浅析贴片机国产化的关键技术

表面贴装技术(Surface Mount System)是评估电子加工行业技术水平的重要依据。贴片机是一种高精度的机电一体化设备,是靠机械运动将电子元器件从供料器中吸取出来并经过校准检测机构对中调整后贴装到电路板(PCB)上的。由于贴装元器件微型化和差异化及贴装技术对速度和精度的要求,必须采取多种精密而高端的机电一体化技术,才能达到机器生产和使用要求。作为SMT生产线的关键设备,外国生产商一直垄断着贴片机市场,价格相当高昂,因此贴片机实现国产化是我国发展的终极目标。当前我国的贴片机技术发展日趋成熟,该文将围绕贴片机的关键技术进行研究。     

基于相位一致性和Hough圆的贴片机视觉定位系统的研究

针对贴片机关键技术中的视觉定位进行了研究。由于图像的亮度对定位的影响比较大,给出一种结合相位一致性与Hough圆的方法。利用相位一致性分别对采集到的PCB板上的一对对角线上的两个Mark圆进行边缘检测,用Hough圆变换分别检测两个Mark圆在图像坐标系下的圆心坐标。由两坐标系间的关系,将其转换成机器坐标,计算出PCB板的偏转角;再以其中的一个Mark圆为参考点,利用PCB板中的数据库信息,计算出PCB板上各元件的实际机器位置,上传到控制机。实验结果表明,这种方法定位精度较高,对图像的亮度和对比度影响较小,抗干扰性好。     

拱架式贴片机贴装路径优化

贴片机工作时贴装头需在喂料器与印刷电路板之间频繁移动，缩短贴装头移动距离是提高贴装效率的重要途径。对多头拱架式贴片机贴装路径优化问题进行研究，分析贴装头沿喂料器移动取料时贴装路径变化，建立贴装头移动距离表达式。以贴装头移动距离最小为目标建立贴装路径优化模型，以贴装位置编号对取贴顺序编码，利用遗传算法对取贴顺序和取料方向进行优化。分析不同取料方式下贴装路径差异和结构特点，结果表明：双向取料与近侧取料在贴装点位置分布偏于PCB单侧较多时出现结构性差异，采用双向取料可获得比近侧取料更短的贴装路径，更利于提高贴装效率。     

一种基于矩形拟合的LED贴片机元件定位算法

针对LED贴片机中元件的视觉定位问题,提出了一种基于矩形拟合的元件定位算法。利用大部分LED贴片灯珠为矩形的几何特征,首先根据背景灰度对采集图像进行全局阈值分割;然后以顶点为界将元件轮廓坐标分为四组并做等间隔采样;最后根据矩形相邻两边正交的特性对采样坐标进行矩形拟合实现元件定位的目的。实验表明,该方法具有较高的准确性和较强的鲁棒性,符合高精度贴片机的贴装要求。     

基于Harris角点特征的贴片元件视觉定位算法

为了实现贴片机视觉系统对贴片元件的高精度定位,提出了一种基于Harris角点特征的贴片元件偏转角度与偏移量检测方法.首先对元件图像进行预处理,以改善引脚部分的图像质量,然后标记元件引脚的连通区域,判别元件引脚形状,再通过Harris角点特征提取、分类和直线拟合等得到元件的偏转角度,最后对元件图像进行旋转和放大处理,并进行基于Harris角点特征的图像配准,得到元件的偏移量.检测结果表明,文中算法能够检测贴片元件的偏转角度和偏移量,对偏转角度的检测误差小于0.1°,对偏移量的检测误差小于25μm,满足贴片机对视觉系统定位算法的精度要求.     

基于灰度信息的PCB板精确定位

利用模板匹配法在待测PCB图像中建立坐标系,采用基于边缘灰度幅度的轮辐法检测定位圆,由幅度排序相关搜索算法检测出最佳圆;提出PCB板角度定位的3种算法,比较了不同算法在检测精度、速度和稳定性上的差异,实证了轮辐法可实现PCB板的精确快速定位.     

基于单CCD视觉定位的BGA自动贴装系统设计

针对BGA芯片的特点,设计了基于单摄像机视觉定位的自动贴装系统,介绍了单CCD视觉系统的构成及原理,避免了多CCD之间的标定引入的误差.研究了整个系统的标定方法及标定过程.并针对BGA芯片焊点的对称性设计了相关的图像处理算法,使系统实现高速贴装.     

