基于变面积式双涡流传感器的焊缝跟踪系统

针对薄板对接接头错边问题以及搭接接头难以实现焊缝跟踪问题,提出了一种基于变面积式双涡流传感器的焊缝跟踪方法.将两变面积式涡流传感器置于焊缝的一侧,通过双传感器分别检测高低和左右的位置信息,相互补偿得到独立的偏差信号以实现焊缝跟踪.分析了变面积式涡流传感器的原理,利用响应面法拟合响应曲面,进行变量分离,得到了输出电压信号与面积的关系式.最后,搭建简易平台进行了薄板对接及搭接的焊缝跟踪试验.结果表明,双涡流传感器焊缝跟踪方法具有可行性与正确性,为自动焊缝跟踪技术研究提供了新的研究方向.     

基于MM32的磁浮电机位移控制系统设计

针对现有的磁悬浮电机位移控制响应速度过慢且过载保护有缺陷的问题,设计一种基于MM32的双闭环控制系统以实现转子位移的快速控制和过载保护。以电涡流传感器对转子位置进行实时检测,结合双闭环PID控制算法,通过隔离驱动芯片UCC27714DR对控制器的输出电流进行控制,从而实现转子在平衡位置的运转和过载时的保护。实验结果表明：电机转速发生改变,控制系统在0.1 s内改变输出电流的大小使其维持平稳运转;过载时使电机以较低速度停止运转,减小过载损害。     

Eddy current nondestructive testing with giant magneto-impedance sensor

Technologies based on magnetic sensors with high sensitivity such as magneto-resistance (AMR, GMR), fluxgate or squid sensors have demonstrated their capability to improve the performances of the classical eddy current (EC) probes.In this paper, a new kind of magnetic sensor based on giant magneto-impedance (GMI) effect has been evaluated. This sensor combines good sensitivity performances at low frequencies and small size. The design of a probe using this new technology has been optimized with fast semi-analytical models. The performances of this GMI based probe have then been successfully evaluated on a 304 L stainless steel mock up for the detection of embedded flaws.     

AlN-based sputter-deposited shear mode thin film bulk acoustic resonator (FBAR) for biosensor applications — A review

A new type of biosensor device is here presented which is fabricated using the same processes used for the fabrication of integrated electrical circuits to enable tighter integration and further sensor/biosensor miniaturization. The device is a so-called thin film bulk acoustic resonator (FBAR) operating in shear mode. Here specifically AlN-based shear mode FBAR is addressed but also an overview of the shear mode FBAR development in general is presented. Developments are reported of a low temperature reactive sputtering process for growing wurtzite-AlN thin films with a close to homogenous c-axis inclination over a 4″ substrate wafer. This process enabled fabrication of shear mode FBAR sensors. The sensor operation is described along with how the design parameters influence its performance. Specifically, sensitivity amplification utilizing low acoustic impedance layers in the FBAR structure is demonstrated and explained. The resolution of the AlN shear mode FBAR sensor is demonstrated to already be comparable with the conventional quartz crystal microbalance (QCM) sensor, suggesting that shear mode FBAR may be a competitive and low cost alternative to QCM.     

一种基于VB的超声波线切割机导轨误差的测量与补偿系统设计

以机床导轨误差理论为基础,基于VB设计了一种机床导轨误差测量与补偿系统。该系统采用光栅传感器来确定导轨的水平位置,通过电涡流位移传感器把被测量(机床导轨误差)转化成电信号,用USB2828数据采集卡的AD功能把传感器输出的电信号转化成数字信号,按传感器及驱动电源的灵敏度计算出补偿误差所需的电压值,再用采集卡的DA功能输出电信号给驱动电源。驱动电源的输出电压控制微位移器的位移(即刀尖的位移)变化,实现了导轨误差的补偿。实验结果表明测试系统的设计较合理,基本达到了补偿的要求。     

金属回转体表面涡流探伤装置设计

为更准确地对昂贵金属回转体进行裂纹定位工作,根据涡流检测原理设计一种用于金属回转体表面的裂纹检测装置。该检测装置采用涡流传感器直线移动、回转体旋转的检测方式对回转体的外表面进行全面检测。检测装置主要由变速器、传动结构、涡流传感器、提离调整机构和坐标记录结构组成,通过涡流传感器-数据采集卡-计算机之间的数据传递来对输出数据进行降噪、显示及储存。该装置可用于较大直径回转体表面裂纹的检测与储存,给裂纹车削工作提供方便,也为其他设计人员提供了参考。     

应用于微弱涡流信号检测的正交锁定放大器设计

涡流检测是一种广泛应用的常规无损检测技术,涡流传感器输出微弱信号的检测是整个系统的关键。设计了一种基于互相关原理的模拟正交锁定放大器,其采用数字频率合成器AD9854发生正交参考信号,通过模拟乘法器AD734进行互相关运算,利用低通滤波器MAX291获得的同相直流分量和正交直流分量。对两路直流分量进行运算,可以得到涡流信号幅度和相位的变化量,从而判定待测对象的特征。通过涡流检测试验应用,结果表明,该放大器可方便地应用于涡流检测系统中,性能可靠,工作频率可达5MHz。     

