Active Vibration Control of Beam Using Electro-magnetic Constrained Layer Damping

This paper investigates vibration control of beam through electro-magnetic constrained layer damping （EMCLD） which consists of electromagnet layer, permanent magnet layer and viscoelastic damping layer. When the coil of the electromagnet is electrified with proper control strategy, the electromagnet can exert magnetic force opposite to the direction of structural deformation so that the structural vibration is attenuated. A mathematical model is developed based on the equivalent current method to calculate the electromagnetic control force produced by EMCLD. The governing equations of the system are obtained using Hamilton＇s Principle and then reduced with the assumed-mode method. A simulation on vibration control of a cantilever beam is conducted under the velocity proportional feedback to demonstrate the energy dissipation capability of EMCLD, and the beam system with the same parameter is experimented. The results of experiment and simulation are compared and the results show that the EMCLD is an effective means for suppressing modal vibration. The results also indicate that the beam system has better control performance for larger control current. The EMCLD method presented in this paper provides an applicable and efficient tool for the vibration control of structures.

On vibration analysis of functionally graded carbon nanotube reinforced magneto-electro-elastic plates with different electro-magnetic conditions using higher order finite element methods

This article deals with evaluating the frequency response of functionally graded carbon nanotube reinforced magneto-electro-elastic(FG-CNTMEE)plates subjected to open and closed electro-magnetic circuit conditions.In this regard finite element formulation has been derived.The plate kinematics adjudged via higher order shear deformation theory(HSDT)is considered for evaluation.The equations of motion are obtained with the help of Hamilton’s principle and solved using condensation technique.It is found that the convergence and accuracy of the present FE formulation is very good to address the vibration problem of FG-CNTMEE plate.For the first time,frequency response analysis of FG-CNTMEE plates considering the effect of various circuit conditions associated with parameters such as CNT distributions,volume fraction,skew angle,aspect ratio,length-to-thickness ratio and coupling fields has been carried out.The results of this article can serve as benchmark for future development and analysis of smart structures.

Effects of Exposure to Extremely Low Frequency Electro-magnetic Fields on Circadian Rhythms and Distribution of Some Leukocyte Differentiation Antigens in Dairy Cows

Objective To investigate the effects of extremely low frequency magnetic and electric fields （ELFEMFs） emitted from 380 kV transmission lines on some leukocyte differentiation antigens in dairy cows. Methods The study was carded out in 5 cows exposed to 1.98-3.28 μT of ELFEMFs and in 5 control cows exposed to 0.2-0.7 μT of ELFEMFs. Following haematological and immunologic parameters were measured in both groups： WBC, CD45R, CD6, CD4, CD8, CD21, and CD11B leukocyte antigen expression. Results Some of the haematological and immunologic parameters under investigation were similar in both groups. However, CD8 （T lymphocyte surface antigen） was higher in the exposed group （1.35 ±0.120 vs 0.50 ±0.14×10^3/mL）. Furthermore, the CD4/CD8 ratio （0.84 ±0.05 and 2.19±0.16 for exposed and not exposed cows respectively） and circadian rhythm were different between the two groups. Conclusion Exposure to ELFEMFs is responsible of the abnormal temporal variations and distribution of some haematological and immunological parameters in dairy cows.

Eddy Currents and Electro-magnetic Forces on the Lower Hybrid Ware Launching Antenna on the Superconducting Tokamak HT-7

This paper analyzes the eddy currents and the electro-magnetic forces on the lower hybrid wave (LHW) launching antenna on the superconducting Tohamak HT-7 by using a finite element circult method. A new iterative algorithm is developed to analyze the coupled magnetic fields Which are very difficult to be calculated. The method and results obtained are helpful to study the eddy currents and electro-magnetic forces on metal plates which are placed in a rather complicated electro-magnetic environment.

Research on Electro-Magnetic Environment of UHV Transmission Lines

Employing even higher voltage level to promote power transmission economy is an important subject in the program of power transmission from west to east. The influence of electro-magnetic environment of transmission project being closely related with human health and construction cost has to be seriously considered before advancing transmission voltage. This paper analyzes and discusses overseas and domestic research achievements on radio interference, audible noise, power frequency electric field, power frequency magnetic fields, DC resultant field intensity and ion stream involved in power transmission at ultra-high-voltage (UHV)AC and ± 800 kV DC or even higher voltage levels. Suggestions on limiting electro-magnetic effects and their ceiling value as well as measures to improve electro-magnetic environment are put forward.

