A Semantic Service Discovery Network for Large‐Scale Ubiquitous Computing Environments

This paper presents an efficient semantic service discovery scheme called UbiSearch for a large‐scale ubiquitous computing environment. A semantic service discovery network in the semantic vector space is proposed where services that are semantically close to each other are mapped to nearby positions so that the similar services are registered in a cluster of resolvers. Using this mapping technique, the search space for a query is efficiently confined within a minimized cluster region while maintaining high accuracy in comparison to the centralized scheme. The proposed semantic service discovery network provides a number of novel features to evenly distribute service indexes to the resolvers and reduce the number of resolvers to visit. Our simulation study shows that UbiSearch provides good semantic searchability as compared to the centralized indexing system. At the same time, it supports scalable semantic queries with low communication overhead, balanced load distribution among resolvers for service registration and query processing, and personalized semantic matching.     

二维耦合光学摆镜伺服控制系统

二维耦合光学摆镜是扫描式星载红外光学系统的关键运动部件,其运动特性对伺服系统提出了高精度位置控制与运动解耦的特殊要求。在建模与仿真分析的基础上,提出了一种新的耦合偏移补偿与分割步进的解耦策略,采用位置环与速度环双闭环的PID控制算法,使用有限转角力矩电机和高精度旋转变压器作为执行与测量元件,以DSP为核心构建了二维耦合光学摆镜伺服控制系统。实验结果表明:该方法设计的控制系统二维运动解耦正确,控制精度高,响应时间短,动态特性好且超调小,可广泛应用于高精度摆动扫描控制系统的研究领域,具有很好的工程应用前景。     

The spinning Astrid-2 satellite used for modeling the Earth's mainmagnetic field

The Swedish micro-satellite Astrid-2 was successfully launched into a near polar orbit in December 1998. Despite the fact that the primary science mission was auroral research, the magnetic instrument was designed to accomplish high-resolution and high-precision vector field magnetic measurements, and therefore mapping of the Earth's magnetic field was possible. The spacecraft spins about a highly stable axis in space. This fact and the globally distributed data make the magnetic measurements well suited for the estimate of a magnetic field model at the spacecraft altitude (about 1000 km). This paper describes the initial analysis of the Astrid-2 magnetic data. As a result of the study of a single day (February 7, 1999), magnetically fairly quiet, it was possible to in-flight adjust the calibration of the magnetometer and find a magnetic field model fitting the scalar component of the measurements to better than 5 nT_rms for latitudes equatorward of 50°. Several methods for field modeling are discussed in this paper under the assumption that the direction of the spin axis in inertial space is nearly constant, and this assumption is corroborated by the observations. The approximate inertial orientation of the magnetometer could then be determined simultaneously with the instrument intrinsic calibration and the estimate of main field model coefficients     

Positioning performance and straightness error compensation of the magnetic levitation stage supported by the linear magnetic bearing

This paper reports high-precision motion control at the target position and the offline compensation of the straightness error occurring during the motion of the magnetically levitated stage supported by the linear magnetic bearing. The linear magnetic bearing is composed of electromagnets and sensors in the same module to enable easy maintenance and to reduce the machining error, and the conventional linear quadratic Gaussian control is adopted for the motion control of the stage. The test results show that the stage can compensate the straightness error precisely, so that it is expected that this stage can be applied to high-precision linear motion applications.     

Industrial Applications of Hall-Effect Devices

The Hall effect can be employed to obtain an output proportional to the product of the current through the element and the field cutting through it. A qualitative explanation aids in the visualization of the phenomena. There are several semiconductor materials that may be selected to emphasize a particular characteristic such as power transfer, temperature stability, etc. Maximum efficiency and improvement of dynamic range can be realized if care is taken in the assembly of the element-magnet structure and appropriate compensation techniques are employed. Since the two inputs are current and flux density and these may result from a variety of sources, the application becomes multitudinous. This creates an entirely new family of transducers that in many cases are improved in size, response and cost over conventional devices. The following applications are described: wattmeter, varmeter, gaussmeter, clip-on ammeter, resolvers and synchros, and magnetic tape readers.     

A novel Variable-Reluctance Resolver proposal and its performance analysis under healthy and eccentric cases

A Variable-Reluctance resolver (VR-Resolver) with a novel structure is proposed in this paper as an absolute position sensor, where two possible structures are analyzed. The signals and excitation windings are located on the stator. Hence the slip rings are eliminated in the rotor. The rotor is considered by slot/teeth configuration so the rotor is shaped in a simple variable reluctance structure with a low sensitivity to the manufacturing tolerance. The excitation winding is wound in toroidal configuration that leads to having a smaller fill factor as well as turns can be considered for the windings. Maximum position error (MPE) is evaluated for the proposed resolvers in both healthy and eccentric cases. Therefore, the resolvers performance and their sensitivity to the eccentricity fault are evaluated. A flexible Magnetic Equivalent Circuit (MEC) with adjustable accuracy is used for modeling thanks to its capability and shorter processing time compared to the Finite-Element Method (FEM), where different cases are analyzed by a unique MEC model. Finally, comparison between the MEC and FEM-based results as well as experimental tests are presented to show effeteness of the proposed resolver as an accurate absolute position sensor for industries applications.     

