基于FPGA的金属膜厚检测系统

根据多频电涡流检测原理,设计了基于FPGA的检测系统,实现了涡流传感器的多频激励和阻抗分析,发现传感器的峰值特征频率与被测金属膜厚相关,进而从峰值特征频率捡取金属的膜厚信息.通过对多层铝箔进行测量实验,并采用保形拟插值对实验数据进行拟合,得到满意的测试结果.系统基于FPGA架构,可实现对金属膜厚度的实时、在线测量.     

ω-λ型涡流阵列传感器跨阻抗响应特性分析

针对金属螺栓连接结构的孔边疲劳裂纹监测需求,介绍了一种具有柔性平面特点的ω-λ型涡流阵列传感器,构建其损伤监测半解析模型,应用半解析模型并通过传感器跨阻抗双参数网格平面图,分析了不同激励频率下传感器跨阻抗输出信号对损伤输入参数的监测灵敏度.分析结果表明,传感器的电导率和磁导率监测灵敏度随提离距离增大而减小;在固定频率下,存在最优监测灵敏度的电导率点和磁导率点,且最优磁导率点随激励频率增大而增大,最优电导率点随激励频率增大而减小;存在磁导率临界值点,当磁性材料的磁导率达到临界值后点,传感器的跨阻抗输出随提离距离增大而减少.     

微小轴承相对位移的测量

研究了微型电涡流位移传感器测量垂直安装的转子系统下端轴承副由于松动和不良摩擦引起的相对位移.通过实验并结合理论分析,说明该转子系统运行过程中轴与轴承之间微小的相对运动对转子动力学行为的影响.     

基于矫顽力与剩磁的铁磁性材料应力测量

铁磁性材料的磁滞回线代表其在外加磁场下的基本磁特性,磁滞回线反映的磁特性参数磁导率μ、矫顽力H_C、剩磁M_R能灵敏地反应铁磁性材料的微观组织结构。针对铁磁性材料受应力易发生形变的问题,该文研究铁磁性材料内部磁畴结构和所受应力的关系,利用应力引起的磁特性参数的变化确定材料所受的应力大小,基于U型磁轭的电磁检测原理,测量激励线圈中的电流值和感应线圈上的电压值,采集被测磁回路的磁滞回线并计算矫顽力、剩磁。结果表明:矫顽力数值会随拉力的增大而升高,剩磁随拉力的增大呈阶段性变化,利用矫顽力与剩磁可以实现铁磁性材料的受力分析。     

Ar瞬态方程非线性涡流检测信号数值模拟研究

针对一个简化的三维铁磁性材料数值计算模型,对其非线性涡流检测信号进行数值模拟研究。基于Ar瞬态方程的基本原理改良并开发用于计算非线性涡流检测信号的数值模拟程序,得出非线性涡流检测信号与磁性材料因塑性变形而产生的磁导率变化之间的相关性。对比非线性涡流数值模拟结果和实验检测结果表明:塑性变形导致的磁导率变化是非线性涡流检测信号变化的直接诱因。     

振动涡流传感器关键技术研究

目前,大型旋转机械轴振动监测主要使用涡流传感器,其性能的优劣,直接关系到整个机组能否安全可靠稳定运行。针对振动涡流传感器的材料敏感性和温漂问题,分别进行了相关实验研究。首先通过实验数据处理,提出了一种消除材料敏感性的变换方法,并对该方法进行了理论论证;其次在理论上分析了影响温漂的主要因素,提出了一种能够有效减小温漂的方法。最后将两种方法综合应用于探头设计之中,实验表明,振动涡流传感器材料敏感性误差小于3.5%,温漂小于2.5%。     

基于加速度计和弯曲传感器的手指运动姿态监测（英文）

针对动态测量关节角度的需要,本文设计了两种手指运动姿态监测方法.第1种方法是通过基于MEMS技术的三轴加速度计ADXL330对近侧指间关节的运动姿态进行监测.ADXL330是通过每一敏感轴所感知的重力加速度分量来实现这一功能.为验证该方法的可行性,设计了步进电机控制的能在竖直平面内转动的装置.对比传感器的输出和电机转动的角度,结果表明:动态条件下,其绝对误差为1°~3°,相对误差为2%~6%.第2种方法是通过弯曲传感器在弯曲时输出电阻的变化来监测手指的运动姿态.实验结果表明:在一定的允许误差范围内,三轴加速度计ADXL330和弯曲传感器都能用于监测手指运动姿态.     

电涡流传感器阵列测试技术

针对采用扁平柔性电涡流传感器阵列实现大面积金属曲面部件位置实时监测,对电涡流传感器的阵列测试技术进行了研究.采用一种基于时分多路的电涡流阵列测试的方法,通过对传感器探头和测试电路的合理设计,使系统电路得到简化,减小阵列单元之间的串扰,提高传感器系统的测试性能,实现了电涡流传感器阵列的快速、高精度测量.     

