虚拟加工中心加工过程算法研究

在虚拟加工环境的建造过程中，关键技术是三维实体的数据结构和加工仿真的逐步成型算法。该文重点研究了毛坯的数据结构特点，四边形离散化方法和毛坯文件的存储格式等，并且分析了三坐标加工中心的加工特点，同时还给出了虚拟加工过程中毛坯被加工成工件的逐步成型算法。该算法在虚拟加工环境中得到了成功应用，文中给出了该算法在三坐标加工中心的验证实例。     

一种非圆齿轮虚拟插齿加工建模及切屑方法研究

非圆齿轮因其节曲线为非圆形,加工过程复杂,加工仿真困难。针对一种非圆齿轮的加工,实现了从毛坯到成品的虚拟插齿过程仿真,即按照事先编制的G代码(即数控程序),驱动虚拟插床有序去除虚拟毛坯材料。通过对毛坯模型进行离散化,在切割过程中不断从场景中移除切屑材料节点实现加工仿真;通过树状场景图结构搭建虚拟加工环境;数控插齿加工过程复合运动的协调运作,实现了基于G代码的加工过程运动仿真。采用Visual Studio 2008作为开发平台,结合OSG(open scene graph)图形库,再现了加工中工件的成型过程,为产品加工过程提供了有益的参考。     

基于动态局部更新体素模型的虚拟加工仿真算法研究

为提高虚拟加工仿真算法的仿真速度和精度,提出一种新的基于动态局部更新体素模型的虚拟加工仿真算法.该算法利用体素节点间的邻接关系,实现虚拟加工仿真的动态局部更新.算法在初始化阶段建立虚拟毛坯的八叉树结构体素模型,并建立任意体素6-邻接关系遍历算法.在虚拟加工几何仿真阶段,利用刀具和毛坯相对运动的时空一致性,从毛坯上一帧已...     

数控车仿真软件中毛坯和工件坐标系仿真模型的建立

本文介绍了一种二维数控车仿真软件中毛坯和工件坐标系仿真模型建立的算法,文中仿真软件开发环境为C#. 在现今微课、慕课和信息化课程流行的年代,数控课程使用仿真软件教学越来越频繁,很多的教师更愿意使用自己开发的简易数控仿真软件来进行教学.下面我将介绍一种在C#环境下数控车仿真软件中毛坯和工件坐标系仿真模型的建立方法.     

综合运用CAXA、Pro/ENGINEER和ANSYS优化设计齿轮

本文针对ANSYS软件计算分析能力强,建立齿轮模型困难的情况,采用CAXA软件绘制齿轮平面图,用Pro/ENGINEER软件生成三维立体模型,并通过IGES文件导入ANSYS软件进行分析、计算、优化.     

基于形状先验模型的平面型工件抓取位姿检测

为了能够在复杂的工业环境中抓取平面型工件,提出一种图割法与形状先验模型结合的工件图像分割方法,并且对工件的位姿信息进行测量.首先,建立先验形状,提出基于最小包围矩形法将工件的形状模板与目标工件人工分割形状进行配准,得到先验形状.为了保证分割结果的准确性,采用单一的先验形状.图割模型中加入了目标形状先验知识.其次,通过自适应调整形状先验项的权重系数,使得图割法的能量函数形状先验项自适应于被分割的图像.第三,本文可以采用形状先验方法分割一幅图像中的多个工件,并且能够计算吸盘的最优抓取位置.最后,采用结构光视觉系统采集工件的点云信息,拟合工件平面,确定工件法向量,得到工件的抓取姿态.实验结果表明,本文算法能够适应遮挡、光照变化的工件图像,同时也能够分割复杂环境中的目标工件;平面型工件抓取位姿的计算结果有效,可以应用于遮挡、反光、复杂干扰背景条件下的工件抓取作业.     

虚拟切削加工系统的设计与实现

虚拟制造是近年出现的一种先进制造技术,虚拟切削加工在虚拟制造中占有重要地位。为了提供虚拟的加工环境和验证工艺设计的正确性,对切削加工过程的计算机仿真方法进行了研究,以OSG作为图形支持系统,用VC++开发了切削加工仿真系统。该系统实现了对毛坯切割的仿真,可对刀具运动切割情况进行实时监控,较好的再现了加工中毛坯的成型过程。     

