犁臂三维几何模型逆向工程研究

介绍了逆向工程的基本概念,基于RE技术上的三维建模方法:数据采集、点云数据处理、三维模型重建。并以犁臂的三维重构过程为实例———利用ATOS光学扫描仪对犁臂表面进行扫描,获取三维点云数据。将测量的点云数据用Imageware软件进行处理后,再利用UGNX软件的曲面造型功能,实现犁臂的三维模型重构,最后对三维模型的精度进行了检测。说明在产品设计中利用数字化逆向工程技术,可大大缩短产品的开发周期,对快速响应市场产生显著效果。     

机械装备零件逆向建模中的数据处理技术应用

以机械装备零件中的滤清器上盖为研究对象,针对关节臂式三维激光扫描仪的特点,介绍了逆向工程中的数据测量方法,分析了影响测量精度的因素。基于非接触式测量点云数据的特征,从多视拼合、噪声去除、数据精简、数据平滑等方面对点云数据处理方法进行了研究,并提出有针对性的处理措施加以改善。最后对点云数据进行了基于Imageware软件的模型坐标系建立以及基于Geomagic Studio软件的零件曲面重建,为探索逆向工程在机械装备零件模型重建中的应用提供技术借鉴。     

逆向工程中点云特征提取技术研究

点云数据的特征提取是逆向工程领域中的一项重要研究内容,为几何分析、数据分割、曲线匹配和拼接、曲面重建等几何处理提供依据,对后期精确的点云配准、模型重建等研究起关键作用。重点研究分析了基于法向量、曲率点特征直方图PFH和快速点特征直方图FPFH等不同点云特征描述参数的点云特征提取技术,为后续的研究和改进形成新的设计思路提供参考。     

Imageware中光滑拼接曲面的方法

逆向工程软件的曲面反求中,曲率较大的地方往往难以得到较好的曲面反求效果,针对该问题提出了一种基于曲率变化的分块曲面构建拼接方法.该方法根据曲率显示的点的颜色特征进行点云数据的分割,分别获得单片光滑曲面,然后将单片曲面拼接起来以实现完整的自由曲面造型.在曲面拼接过程中,调整两片曲面相邻两列控制点,使其三点共线,以达到拼接处一阶连续.最后通过一个典型的实例证明该方法构造的曲面与原始点云的最大误差为由点阵直接拟合生成的曲面误差的1/3,为由点-线-面构造的整块曲面误差的1/5.     

采用Imageware与CATIA的三维曲面重建与数控仿真加工

三维曲面建模和数控加工是产品制造的关键,采用逆向工程与正向加工技术相结合,以解决复杂型面难以建模和加工的问题。首先采用正弦光栅投影仪获取被测型面的光栅图像,通过解相和相位展开获取物体三维点云数据,然后根据点云曲率对点云数据进行分区,采用Imageware进行单个曲面拟合和多曲面拼接,实现整体曲面重建,点云-曲面最大偏差为0.264 mm。最后,利用CATIA软件设计出三维曲面凸模及凹模,通过计算刀路轨迹,产生数控加工程序,完成数控仿真加工过程。     

Imageware中光滑拼接曲面的方法

逆向工程软件的曲面反求中,曲率较大的地方往往难以得到较好的曲面反求效果,针对该问题提出了一种基于曲率变化的分块曲面构建拼接方法。该方法根据曲率显示的点的颜色特征进行点云数据的分割,分别获得单片光滑曲面,然后将单片曲面拼接起来以实现完整的自由曲面造型。在曲面拼接过程中,调整两片曲面相邻两列控制点,使其三点共线,以达到拼接处一阶连续。最后通过一个典型的实例证明该方法构造的曲面与原始点云的最大误差为由点阵直接拟合生成的曲面误差的1／3,为由点一线一面构造的整块曲面误差的1／5。     

基于点云数据的逆向工程技术研究综述

在介绍了逆向工程的定义、逆向工程的流程及应用的基础上,综述了点云数据测量、数据预处理和模型重构的研究现状。首先介绍了点云数据测量方法的分类,然后重点分析了点云数据拓扑关系建立的方法及K近邻域索引的研究,多视点云数据拼合的点位法、固定球法、优化匹配法、特征匹配法及辅助装置法的研究,滤波去噪的方法,孔洞修复的原理,数据精简的方法,特征提取和曲面重建的基本思想和研究成果,最后展望了逆向工程技术的发展方向。     