Numerical Experiment for Dipole-Dipole Interaction in Electro-Magnetism with Help of a Regular Tetrahedron

Aim of this work is to try to explain, on a Rational basis, some equations of Electro-Magnetism, which are based on Experimental data. Any Electric Field can produce a Field of many small Electric Dipoles, continuously distributed in space. In a region, where the Electric Field is constant, in direction and magnitude, all the small Dipoles are parallel to the Electric Field, and are represented by a single, long, parallel to them, fixed in space, Electric Dipole, which is here called Compass. An Alternating current, in a straight Conductor, is studied, by a simple, short computer program, for step-by-step nonlinear dynamic analysis. It is found that, only an Alternating current, not a direct current, can produce an Electric Dipole, in a straight Conductor. The two above Dipoles (Compass-Conductor) are assumed with equal lengths ℓ, lying on two skew lines, perpendicular to each other, at a distance ℓ√2, thus forming, by their four ends, a Regular Tetrahedron, with side length ℓ. Repulsion, between Like Charges, obeys the simple Coulomb Electro-Static law. Whereas Interaction (Attraction or Repulsion), between Unlike Charges, obeys a more accurate Lennard-Jones law. The analysis of Dipole-Dipole (Compass-Conductor) Interaction is performed by hand calculator. The only out-of-balance forces, in the regular Tetrahedron, acting on the Rigid Conductor, are the so-called magnetic forces. Their direction is found, in a simple Rational way, with help of Regular Tetrahedron, without recoursing to a “right-hand-rule”. The proposed model is applied to 1) The force acting on an Electric Charge moving in a magnetic field. 2) The force acting on a Current carrying straight Conductor, due to a magnetic field. 3) The magnetic fields created around a Current carrying straight Conductor. In these applications, proposed model gives reasonable results. Particularly, in third application, results, obtained by proposed model, are found in satisfactory approximation with corresponding ones, obtained by an empirical formula, based on relevant Experimental observations of H.-C. Oersted and A.-M. Ampère. So, the reliability of proposed model is checked. Position and direction of magnetic field vector coincide with those of a corresponding fixed Compass of a constant Electric Field. Main point of present work is that, without introducing the concept of a magnetic field vector, by combining field of dipoles, produced by an electric field, with dipole of an alternating current carrying conductor, the magnetic forces can be determined.

量子传感(Ⅱ):关键技术与典型代表

作为量子信息感知物理实现基础的量子传感技术是三大核心量子技术之一,也是发展历史最悠久、技术成熟度最高、实际应用范围最广、潜在应用最多的量子技术。文章是量子传感综述论文的第二部分,在第一部分的基础上,介绍了量子传感的关键技术以及量子传感器的典型代表。其中,关键技术方面,结合量子态的制备、操控、探测,概括了量子传感具备颠覆性能力的核心原理及技术支撑;典型代表方面,详细介绍了频率、电、磁、重力、惯性等代表性量子传感器技术,以及各类量子传感器的基本原理、实现平台及发展现状。

齿调制作用下转子开槽对永磁电机电磁振动影响

为了研究齿调制作用下转子表面开槽对永磁同步电机电磁振动的影响,以小功率分数槽集中绕组(FSCW)内置永磁同步电机(IPMSM)为研究对象,通过麦克斯韦应力张量法推导径向电磁力波的频率及空间阶数特征。分析齿调制作用在FSCW-IPMSM中将空间高阶电磁力波调制为低阶电磁力波的过程,并给出转子表面开槽在齿调制作用影响下与电磁振动间的联系。研究表明,转子表面开槽结构的改变会使各次谐波磁场发生变化,进而改变以极数阶电磁力波为代表的高阶电磁力波的幅值。在齿调制作用下,这些高阶电磁力波会被调制为幅值较高的低阶电磁力波,并引起不同幅度的低阶振动。然后建立C型、V型两种不同转子表面开槽结构的10极12槽FSCW-IPMSM电磁及结构有限元分析模型并进行仿真分析。结果表明,极数阶即10阶电磁力波会被调制为2阶并引起2阶振动,且两种不同开槽结构间的电磁振动存在着高达22.1%的差异。最后,在一台10极12槽样机上进行振动实验,验证理论与仿真分析结果。

无人机17kW电机振动噪声分析与巡航转速下尖端噪声优化

随着无人机的迅速发展,噪声问题影响消费者体验及AI交互、语音识别等技术,限制了无人机应用潜力。该文针对一台17 kW无人机用外转子永磁同步电机进行研究。为降低电机尖端振动噪声,且保留原电机电磁性能,重点提出优化磁极和定子开槽的方法。具体以平均转矩、转矩脉动等作为约束条件,构建多目标优化数学模型,并利用混合粒子群优化算法求解。该文深入探讨磁极参数、定子开槽对低阶次径向气隙磁通密度空间谐波特征的影响。并对电机转子模态仿真,以研究径向电磁力与空间模态的作用机理。在多转速情况下,以巡航转速为重点,分析整体电机电磁振动噪声特征。最后,仿真和实验结果表明,电机在巡航转速下的尖端噪声显著减小。验证了优化结构对无人机电机尖端振动噪声有明显抑制作用,对解决无人机噪声问题具有重要意义。

