基于遗传算法的激光视觉焊缝特征点提取

提出了一种基于遗传算法的平面焊缝特征点提取方法。采用中值滤波、阈值分割法对焊缝图像进行预处理,以减少噪声;利用种子填充法进行图像分割,提取出激光条纹连通域,根据连通域特征抽象出激光条纹骨架提取的数学模型;重点研究基于遗传算法的骨架提取方法,并采用法向直线扫描法沿骨架方向提取中心点坐标;对骨架中心点进行直线拟合,并利用拉依达准则迭代剔除噪声点,获得激光条纹骨架的准确位置和焊缝特征点坐标。经试验验证可知,该方法能够有效消除焊缝图像中多种噪声及激光条纹宽度的干扰,快速准确地检测出焊缝特征点的位置。     

一种基于激光视觉的焊缝实时检测技术研究

提出了一种基于激光视觉的焊缝实时检测技术,旨在提高焊缝检测的速度和精度。在实际的焊接过程中,由于大量噪声的干扰,焊接图像的采集一直是一个复杂的过程。 本文首先建立基于激光视觉的检测系统,以获得激光条纹的原始图像。在此基础上,将原始激光条纹图像灰度化,并提出一种改进的快速中值滤波算法,在去除图像中椒盐噪声的同时,缩短了程序运行时间。并通过Otsu阈值分割获得激光条纹的二值图像,提取感兴趣的激光条纹区域。接着结合方向模板法和脊线跟踪法提取激光条纹中心线,最后采用亚像素级角点法提取焊缝的特征点。 实验证明,本文提出的方法有效地克服了焊接环境的影响,不仅缩短了焊缝特征点检测的时间,而且具有较高的检测精度,符合实际焊接要求。     

基于条纹式激光传感器的机器人焊缝跟踪系统研究

提出了基于条纹式激光传感器的机器人焊缝跟踪系统,采用机器人末端安装条纹激光传感器,在焊接过程中实时获取焊缝轮廓数据;利用小波变换模极大值理论对焊缝轮廓数据进行分析,确定焊缝特征点;以特征点为分界点,采用最小二乘法拟合焊缝直线并求取交点,精确确定焊缝轮廓特征点坐标;通过机器人坐标变换实时获得焊缝运动轨迹,从而实现焊缝跟踪。对不同的V型焊缝进行实验验证,并对有无采用最小二乘法精确定位进行对比实验。实验结果表明:只采用小波模极大值理论获得的跟踪误差约为0.514 mm,但轨迹存在较严重的抖动现象;而采用了最小二乘法精确定位特征点后,跟踪误差约为0.304 mm,抖动现象明显减弱,满足自动焊接误差要求在0.5 mm之内的要求。     

管道焊接激光视觉跟踪的定位方法研究

为解决在管道自动焊接过程中V型坡口的识别定位问题,提出了一种基于激光视觉传感的局部区域内分步式定位方法。首先建立模板匹配,利用模板匹配方式获取焊缝初始位置区域;然后采用阈值分割和边缘提取获得激光条纹边缘线,通过Shi-Tomasi算法对边缘线进行角点检测,得到边缘线上的亚像素角点位置坐标;最后采用最小二乘法拟合得到精确的边缘直线,对上下边界线求平均值提取激光条纹的中心线,求取直线的交点得到坡口轮廓的拐点信息。通过对实际焊接现场拍摄的50幅同一高度不同位置的图像进行检测,结果表明,分步式定位方法抗干扰性强,精度较高,为完成整个跟踪自动焊接过程奠定了基础。     

激光再制造机器人待加工零件形貌三维重建

采用双目摄像机结合结构光组成主动视觉测量系统,并与机器人耦合,构建了一种具有视觉功能的智能激光加工机器人,能够感知各种复杂曲面轮廓,重建三维形貌。系统由六自由度机器人、双目摄像机和结构光发射器组成。机器人带动双目摄像机和结构光发射器运动,既实现多视角测量,消除测量中的"死角",重建工件的完整三维形貌,又将测量到的点云数据转换到机器人坐标系。阐述了测量原理和数学模型,进行了单摄像机内外参数的标定,双目摄像机相对关系的标定,双目摄像机与机器人之间的手眼关系标定,得到摄像机内参数矩阵,手眼关系矩阵,机器人与世界坐标系关系矩阵。对双目图像进行大步距图像分割,提取目标区域,平滑降低图像噪声,重心法提取亚像素级结构光条纹中心,根据极线约束进行左右条纹配准,三维算法得到空间点坐标,可方便地转换到世界坐标系,实现全局坐标的统一。     

