共查询到20条相似文献,搜索用时 15 毫秒
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This paper presents a general scheme to compute ridges on a smooth 2-manifold surface from the standpoint of a vector field. A ridge field is introduced. Starting with an initial ridge, which may or may not be umbilical, a ridge line is then traced by calculating an associated integral curve of this field in conjunction with a new projection procedure to prevent it from diverging. This projection is the first that can optimize a ridge guess to lie on a ridge line uniquely and accurately. In order to follow this scheme, we not only develop practical ridge formulae but also address their corresponding computational procedures for an analytical surface patch, especially for an implicit surface. In contrast to other existing methods, our new approach is mathematically sound and characterized by considering the full geometric structures and topological patterns of ridges on a generic smooth surface. The resulting ridges are accurate in the numerical sense and meet the requirement of high accuracy with complete topology. Although the objective of this paper is to develop a mathematically sound framework for ridges on a smooth surface, we give a comprehensive review of relevant works on both meshes and smooth surfaces for readers. 相似文献
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The homotopy model: a generalized model for smooth surface generation from cross sectional data 总被引:4,自引:0,他引:4
A generalized model, called the homotopy model, is presented to reconstruct surfaces from cross-sectional data of objects using a homotopy to generate surfaces connecting consecutive contours. The homotopy model consists of continuous toroidal graph representation and homotopic generation of surfaces from the representation. It is shown that the homotopy model includes triangulation as a special case and generates smooth parametric surfaces from contour-line definitions using homotopy. The model can be applied to contours represented by parametric curves as well as linear line segments. First, a heuristic method that finds the optimal path on the toroidal graph is presented. Then the toroidal graph is expanded to a continuous version. Finally, homotopy is used for reconstructing parametric surfaces from the toroidal graph representation. A loft surface is also a special case of homotopy, a straight-line homotopy. Homotopy that corresponds to the cardinal spline surface is also introduced. Three-dimensional surface reconstruction of human auditory surface reconstruction of human auditory ossicles illustrates the advantages of the homotopy model over the others. 相似文献
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《国际计算机数学杂志》2012,89(4):445-463
An algorithm for approximating a non negative solution of inconsistent systems of linear equations is presented. We define a best approximate solution of a system Ax = b x≥0 to be the vector x≥0 which minimizes the norm of the residual r(x) = b ? Ax, for a smooth and strictly convex norm. The algorithm is shown to be feasible and globally convergent. The special case of the ? p norm is included. In particular, the method converges for 1 < p < 2. A generalization of this algorithm is also given. Numerical results are included. 相似文献
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提出了一种两步滚动的调度算法,一般情况下,与在线算法DELAY-SPT比较,滚动调度算法是比较优的。同时,也把两步滚动方法与一步滚动方法进行了比较,得出在一般情况下,两步滚动策略是较优的。 相似文献
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J. J. Steketee 《The Visual computer》1991,8(1):35-46
