基于MDT的参数化产品设计

提出了一种基于ＭＤＴ的参数化产品设计方案。该方案使产品的几何和非几何特性全部参数化，并通过定义变量间的函数并联，在外部建立数据源，然后导入到ＭＤＴ中，实现对产品所有几何和非几何变量的动态驱动，使设计工作的主要任务集中到非几何参数的求解上。叙述了实施该方法的基本过程和要点，并以压力容顺的参数化设计为例，阐述了该方案在设计实践中的应用。     

基于变分几何的参数化造型系统的研究与开发

基于约束的参数化几何造型技术是一种新型、快速的造型方法。本文应用变分几何技术开发了一个参数化几何造型系统——VGPDA。该系统具有自动搜索约束关系,生成约束方程组,进行约束关系一致性识别以及采用符号微分方程法快速求解约束方程组等功能。     

基于MDT的参数化产品设计

提出了一种基于MDT的参数化产品设计方案。该方案使产品的和非所有几何和非几何物特性全部参数化 ,并通过定义变量间的函数关联 ,在外部建立数据源 ,然后导入到MDT中 ,实现对产品所有几何和非几何变量的动态驱动 ,使设计工作的主要任务集中非几何参数的求解上。叙述了实施该方法的基本过程和要点。并以压力容器的参数化设计为便 ,阐述了该方案在设计实践中的应用。     

基于特征的三维参数化造型

基于特征的参数化几何造型是一种新型、快速的造型方法。在开发特征造型工具系统ＦＭＴ的基础上，进一步对三维参数化造型方法作了探讨和研究，特别是对参数化特征造型的表达模式、约束方程组的建立以及稳定、快速地求解约束方程组等一系列关键技术作了较深入的研究，提出了一套三维参数化造型方案。     

准双曲面齿轮几何参数计算方法的研究

介绍了求解准双曲面齿轮几何参数的基本原理.通过分析格里森求解方法的计算过程,建立了几何参数的迭代方程.在这些方程基础上,提出了一种几何参数计算的新方法.最后给出一个计算实例对新方法进行了验证说明.     

一种基于参数化CAD软件进行机械系统动力学求解的方法

传统动力学求解通过对机械系统进行简化,建立动力学方程求解得到解析结果,这种方式较为繁杂且费时费力;文中通过在常用的参数化CAD软件中对机械系统动力学模型进行几何建模,然后调用CAD软件几何求解器求解,最终可以方便而快捷地解决机械系统的动力学问题.     

面向材料反求的非均质体参数化模型构建

非均质产品具有非常广泛的运用,面向材料反求构建非均质产品模型,能更好地设计出材料符合实际分布的非均质产品。利用CT扫描提供的原始数据,经过提取得到具有灰度信息的点云数据,提供非均质产品几何和材料空间构造原始信息。通过体参数化方法实现模型几何空间构造,通过对灰度值的参数化实现材料空间构造;通过求解一个二次型优化问题,将材料空间内嵌于几何空间,实现几何空间和材料空间的耦合,从而最终完成体参数化非均质产品模型的构建。以股骨模型为例,实现其非均质体参数化模型的构建算法。结果表明,面向材料反求的非均质体参数化建模方法能够更为便捷和准确的表达材料实际分布信息,且为基于体参数化模型的性能分析和显示提供模型支撑。     

基于ANSYS的螺旋状预埋件的参数化建模与分析

基于ANSYS有限元分析软件,利用其参数化设计语言APDL,定义了螺旋状预埋件的几何参数,实现了螺旋状预埋件的参数化建模、参数化载荷施加与求解,进而实现参数化有限元分析的全过程.不仅提高了此类问题的建模与分析效率,也为类似问题的解决提供了一条新途径.     

子午加速轴流风机几何参数的优化计算

本文从给定设计参数的条件下,推导出子午加速风机的基元级效率与风机几何参数的解析关系式,进而建立求解风机最佳几何参数的数学模型。然后应用最优化原理和方法,求解了在不同设计参数条件下的子午加速风机的最佳几何参数。试验结果表明用本文所提出的方法确定几何参数的叶轮,其效率较高、性能较好。     

直齿圆柱齿轮精密成形挤压型腔的参数化建模方法

齿轮精密成形是直齿圆柱齿轮成形的必然趋势,但其挤压型腔的数学模型建立困难,往往导致参数不易求解和优化。笔者提出了基于齿轮挤压型腔的参数化数学建模方法,利用Bezier曲线描述挤压型腔轴向变化规律和Pro／Engineer软件对其进行几何建模,使挤压型腔CAD／CAM一体化成为可能。     

几何约束等价性及等价迭代研究

针对几何约束系统中不可构造的柔性复合顶点的求解问题,引入等价约束,分裂部分约束以打破柔性复合顶点的强耦合性,形成只包含简单顶点的求解序列。基于等价约束的性质和结构拓扑,研究了求解序列顶点存在与不存在实数解情况下,雅可比矩阵的求解方法,从而以少量分裂约束方程组对等价约束变量的等价迭代,或者柔性复合顶点的局部迭代,取代柔性复合顶点的整体数值迭代求解,降低迭代的维数,算法实现于几何约束求解引擎CBA(constraint broadcast automa-tion)中。     

An angular constraints solving approach for assembly modeling based on spherical geometry

In this paper, a novel approach for solving angular constraints based on spherical geometry is presented. This method can determine the orientation of a set of parts given the mating constraints between them with the decoupled property of the angular and distance constraints. The combination of angular constraints can be categorized into two cases: operable and un-operable. The former can be solved efficiently by introducing simple spherical surface reasoning. The latter is solved by employing spherical surface four-linkage mechanism. In this way, the rotation transformation matrix of the dependent rigid body is worked out. This new method has the advantages over numerical approach and symbolic approach of clear geometric solubility, geometric operability, and avoiding simultaneously solving all the constraint equations in the model. Moreover, it is an easy and efficient way to determine whether there exist redundant constraints. The presented algorithm has been successfully implemented in our assembly prototype system, InteVue.     

