Modeling of eddy current sensor using geometric and electromagnetic data

In this paper a new modeling method for an eddy current sensor is presented using geometric and electromagnetic data of a sensor and a measuring target It can predict not only sensor output but also medium behavior related to sensor output The geometric data of a sensor coil and the eddy current generated on a measuring target are simplified to an array of circular loops. And to perform computations of the network circuit between sensor coil loops and eddy current loops using the geometric and electromagnetic data in order to consider all possible interactions, the equivalent network circuit of eddy current sensor’s behavior has been drawn. Because the sensor’s initial value, medium behavior, and final value can be shown quantitatively by the proposed modeling method as the geometric and electromagnetic data varies, it can precisely predict the sensor output depending on the measuring goal and application field. Thus the model can be utilized to improve accuracy, eliminate the need for calibration before use, and produce the best design for any given purpose.     

基于电涡流位移传感器列车行驶速度在线测量的方法

电涡流传感器是基于电涡流效应,将非电量转换为线圈阻抗的变化进行测量的。它具有体积小、灵敏度高、动态响应快和非接触测量等优点,目前广泛应用于电力、石化、机械、冶金等行业。本文提出一种基于电涡流位移传感器在线测量列车行驶速度的方法。通过对电涡流位移传感器输出原始脉冲信号处理,最后得到当车轮经过测量装置时只捕获到唯一的信号,根据两个电涡流位移传感器信号上升沿计算得到列车的行驶速度。     

有限元分析涡流效应

以一片变压器的铁心叠片即薄平板导体为模型,用有限元方法直观地表现因涡流效应而引起的磁场与电流的变化,并分析影响涡流大小的因素和减小涡流损害的方法。     

含铁氧体磁芯的电涡流传感器线圈阻抗理论模型和数值计算

针对铁氧体磁芯对电涡流传感器线圈阻抗的影响问题,建立了含铁氧体磁芯的线圈阻抗理论模型,推导了单匝线圈阻抗的级数和矩阵形式,并通过积分获得圆柱线圈的阻抗表达式。因表达式参数多且计算复杂,用有限元法对含Ni-Zn铁氧体磁芯的线圈阻抗进行数值计算,并分析了铁氧体磁芯及其几何参数对传感器性能的影响。研究表明：通过理论模型和有限元法都可获得线圈阻抗值,但后者求解更加简便;铁氧体磁芯可将磁场限定在一定范围之内,提高了传感器的灵敏度;磁芯参数对传感器性能的影响因被测体材料而异。本文的研究可为传感器探头结构优化和性能改善提供理论依据。     

风力发电机混合式刹车系统的电磁涡流刹车研究

针对现代风力发电机刹车系统存在的齿轮箱所受扭矩大、刹车片磨损快等问题,提出了用电磁涡流刹车作为风力发电装置辅助刹车的混合式刹车系统.试验结果表明,该新型刹车系统刹车性能较好,并且解决了上述问题.     

轴承内环感应拆装器的研究

针对轴承内环的过盈装配和拆卸问题,开发研制出了基于工频感应加热技术的轴承内环拆装器,该装置具有可变径和自动定心功能,能够实现加热和拆装的一体化,可实现对轴承内环的快速无损拆装.介绍了装置的基本原理,给出了线圈匝数和集肤深度的数学模型.实验表明,该装置加热效率高,适合于各种工况,因此,具有广泛的应用前景.     

线圈形状及几何参数对电涡流传感器性能的影响

针对电涡流传感器探头线圈形状及其参数对传感器灵敏度和线性范围的影响问题，本文以Biol-Savart定律为基础，推导了具有梯形截面的矩形柱线圈和圆形柱线圈对称轴上任一点的磁场分布，确定了在以位移为检测量的电涡流传感器中采用圆柱线圈更合理，并通过有限元法研究和分析了在线圈匝数密度不变和变化2种情况下圆柱线圈内径、外径、厚度、截面形状（矩形、梯形和倒梯形）对传感器灵敏度和线性范围的影响，为合理选择线圈参数和优化传感器性能提供参考。     

