基于转化邻接矩阵的含复铰运动链描述与同构识别

针对机构分析与综合中复合铰链难以处理和含复铰运动链同构识别困难的问题,分析复合铰链的内部结构,提出引入Pin构件将复合铰链转化为多个并联单铰链的新方法,从而将含复铰运动链转化为只含单铰的简单运动链。定义运动链转换邻接矩阵,用于描述含复铰运动链,通过分析发现该矩阵的内涵性质丰富,方便运动链的分析。提出运用转换邻接矩阵的阶数、对角线元素矢量、矩阵特征值和特征矢量等参数识别判断含复铰运动链同构关系的方法,这些特征参数是含复铰运动链的不变量。实例证明,利用转化邻接矩阵可简单、方便、直观地描述含复铰运动链,其特征值和特征矢量用于识别含复铰运动链的同构关系,具有准确、高效和简便的特点。定义的转化邻接矩阵及其运用方法为复合铰链的处理以及含复铰运动链的识别提供了新的途径。     

ADJACENT MARTIX METHOD OF IDENTIFYING ISOMORPHISM TO PLANAR KINEMATIC CHAIN WITH MULTIPLE JOINTS AND HIGHER PAIRS

The adjacent matrix method for identifying isomorphism to planar kinematic chain with multiple joints and higher pairs is presented. The topological invariants of the planar kinematic chain can be calculated and compared by adjacent matrix. The quantity of calculation can be reduced effectively using the several divisions of bars and the reconfiguration of the adjacent matrix. As two structural characteristics of adjacent matrix, the number of division and division code are presented. It can be identified that two kinematic chains are isomorphic or not by comparing the structural characteristics of their adjacent matrixes using a method called matching row-to-row. This method may be applied to the planar linkage chain too. So, the methods of identifying isomorphism are unified in the planar kinematic chain that has or hasn't higher pairs with or without multiple joints. And it has some characters such as visual, simple and convenient for processing by computer, and so on.     

一种进行运动链和机构同构判定的新方法

提出了一个用来检测多个平面运动链之间的同构对象的新的恒量序列,该恒量序列把杆的级别和运动副的类型、自由度都考虑在内,被称为改进了的各杆总距离等级序列。并提出了一个用以得到这个恒量序列的算法。同时,本文还提出了一个用于检测给定的一个运动链中的非同构机构的计算机辅助方法     

利用邻接矩阵的幂序列进行运动链和机构的同构判定

从同构的图论意义出发,提出了一个新的运动链结构不变量,进而提出了利用邻接矩阵的幂序列进行运动链同构判定的方法。它与现有的其他方法相比,具有直观、简便和显明图论依据的特点,且该方法不仅可以实现运动链的同构判定,而且可以成功地判定一般图的同构。在此基础上,本文最后给出了从同一运动链中识别出不同机构的两个方法。     

平面多杆机构杆组自动生成方法

阿苏尔杆组理论指出,通过对不同运动链选取不同的机架和原动件,能够得到各种可能的阿苏尔杆组与机构构型。基于这一理论提出一种阿苏尔杆组的自动生成方法。针对杆组的结构特点,提出简单易行的杆组同构判别方法,该判别方法也适用于平面多杆机构运动链的同构判别。联合应用运动链的邻接矩阵与关联矩阵,使得自动生成算法与计算机编程相结合,实现了平面多杆机构杆组的自动生成。该自动生成机构杆组的方法理论简单,编程可操作性强,能够实现多杆运动链在构成机构时杆组的准确快速的拆分。该方法将杆组的拆分过程与由杆组搭接形成机构的过程相联系,对拆分得到的所有杆组与机构构型进行同构判别,得到了六杆以内的13种杆组,以及由八杆运动链构成的153种机构。     

Hierarchical clustering approach for determination of isomorphism among planar kinematic chains and their derived mechanisms

The problem of isomorphism among kinematic chains and their derived mechanism has been a hot area of research from last several years. The researchers so far have proposed many methods which are mainly based on characteristic polynomial and some code based methods to test the isomorphism among kinematic chains. In this present communication a hierarchical clustering based computerized method is proposed for the above said problem and it is tested for planar kinematic chains upto twelve links without any counter examples. In this method a hierarchical clustering algorithm is also developed for the identification of distinct mechanism derived from kinematic chains. In this method kinematic chains are represented in the form of weighted squared shortest path distance matrix and this matrix is further transformed in the form of tree or dendrogram with the help of hierarchical clustering algorithm. This algorithm directly gives the number of distinct mechanism derived from a given kinematic chain. The cophenetic correlation coefficient of dendrogram is used as an index for isomorphism identification among kinematic chains. The proposed method is efficient and accurate and only one matrix for a given kinematic chain is developed for the determination of distinct mechanisms. This method is successfully examined for one degree of freedom, 6, 8, 10, 12 links planar kinematic chains, 9 links two degree of freedom and 10 links three degree of freedom planar kinematic chains. The computer algorithm for the proposed method has been proposed which can easily be converted into a computer program. These results are useful for designers to detect isomorphism in mechanisms derived from kinematic chains and duplication among kinematic chains.     