光纤式质量流量计的研究

研究出一种光纤传感器与电磁涡流传感器相结合的新型质量流量计,并给出理论模型和实际系统结构。该流量计对旋涡发生体进行了独特设计,即将光纤嵌入到旋涡发生体内部构成光纤式升力检测器。利用光纤的微弯损耗特性,检测出流体流经旋涡发生体时产生的变动升力大小,结合信号电极测量出的涡流频率,由单片机计算出流体质量流量。与其它质量流量计相比,光纤式质量流量计结构简单,抗干扰能力强。以水为被测对象的实验证明,其测量结果的相对误差在1%以内。     

一种便携式角速度传感器

角速度是旋转系统或传动装置进行状态监测的重要参数。设计了一种新结构、无旋转部件的便携式瞬时角速度传感器。该传感器的工作原理是永磁磁钢建立恒定磁通,被测旋转装置的转动部件切割该恒定磁场后形成涡流,涡流产生的磁场与传感器的霍尔元件相互作用产生霍尔电势,该霍尔电势的幅值与被测旋转装置的角速度成正比。根据磁路的基本定律推导出传感器的输出特性,并对输出特性进行了实际的测定,结果表明:传感器的灵敏度为16.8mV·s/rad,非线性误差为1.24%。     

外应力对Terfenol-D棒的应变和磁感应强度的影响

超磁致伸缩材料Terfenol-D是一种新型的功能材料,以Terfenol-D为核心元件设计各种换能器时,磁场H和应力σ是必须考虑的因素.研究了一定偏置磁场下外加压应力对Terfenol-D棒的应变和磁感应强度的影响.首先测试了在一定的偏置磁场下外压应力和应变的关系,结果表明偏置磁场一定时,应变和应力之间的关系复杂,可用磁性材料技术磁化理论来解释.其次又测试了一定偏置磁场下的外加动态应力和磁感应强度的关系,测试结果表明一定的偏置磁场下,外加压应力增加,磁感应强度减小;偏置磁场为5kA/m时,磁感应强度达到最大值.该实验结果可以为基于Terfenol-D的换能器件的设计提供技术支持.     

基于逆磁致伸缩的索力传感器原理与影响因素研究

基于逆磁致伸缩效应,建立钢缆索索力传感器理论模型,分析了施加在缆索材料上的力信号(外力和应变)与磁信号(磁感应强度、磁场强度)之间的耦合关系.针对一种环式结构的索力传感器,对索力测量原理做了详细推导,可通过检测感应线圈的感应电压反映材料所受外力.传感器输出感应电压与空气间隙尺寸、外部激励磁场下的材料磁导率、激励磁场变化、加载外力变化等因素有关,重点分析了激励磁场变化和外力变化对传感器输出的影响.当外力是缓变力,可通过检测感应积分电压求得外力;当外力是交变力,直接通过感应电压求得外力;最后通过对磁场变化和外力变化影响分别进行了仿真,结果与理论分析基本一致,表明所建立的索力传感器理论模型可行.     

A Novel Inverse-Magnetostrictive Force Sensor

The change in magnetic permeability of a material under stress (inverse magnetostriction) offers the potential for a high-performance, low-cost force sensor capable of being used in harsh real-world environments. The existing force sensor technologies are limited in their use in commercial products by either cost issues or susceptibility to electromagnetic noise. Inverse Magnetostriction has been used to measure strain in controlled environments since its discovery by Joule in 1847, but not in practical applications due to a lack of data on how magnetic material properties change with environmental conditions such as temperature. Utilizing an innovative noise-reducing self-inductance design, this paper presents the basis for an inverse-magnetostrictive compressive load sensor. A lumped-parameter model for the change in sensor inductance under load, due to both mechanical and magnetic effects, is derived. The material properties of a magnetostrictive iron alloy are empirically determined over a broad range of loads and temperatures. The model and material properties are confirmed by testing a prototype force sensor. The prototype measures compressive forces from 100 to 25 000 N over a temperature range of 20 degC to 120 deg with a typical error of +/-2% (4% max). The sensor does experience significant thermal hysteresis for which the model does not currently account. This work was motivated by the need for a force sensor in an automobile electric brake system and used a single iron alloy (50% Ni), but the model and testing procedure provide a roadmap for future research to improve the performance and capabilities of such a sensor     

Calculation of Skin Depths and Eddy-Current Power Losses for Magnetic Position Sensors

