一种光泵磁力仪自动捕获跟踪系统的设计

采用分立的改进型VCO设计了一种光泵磁力仪的跟踪锁定环路,并利用后继的中央控制器来完成辅助捕获功能。实验表明环路能获得1Hz的跟踪精度,失锁后的重新捕获时间小于5s。相比于在系统中应用手动电调或专门的辅助捕获电路,该跟踪系统充分利用了后继中央控制器的富余资源,减小了设备的复杂性和体积;加之运用廉价的分立元件构建VCO单元,进一步降低了成本,因此具有良好的应用前景。     

Magnetic and structural properties of amorphous/nanocrystalline Fe42Ni28Zr8Ta2B10C10 soft magnetic alloy produced by mechanical alloying

Magnetic behavior, microstructural evolution, and amorphization studies of Fe₄₂Ni₂₈Zr₈Ta₂B₁₀C₁₀ alloy, synthetized by mechanical alloying, were investigated. The non-equilibrium microstructure originated from a grain size reduction to about 2.5 nm indicated by X-ray diffraction and the introduction of internal strain up to 3.8%. The results showed that as the milling time increased the amorphous phase became dominant and reached about 92 wt.% at 176 h. The magnetic measurements which were obtained by vibrating sample magnetometer, showed an increase in saturation magnetization up to 12 h and then a decrease until 66 h followed by a slow increase. Simultaneously, the coercivity increased, decreased and finally reached a constant level of about 24 Oe. The value of coercivity obtained in the present study is less than the values reported for the widely investigated mechanically alloyed Fe–Ni–Zr–B alloys, which shows this alloy is a very good soft magnet.     

Evaluation of the electromagnetic characteristics of type 316L stainless steel welds from the viewpoint of eddy current inspections

This study evaluated the electromagnetic characteristics of austenitic stainless steel welds from the viewpoint of eddy current testing. Seven welded plate specimens, which were welded using JIS Z3221:2010 YS316L welding metals, were prepared. Two welding metals and several welding conditions were adopted to discuss the generality. The results of eddy current examination of the specimens using three different types of eddy current probes, that is, an absolute pancake probe, a differential plus-point probe, and a uniform eddy current probe, confirmed that the welds cause a large noise especially when the absolute pancake probe was used. The analysis of the signals through finite element simulations revealed that the magnetic property of the welds is not negligible from the viewpoint of eddy current testing. Complementary experiments were conducted using a vibrating sample magnetometer to validate the results.     

Cryogenic magnetometer research at Twente University of Technology

In 1982 we started the project ‘Cryogenic Magnetometers’ with the aim to develop SQUID-magnetometers appropriate to a large variety of applications. The first system we developed is a SQUID-magnetometer with an open-ended horizontal access at room temperature. The measuring space inside the pick-up coils is easy accessible and the magnetization (remanent or induced) can be measured of materials in a static position or transported through the access.Further, systems have been developed with the pick-up coil set outside the cryostat, in order to arrive at a flexible system with which the object under investigation can be approached as close as possible. Another part of the project is the optimization of magnetometers with respect to the cryogenic system in order to develop cryogenic magnetometer systems with a very long time between helium refills. The present status of these three research subjects is briefly described.     

一种基于椭球约束和Procrustes分析的磁矢量传感器校正算法

磁矢量传感器在测量过程中将受到载体及其他工作部件的干扰,为保证和提高测量精度,提出了基于椭球约束和Procrustes分析的磁矢量传感器校正算法。在分析误差来源并进行分类的基础上,建立了磁矢量传感器误差模型,通过椭球约束法和正交Procrustes分析获得了由测量值到真值的映射关系,实现磁矢量传感器的校正。仿真结果表明,该校正方法能有效地完成磁矢量传感器的校正,而且方法简单、易于实现,在较大噪声水平下也能较好的完成校正工作。     

Nondestructive evaluation of ferromagnetic materials by a “magnetometer like” experimental arrangement

The paper presents experimental results regarding the influence of mechanical stresses and thermal treatments on the Barkhausen noise and magnetization characteristic of MolyPermalloy and MuMetal ferromagnetic samples. The samples are different in stress magnitude and localization and in their thermal history. The level of Barkhausen noise and the changes in magnetization characteristic are estimated by measuring the sensitivity and transduction gain of magnetometer like coils configurations which employ the studied ferromagnetic samples as their nonlinear ferromagnetic cores. The present method is unique in the sense that the two factors (one factor is related to the internal magnetic noise, and the other one is related to the form of the magnetic characteristic) are obtained by employing a single relatively simple experimental arrangement. Various types of stresses, which are different in magnitude and localization, become distinguishable one from the other, when considering their differential effects on the two factors. Several possible experimental arrangements are shown.     

井下磁力计数据采集系统的研制

根据用于地震前兆信息监测的井下集成综合观测系统对各传感器单元的高可靠性和高精度实时观测及便于远程监控要求,提出了井下磁力计单元的数据采集、控制和实时传输系统.针对井下仪器不能进行人工直接操作的情况,设计了高精度的背景磁场自动补偿系统;在上位机GPS定时授时控制下和采用温度补偿有源晶体,设计了高采样时刻记录精度和高幅值记...     

地磁相对记录用低噪声磁通门磁力仪

针对地磁相对记录要求观测仪器具有高分辨力、低噪声和长期稳定性的特点,抑制外界温度对传感器输出的影响,获得较低的温度系数,研制的磁通门传感器采用高导磁率坡莫合金作为磁芯材料,激励线圈直接缠绕在高塑性、较高持久蠕变强度的环形合金骨架上,感应线圈和补偿线圈缠绕在低温度系数的玻璃钢骨架上.采用交变模拟信号处理电路、深度负反馈网...     

SERF原子磁强计用半导体激光器驱动系统

在无自旋交换弛豫(Spin-Exchange Relaxation-Free,SERF)原子磁强计中,半导体激光器被用于极化碱金属原子和检测原子极化率,激光器出射光稳定与否直接关系到SERF原子磁强计的灵敏度,为了保证半导体激光器稳定工作,需要高性能的电流和温度控制单元。通过对激光器控制原理进行研究,以温度控制模块MTD415T和电流控制模块MLD203CHB为核心,通过"集成芯片+外部保护/降噪电路+上位机"的方式构建了一套半导体激光器驱动系统,实现了半导体激光器高稳定性的温度和电流控制,温度稳定性优于±5.0 m K,电流稳定性优于±2.1μA,同时相比较商用的控制器,体积大幅度缩小,促进了SERF原子磁强计的小型集成化。     

UKF based in‐flight calibration of magnetometers and rate gyros for pico satellite attitude determination

In this paper an unscented Kalman filter based procedure for the bias estimation of both the magnetometers and the gyros carried onboard a pico satellite, is proposed. At the initial phase, biases of three orthogonally located magnetometers are estimated as well as the attitude and attitude rates of the satellite. During the initial period after the orbit injection, gyro measurements are accepted as bias free since the precise gyros are working accurately and the accumulated gyro biases are negligible. At the second phase estimated constant magnetometer bias components are taken into account and the algorithm is run for the estimation of the gyro biases that are cumulatively increased by time. As a result, six different bias terms for two different sensors are obtained in two stages, where attitude and attitude rates are estimated regularly. For both estimation phases of the procedure an unscented Kalman filter is used as the estimation algorithm. Copyright © 2011 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society