1,721,276 research outputs found
A Simplified Model based State-of-Charge Estimation Approach for Lithium-ion Battery with Dynamic Linear Model
Full text linkThe performance of model based State-of-Charge (SOC) estimation method relies on an accurate battery model. Nonlinear models are thus proposed to accurately describe the external characteristics of the Lithium-ion (Li-ion) battery. The nonlinear estimation algorithms and online parameter identification methods are needed to guarantee the accuracy of the model based SOC estimation with nonlinear battery models. A new approach forming a dynamic linear battery model is proposed in this paper, which enables the application of the linear Kalman filter for SOC estimation and also avoids the usage of online parameter identification methods. With a moving window technology, Partial Least Squares (PLS) regression is able to establish a series of piecewise linear battery models automatically. One element state space equation is then obtained to estimate the SOC from the linear Kalman filter. The experiments on a LiFePO4 battery prove the effectiveness of the proposed method compared with the Extended Kalman Filter (EKF) with two Resistance and Capacitance (RC) Equivalent Circuit Model (ECM) and the Adaptive Unscented Kalman Filter (AUKF) with Least Squares Support Vector Machines (LSSVM)
A Novel Multiple Correction Approach for Fast Open Circuit Voltage Prediction of Lithium-ion Battery
No full textThis paper proposes a novel fast open circuit voltage prediction approach for Lithium-ion battery, which is potential to facilitate a convenient battery modeling and states estimation in the energy storage system. Open circuit voltage measurement suffers from a long relaxation time (several hours, even days) to reach the thermodynamic equilibrium of the battery. On the basis of the feedback control theory, the proposed multiple correction approach utilizes the constrained nonlinear optimization of the power function in each curve fitting step. The voltage measurement in a short period is divided into several segments to correct the voltage prediction multiple times with the feedback errors after each curve fitting. The similarity between the shape of the power function and the variation of the terminal voltage during the relaxation time is utilized. The proposed method can speed up the time-consuming open circuit voltage measurement and predict the open circuit voltage with high accuracy. Experimental tests on a LiFePO4 battery prove the validation and effectiveness of the proposed method in accurately predicting the open circuit voltage within a very short relaxation time (less than 15 min)
Data-driven Modeling of Li-ion Battery based on the Manufacturer Specifications and Laboratory Measurements
No full textAccurate modeling of Lithium-ion battery is essential in the development and testing of state estimation and lifetime prediction algorithms. The desired features of the model include flexibility, fast development, accuracy and reliability. There are many different ways to model a battery, depending on the level of abstraction desired, the data available and the target application environment. This paper shows how to extract equivalent circuit model parameters from manufacturer datasheets and laboratory measurement to build robust battery simulation models. A step-by-step methodology for data preparation is presented for both datasheet and measurement-based methods. The benefits and the disadvantages of both approaches are also discussed. A simple equivalent circuit model is firstly derived from manufacturer specification and its robustness is enhanced by collecting more extensive experimental data in the laboratory. Furthermore, an advanced model to better capture the battery dynamics is developed. The aging effects are added to this battery model, to reflect the internal parameters variation according to the health condition of the battery. To measure the accuracy of the developed models, the relative error is computed. An initial relative error of 2.8% of the model build with manufacturer specifications is reduced to 1.0% using laboratory measurements and finally to less than 0.4% by incorporating aging effects
State of health estimation based on improved double-extended Kalman filter
No full textIn this chapter, the state of health (SOH) of aviation lithium-ion batteries is estimated from the perspective of ohmic internal resistance and capacity. The dual time scale Adaptive double extended kalman filter (ADEKF) algorithm based on extended Kalman filter is studied, and adaptive noise correction is introduced to solve the estimation error problem caused by variable system noise. State of charge (SOC) and SOH are estimated from two-time scales to avoid the impact of the fluctuation of SOC estimation on the capacity, resulting in a smaller time scale. Obtain ohmic internal resistance through RLS online parameter identification, and then obtain SOH value. Considering the advantages and disadvantages of ohmic resistance and capacitance estimation, a two-factor SOH estimation method is proposed. This method combines ohmic resistance and capacitance estimation to obtain the optimal solution for the health state.</p
State of charge estimation strategy based on fractional-order model
No full textThis chapter designs an adaptive fractional-order extended Kalman filtering algorithm. The combination of this equivalent circuit model and the estimation algorithm achieves accurate prediction of SOC (state of charge) in real time. This chapter first introduces the baseline Kalman filter algorithm and then applies it to the state estimation of lithium-ion batteries; a fractional-order model with a fractional-order algorithm is then designed based on the extended Kalman filtering to achieve the estimation of the battery SOC. A fixed-length memory factor is used in the fractional-order algorithm to reduce the disadvantages of high computational complexity in the fractional-order process to improve the effective use of historical data in the calculation of fractional-order derivatives. Finally, the validation analysis of the model is completed.</p
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Lithium-ion battery hysteresis characteristics and modeling
No full textIn this chapter, the experimental results of the basic characteristics of lithium-ion batteries are used as the basis of the study. The study of the voltage hysteresis effect of the battery is studied in depth, and the dependence of various hysteresis parameters of the battery and the inclusion relationship between the secondary and primary ring hysteresis are further analyzed. Based on the differences in the charge-discharge open-circuit voltage-state of charge curves of the battery hysteresis characteristics and the hysteresis effect curves at various temperatures, a secondary Prandtl-Ishlinskii (PI) hysteresis model that can accurately describe the hysteresis voltage curve is designed, and the accuracy of the model is verified by comparing the experimental data.</p
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