一种实用的B样条曲线分割求交方法

曲线求交在CAD／CAM实体造型过程中经常遇到，处理不当会导致造型失败。基于B样条曲线的性质，建议了一种B样条曲线分割求交的方法。该方法已应用于三维实体CAD软件Solid2000，并给出了几个求交的实例，表明该方法是稳定、准确和有效的。     

高速运转凸轮反求的等距曲线方法

根据三次均匀有理B样条曲线、等距曲线的基本理论,推导了等距三次均匀有理B样条插值算法和应用于凸轮反求的优化算法,较好地解决了坐标机测量一般光滑柱状面的技术问题.用此方法反求出的高速运转的凸轮,无论是进行机构运动仿真还是实际运用均能达到要求.     

曲面造型中一种快速的曲面跟踪求交算法

提出了一种新的曲面求交算法,采用精度好、效率高、计算稳定的迭代方法求得等参数网格线在曲面上的交点,并通过跟踪获得两曲面的交线。本算法由三个子算法组成,一个是求曲面上到固定点距离最近的点,一个是求参数网格线与曲面的交点,一个是求曲面与曲面的交点。为保证不遗漏交点,利用第一个算法对参数网格点进行分类,跟踪交点时利用第三个求下一个交点。与离散法求交相比,本算法具有计算稳定性、可靠性好,速度快,精度高的优点     

测量数据的B样条曲线逼近算法

根据遗传算法,提出了一种B样条曲线逼近大量测量点的方法.为了使曲线具有良好的光顺性和曲线在端点处较好的控制性,采用端点插值的三次非均匀B样条算法逼近测量数据点.     

一种自由曲线的误差评定方法

文中对IGES文件格式及B样条曲线的数据记录格式作了简要的说明,提出了一种自由曲线的误差评定方法.给出了点到理论曲线距离的算法,优化了距离的计算方法,大大提高了计算效率.     

一种数控自动编程直线插补的新算法

本文给出了一种根据零件加工精度的要求 ,对三次B样条列表曲线进行直线插补、自动生成变步长刀位轨迹的算法 ,简称自适应算法。该算法可根据曲线曲率大小 ,自动改变步长 ,同时逼近误差满足要求。该算法稳定、可靠 ,便于在列表曲线、列表曲面的数控加工中推广应用     

一种优化的NURBS曲线插补算法

为弥补目前非均匀有理B样条插补算法的不足,提出一种优化的非均匀有理B样条曲线插补算法。算法采用插补前S曲线加减速方法,不仅优化了前瞻过程,而且在回溯过程中考虑了短样条的情况。算法对长样条和短样条非均匀有理B样条曲线能用统一的方法进行插补,通过引入环形缓冲区和预插补(非离线),提高了加工效率,同时合理地安排插补任务增强了系统的实时性。通过MATLAB仿真,验证了算法的有效性。     

测量数据的B样条曲线逼近算法

根据遗传算法 ,提出了一种B样条曲线逼近大量测量点的方法。为了使曲线具有良好的光顺性和曲线在端点处较好的控制性 ,采用端点插值的三次非均匀B样条算法逼近测量数据点。     

空间曲线实时插补算法的研究

随着数控加工系统的发展．传统的自由曲线曲面离散直线、圆弧插补所带来的大量程序、大量数据丢失以及对机床的冲击影响已成为数控加工中急待解决的问题。NURBS曲线作为STEP标准中定义自由曲线的唯一表示方法，它不仅能精确统一的表示标准解析曲线和自由曲线．而且它的控制能力十分强大、灵活．非常适合于物体外形的表达和交互式设计．因此．研究NURBS曲线插补技术对提高数控系统的加工性能和加工效率具有重大的意义。     

一种新的空间曲线匹配算法

提出一种新的空间曲线匹配算法。该算法对离散的曲线进行光顺、拟合和采样，使用空间曲线微分几何性质计算各采样点的曲率和弗朗内特标架。通过曲率计算匹配点对列表，通过对齐匹配点对的弗朗内特标架进行曲线匹配，得到一个匹配矩阵集。从匹配矩阵集中选出一个最优匹配的匹配矩阵，使得空间曲线的对应点匹配窗口内的距离平方和最小。实验结果证明，算法效率高、鲁棒性好。     

自由曲面数控加工刀具轨迹曲线的一种生成算法

提出一种自由曲面数控加工轨迹曲线计算方法。根据这一方法,可由自由曲面上一定数量的任意分布型值点来 计算曲面加工时的刀具曲线。算法的基本思想是,型值点影响并决定着其控制区域内的曲面形状,这种影响的大小与到 型值点的距离及权指数相关。分别给出了沿X向进给及Y向进给时刀具轨迹曲线的生成算法。讨论了算法中参数选取 对加工曲面形状及拟合精度的影响。     

基于Hilbert填充曲线的自由曲面刀具路径规划研究

利用平面Hilbert填充曲线生成方法简单、易于控制填充疏密的优点,将其用于了自由曲面数控加工刀具路径的生成.对平面Hilbert填充曲线的生成原理进行了研究,用矩阵运算的方法生成该曲线.结合自由曲面的形成过程,提出将平面Hilbert曲线通过与曲面参数域相对应的方法映射到曲面上,进而生成加工刀具路径的思想.最后用一个具体应用实例验证了生成平面Hilbert曲线方法的正确性,和用此曲线作为数控加工刀具路径的可行性.通过与经典刀具路径生成方法比较可见该方法具有算法简单,加工余量均匀,加工效率与表面质量高的优点.     

