磁通门传感器在低空亚音速飞行器上应用的响应频率分析

对比分析常用磁传感器的性能指标, 得出磁通门传感器作为地磁导航磁测传感器的相对优势性。针对磁通门传感器在低空亚音速飞行器上应用的可行性, 从分析磁通门传感器的基本原理入手, 通过对某地实测磁异常场数据的频谱分析, 利用奈奎斯特抽样定理从响应频率方面对其在低空亚音速飞行器上应用的可行性进行验证, 并提出在低空亚音速飞行器上应用的响应频率指标, 即磁通门传感器的响应频率达到40.8~68.0 Hz, 就能够满足其作为低空亚音速飞行器磁场数据采集前端的响应频率需求。     

微磁传感器在无源导航及导引技术中的应用前景

介绍了利用地磁场实现无源导航及导引的技术途径及可能性.主要是利用核心器件微磁传感器的特性研制导航及导引所用的磁通门传感器、磁强计和磁罗盘等.介绍了国内外新型巨磁阻抗非晶丝传感器的基本原理及其发展情况并分析比较了几种微磁传感器的性能和特点,分析了达到制导精度所要求的微磁传感器的分辨率和数据采样的速率.描述了地磁匹配制导技术的途径和方法,给出了地磁场的参考模型以及每个点地磁参数的计算方法.介绍了微磁传感器在近炸引信方面的应用.最后描述了微磁传感器在无源导航及导引技术中的应用前景.     

基于ANSYS的磁通门传感器仿真设计

文章通过ANSYS有限元仿真软件来设计磁通门传感器,根据性能指标要求仿真设计出最佳的传感器模型参数。按照仿真设计的模型参数制作样机实物,得到样机的性能均达到设计指标要求,且两者灵敏度的误差小于2.1%。     

均分直槽微结构光纤光栅磁场传感器

对微结构光纤磁场传感器的增敏性能进行研究, 设计了一种基于飞秒激光微加工的均分直槽型微结构光纤磁场传感器。 利用飞秒激光在刻有光纤布拉格光栅(FBG)的单模光纤(SMF)包层上刻蚀均分直槽微结构, 并采用HF溶液清除直槽内的残留碎屑和 应力集中点,随后用磁控溅射技术在加工部位溅射一层磁致伸缩薄膜TbDyFe。当外界磁 场强度变化时,通过观测传感器中心 波长的变化可实现对磁场强度的测量。直槽微结构能减小光纤横截面积,改善光纤轴向伸缩 性能,增大薄膜附着表面积,从而 提高传感器探头灵敏度。理论分析了直槽微结构提高传感器性能的工作原理,介绍了传 感器探头的制备工艺和性能影响因 素,给出了不同参数传感探头的磁场测试结果。实验结果表明,利用飞秒激光加工直槽微结 构能明显改善传感器探头灵敏度, 其中直槽个数对性能影响最为明显;相对于无微结构传感器探头,有微结构光纤探头灵敏度 最高可提升3.8倍。     

基于结构优化的微型磁通门降噪技术研究

对铁芯结构的改进有利于降低微型磁通门传感器的噪声,本文对铁芯结构进行了拓扑分析与优化,并采用标准MEMS工艺制备了相应的多孔铁芯结构微型磁通门,对所制备的微型磁通门进行了主要噪声指标的综合测试与对比分析。实验结果表明,改进后的多孔铁芯结构能很好地降低微型磁通门传感器的噪声,提高器件的综合性能。     

一种磁通门传感器的选频放大电路设计

由单个运放和电阻、电容网络构成的传统磁传感器信号处理电路中的选频放大电路是一种多环反馈型带通滤波器,其拥有电路结构简单、可靠性高、成本低等特点,但由于电路中电阻、电容的值较大,不易于集成。基于将磁通门传感器微型化的目的,在已有的Hspice磁通门探头信号产生模型的基础上,提出了一种由双二阶模块级联的开关电容带通滤波器来实现选频放大的方法,运用互补开关技术和动态范围定标技术,提高了滤波器的精度。利用Hspice进行仿真验证,结果表明:3 V供电电压下,与用CMOS技术实现的传统模拟带通滤波器相比,开关电容带通滤波器能较好地将磁通门传感器中的二次谐波进行选择并放大。     

