基于Simulink的锂电池建模仿真

针对锂离子电池SOC(荷电状态)难以估算的问题,通过对电池建立等效的Thevenin电路模型,对不同时刻的SOC的模型参数进行拟合得到动态的模型参数,在Matlab中借助Simulink建立仿真模型,采用模块化结构,建立基于卡尔曼滤波算法的电池SOC估算系统;利用测得的电池电压电流,仿真系统可直接估算出实时的电池SOC,与实际的电池SOC对比,误差保持在2.5%以内,表明该方法可以有效地估计电池的SOC,对于锂离子电池在实际应用的容量估算有着重要意义。     

基于三维激光扫描的物体重构建模

针对锂离子电池SOC(荷电状态)难以估算的问题,通过对电池建立等效的Thevenin电路模型,对不同时刻的SOC的模型参数进行拟合得到动态的模型参数,在Matlab中借助Simulink建立仿真模型,采用模块化结构,建立基于卡尔曼滤波算法的电池SOC估算系统;利用测得的电池电压电流,仿真系统可直接估算出实时的电池SOC,与实际的电池SOC对比,误差保持在2.5%以内,表明该方法可以有效的估计电池的SOC,对于锂离子电池在实际应用的容量估算有着重要意义。     

双相多孔锂离子电池液/固界面的声反射与声透射

采用传递矩阵法,同步联立改进的Biot理论,对含液固界面的双相多孔锂离子电池的超声反射与透射系数进行理论求解。考虑锂离子的摇摆特性对电极力学性能的影响,计算了对应状态下液/固界面的双相多孔锂离子电池声反射及透射系数的角度谱与频率谱。同时,构建了不同荷电状态时含单元锂离子电池的频域仿真模型,以萃取对应的超声反射及透射角度谱及频率谱,并与理论计算结果对比吻合良好。随后,以多单元锂离子电池为例,在不同的荷电状态下,分析了反射与透射系数随斜入射角度、入射波频率的变化关系,并分别指出了其角度谱及频率谱特征点随荷电状态的变化特征,为锂离子电池运行状态的超声无损测量提供了理论基础。     

流体-孔隙介质圆柱界面波传播特性

研究流体-孔隙介质圆柱界面波传播特性,分析孔隙介质孔隙率等参数对频散曲线的影响。理论上建立了无限大流体包裹孔隙介质圆柱界面波的模型,利用孔隙介质弹性波动理论,通过数值模拟计算得到流体-孔隙介质圆柱的频散曲线及时域波形,并分析了孔隙介质为开孔和闭孔状态下孔隙介质圆柱半径、孔隙率及渗透率对频散曲线的影响。结果表明,时域上斯通利波可以被明显区分开,孔隙介质圆柱半径的变化改变了圆柱尺度,孔隙率的变化改变了孔隙介质的纵、横波波速,因此对于斯通利波频散曲线的影响较大。而渗透率的变化既不改变圆柱的尺度也不改变孔隙层的纵、横波速度,因此对斯通利波频散曲线影响较小。     

脱粘缺陷对粘接结构频散特性的影响

采用全局矩阵理论,通过引入内聚强度弱化模型和弹簧模型,计算了脱粘缺陷对粘接结构频散特性的影响。分析了内聚强度缺陷、界面缺陷及混合缺陷等因素对粘接结构频散特性的影响,发现频散曲线的演化规律与材料声学性质密切相关。不同材料和不同组合,其规律有很大不同。针对各向同性粘接结构,可能通过考察特定频率段内频散模态的变化,实现对脱粘缺陷的检测。     

考虑内阻时变特性的电池状态估计方法

针对锂离子电池欧姆内阻随温度变化情况,提出了一种考虑内阻时变特性的两步无迹H∞滤波锂电池状态估计方法。首先,对锂电池和内阻抗进行分开建模,在电池Thevenin模型的基础上构建内阻抗预测模型,实时修正模型参量;接着,将无迹变换嵌入到扩展H∞滤波中,降低测量噪声对估计精度的扰动,从而提高电池荷电状态的估计精度。最后,在实验室环境下对电池进行充放电实验,分别针对降温和升温情况下的内阻值及电池端电压的估计进行了详细的实验分析,同传统方法相比,本文方法具有较高的估计精度。     

无限流体中孔隙介质圆柱周向导波的传播特性

为研究无限大流体约束的孔隙圆柱中周向导波的传播规律,分析孔隙参数对导波传播特性的影响,建立了无限流体中孔隙介质圆柱的理论模型,利用孔隙介质弹性波动理论,建立了周向导波频散方程,通过数值模拟计算得到无限流体中孔隙介质圆柱的频散曲线,探讨了圆柱半径和孔隙参数对导波传播特性的影响,并对导波的衰减特性进行了分析;通过数值计算,得到了周向导波的时域波形,讨论了孔隙参数对波形的影响.结果表明,孔隙介质圆柱半径的改变影响圆柱尺度,孔隙度的改变影响孔隙介质中体声波的波速,都对周向导波频散曲线产生一定的影响,所得到的频散曲线特征及衰减曲线与时域波形吻合.研究结果对开展无限流体中孔隙介质圆柱的超声无损评价提供了一定的理论参考.     

