一种用于盘孔裂纹检测的差动式涡流探头的设计与实现

为了实现对某型发动机篦齿盘均压孔的原位、无损探伤,设计了一种差动式的涡流检测探头,探头由一个激励线圈和两个感应线圈组成,由于检测线圈结构上的对称性使得探头对盘孔周边的表面裂纹敏感,同时对激励线圈和检测线圈匝数比的优化设计也能有效增强输出的差动信号,降低干扰。信号调理电路采用正交锁相放大对输出进行正交分解,得到包含信号幅值和相位信息的两路直流分量作为裂纹检测的特征量。对篦齿盘均压孔标准试件的检测结果表明该探头能够很好地实现盘孔周边微小裂纹的检测,灵敏度高。同时,这种差动式的探头结构同样也可用于其它盘孔的裂纹检测。     

VCM design with round coil and axe-shaped magnet for hard disk drive actuator

In this paper, we proposed a novel single-sided magnet voice coil motor (VCM) design that can reduce out-of-plane force. Out-of-plane force of a VCM causes the actuator vibration, which results in settling vibration and acoustic noise. The proposed single-sided magnet VCM consists of a round coil and an axe-shaped magnet. We designed the optimized configuration by using numerical magnetic field simulation and compared its performance with those of a conventional VCM. Torsional moment was reduced by 90% at the worst position of the middle track, and bending moment was reduced by 50% at the worst position of the inner track compared with a conventional VCM. Rotational moment in our VCM was almost the same as that of the conventional one. We manufactured an actuator with the new design VCM and confirmed that the new single-sided magnet VCM shows a good performance as expected, although its magnet volume and coil resistance were almost the same as a conventional design. The measured frequency response of the actuators from the coil current to the head displacement showed that the coil torsional mode vibration of the proposed VCM is reduced remarkably.     

电涡流位移传感器线圈电磁场仿真分析

由于电涡流传感器的探头参数对其性能的影响比较显著,设计电涡流传感器的关键在于对探头线圈进行优化。采用有限元技术(AnsoftM axwell软件)对包括线圈和金属靶板的电涡流位移传感器进行电磁场数值仿真,得到了激励线圈的磁力线和被测靶板中电涡流的密度分布。并通过线圈等效阻抗的实验与计算结果定量比较,验证了仿真分析过程的正确性,为进一步完善传感器的理论分析和优化设计打下了基础。     

影响磁导率测试的电磁检测探头设计因素分析

为了实现对某型火炮关键零部件硬度的原位无损检测,提出了一种基于磁导率测试的硬度电磁检测探头。该探头以差动方式实现检测,它包括检测线圈和参考线圈,磁导率变化引起感应电压变化由电桥电路实现输出。在此基础上,进一步建立对应的电磁场—电路耦合仿真的有限元模型,深入分析了探头结构和尺寸、检测频率及后端电桥电路对检测性能的影响,其结果可为实际探头的制作提供理论指导。     

Enhanced locomotive and drilling microrobot using precessional and gradient magnetic field

We propose a new electromagnetic actuation (EMA) system for an intravascular microrobot with steering, locomotion and drilling functions. The EMA system consists of 3 pairs of Helmholtz coil and 1 pair of Maxwell coil. Generally, Helmholtz coils can align a microrobot in a desired direction by generating a uniform magnetic flux. If the uniform magnetic field generated by Helmholtz coils can be rotated, a microrobot with Helmholtz coils can also be rotated. On the other hand, a Maxwell coil, which generates a constant gradient magnetic flux, can supply the propulsion force for the microrobot. A microrobot actuated by the proposed EMA system has a spiral shaped body containing two magnets with different magnetization directions. With the proposed EMA system, the microrobot can move to the target region and perform drilling there by the precessional magnetic field of the Helmholtz coil pairs. The propulsion force for the microrobot is produced by the gradient magnetic field generated by the Maxwell coil pair. The moving velocity and the drilling performance of the microrobot can be increased by the propulsion force of the Maxwell coil pair. Through various tests, the feasibility and enhancement of the microrobot actuated by the proposed EMA system were verified.     

