In situ calibration of rotating sensor coils for magnet testing

An in situ procedure for calibrating equivalent magnetic area and rotation radius of rotating coils is proposed for testing accelerator magnets shorter than the measuring coil. The procedure exploits measurements of magnetic field and mechanical displacement inside a reference quadrupole magnet. In a quadrupole field, an offset between the magnet and coil rotation axes gives rise to a dipole component in the field series expansion. The measurements of the focusing strength, the displacement, and the resulting dipole term allow the equivalent area and radius of the coil to be determined analytically. The procedure improves the accuracy of coils with large geometrical irregularities in the winding. This is essential for short magnets where the coil dimensions constrain the measurement accuracy. Experimental results on different coils measuring small-aperture permanent magnets are shown.     

Design and fabrication of a superconducting magnet for an 18 GHz electron cyclotron resonance ion∕photon source NFRI-ECRIPS

A superconducting magnet was designed and fabricated for an 18 GHz ECR ion∕photon source, which will be installed at National Fusion Research Institute (NFRI) in South Korea. The magnetic system consists of a set of four superconducting coils for axial mirror field and 36 pieces of permanent magnets for hexapolar field. The superconducting coils with a cryocooler (1.5 W @ 4.2 K) allow one to reach peak mirror fields of 2.2 T in the injection and those of 1.5 T in the extraction regions on the source axis, and the resultant hexapolar field gives 1.35 T on the plasma chamber wall. The unbalanced magnetic force between the coils and surrounding yoke has been minimized to 16 ton by a coil arrangement and their electrical connection, and then was successfully suspended by 12 strong thermal insulating supports made of large numbers of carbon fibers. In order to block radiative thermal losses, multilayer thermal insulations are covered on the coil windings as well as 40-K aluminum thermal shield. Also new schemes of quench detection and safety system (coil divisions, quench detection coils, and heaters) were employed. For impregnation of the windings a special epoxy has been selected and treated to have a higher breaking strength and a higher thermal conductivity, which enables the superconductors to be uniformly and rapidly cooled down or heated during a quench.     

Development of an inductive encoder for simultaneous measurement of two-dimensional displacement

Two-dimensional measurements are usually performed by two one-dimensional devices. In this paper, a simple method is developed, which can directly measure the displacements in two dimensions. The measurement is based on inductive method where a flat coil moves on another flat coil and the induced voltages give the displacements in x and y directions. In this research, five flat coils with special patterns are used. One is stationary and four others make the moving part. When moving part moves on the stationary surface, two of the moving coils detect the displacement in x direction and the other two detect the displacement in y direction. The patterns of the coils are designed in a way that there is no interference between axes, i.e., movement in one dimension has no effect on data of other dimension. The experimental results show the effectiveness of the concept. Resolution of 10 μm and no interference between axes are achieved. Better resolution is expected if more precise experimental device is provided.     

电感式位移传感器输出特性仿真分析

电感式位移传感器因其结构及电磁感应特点,不可避免地出现输出非线性与温度漂移的问题,影响其测试精度。针对这一问题,在分析电感式位移传感器结构特性与工作原理的基础上,建立了其输入/输出关系数学模型,并运用Matlab软件进行了仿真分析;探讨了输入/输出参数之间的变化规律。研究结果表明:电感式位移传感器存在一个近似线性工作区域±δmax,其线性度误差受线圈匝数与半径的影响;在其他参数一定的情况下,线圈半径与线圈匝数分别为定值、依次改变线圈匝数与线圈半径时,存在铁芯位移x,且当x≤│δmax│时,传感器输出特性近似成线性关系,线性度好;当x≥│δmax│时,传感器输出特性为非线性关系,线性度差。     

线圈形状及几何参数对电涡流传感器性能的影响

针对电涡流传感器探头线圈形状及其参数对传感器灵敏度和线性范围的影响问题，本文以Biol-Savart定律为基础，推导了具有梯形截面的矩形柱线圈和圆形柱线圈对称轴上任一点的磁场分布，确定了在以位移为检测量的电涡流传感器中采用圆柱线圈更合理，并通过有限元法研究和分析了在线圈匝数密度不变和变化2种情况下圆柱线圈内径、外径、厚度、截面形状（矩形、梯形和倒梯形）对传感器灵敏度和线性范围的影响，为合理选择线圈参数和优化传感器性能提供参考。     

A polyvalent harmonic coil testing method for small-aperture magnets

A method to characterize permanent and fast-pulsed iron-dominated magnets with small apertures is presented. The harmonic coil measurement technique is enhanced specifically for small-aperture magnets by (1) in situ calibration, for facing search-coil production inaccuracy, (2) rotating the magnet around its axis, for correcting systematic effects, and (3) measuring magnetic fluxes by stationary coils at different angular positions for measuring fast pulsed magnets. This method allows a quadrupole magnet for particle accelerators to be characterized completely, by assessing multipole field components, magnetic axis position, and field direction. In this paper, initially the metrological problems arising from testing small-aperture magnets are highlighted. Then, the basic ideas of the proposed method and the architecture of the corresponding measurement system are illustrated. Finally, experimental validation results are shown for small-aperture permanent and fast-ramped quadrupole magnets for the new linear accelerator Linac4 at CERN (European Organization for Nuclear Research).     

