A new active position sensing method for ropeless elevator

Traditional cable driven elevators perform poorly in high-rise buildings because the weight of the cable limits the payload, and its elasticity degrades control performance. Further, it is not mechanically possible to include several elevator cars in the same hoistway because of the cable. However such multi-car elevator systems are desirable since they reduce passenger waiting time and reduce the space requirements of the elevator system. A promising solution is to use long armature linear motors spanning the hoistway to directly drive elevator cages. In such applications, the mover position sensing method must be explicitly addressed since most active position sensing methods require traveling cables, which are also an obstacle for multi-car elevator systems.In this paper, the linear-motor active position sensing method is formally introduced and the principle of operation, design and real-time operation methods are presented. The proposed method is used to measure the position of the mover of a long armature permanent magnet linear synchronous motor requiring no active components on the mover, thus traveling cables are eliminated. The principle of operation is inspired by linear variable differential transformer: A magnetic shunt positioned at a fixed distance ahead of the mover deforms the magnetic field created by one of the armature coils. The deformation can be determined by measuring the induced voltages on the neighboring coils, and the position of the shunt, and thus the mover, can be calculated.A design method for the optimal dimensions of the shunt for a given armature to provide long measurement range and small maximum position error is presented, accompanied by a real-time measurement algorithm that will enable the motor to be driven using the method. Finally the method is verified by simulations and experimental results conducted on a full scale linear-motor elevator prototype that was constructed in the laboratory.     

RKA 引导磁场设计研究

本文为RKA 设计了一套秒级脉冲磁场系统,该系统主要由磁场线圈和磁场电源两部分组成,磁场线圈通过迭代 获得所需截面形状,之后进行了必要的电磁参数设计,对与之配套的磁场电源提出了主要技术要求和时序控制问题。最 后初步测试了RKA 磁场位形情况,经测试,该秒级脉冲磁场性能稳定,满足RKA 磁场约束要求。     

Development of a magnetizing stage for in situ observations with electron holography and Lorentz microscopy

A magnetizing stage, by which approximately horizontal magnetic fields can be applied to thin-foiled specimens, has been developed so that magnetization process can be observed in situ with electron holography and Lorentz microscopy. It is possible to apply magnetic field up to 200 Oe without serious image distortion by utilizing the magnetizing stage, beam-deflection-back coils and a magnetically shielded objective lens. The devised system can be used to studies of magnetization processes in many soft magnets.     

一体化电磁聚焦系统加载技术的研究

为了提高行波管用电磁聚焦系统的效率,在一体化电磁聚焦系统的无加载设计基础上,进行了加载技术的研究,通过使用CST软件和MTSS软件进行仿真设计,然后进行装管验证。研究结果表明：对某X波段大功率耦合腔行波管的一体化电磁聚焦系统进行加载后,可实现对电磁聚焦磁场的局部调节,且基本不影响相临区域的磁场,在获得相同磁场强度的条件下,线包的耗散功率降低了3%左右。因此,对一体化电磁聚焦系统进行加载技术的研究有较好的实际意义。     

Peripheral nerve stimulation by gradient switching fields in magnetic resonance imaging

A heterogeneous model of the human body and the scalar potential finite difference method are used to compute electric fields induced in tissue by magnetic field exposures. Two types of coils are considered that simulate exposure to gradient switching fields during magnetic resonance imaging (MRI). These coils producing coronal (y axis) and axial (z axis) magnetic fields have previously been used in experiments with humans.The computed fields can, therefore, be directly compared to human response data. The computed electric fields in subcutaneous fat and skin corresponding to peripheral nerve stimulation (PNS) thresholds in humans in simulated MRI experiments range from 3.8 to 5.8 V/m for the fields exceeded in 0.5% of tissue volume (skin and fat of the torso). The threshold depends on coil type and position along the body, and on the anatomy and resolution of the human body model. The computed values are in agreement with previously established thresholds for neural stimulation.     

头盔式动态可变多通道经颅磁刺激线圈的设计

为了实现真正意义上的动态可变多通道经颅磁刺激(TMS),首次提出了头盔式网状线圈的设计理念。基于该理念设计的TMS 线圈系统,可以在全头范围内实现多通道经颅磁刺激,而且在线圈定位、分辨率等方面得到极大改善,同时还可以实现刺激部位、面积、方式和强度的实时动态可变性。建立了人体头颅电磁模型来模拟TMS 线圈产生的诱导电流分布,同时还对线圈产生的诱导磁场分布进行了实际测量,模拟与实测结果均与理论值相符,证明了该设计的有效性与可行性。     

双注电子枪中最小二乘法拟合磁场的研究

用粒子仿真软件EGUN和MAGIC仿真电子枪时,需设置一组线圈来拟合磁控注入电子枪的磁场.为了提高设计效率,采用最小二乘法计算线圈参数,拟合电子枪磁场,计算结果用于34GHz双注磁控注入电子枪的仿真中,仿真结果表明:最小二乘法能够直接计算出拟合磁场的线圈组合,提高设计电子枪的效率;仿真的双注磁控注入电子枪电子速度零散小,横纵速度比适中,满足回旋管对电子枪的要求.     