虚拟砂轮的开发及其磨削性能分析

采用虚拟现实技术,开发了可交互的虚拟磨削加工环境．以正六面体作为磨粒的基本形态,并将该磨粒随机分布在砂轮基体上,建立虚拟砂轮的仿真物理模型以及磨粒与工件接触的数学模型．以平面磨削为例,进行了不同加工参数下磨削加工过程的动态仿真,测试了虚拟砂轮的磨削性能,并分析了工件表面粗糙度的影响因素．仿真结果与理论分析结果具有一致性,证明了将虚拟现实技术应用于磨削加工机理研究是可行的．     

解析EdgeCAM的创新思维——模型篇

一、模型来源不同 很多人已经习惯了使用"IGES"格式的文件,在不同的CAD/CAM环境下进行传递.由于这种文件格式具有的天生的缺陷,从而造成了很多模型缺失的现象,在CAM环境下,第一件要做的事情就是"修补模型".     

单元重构问题探讨

在 CIMS 环境下,采用虚拟单元技术可以解决使用成组单元的结构中出现的过量跨单元加工和加工负荷不平衡问题.本文对实现虚拟单元的关键技术——单元重构的可行性进行了分析,对单元重构的两个主要过程,即任务的时间分解过程和任务的空间分解过程进行了详细的讨论,并对所涉及到的时间划分、计划调度、工件、机器成组等问题给出了相应的策略和算法.从而证明了在 CIMS 环境下实现虚拟单元的可行性.     

三维虚拟加工环境及其关键技术的研究

在分析虚拟制造特点的基础上,提出了三维可视化虚拟加工环境的系统结构,介绍了支持三维建模仿真的组件设计、基于装配模型的三维实体建模方法、NC代码解析器的设计方案以及基于毛坯表面三角片离散化的加工过程仿真算法,并开发了虚拟加工环境原型系统,该系统能够实时地反映零件虚拟原型的加工成形过程仿真,并进行可加工性分析。     

基于IGES接口的电磁计算模型数据交互

现今武器大多是利用非均匀有理B样条(non-uniform rational B-spline,NURBS)数学表述,在CAD/CAM系统下完成建模和重构.利用电磁计算软件运算武器模型的雷达散射截面(radar cross section,RCS)从而评估其隐身性能,就需要与CAD/CAM系统进行数据交互.通过对基本图形转换规范(initial graphics exchange specification,IGES)数据标准的分析,为电磁计算软件编译了IGES数据接口.该数据接口具备IGES文件数据导入和模型数据导出另存为IGES文件格式的功能,从而实现了自行开发的计算软件CRCS v1.2和CAD系统软件的数据交互,提高了软件处理复杂模型的能力进而使模型重构与计算趋于一体化.     

Isogeometric analysis with trimming technique for problems of arbitrary complex topology

Trimming technique is a powerful and efficacious way of endowing an arbitrary complex topology to CAD files created by using NURBS. In the present work, it is shown that any complex multiply-connected NURBS domain can be described by using trimming curves only. Isogeometric analysis for linear elasticity problems of complex topology described in this way is presented. For fully communicative interaction between CAD and CAE, a specific searching algorithm and an integration scheme of trimmed elements are introduced to utilize the IGES files exported from CAD system for Isogeometric analysis. Schemes for imposing essential and traction boundary conditions on trimming curves are presented. It has been demonstrated that with the presented schemes trimmed cases in any complicated situations can be successfully treated. With the examples of complex topology that could be described by employing trimming curves only, effectiveness and robustness of present method are demonstrated.     

A Data-drivenParameter Planning Method for Structural Parts NC Machining

Structural parts are generallyused to compose the main load-bearing components in various mechanical products, and are usuallyproduced by NC machining where the machining parameters heavily determine the final production quality, efficiency and cost. Due to the complex structures and high precision requirements, a large amount of human interactions are usually required to modify the machining parameters generated by existing optimisation model-based or expert system-based methods, which will induce unstable machining quality and low efficiency. This paper proposes a data-driven methodfor machining parameter planning by learningthe parameter planning knowledge from thehigh-qualityhistorical processing files. An attribute graph is first defined to represent the part model. Then for each of the machining operations in the historical processing files, the machining parameters are correlated to a sub-graph that refers to the faces to be machined in this operation. By this way, a graph dataset of machining parameters could beconstructed from the historical processing files, and graph neural networks (GNN) are established to learn the planning models for machining parameters. The proposed method provides an end-to-end strategy for constructing machining parameter planning models thus human interactions can be greatly reduced and the performance of the models are able to be improved as the increase in historical processing files. In the case study, the historical processing files of aircraft structural parts machining are used to train the GNN models for planning cutting width, cutting depth and machining feedrate, and the prediction accuracies reach 95.50%, 94.79%, 95.02% respectively.     