The fabrication of micro-heaters with low-power consumption using SOI and trench structures

This paper presents the optimized design, fabrication and thermal characteristics of micro-heaters for thermal MEMS (micro electro mechanical system) applications using SOI and trench structures. The micro-heaters are based on a thermal measurement principle and contain thermal isolation regions of 10 μm-thick Si membranes consisting of oxide-filled trenches in the SOI membrane rim. The micro-heaters were fabricated with Pt-RTD on the same substrate via the MgO buffer layer between the Pt thin-film and SiO₂ layer. The thermal characteristics of the micro-heaters with trench-free SOI membrane structure was 280°C at an input power of 0.9 W; in the presence of 10 trenches, it was 580°C due to the reduction of the external thermal loss. Therefore, a micro-heater with trenches in the SOI membrane rim structure provides a powerful and versatile alternative technology for enhancing the performance of micro-thermal sensors and actuators.     

铝合金焊缝裂纹的阵列涡流检测仿真研究

为了分析阵列涡流传感器扫查不同位置表面横向裂纹时的线圈输出信号特征,以及焊缝受热区金属材质变化对线圈输出信号的影响,建立铝合金焊缝裂纹的阵列涡流检测的三维有限元模型。结果表明:当裂纹长度分别为1.6、3.0、4.5mm时,裂纹长度与线圈感应电动势的波峰幅值呈单调递增关系,探头扫查侧面裂纹时的线圈感应信号总是大于正上方裂纹;焊接所引起的5A06铝合金材料电导率减小会使线圈的感应电动势幅值增大,且当裂纹长度分别为1.6、3.0、4.5 mm时,裂纹长度越大,电导率减小在裂纹检测时对线圈输出信号的影响越小。     

Forming of Micro Channels with Ultra Thin Metal Foils

The objective of this paper is to investigate the feasibility of producing micro scale structures by forming ultra thin metal foils. During this investigation, flat rolled foils of AISI 304 stainless steel (2.5μm in thickness) and pure copper (3.0μm in thickness) were formed into channels of varying shapes. The shapes of these channels were straight lines, concentric circles, crosses, and other curved shapes. The cross sections of the channels ranged from 10∼20μm wide and 5-10μm deep. Forming was done by cold isostatic pressing. Two types of micro dies were used. One was made of SU-8 photo resist on a Si wafer, the other of dry etched (DRIE) Si wafer. The die and metal foil were vacuum packed in a bag made of multilayered film. The forming was conducted with a 240MPa cold hydrostatic press. The formed structures were examined in terms of their dimensions, surface qualities, and potential for defect. The fabrication results show that the sheet metal forming process can be applied to the manufacturing of micro scale structures.     

Measurement of the electrical conductivity of open-celled aluminium foam using non-contact eddy current techniques

This paper studies the electrical properties of open-celled aluminium foams manufactured by a novel sintering-dissolution process (SDP) using non-destructive eddy current testing. Experimental measurement results are first presented by means of an impedance analyser under swept frequency testing for the determination of electrical conductivity of Al foams. A double air-cored solenoidal sensor has been constructed for the purpose of evaluating cylindrically shaped samples used in the investigations. The effects of porosity (relative density) and pore size, which are the principle parameters of the foams, on the conductivity are examined. The results demonstrate that the electrical conductivity of Al foam is strongly dependent on both porosity and pore size. The sensor geometry is further simulated electromagnetically using finite element methods, by which the mutual impedance between two coils is calculated to solve the forward electromagnetic (EM) induction problem to provide a calibration curve relating the mutual impedance change with the electrical conductivity of the sample. The results obtained from experimental measurements are found to be in good quantitative agreement with the finite element simulations.     

高温连铸坯表面缺陷脉冲电涡流检测方法研究

高温铸坯表面缺陷在线检测对降低生产成本、提高铸坯的热送热装和直接轧制率具有重要意义。提出采用脉冲电涡流检测方法,对高温铸坯表面及近表面缺陷进行在线无损检测。介绍了脉冲电涡流高温铸坯表面缺陷检测方法试验装置,试验研究了脉冲电涡流探测器检测线圈信号的时域特征和频域特征,并给出缺陷信号特征提取方法。研究成果为进一步研究高温铸坯表面缺陷无损探伤装置提供理论基础和技术支撑。     

外圆磨削颤振监测方法设计

磨削颤振是影响加工质量和加工效率的重要因素,常需增加多个后续加工周期来满足加工质量的要求。采用涡流传感器、磨削力传感器、声发射传感器、加速度传感器和接触探头等多传感器对砂轮边沿的自激振荡进行测量,对自激振荡信号,提出采用幅值法和小波分析法进行分析处理,实现了磨削颤振的自动监测和预测,减少了加工周期,提高了加工效率。     

Effects of atomic layer deposition temperatures on structural and electrical properties of ZnO films and its thin film transistors