铁磁性构件缺陷的脉冲涡流检测传感机理研究

铁磁性构件的脉冲涡流检测法是一种融合了漏磁检测与涡流检测的新的复合磁传感检测法。建立了脉冲涡流复合传感有限元仿真模型,仿真分析了铁磁性构件电导率、磁导率和导入直流电流激励大小对脉冲涡流响应信号的影响规律。实验结果表明:随着导入直流电流激励增加,铁磁性构件表面缺陷漏磁场和电流密度引起扰动磁场的复合场对脉冲涡流响应信号的影响更显著,而铁磁构件亚表面埋藏缺陷随着缺陷深度的增大而增大,缺陷漏磁及电流扰动磁场的复合场对脉冲涡流响应信号的影响变小,涡流响应信号占主导地位,为脉冲涡流传感器设计奠定理论基础。     

Liftoff insensitive thickness measurement of aluminum plates using harmonic eddy current excitation and a GMR sensor

This paper describes the implementation of a device that measures the thickness of metallic plates. A pancake coil for magnetic field sinusoidal excitation is used and detection is performed with a bridge giant magneto-resistor sensor. The paper uses the theory of the linear transformer to explain the liftoff effect with a special attention to the point of interception phenomenon. The transformer model shows that to attain the interception points with instantaneous measured voltages independent of the liftoff gap the excitation coil must be driven with imposed current. This effect was explored to show that a simultaneous process of thickness and conductivity measurement is feasible.     

电涡流式钢板在线测厚系统设计

介绍涡流传感器的基本原理,论述涡流传感器应用于钢板厚度在线测量的原理、调节系统的设计以及传感器安装间隙的确定。并简要说明了单片机系统结构及其软件设计方法。     

电涡流传感器中变压器型等效电路的适用性研究

为考察电涡流传感器中等效电路的适用性，本文从被测体材料角度出发，在分析等效电路基础上，采用分离变量法和数值计算法，得到不同被测材料下探头线圈阻抗与提离高度的关系，并与从等效电路得出的结论比较，确定等效电路的适用性，同时考察被测体厚度对线圈阻抗的影响，最后对得出的结论进行理论分析。结果表明，等效电路的适用性与被测体的涡流渗透厚度无关；对非磁性材料作用下的检测系统，等效电路适用，对铁磁性材料则不适用；同时在计算线圈阻抗时，应保证被测体厚度大于其涡流渗透厚度的20％。     

无源线圈在电磁感应溶液测量中的增强效应

将一只由线圈与电容元件共同组成的无源线圈放置于探测线圈与待测电解质溶液组成的测量系统中,借助无源线圈与两者之间的电磁感应耦合,可在谐振频率点附近提高测量系统的探测性能。以塑料容器内0~5%质量分数浓度的Na Cl溶液为探测目标,对无源线圈置于目标溶液前侧及背侧两种情况下的阻抗谱进行了实验分析。结果表明,相同探测距离下,介入无源线圈的测量系统对电解质溶液的浓度表现出更高的灵敏度。当目标溶液位于探测线圈敏感距离之外时,介入无源线圈后依然可实现有效的溶液浓度测量。无源线圈的这种增强效应可提升电磁感应系统的有效探测距离,实现电解质溶液或生物组织等低电导率物质的远距离非接触测量。     

Evaluation of transient eddy current oscillations response for thickness measurement of stainless steel plate

Detection of a wall thickness change in pipelines is extremely important to avoid unwanted leakages and accident reduction in industrial structures. In the present study, transient eddy current oscillation (TECO) nondestructive testing (NDT) method has been used to detect the thickness of stainless specimen. Damped free running oscillations that are generated by cyclic exchange of energy between a capacitor and an induction coil in the TECO probe, are used to induce the eddy currents into the test specimen. The resultant magnetic field is detected by using a Hall sensor in the vicinity of the test specimen. The experimental results are analyzed in the frequency domain by calculating the power spectral density (PSD) of the detected decay of oscillations response from the probe. Two features, peak frequency and −3 dB bandwidth of the PSD, are used to interpret the thickness variation in test specimen. The TECO method has been successfully applied to measure the thickness of stainless steel plates.     

