Analytical calculation of the envelope surface for generic milling tools directly from CL-data based on the moving frame method

Two closed-form solutions for calculating tool envelope surfaces are proposed based on the moving frame method. They have several advantages: (a) Given a sequence of cutter location (CL) data before post-processing into NC code, although we do not know the special configuration of machine tool, the tool envelope surface can be calculated accurately; (b) The two methods fit for a generic milling tool with a surface of revolution, such as a cylindrical cutter, conical cutter, drum cutter, and so on; (c) Since the calculation is developed based on the representation of the parametric form of the generating curve, it is convenient to use Bézier method, B-Spline or NURBS to unify the representation of the cutters and calculation of tool envelope surfaces. Several examples are presented to prove their effectiveness and good adaptability. The two methods can be used for NC machining simulation, evaluation and correction of the tool path.     

Analysis of improved positioning in five-axis ruled surface milling using envelope surface

This article covers side milling of ruled surfaces using a milling cutter. Flank milling is useful for machining objects such as impellers, turbine blades, fan vanes and all workpieces defined by non-developable, ruled surfaces. In the present article, we first introduce two types of positioning on ruled surfaces developed within the Toulouse Mechanical Engineering Laboratory. The positioning studied is taken from the geometric situation not taking the instantaneous speed of rotation of the milling cutter into account. The swept profile of the tool is then determined based on the tool motion. Having defined the envelope surface, we seek to analyse improved and standard positioning errors comparing envelope surfaces with the ruled surface. We then introduce an example to illustrate positioning developed through a first theoretical study before experimentation including machining and measurement of the test piece. Finally, we give our conclusions as to the validity of improved positioning without taking the instantaneous speed of rotation of the milling cutter into account.     

A comprehensive adaptive approach to calculating the envelope surface of the digital models in CNC machining

The digital models are the fundamental elements used in the virtual simulation of CNC machining for process planning, result prediction, analysis, etc. The essential work to build the digital models of machined parts is the calculation of the envelope surface generated by moving a cutter surface relative to workpieces. This calculation is usually complicated, and the requirements in different cases are also varied. Hence, it is very beneficial to develop an effective approach for different requirements. In this work, a comprehensive envelope approach is established, and it adaptively choose 1) the elimination parameter among two cutter surface parameters, 2) the representation form of envelope surface, and 3) the discretization way, so it is robust to satisfy different requirements. The elimination parameter and representation form are adaptively chosen to improve the calculation efficiency by obtaining the closed-form representation of the envelope surface prior to the implicit one. The discretization way is further adaptively chosen to obtain approximately even point distribution to the applications of 3D and FEA modeling. Finally, comprehensive algorithms are proposed to effectively implement this adaptive envelope approach for different applications. The examples are given to the manufacturing of spiral bevel gears and five-axis CNC milling.     

Optimize tool paths of flank milling with generic cutters based on approximation using the tool envelope surface

This paper presents a global optimization method to generate a tool path for flank milling free-form surfaces with a generic cutter based on approximation using the tool envelope surface. It is an extension of our previous work [Gong Hu, Cao Li-Xin, Liu Jian. Improved positioning of cylindrical cutter for flank milling ruled surfaces. Computer Aided Design 2005; 37:1205–13]. First, given initial tool path or tool axis trajectory surface, the grazing points of the tool envelope surface can be calculated. Second, the errors between the tool envelope surface and the designed surface along the normal direction of the tool envelope surface are calculated. Based on this new definition of error, an optimization model is established to get the global optimized tool axis trajectory surface. In order to simplify the calculation, two variants of this method based on the least square criterion are proposed to solve this model. Since this method is really based on the tool envelope surface, it can reduce the initial machining errors effectively. The proposed method can be used not only for cylindrical cutters and conical cutters, but also for generic cutters with a surface of revolution. In addition to ruled surfaces, it also can be used for machining non-ruled surfaces. Finally, several examples are given to prove its effectiveness and accuracy. The generated tool paths and calculated grazing points for test are available in supplementary files for the readers’ convenience in verifying this work in different CAD/CAM systems.     

