Quench analysis of a superconducting magnet with 98 coils connected in series

A novel insertion device for electron storage rings called the MAX-Wiggler has been constructed at MAX-lab. The MAX-Wiggler is a cold bore superconducting wiggler magnet with 47 3.5-T poles and a period length of 61 mm aimed for the production of X-rays at the 1.5-GeV electron storage ring MAX-II at MAX-lab. The MAX-Wiggler consists of 98 racetrack coils connected in series in the superconducting magnet and the total stored magnetic energy at the nominal maximum field strength of 3.5 T is 48 kJ. This paper describes the quench analysis of the magnet. Several protection schemes have been evaluated, such as an external dump resistor and safety switch or subdivision of the series of coils into sections with shunt resistors or silicon diodes in parallel to each group of coils in a section. It has been found that the most suitable protection scheme, in order to prevent the superconducting coils from getting overheated, is subdivision with a shunt path containing silicon diodes operating at liquid helium temperatures. The MAX-Wiggler has been commissioned and it has survived the quenches occurring during the initial training of the superconducting coils.     

码分多址系统中多用户检测算法的性能分析

多用户检测算法是码分多址系统中解决多址干扰的关键技术之一，近年来人们对此做了许多研究。现分析了几种典型的多用户检测算法的特性，给出了它们的性能特点。     

某火炮故障检测系统设计及精度问题研究

火炮故障检测系统检测范围有限和检测精度低是火炮故障诊断系统的两大缺陷,针对现有火炮检测系统检测精度低的问题,从电路设计、A/D采集电路设计以及液晶显示等方面分析了影响系统检测精度的主要因素,并提出了多种改善检测精度的方案。针对现有火炮检测系统检测范围有限的问题,提出了一个可对炮控箱、操纵台和瞄控箱、电源、开关以及电位旋钮等多位置发生的故障进行检测的火炮综合故障检测系统,并对该系统相关的硬件和软件进行了设计。测试实验表明,该系统功能完善,通用性好,改善系统检测精度的方案实用性强,对于提高我国的火炮故障检测水平具有积极的意义。     

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     

基于多传感器和Bi-LSTM的个性化跌倒检测研究

解决老年人发生意外跌倒却无法被及时发现与救治的问题.为提高跌倒检测的精确度与解决个性化适配问题,本文提出一种基于多传感器和Bi-LSTM神经网络的端云协同的个性化跌倒检测方案.该系统主要包括2方面,一方面是可穿戴设备设计与个体适配的实时跌倒检测算法的实现;另一方面是基于Bi-LSTM的云端个性化跌倒模型的构建.可穿戴设...     

A multiple circular path convolution neural network system for detection of mammographic masses

A multiple circular path convolution neural network (MCPCNN) architecture specifically designed for the analysis of tumor and tumor-like structures has been constructed. We first divided each suspected tumor area into sectors and computed the defined mass features for each sector independently. These sector features were used on the input layer and were coordinated by convolution kernels of different sizes that propagated signals to the second layer in the neural network system. The convolution kernels were trained, as required, by presenting the training cases to the neural network. In this study, randomly selected mammograms were processed by a dual morphological enhancement technique. Radiodense areas were isolated and were delineated using a region growing algorithm. The boundary of each region of interest was then divided into 36 sectors using 36 equi-angular dividers radiated from the center of the region. A total of 144 Breast Imaging-Reporting and Data System-based features (i.e., four features per sector for 36 sectors) were computed as input values for the evaluation of this newly invented neural network system. The overall performance was 0.78-0.80 for the areas (Az) under the receiver operating characteristic curves using the conventional feed-forward neural network in the detection of mammographic masses. The performance was markedly improved with Az values ranging from 0.84 to 0.89 using the MCPCNN. This paper does not intend to claim the best mass detection system. Instead it reports a potentially better neural network structure for analyzing a set of the mass features defined by an investigator.     