用邻接矩阵判断含复铰平面运动链同构和拓扑对称的新方法

提出了含复铰平面运动链同构和拓扑对称性判断的邻接矩阵方法。通过适当地定义运动链的邻接矩阵,在结构特征相同的情况下,比较两运动链邻接矩阵的结构,即可完成同构判断。通过邻接矩阵可得到构件或铰链点的广度优先生成树,比较生成树的结构特征,即可确定构件或铰链点的拓扑对称关系。研究表明,该方法具有简便、可靠、计算工作量小和便于用计算机处理等特点。     

RESEARCH ON ADAPTIVE DATA COMPRESSION METHOD FOR TRIANGULATED SURFACES

NC code or STL file can be generated directly from measuring data in a fas re-verse-engineering mode. Compressing the massive data from laser scanner is the key of the new mode.An adaptive compression method based on triangulated-surfaces model is put forwar. Normal-vectoranges between triangles are computed to find prime vertices for removal. Ring data structure isadopted to save massive data effectively. It allows the efficient retrieval of all neighboring vertices andtriangles of a given vertices. To avoid long and thin triangles, a new re-triangulation approach based onnormalized minimum-vertex-distance is proposed, in which the vertex distance and interior angle oftriangle are considered. Results indicate that the compression method has high efficiency and can getreliable precision. The method can be applied in fast reverse engineering to acquire an opimal subsetof the original massive data.     

基于杆组邻接矩阵的平面机构综合方法

为在平面机构综合中能够求解出包含R副和P副的全部运动链,给出一种基于杆组邻接矩阵的平面机构综合新方法。通过对前期研究提出的杆组邻接矩阵进行修正,构造改进的杆组邻接矩阵。基于改进的杆组邻接矩阵,求解给定杆组的所有装配方式,并同步辨识同构体,获取杆组装配关系的杆组邻接矩阵。根据提出的约束条件,采取逐级构造杆组邻接矩阵方法,求解杆组间的可行连接方式,并同步辨识同构体,从而获取全R副杆组间的连接关系的杆组邻接矩阵。将所有类型杆组代入求得的杆组连接关系矩阵,获取所有类型杆组可构成的全部机构构型,包含主动件和机架变换问题。以平面6杆机构为例,应用该方法首次求出包含R副和P副的所有机构构型为364种,验证了提出的综合方法的有效性和实用性。     

一个多边形快速等距偏移方法

多边形的等距偏移是CAD/CAM领域中的一个基础性问题 ,是型腔环切加工刀具轨迹生成的关键。根据无效环在原始多边形上的对应连续线段必有一凸或凹点 ,从多边形的凸点和干涉凹点出发 ,利用干涉边的连贯性逐步确定无效环 ,最后对多边形中的非干涉区域作等距偏移 ,实现多边形的等距偏移。该方法利用干涉区域的连贯性避免了大量不必要的求交计算 ,同时支持带有孤岛的多边形等距偏移。其算法复杂度接近于O(n) ,其中n为多边形顶点个数。     

Adding sub-chain method for structural synthesis of planar closed kinematic chains

For at least the past five decades,structural synthesis has been used as a main means of finding better mechanisms with some predefined function.In structural synthesis,isomorphism identification is st...     

平面运动链同构识别的距离和序列法

对平面机构运动链结构组成进行探讨后,研究了运动链中的结构不变量,并基于缩杆邻接矩阵提出了4个新的运动链结构恒量序列,这些恒量序列将杆的级别、运动副数目以及各杆的连接关系考虑在内。以此为基础,提出了对运动链进行同构识别的距离和序列法。该方法实质上是对运动链进行分类同构识别,因此具有操作简单、可靠性好、识别效率高等特点,已成功应用于12杆以下机构运动链型综合时的同构识别     

A systematic method of adaptive joint design considering different assembly sequence in sheet metal product

In sheet metal assembly, not only the component variations and tool errors, but also the component structure (joint type) and assembly process (assembly sequence) affect the final dimensional quality. In this paper, a systematic method for adaptive joint design considering different assembly sequence is proposed to meet the in-process dimensional adjustability of KCs (key characteristics). First, the adaptive characteristic of the sheet metal joint is depicted. Then, the mathematical model in order for concurrently optimizing both joint type and different assembly sequence is presented. How to evaluate the combination of joint type and assembly sequence is carried out according to two conditions: (1) for single KC, and (2) for multiple KCs. The KC confliction is considered to ensure the important KCs. Genetic algorithm is used to resolve the optimization of joint design. An example is chosen to demonstrate our method finally, and various joint designs are acquired according to different assembly sequences by this means. The proposed methods make it possible for us to improve the dimensional quality of product in the design stage.     