基于LabVIEW的井下弱磁信号检测系统

本文介绍了井下弱磁信号产生的模型与原理。为了对井下弱磁信号实现检测及改善信号的信噪比,利用信号累加平均对弱磁信号检测系统设计。采用软硬件相结合的设计方法,以Labview为虚拟仪器软件开发平台,结合磁通门传感器、信号调理电路以及数据采集卡组成弱磁信号检测系统,该系统具有数据采集、处理分析和保存回放的功能。测试结果表明,该系统对弱磁信号检测具有性能稳定,分辨率高,界面友好,操作简单的特点,在石油工业及其他各个领域都有广泛的应用价值。     

基于TMS320F2806的感应电机控制系统

设计了一种基于TMS320F2806无速度传感器的感应电机矢量控制系统,采用转子磁场定向,实现磁链与转矩的解耦控制,利用PI自适应控制原理控制速度和电流,通过磁通估算模块计算磁链和磁通角,然后通过开环速度估计模块估算转子的角速度。实验结果表明,该系统设计简单实用,性能良好。     

基于FPGA的数字磁通门传感器系统设计和实现

针对传统磁通门信号处理电路中模拟元件的缺点,设计一种基于现场可编程门阵列（FPGA）的数字磁通门系统。整个系统采用闭环结构,由激励产生模块、信号处理模块和负反馈模块组成。外围模拟电路用高速D/A、A/D芯片取代,有利于系统温度稳定性的提到。FPGA内的数字逻辑实现了磁通门信号解算、激励正弦信号发生、D/A、A/D输入/输出串并转换的功能,首先用硬件描述语言（HDL）设计并仿真,然后下载、配置到FPGA中,调试完成后进行实验,通过实时处理双铁芯磁通门传感器探头输出信号对系统进行测试。实验结果证实了系统功能的正确性。闭环结构的采用提高了系统信号梯度线性度,与模拟系统相比,基于数字逻辑的设计温度性能更稳定,更易于小型化,可移植性更强。     

三分量磁通门传感器非正交性误差校正

静态磁场测量中,由于三分量磁通门传感器的非正交性,使得高分辨率测量要求不能得到满足,必须校正其测量误差。通过分析三分量磁通门传感器非正交性误差,给出其数学模型描述,提出了一种基于实数编码遗传算法的校正方法。应用于三分量磁通门传感器非正交性误差的校正,提高了传感器磁场测量的准确度。实验表明,该算法提高了三分量磁通门传感器非正交误差的校正效果。     

Fluxgate Sensor Theory: Stability Study

This paper introduces a gating function that straightforwardly represents the fluxgate mechanism separately from the complications of hysteresis and demagnetization. The characteristics of the gating function are easily measurable and can be regarded as the performance indices of the sensor. The paper also presents a general-state equation that is valid not only for single sensors, but also for symmetric multiple sensors (e. g., gradiometers). Based on the theories of Floquet-Lyapunov and of Hsu, the instability criterion and the method of calculation are investigated. The generalized instability map illustrated on a parameter plane will be useful for the design of stable fluxgate sensor systems.     

A 2D CMOS microfluxgate sensor system for digital detection of weakmagnetic fields

This paper presents a CMOS two-dimensional (2-D) vector magnetic sensor system integrating two planar microfluxgate sensors and the complete electronics for sensor excitation and signal readout. The system is based on an industrial 0.8-μm double-poly, double-metal CMOS technology with ferromagnetic NiFeMo cores added in a simple postprocessing sequence. The fluxgate sensors are embedded in a ΣΔ analog-to-digital converter for a stable and precise digital detection of weak magnetic fields. A cascaded ΣΔ modulator topology is utilized to obtain second-order noise shaping and to suppress pattern noise. Within the range of ±50 μT, the system nonlinearity is less than 1.5 μT. The angular resolution as a 2D vector sensor is less than 4° for a measured magnetic induction of 50 μT. This makes the 2-D microfluxgate magnetometer suitable for use as fully integrated electronic compass     

Vehicle detection using a magnetic field sensor

The measurement of vehicle magnetic moments and the results from use of a fluxgate magnetic sensor to actuate a lighting system from the magnetic fields of passing vehicles is reported. A typical U.S. automobile has a magnetic moment of about 200 A-m²(Ampere-meters²), while for a school bus it is about 2000 A-m². When the vehicle is modeled as an ideal magnetic dipole with a moment of 200 A-m², the predicted results from an analysis of the sensor-vehicle geometry agree closely with observations of the system response to automobiles.     