基于磁流包覆冷却拉锥全光纤磁场传感器特性研究

为提高光纤传感器磁场检测中的敏感度,进一步实现弱磁场环境中的高精度场强勘测,提出一种基于磁流包覆与冷却拉锥透射式全光纤高灵敏磁场传感器,拉锥过程采用间歇式停顿冷却技术,可更加便捷获得高质量干涉谱,减缓光子晶体光纤空气孔塌缩,制作工艺简单,具有可操纵性强、灵敏度高、损耗小等优势,实现了高灵敏磁场环境实时在线检测,并对传感器的变温影响进行了讨论。实验结果表明,光子晶体光纤的拉锥长度为5.5mm、腰椎直径为75μm时,可得到良好的干涉光谱,在0~78 Oe(1 Oe■79.578A·m-1)磁场范围内,灵敏度达95pm/Oe,线性拟合度为98.31%。     

An Electromagnetic Near-Field Sensor for Simultaneous Electric and Magnetic-Field Measurements

This paper describes the theory of a single sensor to perform simultaneous electric and magnetic near-field measurements. The theory indicates that it is possible to measure the magnetic-loop and electricdipole currents using a loop antenna terminated with identical loads at two diametrically opposite points. The theory also indicates that it is possible to choose an ideal load impedance for achieving equal electric and magnetic-field responses of the loop. Preliminary experiments have been performed using a plane-wave field to verify these results.     

高精度激光器电流驱动与交流温控系统设计

半导体激光器作为原子磁强计的重要组成部分,其波长和功率主要由电流和温度决定,而传统的直流温控系统会对磁强计产生磁场干扰。针对高精度电流控制、温度控制和磁场干扰问题,设计了一种激光器恒流源驱动和交流控温系统。首先,设计基于功放的高精度激光器恒流源驱动系统;然后,设计交流温度调制解调检测和交流加热驱动系统;最后,采用STM32控制器、高精度AD采集和DA输出结合温度模糊自适应PID控制算法进行高精度温度控制。实验结果表明:在42℃温度下控制精度为0.005℃,在32 mA电流下稳定度为0.5 A,为激光器光功率和波长稳定性奠定基础。     

Numerical method for calculation of complex dielectric permittivity

The letter describes the numerical method used at Istituto di Elettronica dell'Università di Pisa, Italy, for processing experimental data obtained in measuring complex dielectric permittivity by dielectrometer. The letter shows that it is possible to obtain high-precision results without using Von Hippel tables.     

Magnetic control system targeted for capsule endoscopic operations in the stomach--design, fabrication, and in vitro and ex vivo evaluations

This paper presents a novel solution of a hand-held external controller to a miniaturized capsule endoscope in the gastrointestinal (GI) tract. Traditional capsule endoscopes move passively by peristaltic wave generated in the GI tract and the gravity, which makes it impossible for endoscopists to manipulate the capsule endoscope to the diagnostic disease areas. In this study, the main objective is to present an endoscopic capsule and a magnetic field navigator (MFN) that allows endoscopists to remotely control the locomotion and viewing angle of an endoscopic capsule. The attractive merits of this study are that the maneuvering of the endoscopic capsule can be achieved by the external MFN with effectiveness, low cost, and operation safety, both from a theoretical and an experimental point of view. In order to study the magnetic interactions between the endoscopic capsule and the external MFN, a magnetic-analysis model is established for computer-based finite-element simulations. In addition, experiments are conducted to show the control effectiveness of the MFN to the endoscopic capsule. Finally, several prototype endoscopic capsules and a prototype MFN are fabricated, and their actual capabilities are experimentally assessed via in vitro and ex vivo tests using a stomach model and a resected porcine stomach, respectively. Both in vitro and ex vivo test results demonstrate great potential and practicability of achieving high-precision rotation and controllable movement of the capsule using the developed MFN.     

Novel encoder for switching angle control of SRM

In a switched reluctance motor drive, it is important to synchronize the stator phase excitation with rotor position because the position of the rotor is an essential information. Although high-resolution optical encoders or resolvers are used to provide precise position information, these sensors are expensive. Moreover, in a high-speed region, switching angles are fluctuated back and forth out of the preset value, which is caused by the sampling period of the microprocessor. In this paper, a low-cost analog encoder suitable for practical applications is proposed. In addition, the control algorithm to generate switching signals using a simple digital logic is presented. The validity of the proposed analog encoder with a proper logic controller is verified from the experiments.     