运动链拓扑胚图的同构判断

平面并联机构基于胚图的综合方法中,拓扑胚图的同构判断是关键的环节。针对不含二元杆的运动链拓扑胚图,解决它们之间的同构判断问题。运动链的拓扑胚图与拓扑图相比有着独特的个性,由于在支链上没有二元点,所以图的顶点之间的关系主要是顶点之间的相对位置。根据拓扑胚图的特性,从关于图的邻接矩阵的经典理论出发,建立图的任意顶点之间的路径数矩阵,将路径数矩阵的元素按照一定规则排列成路径数组。论证了拓扑胚图同构的条件。在度序列和一阶路径数组相等的前提下,利用二阶路径数组来判断拓扑胚图是否同构。举实例说明判断过程及具体应用。拓扑胚图同构判断问题的解决不仅为基于胚图的型综合奠定了基础,而且对于某些运动链拓扑图的同构判断也具有普遍意义。     

基于蒙皮模型和WEOPA的人体外形和运动跟踪

为了解决多关节人体三维外形和运动跟踪问题,提出了一种基于蒙皮模型(skinned model)和加权扩展正交普鲁克分析(weighted extended orthogonal procrustes analysis,WEOPA)的三维人体外形和运动跟踪方法。首先使用Shape-From-Silhouettes方法从当前帧多目视频图像轮廓中计算出被跟踪人物的可视外壳,然后建立人物先验蒙皮模型并与之匹配,其中蒙皮模型的引入使得多关节人体三维外形和运动跟踪问题被转化为一个分层非线性最小二乘匹配问题。考虑到在先验模型获取中肢体间连接部位产生的网格顶点粘连问题,采用WEOPA算法来进行求解,其中通过引入4种不同的权值分配策略,克服了顶点粘连对匹配的影响,并有效利用了匹配点对的几何法线信息。实验结果表明,该方法能对人物外形和运动进行有效的跟踪。     

用拓扑特性矩阵辨识运动链的同构体及机架变换研究

基于运动链的基本环路及环路中构件、运动副的互相连接关系，建立了描述平面和空间运动链及机构的拓扑特性矩阵，对平面、空间运动链及机构的同构体辨识问题进行了研究。由于拓扑特性矩阵较常用于同构体辨识的邻接矩阵、关联矩阵等矩阵的元素少，而且可以通过比较拓扑特性矩阵的对应行列的元素直接进行同构体的辨识，因此，应用拓扑特性矩阵辨识同构体是更简便和高效的。给出了应用拓扑特性矩阵辨识同构体的方法、步骤及流程图，并给出了较典型的辨识例子（包括空间运动链），证明了该方法的正确性和高效性。同时还应用拓扑特性矩阵对运动链的机架变换问题进行了研究。     

基于改进ECT的隔热材料胶层无损检测研究

电容层析成像(ECT)技术是能显示被测物场的二维或三维介质分布图像的实时检测技术,基于平面阵列传感器的ECT系统为陶瓷多孔隔热材料缺陷检测提供一种新的技术途径。本文针对陶瓷多孔隔热材料粘结胶层的缺陷无损检测问题,提出了一种基于改进的电容层析成像方法。首先在分析平面阵列传感器ECT检测系统模型及成像原理的基础上,提出了一种改进初值的Landwebe迭代图像重建算法;进一步将该算法应用到基材表层与隔热材料之间的粘结胶层的缺陷检测领域,并通过实验验证了采用基于改进ECT的无损检测方法在陶瓷多孔隔热材料粘结胶层缺陷检测中应用的有效性;同时与采用传统ECT成像算法的检测实验进行比较。结果表明本文提出的改进ECT算法对胶层缺陷图像重建质量具有较大幅度的提高。     

机械CAD三角网格模型的特征表面分割混合算法

针对机械CAD三角网格模型中普遍存在的网格稀疏性和非均匀性分布等特点，提出了一种特征的二次提取及表面分割混合算法。第一次分割采用基于边的方法，即在平面合并的基础上对相邻三角面片法矢夹角的方差进行判断和处理，从而实现平面与其他稀疏网格表面区域的分割和边界特征的提取；第二次分割采用基于顶点的方法，首先由顶点的估算曲率计算出各面片的近似曲率，然后通过区域生长实现其他表面区域的分割及特征提取。实验结果表明，该方法能较准确地实现机械CAD三角网格模型的特征提取和表面分割。     

平面Ⅲ级杆组构形研究

运用“可能域”的概念建立起模型空间,得到平面Ⅲ级杆组的所有可能构形。再根据排列组合论和运动链同构判定的邻接矩阵法证明,在全转动副的基础上,含R、P副平面Ⅲ级杆组可演化成其它19种不同的构形。