冷原子干涉仪中二维磁光阱线圈的优化设计

大通量冷原子源是实现高精度冷原子干涉仪的关键技术之一。为获得大通量冷原子源,通常采用二维磁光阱(2D-MOT)和三维磁光阱(3D-MOT)的级联结构,其中2D-MOT的磁场分布是影响其性能的重要因素。通过数学建模及有限元分析,对2D-MOT中不同构造(长方形、跑道形、马鞍形)的反亥姆霍兹线圈进行数值计算,分析了不同构造线圈的磁场分布及因在制造与装配过程中产生的偏心、线圈不对称、平行度及内径不对称误差造成的磁场零点漂移和磁场梯度变化。分析结果表明,在偏心误差C1.14 mm,线圈不对称误差I0.016 A,平行度误差1.02时,马鞍形线圈产生的磁场梯度更有利于制备大通量冷原子源。该结果为冷原子干涉仪2D-MOT的磁场系统设计和加工提供了理论指导。     

Electromagnetic field exposure system for the study of possibleanti-cancer activity

The characteristics of a static and extremely low frequency (ELF) magnetic fields (H-field) exposure system are analyzed. The system has been successfully used in a series of animal experiments devoted to the study of a new potential application of electromagnetism in cancer therapy. The characterization of this exposure system contributes to the improvement needed in the understanding of the role played by the various exposure parameters such as field intensity and field components (static, ELF, or a combination thereof) in the induction of the observed anti-tumor efficacy. This knowledge is important for extrapolating exposure conditions from animals to humans. The exposure system provides static and ELF H-field with an intensity in the kA/m range. The system allows six animals to be treated simultaneously with almost the same total (static + ELF) H-field intensity, but with different static and ELF components and, consequently, with different induced electric field levels and currents. The H-field uniformity experienced by each mouse is 12.4%     

Improving the homogeneity of the magnetic field in the magnetic search coil technique

The magnetic search coil technique is used to obtain accurate eye-movement measurements. For the data analysis it must be assumed that the magnetic field does not change over time (apart from the required modulation). To comply with this assumption either no translational movements of the eye coil(s) are allowed or the magnetic field has to be perfectly homogeneous. Both are normally not the case, i.e., measurement errors occur. These errors can be minimized by keeping the magnetic field as homogeneous as possible. Larger field coils are typically chosen to achieve this aim. However, sometimes the experimental setup imposes limitations on the size of the configuration. We present a method for improving the homogeneity of the magnetic field by adding supplementary field coils without changing the size of the configuration.     

大型疏绕螺线圈组磁场的仿真与测试

为解决低频强磁场模拟试验设备中磁场发生线圈为一大型疏绕螺线圈组,其磁场分布无法利用现有的适用于密绕情形公式进行计算的实际问题,采用Ansys仿真对其磁感应强度及其均匀性进行了计算和分析,并结合试验测试进行了验证。研究结果表明,低频强磁场模拟试验系统为相关技术指标和磁场受试空间的确定提供了直接依据。     

行波管；集成极靴式磁聚焦系统；磁感应强度；数值模拟

集成极靴式互作用系统在高频段行波管中有着巨大的应用潜力,而在其设计和应用过程中,最大限度地克服横 向磁场是一个十分重要的问题。介绍了集成极靴式互作用系统的结构单元、工作原理和比较优势;基于一段特定几何尺 寸的集成极靴式互作用系统,先定性分析了影响其磁场分布的关键参量,然后利用CST 静磁工作室详细研究了各个参量 的变化与其磁场分布的相互关系。计算结果不仅可以进一步加深对矩形磁钢磁场分布的认识,也为集成极靴式互作用系 统的在高频段行波管中的应用奠定了基础。     

Minimum Stored Energy High-Field MRI Superconducting Magnets

A globally optimum minimum stored energy optimization strategy is implemented to design actively shielded superconducting magnet configurations used in high-field applications. The current density map is first obtained and used as a foundation for the magnet configurations by placing coils at current density local extremities. Optimized current density maps based on the stored energy formulation along with final magnet arrangements are provided to illustrate the findings. In this work, the focus was on compact superconducting magnets as measured by physical size and system footprint for given magnetic field properties inside the imaging region. The process of obtaining the current density maps proposed here over the given magnet domain, where superconducting coils are laid out, suggests that peak current densities occur around the perimeter of the domain, where in the most compact designs, with the domain length less than 1 m, the current direction alternates amongst adjacent coils. To reduce the peak magnetic field to acceptable levels on the superconductors in high-field designs, the size of the magnet domain is made larger, to the extent that the current densities no longer alternate between coils.      

