线性测微电感的精化

为提高测微电感传感器的测量精度,提出了基于赫姆霍兹线圈理论设计螺线管线圈的方法,改善了螺线管线圈内轴向上磁场的分布均匀性。首先,分析了螺线管线圈模型,建立了螺线管线圈参数与轴向磁场强度分布相互关系的广义函数模型。然后,通过线圈与磁芯的尺寸确定了系统轴向磁场强度分布函数模型,结合磁芯移动区间范围设置磁场均匀度最小误差目标函数,通过对目标函数寻优得到各螺线管线圈的各项参数。最后,搭建了测微电感传感器的测试系统,测试了传感器性能。实验结果表明:与传统线圈相比,改进型螺线管线圈在100μm测量范围内的线性度由0.46%提高到0.30%。实验显示通过对不同规格的螺线管线圈进行组合,可使得螺线管内轴向上磁场强度分布均匀,从而提高了测量精度。     

高温磁悬浮轴承定子电磁线圈封装技术研究

高温电磁线圈是高温磁悬浮轴承系统的关键元件,为了延长高温电磁线圈的可靠性及使用寿命,提高磁悬浮轴承系统的性能,需要对高温电磁线圈进行封装。主要介绍了高温磁悬浮轴承系统,设计了高温磁悬浮轴承定子线圈的封装结构以及线圈陶瓷骨架结构,探讨了电磁线圈的封装材料及线圈封装工艺。     

面向超高场核磁共振应用的微型接收线圈制作与实验研究

为实现纳升级微量样品检测,结合商业常规核磁共振3.2毫米探头,本文研究了两种类型的自谐振微型接收线圈。当无线传输能量时,探头螺旋管形成射频脉冲激励能量。而微型接收线圈对该能量进行接收后以样品为作用目标,并采集信号回传,把感应获取的磁共振信号传输到探头螺线管。与现有磁共振探头不同,本文提出Pigtail型和Stripline型微接收线圈结构。实测结果显示,线圈谐振频率达128MHz和935.7MHz,应用于3T超导核磁共振设备初步完成了蔗糖波谱的测试分析实验,表明微型接收线圈对提高谱线分辨率有重要作用。     

Dynamic performance of high speed solenoid valve with parallel coils

The methods of improving the dynamic performance of high speed on/off solenoid valve include increasing the magnetic force of armature and the slew rate of coil current, decreasing the mass and stroke of moving parts. The increase of magnetic force usually leads to the decrease of current slew rate, which could increase the delay time of the dynamic response of solenoid valve. Using a high voltage to drive coil can solve this contradiction, but a high driving voltage can also lead to more cost and a decrease of safety and reliability. In this paper, a new scheme of parallel coils is investigated, in which the single coil of solenoid is replaced by parallel coils with same ampere turns. Based on the mathematic model of high speed solenoid valve, the theoretical formula for the delay time of solenoid valve is deduced. Both the theoretical analysis and the dynamic simulation show that the effect of dividing a single coil into N parallel sub-coils is close to that of driving the single coil with N times of the original driving voltage as far as the delay time of solenoid valve is concerned. A specific test bench is designed to measure the dynamic performance of high speed on/off solenoid valve. The experimental results also prove that both the delay time and switching time of the solenoid valves can be decreased greatly by adopting the parallel coil scheme. This research presents a simple and practical method to improve the dynamic performance of high speed on/off solenoid valve.     

Investigation of the magnetic field response from eddy current inspection of defects

Eddy current testing is one of the most widely used methods in non-destructive testing for the inspection of conductive materials. Numerical modelling of eddy current testing has emerged as an important approach alongside experimental studies. This paper investigates an application of numerical modelling and experimental study as a means of the quantitative non-destructive evaluation (QNDE) of defects in conductive samples. There are two methods of measuring eddy current response, more commonly by measuring the change in impedance of the eddy current probe coil, or as used in this work, by measuring the change in magnetic field directly using magnetic field sensors such as superconducting quantum interference devices, giant magneto resistance, or as in this case Hall sensors. Specifically, measurements made using an eddy current probe containing an excitation coil and a Hall sensor, experimentally obtained using an X?CY scanner table, are compared with a numerical (finite element method) model. The discrepancies between the experimental tests and the numerical models have been analysed and explained, which is an important factor in engineering applications of QNDE.     

