Li-ion batteries monitoring for electrified vehicles applications

L'abstract è presente nell'allegato / the abstract is in the attachmen

Real-time Energy Management System of Battery-Supercapacitor in Electric vehicles

This thesis presents the design, simulation and experimental validation of an Energy Management System (EMS) for a Hybrid Energy Storage System (HESS) composed of lithium ion batteries and Supercapacitors (SCs) in electric vehicles. The aim of the EMS is to split the power demand considering the weaknesses and strengths or the power sources. The HESS requires an EMS to determine power missions for the battery and SC in real time, where the SC is commanded to assist the battery during high power demand and recover the energy generated during braking. Frequency sharing techniques have been proposed by researchers to achieve this objective, including the Discrete Wavelet Transform (DWT) and conventional filtration methods (low and high pass filters). However, filtration approaches can introduce delay (milliseconds to tens of seconds) in the frequency components which undermines the hybridisation advantages. Hence, the selection of the filtration technique and filter design are crucial to the system's performance. Researchers have proposed power demand prediction methodologies to deal with time delay, however, the advantages and drawbacks of using such methods have not been investigated thoroughly, particularly whether time delay compensation and its inherent prediction error improves the system performance, efficiency, and timely SC contribution during the motoring and braking stages. This work presents a fresh perspective to this research field by introducing a novel approach that deals with delay without complicated prediction algorithms and improves the SC contribution during the motoring and braking stages while reducing energy losses in the system. The proposed EMS allows the SC to provide timely assistance during motoring and to recover the braking energy generated. A charging strategy controls energy circulation between the battery and SC to keep the SC charge availability during the whole battery discharge cycle. The performance and efficiency of the HESS is improved when compared to the traditional use of conventional filtration techniques and the DWT. Results show that the proposed EMS method improves the energy efficiency of the HESS. For the US06 driving cycle, the energy efficiency is 91.6%. This is superior to the efficiency obtained with an EMS based on a high pass filter (41.3%), an EMS based on DWT high frequency component (30.3%) and an EMS based on the predicted DWT high frequency component (41%)

Design of a unmanned aerial vehicle

Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1998.Includes bibliographical references.by Jean-Marc C. Hauss.M.Eng

3D and 4D Characterisation of Lithium-Ion Battery Electrode Microstructures using X-ray Tomography

There is a direct link between electrode microstructure and their performance in lithium-ion batteries (LIBs); however, this relationship remains poorly understood. By utilising tomographic X-ray imaging techniques, it is possible to characterise LIB electrode microstructure in three dimensions. Moreover, extending these imaging techniques to explore changes in these materials gives rise to the notion of “four-dimensional” (4D) tomography to study microstructural evolution with time. This work focused on characterising, both qualitatively and quantitatively, the three-dimensional (3D) microstructure of LIB electrode materials at multiple length and time scales with the aid of laboratory and synchrotron X-ray sources. The suitability and reliability of direct 3D microstructural analysis for quantifying LIB electrodes was demonstrated by comparing it with stereological methods, which are shown to introduce bias when applied to inhomogeneous 3D microstructures. Silicon (Si) and metallic lithium (Li) are highly energy-dense electrode materials and promising candidates for use in LIBs; however, they experience significant microstructural degradation upon electrochemical cycling. Using a custom-built, X-ray transparent in-situ electrochemical cell, 4D characterisation of the microstructural evolution and degradation within the aforementioned electrode materials was performed both in-situ and in-operando. Phase transformation, fracture formation and propagation within individual Si particles was visualized and tracked in 3D during the course of a half-cell discharge. At a higher X-ray imaging resolution, microstructural evolution in Si microparticles as a result of repeated cycling was captured and quantified in 3D. Visualisation of formation and growth of pits and mossy lithium deposits along metallic Li electrode surfaces was also presented. Finally, an X-ray contrast-enhancement approach for imaging lowly attenuating electrode materials such as graphite was also demonstrated. This work has demonstrated X-ray tomography as a diagnostic tool for providing valuable insight into electrode microstructure which can aid the efficient design of these electrode materials in future generation LIB systems

Underwater Vehicles

For the latest twenty to thirty years, a significant number of AUVs has been created for the solving of wide spectrum of scientific and applied tasks of ocean development and research. For the short time period the AUVs have shown the efficiency at performance of complex search and inspection works and opened a number of new important applications. Initially the information about AUVs had mainly review-advertising character but now more attention is paid to practical achievements, problems and systems technologies. AUVs are losing their prototype status and have become a fully operational, reliable and effective tool and modern multi-purpose AUVs represent the new class of underwater robotic objects with inherent tasks and practical applications, particular features of technology, systems structure and functional properties

Evolutionary robotics in high altitude wind energy applications

Recent years have seen the development of wind energy conversion systems that can exploit the superior wind resource that exists at altitudes above current wind turbine technology. One class of these systems incorporates a flying wing tethered to the ground which drives a winch at ground level. The wings often resemble sports kites, being composed of a combination of fabric and stiffening elements. Such wings are subject to load dependent deformation which makes them particularly difficult to model and control. Here we apply the techniques of evolutionary robotics i.e. evolution of neural network controllers using genetic algorithms, to the task of controlling a steerable kite. We introduce a multibody kite simulation that is used in an evolutionary process in which the kite is subject to deformation. We demonstrate how discrete time recurrent neural networks that are evolved to maximise line tension fly the kite in repeated looping trajectories similar to those seen using other methods. We show that these controllers are robust to limited environmental variation but show poor generalisation and occasional failure even after extended evolution. We show that continuous time recurrent neural networks (CTRNNs) can be evolved that are capable of flying appropriate repeated trajectories even when the length of the flying lines are changing. We also show that CTRNNs can be evolved that stabilise kites with a wide range of physical attributes at a given position in the sky, and systematically add noise to the simulated task in order to maximise the transferability of the behaviour to a real world system. We demonstrate how the difficulty of the task must be increased during the evolutionary process to deal with this extreme variability in small increments. We describe the development of a real world testing platform on which the evolved neurocontrollers can be tested

NASA Tech Briefs, March 1995

This issue contains articles with a special focus on Computer-Aided design and engineering amd a research report on the Ames Research Center. Other subjects in this issue are: Electronic Components and Circuits, Electronic Systems, Physical Sciences, Materials, Computer Programs, Mechanics, Machinery, Manufacturing/Fabrication, Mathematics and Information Sciences and Life Science