亥姆霍兹线圈场均匀性的仿真研究

通过对亥姆霍兹线圈内部的均匀场进行仿真计算,直观地看到了线圈内部场的变化趋势,将结果与解析法结果对比,误差在1％左右,亥姆霍兹线圈在其轴线附近产生的磁场均匀度较好。并以r为200mm、250mm、300mm为例,仿真计算出均匀区的大小,结果表明,线圈馈人点的位置会影响均匀场对称中心的位置。     

仿真地磁的磁场模拟装置

基于亥姆霍兹线圈产生均匀磁场的特性, 绕制了三轴亥姆霍兹线圈, 通过改变3组线圈通电电流大小, 分别产生3个正交方向的磁场, 模拟地磁场强度, 为地磁导航系统的半实物仿真实验提供地磁场环境。同时,就地磁导航半实物仿真的需求, 对地磁场模拟生成装置进行了可重复性和线性度验证实验、响应速度测量实验、均匀性验证实验和稳定性验证实验, 并建立了装置的输入输出模型, 验证了装置的各项指标符合实验室需求。     

基于有限元法对亥姆霍兹线圈磁场的分析

为进一步明确亥姆霍兹线圈所产生磁场的近场特性,尝试采用基于有限元方法的ANSYS软件对亥姆霍兹线圈进行分析.采用ANSYS软件对亥姆霍兹线圈建立三维实体有限元模型并进行仿真.仿真结果与Matlab语言绘制亥姆霍兹线圈磁感应强度的空间分布图相比较,结果说明ANSYS有限元模型优于Matlab语言.最后通过实验验证所建的三维亥姆霍兹线圈有限元模型的有效性和正确性,对研究亥姆霍兹线圈其他性质有一定的参考应用价值.     

永磁体双磁环结构的磁场均匀性分析

提出了可用于四频差动激光陀螺法拉第室的永磁体双磁环结构,用以产生较强且均匀的轴向磁场.推导了永磁体磁环轴线上磁场分布的解析式,理论并实验证明了该解析式的正确性.引入磁场均匀度概念,提出了类亥姆霍兹线圈的舣磁环结构,模拟了磁环间距对磁场分布的影响,数值计算了不同均匀度下双磁环结构的磁场分布特征.在此基础上,针对四频差动激光陀螺法拉第室的要求,给出了适用的设计方案.     

亥姆霍兹磁场分布演示仪的设计与实现

亥姆霍兹线圈是一对匝数和半径相同的共轴平行放置的圆线圈,两线圈间的距离等于线圈半径。亥姆霍兹磁场分布演示仪是利用单片机技术将霍尔探头检测到的磁场信号显示到点阵屏上,移动探头就可以将磁场分布情况以曲线的形式显示出来。该仪器主要服务于实验教学,生动立体的演示给教学带来了很好的效果。     

基于COMSOL软件仿真亥姆霍兹线圈

本文通过应用COMSOL有限元软件对亥姆霍兹线圈产生的涡流进行仿真分析,应用软件自带的后处理功能,图像化的分析亥姆霍兹线圈产生的电磁场响应特性。     

扫频荧光法测量超高真空原子磁光阱中的磁场分布

利用扫频荧光法实测了超高真空原子吸收池中反亥姆霍兹线圈轴线上的磁场分布 ,与计算结果对比 ,同时还采用移动暗线的测量方法进行了检验。考虑到封接材料的非线性磁化 ,可以解释所有观察到的现象。     

均匀磁场与双频激光器的差频特性

磁场均匀性影响双频激光器的差频特性及输出光束的圆偏振度。采用简化物理模型,设计出最佳参数的同轴腰鼓形磁钢,获得了不均匀性小于1.3%的轴向磁场,此设计也可用于行波管等的聚焦场中。新颖的轴对称线圈磁场设计获得了不均匀性小于0.5%的可调场,其单位场强的激磁安匝数、场均匀性、平衡温升等指标均优于长螺线管或亥姆霍兹线圈。实验测量     

利用MATLAB模拟亥姆霍兹线圈磁场分布

文章主要讨论亥姆霍兹线圈中磁场的分布情况,通过MATLAB模拟得到磁场分布的理论图形,并与实际测得值比较进行误差分析,通过实验数据的计算比较,证明磁场满足迭加原理,通过MATLAB的编程过程进一步加深对毕奥-萨伐尔定律的理解.通过该实验的操作、数据处理、计算机模拟、画图对比等过程更好地理解电和磁的相互作用问题.     

