磁浮列车磁场测量系统中运动控制平台的设计

磁浮列车气隙磁场的测量可以为列车电磁系统的设计和控制提供重要依据.本文对气隙测量系统中磁传感器运动控制平台的设计进行了详细介绍,阐述了运动控制平台的工作原理和光栅尺信号的处理方法.采用双计数器鉴相法消除了光栅尺抖动的影响,提高了传感器的定位精度.同时采用电流矢量恒幅旋转的细分方法实现了步进电机恒转矩均匀细分控制,提高了步进电机的分辨率和运行稳定性.所设计的运动控制平台的定位精度可以达到1μm.     

尖劈状磁场中磁流体磁性微粒的受力分析

通过有限元方法对尖劈形磁场中磁流体磁性微粒所受的磁场力进行了数值分析,分别给出了磁场气隙处磁通量和磁场强度随不同气隙宽度和夹角的变化规律.在此基础上,利用虚位移法和麦克斯韦应力张量法计算磁流体磁性微粒在气隙上方所受的磁场力.结果表明,随着气隙宽度的减小,磁通量、磁场强度和磁场力明显增加;随着气隙夹角的增加,磁通量、磁场...     

异步电机静偏心状态电磁激励力的建模分析与实验研究

为了建立异步电机磁-固耦合动力学模型,并准确预测电机在不平衡运行状态下的气隙径向电磁激励力,推导转子-气隙系统的拉格朗日-麦克斯韦能量方程,采用4阶龙格库塔法计算异步电机存在静偏心时的转子振动响应的数值解,根据转子实际振动偏心计算各阶次不平衡电磁力波,最后分析转子主轴系统弯曲刚度以及初始静偏心大小对气隙磁场和径向电磁力的影响。通过实验研究验证了理论建模和数值计算的准确性。结果表明,在异步电机静偏心状态下,气隙磁场受转子振动偏心影响而发生改变,电机转子弯曲刚度越小且初始静偏心越大,气隙磁场的分布就越不均匀,导致电机定子受到的径向电磁激励力也会越大。因此,该模型和数值解有助于提高异步电机不平衡电磁力的计算精度,对细长主轴异步电机尤其有效。     

磁浮列车磁场测量系统中运动控制平台的设计

磁浮列车气隙磁场的测量可以为列车电磁系统的设计和控制提供重要依据．本文对气隙测量系统中磁传感器运动控制平台的设计进行了详细介绍,阐述了运动控制平台的工作原理和光栅尺信号的处理方法．采用双计数器鉴相法消除了光栅尺抖动的影响,提高了传感器的定位精度．同时采用电流矢量恒幅旋转的细分方法实现了步进电机恒转矩均匀细分控制,提高了步进电机的分辨率和运行稳定性．所设计的运动控制平台的定位精度可以达到1μm．     

用于地震勘探的新型高精度地震检波器研究

论述了一种新型适合高分辨率地震勘探的高灵敏度、低失真度的高精度地震检波器.为使检波器获得高灵敏度、低失真度,对检波器内的电磁场进行了系统的研究.研究表明:要获得高灵敏度、低失真度的高精度检波器,检波器必须具有磁感应强度高而均匀的气隙磁场.采用辐向磁场磁路设计和检波器结构优化设计.设计中采用辐向冲磁的FeCo基磁钢和专业的磁路设计软件.所设计的检波器获得了理想的气隙磁场,气隙磁场中均匀场的宽为13 mm,磁感应强度为 560mT.所设计的检波器特性参数为:频率:f=10Hz±2.5%灵敏度:S=280mV/cm/s±2.5%阻尼:b=0.7失真度:d<0.05%.     

基于永磁体的小口径磁流变抛光装置设计与优化

针对小口径、高陡度光学元件的特点,设计了抛光轮直径为20 mm并运用永磁体作为磁场发生器的磁流变抛光装置.首先根据静磁场基本理论对磁场分布进行计算和仿真,以此为基础对抛光装置进行了详细设计;然后根据装置结构和磁场分布特点,以及流体流动过程中流速与喷管半径之间的关系完成喷管等关键部件的优化;最后提出了双层喷管设计实现屏蔽干扰磁场的方法.实验结果表明,所设计的装置能够实现磁流变液的稳定循环,并获得稳定的去除函数.为确定该装置的材料去除能力,使用K9玻璃进行了工艺实验,确定了K9光学元件的峰值去除效率为4.2μm/min.     

