共查询到18条相似文献,搜索用时 109 毫秒
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利用参数化曲线段端点处的几何信息,根据端点处参数速率相等构造并确定最优或逼近最优的有理参数化方程。方法计算简单、效率高,由曲线端点处的几何信息可直接得到最优有理参数化方程。大量实验数据表明方法准确度更高、自适应性更强。若参数化曲线段端点处的参数速率相等且是最值,则得到的参数化是最优的;其余情形逼近于最优。 相似文献
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Bézier曲线的一种重新参数化新方法 总被引:2,自引:0,他引:2
曲线重新参数化的关键是重新参数化方法。对Bézier曲线的重新参数化方法进行了讨论,找到了一种新方法,比常用的有理线性参数变换计算简单,通用性强。论证了利用新方法的自由度,可以求出Bézier曲线的最优参数化方程。给出了求解Bézier曲线最优参数化方程的新算法。新算法具有单一自由度,最优值通过求解一个二次方程的根得到,算法简单可靠,文中给出了计算实例。 相似文献
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C-Bézier曲线的一种重新参数化新方法 总被引:2,自引:0,他引:2
曲线重新参数化的关键是重新参数化方法.对Bézier曲线的重新参数化方法进行了讨论,找到了一种新方法,比常用的有理线性参数变换计算简单,通用性强.论证了利用新方法的自由度,可以求出Bézier曲线的最优参数化方程.给出了求解Bézier曲线最优参数化方程的新算法.新算法具有单一自由度,最优值通过求解一个二次方程的根得到,算法简单可靠,文中给出了计算实例. 相似文献
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该文改进衡量参数优劣的标准,利用分段线性变换,得到了一种新的最优参数化方法。以分段节点作为自由变量,以曲线参数速率的变化率为目标函数进行优化。通过求解一个方程组,得到了所求节点的显式解。与以往利用M?bius变换的最优参数化不同,该文得到的曲线仍为Bézier曲线。最优参数化后的参数接近弧长参数,文末的数值实例验证了本算法的有效性。 相似文献
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本文讨论参数曲线的近似弧长参数化插值方法。基于保单调插值方法,用分段五次(或五次以上)Bernstein多项式构造了弧长函数的反函数局部逼近解t=T(s),且T(s)是C~2连续的。将t=T(s)代入原参数曲线,得到C~2连续的近似弧长参数化曲线。这种近似弧长参数化曲线不但插值原参数曲线上的一组点,且在这组点有着精确的弧长参数化。进一步研究表明近似弧长参数化曲线可由原参数曲线经参数变换得到,所以它们有着完全相同的几何形状。最后,导出了近似弧长参数化曲线切失模长与1有二阶误差。 相似文献
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基于Haar小波分解的快速曲线重构 总被引:1,自引:0,他引:1
采用Haar小波分解构造误差驱动的曲线数据压缩算法,对求得的少量重要数据点。运用保型性好计算速度快的通用参数化曲线插值方法,最终求得满足要求的三次B样条曲线,本文算法适用于大量密集数据点的快速曲线重构。 相似文献
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针对SolidEdge在产品设计中遇到的一些复杂曲线的情况,通过两个实际案例,由浅入深地讨论了如何利用该软件进行曲线的参数化设计。 相似文献
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Ramsharan Rangarajan Adrian J. Lew 《International journal for numerical methods in engineering》2011,88(6):556-585
We construct a method for the parameterization of a class of planar piecewise C2‐curves over a collection of edges in an ambient triangulation. The map from the collection of edges to the curve is the closest‐point projection. A distinguishing feature of the method is that edges in the ambient triangulation need not interpolate the curve. We formulate conditions on the ambient triangulations so that the resulting parameterization over its selected edges is (i) bijective, (ii) maps simple, connected collection of edges to simple, connected components of the curve, and (iii) is C1 within each edge of the collection. These properties of the parameterization make it particularly useful in the construction of high‐order finite element approximation spaces on planar curves immersed in triangulations. We discuss this application and illustrate it with numerical examples. The parameterization method applies to a large class of planar curves, including most ones of interest in engineering and computer graphics applications, and to a large family of triangulations, including acute‐angled triangulations. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
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In this study, a hyper-redundant manipulator was designed for detection and searching in narrow spaces for aerospace and earthquake rescue applications. A forward kinematics equation for the hyper-redundant manipulator was derived using the homogeneous coordinate transformation method. Based on the modal function backbone curve method and the known path, an improved modal method for the backbone curves was proposed. First, the configuration of the backbone curve for the hyper-redundant manipulator was divided into two parts: a mode function curve segment of the mode function and a known path segment. By changing the discrete points along the known path, the backbone curve for the manipulator when it reached a specified path point was dynamically obtained, and then the joint positions of the manipulator were fitted to the main curve by dichotomy. Combined with engineering examples, simulation experiments were performed using the new algorithm to extract mathematical models for external narrow space environments. The experimental results showed that when using the new algorithm, the hyper-redundant manipulator could complete the tasks of passing through curved pipes and moving into narrow workspaces. The effectiveness of the algorithm was also proven by these experiments. 相似文献
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Dan Wang Weihong Zhang 《International journal for numerical methods in engineering》2012,90(13):1598-1617
Simultaneous shape optimization of thin‐walled curved shell structures and involved hole boundaries is studied in this paper. A novel bispace parameterization method is proposed for the first time to define global and local shape design variables both in the Cartesian coordinate system and the intrinsic coordinate system. This method has the advantage of achieving a simultaneous optimization of the global shape of the shell surface and the local shape of the openings attached automatically on the former. Inherent problems, for example, the effective parameterization of shape design variables, mapping operation between two spaces, and sensitivity analysis with respect to both kinds of design variables are highlighted. A design procedure is given to show how both kinds of design variables are managed together and how the whole design flowchart is carried out with relevant formulations. Numerical examples are presented and the effects of both kinds of design variables upon the optimal solutions are discussed. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
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This article considers a dynamic optimization problem arising in a one-dimensional magnetohydrodynamic flow, which can be modelled by coupled partial differential equations, where the external control input (external induction of magnetic field) takes a multiplicative effect on the system states (momentum and magnetic components). The aim is to drive the flow velocity to within close proximity of a desired target of flow velocity at the pre-indicated terminal time. First, the Galerkin method is utilized to reduce the original dynamic optimization problem to a lower finite-dimensional dynamic optimization problem governed by a set of ordinary differential equations. Then the control parameterization method is employed to parameterize the finite-dimensional optimization problem and thus obtain an approximate optimal parameter selection problem, which can be solved using gradient-based optimization techniques, such as sequential quadratic programming. The exact gradients of the cost functional with respect to the decision parameters, which are the key advantages of this approach, are computed using the analytical equations. Finally, numerical examples are illustrated to verify the effectiveness of the proposed method. The novel scheme of this article is to develop an effective computational optimal control method for realizing the optimal tracking control of flow velocity in a one-dimensional magnetohydrodynamic flow. 相似文献
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产品零部件之间存在着复杂的信息依赖关系,对产品局部的改动可能影响到整个产品的设计周期,因此评价产品设计变更的消解时间以便决定合适的产品开发策略显得极为重要。在产品参数化设计进程模型的基础上,提出了产品设计任务信息依赖度的概念和计算方法,分析了交互依赖、串联、循环等五种任务关联模型的设计变更时间计算方法,以减速器为设计实例说明了参数设计变更的时间评价方法。 相似文献