一种G^2连续Hermite样条的构造方法

通过保证曲线段连接点处的左右曲率矢相等 ,构造 G2连续的 Hermite样条 ,既保持 Hermite样条的原有特点 ,又保证了良好的光顺性 ,以满足研究工作的要求。

基于双圆弧插值的G^2 Hermite数据容许分割

螺线是一种具有单调曲率的平面曲线,只能插值容许G^2Hermite数据(即可用螺线插值的G^2Hermite数据).在G^2 Hermite数据{A,T_A,O_A,B,T_B,O_B}的G1双圆弧插值基础之上,插入一个点(或2个点)以及该点处的切向与曲率值,把给定数据分割成2组(或3组)容许G^2Hermite数据,再用G^2连续的分段螺线插值之.根据双圆弧连接弧的不同情形,提供了3种不同的算法.算法几何意义明显,实用性强,能用不超过3条G^2连续的分段螺线插值任意一组非容许G^2 Hermite数据,彻底解决了用最少螺线段插值任意G^2 Hermite数据的问题,对高速公路、高速铁路、机器人行走路线等对几何品质要求较高的曲线设计有潜在的应用价值,最后给出实例表示.

S-型非均匀有理TC-双弧的G^2Hermite插值

S-型PH(Pythagorean-hodograph,简称PH)曲线可以用于整体构造含有拐点等情况的曲线造型。文章运用分段的思想,通过将有理三次PH曲线与TC-双弧相结合,引入曲率参数κ,构造出插值G2 Hermite数据的S-型PH曲线;与已有的结果相比,构造的曲线更加丰富,且具有更好的光滑性;最后,通过调整端点处的曲率参数κ,使得曲线具有更好的曲率变化。

自动满足C^2连续的带参数五次Hermite插值样条

为了克服已有的带形状参数的三次或四次Hermite型插值样条不能自动满足C2连续这一不足,提出了一类新的五次Hermite插值样条.该样条除了具有带形状参数Hermite型插值样条的特性外,在插值条件保持不变的情形下可自动满足C2连续且其形状还可通过所带的形状参数进行调控.进一步,给出了一种确定形状参数最优取值的方法,该法可使得五次Hermite插值样条曲线具有最优插值效果.

基于Mbius变换的五次有理PH曲线C^2 Hermite插值

文章通过Mbius变换引进了参数,在拓展的复平面C∞=C∪{∞}上,构造了五次有理PH曲线C2 Hermite插值,给出了插值算法;基于"弹性弯曲能量"得到满足插值条件的最优曲线,数值实例表明了该算法的有效性。

An Optimal Feed Interpolator Based on G^2 Continuous Bézier Curves for High-Speed Machining of Linear Tool Path

A numerical control (NC) tool path of digital CAD model is widely generated as a set of short line segments in machining. However, there are three shortcomings in the linear tool path, such as discontinuities of tangency and curvature, huge number of line segments, and short lengths of line segments. These disadvantages hinder the development of high speed machining. To smooth the linear tool path and improve machining efficiency of short line segments, this paper presents an optimal feed interpolator based on G^2 continuous Bézier curves for the linear tool path. First, the areas suitable for fitting are screened out based on the geometric characteristics of continuous short segments (CSSs). CSSs in every area are compressed and fitted into a G^2 Continuous Bézier curve by using the least square method. Then a series of cubic Bézier curves are generated. However, the junction between adjacent Bézier curves is only G^0 continuous. By adjusting the control points and inserting Bézier transition curves between adjacent Bézier curves, the G^2 continuous tool path is constructed. The fitting error is estimated by the second-order Taylor formula. Without iteration, the fitting algorithm can be implemented in real-time environment. Second, the optimal feed interpolator considering the comprehensive constraints (such as the chord error constraint, the maximum normal acceleration, servo capacity of each axis, etc.) is proposed. Simulation and experiment are conducted. The results shows that the proposed method can generate smooth path, decrease the amount of segments and reduce machining time for machining of linear tool path. The proposed research provides an effective method for high-speed machining of complex 2-D/3-D profiles described by short line segments.

