巴克豪森励磁检测传感器设计与仿真分析

针对铁磁性材料设计了一种基于巴克豪森效应的励磁检测传感器装置.为了验证所设计的励磁检测传感器中励磁装置的可行性,利用有限元电磁场仿真分析软件Ansoft对磁化器部分进行了有限元仿真,并分析了不同激励条件下的试样磁化效果.通过仿真结果可以得出:磁化装置符合设计要求,能够对试件进行有效的励磁;通过不同参数下的仿真结果得到,励磁电流幅值以及频率是影响励磁效果的关键因素,并且对于特定分析点,随着励磁电流的幅值减小以及频率的增加,试件磁感应强度基本呈现减小的变化趋势.     

励磁器磁极布置及提离值的确定

介绍钢丝绳故障电磁监测方法所涉及的永久磁铁励磁装置的设计方法.为了研究磁极布置方式对钢丝绳通过时产生的励磁效果,用ansoft maxwell软件进行仿真,确定了N-N-S-S磁极布置方式具有最好的磁化效果,该方式下钢丝绳的磁感应强度B接近2 T,满足将钢丝绳磁化至饱和状态B≥1 T的要求.利用磁偶极子理论和有限元分析,采用MATLAB软件仿真不同提离值下的漏磁场强度,利用Ansoft maxwell软件进一步验证,结合实际工况,确定了传感器在钢丝绳径向安装、提离值的范围2～3 mm时监测效果较好.在实验室搭建电梯钢丝绳检测实验台,对所做的仿真研究进行实验验证,该N-N-S-S励磁器磁极布置方式及2.5 mm的提离值有较好的应用效果.     

基于ANSYS的霍普金森拉杆装置设计研究

分离式霍普金森拉杆(Split Hopkinson Tension Bar,SHTB)装置被广泛用于研究材料的动态抗拉力学性能,对SHTB来说,入射拉伸波的峰值大小、脉冲时长及脉冲升时等直接关系拉伸实验结果的准确性.目前尚无系统性地对入射拉伸波的产生尤其是实验装置中各部件的尺寸对入射波波形影响的研究.采用ANSYS/LS-DYNA有限元分析软件对SHTB实验装置中入射波产生过程的波形叠加、幅值等问题进行数值分析,为改进SHTB实验装置提供了设计依据.     

磁弹传感器动态磁滞模型构建与影响因子分析

研究钢缆索索力测试问题,从钢缆索磁化过程中能量平衡原理出发,在考虑与励磁频率相关的涡流损耗和异常损耗等能量损耗的基础上建立硬磁材料应力相关的动态磁滞模型,对模型的应力、温度和励磁磁场等影响因子进行了理论分析.针对常用Preisach和Jiles-Atherton磁滞模型对硬磁钢缆索材料动态模型描述的不足,提出重点分析了磁场频率和磁化工作点对模型的影响,并进行了仿真.通过仿真结果的对比分析,传感器在准静态频率时能量损耗主要来自磁滞损耗,在中高频率时涡流损耗和异常损耗项非常明显.当磁化工作点充分接近材料饱和磁化点时,传感器灵敏度下降;远离饱和磁化点时,模型精度降低,测量精度下降.     

交变漏磁法在钢管表面缺陷识别中的应用

交变漏磁通法由于采用交流信号通过励磁线圈对钢管进行磁化,励磁强度和渗透深度容易实现调节[1],所以较永磁铁的漏磁检测方法更容易实现表面缺陷的检测.本文对缺陷处泄漏场的分布进行了分析,并用实验验证了分析的正确性.结果表明,该交变漏磁法对钢管表面较小裂纹具有较高的检出率.     

