A low power micro fluxgate sensor with improved magnetic core

The influence of an improved magnetic core on the micro fluxgate sensor about sensitivity and power consumption is investigated and discussed in this paper. We have fabricated the micro solenoid fluxgate sensors based on the MEMS technologies, with the electroplating permalloy cores, which are easy to process and used in common; and the amorphous soft magnetic ribbon cores, which have better soft magnetic performances but be hard to be integrated, respectively. Four magnetic core structures are designed, including rectangular structure, unequal width rectangular structure, multi rectangular ring structure and spiral structure. Spiral structure can improve the performances of the fluxgate sensor significantly, both sensitivity and power consumption. The micro fluxgate sensors with the amorphous soft magnetic ribbon cores are promoted in all aspects than those with the electroplating permalloy cores, including ultra low power consumption of 2.4 mW with unequal width rectangular structure, and high sensitivity of 118 V/T with rectangular structure in wide linear range of 0–800 μT.     

Improved micro fluxgate sensor with double-layer Fe-based amorphous core

A rapid manufacturing process for the micro solenoid fluxgate sensor integrating multilayer amorphous ribbon core has been established, which combines the micro assembling method and the MEMS technologies. We select Fe-based amorphous soft magnetic ribbons for core materials and have fabricated the micro fluxgate sensors by MEMS technologies, with single-layer core and double-layer core respectively. The micro fluxgate sensors with double-layer core show the advantageous to that with single-layer core and exhibit sensitivity of 1089.2 V/T at excitation current of 120 mA rms, wide linear range of ?900 to 900 μT and power consumption of 24.48 mW. The noise power density of the single core fluxgate sensor is 2.48nT/Hz^1/2@1 Hz.     

Low power integrated fluxgate sensor with a spiral magnetic core

Facing the new integrated applications, coordination between three parameters of the micro fluxgate sensor, namely, sensitivity, power consumption and operation range, is the key to make the applications come true. This paper reports a new low power micro integrated fluxgate sensor with low cost solution. A spiral electroplating permalloy magnetic core is introduced to reduce excitation current. Due to the design of little coils resistance and thick magnetic core, the fluxgate sensor exhibits a power consumption of 7.35 mW, a sensitivity of 117 V/T and a linear range of −200 to 200 μT. Compared with the constant-width magnetic core and the multi rectangular ring magnetic cores, experiment results show that the spiral magnetic core benefits both smaller excitation current and higher sensitivity. The newly developed fluxgate sensor maintains high sensitivity and wide linear range with low power consumption.     

Two-axis micro fluxgate sensor on single chip

We present a two-axis micro fluxgate sensor on single chip for electronic compassing function. To measure X- and Y-axis magnetic fields, functional two fluxgate sensors were perpendicularly aligned and connected each other. The fluxgate sensor was composed of square-ring shaped magnetic core and solenoid excitation and pick-up coils. The solenoid coils and magnetic core were separated by benzocyclobutane which had high insulation and good planarization characters. Copper coil patterns of 10 μm width and 6 μm thickness were electroplated on Ti (300 Å)/Cu (1,500 Å) seed layers. 3 μm thick Ni_0.8Fe_0.2 (permalloy) film for the magnetic core was also electroplated under 2,000 gauss. Excellent linear response over the range of ?100 μT to +100 μT was obtained with the sensitivity of ～280 V/T. Actual chip size was 3.1×3.1 mm². The sine and cosine signals of two-axis fluxgate sensor had a good function of azimuth compass.     

微型磁通门传感器的低功耗结构设计

微型磁通门的功耗是影响其整体性能的关键因素.要降低功耗必须保证器件的薄膜铁芯能够在较小的激励电流下进入饱和状态,为此,可以通过降低铁芯的饱和磁场强度Hs来实现这一目标.设计了一种具有多孔结构薄膜铁芯的微型磁通门,经过有限元仿真分析发现,多孔结构能够降低磁通门铁芯的饱和磁场强度Hs,从而获得较小的饱和激励电流,在保证微型磁通门灵敏度的同时,有效降低器件功耗.     

Improved performance of the micro planar double-axis fluxgate sensors with different magnetic core materials and structures

As a classic weak magnetic field sensor, the fluxgate sensors have great potential application in many fields. This paper presents four kinds of the micro planar double-axis fluxgate sensors based on the MEMS technologies, which have different core materials and core structures. The core materials include electroplated permalloy, Co-based amorphous ribbon and Fe-based amorphous ribbon, and the core structures include single-layer open magnetic loop structure and double-layer closed magnetic loop structure. The sensor with closed double-layer Fe-based ribbon core exhibits a best sensitivity of 238 V/T due to reducing the magnetic flux leakage. The results show that the magnetic core with closed magnetic loop, high permeability and high saturation induction density will help increase the sensitivity of the micro double-axis fluxgate sensor.     