光纤陀螺在直流及交变磁场中的磁敏感性研究

介绍了光纤陀螺的磁敏感性机理并进行了实验研究。利用亥姆霍兹线圈装置和光纤陀螺测试平台,研究了光纤陀螺在直流磁场中的磁敏感性,得到光纤陀螺数据输出与磁感应强度基本呈线性关系,以及轴向磁场和径向磁场影响系数的大小和光纤陀螺磁敏感轴的方向。主要针对50Hz的交流磁场研究交流磁场对光纤陀螺零偏和零漂的影响及其交流磁敏感性,得到交流磁场对零偏的影响可以忽略,但磁感应强度与陀螺零漂值的大小基本呈线性关系。研究了不同频率交流磁场对光纤陀螺输出的影响,说明了光纤陀螺数据输出主要与瞬态的磁感应强度成正比,不同频率交流磁场对光纤陀螺零漂值的影响不同,存在一个频率(或频率范围)对光纤陀螺零漂的影响较大,其频率范围与光纤陀螺输出带宽有关。     

3D Helmholtz coil system setup for thermal conductivity measurements of magnetic nanofluids

This study aims to design a mechatronic system that involves a 3D Helmholtz coil system implemented with the 3ω method to measure the thermal conductivity of magnetic nanofluids under uniform and rotating magnetic fields. For this purpose, a 3D Helmholtz coil system was designed and manufactured to generate a uniform and rotating magnetic field up to 400 G. First, the uniformity and rotation abilities of the magnetic field generated by the system were investigated numerically and experimentally. The investigations pointed out that the 3D Helmholtz coil system can generate a uniform magnetic field in 1D, 2D, and 3D with a maximum non-uniformity factor of 0.0016. After that, the thermal conductivity of Fe₃O₄ – water magnetic nanofluid samples with 1, 2, 3, 4, and 4.8 vol.% were measured under 1D, 2D, and 3D uniform magnetic field application. The magnetic field was applied at different direction angles between X, Y, and Z axes in the Cartesian coordinate system. The results pointed out that the thermal conductivity of the samples increases as the magnetic field and particle concentration increase. The maximum thermal conductivity enhancement was observed as ∼9.1% and the minimum thermal conductivity was observed as ∼1.9% when the magnetic field is applied in parallel and perpendicular directions, respectively. The measurement results also pointed out that under the external uniform magnetic field application at 2D and 3D, thermal conductivity enhancement is less affected by the particle concentration increment.     

Uniform magnetic field generated by two orthogonal sheet currentloops

A uniform-magnetic-field generating source (UMFGS) comprising two orthogonal sheet current loops, which gives a uniform magnetic field at low frequency over a much larger region than either a Helmholtz coil or wrapped wires, is presented. The H-field distribution inside the UMFGS is studied under quasi-static conditions. The UMFGS is shown to generate a well-defined magnetic field distribution, and the direction of the generated H field can be adjusted in the range 0-360° in the horizontal plane. Experimental data show good agreement with numerical results. The properties of the UMFGS need to achieve an optimal structure are predicted theoretically. Optimum design equations obtained with the aid of the computer are presented     

兆赫兹频段多频磁负超材料的设计和特性研究

针对传统兆赫兹频段超材料仅工作在单频点,无法适用多频系统的问题,提出一种由介质基板和两侧呈嵌套分布的方形螺旋线圈环构成的超材料结构单元,利用HFSS软件对该回型嵌套式结构及其衍生结构单元进行仿真分析并进行等效参数提取。结果表明:该结构在兆赫兹频段能实现多频点磁负特性,通过调节螺旋线圈的参数可以对磁负点的频率进行调控,以满足不同系统工作频段要求。对低频磁负超材料多频化的发展提供了参考。     