挖掘机工作装置的静强度仿真分析

针对反铲液压挖掘机工作装置在强度设计时,边界条件设定困难,且计算工况选择过于简单的问题,为了准确地找到工作装置的危险截面,采用Workbench软件建立了工作装置的有限元模型,对不同位移边界条件进行了理论分析和仿真对比,并通过应力试验进行验证,最后针对多种工况对工作装置进行有限元分析.结果表明简支梁位移边界条件更符合实际情况,且复合工况下斗杆的受力更大.仿真结果与实验数据比较吻合,找到了工作装置较精确的危险截面,可以为同类工程机械的强度分析提供一定的参考.     

基于有限元分析QCM电极尺寸的优化设计

提出了一种优化石英晶体微天平(Quartz Crystal Microbalance,简称QCM)结构、抑制寄生振动模的设计方法.用Ansys9.0有限元软件直接对QCM进行三维有限元分析,从而避免了一般解析和半解析中对控制方程的简化.首先通过对QCM谐振频率收敛性的分析,验证了有限元计算的正确性;然后分析了不同电极尺寸对QCM振动及能陷情况的影响,并找到了较佳的电极尺寸;最后针对不同电极尺寸的QCM进行了液体测量实验,实验结果验证了基于有限元分析QCM电极尺寸设计方法的有效性.     

电工钢片磁化曲线无损检测传感器研究

针对一种电工钢片磁化曲线无损检测传感器进行研究,该传感器利用磁通测量线圈和磁位计分别检测电工钢片特定区域的磁通和磁势,实现钢片磁化曲线的无损检测.为了实现传感器的优化设计,利用ANSYS软件对传感器进行二维和三维仿真实验.同时,通过仿真实验获得不同励磁载荷情况下磁通测 量线圈和磁位计的仿真测量值;对检测到的信号进行曲线拟合,求得被测电工钢片的基本磁化曲线.仿真实验验证了该传感器检测方案的正确性和优化设计的可行性,并为实际应用提供了根据.     

图像重建中 Total Variation 正则化项的有限元计算方法

为在迭代图像重建算法中获得更高质量的重建图像,推导出TV（Total Variation）正则化项关于重建图像的Fréchet导数,并给出该导数的有限元表示;利用两个数值实验,分别采用不同的网格尺寸和不同的形函数验证该有限元表示结果.数值实验结果表明：采用相同的k次单纯形元时,随着网格不断加密,计算结果的L1和L2误差均下降;采用相同的网格时,线性单纯形元函数计算结果明显优于分片常数有限元和二次单纯形元计算结果.     

碳纤维增强复合材料脉冲涡流无损检测仿真与实验研究

采用有限元仿真软件对脉冲涡流矩形传感器两种放置方式进行了建模与仿真分析,综合比较水平与竖直放置两种方式的检测效果,相同尺寸的矩形传感器水平放置检测时,长宽比越大,检测效果越好。采用水平放置方式下的矩形探头对碳纤维增强复合材料进行了电导率分布与缺陷检测实验,实验证实脉冲涡流矩形传感器能够有效检测碳纤维增强复合材料的电导率分布与缺陷。     

A note on persistency of excitation

We prove that if a component of the response signal of a controllable linear time-invariant system is persistently exciting of sufficiently high order, then the windows of the signal span the full system behavior. This is then applied to obtain conditions under which the state trajectory of a state representation spans the whole state space. The related question of when the matrix formed from a state sequence has linearly independent rows from the matrix formed from an input sequence and a finite number of its shifts is of central importance in subspace system identification.     

Persistence of excitation in linear systems

This paper develops output reachability characterizations of linear finite dimensional multivariate systems, so as to translate excitation properties of system inputs to excitation properties of system outputs, states, or associated regression vectors. Such properties are of fundamental concern for convergence of algorithms involving on-line identification, adaptive state estimation, prediction and control. Persistence of excitation guarantees convergence without a priori stability assumptions and ensures robustness properties.     

Persistency of excitation in continuous-time systems

For the class of linear time-invariant single-input continuous systems we find conditions on the input under which the state is persistently exciting for adaptive identification purposes. These conditions are expressed through time-domain properties of the filtered input. They are both necessary and sufficient and no prior constraints are placed on the structure of the input wave or its boundedness.     