永磁同步直线电机霍尔位置检测传感器的优化

针对采用线性霍尔元件检测直线电机动子的磁场进而通过磁场信息来解算电机位置的方法,通过介绍双霍尔传感器位置检测的原理,分析由安装误差造成解算位置偏差的机理。提出采用三轴霍尔传感器代替线性霍尔传感器的方法,实现霍尔线性影响因素的误差补偿。为了降低非线性干扰造成的位置解算误差,提出了模糊-神经建模方法来实现传感器的离线标定,最后通过仿真和实验证明了所提传感器误差补偿方法的有效性。     

外加磁场对磁流体润滑油膜轴承的影响

为了研究磁流体润滑油膜轴承内磁场的分布情况,分别通过永磁铁、螺线管及亥姆赫兹线圈对其施加3种不同形式的外磁场。通过磁场二维实体有限元模型的数值仿真,分析在3种模型下磁流体润滑油膜轴承的磁场分布特性,并比较磁场在油膜区的分布情况。结果表明,永磁铁模型的磁场主要分布在永磁铁、油膜、轴承座以及靠近磁铁的轧辊部分,螺线管模型的磁场主要分布在油膜、轴承座以及靠近磁铁的轧辊部分,亥姆霍兹线圈模型的磁场主要分布在线圈以及油膜的端部;3种模型在油膜区磁场分布沿轴向均呈现中间小、两端大的不均匀现象,且具有端部效应;永磁铁模型和螺线管模型在油膜区磁场沿径向分布均匀,亥姆霍兹线圈模型沿径向分布不均匀。     

基于ZigBee无线传感器网络的气缸位置检测系统

针对工业现场中气缸位置信息传输的问题,提出了构建基于ZigBee技术的无线传感器网络,简要介绍了气缸无线化系统方案,利用CC2430和无触点式磁性传感器完成中心节点和终端节点的硬件设计,并给出系统软件实现流程。通过与Zigbee协议栈的接口,实现Zigbee网络的建立、节点加入、终端设备绑定等功能。经过搭建试验平台验证,该系统可以实现气缸位移信息的无线传输,减少工业现场复杂的布局布线等问题,证实了其有效性和通用性。     

插接式智能组合电器中电子式电流传感器的结构特性分析

电力系统中电子式电流传感器替代传统电磁式电流互感器是发展方向。首先简要介绍一种应用在插接式智能组合电器中的电子式电流传感器的基本测量原理 ,然后对传感器的结构特性进行分析 ,主要包括温度、线圈的多层绕制与不均匀绕制、电流源的放置方式以及磁场的不均匀分布等因素对测量结果的影响 ,最后对多种因素共同作用下的影响进行综合分析 ,分析结果对改善电流传感器的性能有指导作用。     

Development of a solenoid RF coil for animal imaging in 3 T high-magnetic-field MRI

The purpose of this study was to develop a solenoid coil for use with small animals in a 3 Tesla horizontal magnetic resonance imaging (MRI) system, and to investigate image quality by examination of parameters such as signal-to-noise ratio (SNR) and Q-factor. A receiver solenoid coil was formed by winding three separate coils of copper tape around an acryl cylinder. The cylinder was supported at each end. A euthanized rat weighing 240 g was used as a subject animal for imaging. A cylindrical plastic tube containing a solution of 0.7 g/L CuSO(4) was used as a phantom. Measured SNRs were 985 in the phantom image 995 in the rat. The Q-factor was 89 in the phantom and 84 in the rat, in the loaded condition. The homogeneity of the radiofrequency (RF) field was good and the resolution of the image was sufficient to distinguish internal organs from one another in the abdomen of a rat. This study has demonstrated that a solenoid coil may be used to produce good quality images of small animals.     

