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.     

基于再生运动链法的锁芯机构创新设计

在分析现有锁具机构的基础上,应用机构再生运动链设计法对机构进行还原再生,找出满足拓扑要求与约束要求的非同构运动链,从而实现新锁具的机构创新。首先应用一般化原则将现有玥玛空转锁芯机构转化为与之对应的一般化链;然后运用数综合理论,对原型的机构运动链进行还原,找到所有可能的具有相同构件数和运动副数的一般化运动链图谱;再根据设计要求与约束对运动链进行元件识别,从而得到可行特定化链;最后由可行特定化链具体化为新的锁芯机构方案简图。利用三维软件对新设计的锁芯机构进行三维建模并分析其工作原理,结果表明设计的锁芯机构是合理的,并申请了2项国家发明专利。     

实现装载机车架流水线装配

通过对装配现场的分析,分别设计制作了移动式全自动前后车架装配板链线,对延续多年的前后车架地摊搭架式装配进行了重大改进,使得员工工作环境得到了明显改善,工作效率得到大幅提升。设计了三维立式工作吊架,通过制作工装保证轴承的位置,并通过小型油压机将轴承快速压型到位,效率高,大大降低员工的劳动强度,同时不使用铜棒敲击,避免了噪声,改善了装配现场环境,提高了轴承的装配精度。装配产能也提升到了8分钟/台,装配效率提高50%。     

An integrated design of quasi-zero stiffness mechanism

Nonlinear Quasi-zero stiffness (QZS) mechanisms were studied to overcome the weakness of linear isolators. This paper presents an integrated design of the QZS mechanism. First, various types of QZS vibration mechanisms are analyzed and a generalized model for QZS mechanisms is derived. The generalized model consists of two main parts: link and horizontal spring. The motion equation of the QZS mechanism is a Duffing equation with nonlinear stiffness. Based on the generalized model, the design problem of the QZS mechanism is converted into the kinematic design of a link element. For simplicity, the link is generalized with a cam-roller mechanism. The integrated design approach shows that the QZS mechanism can have desired QZS characteristics with properly designed cam geometry.     

Multicriterion optimization of the kinematics of the spatial mechanisms of passenger car wheel suspensions

Four spatial mechanisms simulating passenger car wheel suspensions and steering linkages and power drives are considered. A structural analysis of the mechanisms is provided. A method for calculating the coordinates of characteristic points and the main kinematic characteristics of these mechanisms is proposed. The problem of multicriterion optimization of the kinematic characteristics is defined. A subproblem of the multicriterion optimization consists in the synthesis of a mechanism ensuring the required motion of a wheel. Some optimization results are presented.     

基于运动链再生创新设计理论的冲击攻丝机的研制

冲击攻丝是国外最近开发出来的一种全新的螺纹加工方法。本文详细介绍了冲击攻丝机的结构和工作原理。为了避开现有的专利设计,本文把运动链再生创新设计理论应用到冲击攻丝机上,经过原始机构分析、一般化运动链、数综合、定义设计约束和再生运动链过程,由此得出6种新的运动链,再将这些新的运动链具体化为机构,从而得到6种具有自主知识产权的创新机构。     

轮式移动机器人运动学建模方法

研究轮式移动机器人运动学建模方法问题。提出用于不规则地形下的轮式移动机器人运动学建模方法——轮心建模法(Wheel-center modeling,WCM)在分析多刚体链式机构运动的速度特性以及不规则地形上轮式移动机构转动角速度特性的基础上,建立车轮轮心速度的矢量表达式,即确立WCM。以六轮摇臂转向架月球漫游车的运动学建模为例,分析各关节转动角速度矢量在车体坐标系下的投影,并根据转动矢量方向在车体坐标系中变化与否,将矢量叉乘的投影写成不同的形式,利用车轮轮心坐标系、轮地接触坐标系相对于车体中心坐标系的齐次变换矩阵中的相应元素,将车轮轮心的速度矢量表达式投影到车体中心坐标系下,建立车体运动学模型,从中阐述WCM的方法和过程,并分析WCM的特点。用试验和仿真验证该建模方法的正确性。     

平面闭式运动链简图自动绘制的最大环路法

机构运动链结构简图的自动绘制,直接关系到机构设计的效率与可靠性。在对平面闭式机构运动链的拓扑特性研究基础上,基于缩杆邻接矩阵,提出一种运动链结构简图自动绘制的最大环路方法。此方法采用广度优先生成树算法获得运动链的独立回路,并通过独立回路的加减运算得到最大可行外环。根据回路关系逐步修正最大可行外环,使各独立回路成为其非交叉规范化内环。在运动链结构简图绘制过程中,根据外环和内环情况,将运动链中的运动副布置在由外往内的同心圆内接正多边形的顶点上,使绘制的运动链简图规范、美观。在对这种基于外环与内环关系的简图自动绘制算法研究过程中,借助多个机构实例进行说明。研究与应用结果表明,最大环路法具有实现简单、方法完备的特点,适用于多杆多自由度平面闭式运动链结构简图的自动绘制,应用于机构设计中,可极大地提高设计效率。     