基于肤色与模板匹配的人脸检测方法研究

利用肤色信息在彩色图像中检测人脸速度快、易于实现,但准确率不高。本文提出首先应用人脸肤色信息在彩色图像中进行人脸粗略检测,得到候选人脸区域,再以基于梯度模板匹配的方法进行人脸精确定位,从候选区中准确地找到人脸。将这两种方法结合在保证精确的人脸检测的前提下,可有效提高检测速度。     

基于知识模板的产品建模方法

为实现产品概念设计的创新,提出功能模板、行为模板和结构模板的概念,并利用三者之间的映射关系实现行为流产品建模.通过行为流建模的具体算法,在实现产品概念模型设计的同时生成该模型的行为路径.发动机模型的创建实例表明,该算法能实现产品概念模型设计的再创新.     

A response surface based optimisation algorithm for the calculation of fuzzy envelope FRFs of models with uncertain properties

This paper describes a response surface based optimisation technique for the calculation of envelope frequency response functions (FRFs) of imprecisely defined structures using the interval and fuzzy finite element method.The authors developed a hybrid - global optimisation and interval arithmetic - procedure for interval and fuzzy envelope FRF calculation. This hybrid approach reduces the computational cost of the analysis compared to a full global optimisation approach and reduces the conservatism on the envelope FRF compared to a full interval arithmetic approach.Still, the optimisation step is the computationally most expensive part of the algorithm. To handle industrially sized applications, a very efficient optimisation procedure is imperative. The response surface based procedure described in this paper decreases the computational cost of a fuzzy envelope FRF calculation with a factor 50 or more compared to the commonly used two-level full factorial design of experiments, while giving a comparable accuracy.     

基于比值法和模板匹配法的灰度图像拼接

提出一种改进的基于比值法和模板匹配法的灰度图像拼接算法。对两幅具有重叠区域的灰度图像，先通过设置拼接参数对话框，在另一幅图像中找到最佳匹配点，最后利用平滑因子对两幅图像的重叠区域进行数据融合操作，实现了灰度图像的快速自动拼接。实验证明．该方法对大部分灰度图像具有很好的拼接效果。     

基于模板替换的室内场景建模方法研究

当前,室内场景建模相关研究已经取得很多进展,特别是基于多视角融合的建模 框架与基于单视角的建模框架的提出,增强了机器人的环境感知能力。但仍然存在以下不足： ①基于多视角融合的建模方式预处理时间长,建模完成后需线下优化过程,不能满足特定条件 下的建模需求;②基于单视角的建模算法输出一般为体素,建模质量较低,信息缺失严重,对 于场景细节无法精确刻画,难以满足机器人交互的要求。特提出一种基于模板替换的室内场景 建模方法研究。首先,预处理由设备采集到的三维点云场景,分割出存在点云缺失的单个对象, 并利用虚拟扫描技术采样对象表面点并计算法向量与曲率。采用八叉树网格结构,将点云的法 向量与曲率信息分别存入网格中,再利用卷积神经网络(CNN)提取高维特征向量,将其与数据 库中三维对象特征进行欧氏距离比较,得到检索序列。从序列中挑选出最相似的对象,利用迭 代就近点(ICP)配准方法,与扫描场景进行配准,完成场景优化。对提出的网络模型在 2 个基准 数据集上进行测试并表现出良好的性能。     

Tool path deformation in 5-axis flank milling using envelope surface

This paper deals with assessment and correction of tool path in 5-axis machining. The tool trajectory is described using two curves; each one corresponding to the trajectory of two particular points of the tool axis. The assessment of the tool path is performed via the calculation of the envelope surface, which is calculated using a kinematics approach. The geometrical deviations between the envelope surface and the nominal surface are calculated. When necessary, the tool path is corrected, so that the envelope surface fits the ideal surface as much as possible. This correction is carried out by the deformation of both curves that are representative of the tool trajectory. We choose to illustrate our purpose through flank milling of sculptured surfaces.     

A novel envelope model based on convex constrained optimization

The concept of envelope has been used widely in signal analysis. However a good mathematical definition of suitable envelope remains an issue. In this paper, we present a novel model to estimate the envelope of a signal by using the convex constrained optimization. This model is based on the commonly accepted knowledge about envelope which makes it coincide with the geometric envelope of the signal. The envelope based on the new model is smooth and has no undershoots. Experiments comparing with the existing typical models of envelope are also implemented and discussed.     