Organic-inorganic thin film transistors (OITFTs) with Al/ZnO/PVP structure on Si substrate were fabricated and studied as to their structural and electrical properties. PVP (poly-4-vinylphenol) organic gate insulator was coated on Si substrate by spin coating method. The ZnO was deposited as an active layer by using the atomic layer deposition (ALD) method on PVP/Si substrate at various temperatures ranging from 80 to 140 °C. The structural and electrical properties of ZnO thin films were analyzed by X-ray diffraction and by hall-effect measurement system for optimum process of the OITFT. The grain size and carrier concentration of ZnO films increased, and the resistivity decreased as the deposition temperature increased from 80 to 140 °C. The field effect mobility, on/off current ratio and threshold voltage of OITFTs with ZnO active layer deposited at 100 °C were found to be 0.37 cm²/V·s, 5×10² and 5 V, respectively.     

Development of SDT sensor based eddy current probe for detection of deep fatigue cracks in multi-layer structure

The detection and characterization of deeply buried fatigue damage in thick, multi-layer airframe components pose significant technical challenges to the aviation safety community. Currently, no nondestructive evaluation technique is available to reliably detect such potential damage from the exterior of the airframe, which is highly desirable in light of inspection cost as well as avoidance of structure damage. Recent technological advances in high-sensitivity magnetic sensors, i.e., spin-dependent tunneling (SDT) sensors, make it feasible to employ electromagnetic inspection techniques for deep fatigue crack inspection. In this work, we report on the development and fabrication of a low frequency eddy current probe based on a magnetically shielded SDT pickup sensor concentrically located in the interior of an induction drive coil to enable localized deep diffusion of the electromagnetic field into the part under test. Simulation studies were conducted to demonstrate the deep penetration capability of this probe configuration and to understand inspection sensitivity based on magnetic field perturbation due to subsurface cracking. Experimental results obtained using this SDT sensor on samples with induced flaws demonstrate its potential for practical application.     

一种基于摆动式涡流传感器的焊缝跟踪方法

采用非接触电涡流传感器应用于焊缝跟踪,利用指数运算电路补偿传感器的线性度,从而加大了传感器的量程,消除了传感器在焊缝跟踪过程中的失真情况.选用摆动式涡流传感器检测焊缝偏差信息,实现复杂形状焊缝的平板对接I形坡口的自动跟踪.应用区域积分差值加权比较法对焊缝的偏差信息进行分析,消除了因板厚不均匀以及错位的误判,在采样数据点不变的情况下,提高了焊缝跟踪精度.结果表明,摆动式涡流传感器用于焊缝自动跟踪可行,跟踪效果好,为目前对自动焊缝跟踪技术的研究提供了一种新的方法.     

基于频谱分析的涡流探头工作频率确定方法及检测系统研究

涡流检测对某一被测量的检测灵敏度很大程度上依赖于试验频率。文章提出了一种基于频谱分析的涡流探头最佳试验频率获取方法,设计了数字化涡流阻抗检测系统。在该系统中,激励信号具备扫频输出和单频输出功能,探头检测信号拾取后数字化分解为实部和虚部。借助该系统,可方便、快捷、实时地获取每一探头的阻抗频谱,根据实际需要分析获得最佳试验频率。     

焊接逆变电源与涡流检测融合设计分析

根据焊接逆变电源与涡流检测的工作原理,在焊接逆变电源中加入涡流检测激励与接收部分的模拟信号处理电路,而涡流检测的数字信号处理部分则与焊接逆变电源共用,实现焊接逆变电源与涡流检测的融合设计.焊接逆变电源主变压器输出的交流方波经过滤波后,以滤波器输出的正弦波作为涡流检测的激励信号,驱动涡流检测探头,涡流检测探头接收的信号经过放大、比较、检波及后续的数字信号处理进行缺陷判断,实现涡流检测.结果表明,该融合系统能够在不影响焊接的条件下为逆变电源增加涡流检测功能.     

粗糙集的约简算法在涡流传感器设计中的应用

用粗糙集理论从传感器设计的大量数据中提取最小规则集，约简过程表明，核属性中只有测量参数，即涡流传感器结构参数对灵敏度的影响是通过与测量参数的配合而起作用的，应用粗糙集约简算法，不仅获得了传感器的设计规则，而且揭示了影响传感器性能的因素之间的关系，为涡流传感器设计提供了新的知识。     

铝硅合金变质效果涡流检测时传感器的阻抗分离研究

根据活塞合金ZL108的变质质量与材料电导率呈单调函数关系的规律,利用电涡流原理检测ZL108的变质质量。研究应用移相、混频和滤波技术将电涡流传感器阻抗中的电阻分量和电感分量分离出来。设计的测量电路使传感器信号一方面与电源信号混频,另一方面与移相π/2的电源信号混频,并从前者获得电涡流传感器阻抗中的电阻分量,从后者中获得电感分量。最终确定根据电涡流传感器电阻的改变获得ZL108合金的变质信息,消除了电感分量的影响,提高了测量的准确性。