真空管道HTS磁浮系统中振动耗能法电磁制动分析

为了实现高温超导(HTS)磁浮车的无接触的制动,本文提出一种基于振动耗能的电磁制动方法。在永磁轨道与磁浮车的悬浮气隙中增加一层固定在车体上的电磁线圈,以线圈通电的方式改变磁场分布而得到在轨道上方的磁场分布不均衡的效果。磁浮车体的运动方向上的动能将转化到与其运行垂直方向上的阻尼振动耗掉而使车体减速,其阻尼系数通过闭合线圈的方式改变。以真空管道中运行的HTS磁悬浮车为例,用理论分析得出所加电磁线圈的自阻值与外接电阻的阻值之和与耗能的关系,最后在西南交通大学真空管道HTS磁浮系统实验平台上实验验证了该方法的合理性与有效性,为将来的真空管道磁浮交通系统的设计提供参考。     

基于Ansoft的电磁装置仿真分析

本文介绍了在Ansoft环境下进行电磁场仿真分析的方法,并以试验器设备中的电磁装置为研究对象,利用Maxwell 3D模块建立三维仿真模型,在建立仿真模型的基础上,对电磁设备的基本特性进行了仿真分析,获得了电磁装置工作气隙的磁场分布。仿真结果可以用于指导电磁设备的设计和优化。     

磁悬浮运动中电磁铁磁滞特性的非线性影响研究

超精密磁悬浮运动控制中,电磁铁铁心及衔铁导轨中存在的磁滞特性是导致电磁力难以实现精确控制的重要原因之一.研究磁滞特性对电磁力的非线性影响规律并建立其非线性模型具有重要意义.通过研究磁悬浮精密运动中电磁铁磁滞特性对气隙处磁感应强度的影响,分析了带气隙磁路磁滞特性建模原理,建立了包含Jiles Atherton模型的电磁铁磁浮力非线性模型,并采用粒子群优化算法对该模型参数进行实验验证.结果表明,磁悬浮精密运动中电磁铁磁滞特性不容忽视,采用经参数辨识得到的新模型比采用传统模型计算得到的气隙磁感应强度值更精确、更接近实测值.研究结果为提高磁悬浮精密运动中电磁力的精确控制提供了重要参考价值.     

低频电磁振动台非均匀气隙磁场优化设计

针对大行程低频电磁振动台气隙磁感应强度参数非线性导致振动激励信号产生失真的问题,在电磁振动台机电耦合模型分析基础上,采用电路等效原理建立大行程磁路简化数学模型,并基于Ansys Maxwell软件对气隙磁感应强度的非均匀分布特性进行仿真分析。基于连续混合整数非线性规划算法,分别仿真分析不同内磁轭母线轮廓及端面结构非线性参数对应的气隙磁感应强度分布特性,得到具有最小不均匀度的变气隙及变截面磁路最优解。仿真结果表明:变气隙和变截面结构分别将优化前25.95%的不均匀度降低到7.09%和2.70%,变截面结构具有更好的优化效果。设计的优化磁路结构可有效改善大行程低频电磁振动台气隙磁感应强度的非线性,降低输出振动信号的失真度,提高低频振动校准精度。     

Magnetic Field Analysis of Inset and Surface-Mounted Permanent-Magnet Synchronous Motors Using Schwarz–Christoffel Transformation

In this paper, we apply an original numerical Schwarz–Christoffel (SC) transformation to analyze magnetic field originating from permanent magnets and the armature winding currents in a slotted air gap of an inset permanent-magnet synchronous motor. We obtained the solution of the SC integral numerically using Matlab SC Toolbox. We used this field solution to calculate both cogging torque and electromagnetic torque by integrating the Maxwell stress tensor inside the air gap. The case without inter-polar piece, which is equivalent to a surface-mounted permanent-magnet motor, is also treated. The accuracy of the developed method is verified by comparing its results with those obtained from the developed numerical finite-element models.      