Single-port-access surgery with a novel magnet camera system

In this paper, we designed, built, and tested a novel single-port access laparoscopic surgery (SPA) specific camera system. This device (magnet camera) integrates a light source and video camera into a small, inexpensive, portable package that does not compete for space with the surgical tools during SPA. The device is inserted through a 26-mm incision in the umbilicus, followed by the SPA port, which is used to maintain an insufflation seal and support the insertion of additional tools. The camera, now in vivo, remains separate from the SPA port, thereby removing the need for a dedicated laparoscope, and, thus, allowing for an overall reduction in SPA port size or the use of a third tool through the insertion port regularly reserved for the traditional laparoscope. The SPA camera is mounted to the abdominal ceiling using one of the two methods: fixation to the SPA port through the use of a rigid ring and cantilever bar, or by an external magnetic handle. The purpose of the magnet camera system is to improve SPA by: 1) eliminating the laparoscope SPA channel; 2) increasing the field of view through enhanced camera system mobility; and 3) reducing interference between the camera system and the surgical tools at the port, both in vivo and ex vivo.     

A superconducting magnet system for free-electron cyclotron maser

A superconducting magnet system for free-electron cyclotron maser is developed. This system includes a main superconducting magnet, a gradient superconducting magnet, a normal magnet, a cryostat and some accessories. The designed magnet system has the advantages of having a small size, high stable magnetic field and suitable field profile. It is very suitable for a 4mm wavelength free-electron cyclotron maser. The design and some experimental results are given.     

永磁同步电机伺服系统的模糊控制

为了克服参数的不确定性,提高永磁同步电机伺服系统的快速跟踪能力,文中提出了一种自校正模糊控制器。该自校正模糊控制器与传统控制器相比,具有在线计算简单、减小稳态误差的优点。同时将其应用于永磁同步电机伺服系统的速度控制,证明了该模糊控制器的优越性。     

光电瞄具多光轴平行性检测系统的设计与研究

为了精准地测量光电瞄具多光轴的平行性,采用大口径离轴抛物面反射镜平行光管的多光轴检测方法进行了理论分析,并设计了完整的测量系统(包括光学成像系统、控制系统、图像采集与处理系统)。该系统采用离散余弦变换系数作为评价标准,实现了高精度的自动对焦;采用大口径离轴抛物面反射镜满足不同型号瞄具的测量,实现了可见光、近红外和远红外3种光学系统的光轴平行性的自动检测。结合一种光电瞄具成品进行了实际测试,当光轴之间偏差角为0.04mrad~0.08mrad时,相对误差在13%以内,此范围可认为是系统检测角度的下限。结果表明,该系统减小了人为读数等主观原因造成的误差,通用性强、检测效率高,精度满足需求。     

Pulsed magnet system considerations for repetitive operation ofhigh-power magnetrons

A tradeoff evaluations has been performed to specify a compact, low-loss pulsed electromagnet system for a repetition rate application of high-power magnetrons. The required magnetic field is 5 to 15 kG with 1% uniformity over the magnetron volume, and the pulse repetition rate is on the order of 5 pps. To drive the magnets, a recirculating driver scheme which transfers energy back and forth between two capacitor banks has been identified as a variable low-power-loss approach. The circuit comprises a 10-kW switching power supply, a high-voltage switch network, 400-kJ capacitor banks, and magnet coils. Several recirculating drive systems operating in the voltage range of 10 to 50 kV and output currents with a pulse duration of ≈10 ms are compared relative to their power losses, system size and weight, and their limitations at high pulse repetition rates     

Fault detection with multiple observers

There is a pressing need for network management systems capable of handling faults. The use of a set of independent observers to detect faults in communication systems that are modeled by finite-state machines is proposed. An algorithm for constructing these observers and a fast real-time fault detection mechanism used by each observer are given. Since these observers run in parallel and independently, one immediate benefit is that of graceful degradation-one failed observer will not cause collapse of the fault management system. In addition, each observer has a simpler structure than the original system and can be operated at higher speed. This approach has the potential to be incorporated into the fault management system for a high-speed communication system     

基于小波变换的电磁线绕包图像边缘检测方法

基于机器视觉的电磁线绕包质量检测的关键技术是提取绕包图像的边缘,传统的边缘检测算子存在着定位精度不高或对噪声敏感的问题。为满足不断提高的工业要求,提出一种基于小波变换的电磁线绕包图像的边缘检测方法。首先利用小波函数求出图像的梯度模极大值,然后经过自适应阈值和非极大值抑制去除伪边缘点,归一化处理后得到电磁线绕包边缘图像。与Canny算法比较,该方法能够有效去除噪声影响且边缘提取连续准确,具有较好的适应性和鲁棒性。     