基于DSP的电动汽车锂电池荷电状态估算的研究与实现

锂电池荷电状态(SOC)的准确估算是电动汽车能源管理的关键技术。为了提高锂电池SOC的估算精度,将无迹卡尔曼滤波(UKF)应用于锂电池SOC估算,以减小拓展卡尔曼滤波(EKF)简单线性化带来的误差。搭建电池检测系统的硬件平台,以TMS320F28335型数字信号处理器(DSP)为主控芯片(MCU),实现电压、电流、温度的检测及UKF算法,并设计了相关的电池测试实验。实验结果表明,UKF可以实时估算锂电池SOC,估算误差在4%以内,高于传统的拓展卡尔曼滤波(EKF)。     

矢量气动声学的理论研究进展及应用

气动声学的声比拟理论以密度、声压等标量为波动算子变量,建立非齐次波动方程,描述流体运动及与边界作用诱发声音的辐射,但标量无法直接描述声能量的传播过程和途径.在流体力学研究中,标量用于描述当前当地的物质状态,而矢量用于描述质量和能量的传输.借鉴上述思想,开展了矢量气动声学的研究,概述矢量气动声学的理论研究进展及应用,主要包括:（1）以声粒子速度为变量,采用声比拟理论的思想直接从Navier-Stokes方程出发推导建立了气动声学的矢量波动方程及两种频域解;（2）综合利用声压和声粒子速度的积分解,直接求解声源周围的瞬时和有功声强矢量场,直观显示声能量的传播途径,应用于旋转声源辐射声能量的传播分析,揭示了亚音速旋转声源辐射声能量的3种传播模式:螺旋模式、声学黑洞模式和R-A模式;（3）采用球谐级数展开方法建立旋转点/紧凑声源辐射噪声的声压和声粒子速度的频域解析解,在此基础上推导了声功率谱的频域解析解,建立了识别旋转叶片声源在空间域和频域分布特征的方法;（4）综合利用矢量气动声学方法和等效源方法,显示声源和散射边界周围声强矢量场的分布特征和能量传播途径,直接揭示了阻抗边界主要的吸声位置以及直接计算得到阻抗边界的吸收声功率.      

锂离子电池放电循环的发热特性研究

锂离子电池发热特性的研究对于发展电池热管理系统具有重要意义.本文采用数值方法对锂电池放电过程中的微观发热特性进行了研究,并对锂电池放电循环过程中固体电解质(SEI)膜和欧姆热的变化规律进行了分析,研究结果表明:锂电池以高倍率(5C)放电时,SEI膜产生的热量是锂电池发热的重要部分;随着放电循环的进行,锂电池负极颗粒表面SEI膜以线性规律增厚,导致电池SEI膜电阻不断增大;锂电池放电环境温度越高,锂电池负极SEI膜增厚越快,容量衰退越快。     

Analysis of the Properties of Fractional Heat Conduction in Porous Electrodes of Lithium-Ion Batteries

Research on the heat transfer characteristics of lithium-ion batteries is of great significance to the thermal management system of electric vehicles. The electrodes of lithium-ion batteries are composed of porous materials, and thus the heat conduction of the battery is not a standard form of diffusion. The traditional heat conduction model is not suitable for lithium-ion batteries. In this paper, a fractional heat conduction model is used to study the heat transfer properties of lithium-ion batteries. Firstly, the heat conduction model of the battery is established based on the fractional calculus theory. Then, the temperature characteristic test was carried out to collect the temperature of the battery in various operating environments. Finally, the temperature calculated by the fractional heat conduction model was compared with the measured temperature. The results show that the accuracy of fractional heat conduction model is higher than that of traditional heat conduction model. The fractional heat conduction model can well simulate the transient temperature field of the battery. The fractional heat conduction model can be used to monitor the temperature of the battery, so as to ensure the safety and stability of the battery performance.     

孔隙介质包裹的充液管道结构中导波传播特性

研究孔隙介质包裹的充液管道中纵向导波传播特性,分析孔隙介质参数对频散曲线的影响。建立了孔隙介质包裹充液管道的结构模型,利用孔隙介质弹性波动理论,建立对应的频散方程,数值模拟计算得到该模型的频散曲线和时域波形,并分析了孔隙介质参数以及管壁厚度对频散曲线的影响。结果表明孔隙介质的渗透率对于导波频散的影响较小,孔隙度的改变对时域波形的位移幅度影响较大。同时,导波存在衰减,且衰减随孔隙度增大而增大。所得结论为埋地管道无损检测方面提供一定理论参考。     