基于改进TLD算法的激光视觉传感型焊缝跟踪

为了解决基于线激光视觉传感的焊缝中心位置定位精度不高的问题, 采用了一种基于改进跟踪-学习-检测(TLD)算法的焊缝跟踪方法。由激光视觉传感器实时获取焊缝图像, 采用将跟踪器与检测器结合的TLD算法实时跟踪焊缝特征点, 同时通过在线学习机制更新分类器参量。在此基础上对激光条纹图像截取感兴趣区域, 大幅减少检测器的搜索区域; 根据激光条纹光强分布特性, 结合纠偏方向选取跟踪器有效特征点, 以此提高算法效率, 对不锈钢板V型焊缝和搭接焊缝进行跟踪试验。结果表明, 跟踪与检测可实现共同定位焊缝中心位置, 其融合的焊缝跟踪方法能够准确地提取焊缝特征点, 两种焊缝跟踪平均绝对误差分别为0.062mm和0.052mm。此方法为提高焊缝跟踪精度提供了依据。     

不等厚板激光焊接焊缝缺陷结构光视觉检测

为了检测不等厚钢板激光焊接焊缝表面缺陷,采用结构光主动视觉检测法和高斯数据拟合技术进行了焊缝表面缺陷检测的实验研究。首先采用高斯拟合法对激光条纹图像进行处理,提取出具有亚像素精度的激光条纹中心线;然后通过最小二乘法拟合出3条相交直线并求其交点,近而获得精确的焊缝端点位置坐标;最后给出焊缝表面缺陷-凹度和凸度的检测方法,并以不等厚钢板激光焊接焊缝为检测对象进行验证。结果表明,这种基于拟合技术的结构光视觉检测法为判断激光焊接焊缝质量是否合格提供了较为准确的判断依据。     

激光拼焊焊缝截面轮廓几何建模方法北大核心CSCD

提出了一种激光拼焊焊缝截面轮廓的几何建模方法,基于Laws纹理滤波和数学形态学闭运算提取了截面的轮廓边缘,分别采用多项式函数模型、指数函数模型、高斯函数模型对提取的截面轮廓边缘进行了曲线拟合,并对拟合结果进行了误差分析。分析结果表明,基于指数函数模型拟合的焊缝截面轮廓上边缘的精度最高,基于高斯函数模型拟合的焊缝截面轮廓下边缘的精度最高。对不同工艺参数条件下获得的激光拼焊焊缝截面轮廓边缘进行了几何建模实验,实验结果表明,提出的方法可以有效地实现激光拼焊焊缝截面轮廓的几何建模。     

一种线结构光亚像素中心坐标提取方法

为了提高光条中心点提取的精度和速度，提出了一种新的线结构光条纹中心亚像素提取方法。首先对图像进行中值滤波，采用轮廓跟踪算法避免扫描光条纹区域外的像素，以此提高计算速度，结合灰度重心法对光条纹中心进行初提取；通过均方灰度梯度法计算光条纹的法线方向并以初提取点为中心进行双线性插值；以提取到的初始点和插值点采用加权灰度重心法计算光条纹中心的亚像素位置。实验结果表明，所提方法的标准误差在0.140 0 pixel左右，运算时间约为0.067 0 s。     

线激光光条中心快速提取算法

提出一种新的快速激光条纹中心提取算法,该算法具有较好的抗噪声或冗余点能力。该算法在传统重心算法的基础上结合轮廓跟踪算法,根据激光条纹在图像中的分布特点,通过阈值轮廓跟踪算法避免了对图像中不包含激光条纹区域的扫描,以此提高了提取速度,不用对整幅图像完成一次扫描即可计算出激光光条中心。所提算法具有复杂度低、计算简单、程序运行时间少等优点。实验结果表明:该算法能够实现对光条中心的快速提取,比Steger算法提速将近70.37倍,比传统重心算法提速将近4.48倍;对光条图像增加噪声(冗余)点后发现,所提算法具有优良的抗噪效果。     

