基于干涉预处理的NURBS曲线前瞻插补算法

鉴于直接自适应插补容易在加工过程中引起较大的速度波动,而按曲率极值点对NURBS曲线进行分段插补造成加减速过程中加速度和加加速度超限,提出一种基于干涉预处理的非均匀有理B样条曲线前瞻控制插补算法。首先对曲线进行自适应处理,得到各自适应插补点的运动参数;然后找出其中加速度或加加速度超限的点(即危险点),并对这些点的速度进行前瞻控制,根据前瞻控制信息对相邻危险点进行干涉处理,最终得到用来对曲线分段的危险点信息和相应的控制策略;最后根据各危险点之间的干涉类型对曲线进行实时插补。仿真实验表明,该算法能够在保证加工精度的前提下,实现进给速度的平滑过渡,并且能够保证加速度和加加速度不超限。     

A quick deviation zone fitting in coordinate metrology of NURBS surfaces using principle component analysis

Evaluation of the tolerance zone using discrete measured points plays a critical role in today’s manufacturing, metrology, and many industrial applications. The deviation zone is typically evaluated using a fitting method that locates an ideal desired geometry corresponding to a set of measured points while a function of the Euclidean distances of the measured points to the ideal surface becomes minimum. This paper presents a quick and reliable algorithm called Dynamic Principle Component Alignment (DPCA) for fitting complex surfaces to the coordinate metrology measured points using the information that is dynamically generated by Principal Component Analysis (PCA) of the measurement data and the corresponding fitted geometry. The developed algorithm efficiently eliminates the necessity for applying commonly used optimization methods for the fitting (localization) process, which decreases the computational cost and uncertainty of the evaluation process. Moreover, DPCA is very reliable and practical in coordinate metrology with large data sets in processes such as laser scanning and other optical methods. The results show that the proposed methodology more accurately finds fitting parameters in comparison with the other commonly used methods while the computational cost is considerably reduced.     

Facial image synthesis using skin texture recording

A significant issue in synthesizing realistic faces is the representation of skin grain and wrinkles. This paper describes a new approach based on the registered body of a real person. This recording allows simultaneously registering of the 3-D coordinates of a point and the corresponding reflected intensity. Using a 4-D B-spline surface to reconstruct the face, we come close to achieving a photographic result.     

汽轮机叶片截型数据样条重构

就CAD二次开发工程中遇到的叶片截型数据点重构样条的问题进行了分析,提出了一个基于德布尔(de Boor)样条值点计算递推法的反求样条控制顶点的方法,推导了具体计算的公式,给出了计算方程组。在实践中应用该方法得到了过型值点的光顺的样条曲线,获得了满意的效果。最后就多种CAD软件实现的反求控制顶点进行了比较。     

基于NURBS的水力机械叶片表面造型研究

论述了在已知叶片轴面截线图的情况下，采用B样条插值理论，求出叶片表面控制点，然后利用非均匀有理B样条方法实现叶片表面的数值化。同时可采用交互方式对叶片表面控制点或其权因子进行修改，构造出逼真的叶片，增强了叶片计算机辅助设计系统的交互设计能力；对改进叶片的设计方法和提高其设计质量具有重要意义。     

基于数学规划的曲面造型方法

利用数学规划方法构造曲面是一种新颍的几何造型方法，在自由曲面设计、过渡面设计等领域具有鲜明的特点。本文比较详细地阐述了该方法的基本思想和实现方法，并就其理论根据和发展前景做了深入的讨论。     

热轧带钢板形质量可视化研究

本文首先对板形质量可视化的方法作了比较，然后介绍了现场板形数据的获取。在对板形数据作了充分分析的基础上，提出一种基于空间点插值和逼近相结合的板形再现方法。接着介绍了板形模型的建立以及板形质量可视化软件的实现，最后用该软件处理的图象与实际检测结果相比较，正确率较高。     

三次B样条插值在测量叶片散射光分布的应用

本文阐述了一种测量叶片散射光分布的快速方法,本方法是结合三次B样条插值算法与直接测量法而成,与常规测量叶片散射光分布方法相比,其测量时间短,而且获得到较精确的测量结果。在VC 6.0的环境下,通过串口连接,实现了软件与叶片散射光分布测量系统的通讯,也实现了直接测量法和三次B样条插值算法的结合。本文通过叶片散射光分布测量系统,在650nm波长光照条件下,测定了标准白板(参比样)的反射光和玉米叶片的反射和透射在入射面上的光强分布,并使用三次B样条插值所得数据与采集到的数据进行比较,获得较好的实验结果。     

Numerical Solutions for Unsteady Flows of a Magnetohydrodynamic Jeffrey Fluid Between Parallel Plates Through a Porous Medium

In the present article, the numerical solutions for three fundamental unsteady flows (namely Couette, Poiseuille, and generalized Couette flows) of an incompressible magnetohydrodynamic Jeffrey fluid between two parallel plates through a porous medium are presented using differential quadrature method. The equations governing the flow of Jeffrey fluid are modeled in Cartesian coordinate system. The resulting non-dimensional differential equations are approximated by using a new scheme that is trigonometric B-spline differential quadrature method. The scheme is based on the differential quadrature method in which the weighting coefficients are obtained by using trigonometric B-splines as a set of basis functions. This scheme reduces the equation into the system of first-order ordinary differential equation which is solved by adopting strong stability-preserving time-stepping Runge–Kutta scheme. The effects of the sundry parameters of interest on the velocity profiles are studied and the results are presented through graphs. It is observed that, the velocity increases from the horizontal channel to vertical channel. The velocity is a decreasing function of magnetic parameter. With an increase in time, the velocity increases.     

悬挂式层间减震结构地震反应的比较分析

在符拉索夫开口簿壁杆件理论平面假定的基础上,本文针对核筒,采用三次B样条有限条方法构造连续化模型,并分别计算其动、势能。针对悬挂部分,分别应用杆系有限元和悬吊体系理论,计算其动、势能。然后,由拉格朗日公式,得到悬挂结构体系的动力方程,并用wilson-θ法求解。最后,结合算例得到了具有实际意义的结论。