一种用于AOI的PCB拼接算法

针对自动光学检测技术(AOI)在PCB板检测中存在的图像拼接严重错位、系统响应速度慢、拼接精度差等问题,对PCB图像拼接算法进行了改进研究.首先,提出整行缩小以及以行图像为配准图像的方式进行图像拼接;其次,在传统PCB图像拼接算法上引入surf配准,采用图像金字塔尺度空间的方法,确定拼接图像间的对应特征点,选取最近邻次近邻的配准方式进行特征匹配.实验结果表明:提出的拼接算法,生成图像的数据量相对较少、速度较快,误差不会累积传递,消除了错位偏差,并解决了因光照不均而造成拼接缝隙的问题,大大提高了拼接的精度和速度,为AOI系统后续准确识别PCB板缺陷打下了良好的基础.     

高温气冷堆核电站蒸汽发生器管板定位机器人

管板定位机器人用于高温气冷堆核电站蒸汽发生器的传热管检修工作。作为堵管工具的载体,搭载各种不同的堵管执行单元,将其引导至指定的工作管孔,实施堵管工序。根据施工需求,开展了管板定位机器人研究。受限于被检对象及施工工况条件,管板定位机器人采用了模块化、轻量化设计。为消除管板定位机器人工作过程中管板结构应力变形、机器人自身运动误差和姿态调整引起的变形误差等因素影响,采用机器视觉辅助定位设计方案,消除上述各种非线性误差影响,提高管板定位机器人的位置控制精度。所设计的机器人样机在蒸汽发生器模拟体上进行了实际测试。结果表明,应用机器视觉技术进行目标定位及运动反馈控制是进行非线性误差补偿的有效手段,该方法控制精度高,控制系统相对简单可靠。     

基于遗传算法的转塔式贴片机贴装过程优化

在转塔式贴片机的贴片过程中,元件贴装顺序和元件在供料槽中的布置是影响转塔式贴片机贴装时间的主要因素.在分析实际工程应用的基础上,建立了转塔式贴片机的集成优化模型,在改进的遗传算法中,提出了一种二维符号编码方法,用元件编号描述元件贴装顺序,用供料槽编号描述元件在供料架中的布置情况,并用元件类型编码实现了两者之间的联系.针对提出的编码方式,采用了基于顺序的交叉和自适应的变异操作,并在算法内采用了并行结构,结合局部搜索策略,实现了元件贴装顺序和供料槽布置可同时优化.与其他方法的比较结果表明,该算法可实现贴装过程的优化,因此提高了印刷电路板的组装效率.     

Characterization of Ordovician carbonate reservoirs, southeastern Saskatchewan, Canada

The discovery of the prolific Ordovician Red River reservoirs in 1995 in southeastern Saskatchewan was the catalyst for extensive exploration activity which resulted in the discovery of more than 15 new Red River pools. The best yields of Red River production to date have been from dolomite reservoirs. Understanding the processes of dolomitization is, therefore, crucial for the prediction of the connectivity, spatial distribution and heterogeneity of dolomite reservoirs.The Red River reservoirs in the Midale area consist of 3～4 thin dolomitized zones, with a total thickness of about 20 m, which occur at the top of the Yeoman Formation. Two types of replacement dolomite were recognized in the Red River reservoir: dolomitized burrow infills and dolomitized host matrix. The spatial distribution of dolomite suggests that burrowing organisms played an important role in facilitating the fluid flow in the backfilled sediments. This resulted in penecontemporaneous dolomitization of burrow infills by normal seawater. The dolomite in the host matrix is interpreted as having occurred at shallow burial by evaporitic seawater during precipitation of Lake Almar anhydrite that immediately overlies the Yeoman Formation. However, the low δ18O values of dolomited burrow infills (-5.9‰～ -7.8‰, PDB) and matrix dolomites (-6.6‰～ -8.1‰, avg. -7.4‰ PDB) compared to the estimated values for the late Ordovician marine dolomite could be attributed to modification and alteration of dolomite at higher temperatures during deeper burial, which could also be responsible for its 87Sr/86Sr ratios (0.7084～0.7088) that are higher than suggested for the late Ordovician seawaters (0.7078～0.7080). The trace amounts of saddle dolomite cement in the Red River carbonates are probably related to "cannibalization" of earlier replacement dolomite during the chemical compaction.     