Curved crystal spectrometer for the measurement of X-ray lines from laser-produced plasmas

In order to diagnose the laser-produced plasmas, a focusing curved crystal spectrometer has been developed for measuring the X-ray lines radiated from a laser-produced plasmas. The design is based on the fact that the ray emitted from a source located at one focus of an ellipse will converge on the other focus by the reflection of the elliptical surface. The focal length and the eccentricity of the ellipse are 1350 mm and 0.9586, respectively. The spectrometer can be used to measure the X- ray lines in the wavelength range of 0.2-0.37 nm, and a LiF crystal （200） （2d = 0.4027 nm） is used as dispersive element covering Bragg angle from 30° to 67.5°. The spectrometer was tested on Shengnang- Ⅱ which can deliver laser energy of 60-80 J/pulse and the laser wavelength is 0.35 μm. Photographs of spectra including the 1 s2p ^1P1-1s^2 ^1S0 resonance line（w）, the 1s2p ^3P2-1s^2 1S0 magnetic quadrupole line（x）, the 1s2p ^3P1-1 s^2 ^1S0 intercombination lines（y）, the 1 s2p ^3S~1-1 s^2 ^1S0 forbidden line（z） in helium-like Ti Ⅹ Ⅺ and the 1 s2s2p ^2P3/2-1 s622s ^2S1/2 line（q） in lithium-like Ti Ⅹ Ⅹhave been recorded with a X-ray CCD camera. The experimental result shows that the wavelength resolution（λ/△ 2） is above 1000 and the elliptical crystal spectrometer is suitable for X-ray spectroscopy.     

Preparation and Characterization of TaN ALD Precursors

High purity organic-tantalum precursors for thin film ALD TaN were synthesized and characterized.Vapor pressure and thermal stability of these precursors were studied.From the vapor pressure analysis,it was found that TBTEMT has a higher vapor pressure than any other published liquid TaN precursor,including TBTDET,TAITMATA,and IPTDET.Thermal stability of the alkyl groups on the precursors was investigated using a 1H NMR technique.The results indicated that the tertbutylimino group is the most stable group on TBTDET and TBTEMT as compared to the dialkylamido groups.Thermal stability of TaN precursors decreased in the following order:TBTDET ＞ PDMAT ＞ TBTEMT.In conclusion,precursor vapor pressure and thermal stability were tuned by making slight variations in the ligand sphere around the metal center.     

Electronic Structure of Semiconductor Nanocrystals

This paper reviews our recent development of the use of the large-scale pseudopotential method to calculate the electronic structure of semiconductor nanocrystals, such as quantum dots and wires, which often contain tens of thousands of atoms. The calculated size-dependent exciton energies and absorption spectra of quantum dots and wires are in good agreement with experiments. We show that the electronic structure of a nanocrystal can be tuned not only by its size,but also by its shape. Finally,we show that defect properties in quantum dots can be significantly different from those in bulk semiconductors.     

Critical Stage Rule-Based Real Time Dispatch（RTD）System in Highly-Mixed-Products （HMP） FAB

An improving utilization and efficiency of critical equipments in semiconductor wafer fabrication facilities are concerned. Semiconductor manufacturing FAB is one of the most complicated and cost sensitive environments. A good dispatching tool will make big difference in equipment utilization and FAB output as a whole. The equipment in this paper is In-Line DUV Scanner. There are many factors impacting utilization and output on this equipment group. In HMP environment one of the issues is changing of reticule in this area and idle counts due to load unbalance between equipments. Here we'll introduce a rule-based RTD system which aiming at decreasing the number of recipe change and idle counts among a group of scanner equipment in a high-mixed-products FAB.     