一种简化的室内机器人电磁定位算法与系统

文章提出了一种简化的室内机器人的电磁定位算法。在定位空间内布置一个发射线圈和一个三轴接收线圈,形成电磁耦合系统。以接收线圈三轴为参考建立空间直角坐标系,并对发射线圈加载正弦电信号作为激励信号,产生交变电磁场。接收线圈感应到磁场的变化,通过测量计算感应耦合的强度特征值,确定移动目标的位置参数。本系统将三轴接收线圈固定,而将水平发射线圈置于平面移动机器人目标之上,这样可将定位算法简化。根据磁偶极子模型,提出了解析计算方法。通过仿真和实验,证明该方法能够满足室内机器人的定位要求,是可行且有效的。     

电磁超声换能器优化设计与板状结构损伤成像应用研究

提出了一种用于板状结构损伤成像的虚拟电磁超声换能器EMAT(Electromagnetic Acoustic Transducer)阵列.由螺旋线圈和圆柱形永磁铁组成的电磁超声换能器可以通过洛伦兹力在铝板中有效地激发低频散和高幅值的单一S0模态兰姆波.实验研究了电磁超声换能器配置参数(如激发频率,螺旋线圈外径、螺旋线圈内径和提离距离)对S0模态兰姆波性能的影响.另外,将接收电磁超声换能器移动到用于接收兰姆波的多个预定义位置来构建虚拟传感器阵列,实验研究了阵元间距和阵元数量对成像结果的影响.结果表明,通过相控虚拟聚焦成像方法,虚拟电磁超声换能器阵列的成像结果与实际损伤位置吻合良好.     

相控式与偏磁式消弧线圈的研究

分析了相控式消弧线圈与偏磁式消弧线圈的工作原理,详细介绍了这两种消弧线圈补偿电流的特性,阐述了电网正常运行和发生单相接地故障时这两种消弧线圈的工作特性,从而得出结论:带滤波电路的相控式消弧线圈有一定的滤波作用,但由于存在滤波电路而使相控式消弧线圈的补偿效果较差;偏磁式消弧线圈既能有效滤波,又能起到很好的补偿效果。     

不规则直流线圈磁场的计算方法研究

将不规则直流线圈等效为若干段载流直导线的组合,通过坐标变换和磁场变换计算出单根载流直导线的磁场,进而叠加求和得到整个不规则直流线圈的磁场.计算示例表明,该方法计算不规则直流线圈的磁场简单易行,可用于实际工程中线圈磁场的计算.     

抑制电磁干扰的悬浮间隙传感器检测线圈结构设计

高速磁浮列车悬浮间隙中存在着牵引磁场、悬浮磁场等多种磁场,它们的高次谐波耦合到检测线圈中容易形成电磁干扰对悬浮间隙传感器造成影响。通过设计8字结构线圈,大幅度抑制了这种共模形式的电磁干扰。针对双检测线圈可能存在相互电磁干扰问题,通过调整双线圈之间相对位置,使两线圈间互感接近于零时,就可消除该种干扰,据此,确定两检测线圈间错位1/3线圈长度,通过试验验证了可行性。     

Design multiple-layer gradient coils using least-squares finite element method

The design of gradient coils for magnetic resonance imaging is an optimization task in which a specified distribution of the magnetic field inside a region of interest is generated by choosing an optimal distribution of a current density geometrically restricted to specified non-intersecting design surfaces, thereby defining the preferred coil conductor shapes. Instead of boundary integral type methods, which are widely used to design coils, this paper proposes an optimization method for designing multiple layer gradient coils based on a finite element discretization. The topology of the gradient coil is expressed by a scalar stream function. The distribution of the magnetic field inside the computational domain is calculated using the least-squares finite element method. The first-order sensitivity of the objective function is calculated using an adjoint equation method. The numerical operations needed, in order to obtain an effective optimization procedure, are discussed in detail. In order to illustrate the benefit of the proposed optimization method, example gradient coils located on multiple surfaces are computed and characterised.     