Superconducting magnet system of the CMD-2 detector

This paper describes the superconducting magnet system of the CMD-2 detector. The magnetic field is provided by the main and two compensating superconducting solenoids. The unique features of this system are the solenoids protection method utilizing a distributed resistance along the coil and the power supply being a fluxpump type. The main solenoid produces a field up to 1.2 T in a volume of φ 0.71 m×0.9 m. Its radiation thickness and E/M ratio are 0.38 X₀ and 5 kJ/kg, respectively. NbTi/Cu superconducting cables without any insulation and an aluminum stabilizer were used for the design of solenoid coils. The superconducting cable was wound in a stainless-steel bobbin and soldered by a PbSn alloy. The cooling bath provides a temperature of 4.2 K in the system. The superconducting magnet system of the CMD-2 detector was manufactured and tested in 1989     

Flux trapping in a ring-shaped YBCO bulk by pulsed fieldmagnetization

A pulsed magnetic field can be applied using small coils to generate a strong magnetic field for the magnetization of the high-Tc superconductors (HTS) to be used as quasi-permanent magnets in flywheels and motors. The dynamic electromagnetic behavior of two melt-processed ring-shaped Y-Ba-Cu-O bulks using the pulsed field magnetization (PFM) process has been experimentally investigated and analyzed. The flux trapped in the bulk by PFM process was compared to the flux trapped by field cooling process. Both cases then have been analyzed with a numerical model based on the finite-element method (FEM). The power-law model was utilized to relate the electric field to the current density inside the superconductor. The dependence of the critical current density on the magnetic field density was taken into account. Measured and calculated results are compared and discussed     

一种新型磁场MWECR-CVD和氢化非晶硅薄膜制备

为了简化多电磁线圈 MWECR- CVD装置 ,提出将单个电磁线圈和一个永磁体单元组合 ,以形成所需的新型磁场 .这一磁场可使等离子体集聚于样片台上方 ,显著提高了等离子体的能量密度 .应用这种新型磁场的 MWE-CR- CVD装置沉积氢化非晶硅薄膜 ,与采用单电磁线圈或双电磁线圈时相比 ,薄膜沉积速度大幅度提高 ,沉积速度达到采用传统 RF- PECVD装置时的数倍至十倍     

Performance of large-size superconducting coil in 0.21T MRI system

A high-temperature superconductor (HTS) was used on magnetic resonance imaging (MRI) receiver coils to improve image quality because of its intrinsic low electrical resistivity. Typical HTS coils are surface coils made of HTS thin-film wafers. Their applications are severely limited by the field of view (FOV) of the surface coil configuration, and the improvement in image quality by HTS coil is also reduced as the ratio of sample noise to coil noise increases. Therefore, previous HTS coils are usually used to image small in vitro samples, small animals, or peripheral human anatomies. We used large-size HTS coils (2.5-, 3.5-, and 5.5-in mean diameter) to enhance the FOV and we evaluated their performance through phantom and human MR images. Comparisons were made among HTS surface coils, copper surface coils, and cool copper surface coils in terms of the signal-to-noise ratio (SNR) and sensitivity profile of the images. A theoretical model prediction was also used to compare against the experimental result. We then selected several human body parts, including the wrist, feet, and head, to illustrate the advantage of HTS coil over copper coil when used in human imaging. The results show an SNR gain of 200% for 5.5-in HTS coil versus same size copper coils, while for 2.5- and 3.5-in coils it is 250%. We also address the various factors that affect the performance of large size HTS coils, including the coil-to-sample spacing due to cryogenic probe and the coil-loading effect.     

An inverse design of an open,head/neck RF coil for MRI

Radio-frequency (RF) coils are a necessary component of magnetic resonance imaging (MRI) systems. When used in transmit operation, they act to generate a homogeneous RF magnetic field within a volume of interest and when in receive operation, they act to receive the nuclear magnetic resonance signal from the RF-excited specimen. This paper outlines a procedure for the design of open RF coils using the time-harmonic inverse method. This method entails the calculation of an ideal current density on a multipaned planar surface that would generate a specified magnetic field within the volume of interest. Because of the averaging effect of the regularization technique in the matrix solution, the specified magnetic field is shaped within an iterative procedure until the generated magnetic field matches the desired magnetic field. The stream-function technique is used to ascertain conductor positions and a method of moments package is then used to finalize the design. An open head/neck coil was designed to operate in a clinical 2T MRI system and the presented results prove the efficacy of this design methodology.     

迴旋管永磁聚焦系统设计

迴旋管实现永磁包装,迄今尚未见有文献报道。本文提出采用一种适合于迴旋管工作的双均习区径向磁路系统作为永磁聚焦方案,并利用计算机进行了研究,通过设计计算,选用磁能积(BH(max)为20 MGOe的钐钴磁钢。为了调整磁场,在双均匀区添加了一些小电磁线包,它们改变磁场的范围约为5％。 通过计算表明,建立一个8 mm二次谐波迴旋管所需的65007000Gs强磁场系统,约需钐钴磁钢4050kg。这对于研制 8 mm二次谐波永磁聚焦迴旋管以及近厘米波段迴旋管是很吸引人的。本文最后还对提高磁路效率、扩大均匀区等问题进行了简单的讨论。     

Imaging system based on electromagnetic tomography (EMT)

A novel non-contacting instrumentation system for obtaining cross-sectional images of conductive and ferrous material is described. The image space is energised with a parallel magnetic field and the distortion created by objects is detected by sensing coils. The backprojection method is used for reconstruction. Initial results are presented.<>