GaAsSb/InAlAs PA DHBTs Grown by Production MBE

The epi material growth of GaAsSb based DHBTs with InAlAs emitters are investigated using a 4 × 100mm multi-wafer production Riber 49 MBE reactor fully equipped with real-time in-situ sensors including an absorption band edge spectroscope and an optical-based flux monitor. The state-of-the-art hole mobilities are obtained from 100nm thick carbon-doped GaAsSb. A Sb composition variation of less than ± 0.1 atomic percent across a 4 × 100mm platen configuration has been achieved. The large area InAlAs/GaAsSb/InP DHBT device demonstrates excellent DC characteristics,such as BVCEO＞6V and a DC current gain of 45 at 1kA/cm2 for an emitter size of 50μm × 50μm. The devices have a 40nm thick GaAsSb base with p-doping of 4. 5 × 1019cm-3 . Devices with an emitter size of 4μm × 30μm have a current gain variation less than 2% across the fully processed 100mm wafer. ft and fmax are over 50GHz,with a power efficiency of 50% ,which are comparable to standard power GaAs HBT results. These results demonstrate the potential application of GaAsSb/InP DHBT for power amplifiers and the feasibility of multi-wafer MBE for mass production of GaAsSb-based HBTs.     

Influence of polarization extinction ratio on distributed polarization coupling detection

Distributed polarization coupling in polarization-maintaining fibers can be detected by using a white light Michelson interferometer. This technique usually requires that only one polarization mode is excited. However, in practical measurement, the injection polarization direction could not be exactly aligned to one of the principal axes of the PMF, so the influence of the polarization extinction ratio should be considered. Based on the polarization coupling theory, the influence of the incident polarization extinction on the measurement result is evaluated and analyzed, and a method for distributed polarization coupling detection is developed when both two orthogonal eigenmodes are excited.     

Noise character analysis and the restraint of self-pulsation laser diodes

We calculate the Langevin noise sources of self-pulsation laser diodes, analyze the effects of active region noise and saturable-absorption region noise on the power fluctuation as well as period fluctuation, and propose a novel method to restrain the noise effects. A visible SIMULINK model is established to simulate the system, The results indicate that the effects of noise in absorption region can be ignored; that with the increase of DC injecting current, the noise effects enhance power jitter, and nevertheless, the period jitter is decreased; and that with external sinusoidal current modulating the self-pulsation laser diode, the noise-induced power jitter and period jitter can be suppressed greatly. This work is valuable for clock recovery in all-optical network.     

High-quality single-crystal CdSe nanoribbons and their optical properties

Large-scale synthesis of single-crystal CdSe nanoribbons is achieved by a modified thermal evaporation method, in which two-step-thermal-evaporation is used to control CdSe sources＇ evaporation. The synthesized CdSe nanoribbons are usually several micrometers in width, 50 nm in thickness, and tens to several hundred micrometers in length. Studies have shown that high-quality CdSe nanoribbons with regular shapes can be obtained by this method. Room-temperature photolumines-cence indicates that the lasing emission at 710 nm has been observed under optical pumping （266 nm） at power densities of 25-153 kW/cm^2. The full width half maximum （FWHM） of the lasing mode is 0.67 nm     

Propagation of hermite-cosh-gaussian beams passing through ABCD optical system with an annular aperture

By using the expansion of the aperture function into a finte sum of complex Gaussian functions, the corresponding analytical expressions of Hermite-cosh-Gaussian beams passing through annular apertured paraxially and symmetrically optical systems written in terms of ABCD matrix were derived, and they could reduce to the cases with squared aperture. In a similar way, the corresponding analytical expressions of cosh-Gaussian beams through annular apertured ABCD matrix were also given. The method could save more calculation time than that by using the diffraction integral formula directly.     

中国建立EB级存储实验室,致力云计算应用(英文)

正With the support of 863 programs,Sugon Information Industry Co.,Ltd.,set up a dawning EB-class storage laboratory to address massive data storage requirements and largescale cloud computing demonstration applications.The Dawning EB-class cloud storage system adopts advanced fault-tolerant architecture,efficient data fault-tolerant algorithms with user authentication and data encryption policies to deal with the"lost""wrong"and"stolen"problems of data for ensuring the reliability and safety of the EB-class storage system in the public network application environments.The Dawning EB-class Storage Laboratory taking advan-