微型磁通门铁芯结构的拓扑分析与优化

多孔铁芯有利于满足微型磁通门传感器降低功耗的要求,但不同的拓扑结构所取得的效果不同,对多孔铁芯结构进行了拓扑分析与针对性优化,并采用微机电系统(MEMS)工艺制备了不同铁芯结构的微型磁通门进行性能测试与对比验证.实验结果证明:优化后的铁芯结构能更好地降低微型磁通门传感器功耗,提高器件整体性能.     

闭环反馈式数字磁通门传感器

针对传统磁通门传感器模拟电路温度性能相对较差的问题,研究了一种闭环数字磁通门传感器。利用高速A／D直接采样传感器信号,用单片机进行数字信号处理,再经D／A转换输出反馈信号。详细介绍了传感器的硬件结构和软件设计,并用该传感器对地磁场进行了测量试验。结果显示：它的零位温度系数为6．7×10^-10／℃,灵敏度温度系数为2．5×10^-4／℃,线性度达到了5．4×10^-3。     

RTD型磁通门传感器检测系统设计

为了对外界静磁场进行检测,设计了滞留时间差(RTD)型磁通门传感器的检测系统.通过对检测系统信号调理电路、数字存储单元以及数据处理算法等方面的设计优化,提高了检测系统的检测精密度和准确度.在电磁屏蔽室中,利用赫姆霍兹线圈给定外磁场,对所设计的检测系统进行测试,实验结果表明:时间差波动小于±0.1μs,在±5 ×104 nT范围内线性度误差为±0.21％,灵敏度为22.4 s/T,多次测量标准差不大于0.03,适合用于对静磁场的检测.     

数字磁通门传感器的自动相位对准

三轴数字磁通门传感器信号处理电路的延时(相位延迟)及各轴延时不一致,影响数字滤波器的输出性能。提出了基于加权最小二乘法的互功率谱相位法计算延时的方法,针对该数字滤波器的特性,选择传感器的不同谐波信号对比分析相位延迟计算的精度,并设计了传感器的自动相位对准方法。实验结果表明:该计算方法精确有效,自动相位对准使滤波器输出性能提高25.89%。     

A differential transformer-based force sensor utilizing a magnetic fluid core

Microsystem Technologies - A force sensor utilizing a transformer concept with a ferrofluid core was developed. A ferrofluid reservoir was machined out of Teflon and the open top of the reservoir...     

Stress dependence of sensitivity of fluxgate sensor

This paper presents results of investigation of the stress sensitivity of the fluxgate sensor with amorphous alloy (CoFe)₈₉(MnMoSiB)₁₁ (Vitrovac 6150F) ring core. Stress was applied in two directions: perpendicularly to the flux density in the ring core or in the direction of diameter of the ring. The influence of mechanical stress from the external forces on magnetic properties of this ring core was measured. Then results of this testing were used in computer simulation of the influence of the stress on the output signal of the fluxgate sensor.     

基于单片机的数字磁通门传感器

主要研究了一种数字磁通门传感器.这种传感器采用单片机的A/D对磁通门输出信号进行采样.采样后的数据通过串口送给计算机进行运算,并得到最终的输出量.该传感器对地球磁场进行了测量.结果显示:它的误差较小,改善了传统磁通门传感器的温度性能,提高了输出信号的稳定性.     

基于磁通门与重力加速度传感器的钻井测斜仪

介绍了以磁通门技术与加速度计为工作原理的钻井测斜仪,阐述了两种传感器的工作原理及测斜仪的结构设计,推导出井斜角、方位角、工具面角的数学模型。测斜仪采用幅值相位法和二次谐波法检测信号,采用内置单片机处理数据,通过对采集的数据进行逐点修正的方法来消除多种误差的影响,使测斜仪的测量精度得到显著提高。     