永磁同步电机直接转矩控制系统的仿真研究

文章分析了永磁同步电机直接转矩控制的原理,阐述传统直接转矩控制系统转矩脉动的缺点,本文将空间矢量脉宽调制技术引入永磁同步电机的直接转矩控制系统中,利用空间矢量的调制过程,可在相同的系统硬件条件下得到更多的、连续的电压空间矢量,进而得到对电机更准确的控制。仿真结果表明,该方案既保持了直接转矩控制快速动态响应,又减小了电机转矩的脉动。     

Superconducting rectifier fluxpump for magnet system of the CMD-2detector

A superconducting rectifier fluxpump has been used for the dc power supply of the magnet system of the CMD-2 detector on the VEPP-2M collider at the Budker Institute of Nuclear Physics in Russia since 1989. The fluxpump provides a complete pumping cycle: charging the magnet system, stabilization of the magnetic field, and discharging. The fluxpump consists of an air-core current step-up superconducting transformer and two groups of thermally controlled superconducting switches arranged as a fullwave rectifier. Critical output current during the test was 5.4 kA. The accuracy of the field stabilization provided by the fluxpump is 2.5·10^-5. The fluxpump has exhibited reliable and safe operation during its entire history of use     

An advanced permanent magnet motor drive system for battery-poweredelectric vehicles

Availability of high-energy neodymium-iron-boron (Nd-Fe-B) permanent magnet (PM) material has focused attention on the use of the PM synchronous motor (PMSM) drive for electric vehicles (EVs). A new Nd-Fe-B PMSM is proposed for the drive system, which possesses high power density and high efficiency, resulting in greater energy and space savings. The design and optimization of the motor employs finite element analysis and computer graphics. Increasingly, a new PWM inverter algorithm is developed for the drive system, which can handle the nonconstant battery voltage source. An efficiency optimizing control is adopted to further improve the energy utilization of the drive system. Both the control strategy and the PWM generation are implemented in a single-chip microcontroller. As a result, the motor drive achieves high power density, high efficiency, and compactness. A prototype of the 3.2 kW battery-powered drive system has been designed and built for an experimental mini-EV     

基于直驱永磁同步风力发电系统的控制器设计与研究

直驱永磁同步风力发电系统采用了背靠背双PWM变流器,基于解耦控制策略的PI控制器用于实现对系统机侧和的网侧的有效控制.工程上PI参数多采用试验加试凑的方式,造成大量人力浪费.本文对直驱永磁同步风力发电系统进行数学建模,并提出一种基于粒子群优化算法的PI参数优化,在风速突变条件下对系统仿真分析,结果表明利用粒子群优化算法的PI控制参数能较好的拟合真实值,动态响应快.进而验证了该方法在工程应用中的可行性和有效性.     

一种改进的多符号检测算法

针对再入遥测环境下中信号相位容易受噪声影响,导致传统MSD过程中最大似然值被误判的问题,研究一种改进的多符号检测算法：每次MSD运算较前一次MSD运算有N-2个码元的重叠,即每次滑动两个码元长度的码元滑动策略。仿真和测试结果验证了改进算法的有效性。     

Disturbance rejection control method for permanent magnet synchronous motor speed-regulation system

The speed-regulation problem for permanent magnet synchronous motor (PMSM) system is studied in this paper. To guarantee the disturbance rejection ability of the closed loop system, most of the existing advanced control methods develop disturbance rejection control laws only for speed loop. To further improve the disturbance rejection ability, a control scheme which employs disturbance rejection control laws for not only speed loop but also the q-axis current loop, is developed here. Considering the dynamics of q-axis current, the coupling between rotor speed and d-axis current as well as the back electromotive force are regarded as lumped disturbances for the q-axis current loop, which are estimated by introducing an extended state observer (ESO). Thus a composite control law consisting of proportional feedback and disturbance feedforward compensation is developed to control the q-axis current. Simulation and experiment comparisons are presented to verify the effectiveness of the proposed method.