一种针对Virtex-7加密位流的侧信道分析方法

随着FPGA在商业、国防等领域的广泛应用,出现了很多针对FPGA的攻击方法,电路安全性面临着极大挑战。为了进一步研究FPGA的安全机制,文章介绍了一种新的侧信道分析(SCA)方法,并首次在Xilinx Virtex-7芯片上分析了加密位流在加载过程中存在的安全漏洞。相比之前的攻击目标,Virtex-7芯片规模更大,采集的信号信噪比更低,攻击难度更大。之前的研究使用的是SASEBO或SAKURA这类专为SCA设计的测试板,而该文的分析是第一个在Xilinx官方评估板上进行的实例,由于官方评估板不是针对侧信道信号采集设计的电路板,因此需要经过处理才能获得足够的信噪比。使用电磁辐射作为侧信道测量值,在80万条电磁曲线内就能够获得一组密钥。通过密钥解密,得到明文位流,攻击者就能够对FPGA进行逆向分析、克隆等操作,从而影响FPGA的安全。

基于矢量控制的电励磁双凸极电机失磁容错运行转矩脉动抑制策略

电励磁双凸极电机(doubly salient electro-magnetic machine,DSEM)在航空和电动汽车等领域具有广阔的应用前景,这些领域对可靠性有更高的要求。DSEM通过励磁绕组实现他励,其励磁故障是影响DSEM电动运行可靠性的重要方面。针对DSEM驱动系统的励磁故障,该文提出一种基于矢量控制的DSEM失磁容错运行转矩脉动抑制策略。首先,根据瞬时功率不变原则建立DSEM失磁后极坐标系下的转矩数学模型,该模型建立磁阻转矩与电流矢量的幅值和相角之间的关系。随后,基于该模型,以铜耗最小化为目标确立电流矢量的相角,通过控制电流矢量的幅值抑制转矩脉动,将所得的电流矢量变换后得到三相参考电流,进行闭环控制。最后,针对1台18/12极DSEM,通过实验验证所提方法的可行性和有效性。

基于Levant微分器的磁浮球控制算法研究

针对永磁电磁混合悬浮系统控制中因信号突变和噪声干扰引起的控制效果不理想等问题,提出一种改进型Levant微分器和PID相结合的控制方法(improve Levant-PID,ILevant-PID)。融合PID控制适应性强和Levant微分器对输入噪声的鲁棒特性优势,解决系统输出抖振问题,利用模拟退火-粒子群优化解决ILevant-PID控制器参数多、关联性强等制约问题。仿真实验表明:与传统PID控制方法相比,ILevant-PID控制方法在阶跃输入下,启动更为平缓,调节时间减小了41.19%,超调量减小了40.36%。ILevant-PID控制器在阶跃输入时有无噪声条件下的稳态误差分别为±0.37 mm及±0.23 mm,相对于PID降低了87%以上。在跟踪方波输入时,ILevant-PID可实现PID无法对8 mm给定信号无超调跟踪,较好地改善PEMS(permanent magnet electro magnetic hybrid suspension)系统控制性能。

线性霍尔磁传感芯片用引线框架设计

线性霍尔磁传感芯片的金属引线框架部件在待检测磁场中具有聚磁效应和涡流效应,会干扰待测磁场,使磁场强度偏离真实值,导致检测准确度变差。对含磁组分金属框架和不同结构尺寸的框架进行仿真分析后,得出无磁组分材质及小尺寸结构设计可改善金属框架对待检测磁场的干扰,并且对小尺寸结构框架的施工方案进行分析。最终制备得到一种线性霍尔磁传感芯片,通过自主搭建的环境对芯片进行测试,得到354.8 kHz的带宽值。

基于FDTD的局部放电射频传感器特性研究

射频(RF)检测局部放电(PD)可以实现非接触式测量,因而具有较好的应用前景。以小环天线为例,对磁场天线作为局部放电射频传感器时其灵敏度的确定方法和影响灵敏度的因素开展了研究。首先,基于时域有限差分(FDTD)法建立了吉赫兹横电磁波(GTEM)小室的仿真模型,通过实验和仿真对比表明了仿真模型的有效性。在此基础上,考虑了天线结构、尺寸等因素对灵敏度的影响,确定了灵敏度随天线直径、垂直导体、线圈匝数的变化规律。本文的研究为进一步考察不同磁场天线传感器的特性,并对传感器特性进行优化,设计实现能够满足具体电力设备局部放电测试需求的新型射频磁场传感器奠定了技术基础。