基于等效模型和多时间尺度扩展卡尔曼滤波的锂离子电池SOC预测

荷电状态(SOC)和最大可用电量估计是锂离子电池寿命预测中的两个最重要部分;然而与快速时变的SOC比较,最大可用电量的参数变化缓慢;文章提出了一个基于等效模型和多时间尺度的扩展卡尔曼滤波(EKF)预测算法对SOC和最大可用容量分别在不同时间尺度上进行估计,在宏观尺度上利用了SOC估计值作为观测量,更新最大可用电量;针对NCA/C卫星锂离子电池实验数据的仿真结果表明,提出的多时间尺度EKF预测算法与EKF联合估计算法相比,SOC和最大可用电量估计准确度更高,同时提高了计算效率。     

Interface wave propagation characteristics of liquid-immersed porous cylinder

This paper devotes to investigate the propagation characteristics of the interface wave on the liquid-immersed porous cylinder, and special emphasis is paid on the dependence of the dispersion relation on the porous media parameters. A model of liquid-immersed porous cylinder is established theoretically. Based on the elastic-dynamic theory of liquid-saturated porous solid and wave theory, the dispersion curves and transient response of open-pores and sealed-pores are simulated numerically, and their dependence on the cylinder radius and porous medium parameters are analyzed. The results show that the Stoneley-Scholte wave can be clearly distinguished with other waves in the time domain, and the Stoneley-Scholte wave dispersion relates intimately with the porosity of the porous medium and cylinder radius, whilst the permeability of the media has little effect on the dispersion property.     

含孔隙分层半空间中瑞利波的传播特性研究

为了研究含孔隙介质分层半空间中瑞利波的传播规律,分析孔隙介质参数对瑞利波频散曲线的影响,本文进行了数值模拟研究。采用传递矩阵算法,计算了含孔隙分层半空间中一定频率范围内瑞利波所有模式的频散及激发强度曲线,并与均匀弹性固体分层半空间情况作了类比分析,在含孔隙覆盖层的两层模型和含低速孔隙夹层的三层模型下,详细研究了孔隙度、渗透率、层厚度等参数对瑞利波各模式的影响,发现孔隙度及层厚度的变化对频散曲线影响较大,而渗透率的变化对频散曲线影响较小。     

Frequency band structure and absorption predictions for multi-periodic acoustic composites

This article introduces a computational framework for studying frequency band structure and absorption behavior in multi-periodic acoustic composite structures. Herein, multi-periodic acoustic composite structures are defined as periodically-layered acoustic media wherein each layer is composed of periodically-repeated fluid unit cells, especially those arising from the study of porous materials. Hence, at least two periodic scales (microscopic and mesoscopic, respectively) comprise the macroscopic acoustic composite media. Exploitation of the multi-periodicity allows for efficient generation of dispersion and absorption curves via the conventional multi-scale asymptotic method (for homogenizing the mesoscale) coupled to the acoustic transfer matrix methods (for the macroscale). The combined computational framework results in a single analysis procedure for evaluating complex dispersion relationships and acoustic absorption. The dispersion curves can be used to reveal frequency stop bands wherein the wave vector is highly imaginary—i.e., plane waves experience rapid attenuation. They can also be used to reinterpret classical absorption curves. The framework is applied to four multi-periodic acoustic composite structures in order to demonstrate the framework's utility and to reveal novel properties, particularly those which can be influenced by design of the mesoscopic unit cell.     

Hybridization of acoustic waves in piezoelectric plates

The interaction (hybridization) of different types of acoustic waves of zero and higher orders propagating in lithium niobate piezoelectric plates is theoretically investigated. Different crystallographic orientations of the plates and different directions of wave propagation in them are considered. It is shown that, for an electrically free plate with the propagation direction along any of the crystallographic axes, the dispersion curves have intersection points and hybridization is absent. However, when the propagation direction slightly changes or when one of the plate surfaces is short-circuited, the dispersion curves separate and the waves become coupled. A quantitative coefficient characterizing the degree of wave hybridization with allowance for both mechanical and electric coupling is introduced. It is shown that the dependence of this coefficient on the product of the plate thickness by the wave frequency determines the extent of separation of the dispersion curves of interacting waves. The phenomenon under study is of both fundamental and practical interest, for example, in connection with the problem of an efficient excitation of nonpiezoactive acoustic waves in piezoelectric plates.     

A review of recent developments in the surface modification of LiMn2O4 as cathode material of power lithium-ion battery

LiMn₂O₄ (LMO) is a very attractive choice as cathode material for power lithium-ion batteries due to its economical and environmental advantages. However, LiMn₂O₄ in the 4-V region suffers from a poor cycling behavior. Recent research results confirm that modification by coating is an important method to achieve improved electrochemical performance of LMO, and the latest progress was reviewed in the paper. The surface treatment of LMO by coating oxides and nonoxide systems could decrease the surface area to retard the side reactions between the electrode and electrolyte and to further diminish the Mn dissolution during cycling test. At present, LiMn₂O₄ is the mainstreaming cathode material of power lithium-ion battery, and, especially the modified LMO, is the trend of development of power lithium-ion battery cathode material in the long term.