【作者】 束长林；

【导师】 孙玉文；

【作者基本信息】 大连理工大学 ， 机械制造及其自动化， 2004， 硕士

【摘要】 反求工程(RE，Reverse Engineering)和数控加工技术(NC，Numerical Control)是先进制造技术中的关键技术，在产品跟踪以及创新设计中起着重要作用。RE／NC的集成，将有助于缩短产品测量、建模与加工(3MS)的周期，改善设计的质量与加工的效率。为此，本文以非均匀有理B样条技术(NURBS)为基础，针对离散数据的曲面重建及其加工路径规划等问题进行了系统研究，以期实现RE、NC的有机集成，从而提高产品快速开发(RPD)的能力。 根据离散数据(截面数据、散乱数据)的两种形式，分别讨论了各自的建模方式。首先，对于截面数据给出了基于统一节点矢量的NURBS曲面蒙皮与拟合方法，避免了利用节点插入算法存在的节点相容性问题。其次，针对建模难度较大的无明显矩形拓扑的空间散乱数据，提出了一类卷曲模型的精确曲面建模方法，基于提出的截面轮廓设计技术并借助蒙皮方法实现了该类数据的基面参数化，在此基础上采用迭代求精建模策略进行曲面的NURBS重建，提高了建模的质量。此外，对工程实际中常常忽视的曲面延拓问题，给出了概括性阐述及选择方法。 以微分几何学和矢量分析为工具，提出了复杂曲面加工路径规划的新方法。通过给定被加工曲面采样点处走刀方向在其参数域上的表示，并依据标量场与梯度场的转化关系，建立了参数域上基于NURBS的走刀矢量场拟合模型，由此产生的路径是并行的、光滑的，且有利于轨迹的补偿和调控，可将多种轨迹规划的方式统一在同一模型下，能有效解决截平面法在参数曲面轨迹规划中存在的截交操作。同时，基于复杂曲面加工的局部各向异性特征，给出了一种具体的基于最优切削方向场的刀具路径规划方法。 综上可知，基于参数域同构且以NURBS为连接手段的曲面建模与路径规划技术，提供了一种RE／NC的有效集成途径，相关实例验证了方法的正确性与可行性。更多还原

【Abstract】 RE (Reverse Engineering) and NC (Numerical Control) are the key technologies of AMT (Advanced Manufacturing Technology), and they play an important role in product reproducing and innovatively designing. The integration of RE/NC can shorten the period of product with measuring, modeling, machining (3 MS), and improve the quality of designing and efficiency of manufacturing. Therefore, this paper systemically studies the surface reconstruction from measured points and the tool-path planning of surface based on Non-uniform Rational B-Splines (NURBS), so as to realize the integration of RE/NC, and to boost the ability of RPD.According to the two styles (cross-sections, scatter points) of measured points, the methods of modeling are discussed respectively. Firstly, for the cross-sections, given the uniform knot vectors a fitted NURBS surface can be produced by skinning, and the algorithm avoids the problem of knot compatibility by knot insertion. Secondly, for the scattered points with no obvious rectangular topology, it is difficult for them to be parameterized, and a NURBS surface fitting method with tight tolerance for wrap-around models is presented. By means of sectional design technique and skinning method, these points can be parameterized by constructed base surface. Plus with ICP, the precise NURBS model is constructed, which boost the quality of mode!. In addition, the problem of surface extension is often neglected in the engineering, this paper presents the expatiation on the problem, and how to choose these methods is also to be given.Using differential geometry and vector analysis, a new tool-path generation method for freeform surface machining is presented. Given the tool-path direction of the parameter domain of machined surface, a tool-path director vector field model based on NURBS can be constructed by fitting discrete sample vector value according to the relation of scalar quality field and gradient field. And the generated tool-paths not only are side-by-side and smooth, but also are in favor of repairing and controlling. Furthermore, some other tool-path planning methods can be represented with the above method, especially which can cope with the problem of intersectant operation form iso-planar method. Based on the feature of anisotropy of machining width on the local of the free-form surface, a tool-path planning method of optimal cutting direction field is given.Above all, the technologies , surface modeling and tool-path planning by means of NURBS based on the same parameter domain, offer a way for integration of RE/NC. Related samples show the feasibility and precision of the methods.更多还原