Noise sources in miniature fluxgate sensors Part I: theoretical treatment

A mathematical model for miniature fluxgate magnetometers is presented in the first part of this work. It is based on certain well-defined and easy-measurable parameters of the hysteresis loop exhibited by the fluxgate magnetic core, i.e., the coercive force and the field intensities at which the flux-reversal starts and saturates. Two signal extraction techniques are modeled, the classical second-order harmonic one, and the current sampling one. For both cases, analytical expressions (in time and frequency domains) are derived for the magnetometer transfer function (voltage vs field) and the influence of the aforementioned hysteresis loop parameters on the magnetometer response. Consequently the signal-to-noise ratio (SNR) in the ELF (Extremely Low Frequency) range and the effective magnetometer bandwidth are calculated for both cases. The SNR is a function of the variance of the aforementioned hysteresis loop parameters. Several noise-sources of different origin have been found to influence this variance, namely: (a) the magnetic (Barkhausen) noise, (b) the noise superimposed to the excitation waveform, (c) the noise generated due to electromagnetic-interference, and (d) the noise generated due to mechanical vibration of fluxgate cores. The extend, up to which the power of these noise-sources boost the variance of the aforementioned hysteresis loop parameters, is a function of certain fluxgate core characteristics, namely: (a) the saturation magnetization, (b) the coercive field, (c) the flux-reversal duration, (d) the dependence of flux-reversal duration on the excitation field slope (slew rate), (e) the core cross-section, and (f) the core frequency response (magnetic damping and magnetic viscosity). Finally, the conditions are investigated so that the current-sampling technique exhibits better SNR compared to the classical second-order-harmonic one. In the second part of this work the theory presented here is applied to explain the noise performance of miniature fluxgates employing amorphous wire cores.     

Analysis and Experimental Verification of a Three-Dimensional Noncontacting Angular Motion Sensor

A three-dimensional noncontacting angular motion sensor, based on magnetometry, has been developed for velocity feedback in the ball wheel mechanism, which serves as the drivetrain for a class of omnidirectional mobile platforms. More generally, this scheme tracks rigid-body rotation about a fixed point with an undefined axis of rotation. The approach involves tracking the time-varying magnetic field of a permanent disc magnet embedded at the center of the sphere. This data is then used to determine the absolute orientation of the magnet axis. Finally, an approach based on the natural invariants of rigid-body motion is used to determine the instantaneous axis of rotation and the angular speed of the sphere about this axis. In this paper, the sensing scheme is formulated, effects of geometric offsets within the tri-axial fluxgate magnetometer are addressed, and results from experimental verification are presented.     

Noise sources in miniature fluxgate sensors. Part II: the case of sensors with Fe77.5Si7.5B15 amorphous wire cores

As a continuation of Part I this paper is devoted to fluxgate sensors that employ Fe_77.5Si_7.5B₁₅ amorphous wires as magnetic cores, with attention being paid to fluxgate miniaturization. Two types of fluxgate sensors have been constructed. The first type is based on the high axial anisotropy exhibited by amorphous wires and employs two coils, an excitation and a receiving one. The second type employs the large Matteucci effect, owed to helical anisotropy induced into such wires either by mounting under torsion or by torsion annealing. The latter fluxgate type employs one single excitation coil. The exploitation of the Matteucci effect indicates that it may lead to the construction of miniature fluxgate sensors. The voltage-output of a series of such sensors has been sampled and processed. The repeatability of the flux-reversal process in the presence of helical or axial anisotropy is quantitative and qualitative investigated to allow for understanding the nature of noise. The existence of noise-sources that have been modeled in Part I is investigated and their power spectral density is estimated, from the experimental results. The influence of several manufacturing parameters in the noise at the output of fluxgates sensors is experimentally verified. Such parameters are the dimensions of the core, the presence and thickness of the glass-cover in glass-covered wires, the level of applied stress and torsion, working temperature level, and the characteristics of the excitation waveform. An irregular behavior at the hysteresis loop of fluxgates that employ the Matteucci effect is observed, which could be understood as a kind of perming effect. Measurements of the repeatability and hysteresis errors, of the sensors transfer function (output-voltage vs input-field), are presented, along with measurements of the cross-field sensitivity. The latter errors do not count as noise, but may limit the performance of fluxgates significantly, especially when miniaturization is attempted. Finally some design rules and manufacturing hints are proposed for fluxgate-magnetometer noise reduction.     

RTD fluxgate: a low-power nonlinear device to sense weak magnetic fields

Fluxgate magnetometers have always been of interest to technical and scientific communities to sense weak magnetic fields (in the range of 10/sup -6/) with a resolution of 100 pT at room temperature. These devices find applicability in fields such as space, geophysical exploration and mapping, nondestructive testing, and assorted military applications. This article discusses the quantities affecting the RTD fluxgate performances, considerations on the design of an RTD fluxgate, and presents an magnetometer experimental prototype.