Interactive blood-coil simulation in real-time during aneurysm embolization

Over the last decade, remarkable progress has been made in the field of endovascular treatment of aneurysms. Technological advances continue to make it possible for a growing number of patients with cerebral aneurysms to be treated with a variety of endovascular strategies, essentially using detachable platinum coils. Yet, coil embolization remains a very complex medical procedure for which careful planning must be combined with advanced technical skills in order to be successful. In this paper, we describe a complete process for patient-specific simulations of coil embolization, from mesh generation with medical datasets to computation of coil-flow bilateral influence. We propose a new method for simulating the complex blood flow patterns that take place within the aneurysm, and for simulating the interaction of coils with this flow. This interaction is twofold, first involving the impact of the flow on the coil during the initial stages of its deployment, and second concerning the decrease of blood velocity within the aneurysm, as a consequence of coil packing. We also propose an approach to achieve real-time computation of coil-flow bilateral influence, necessary for interactive simulation. This in turns allows to dynamically plan coil embolization for two key steps of the procedure: choice and placement of the first coils, and assessment of the number of coils necessary to reduce aneurysmal blood velocity and wall pressure. Finally, we provide the blood flow simulation results on several aneurysms with interesting clinical characteristics both in 2D and 3D, as well as comparisons with a commercial package for validation. The coil embolization procedure is simulated within an aneurysm, and pre- and post-operative status is reported.     

线圈材料对电涡流传感器温漂特性影响研究

温漂是表征电涡流位移传感器在工作温度范围测量的稳定性重要参数,本文通过对电涡流传感器探头线圈物理性能的分析,提出阻抗是影响温度稳定性能的主要因素,并通过改变探头线圈材料来降低温度对阻抗的影响,并配选出一种新型合金取代原有线圈材料.实验验证了这种方法可以抑制温漂.     

Novel electromagnetic actuation (EMA) method for 3-dimensional locomotion of intravascular microrobot

A new electromagnetic actuation (EMA) method is proposed for 3-dimensional locomotion of a microrobot. Generally, the EMA system uses Helmholtz coils and Maxwell coils. The Helmholtz coil pair generates a uniform magnetic flux density and the Maxwell coil pair generates a uniform gradient magnetic flux. The microrobot can be aligned to the desired direction by the Helmholtz coils and then, be propelled in the aligned direction by the Maxwell coils. However, many previous EMA systems have been restricted to 2-dimensional planar actuation. The EMA system proposed in this paper consists of a pair of stationary Helmholtz–Maxwell coils and a pair of rotational Helmholtz–Maxwell coils. This new EMA system can manipulate a microrobot in 3-dimensional space. For accurate actuation of a microrobot, the gravitational force, which influences the motion of microrobot, has to be analyzed and compensated. Through various experiments, the performance of the proposed EMA system was evaluated. Finally, a microrobot was test-driven in a blood vessel phantom, and the result of the test drive verified the feasibility of 3-dimensional motion of a microrobot by the new EMA system.     

一种涡流检测探头响应与缺陷大小的关系研究

为了实现涡流无损检测的定量评估,设计了一种直接测量涡流磁场的涡流检测探头,该探头包含两个激励线圈和一个检测线圈.通过有限元法建立三维涡流仿真模型,对比研究导体内有无圆柱形缺陷时涡流的分布情况以及检测线圈响应的变化量.仿真结果显示,当导体内存在圆柱形缺陷时,涡流密度会集中分布在缺陷的侧面区域并且其大小会增加;检测线圈中响应的变化量与缺陷体积之间的关系满足两个指数函数的线性组合,对于体积较小的缺陷,检测线圈中响应的变化量与缺陷的体积近似成正比关系.实验结果验证了导体内存在小体积的缺陷时,检测线圈中响应的变化量与缺陷的体积之间的近似正比关系,证明了该结构的探头可以用于对缺陷的定量研究.     