插值Doo-Sabin表面形状调节

修改了插值的Doo-Sabin细分表面的初始控制网格，在第一次细分的同时加入了表面调节参数。这个方案具有以下特征：1）满足插值所有顶点或某些顶点的同时可以由参数调节极限表面；增加了对极限表面的调节自由度。2）整个的计算复杂度为O(k),其中k是顶点的数量。在最后也对结果表面的形状处理进行了讨论。     

A clustering method for automatic biometric template selection

The problem addressed in this paper is the template selection and update in biometrics based on clustering. Template selection is a reliable method to reduce the number of templates used in a biometric system to account for variations observed in a person's biometric data. An efficient method based on clustering with automatic selection of the number of clusters is proposed in this work for finding subgroups of similar templates which are used for prototype selection.Experimental results confirm the advantage of the new method and the importance of adopting a procedure to perform template selection.     

基于模板的模块化设计方法

为了尽量减少软件人员的重复劳动,文章提出了基于模板的模块化程序设计方法。该方法已成功应用于湖南建行的软件开发工作中。     

B样条曲面的双向插值造型算法

基于Coons-Gordon造型原理,研究了插值两族相交截面线采样点的B样条曲面双向插值造型算法。参数化各采样点并计算每条截面线的节点矢量,估算每条截面线对应的曲面参数,根据每条截面线的节点分布以及另一族截面线对应的曲面参数统一节点矢量。分别插值两族截面线采样点及其公共点得到三张B样条曲面,其布尔和即为插值两族截面线采样点的B样条插值曲面。实例表明,得到的双向插值曲面控制顶点数少,光顺性好。     

基于二次Bezier曲面的图像雕刻型面建模

针对纹理清晰且结构较简单的图像,依据其灰色或彩色像素信息,利用二次Bezier曲面直接构建雕刻型面模型。该方法通过对图像进行分割,分析和计算图像子块的像素值及位置参数,作为构建模型曲面片的特征参数,并对曲面片采用一种有限光滑拼接方法实现建模。构建的雕刻型面模型能够表述图像中原物体的基本结构特征,并能满足数字化雕刻加工的需要。算法复杂度较低,实用性强是该建模方法的特点。     

Ranking highlight level of movie clips: A template based adaptive kernel SVM method

This paper looks into a new direction in movie clips analysis – model based ranking of highlight level. A movie clip, containing a short story, is composed of several continuous shots, which is much simpler than the whole movie. As a result, clip based analysis provides a feasible way for movie analysis and interpretation. In this paper, clip-based ranking of highlight level is proposed, where the challenging problem in detecting and recognizing events within clips is not required. Due to the lack of publicly available datasets, we firstly construct a database of movie clips, where each clip is associated with manually derived highlight level as ground truth. From each clip a number of effective visual cues are then extracted. To bridge the gap between low-level features and highlight level semantics, a holistic method of highlight ranking model is introduced. According to the distance between testing clips and selected templates, appropriate kernel function of support vector machine (SVM) is adaptively selected. Promising results are reported in automatic ranking of movie highlight levels.     

基于伸缩因子的代数曲线曲面变形方法

提出了一种基于伸缩因子的代数曲线曲面变形方法。首先构造了一种用于代数曲线曲面变形的伸缩因子,然后将所构造的伸缩因子分别作用于待变形的代数曲线与曲面,通过改变伸缩因子各参数的取值实现对代数曲线曲面的变形。实例表明,该方法操作方便,易于控制,可获得丰富的变形效果,是一种简单有效的代数曲线曲面变形方法。     

基于四边形网格的可调细分曲面造型方法

提出了一种基于四边形网格的可调细分曲面造型方法。该方法不仅适合闭域拓扑结构，且对初始网格是开域的也能进行处理。细分算法中引入了可调参数，增加了曲面造型的灵活性。在给定初始数据的条件下，曲面造型时可以通过调节参数来控制极限曲面的形状。该方法可以生成C1连续的细分曲面。试验表明该方法生成光滑曲面是有效的。     

基于曲面建模的三维地质体体绘制研究

体绘制技术因为其相对于面绘制技术能够更好地反映三维体的真实结构,因而越来越受到人们的重视.提出了一种基于曲面建模的地质体体绘制方法,并在此基础上引入原始钻孔点的穷举搜索来获得散乱点以生成曲面.并根据现场数据的特征采用了适合中小型数据量插值拟合计算的改进谢别德插值来实现曲面的生成.产生曲面之后,使用了现在被普遍采用的基于图像空间序的光线投射算法完成地质体的体绘制,并在此基础上实现了剖切,缩放等三维体的交互操作.