超声传感埋弧焊焊缝跟踪的研究

本文提出了一种非接触超声传感埋弧焊焊缝跟踪系统。介绍了超声波传感器及其焊缝跟踪工作原理。在焊缝跟踪中既可以采取检测焊缝坡口的跟踪方法,也可以采取检测磁性胶条的跟踪方法。埋弧焊焊缝跟踪实验表明,该系统具有良好的动态性能和控制精度。该焊缝跟踪方法能够满足压力容器焊接工程的需要。     

接触式 光电传感焊缝跟踪技术的应用

现代电子技术及焊接控制技术的新发展,推动了焊缝自动跟踪技术及设备的更新换代。一般地说,焊缝跟踪传感器分为两大类:接触式或非接触式。由于焊接施工条件等原因,使得非接触式传感器如电磁式、红外式、激光扫描式、电感应式、计算机图象识别式等技术的应用受到很大限制,加之上述控制方法抗干扰能力差、成本高、原理比较复杂,因此近几年来,抗干扰性能好、价格低廉的接触式传感器在国     

基于机器视觉的焊接跟踪技术的应用研究

在传统接触式埋弧焊焊缝跟踪系统的基础上,通过摄像机进行焊接坡口复合跟踪。焊接前,对焊接坡口进行数据采集,运用计算机进行图像处理,生成虚拟焊缝识别系统。焊接时,虚拟焊缝识别系统控制焊枪,实现焊缝自动跟踪,从而达到实时和精确．保证了焊接质量。     

焊缝跟踪技术应用研究

基于大型龙门架弧焊机器人平台,对焊缝跟踪技术进行应用,使焊接具备焊缝跟踪功能,改善焊缝质量,提高焊接自动化水平。对一般的对接和角接焊缝进行了直线焊接跟踪实验,结果表明,焊缝跟踪的精度能够达到±1mm以内,较未跟踪焊接焊缝质量显著提高。     

基于LabVIEW的窄坡口管道焊接电弧传感测控系统

针对窄坡口管道焊接电弧跟踪的技术需求，搭建了基于高速摆动的多轴运动控制和电弧传感测控系统。基于LabVIEW的软件开发平台，开发了信号采集、滤波、偏差提取、多轴运动焊缝跟踪、起/停弧控制及人机交互程序。完成了基于CANopen协议的多轴运动控制程序开发。进行了平焊位置窄坡口短路过渡焊缝跟踪试验。试验结果表明：该测控系统可实现电流信号采集、滤波处理及偏差提取。偏差提取程序和死区PID控制策略可行有效，实现了焊缝跟踪，平焊位置最大跟踪误差为15.04%,跟踪精度为±(0.12～0.15)mm。验证了电弧跟踪测控系统各程序功能和跟踪算法的有效性。基于LabVIEW的电弧传感测控系统，编程量小，程序结构简单，能够满足窄坡口焊缝跟踪功能的理论分析和快速开发要求。     

基于传感器焊缝跟踪技术发展现状

针对目前焊接传感器在研究应用领域种类繁多,使用场合纷繁复杂,本文按照传感器在焊缝跟踪的发展过程中,主要分为三种方式:直接电弧式、接触式、非接触式。阐述各种传感器的工作原理,比较每种传感器在应用中的经济效益、实用性以及优缺点,在焊缝跟踪技术传感器具体使用中具备一定参考意义。     

自调整比例因子Fuzzy-P控制在焊缝跟踪中的应用

介绍了自调整比例因子Fuzzy—P控制理论及其在非接触超声传感焊缝跟踪系统中的应用。试验表明,该系统具有良好的控制特性,能满足焊接工程应用的要求。     

基于视觉传感的焊缝跟踪控制系统

介绍了传感器在焊接生产中的应用和视觉传感原理。分析了视觉传感焊缝跟踪系统的原理和特点。提出焊缝图像特征提取方法和流程，以及实施焊缝跟踪控制的方法。系统采用条形光传感方法，选用CCD等光学器件组成焊缝图像传感系统，然后将获取的焊缝图形信息进行识别处理，获得焊接电弧与焊缝中心是否偏离、偏离方向和偏离程度的处理结果。根据这一结果，调整电孤与焊缝中心的相对位置，消除电弧与焊缝的偏离，达到焊接电弧准确跟踪焊缝的目的。     

基于光纤声发射传感技术的刀具健康监测系统研究

基于光学原理设计了一种非接触式光纤法-珀声发射传感系统,建立非接触式光纤法-珀声发射实验装置,用于刀具的健康监测.实验结果表明,该传感器制作简单,加工成本低,安装容易,能有效实现刀具健康状态的非接触式监测.     

