to fuse the output from INS and the CNS to achieve high precision and robust attitude estimation.The findings of this study provide a solid foundation for the development of FDIR systems for various applications such as robotics, autonomous vehicles, and unmanned aerial vehicles, particularly for satellite attitude estimation. The proposed INS-based approach with the FDIR system has demonstrated high accuracy, fault tolerance, and low computational load, making
it a promising solution for satellite attitude estimation in harsh space environment
State estimators in soft sensing and sensor fusion for sustainable manufacturing
State estimators, including observers and Bayesian filters, are a class of model-based algorithms for estimating variables in a dynamical system given sensor measurements of related system states. They can be used to derive fast and accurate estimates of system variables which cannot be measured directly (’soft sensing’) or for which only noisy, intermittent, delayed, indirect or unreliable measurements are available, perhaps from multiple sources (’sensor fusion’). In this paper we introduce the concepts and main methods of state estimation and review recent applications in improving the sustainability of manufacturing processes. It is shown that state estimation algorithms can play a key role in manufacturing systems to accurately monitor and control processes to improve efficiencies, lower environmental impact, enhance product quality, improve the feasibility of processing more sustainable raw materials, and ensure safer working environments for humans. We discuss current and emerging trends in using state estimation as a framework for combining physical knowledge with other sources of data for monitoring and control of distributed manufacturing systems
Advanced Battery Technologies: New Applications and Management Systems
In recent years, lithium-ion batteries (LIBs) have been increasingly contributing to the development of novel engineering systems with energy storage requirements. LIBs are playing an essential role in our society, as they are being used in a wide variety of applications, ranging from consumer electronics, electric mobility, renewable energy storage, biomedical applications, or aerospace systems. Despite the remarkable achievements and applicability of LIBs, there are several features within this technology that require further research and improvements. In this book, a collection of 10 original research papers addresses some of those key features, including: battery testing methodologies, state of charge and state of health monitoring, and system-level power electronics applications. One key aspect to emphasize when it comes to this book is the multidisciplinary nature of the selected papers. The presented research was developed at university departments, institutes and organizations of different disciplines, including Electrical Engineering, Control Engineering, Computer Science or Material Science, to name a few examples. The overall result is a book that represents a coherent collection of multidisciplinary works within the prominent field of LIBs
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