基于OpenGL的雕塑建模与可视化仿真

文章是在OpenGL的虚拟现实技术和VC＋＋2008编程技术以及3DMAX建模技术上进行研究的。3DMAX建模软件对雕塑模型进行创建与绘制。导出aDS格式的文件,在VC＋＋2008支持的OpenGL环境下对雕担模型进行读取与控制。基本实现了雕塑可视化模拟,达到了较逼真的雕塑三维可视化效果。     

飞行器几何数据库与CAD软件数据交换问题研究

飞行器几何数据入库的关键,是在对图形文件结构分析研究的基础上,开发出CAD软件的图形数据和数据库之间的接口程序,使得图形数据和数据库数据可以自由交换。论文研究了IGES文件格式和DXF文件格式的详细结构,开发出具有IGES文件和DXF文件入库与出库功能的飞行器几何数据库管理系统软件。     

Fast character modeling with sketch-based PDE surfaces

Virtual characters are 3D geometric models of characters. They have a lot of applications in multimedia. In this paper, we propose a new physics-based deformation method and efficient character modelling framework for creation of detailed 3D virtual character models. Our proposed physics-based deformation method uses PDE surfaces. Here PDE is the abbreviation of Partial Differential Equation, and PDE surfaces are defined as sculpting force-driven shape representations of interpolation surfaces. Interpolation surfaces are obtained by interpolating key cross-section profile curves and the sculpting force-driven shape representation uses an analytical solution to a vector-valued partial differential equation involving sculpting forces to quickly obtain deformed shapes. Our proposed character modelling framework consists of global modeling and local modeling. The global modeling is also called model building, which is a process of creating a whole character model quickly with sketch-guided and template-based modeling techniques. The local modeling produces local details efficiently to improve the realism of the created character model with four shape manipulation techniques. The sketch-guided global modeling generates a character model from three different levels of sketched profile curves called primary, secondary and key cross-section curves in three orthographic views. The template-based global modeling obtains a new character model by deforming a template model to match the three different levels of profile curves. Four shape manipulation techniques for local modeling are investigated and integrated into the new modelling framework. They include: partial differential equation-based shape manipulation, generalized elliptic curve-driven shape manipulation, sketch assisted shape manipulation, and template-based shape manipulation. These new local modeling techniques have both global and local shape control functions and are efficient in local shape manipulation. The final character models are represented with a collection of surfaces, which are modeled with two types of geometric entities: generalized elliptic curves (GECs) and partial differential equation-based surfaces. Our experiments indicate that the proposed modeling approach can build detailed and realistic character models easily and quickly.

     

Automesh for trimmed surface entity of IGES/PDES

IGES/PDES is an internationally accepted standard protocol for transferring the information of a two-dimensional or three-dimensional model between different CAD/CAM software. Any solid model can be constituted by a number of surfaces. Trimmed surface is one of the most important entities used to design a two-dimensional or three-dimensional model in IGES/PDES. The main idea in this article is to extract trimmed surface entity information from an IGES protocol created in a CAD/CAM software. Then, from the extracted information of trimmed surface entity in the model space and in the u–v space, a new u–v space is developed for meshing. After meshing the geometric region in the new u–v space, the meshed geometric region is transformed back to the model space by using a particular transformation. A Fortran code which can be used for pre-processing in Boundary Element Method has been developed by the present authors. Some meshed surface models are presented in this paper as examples.     

A study on three-dimensional vision system for machining setup verification

In computerized numerical control (CNC) machine tools, it is often a time-consuming and error-prone process to verify the Euclidean position accordance between the actual machining setup and its designed three-dimensional (3D) digital model. The model mainly contains the work piece and jigs. The mismatch between them will cause a failure of simulation to precisely detect the collision. The paper presents an on-machine 3D vision system to quickly verify the similarity between the actual setup and its digital model by real and virtual image processing. In this paper, the system is proposed first. Afterwards, a simple on-machine camera calibration process is presented. This calibration process determines all the camera's parameters with respect to the machine tool's coordinate frame. The accurate camera mathematical model (or virtual camera) is derived according to the actual imaging projection. Both camera-captured real images and system-generated virtual images are compensated to make them theoretically and practically identical. The mathematical equations have been derived. Using the virtual image as a reference and then superimposing the real image onto it, the operator can intuitively verify the Euclidean position in accordance to the actual setup and its 3D digital model.