差动涡流式连铸结晶器钢水液位仪

介绍了差动涡流式连铸结晶器钢水液位仪的基本原理及构成。仪器可测量0～150mm的钢水液位变化。传感器的核心部分为1个发射线圈和2个接收线圈。信号放大单元采用差动调幅原理．提高了信噪比，扩大了量程。针对结晶器钢水液位测量的特殊性，放大信号再经信号处理单元的若干环节处理成可靠的、适于钢水液位控制的4～20mA线性隔离输出信号。     

基于平面线圈的高分辨力时栅角位移传感器

针对现有时栅角位移传感器采用漆包线绕制工艺加工线圈,导致线圈布线不均且容易随时间发生变化进而影响测量精度的问题,提出一种基于PCB技术的新型时栅角位移传感器。该传感器通过在PCB基板的不同层上布置特定形状的激励线圈和感应线圈,形成两个完全相同并沿圆周空间正交的传感单元;当在两传感单元的激励线圈中分别通入时间正交的两相激励电流后,通过导磁定子基体和具有特定齿、槽结构的导磁转子对传感单元内的磁场实施精确约束,使两传感单元的感应线圈串联输出初相角随转子转角变化的正弦感应信号;最后通过高频时钟脉冲插补初相角实现精密角位移测量。利用有限元分析软件对传感器进行了建模和仿真。根据仿真模型制作了传感器实物,开展了验证实验,并对实验中角位移测量误差的频次和来源进行了详细分析。经过标定和补偿,最终获得了整周范围内误差在-2.82″~2.02″的时栅角位移传感器。理论推导、仿真分析和实验验证均表明,该传感器不仅能实现精密角位移测量,还能在激励线圈和感应线圈空间极距和信号质量不变的情况下,将位移测量的分辨力从信号源头提高1倍,且结构简单稳定、极易实现,特别适用于环境恶劣的工业现场。     

Calculation and measurement of the magnetic field in a large diameter electromagnetic flow meter

An idealized magnet model previously used in a simple coil configuration is applied to a more complicated engineering design problem, where an electromagnetic flow meter in diameter of 500 mm is used with five pairs of coils. The numerical results are compared with measurement data. The difference between theory and experiment and the possible causes of errors are discussed. It is shown that the idealized magnet model is practical for the design and the analysis of the flow meter. The work also shows that the traditional uniform field design based on two dimensional (2D) analysis is not suitable for this kind of flow meter. Thus nonuniform field and 3D analysis is needed.     

多参数协同调制的高分辨力直线时栅位移传感器

为了解决高精度的直线时栅位移传感器依赖空间超精密刻线和刻线不均匀等问题,提出一种采用多参数协同调制的新型直线时栅位移传感器。该传感器通过在PCB基板上布置阵列的激励线圈和特定形状的感应线圈,通过调制感应的面积和线圈的参数,感应出电行波信号,经过整形后用高频时钟脉冲插补得到位移量。通过仿真分析设计与样机实验,得出实验结果表明,在不改变空间极距的情况下,使得分辨力在信号源头上提高1倍且有±68μm的测量精度。     

一种高精度测量仪直线位移装置的设计

针对传统测长仪测量主轴系统存在结构复杂、装调繁琐、笨重且造价高等缺陷,考虑结构的简化与测量精度的提高,采用空气阻尼原理,设计出一种具有空气阻尼控制的直线位移装置,并将其应用于JC系列高精度数显测量仪。研究表明:该装置在测量过程中作直线位移时平稳、顺畅,保障了测量的稳定、可靠,完全满足高精度数显测量仪的使用要求。     

光纤传感测量系统在超导转子旋转装置中的应用

介绍了超导转子旋转驱动原理以及应用在超导转子旋转装置中的一种光纤传感测量系统。光纤传感测量系统包括微位移光纤传感器、转速光纤传感器、电机控制光纤传感器和信号读取图形,该系统能够进行转子悬浮微位移和旋转速度的测量并提供转子旋转所需的控制信号。在4.2K低温下进行了转子悬浮旋转实验,超导球形转子悬浮微位移测量分辨率为10μm,转子转速达到了1013rpm。实验结果为进一步应用光纤传感测量系统精确监控超导转子工作姿态提供了参考。     

微机械电磁阻尼结构分析

提出采用电磁阻尼结构来提高微机械角度调节装置的响应速度.通过建立结构模型和分析结构参数对阻尼效果的影响,给出具体设计实例以及制作工艺,证实该阻尼结构的有效性和可行性.     