1. IntroductionIn a quasi-stationary magnetic field, eddy-currelltfrom an alternating-current excitation induces secondary currents and fields between magnetic material and position sensor. The skin depths and eddycurreat losses are also induced in a conductor whenan alternating external magnetic field is applied tothe conductor[1]. For a magnetic position sensort ifthe position of the moving sensor is given, the waveform of the output voltage induced by eddy-currentcan be used as an index to …     

Enhancement of Sensitivity of Microwave Planar Sensors With EBG Structures

A strategy to improve microstrip sensor performance for monitoring dielectric properties of materials is proposed. The method relies on the reduction of the wave group velocity to induce higher interaction between the sensor and the material. This is achieved by the design of periodic patterns in the sensor ground plane, which exhibit electromagnetic band gap (EBG) effects. The presence of these EBG structures turns out to be highly effective, inducing a noticeable decrease of the wave velocity. The sensitivity is defined and measured for different sensor configurations in order to quantify the improvements obtained. It is observed that, with the EBG structures, the residence time of the wave in the material under test is longer, and a substantial increase of the sensor sensitivity is obtained. EDICS Category-MICR     

磁屏蔽效能的有限元分析

提出了磁屏蔽效能问题的三维有限元模型的建立方法,应用ANSYS软件得到磁屏蔽效能为28.78,并将结果绘制成曲线,使结果更加一目了然。为了检验计算结果是否符合实际情况,通过一种间接的方法对磁屏蔽效能进行测试。对比分析以上的计算结果和测试结果,可以得出结论:利用有限元法进行磁屏蔽效能计算,对直流传感器的磁屏蔽效能估算具有一定的指导意义。     

The theoretical output of a ring core fluxgate sensor

This article proves that the output from a ring core sensor is directly proportional to the first time derivative of the product of dynamic permeability and magnetic intensity perturbation within the core caused by an external, uniform magnetic field. (Dynamic permeability is defined to be the slope of the hysteresis loop at a given point in time.) Assuming that ellipsoidal shells can approximate the core, the demagnetization factor can be "estimated" in the first order to be proportional to the first power of the quantity tape thickness (or number of wraps) divided by the core diameter. The constant of proportionality is determined from laboratory data. When an additional scale adjustment is applied to the resulting sensor output formula, the computed output tracks laboratory data for a range of sensor geometries.     

Cyclic hysteresis of AZ31B extrusion under load‐control tests using embedded sensor technology

The fatigue behaviour of AZ31B extrusion magnesium alloy under load‐control cyclic test conditions is estimated using a combination of simulation and experimental results. The strain measurement of this asymmetric material is found experimentally using a Fibre Bragg Grating (FBG) sensor during rotating bending tests. Then, to analyse applied stresses in the sample – particularly in the plastic deformation range – the Variable Material Property (VMP) method is employed. Using this simulation method, the hysteresis loops of two critical top and bottom elements of the sample's cross section under different bending moments are obtained. Finally, the strain of the sample during rotating bending, as measured by the embedded FBG sensor, is related to the stresses obtained from the modeling using a mapping function. The hystereses obtained from this combination of the modeling and experimental results are compared with the results of a companion strain‐control pull–push test in which the input strain history was that of measured by the FBG sensor. Observations verify that the stresses of the combined VMP‐FBG hysteresis loops have good compatibility with the stress responses obtained through the experiment. The hybrid model introduced in this work can be employed to capture cyclic hysteresis, and hence estimate the fatigue life, under load‐controlled rotating bending tests.     

Magnetic Nondestructive Test for Resistance Spot Welds Using Magnetic Flux Penetration and Eddy Current Methods

Resistance spot welding technologies are widely used in industry. A highly reliable monitoring method is needed to effectively weld and create a robust structure. We developed a combined technique using magnetic flux penetration and an eddy current test (ECT). The magnetic measuring system consists of a pair of magnetic probes having an induction coil and detection coil, a lock-in amplifier, a current source, and a personal computer. The magnetic flux penetration through both surfaces at the weld was measured at low frequency. The ECT was performed at each surface with multiple frequencies. The magnetic flux penetration method showed good correlation with the destructive shear test because of the change in permeability due to the formation of the nugget. The ECT method reflected the depth profile of the nugget and was effective for determining a defective product.     

智能材料工艺与结构中的先进传感器的发展

建立复合材料成型过程的智能化在线监控系统,有效地调整生产工艺,科学设计和优化生产工艺,可以有效地提高生产质量,降低生产成本。除生产工艺智能化外,还需建立材料结构的智能化体系,从复合材料固化成型、材料生产到材料应用整个过程均实现智能化,将开辟材料科学研究的新途径。建立智能材料工艺与结构体系需要先进的性能优良的传感器,本文以智能材料体系为背景阐述了各种传感器技术性能及发展方向。