逆向工程在复杂曲面重构中的应用研究

分析和研究了逆向工程在零件曲面复杂的情况下重建模型的关键技术问题。将整个逆向工程分为数据点云扫描、点云数据封装处理和参数化曲面重构三个模块,针对各模块不同的功能和特性加以论述和分析。以某音响结构件为例,着重论述了复杂曲面重建中的一些重要步骤并给出了解决方案,最后得到了逆向工程的整体参数化曲面模型。     

大型复杂零件反求软件开发及功能实现

在大尺寸复杂零件反求设计实际应用过程中,往往需要正向设计软件能够直接处理点云数据而逆向设计软件能够直接进行参数化实体造型。针对这一实际工程需要,对点云数据获取与预处理、多视测量与数据拼接、复杂曲面特征提取与重构等理论和方法进行研究,以VC++6.0为开发工具,借助UG/OPENAPI平台开发了RETOOL反求系统;该系统可内嵌于UG NX系统,实现了正向设计软件能够直接处理点云数据的功能;以风机叶片等零件为应用实例详细阐述了RETOOL系统用户界面、点云数据获取、特征点提取和特征曲线拟合等模块开发过程。     

多视点云数据快速对齐方法

多视点云数据的对齐(拼接)问题是逆向工程研究的热点问题之一。在ICP算法的基础上,提出通过在数据测量时放置基准物体,建立点云数据对齐特征,在进行多视点云数据拼接时对对齐特征增加约束的方法,实现多视点云数据的快速对齐。并对基于三个基准点约束对齐的对齐精度进行了分析,提出了减少对齐误差的措施,最后通过实例对研究结果加以分析验证。     

Minimal Realization of Linear Graph Models for Multi-physics Systems

An engineering system may consist of several different types of components,belonging to such physical"domains"as mechanical,electrical,fluid,and thermal.It is t...     

Quantum Cooperative Robotics and Autonomy

The intersection of Quantum Technologies and Robotics Autonomy is explored in the present paper.The two areas are brought together in establishing an interdisci...     

考虑进油孔有限长滑动轴承油膜力的近似解析解

针对具有进油孔的有限长滑动轴承油膜力求解问题,采用变分原理和分离变量法,求得了有限长滑动轴承油膜压力分布的近似解析表达式。将油膜压力分布的近似解析表达式在油膜存在区域上进行积分,即得到了油膜力。将提出的计算有限长滑动轴承油膜力方法与无限长轴承模型、有限元方法的计算结果进行了比较,发现了提出的方法与有限元方法的计算结果很接近。最后,研究了进油孔位置和进油压力对油膜存在区域、油膜力等的影响,研究结果表明进油孔位置和进油压力对油膜存在区域和油膜力有较大的影响。     

三绕组变压器的双绕组等效建模及在Matpower中的应用

针对实际电网存在着大量的三绕组变压器,但国际上一些著名商业软件,如BPA仿真软件、Matpower这一权威潮流计算开源软件,均只提供双绕组变压器模型,限制了其在具有三绕组变压器的电力系统中的应用的问题,潮流计算是自主开发的电力系统各种应用软件的核心模块,因此依托国际权威开源程序进行二次开发,是一种较好的选择。对Matpower要求的数据格式进行了归纳,对变压器的一般的等值电路及带理想变压器的等值电路和带标幺值的等值电路进行了分析研究,提出了三绕组变压器转换为双绕组等效模型的建模方法,使得原先只适应双绕组变压器的潮流计算软件可以适用于三绕组变压器电网的潮流计算;最后以Matpower软件为例进行了案例计算,并用PSASP仿真软件进行对比验证。研究结果证明,所提出的建模方法是有效的。     

On the Relation of Load to Average Gap in the Contact Between Surfaces with Longitudinal Roughness

A computer simulation model for the contact between longitudinally-oriented rough surfaces has been formulated. This model closely duplicates the actual surf ace contact deformation behavior by taking into account the elastic interactions between the asperities. There were no assumptions made about the shapes, or any deformation behavior of the asperities, except for their obeying the laws of elasticity. The plastic deformations on the high asperity peaks were taken into account by setting a ceiling on their contact pressures at the material hardness value. The simulations used real surface profiles which were digitized from unworn circumferentially ground steel surfaces. Each pair of these profiles was mathematically combined to form an equivalent rough profile pressing against an infinitely rigid flat and having the appropriately adjusted elastic modulus. A total of 28 different pairs of profiles were used in the simulations. Each contacting pair was subjected to 30 different load levels and the local contact pressures and deformations were calculated. The contact simulations yielded some important mathematical relationships between parameters, such as the real area of contact, average gap, and average asperity load through statistical curve fitting. Two analytical functions were generated to relate the average load to average gap and the real area of contact to load.     