Principles and basic algorithms for evaluating polynomial functions by Forward Differencing (FD) and Adaptive Forward Differencing (AFD) are presented. Both techniques are used nowadays in scanning/display algorithms for parameteric polynomial surfaces by generating and displaying a set of points. Constraints to be put on such a set of points are made explicit. One FD and two AFD surface-scanning/display algorithms presented in literature are evaluated in terms of these constraints. The FD algorithm is proved to be valid, but the AFD algorithms are shown to be incorrect. A valid AFD algorithm is presented.This research was partially done at the Faculty of Technical Mathematics and Informations of the Delft University of Technology, Delft, The Netherlands 相似文献
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1 Introduction Owing to the effect of crosswind, initial disturbance and the deviation of engine parameters.etc in the initial aviation, variable rolling velocity aerocraft will produce attitude angle deviation (AAD) in the ideal orientations. It must control the attitude of the aerocraft, accordingly, AAD of aerocraft can be amended.Angle stabilization control system is used for the attitude control of rolling aerocraft by this paper. This control system is generally located in the control… 相似文献
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由于受横风、初始扰动和发动机参数偏差等因素的影响,变滚转速率飞行器在飞行过程中的飞行姿态将会发生变化.从而导致其实际飞行轨迹偏离预定飞行轨迹。本文利用AVR微控制器ATmega16及相应的信号调理电路。进行姿态控制器的设计,采用鉴频鉴幅方法对飞行器姿态角偏差进行处理,能够有效地修正飞行器姿态角偏差,完成对飞行器在变滚转速率飞行状态下的自适应姿态控制。 相似文献
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在旋转弹高速自旋的情况下,传统角速率陀螺测量滚转角时无法克服角速率量程和测量精度的矛盾,不能准确测量旋转弹弹体姿态。针对这一问题,在保证旋转弹的制导方式高度自主的前提下引入地磁信息,设计了一种高精度、适用于大动态范围的旋转弹姿态测量算法。着重针对滚转角的测量提出了一种新的解算思想,将滚转角以旋转弹横截面内的地磁矢量为界进行分解,并给出了结合地磁测量信息的偏航角、俯仰角计算公式。仿真结果表明:利用测量旋转弹姿态的算法是可行的,且精度高,值得推广。 相似文献
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针对三维扫描或三维重建获取的散乱点云数据曲面重建问题, 提出基于拉普拉斯规则化的高阶平滑算法。首先, 计算点云数据的包围盒并离散化得到体素空间; 其次, 在体素空间根据隐式曲面的梯度和点云位置、法向信息建立目标函数, 并通过对目标函数的拉普拉斯规则化达到控制重建曲面光顺效果的目的; 再次, 根据最优化原理将重建问题转换为一个稀疏线性方程组求解问题; 最后, 通过步进立方体算法得到重建曲面的三角网格表示。定性和定量的实验结果表明, 该方法重建曲面绘制效果和精确度优于常用的Poisson方法。 相似文献
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冷连轧生产是较早引入仿真技术进行辅助研究与开发的领域之一,目前已取得了大量的成果。但大多数仿真研究局限于模型的静态机理建模,难以适应复杂环境的变化,造成了很大偏差。该文以轧制力为例,研究机理和数据的结合,从而修正轧制力的模型,实现轧制力参数的预报。轧制力是冷连轧生产的关键力能参数之一,为提高预报精度、缩短自适应过程的时间,研究轧制力建模,并进行仿真研究很必要。文章讨论了仿真系统模型的类型和建模方法,对冷连轧轧制力模型进行了机理推导,并运用智能方法对轧制力参数进行回归和分析。结果表明,采用机理建模和辨识建模相结合的方法,可以建立较精确的轧制力模型,为轧制过程模型的建立及优化提供了成功的范例。 相似文献
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在钢板轧制过程中,由于温度、板坯塑性形变率、压下比等因素的影响,终轧钢板的形变总是不均匀的.为此本文结合厚板生产工艺分析了立辊轧制在厚板平面形状控制中的作用,它的研究应用在板型平面优化控制中提供了很好的技术支持. 相似文献
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王纪锋 《自动化与仪器仪表》1994,(3):35-38
输出辊道系统是热连轧机系统的一个子系统。本文设计研究的是某钢铁厂大型热连轧机输出辊道系统,它具有较为复杂的工艺过程。所以,在其速度控制方案设计中重点研究、论述了方案设计,提出了表征工艺过程的速度图及其励磁控制方案。同时,也提供了一套能够满足工艺速度图的单元电路“速度信号控制单元──SXK”。 相似文献
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文章提出了基于扩展有向图的产品参数化模型,将各类约束在形式上利用对象及相关概念统一起来,利用扩展的有向图表示设计对象及对象间的约束关系。对于有环的有向图,在正向约束求解的基础上,引入了反向约束求解,局部调整的机制。模型的主要思想是:求解过程中利用对象本身所具有的性质进行充分推理、判断,在此基础上进行约束的最小方程组计算。 相似文献
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为有效解决构造光滑曲面的三角网格插值问题,将Gregory四边形面片的易控性嫁接到Bézier三角面片上,提出一种新型双三次Gregory三角面片的插值模型.因为公共边界处的G1连续仅取决于2个相邻三角面片的控制点或向量,而无其它连续性限制,所以,该方法可有效消除使用Gregory四边形面片时需分割三角域产生的扭曲现象.实验结果表明,使用该模型对给定的三角网格进行插值,总能生成G1连续的光滑曲面. 相似文献
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针对轧机厚度控制系统设计周期长,现场调试费用高及调试风险大等问题,采用虚拟仪器技术设计实现了一个离线、安全、可靠的仿真实验平台.以某2500mm轧机为研究背景提取其数学模型,在一台PC上建立轧机的动态仿真模型(仿真机),代替现场轧机来验证厚度控制系统.仿真机接人与反馈信号均通过内置的NI数据采集卡的I/O口与控制系统相连接,并且所有接入与反馈的信号与现场轧机保持一致.实验结果表明仿真平台验证的控制系统能够直接应用到现场中,并达到了理想控制效果.仿真思想为一些不可直接实验操作的大型控制对象的控制系统设计提供了一条新路径. 相似文献
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张璐佳 《计算机测量与控制》2019,27(7):74-78
现有基于PLC的隔振器滞回动力自动控制系统存在控制误差高的不足,为此设计了一种基于动态矩阵控制算法的自动控制系统。系统的硬件部分由动态控制中心、伺服电机、动力传感器、前置信号放大器、及数据计算单元等关键的模块构成,为提高系统的控制性能在伺服电机模块中内置了型号的单片机控制器,保证电磁控制信号的稳定输出;依据动态矩阵控制算法原理设计了自动化控制系统的主控程序,并给出了动态预测矩阵控制的基本流程,利用动态滚动预测的模式来降低控制时域内的误差,并保证滞回动力值的稳定输出;分析数据表明,提出的自动化控制系统在功能性方面可以满足批量测试及远程控制的要求,在3个稳态值条件下的系统误差都明显低于传统隔振器控制系统,最高的误差输出在0.05之间。 相似文献