圆台状脉冲涡流差分传感器缺陷检测信号的解析计算

将傅里叶变换理论应用于圆台状脉冲涡流差分传感器缺陷检测信号的求解,提出了一种缺陷检测信号的解析计算方法。首先分析了缺陷检测信号谐波系数随缺陷尺寸变化的规律,而后根据电磁波反射与折射理论建立了圆台状差分传感器磁场解析模型,并根据谐波系数随缺陷尺寸变化的规律得到了任意缺陷检测信号傅里叶变换系数的通用表达式,最后经傅里叶反变换得到了任意缺陷的时域差分检测信号。通过实验对所提算法进行了验证,结果表明:该算法可准确求得圆台状脉冲涡流差分传感器缺陷检测信号,且具有较快的计算速度。     

Study on wireless sensing for monitoring the corrosion of reinforcement in concrete structures

The reinforcement corrosion has a serious impact on durability and safety of reinforced concrete structures. Based on radio frequency technology, the wireless sensor for the monitoring of reinforcement corrosion is investigated in this paper. The sensors are fabricated and experiments on the sensors are carried out. Experimental results show that it is feasible to determine whether the steel wire is broken or not by monitoring the resonant frequency of the circuit, and the sensor with spring switch designed in this paper can solve the problem of the resonant frequency missing of the sensor during the process of the steel wire corrosion. The encapsulation materials for the sensors are studied.     

Light intensity analysis of a passive visual sensing system in GTAW

In manual welding, an experienced welder acquires 80% of the welding process information by vision. Visual sensing has the advantage of supplying abundant information without contact with the workpiece or welding circuit. Visual sensors have been widely used in the field of welding. According to optical imaging principles, the object imaging process depends on the shape, size, position, and angle of the light source; the shape of the object; the reflectance characteristic of the object’s surface; and the position, angle, and inner parameters of the camera. In order better to utilize the image information of a visual sensor and to ascertain the weld shape and size, arc light intensity is calculated from the arc length and the welding current. The visual sensing system is analyzed from the point of the view of light intensity. The function of adjusting the system to the light intensity is formulated in this paper. A relationship between the gray image, arc length, and welding current can be obtained. Welding experiments were implemented. Thus, we can recover the shape and height of the weld pool by SFS (shape from shading) algorithms from the weld pool image.     

基于B_z(p_(max))相轨迹的电磁涡流无损检测方法

基于电磁涡流检测的变压器等效理论,提出一种相轨迹分析方法。该方法对正弦激励下空间磁通密度信号进行相敏解调,并绘制其相轨迹图。仿真及实验结果表明,在激励线圈所在平面上,磁通密度法向分量B_z在其空间极大值点处p_(max)呈现出良好的线性特征:随提离高度变化,其R-I平面上相轨迹按固定参数线性变化;而被测铝板表面或内部的微小缺陷则会引起线性化参数的明显改变。该结论为设计对提离高度不敏感的电磁涡流检测装置提供了理论指导。     

远场涡流无损检测技术在管道中的应用

远场涡流检测技术在国外发达国家中已充分应用于现场,且收效显著。国内还处于研究认识阶段。本文针对远场涡流检测技术的理论作了分析研究,并在实验室也做了相关的实验,实验结果表明,检测信号的幅值和相位可以反映套管的壁厚信息,检测信号的幅值和相位随管壁厚度成线性关系。     

一种恒流源电路的巧妙设计

本文主要介绍了在温度巡检仪系统中恒流源电路的巧妙设计，系统采用恒流源电路作为信号的获取电路，恒流源电路是采用价格低廉的器件通过比较巧妙的设计构成的，恒流效果十分理想。同时也介绍了温度传感器在现场的安装技术。     

矩形脉冲涡流传感器的三维磁场量与缺陷定量评估

脉冲涡流是一种有效的电磁无损检测技术。基于脉冲涡流检测原理设计了脉冲涡流检测系统,并对矩形脉冲涡流传感器的三维磁场量进行了研究。分别在传感器的不同走向下,使用三维检测传感器获得了三维磁场量的Bx、By与Bz曲线。在传感器的不同走向下,提出使用三维蝶形图对缺陷进行检测识别。对三维信号进行特征分析后,分别在不同走向下,通过Bz曲线评估缺陷的深度。通过By与Bz曲线的特征可以测量缺陷的长度。为进一步实现飞机机身缺陷的成像检测提供了有价值的参考。