Research on Torque Calculation Method of Permanent-Magnet Spherical Motor Based on the Finite-Element Method

In this paper, the finite-element method (FEM) is used to calculate the spinning torque of the permanent-magnet (PM) spherical motor. Three-dimensional (3-D) FE model of the PM spherical motor is established. Spinning torque distribution on the spherical surface and its variation curve on the equator are obtained respectively. In order to avoid the complicated torque calculation process under 3-D magnetic field and thus reduce the computational burden, the torque calculation method based on the 2-D conversion model is proposed. This method equivalently simplifies the magnetic field of the spherical PMs and the shape of cylindrical stator windings to be simulation parameters of the 2-D conversion model. With these parameters, 2-D conversion model of the PM spherical motor is established. Spinning torque variation curves obtained by the 3-D model and the 2-D conversion model respectively are compared and the results agree extremely well. By comparing the maximum static torque (MST) obtained under different configuration parameters of the PM spherical motor, it is found that the errors are within the allowable range. Therefore, the reliability of the proposed torque calculation method in the paper is verified. Finally, based on the 2-D conversion model, variation curves of the MST with the length of the air gap, the ampere turns, the length of stator windings and the outer radius of stator windings are obtained, and they are validated by those based on the 3-D model. These results can provide the basis for the optimization of the PM spherical motor.      

超精密大行程麦克斯韦磁阻驱动器磁场建模与推力分析

为了克服大行程麦克斯韦磁阻驱动器在大气隙下漏磁大幅增加、气隙区磁场分布不均匀且非线性强烈等现象导致的磁场和推力解析模型精度较低等问题,利用考虑综合高斯函数的加权漏磁系数的磁路建模方法,改进了磁阻驱动器的三维漏磁分布计算方式,并得到了可准确描述其推力与输入电流函数关系的解析模型,从而为该类驱动器的设计及控制提供重要依据。首先,建立了大行程麦克斯韦磁阻驱动器考虑漏磁前后的工作磁路,分析了永磁偏置磁路的作用及使用永磁偏置结构后仍具有非线性的原因,并利用安培环路定律和磁路的欧姆定律以及磁场的可叠加性,建立了该磁阻驱动器的推力解析模型。然后,为了优化解析模型,提出了基于高斯曲线的加权漏磁系数计算方法,同时利用有限元仿真软件对大行程麦克斯韦磁阻驱动器的三维磁场分布及漏磁系数进行了分析计算,得到了考虑加权漏磁系数的推力解析模型。最后,搭建了大行程麦克斯韦磁阻驱动器推力测试系统,并通过对比优化前后解析模型计算推力与仿真推力和实测推力,验证了解析模型的准确性。结果表明,优化后解析模型的均方根误差仅为优化前的11.1%,其精度得到有效提升;同时,优化后解析模型计算推力与实测推力之间的均方根误差小于0.6 N,精度较高。研究结果对高端微纳制造装备与测量仪器中新型超精密驱动部件的设计有一定意义和参考价值。     

Simulation of the Magnetic Induction Vector of a Magnetic Core to be Used in FFC NMR Relaxometry

This paper is a contribution for the assessment and comparison of magnet properties based on magnetic field characteristics particularly concerning the magnetic induction uniformity in the air gaps. For this aim, a solver was developed and implemented to determine the magnetic field of a magnetic core to be used in Fast Field Cycling (FFC) Nuclear Magnetic Resonance (NMR) relaxometry. The electromagnetic field computation is based on a 2D finite-element method (FEM) using both the scalar and the vector potential formulation. Results for the magnetic field lines and the magnetic induction vector in the air gap are presented. The target magnetic induction is 0.2 T, which is a typical requirement of the FFC NMR technique, which can be achieved with a magnetic core based on permanent magnets or coils. In addition, this application requires high magnetic induction uniformity. To achieve this goal, a solution including superconducting pieces is analyzed. Results are compared with a different FEM program.     