基于阻抗原理的磁弹性传感器测试仪设计

设计了一种基于阻抗原理的磁弹性传感器共振频率测试仪。系统集成了微控制器、交流激励信号发生单元、直流偏置信号发生单元和有效值检测电路单元,并通过RS-232串口总线实现与上位机之间的通信。交流激励信号电路采用压控电流源方式,避免了线圈阻抗变化对交流激励电流的影响。实验结果表明：测试仪可以快速检测磁弹性传感器的共振频率,稳定性好,精度高,系统操作简单,集成度高,能够满足磁弹性传感器研究中的检测要求。     

Wireless magnetic resonant energy transfer system based on micro 3D flexible MEMS Litz coils

Wireless magnetic resonant energy transfer system shows more superiority in energy transfer efficiency and relative position parameters than that of inductive coupling system. It has been recognized as the best power supply method for implantable medical devices. The dimension and performance of the resonant coil is the key point that has great effect on the transfer efficiency and implantable applications. In this paper, high Q flexible planar and roll Litz coil is designed and implemented for the wireless energy transfer system. L and Q for 3D Litz coil is calculated and compared by theoretical model. The roll-Litz coil shows better performance in L and Q with smaller size comparing with the planar-Litz coil. Wireless energy transfer system based on two and four resonant coils is build up. The experimental results show that the energy transfer efficiency is improved by using the high Q 3D Litz coils. What’s more the roll-Litz four coil system shows priority in higher transfer efficiency with smaller size comparing with planar-Litz coil system. The efficiency of four-coil transfer system based on roll-Litz coils gets 48 % higher than the two-coil system with 1.0 cm transfer distance, and 10 % higher than the four-coil transfer system based on planar-Litz coils with 1.5 cm transfer distance.     

Fabrication of microcoils with narrow and high aspect ratio coil lines

Recently, there has been a growing requirement to reduce their size of actuators. However, the miniaturization of actuators has made little progress since this requires micro-fabrication, processing, and other new techniques that are not compatible with traditional machining technologies. We have forcused on the fabrication of electromagnetic type microactuators that could be driven at low voltage and with high efficiency but it is well known that existing technologies for miniaturization of these devices are unsuitable because the allowable current path would be too small in microscopic applications. Therefore, we have proposed the development of a spiral microcoil with narrow width and high aspect ratio lines that can be fabricated using X-ray lithography and metallization techniques. We have fabricated spiral structures consisting of coil lines with widths of 10 μm and with aspect ratios of over 5. We have also succeeded in electroforming copper onto seed layers and have demonstrated isotropic copper etching in order to form narrow width coil lines to act as current paths. In addition, we have estimated the suction forces that can be generated by electromagnetic actuators fabricated using these coils. These results give rise to the expectation that practical high performance spiral microcoils could be manufactured using these techniques, in spite of their miniature size.     

子母弹线圈间耦合对无线传输效率的影响

在子母弹无线能量传输系统中,各个线圈间交叉耦合,使系统传输效率受到影响;通过建立并联谐振无线能量传输系统模型,在子弹线圈组间耦合很小的情况下,分析各个线圈间耦合对系统传输效率的影响,得到在最大传输效率时子弹线圈的频率条件;最后通过实验对推导公式呈现出的子弹线圈频率偏移方向,以及线圈间耦合对系统传输效率的影响进行了验证;结果表明,在对多个子弹线圈进行无线能量传输时,达到最大传输效率时子弹线圈的频率高于初始谐振频率;当子弹线圈与母弹线圈间距较大时,应采用多个母弹线圈对其传输能量;并且减小子弹和母弹线圈间距,可以提高系统最大传输效率。     

带磁芯励磁线圈的阻抗匹配

带磁芯励磁线圈的阻抗匹配是磁致伸缩器件设计和应用的基础.为使励磁线圈产生较大磁场,利用AMH-1M-S型磁特性测试系统,测试了在不同频率下线圈磁芯材料硅钢片的B-H和u-H曲线,同时计算了带磁芯励磁线圈的复阻抗.根据串联谐振电路原理,理论上计算了电路谐振时的电容值.搭建了实验平台,利用示波器采集电源电压和串接在电路中采样电阻电压的数值,计算了串接匹配电容前后电路的阻抗变化.实验结果表明:串接匹配电容后,在励磁电流频率为50 Hz、100 Hz、150 Hz时,励磁线圈总阻抗下降了48.95%、61.34%、60.06%,励磁电流分别增加了95.88%、158.62、150.38%.