电弧传感器的研究及应用现状与面临的问题

实现焊接自动化的两个主要难题是:焊缝跟踪和焊接质量控制。其中焊缝跟踪是保证焊接质量的前提,所以实现焊缝的自动跟踪就成为首先要解决的问题。一个焊缝跟踪系统包括以下两个主要的方面:传感器与控制器。传感器根据传感方式的不同可以分为附加式传感器和电弧传感器两大类。传统的焊缝跟踪传感器多数是属于附加式。例如,接触式传感器、电磁传感器和各种光学传感器,这类传感器都在焊炬上固定一个附加的机械、电磁或光学装置,用于检测焊缝的相对位置,其共同的问题就     

焊缝跟踪中的非接触式超声波传感器的研究

介绍了超声波的物理基础,研制了焊接缝跟踪中的非接触超声波传感器。利用声阻抗匹配技术减小了超声波的传输损耗。设计了聚焦透镜,使声束焦点直径达到了０．５ｍｍ。     

焊缝跟踪FUZZY－P控制规则的研究

介绍了一种非接触超声传感焊缝跟踪系统。该焊缝跟踪系统采用了Fuzzy－P控制理论,即在大偏差时采用比例控制,在小偏差时采用自调整模糊控制。研究了Fuzzy－P控制的阈值和比例控制的规则。介绍了自调整模糊控制的原理,提出了焊缝跟踪中的双因数自调整模糊控制方法。在试验的基础上确定了双因数的数值。应用公式法生成了模糊控制规则表。同时分析了自调整模糊控制中的比例系数对系统动态特性的影响。通过试验确定了该系统中的比例系数的数值。试验证明,该跟踪系统具有快速、准确、稳定的特点,完全能够满足实际工程应用的需要。     

In situ Measurement of Journal Bearing Lubricant Viscosity by Means of a Novel Ultrasonic Measurement Technique Using Matching Layer

An ultrasonic viscometer was used to measure the circumferential viscosity variation in a journal bearing noninvasively. This sensing technique is based on the reflection of a shear wave at a solid–liquid boundary that depends on the viscosity of the liquid and the acoustic properties of the solid. Very little ultrasonic energy can propagate into the oil at a metal–oil interface because the acoustic mismatch is significant. Interleaving a matching layer between the metal and the lubricant enables accurate ultrasonic viscosity measurements (M. Schirru, et al., Tribology Leters, Vol. 60, No. 3, 2015). This technique has been used to build a miniaturized ultrasonic viscometer that is accommodated inside a journal to obtain the circumferential viscosity profile. Four viscosity regions are identified due to the variations in the localized temperatures and loads. The results are compared with the isothermal solution of the Reynolds equations for hydrodynamic lubricated bearings. The ultrasonic viscometer locates the angle at which the maximum load occurs and the length of the loaded contact with good accuracy. Finally, the viscosity results are used to estimate the frictional power losses. It is shown that over 70% of the total losses in the journal bearing occur in the region where the load is maximum.     

Assessment of combined V/Z clamp-on ultrasonic flow metering

Clamp-on ultrasonic flow metering can provide a non-invasive and portable means for flow measurement. However, it indicates flow rates with low measurement accuracy at low flow velocity in pipe flows. Typical accuracy of the clamp-on ultrasonic flow metering amounts as low as ±1% if the flow velocity in a pipe is greater than 0.5 m/s. The accuracy can be increased greater than ±2% if the flow velocity is lowered smaller than 0.5 m/s. Inner pipe diameter can be also an influential factor in flow metering when the exact value of the inner diameter is not known. The inner pipe diameter cannot be found if the pipe is too large to measure or if there are erosions or adhesions on the inner pipe surface due to small particles in the flow. These shortcomings of the clamp-on ultrasonic flow metering can be overcome by combining two transit times along a Z-shaped and a V-shaped ultrasonic path. This technique is termed combined V/Z clamp-on ultrasonic flow metering. With the water flow standard system in KRISS, this combined technique exhibited intermediate performance between the two flow metering techniques along the Z-shaped and the V-shaped ultrasonic paths. Notably, the combined technique showed better performance (expanded uncertainty less than 0.76%, k = 2) than the two flow metering techniques (1.61% and 1.17%, k = 2) in the flow range of (100–400) m³/h with pipe diameter of 250 mm.     