An algorithm of NURBS surface fitting for reverse engineering

Reverse engineering is an approach for constructing a CAD model from a physical part through dimensional measurement and a surface model. Different from conventional methods, this paper develops a new algorithm by which a desired fitted surface is obtained with less computation. Let selected m×n measured points be control points to construct B-spline or NURBS surface, then modify this constructed surface by using all the measured points and least squares minimization. A new algorithm for parameterization for measured points is also presented in this paper. The effectiveness and efficiency of these proposed algorithms are demonstrated.     

计算任意多边形最大内圆的一种算法

这里给出一种利用计算参考点确定圆心的搜索方向，采用步长因子自动控制搜索精度的计算任意多边形最大内圆的算法。并在AutoCAD中利用AutoLisp程序模拟了算法的动态搜索过程，验证了该算法的正确性和可操作性。     

An enhanced algorithm for estimation of a digitized curve length using B-splines

A digitized curve length estimation is a hot topic of research. All the methods tend to estimate the length of the original curve from which the digitized curve is obtained. When comparing different methods of estimation, the main performance criterium is the accuracy of this estimation. In this paper a novel approach is presented. It shows a significant improvement compared to all the other methods, regardless of the resolution and the type of curve. The method is based on B-splines. The initial number of control points and their location is determined by the reverse polygonization, which is one of the polygonal approximation techniques. The method then iteratively updates the location of the control points of the B-spline based on the specified cost function. Due to the fact that it shows the same level of accuracy for different B-spline orders it is also much more convenient to use than the other methods because it doesn’t require the selection of appropriate parameter(s). Beside that it doesn’t require nonlinear optimization techniques. The performance of the method is verified on various test curves including the ones with multiple paths within pixel at different grid resolutions.     

UG中桥接曲线参数的自动寻优方法研究

如何快速、精确、光滑地连接多个曲面块,是广泛存在于CAD建模工作中的一个难题。在UG平台上进行多曲面连接系统的二次开发过程中,需要由最小曲率半径值反求出桥接曲线(Bridge Curve)的两个参数。本文找出了桥接曲线的等效数学模型,并在此基础上确定出桥接曲线最小曲率半径与桥接参数之间的关系,给出了求解理论方程组。由于求解精确理论值非常困难,本文采用最优化方法对方程组进行了数值求解,并依据经验给出了桥接质量的评价标准。通过验证表明,该方法精度可满足工程实际需要。     

An efficient algorithm for processing data from a multi-point sensor of vibrations

A new technique of vibration sensing, based on a polarimetric fibre-optic strain sensor, is presented; it is designed for localisation of multiple sources of disturbances in a broad frequency spectrum without using fibre gratings. A mathematical model of the sensor is used for development of a variational method for estimation of amplitudes of component vibrations on the basis of noisy samples of the signal at the output of the sensor. This method is implemented in a new algorithm of estimation, being 100–1000 more efficient (in terms of computing time) than an algorithm published previously.     

An algorithm for finding the zero crossing of time signals with Lipschitzean derivatives

This paper deals with an efficient global optimization algorithm enabling to find the first root from the left of an equation ø(t) = 0, where t ϵ [a,b], ø(a) > 0, assuming the time function ø(t) has Lipschitzean derivatives. Two theorems establish the necessary conditions for finding the first root from the left and convergence of the algorithm. The algorithm can be adopted for finding the switching times of networks with internally controlled switches, such as analog-to-digital and digital-to-analog converters, or power converters. Examples showing the general applicability and accuracy of the new algorithm are given and the results of a comparison with other methods are presented.     

An algorithm for the determination of optimal design parameters of x̄control charts

One of the main difficulties in the use of an economic design of reliable optimum values for the design parameters compared with a control chart is the computation of the design parameters n (sample size), h (sampling interval) and k (control limit factor). A very simple procedure is described in this research to determine the design parameters of an x̄ control chart in Duncan’s economic model, such that they minimise the expected total costs per time unit. Numerical examples give more accurate and more published results.     

An analysis of cutting-edge curves and machining performance in the Inconel 718 machining process

When considering the machining of materials used for aircraft components, the principal areas of interest usually include the manufacturing characteristics of the materials when they are machined with different cutting-edge curves, and the development of manufacturing processes that improve the machining precision, thereby reducing the time required to carry out secondary machining operations or error correction of the final component. A further area of concern is to develop manufacturing techniques that are capable of generating highly reliable aircraft components which ensure that flight safety is not compromised through component failure. This paper employs a Taguchi L9 experimental layout to investigate the optimal cutting parameters when machining Inconel 718 with the planar-type conical ball-end cutter, the S-type cutter, and the traditional conical ball-end milling cutter. The current results provide a valuable technical database for aircraft component manufacturers who are seeking to enhance their automatic manufacturing capabilities.