ESP液压单元电磁阀电磁场动态特性分析

汽车ESP液压单元的电磁阀动态特性对ESP的性能起着至关重要的作用。采用有限元法,以ANSYS软件为平台建立电磁阀电磁场有限元模型,在此基础上分析了在不同工作气隙与线圈电流时电磁阀动铁的电磁力和线圈的自感系数动态响应特性。     

磁致伸缩微小驱动器驱动电磁线圈的设计研究

激励磁场强度对磁致伸缩驱动器驱动位移的大小具有决定作用。对于微小磁致伸缩驱动器 ,如何进行驱动线圈的整体设计 ,使小尺寸线圈产生较大磁场强度是本研究的主要目标。通过优选电磁线圈参数Gcoil确定线圈几何结构尺寸 ,并通过建立磁场强度Hcoil与电磁线圈的电流密度Jcoil进而与电磁线圈线径 之间的关系模型计算和优选电磁线圈线径来提高线圈电磁转化率 ,从而增大激励磁场强度是研究的具体方法。针对 7mm× 2 0mm的Terfenol D试样确定驱动线圈几何参数Gcoil=0 .17,线圈电流密度为最大时的线径 =1mm。 1mm线径的电磁线圈 ,经ANSYS计算 ,比线径为 0 .5mm线圈产生的磁化强度提高了 2 5 %     

Measurement of magnetic susceptibility in pulsed magnetic fields using a proximity detector oscillator

We present a novel susceptometer with a particularly small spatial footprint and no moving parts. The susceptometer is suitable for use in systems with limited space where magnetic measurements may not have been previously possible, such as in pressure cells and rotators, as well as in extremely high pulsed fields. The susceptometer is based on the proximity detector oscillator, which has a broad dynamic resonant frequency range and has so far been used predominantly for transport measurements. We show that for insulating samples, the resonance frequency behavior as a function of field consists of a magnetoresistive and an inductive component, originating, respectively, from the sensor coil and the sample. The response of the coil is modeled, and upon subtraction of the magnetoresistive component the dynamic magnetic susceptibility and magnetization can be extracted. We successfully measure the magnetization of the organic molecular magnets Cu(H(2)O)(5)(VOF(4))(H(2)O) and [Cu(HF(2))(pyz)(2)]BF(4) in pulsed magnetic fields and by comparing the results to that from a traditional extraction susceptometer confirm that the new system can be used to measure and observe magnetic susceptibilities and phase transitions.     

Development of EMA transducer for inspection of pipelines

Electromagnetic acoustic transducers (EMATs) have potential for In-line inspection (ILI) of pipelines compare to other Nondestructive evaluation (NDE) methods, since EMAT doesn’t need to contact and/or coupling material and can detect defects in outside of pipelines. However, improvement of transduction efficiency of EMATs is needed to secure integrity of the pipelines. To improve performance of EMAT, optimization of major parameters, such as strength of permanent magnet, shape of coil, configuration of static and dynamic magnetic fields is required. Thus, in this paper, investigation of transduction efficiency with variation of major parameters are performed by comparison of generated ultrasonic signals. Based on the investigation results, EMATs for ILI of pipelines are designed and fabricated with optimized Periodic solenoid array (PSA) types of meander-line sensor, static magnetic field, and then, performance of the developed EMATs are evaluated by detecting defects in the gas pipelines mounted in the one-bed testing system.     