基于 ELM 的超声多特征融合螺栓应力测量方法

针对传统超声波螺栓应力测量中存在的非线性和不适定性问题,提出一种基于极限学习机(ELM)的超声多特征融合 螺栓应力测量方法。 首先基于声弹性理论和散射理论,根据超声回波信号提取声时差及瑞利散射范围内多晶体材料中纵波的 衰减系数等超声波特征参数。 然后通过向量降维选择声时差、衰减系数和有效受力长度作为模型输入特征向量,建立了基于 ELM 的超声多特征融合螺栓应力测量模型。 搭建螺栓轴向应力超声波测量实验平台,对不同材料和规格的螺栓进行螺栓应力 的测量,并对比了使用传统的超声测量方法的测量结果,验证了传统超声检测方法的局限性。 对比了 ELM 与其他机器学习方 法包括 BP、支持向量回归(SVR)的测量结果和精度。 结果表明,提出的方法有效克服了传统超声测量方法的不足,能实现不同 材料不同规格的螺栓应力测量,并且测量精度更高(平均相对误差为 3. 86% ),泛化能力更好。     

Ultrasonic fingerprint sensor in underglass prototype using impedance mismatching

Fingerprint imaging is a powerful tool in biometric identification systems. There are several methods for measuring fingerprints, such as optics, capacitive, and ultrasonic methods. The previous ultrasonic imaging techniques have been available in immersion systems which require the hands to be put into water. Also, pulse-echo system in dry condition has coupling layer which is similar acoustic impedance to human tissue or high impedance materials based on waveguide. For fingerprint imaging in the dry state, we propose an ultrasonic imaging technique in underglass by using the impedance mismatch between the fingertip and the solid plate. We present the image results according to the plate material such as acrylic, glass and PDMS. In addition, simulation results based on small 2-D array transducers in a near field suggest the feasibility of compact and fast fingerprint scanning system. Therefore, this work presents feasibility of ultrasonic pulse-echo fingerprint sensing method for dry hand.     

采用微型排水罩的药H焊丝水下焊接焊缝自动跟踪系统

针对水下焊接图像噪声大、清晰度差的特殊情况,设计并研制成功一套药芯焊丝水下焊接的视觉传感焊缝自动跟踪系统.该系统由视觉传感、图像预处理及偏差识别系统,控制系统和执行机构等组成.采用小波多尺度变换进行水下焊缝图像边缘提取,结果保留大多数的细节,得到有利于焊缝位置特征提取的预处理图像,在一种基于二值图像的焊缝中心位置识别算法计算后,得出焊缝偏差.在理论分析视觉传感焊缝自动跟踪系统模型的基础上,设计满足跟踪精度要求的规则自调整模糊算法.对影响跟踪系统精度的因素进行分析,并采用相应的措施以提高系统的精度.通过药芯焊丝湿法水下焊接焊缝自动跟踪试验表明,采用规则自调整模糊控制能够达到较高的焊缝跟踪精度.在斜线、折线和曲线三种不同形状待焊焊缝的跟踪试验中,系统都能满足药芯焊丝水下自动焊接的要求.经过改进微型排水罩,进行微型排水罩局部干法药芯焊丝水下焊接焊缝跟踪试验,采用规则自调整模糊控制,不仅得到满意的焊缝跟踪效果,还改善焊缝成形质量.     

焊缝特征值提取与分析

在主动式视觉传感器的焊缝跟踪系统中，提出了新的接缝图像处理和特征值提取的算法，详述了直线段的调整、线段拟合算法以及接缝特征值的获取。经过误差分析，焊枪与接缝的实际偏差为0.2mm。     

Developments in microultrasonic machining (MUSM) at FEMTO-ST

The aim of the article is to present new developments in microultrasonic machining concerning design and manufacture of a complete acoustic system optimized for ultraprecise processing on 2-in. wafer and examples of microstructures produced at FEMTO-ST institute, particularly in piezoelectric materials. The potentialities and the limitations of the ultrasonic machining technique are discussed. The choice and the dimensions of the material for the acoustic transducer were defined through finite element modeling. Other parameters affecting the machining process such as static load of the tool, vibration amplitude, grain material and size of the abrasive slurry, and workpiece characteristics were hierarchized experimentally in order to increase machining quality (surface state, precision) and minimize tool wear.