旋转变压器正交误差的励磁补偿

文中主要讨论了旋转变压器在鉴相工作方式下因正余弦绕组空间位置不正交和励磁电源输出信号相位不正变而引起的测量误差的表现形式，并据此提出了一种采用励磁电源正、余弦输出信号的相位微调的方法来补偿正余弦绕组因空间位正不正变引起的误差和励磁信号相位不正交引起的测量误差。应用的实践和理论分析均证明该方法对补偿上述误差是行之有效的。     

提高高精度光纤陀螺磁场适应性的方法研究

光纤环在磁场中产生磁致非互异性误差,成为制约高精度干涉型光纤陀螺（以下简称高精度光纤陀螺）应用的主要因素之一,而误差与磁场强度、光纤扭转率有关。由于光纤扭转导致的光纤环磁场灵敏度达到10 (°)·h?1·Gs?1以上,即使采用坡莫合金对磁场屏蔽,屏蔽效能仅能达到30 dB左右,难以满足高精度光纤陀螺的应用需求。文中通过等效电路模型和有限元仿真分析了屏蔽材料连接缝隙对屏蔽效能的影响,通过公式计算了扭转率对磁场灵敏度的影响。根据分析,提出了将屏蔽材料由螺钉连接改为激光焊接并对光纤进行退扭的改进方法。通过光纤退扭,光纤环磁场灵敏度降低了89.3%;通过对连接缝隙激光焊接,屏蔽效能由 31 dB 提高到 64 dB以上,磁场灵敏度由 0.026 5 (°)·h?1·Gs?1 降低到了 0.000 4 (°)·h?1·Gs?1以下,且变温环境下陀螺零偏稳定性提高了7.5%以上。改进措施能够提高光纤环在磁场和温度环境下的精度,满足高精度光纤陀螺性能要求。     

Influence of ferrimagnetic resonance on conversion of electromagnetic energy into mechanical one

In this paper it is obtained in zero approximation the algorithm of calculation of the force of electromagnetic wave propagation in rectangular waveguide applied to the ferrite sphere, placed into constant magnetic field by the method of physical modeling. It is researched the dependence of the force on a value of magnetic field intensity near ferromagnetic resonance. Theoretical results of the calculations were compared with experimental ones. At the resonance electromagnetic field with the power of 10W and the wave length of 3.2 cm influences on ferrite sphere with diameter of 3.55mmwith a force of 6 ± 0.5 µN. This force in enough for rotation of the suspension system of the reference ponderomotive wattmeter, fixed attached by means of braces or kerns. It allows to develop high-precision microwave wattmeters with enough mechanic strength for industrial application.     

国家级弱磁实验室高精度中央空调设计

弱磁计量实验室对磁环境、温度控制精度均有严格要求.普通恒温恒湿空调器虽然能达到温度控制精度要求,但由于含铁磁物质,不能在该环境下使用;常规中央空调系统虽然可以满足磁环境要求,但难以满足温度波动小于0.2℃/h的温控精度要求.本项目设计采用中央空调加分区控温的方式较好地解决了该难题,设计中采用高效能热隔离、小温差送风、孔...     

In situ runout identification in active magnetic bearing system by extended influence coefficient method

In this paper, an efficient, yet easy-to-use, in-situ runout identification scheme, based on the extended influence coefficient method, is presented for active magnetic bearing (AMB) systems. It is shown experimentally that the proposed scheme successfully identifies and eliminates the troublesome runout of a well-balanced AMB system in the laboratory, so that a high-precision spindle system can be achieved, while it is in operation.     

Turn-Coupling in Thick-Film Integrated Magnetic Components for Power Converters

Thick-film technology constitutes an alternative to develop low-power integrated magnetic components. This paper explores into the possibilities presented by such technology and proposes new conductor arrangements that allow turn-coupling to be obtained in thick-film magnetic structures. The benefit of having such a coupling is twofold. On the one hand, it allows inductors to be integrated in even smaller volumes. On the other hand, it makes it possible to design flat power transformers using this integration technique. A complete design procedure of both, power inductors with turn-coupling and power transformers, is presented in this paper. A full characterization of these thick-film transformers is also given. Some experimental results are included as well so that the reader can validate the modeling proposed.      

Wavelet neural network control for induction motor drive using sliding-mode design technique

This paper addresses an adaptive observation system and a wavelet-neural-network (WNN) control system for achieving the favorable decoupling control and high-precision position tracking performance of an induction motor (IM) drive. First, an adaptive observation system with an inverse rotor time-constant observer is derived on the basis of model reference adaptive system theory to preserve the decoupling control characteristic of an indirect field-oriented IM drive. The adaptive observation system is implemented using a digital signal processor with a high sampling rate to make it possible to achieve good dynamics. Moreover, a WNN control system is developed via the principle of sliding-mode control to increase the robustness of the indirect field-oriented IM drive with the adaptive observation system for high-performance applications. In the WNN control system, a WNN is utilized to predict the uncertain system dynamics online to relax the requirement of uncertainty bound in the design of a traditional sliding-mode controller. In addition, the effectiveness of the proposed observation and control systems is verified by simulated and experimental results.     

基于STM32的物体姿态测量系统设计

采用JY-901高精度惯性导航模块来作为姿态检测的传感器,通过STM32单片机来对JY-901高精度惯性导航模块采集的数据进行处理[1],然后在TFTLCD液晶屏来实时显示出JY-901高精度惯性导航模块采集物体的姿态数据.这样可以直观的在TFTLCD液晶屏上动态观察物体的姿态信息.JY-901高精度惯性导航模块内部中运用了卡尔滤波算法对检测的数据进行了运算融合,提高了数据测量的精确度[2].