Site-Specific Magnetic Assembly of Nanowires for Sensor Arrays Fabrication

The effect of variation in local magnetic field on magnetic assembly of 30 and 200 nm diameter Ni nanowires synthesized by template directed electrodeposition was investigated with different materials (Ni–Ni and Ni–Au) and shapes of electrodes. Ni–Au paired electrodes improved confinement of the assembled Ni nanowires across the electrode gap because of the narrower distribution of magnetic field around the gap between the two electrodes. Simulation results indicated a local magnetic field strength at the electrode tip increased by a factor of 2.5 with the use of a needle-shape electrode as compared to rectangular-shape electrode. The resistance of nanowire interconnects increased as the applied voltage was raised, and under the same applied voltage, the increase in resistance is further enhanced at lower temperatures because of higher current density.      

气隙对电流比较仪磁屏蔽屏蔽效能影响的研究

电流比较仪的磁屏蔽是减小磁性误差,提高测量精度的重要组成部分,但实际中磁屏蔽往往存在气隙导致屏蔽效能下降,影响比较仪的测量精度。通过建立有限元模型,研究磁屏蔽上引线穿出气隙对屏蔽效能的影响,得到了屏蔽效能随气隙高度变化的规律。对于该模型,气隙高度小于10 mm时,屏蔽效能下降不大;当气隙高度大于10 mm后,屏蔽效能下降明显。最后,搭建实验平台验证气隙对屏蔽效能的影响,实验结果与有限元计算结果相吻合,小气隙对屏蔽效能的影响不大,当气隙超过一定高度后对屏蔽效能影响很大,实际设计中应予以避免。     

Magnetic imaging of reinforcing steel

A new nondestructive evaluation technique is proposed to image steel reinforcement in reinforced concrete structures. One imposes a static magnetic field on a reinforced concrete member and measures the distortion of that field due to the magnetization of the reinforcement. The distribution of magnetization within the member is determined by inverting linearized fundamental equations of magnetostatics. A second set of equations, involving the ambient magnetic field and the magnetic susceptibility of steel, relates the magnetization to the volume of steel. Simple finite-element simulations were performed to investigate the performance of the reconstruction algorithm. The present version of the algorithm differentiated clearly between widely-spaced cubes of steel and air. The reconstructions were less successful when the cubes were adjacent. Some areas that deserve further development were identified. The magnetostatic principles underlying the imaging technique could also be applied to locate ferromagnetic objects for other applications.     

磁流体密封的磁路设计及磁场有限元分析

为了在磁流体密封结构的密封间隙内获得最大的磁能积以及提高磁流体密封的耐压能力,在磁路设计理论和磁流体密封理论的基础上,对一种并联型的磁流体密封结构进行磁路设计,采用有限元法数值计算出磁流体密封结构中的磁场从而计算出磁流体密封耐压能力,并对计算结果进行了分析和讨论。结果表明:极靴与永磁体结合处的漏磁以及中间极靴轴向长度较短,导致中间极靴与两侧极靴下密封间隙内的磁感应强度差成非线性关系,也导致了磁路法低于有限元法计算出的磁流体密封耐压能力;中间极靴下密封间隙内磁感应强度较大导致两侧极靴下密封间隙内的磁感应强度差近似相等。     

A Quantitative Comparative Analysis of a Novel Flux-Modulated Permanent-Magnet Motor for Low-Speed Drive

A novel low-speed flux-modulated (FM) permanent-magnet (PM) motor that breaks the traditional design rule, which stipulates that the number of stator pole pairs and the number of rotor pole pairs must be the same, is proposed. The FM motor has a special physical structure with iron segments in the air gap to modulate the magnetic field. In the design, the free space between adjacent stationary iron segments also acts as ventilating ducts to help improving the heat dissipation and ventilation of the motor. Its cogging torque is very small. In this paper, a rule for comparing the power density of electric motors is proposed. The performance of the FM motor is compared with those of a magnetic-geared PM motor, a traditional PM motor, and a fractional-slot PM motor by using magnetic field finite-element analysis.