Electron impact excitation cross sections

Title of program: POLORB Catalogue number: AAGW Program obtainable from: CPC Program Library, Queen's University of Belfast, N. Ireland (see application form in this issue)

     

16.

Persistent excitation in bilinear systems     

Dasgupta  S. Shrivastava  Y. Krenzer  G. 《Automatic Control, IEEE Transactions on》1991,36(3):305-313

Discrete-time systems described by difference equations which are polynomial in the input and linear in the output are discussed. Bilinear systems are special members of this class. Two issues are examined. First, a multidimensional polynomial-based algebraic condition which is necessary and sufficient for such systems to be identifiable is given. Second, subject to an identifiability assumption, a condition on the input sequence which guarantees persistent excitation is given. The principle analytic tool used in this study involves multidimensional polynomials     

17.

同步发电机励磁控制器设计     

《工矿自动化》2013,(10):55-59

针对基于开环迭代学习控制的同步发电机励磁控制器存在稳定性差、易受干扰影响、不能完全跟踪期望轨迹的问题,设计了一种基于开闭环PID迭代学习控制与电力系统稳定器结合的同步发电机励磁控制器;在开环迭代学习控制的基础上,引入闭环反馈控制,将上一次的输入和输出误差及当前的输出误差作为当前的控制输入,从而构成开闭环PID型迭代学习控制;同时,利用电力系统稳定器提供的附加正阻尼信号来改善同步发电机励磁控制系统的电压稳定性和功角稳定性。仿真结果表明,该励磁控制器具有较强的鲁棒性,提高了系统稳定性。     

18.

A numerical method for determining a localized initial excitation for some mathematical models of the heart excitation     

A. M. Denisov  I. A. Pavel’chak 《Mathematical Models and Computer Simulations》2013,5(1):75-80

A numerical method for determining a localized initial excitation for some mathematical models of heart excitation is considered. In the statement of the direct problem, the process of changing the field in two domains corresponding to the heart and the torso is simulated. The alteration of the potential in the heart is described by the FitzHugh-Nagumo or the Aliev-Panfilov model for domains in R2. The inverse problem consists in determining the coordinates of a localized initial excitation in the heart from the known values of the potential on the boundary of the torso. The results of numerical experiments are presented.     

19.

Prosody modification using instants of significant excitation     

Rao  K.S. Yegnanarayana  B. 《IEEE transactions on audio, speech, and language processing》2006,14(3):972-980

Prosody modification involves changing the pitch and duration of speech without affecting the message and naturalness. This paper proposes a method for prosody (pitch and duration) modification using the instants of significant excitation of the vocal tract system during the production of speech. The instants of significant excitation correspond to the instants of glottal closure (epochs) in the case of voiced speech, and to some random excitations like onset of burst in the case of nonvoiced speech. Instants of significant excitation are computed from the linear prediction (LP) residual of speech signals by using the property of average group-delay of minimum phase signals. The modification of pitch and duration is achieved by manipulating the LP residual with the help of the knowledge of the instants of significant excitation. The modified residual is used to excite the time-varying filter, whose parameters are derived from the original speech signal. Perceptual quality of the synthesized speech is good and is without any significant distortion. The proposed method is evaluated using waveforms, spectrograms, and listening tests. The performance of the method is compared with linear prediction pitch synchronous overlap and add (LP-PSOLA) method, which is another method for prosody manipulation based on the modification of the LP residual. The original and the synthesized speech signals obtained by the proposed method and by the LP-PSOLA method are available for listening at http://speech.cs.iitm.ernet.in/Main/result/prosody.html.     

20.