C2 Continuous Quartic Hermite Spline Curves with Shape Parameters

In order to relieve the deficiency of the usual cubic Hermite spline curves,the quartic Hermite spline curves with shape parameters is further studied in this work. The interpolation error and estimator of the quartic Hermite spline curves are given. And the characteristics of the quartic Hermite spline curves are discussed.The quartic Hermite spline curves not only have the same interpolation and continuity properties of the usual cubic Hermite spline curves, but also can achieve local or global shape adjustment and C;continuity by the shape parameters when the interpolation conditions are fixed.

CONSTRUCTION OF G^2 CONTINUOUS CURVES ON SURFACE WITH PLANAR CUBIC BZIER CURVES

The problem of constructing curve on parametric surface (or surface that canbe parameterized) such that it interpolates a sequence of points with prescribed tangent directionand curvature vector (or geodesic curvature) at every point and the issue of curve blending on thiskind of surface are researched. The mapping and tangent mapping from the surface to its parametricplane are introduced and thus several conclusions with differential geometry are deduced. Based onthose conclusions, the problem of interpolating (or blending) curve on a parametric surface isconverted to a similar one on its parametric plane. The final solution curve of either interpolationor blending issue is explicit and can still be expressed by parametric form. And so, unlikeexisting methods, the presented method needs not to use any surface/ surface intersectionalgorithms, usually a troublesome process, for displaying such interpolation curve. Experimentresults show the presented methods are feasible and applicable to CAD/CAM and computer graphics

形状可调的C^2连续三次三角Hermite插值样条

基于函数空间{1,sint,cost,sin^2t,sin^3t,cos^3t}构造了一种形状可调的三次三角Hermite插值样条.该样条不仅具有带参数的Hermite型插值样条的主要特性,而且在插值节点为等距时可自动满足C2连续,其形状还可通过所带的参数进行调节.在适当条件下,该样条对应的Ferguson曲线可精确表示工程中一些常见的曲线.

Mbius变换下四次有理抛物-PH曲线的C^2 Hermite插值

目的曲线插值问题在机器人设计、机械工业、航天工业等诸多现代工业领域都有广泛的应用,而已知端点数据的Hermite插值是计算机辅助几何设计中一种常用的曲线构造方法,本文讨论了一种偶数次有理等距曲线,即四次抛物-PH曲线的C2Hermite插值问题。方法基于Mbius变换引入参数,利用复分析的方法构造了四次有理抛物-PH曲线的C^2 Hermite插值,给出了具体插值算法及相应的Bézier曲线表示和控制顶点的表达式。结果通过给出"合理"的端点插值数据,以数值实例表明了该算法的有效性,所得12条插值曲线中,结合最小绝对旋转数和弹性弯曲能量最小化两种准则给出了判定满足插值条件最优曲线的选择方法,并以具体实例说明了与其他插值方法的对比分析结果。结论本文构造了Mbius变换下的四次有理抛物-PH曲线的C^2 Hermite插值,在保证曲线次数较低的情况下,达到了连续性更高的插值条件,计算更为简单,插值效果明显,较之传统奇数次PH曲线具有更加自然的几何形状,对偶数次PH曲线的相关研究具有一定意义。

Constructing G^2 Continuous Curve on Freeform Surface with Normal Projection

This article presents a new method for G2 continuous interpolation of an arbitrary sequence of points on an implicit or parametric surfaee with prescribed tangent direction and curvature vector, respectively, at every point. First, a G2 continuous curve is constructed in three-dimensional space. Then the curve is projected normally onto the given surface. The desired interpolation curve is just the projection curve, which can be obtained by numerieally solving the initialvalue problems for a system of first-order ordinary differential equations in the parametric domain for parametric case or in three-dimensional space for implicit ease. Several shape parameters are introduced into the resulting curve, which can be used in subsequent interactive modification so that the shape of the resulting curve meets our demand. The presented method is independent of the geometry and parameterization of the base surface. Numerical experiments demonstrate that it is effective and potentially useful in numerical control （NC） machining, path planning for robotic fibre placement, patterns design on surface and other industrial and research fields.