An improved feedrate scheduling method for NURBS interpolation in five-axis machining

Five-axis machining plays an important role in manufacturing by dint of its high efficiency and accuracy. While two rotation axes benefit the flexibility of machining, it also brings limitations and challenges. In order to further balance machining precision and efficiency, an improved feedrate scheduling method is presented considering geometric error and kinematic constraints for the Non Uniform Rational B-Spline (NURBS) interpolation in five-axis machining. A simplification method is proposed to calculate the geometric error which describes the deviation between the ideal tool path and the real tool path induced by the non-linear movement. A linear relation between geometric error and feedrate is built to limit the feedrate. The constraints determined by single axis kinematic performance and tangential kinematic performance are also considered. Under these constraints, a constrained feedrate profile is determined. Aiming to get more constant feedrate in the difficult-to-machine areas, this work proposes a scheduling method which combines morphological filtering and S-shape acceleration/deceleration (acc/dec) mode. Simulations and experiments are performed to compare the proposed feedrate scheduling method with two previous feedrate scheduling method and the results prove that the proposed feedrate scheduling method is reliable and effective.     

2-D SHAPE BLENDING OF NURBS CURVE SHAPES

２－ＤＳＨＡＰＥＢＬＥＮＤＩＮＧＯＦＮＵＲＢＳＣＵＲＶＥＳＨＡＰＥＳＪｉｎＸｉａｏｇａｎｇ；ＢａｏＨｕｊｕｎ；ＰｅｎｇＱｕｎｓｈｅｎｇ２－ＤＳＨＡＰＥＢＬＥＮＤＩＮＧＯＦＮＵＲＢＳＣＵＲＶＥＳＨＡＰＥＳ￥ＪｉｎＸｉａｏｇａｎｇ；ＢａｏＨｕｊｕｎ；Ｐｅ...     

基于NURBS的PDE曲面构造法研究及应用

由非均匀有理Ｂ样条曲线曲面给定边界条件，用偏微分方程来构造曲面，以参数“ａ”控制其整体形状，本文分析其思路原理及过程，并列举了在ＣＡＤ上的应用，最后分析了优缺点。     

一种对称非均匀细分曲面算法

为了得到能更好应用于CAD系统的细分曲面造型方法,提出一种基于B-样条的对称非均匀细分算法,其中的思想和均匀Lane-Riesenfeld节点插入算法相似。基于B-样条的节点插入算法,以Blossoming为工具,计算出细分后的新控制顶点。细分后得到的极限曲面由张量积样条曲面组成,在奇异点达到2C连续。与传统的细分曲面算法相比,该细分曲面算法具有良好的局部支撑性,大大降低了算法的复杂度,而且该算法是对称的,不用考虑定向问题。     

自由曲面的测量、建模、加工一体化过程研究

本文以一个鼠标模型为例，介绍了自由曲面的测量、建模、加工一体化过程，对一体化过程的各个步骤进行了研究为实现逆向工程集成化奠定了基础。     

基于DXF文件的曲线拟合方法的设计与实现

现有的基于微机开发的数控加工系统都是人工调试完成后加载运行,为了能够依据AUTOCAD绘图系统提供的信息自动生成数控加工代码,本文对基于PMAC卡的数控加工代码生成及动态在线监测系统研制过程中遇到的问题进行了研究,重点研究了如何利用DXF文件中的参数进行曲线拟合,详细介绍了NURBS曲线算法的实现,为后续的工作打下了基础。     

Spline-based meshfree method with extended basis

In this work, an extension has been performed on the analysis basis of spline-based meshfree method (SBMFM) to stabilize its solution. The potential weakness of the SBMFM is its numerical instability from using regular grid background mesh. That is, if an extremely small trimmed element is produced by the trimming curves that represent boundaries of the analysis domain, it can induce an excessively large condition number in global system matrix. To resolve the instability problem, the extension technique of the weighted extended B-spline (WEB-spline) is implemented in the SBMFM. The basis functions with very small trimmed supports are extrapolated by neighboring basis functions with some special scheme so that those basis functions can be condensed in the solution process. In order to impose essential boundary conditions in the SBMFM with extended basis, Nitsche's method is implemented. Using numerical examples, the presented SBMFM with extended basis is shown to be valid and effective. Moreover, the condition number of the system is well-managed guaranteeing the stability of the numerical analysis.     

基于MATLAB的叶片型面几何造型及超差计算

介绍了激光非接触式四坐标测量仪图形输出系统的研制与开发。简述了叶片测量原理;采用MATLAB软件,对测得的叶片数据进行处理,并运用spline工具箱,绘制了被测叶片截面的B样条曲线,建立了叶片的三维几何模型;最后实现了模型的超差计算。     

NURBS曲线C~1连续参数优化算法

曲线的参数特性直接决定基于自由曲线的路径规划、运动控制等算法的质量.为了生成满足C1连续的近似弧长参数化,提出一种基于分段三次重新参数化的参数优化算法.首先利用Simpson方法离散积分能量,然后使用极值求解法求得初始解,最后通过LM(Levenberg-Marquardt)优化算法计算出曲线的最优参数表示.与C1连续的分段有理重新参数化方法相比,该算法能够在分段数量很少的情况下达到局部最优.最后通过实例说明了文中算法的有效性.     

基于双圆弧逼近的插补技术研究

NURBS插补技术已经成为国内外数控系统厂商和相关研发机构争相研究的热点问题,从NURBS曲线构造原理出发,给出了一般参数曲线插补基本实现过程。分析了NURBS曲线数学理论基础、双圆弧基本数值算法。采用常见的CAM软件ProE辅助设计软件,验证实验证明了该技术方案的可行性。