Stripe sensor tomography

We introduce a general concept of tomographic imaging for the case of an imaging sensor that has a stripelike shape. We first show that there is no difference, in principle, between two-dimensional tomography using conventional electromagnetic or particle radiation and tomography where a stripe sensor is mechanically scanned over a sample at a sequence of different angles. For a single stripe detector imaging, linear motion and angular rotation are required. We experimentally demonstrate single stripe sensor imaging principle using an elongated inductive coil detector. By utilizing an array of parallel stripe sensors that can be individually addressed, two-dimensional imaging can be performed with rotation only, eliminating the requirement for linear motion, as we also experimentally demonstrate with parallel coil array. We conclude that imaging with a stripe-type sensor of particular width and thickness (where the width is much larger than the thickness) is resolution limited only by the thickness (smaller parameter) of the sensor. We give examples of multiple sensor families where this imaging technique may be beneficial such as magnetoresistive, inductive, superconducting quantum interference device, and Hall effect sensors, and, in particular, discuss the possibilities of the technique in the field of magnetic resonance imaging.     

Coil impedance calculation of an eddy current sensor by the finite element method

An eddy current sensor utilizes the variation of coil impedance to perform the measurement of physical parameters, and the coil impedance is an important parameter for investigating the properties of an eddy current sensor. Therefore, the study of approaches to calculation of coil impedance is very important. In this paper, an integral expression for coil impedance with a magnetic substance is given directly. For the convenience of calculation of the coil impedance, this integral expression is further expanded in series form and the coil impedance is computed using Mathematica. Then, two different finite element models of the eddy current measurement system are built on the basis of the finite element modeling theory. The infinite boundary of model 1 is truncated. On the contrary, the infinite boundary of model 2 is simulated completely by an infinite element. The coil impedance and the magnetic distribution are obtained by the finite element method, respectively. The comparison shows that the result obtained by the finite element method is in good agreement with that of the theoretical calculation approach, which indicates the correctness and reasonability of modeling of the eddy current measurement system and calculation of the coil impedance by the finite element method. The text was submitted by the authors in English.     

Research on magnetic pulse sizing of aluminum tube

We investigated the effects of primary system parameters on the magnetic pulse sizing of aluminum tubes. Furthermore, we present the applicable design method of the sizing coils required for tube sizing. For the AA5056-O tube, we utilized the method of three-section sizing, with one coil for the corresponding position and three times discharge. The research results indicate that the length of the solenoid coil is inversely proportional to the nominal peak value of magnetic pressure; the appropriate combination of the discharge voltage and the gap between the tube and die dictates the sizing; the sizing precision can be improved greatly by iterative sizing, and three times is optimal. The experimental results of magnetic pulse tube sizing meet the technical requirements.     

Hall measurements to 40 kilobars under hydrostatic pressure in a piston-cylinder device

A technique for Hall measurements under truly hydrostatic pressures to 40 kilobars is described. The method employs the piston-cylinder apparatus with a Teflon cell to contain a suitable fluid. The necessary magnetic field is generated by a coil placed inside the cell. Hall data can be obtained over the full pressure range, at temperatures from 150 to 300 K. Results for an Al(x)Ga(1-x)As sample are presented as an example.     

微细电解加工的过程检测及精度控制

超短脉冲微细电解加工时,极间加工间隙很小,加工过程的稳定性是影响加工精度的重要因素。在所建立的加工控制系统中,采用两步短路对刀法精确定位电极初始间隙,利用霍尔电流传感器实时检测平均加工电流,动态控制电极的进给运动速度,从而保持不同加工条件下稳定加工的最小加工间隙。进行了微细结构的电解加工试验,通过检测加工过程的状态,保证了加工的稳定性,实现了线宽只有25μm的微细结构加工。     

Physical interpretation of magnetostatic shielding

Plausible physical mechanisms of the effect of a magnetic shield are considered. The shield is treated as a shunt for magnetic flux, as a compensator of an external field by means of fictitious magnetic charges, and as a solenoid compensating for an external field by means of molecular Ampere currents. None of the listed mechanisms taken separately can account for all aspects of magnetic shielding. This effect can be described adequately only if a complex approach is endorsed. Examples of calculations and measurements of magnetic parameters of shields, and their designs are presented.