同步发电机励磁非线性预测控制技术   总被引：1，自引：0，他引：1  

蒋铁铮  陈陈  曹国云 《控制与决策》2005,20(4):467-470

以功角、有功功率、角速度这些可测量作为反馈量,基于非线性预测控制理论,设计出具有闭合解析形式控制律的励磁控制器．该控制器的设计参数只有滚动预测时间T和控制阶r,便于工程实现和调试．仿真结果表明,该控制器能使系统提高稳定性,具有良好的动态品质,较好地维持了发电机机端电压的静态调节精度．     

Computer:	Installation:
CDC 7600	NCAR, Boulder, Colorado
CDC 6600	ULCC, University of London
ICL 1904S	Queen Mary College, London Operating system: SCOPE, MAXIMOP Programming language used: FORTRAN IV High speed storage required: 31 kwords No. of bits in a word: 60 Overlay structure: None No. of magnetic tapes required: None Other peripherals used: Card reader, line printer No. of cards in combined program and test deck: 1722 Card punching code: CDC

Persistent excitation in bilinear systems

Discrete-time systems described by difference equations which are polynomial in the input and linear in the output are discussed. Bilinear systems are special members of this class. Two issues are examined. First, a multidimensional polynomial-based algebraic condition which is necessary and sufficient for such systems to be identifiable is given. Second, subject to an identifiability assumption, a condition on the input sequence which guarantees persistent excitation is given. The principle analytic tool used in this study involves multidimensional polynomials     

同步发电机励磁控制器设计

针对基于开环迭代学习控制的同步发电机励磁控制器存在稳定性差、易受干扰影响、不能完全跟踪期望轨迹的问题,设计了一种基于开闭环PID迭代学习控制与电力系统稳定器结合的同步发电机励磁控制器;在开环迭代学习控制的基础上,引入闭环反馈控制,将上一次的输入和输出误差及当前的输出误差作为当前的控制输入,从而构成开闭环PID型迭代学习控制;同时,利用电力系统稳定器提供的附加正阻尼信号来改善同步发电机励磁控制系统的电压稳定性和功角稳定性。仿真结果表明,该励磁控制器具有较强的鲁棒性,提高了系统稳定性。     

A numerical method for determining a localized initial excitation for some mathematical models of the heart excitation

A numerical method for determining a localized initial excitation for some mathematical models of heart excitation is considered. In the statement of the direct problem, the process of changing the field in two domains corresponding to the heart and the torso is simulated. The alteration of the potential in the heart is described by the FitzHugh-Nagumo or the Aliev-Panfilov model for domains in R2. The inverse problem consists in determining the coordinates of a localized initial excitation in the heart from the known values of the potential on the boundary of the torso. The results of numerical experiments are presented.     

Prosody modification using instants of significant excitation

Prosody modification involves changing the pitch and duration of speech without affecting the message and naturalness. This paper proposes a method for prosody (pitch and duration) modification using the instants of significant excitation of the vocal tract system during the production of speech. The instants of significant excitation correspond to the instants of glottal closure (epochs) in the case of voiced speech, and to some random excitations like onset of burst in the case of nonvoiced speech. Instants of significant excitation are computed from the linear prediction (LP) residual of speech signals by using the property of average group-delay of minimum phase signals. The modification of pitch and duration is achieved by manipulating the LP residual with the help of the knowledge of the instants of significant excitation. The modified residual is used to excite the time-varying filter, whose parameters are derived from the original speech signal. Perceptual quality of the synthesized speech is good and is without any significant distortion. The proposed method is evaluated using waveforms, spectrograms, and listening tests. The performance of the method is compared with linear prediction pitch synchronous overlap and add (LP-PSOLA) method, which is another method for prosody manipulation based on the modification of the LP residual. The original and the synthesized speech signals obtained by the proposed method and by the LP-PSOLA method are available for listening at http://speech.cs.iitm.ernet.in/Main/result/prosody.html.     

同步发电机励磁非线性预测控制技术

以功角、有功功率、角速度这些可测量作为反馈量,基于非线性预测控制理论,设计出具有闭合解析形式控制律的励磁控制器．该控制器的设计参数只有滚动预测时间T和控制阶r,便于工程实现和调试．仿真结果表明,该控制器能使系统提高稳定性,具有良好的动态品质,较好地维持了发电机机端电压的静态调节精度．