螺线管结构参数对脉冲磁场的影响

研究了线圈间距、匝数、个数以及不锈钢套筒对脉冲磁体产生磁场的影响规律。在储能电容和电压不变的前提下,研究结果表明：增加线圈间距会导致磁感应强度降低,磁力线包络增大,但总电流达到峰值时刻减小;增加线圈匝数,峰值电流明显减小,会降低磁感应强度,但有利于抑制磁力线包络;增加并联线圈个数,有利于产生较长的均匀区,但是在供能一定的条件下,磁场强度有所降低,同时总电流达到峰值时刻减小。总体来看,在一定均匀区长度的设计要求下,减少单个线圈匝数,增加并联线圈个数,能够得到磁感应强度更大、均匀性更好的磁场,但要考虑线圈承载电流的能力。另外,不对称的阴阳极金属结构会导致磁场不对称分布,且磁感应强度达到峰值时刻要晚于总电流达到峰值的时刻。     

Calibration of a multi-mobile coil magnetic manipulation system utilizing a control-oriented magnetic model

In this paper, we address the calibration of a family of magnetic manipulation systems composed of several coils that are moved around by serial robot manipulators. We show in this paper that the calibration of the whole system ultimately results in calibrating the manipulator and coil separately up to an unknown rigid transformation. For calibration of the coil, we propose to use a model that has not been used so far in the literature; a control-oriented model which is sufficiently accurate and computes the magnetic field in real time. A protocol for calibrating the magnetic manipulation system using the Nelder–Mead algorithm to estimate the model parameters is presented. Calibration was performed through simulations and validated experimentally on a physical system. It was observed that the root mean square error was reduced by 37% after calibration of the physical system, indicating an improvement in accurately estimating the magnetic model.     

生物组织磁聚焦电导率成像原理及反演算法

生物组织磁聚焦电导率成像系统利用多圈螺旋电感线圈形成聚焦磁场激励和检测导电目标,达到了提高成像空间分辨率的目的。根据所推导的频率变化与分层生物组织电导率的关系，引入遗传算法对目标电导率进行反演优化计算，获得了充足的成像数据。对于给定的十层分层生物组织模型，反演优化所得电导率除最深层有较大偏差需要进行数据处理外，其余均与目标一致，成像数据非常可靠；成像速度为百毫秒数量级但是具有很大提高潜力。计算结果表明该方法能够有效地对生物组织进行分层媒质建模计算，进一步采取措施能够实现较高分辨率的实时成像。     

A 3-D differential coil design for localized magnetic stimulation

A novel three-dimensional (3-D) differential coil has been designed for improving the localization of magnetic stimulation. This new coil design consists of a butterfly coil with two additional wing units and an extra bottom unit, both perpendicular to the plane of the butterfly coil. The wing units produce opposite fields to restrict the spread of induced fields while the bottom unit enhances the induced fields at the excitation site. The peak induced field generated by this new design is located at the center of the coil, providing an easy identification of the excitation site. The field localization of the new coil is comparable with that of much smaller coils but with an inductance compatible to current magnetic stimulators. Numerical computations based on the principles of electromagnetic induction and using a human nerve model were performed to analyze the induced fields and the stimulation thresholds of new coil designs. The localization of the coil design was assessed by a half power region (HPR), within which the magnitude of the normalized induced field is greater than 1/square root of 2. The HPR for a 3-D differential coil built is improved (decreased) by a factor of three compared with a standard butterfly coil. Induced fields by this new coil were measured and in agreement with theoretical calculations.     

磁性液体强化扬声器音圈散热的实验研究

实验将封有聚α-烯烃合成油基磁性液体的两玻璃管放置于磁场中,研制了磁性液体在均匀磁场中瞬态双热线导热 系数的实验测量装置,测试发现磁性液体的导热系数在均匀磁场中随磁场强度的增大而显著增大.研制了恒压法在线实时 检测扬声器音圈温升的测量装置,评价了在同一工况下空气和磁性液体对扬声器音圈温升的影响,测量发现磁性液体能显著 ...     

行波磁场摆动器产生自由电子激光的初步研究

在一定放置的线圈中通以正弦交流电时,其附近空间就会产生一个正弦行波磁场,磁场的极距和行波的速度都可以通过输入的频率加以调节。相对论性电子在这种摆动器中的散射波长比较短,而能量因子值可以变,这既有利于向短波长方向发展,又有助于自由电子激光器的小型化。