高速开关阀动态响应特性研究及性能优化

为研究某型高速开关阀的动态响应特性并开展参数优化,描述开关阀的结构组成及工作原理,并建立其数学模型;基于电磁铁的有限元模型,重点研究极靴盆口磁分路的作用,并求解电磁力及磁通量离散空间分布;进而建立开关阀的机-电-液联合仿真模型,研究其静态压力控制特性及关键参量的动态响应过程。以单变量作用规律分析为基础,应用(1+1)-ES算法完成多参数迭代优化。最后,测定高速开关阀的动态响应特性,完成对比验证。实验结果表明:所建立的联合仿真模型较好地刻画了开关阀的动态响应特性,并借助进化策略优化算法实现了性能的有效提升。

基于抖频和斜坡补偿的抗EMI振荡器设计

设计了一种应用于开关电源转换器中的抗电磁干扰(Electro-Magnetic Interference,EMI)振荡器,其主要创新在于在开关电源系统中加入了频率抖动且可产生斜坡补偿的时钟信号。产生斜率可调整的三角波电流信号,并将频率抖动模块集成在振荡器内部。该振荡器提高了开关电源稳定性,而且引入了数字辅助的修调技术,对充电电容进行双向调整,消除了工艺带来的误差。该振荡器基于0.18μm BCD(Bipolar CMOS DMOS)工艺,实现了振荡器频率线性切换,振荡器的正常工作频率为1 MHz,最小工作频率为100 kHz,其抖动范围在基础频率的−1.66%~+4.3%,在2.7~5.5 V电源电压范围以及−40~125℃温度范围内,输出频率变化2.45 kHz,变化率为0.245%,占空比偏移0.653 ns,补偿电流峰值偏移0.125 nA,修调范围60.98%。

Design and assembly of the CsI(Tl) crystal module of the BESⅢ electro-magnetic calorimeter

The CsI（T1） crystal modules of the Beijing Spectrometer Ⅲ （BESⅢ） electro-magnetic calorimeter （EMC） were designed and assembled through Monte Carlo simulation and experiments. After the assembly was finished, the performance of each crystal module was tested by cosmic rays. All crystal modules were found to work well before the installation of EMC.

无人驾驶履带车辆电子机械制动器的电流预测控制策略

面向制动负荷大的无人驾驶履带车辆,设计了一种基于永磁同步电机的电子机械制动系统,提出了一种针对制动执行全过程的控制策略.在制动空行程段,采用常规的位移、转速、电流三环PID控制,使其快速到达接触位置,快速消除制动器摩擦副间隙;在制动作动力增长段,为保证作动力跟随的精确性、快速性和稳定性,基于接触位置和压紧位置对应的作动力标定结果,内环采用永磁同步电机q轴电流的预测控制策略,保证电子机械制动作动器比例施加行车制动作动力.通过对电子机械制动作动器及作动过程的建模,分析了永磁同步电机q轴电流与制动作动全过程的对应关系,仿真验证了制动作动全过程控制策略中位移控制和扭矩控制动态切换的可行性,提高作动力控制精度和鲁棒性.结果表明该策略既能有效提高制动响应时间,保证制动作动系统能够在50 ms内实现制动间隙快速消除,又能解决电子机械制动作动器作动力控制的不均匀性问题,保证制动作动系统在受到扰动时仍具有较好的跟踪性能,预测误差不超过10%.

城市轨道交通车辆变流设备对计轴设备干扰问题探讨

针对某城市轨道交通B2型车辆计轴红光带干扰问题,采用Maxwell仿真试验以及现场试验结合的方式,以牵引逆变器及辅助逆变器两个大型变流设备为切入点,探究了不同出线布置方式、工作模块数量、负载、DC/DC开关频率对轨道计轴设备的干扰。研究表明大电流线布置方式、高频辅助逆变器DC/DC开关频率变化会对计轴设备产生影响。并基于干扰原因提出应对策略,为既有线路红光带干扰问题提出改善建议,并对未来轨道车辆变流设备设计提供思路。

某梯级电站巨型水轮发电机总体设计研究

某梯级电站所处河流段水力资源丰富、落差巨大,地质结构复杂,土建成本高。该梯级电站天然属性决定了电站装机必然是高转速、大容量水轮发电机型。水轮发电机总体设计方案和单机容量、转速、电压相关,也受制于机组飞逸转速、水轮机轴向推力、径向不平衡力。总结某梯级电站水轮发电机电磁、通风、绝缘、轴承、刚强度、机组轴系稳定等各方面研究成果,并针对某梯级电站具体特点,对各电站水轮发电机总体设计方案进行论证,找出影响设计方案可行的关键因素,为电站总体规划设计提供支持。