STEP卫星加速度计测量头线圈的超导特性测试及改进

为确保STEP卫星超高精度加速度计的测量头线圈三维超导膜在设计的工作电流范围内完全超导,以实现10-18g精度的加速度测量,对测量头线圈进行了低温超导测试,测试证明三维超导膜存在不完全超导缺陷。利用分段测试法对三维膜线圈的二维组成部分进行了测试,确定了测量头线圈超导缺陷的位置,并分析了造成超导缺陷的原因。根据测试和分析结果改进了线圈设计,实现了测量头线圈的完全超导,并标定线圈的最大工作电流为-40～40mA,满足STEP卫星加速度计对超导电流要求的-10～10mA,设计裕度达到300%。通过测试、分析与改进设计,定型了STEP卫星超高精度加速度计测量头线圈的研制,为完成STEP任务奠定了技术基础。同时,实现了三维超导膜线圈的制造与工程应用。     

电液伺服阀中弹簧管刚度测量方式转换的研究

为了使新研制的刚度测量台在伺服阀弹簧管刚度的高精度测量中得到很好地应用,在对传统的手工吊砝码施力、显微镜读取变形的弹簧管刚度测量老方法的受力变形分析的基础上,推导出弹簧管力矩-转角刚度与显微镜观测点线位移的表达关系式,然后选取多个弹簧管进行两种测量方法的对比实验,对实验数据进行分析并同理论推导的表达式进行对比,修正其关系式,给出实际生产应用中两种测量方法的转换修正系数和对应表达式,据此可以将弹簧管刚度测量老方法转换为新型刚度测量台测量方式。     

直线位移微机自动测量系统

为了在空间遥感详查相机研制工作中准确、有效地评价像移补偿系统的像移补偿效果,提出了采用分辨率为0.4μm的光栅尺作为像移补偿片台直线位移的检测元件,采用微机实现直线位移自动测量的检测方法并给出了详细设计思路,包括系统的硬件设计和软件设计。系统具有手动采样、定时采样、外同步采样等多种位移数据读取方式,并可以实时计算出像移补偿片台的位移、速度和速度误差。在实际工程检测应用中实现了极限误差优于0.5μm的检测精度。     

Flywheel energy storage—II: Magnetically suspended superflywheel

This article, the second of a two part paper, describes the general design requirements for a flywheel energy storage system. A new superflywheel energy storage system, using a spokeless, magnetically suspended, composite material pierced disk rotor is proposed. The new system is configured around a permanent magnet (“flux biased”) magnetic suspension system with active control in the radial direction and passive control in the axial direction. The storage ring is used as a moving rotor and electronic commutation of stationary armature coils is proposed. There is no mechanical contact with the rotating ring and long life and low run down losses are projected. A discussion of major components for a 10 kwh system is presented.     

新型两用表面形貌测量仪的研究与开发

开发了一种大量程、高分辨率、非接触式与接触式测量两用的新型表面形貌测量仪器。仪器本体为非接触测量轮廓仪,通过插入接触式测头实现接触测量。非接触式测头采用傅科法自动聚焦原理,接触式测量采用微恒力电感测量原理,它们共用一个音圈电机,各自跟踪电气零位,实现大量程、高分辨率的位移测量。文中还介绍了仪器采用的共运动基面二维工作台。     

一种滚动导轨磨削加工尺寸在线测量仪

针对滚动导轨磨削加工尺寸的在线测量问题,介绍了一种导轨磨削加工尺寸在线测量仪,该仪器以半导体激光器配合光电二极管作工件位置检测器、整体切割的平行弹簧,配合音圈电机作测头驱动器和双电感位移传感器作偏差尺寸检测器,采用相对测量法,配合数据采集卡、工控机和上层控制软件,能对导轨磨削尺寸进行在线检测。     

A high-sensitive static vector magnetometer based on two vibrating coils

A static vector magnetometer based on two-dimensional (2D) vibrating coils actuated by a piezoelectric cantilever is presented. Two individual sensing coils are orthogonally fastened at the tip of cantilever and piezoelectric sheets are used to excite the cantilever bending. Due to off-axis coupler on the tip, the cantilever generates bending and twisting vibrations simultaneously on their corresponding resonant frequencies, realizing the 2D rotating vibrations of the coils. According to Faraday-Lenz Law, output voltages are induced from the coils. They are amplified by a pre-amplifier circuit, decoupled by a phase-sensitive detector, and finally used to calculate the vector of magnetic field at the coil location. The coil head of a prototype magnetometer possesses a dc sensitivity of around 10 μV/Gs with a good linearity in the measuring range from 0 to 16 μT. The corresponding noise level is about 13.1 nT in the bandwidth from 0.01 Hz to 1 Hz.