新型环形同点单铁芯双分量磁通门传感器

双分量磁通门传感器在金属磁记忆检测中得到广泛使用,且使用的双分量磁通门传感器为双铁芯式跑道型设计的磁通门传感器。由于传感器中的双铁芯磁参数不一致、铁芯不闭合的原因,产生变压器效应,形成了测量噪声。双分量磁通门通常由两个磁通门传感器平行放置而成。因此,由于传感器铁芯参数,线圈参数不可能完全一致所造成的传感器之间的一致性差,而且双分量或多分量磁通门传感器存在着几何中心不重合的问题。本文研究设计了新型双分量磁通门传感器,采用环形铁芯设计,直接应用单铁芯调理双方向的磁通门信号,改善了双分量传感器的一致性差、几何中心不同点的问题,有效的抑制了变压器噪声,提高了磁通门传感器的测量中的测量准确度,减少了测量误差。     

磁通门传感器在车辆导航系统中的应用研究

针对现行车辆导航系统中测角传感器的一些不足和磁通门传感器的特点,将磁通门传感器用于车辆导航系统当中,测量车体的航向和姿态角.并针对在使用过程中存在的问题,提出了基于正交函数的最小二乘拟合法消除车体磁场对传感器测角精度的影响和卡尔曼滤波方法补偿测角过程中的观测误差,有效地提高了磁通门传感器的测角精度.最后,通过实验,验证了2种方法的可行性,测角的最大误差仅为0.74°,达到了令人满意的导航定位效果.     

双分量环形磁通门测斜传感器测量原理分析

在地下勘测,钻井探矿等领域,需要测斜仪对钻头的姿态进行精确定位与控制,实时监测地底下钻头的姿态变化。现有的测斜仪通常为三分量磁通门传感器与三分量加速度传感器相结合,其结构复杂,且磁通门传感器与加速度传感器的轴向要求方向一致,因此需要人工调节与算法调节,加大了前期传感器布置与补偿的计算难度。本文研究了新型测斜传感器,采用环形铁芯设计和铁芯不固定的方法,设计了双分量环形磁通门传感器,并通过铁芯与磁通门传感器的敏感轴方向上磁通量之间的角度关系,通过三维坐标轴旋转计算得出测量被测物体的俯仰角等姿态变化。经过试验表明,新型测斜传感器能对物体的姿态角进行精准测量,精度高,且省去了加速度传感器,简化了传感器结构和测量参数,并且简化了角度测量算法与正交度补偿算法。     

一种平面四轴向磁通门传感器的设计

设计了一种新型的四轴向磁通门传感器,可测量铁磁性目标经过时产生的磁异信号在四个轴向上的变化情况,通过各轴间的相关性即可判断出目标的运动方向。结构中将四个三端式磁通门探头单元相间45°摆放,使得传感器的任一侧都有四个磁场强度分量的输入,结合分时激励的方法,与传统磁通门传感器相比,其具有电路简单,灵敏度高、稳定性好、功耗小等优点。经实验表明,该传感器方向识别正确率可达85%以上,能够较好的应用于安防及侦测领域中对目标运动及其方向的监测。     

MEMS micro fluxgate sensors with mutual vertical excitation coils and detection coils

As a classic Earth magnetic field sensor, fluxgate magnetic sensors have great potential applications in many fields. This paper presents a new 3D micro-solenoid fluxgate magnetic sensor based on the MEMS technique. The excitation coils were placed vertically to the detection coils on the chip plane, around a rectangular shaped magnetic core. Polyimide was used to insulate coils and magnetic core. Width of copper conductor lines is 50 μm, and line space is 50 μm. The design of such fluxgate magnetic sensor followed second harmonic signal selecting method. Phase-lock amplifier was used to get second harmonic signal output by detection coils. The linear range of 0–80 μT with sensitivity of 6.7 V/T was achieved from the fabricated sensor with excitation current of 430 mA and the operational frequency of 40 KHz. As the excitation current was 470 mA, linear range of 0–50 μT with sensitivity of 21.7 V/T was achieved.     

An optical navigation sensor for micro aerial vehicles

This paper describes a catadioptric microsensor for multidirectional imaging and 3D egomotion computation. Inspired by the wide viewing angle of insects’ compound eyes, we show how to extract egomotion information from spherical images. We demonstrate how reflective surfaces can be used for building a compact, multidirectional eye that enables to collect video from 60% of the full sphere. Some experiments performed on synthetic images (using a ray-tracing environment) are presented to validate the concept. We have called the resulting imaging system SICONS (SIngle Chip Optical Navigation Sensor). SICONS is intended for application in micro unmanned aerial vehicles (micro-UAVs) to develop their perceptive, visual guidance and motive abilities to move within the real world in the same way an insect does.