A computer generator for randomly layered structures

AcomputergeneratorforrandomlylayeredstructuresYUJia shun1,2,HEZhen hua2(1.TheInstituteofGeologicalandNuclearSciences,NewZealand;2.StateKeyLaboratoryofOilandGasReservoirGeologyandExploitation,ChengduUniversityofTechnology,China)Abstract:Analgorithmisintrod…     

海南岛地体及其毗邻陆缘晚中生代—新生代古地磁研究和构造演化

本文叙述了对海南岛及其毗邻大陆边缘白垩纪到第四纪地层岩石进行古地磁研究的全部工作过程。通过分析岩石中剩余磁矢量的磁偏角及磁倾角的变化,提出海南岛白垩纪以来经历的构造演化模式如下:早期伴随顺时针旋转而向南迁移,后期伴随逆时针转动并向北运移。联系该地区及邻区的地质、地球物理资料,对海南岛上述的构造地体运动提出以下认识:北部湾内早期有一拉张作用,主要是该作用使湾内地壳显著伸长减薄,形成北部湾盆地。从而导致了海南岛的早期构造运动,而海南岛后期的构造运动则主要是受南海海底扩张的影响。海南地体运动规律的阐明对于了解北部湾油气盆地的形成演化有重要的理论和实际意义。     

Exciton Seebeck in Molecular Systems

Various applications relevant to the exciton dynamics,such as the organic solar cell,the large-area organic light-emitting diodes and the thermoelectricity,are operating under temperature gradient.The potential abnormal behavior of the exicton dynamics driven by the temperature difference may affect the efficiency and performance of the corresponding devices.In the above situations,the exciton dynamics under temperature difference is mixed with     

Achieving Unusual States of Matter Under High Pressure

The elongation method,originally proposed by Imamura was further developed for many years in our group.As a method towards O(N)with high efficiency and high accuracy for any dimensional systems.This treatment designed for one-dimensional(ID)polymers is now available for three-dimensional(3D)systems,but geometry optimization is now possible only for 1D-systems.As an approach toward post-Hartree-Fock,it was also extended to     

《Chinese Science Bulletin》SUBJECT INDEX TO VOLUME 59(2014)

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An on-line scaling method for improving scalability of a database cluster

The explosive growth of the Internet and database applications has driven database to be more scalable and available, and able to support on-line scaling without interrupting service. To support more client's queries without downtime and degrading the response time, more nodes have to be scaled up while the database is running. This paper presents the overview of scalable and available database that satisfies the above characteristics. And we propose a novel on-line scaling method. Our method improves the existing on-line scaling method for fast response time and higher throughputs. Our proposed method reduces unnecessary network use, i.e. , we decrease the number of data copy by reusing the backup data. Also, our on-line scaling operation can be processed parallel by selecting adequate nodes as new node. Our performance study shows that our method results in significant reduction in data copy time.     

An improved R-tree based on childnode''s probability

R-Tree is a good structure for spatial searching. But in this indexing structure,either the sequence of nodes in the same level or sequence of traveling these nodes when queries are made is random. Since the possibility that the object appears in different MBR which have the same parents node is different, if we make the subnode who has the most possibility be traveled first, the time cost will be decreased in most of the cases. In some case, the possibility of a point belong to a rectangle will shows direct proportion with the size of the rectangle. But this conclusion is based on an assumption that the objects are symmetrically distributing in the area and this assumption is not always coming into existence. Now we found a more direct parameter to scale the possibility and made a little change on the structure of R-tree, to increase the possibility of founding the satisfying answer in the front sub trees. We names this structure probability based arranged R-tree (PBAR-tree).     

Integrating GIS Web services based on mediating architecture

The geographic information service is enabled by the advancements in general Web service technology and the focused efforts of the OGC in defining XML-based Web GIS service. Based on these models, this paper addresses the issue of services chaining,the process of combining or pipelining results from several interoperable GIS Web Services to create a customized solution. This paper presents a mediated chaining architecture in which a specific service takes responsibility for performing the process that describes a service chain. We designed the Spatial Information Process Language (SIPL) for dynamic modeling and describing the service chain, also a prototype of the Spatial Information Process Execution Engine (SIPEE) is implemented for executing processes written in SIPL. Discussion of measures to improve the functionality and performance of such system will be included.     

Tracking data management using topology of moving object database system for moving object constrained trajectory in LBS application

Advances in wireless technologies and positioning technologies and spread of wireless devices, an interest in LBS (Location Based Service) is arising. To provide location based service, tracking data should have been stored in moving object database management system (called MODBMS) with proper policies and managed efficiently. So the methods which acquire the location information at regular time intervals then, store and manage have been studied. In this paper, we suggest tracking data management techniques using topology that is corresponding to the moving path of moving object. In our techniques, we update the MODBMS when moving object arrived at a street intersection or a curved road which is represented as the node in topology and predict the location at past and future with attribute of topology and linear function. In this technique, location data that are corresponding to the node in topology are stored, thus reduce the number of update and amount of data. Also in case predicting the location,because topology are used as well as existing location information, accuracy for prediction is increased than applying linear function or spline function.