INTEGRAL EQUATION METHOD＇S APPLICATION IN HOLE-EDGE STRESS OF COMPOSITE MATERIAL PLATE WITH DIFFERENT SHAPED HOLES

The strength of composite plate with different hole-shapes is always one of the most important but complicated issues in the application of the composite material. The holes will lead to mutations and discontinuity to the structure. So the hole-edge stress concentration is always a serious phenomenon. And the phenomenon makes the structure strength decrease very quickly to form dangerous weak points. Most partial damage begins from these weak points. According to the complex variable functions theory, the accurate boundary condition of composite plate with different hole-shapes is founded by conformal mapping method to settle the boundary condition problem of complex hole-shapes. Composite plate with commonly hole-shapes in engineering is studied by several complex variable stress fimction. The boundary integral equations are founded based on exact boundary conditions. Then the exact hole-edge stress analytic solution of composite plate with rectangle holes and wing manholes is resolved. Both of offset axis loadings and its influences on the stress concentration coefficient of the hole-edge are discussed. And comparisons of different loads along various offset axis on the hole-edge stress distribution of orthotropic plate with rectangle hole or wing manhole are made. It can be concluded that hole-edge with continuous variable curvatures might help to decrease the stress concentration coefficient; and smaller angle of outer load and fiber can decrease the stress peak value.     

Fifth International Summer School on Screw-Theory Based Methods in Robotics

正3-11 September,2014University of Bologna,Bologna,Italy www.summerscrews.org summerscrews2014.ing.unibo.it SUMMER 20SCREWS 14In 2014,our screw-theory school comes to the world's oldest university.In early September,Summer Screws'14 will gather six experts in the application of screw theory in robotics and up to 40 participants at the University of Bologna,Bologna,Italy.The school will teach attendees how to apply existing methods and empower them to develop new ones in their own research.The basic theoretical notions will be introduced in a rigorous manner,emphasizing examples,applications,and exercises.Scholarships are available.     

电站锅炉模糊风险评价方法研究与应用

针对电站锅炉风险等级评价问题,将模糊综合评价技术应用到电站锅炉风险等级评价中。开展了电站锅炉失效影响因素及模糊评价因素的重要程度分析,建立了一套科学合理适于在线评价的电站锅炉风险评价体系,提出了模糊综合评价技术与改进的模糊层次分析法相结合的模糊风险评价方法,利用改进的模糊层次分析法计算了指标体系中各层指标权重。对某一台电站锅炉的实际运行工况影响子因素进行了模糊风险评价,采用模糊合成算子进行模糊综合运算得到电了站锅炉运行工况影响子因素的评价向量。研究结果表明:电站锅炉的运行工况影响子因素的风险评价等级为第6级,失效可能性等级为小,该电站锅炉运行工况良好。     

INDUSTRIAL ENGINEERING AND VISUALISATION-A PRODUCT DEVELOPMENT PERSPECTIVE

Taking the actual project of teaching and researching process for example, the relationship between the industrial engineering and product development is discussed. And use the novel visualization technology to support the industrial engineering and product development. How to use the new computer modeling and simulating technologies to support the product development and industrial engineering, is introduced especially. The support includes both domestic products and industrial systems. The visualization and computer technologies take a very important role in some system or multi-direction modeling, those technologies mentioned above can help the industrial engineers study the effect of design on the whole life circle, including the producing steps. So the engineers can avoid making the wrong decision which may cause bad effects on the whole industrial engineering.     

Non-monotonic material contrast in scanning ion and scanning electron images

30 keV Ga⁺ focused ion beam induced secondary electron (iSE) imaging was used to determine the relative contrast between several materials. The iSE signal compared from C, Si, Al, Ti, Cr, Ni, Cu, Mo, Ag, and W metal layers does not decrease with an increase in target atomic number Z₂, and shows a non-monotonic relationship between contrast and Z₂. The non-monotonic relationship is attributed to periodic fluctuations of the stopping power and sputter yield inherent to the ion–solid interactions. In addition, material contrast from electron-induced secondary electron (eSE) and backscattered electron (BSE) images using scanning electron microscopy (SEM) also shows non-monotonic contrast as a function of Z₂, following the periodic behavior of the stopping power for electron–solid interactions. A comparison of the iSE and eSE results shows similar relative contrast between the metal layers, and not complementary contrast as conventionally understood. These similarities in the contrast behavior can be attributed to similarities in the periodic and non-monotonic function defined by incident particle–solid interaction theory.