一种基于约束的多视图尺寸驱动方法及实现

提出一种基于约束的多视图尺寸驱动的方法。该方法是通过建立一组具有参数化特性的、扩展的图形数据结构，用统一的形式来表示多视图间图形的几何元素和几何约束，由系统内部自动建立起多视图的参数化模型，进而实现多视图间的尺寸驱动。     

A symplectic pseudospectral method for nonlinear optimal control problems with inequality constraints

A symplectic pseudospectral method based on the dual variational principle and the quasilinearization method is proposed and is successfully applied to solve nonlinear optimal control problems with inequality constraints in this paper. Nonlinear optimal control problem is firstly converted into a series of constraint linear-quadratic optimal control problems with the help of quasilinearization techniques. Then a symplectic pseudospectral method based on dual variational principle for solving the converted constrained linear-quadratic optimal control problems is developed. In the proposed method, inequality constraints which can be functions of pure state, pure control and mixed state-control are transformed into equality constraints with the help of parameteric variables. After that, state variables, costate variables and parametric variables are interpolated locally at Legendre-Gauss-Lobatto points. Finally, based on the parametric variational principle and complementary conditions, the converted problem is transformed into a standard linear complementary problem which can be solved easily. Numerical examples show that the proposed method is of high accuracy and efficiency.     

3D geometric constraint solving using the method of kinematic analysis

In this paper, an approach based on kinematic method for solving 3D geometric assembly constraints is presented. The relative generalized coordinates and generalized recursive formulations used in kinematic analysis are utilized to reduce the size of constraint equations. Based on the cut-constraint method, this approach can be used to solve all kinds of configurations. In the case of an open-loop constraint system, the geometric constraints can be satisfied by sequentially determining the values of relative generalized coordinates. With respect to a closed-loop constraint system, the proposed approach converts it to a spanning tree structure by cutting constraints and introducing cut-constraint equations. Furthermore, a topological analysis method is also developed to obtain the spanning tree with the minimal number of cut-constraint equations, and the analytical Jacobian matrix of cut-constraint equations is derived to enhance computational efficiency. In the end, the proposed approach is demonstrated and validated using two examples of closed-loop geometric constraint system.     

Parametric process planning based on feature parameters of parts

This paper presents a model parametric process plan that is dependent on feature parameters of parts, and proposes a solution for the automated process planning of part families. Based on the parametric process plan templates for part families and the feature parameters of new parts, a prototype system is developed. First, parts are grouped into families considering their geometric or manufacturing similarities, and the parametric process plan template is pre-created for each family. Then, to plan the process of a new part, the system extracts feature parameters from its feature-based model and generates an a parametric process plan by searching the template library and solving related constraints. Finally, the system outputs the process plan sheets, if necessary. Although the system cannot creatively generate process plans for brand new parts, the system can meet two important requirements of the real industrial world to CAPP systems, that is good system performance and rapid response.     

Generation of rotation matrix for assembly models with arbitrary angle constraints

Assembly modeling, which is established by geometric constraints, plays an important role in product design. However, most constraint solving methods are only applicable for the cases in which the orientation constraints between base and mating component are either fit or against. This paper presents a modified geometric constraint solving method. It allows arbitrary angles for the orientation constraints and implements them into rotation matrix that determines the relative orientation of a mating component to a base component. The method transforms the constraints to a set of nonlinear equations firstly, and then solves it algebraically instead of using numerical methods.     

Adaptive feedrate interpolation with multiconstraints for five-axis parametric toolpath

A good adaptive feedrate will be helpful for improving machining accuracy and efficiency, as well as avoiding the excess of the machine’s physical capabilities and feed fluctuations during machining. Therefore, it is highly desirable to consider the constraints of geometric error, cutting performance, and drive constraints in the feedrate scheduling of the parametric curve interpolator for five-axis computer numerical control machining. In this paper, a novel multiconstraints feedrate scheduling method is proposed for the parametric curve interpolator in five-axis machining. In the method, the feed optimization model is first built with the constraints of geometric error, the maximum feedrate and acceleration of cutter tip, and the maximum feedrate and acceleration of five-drive axes. Then, the relations between each constraint and the cutter tip feedrate are derived by means of near arc length parameterization. After that, a linear programming algorithm is applied to obtain the optimal feed profile on the sampling positions of the given tool path. Finally, illustrated examples are given to validate the feasibility and applicability of the proposed feedrate scheduling method. The comparison results show that the proposed method has an ability of the simultaneous guarantees of geometric accuracy, cutting performance, and drive characters of machine tools.     

基于普通算法进行几何推理的参数化设计方法

提出了一种基于普通算法进行推理的参数化设计方法。该方法引入了建立和管理参数化模型的新策略 ,通过扩展一般的图形数据结构统一表示几何约束 ,基于普通算法实现几何推理。在此基础上开发了面向对象的参数化设计系统 ,验证了此算法的有效性     

面向广义优化的参数化设计方法研究

提出一种将广义优化模块与参数化设计集成的方法及其集成策略，详细探讨了产品广义优化模型和参数化模型的关系协调、变量映射构建、几何约束处理以及自动再生算法，借助于Pro／E参数化软件强大的干涉检验和三维可视化功能，实现了产品全过程和全性能的广义优化及优化结果的可视化。提出的方法在液压挖掘机设计中得到了验证。