自适应机构的综合方法

根据自适应机构的结构特征，分析了其运动链的自由度规律，并且对相应的自由度综合出了所有可能的运动链。在此基础上，对此类机构的运动链的选择和功能结构化设计进行了讨论，总结出了一般性的原则和方法，为自适应机构的综合创新方法提供了借鉴。     

A manufacturing model of helical groove on rotary burr and a universal post processing method

A systematic machining theory and precision method to determine cutter location in a grinding system is presented for rotary burr. First, the helical cutting edge on various kinds of revolving surfaces is built. Then, based on the geometry model of the helical cutting edge, the smooth spiral rake surface with constant normal rake angle and flank surface can been formed during the one-pass grinding process by this method. No interference between the grinding wheel and workpiece happens by the wheel special rotation. The method has the characteristic of detaching the grinding wheel path solution from specified machining conditions. The grinding wheel path is suitable for different NC machine tools through post processing. Meanwhile, a mechanism kinematic model of the NC machine tool is built, and a generalized algorithm for post-processing of multi-axis NC machine tools is presented. This model is applied to arbitrary configuration of NC machine tool, and the motion value for each axis will be generated by the inputting structure and motion parameters of the machine tool. The model, together with the machining method mentioned in this paper, make the calculation and generation of the grinding wheel path simpler and universal. At last, the validity of the method given in the paper is identified by an example of grinding.     

Vibro-acoustic Radiation Characteristics Analysis of Railway Vehicle Wheel with Damping Ridges Based on Modal Strain Energy

The existing researches on the damping wheel mainly focus on investigating the influence of damping structure change on the vibro-acoustic control.The changes include the geometric size of the damping structure,the damping material parameters,and the placement,and so on.In order to further understand the mechanism in reducing the acoustic radiation of railway wheel with layer damping treatment,in this paper,the wheel is simply modified by a full-sized circular plate.The circle plate side has stuck circumference constrained damping ridges and radial constrained damping ridges on it.Based on a hybrid finite element method-boundary element method(FEM-BEM),the paper develops a vibro-acoustic radiation model for such a distributed constrained damping structure.The vibration and acoustic radiation of the circular plate is analyzed.In the analysis,the dynamic response of the system is obtained by using the 3D finite model superposition method.The obtained vibration response is used as the initial boundary condition in solving Helmholtz boundary integral equation for the sound radiation analysis.In the procedure,firstly,the modal analysis of the circular plate is performed to get the distribution of the system modal strain energy.Secondly,the vibro-acoustic radiation characteristics of the plate with different kinds of circumference damping ridges and radial damping ridges are compared in order to try to find the best effective damping ridge structure.Thirdly,using the distribution of the plate modal strain energy investigates the effect of the ridge distribution locations on the circular plate on its vibro-acoustic radiation.The calculation and analysis research results show that,the sticking circumference and radial damping ridges on the plate can control the vibro-acoustic radiation of the plate effectively in different frequency range.The distribution of the constrained damping ridge has an effect on reduction in vibro-acoustic radiation of the circular plate.The present research is very useful in the design of railway wheel with low noise level.     

基于回路配置的平面机构运动链绘制新方法及其计算机实现

提出了一种根据平面机构运动链的邻接矩阵绘制草图的新方法,它首先借助运动链简图的广度优先生成树求得图的基本回路,然后将回路标准化后按照排序规则进行排序,最后依据排序后的回路自动绘制出运动链简图;还将该方法与已有的方法进行了比较和分析,并通过应用实例验证了这种方法的有效性和完备性,最后还给出了相应的计算机原型系统实现。     

Kinematic,static and dynamic investigations of a plane single-loop kinematic chain with prismatic jointsEtudes cinematiques,statiques et dynamiques d'une chaine cinematique plane,a une boucle et ayant des joints prismatiques

A plane single-loop closed kinematic chain with prismatic joints and many degrees of freedom is studied. Some formulas expressing the displacement, the velocities and the accelerations of an arbitrary order of the links by means of generalized coordinates (i.e. the distances between the sliders of the adjacent links) and their derivatives respectively are obtained making use of the intrinsic transmission functions. The equations connecting the effective forces applied to every two adjacent links are derived for the state of equilibrium of the kinematic chain by applying the principle of virtual work. The differential equations for the movement of the kinematic chain are obtained.     

新型平行分度凸轮机构的综合与仿真

提出了一种新的平行分度凸轮机构 ,它的特点是其分度凸轮具有自共轭的凸轮齿 ,使分度期凸轮具有连续的工作表面 ,从而能够提高机构的动态性能。介绍了该机构的模型和工作原理 ;通过分析和综合 ,给出了该机构存在的一组参数。应用相对运动法导出了自共轭凸轮齿的齿廓方程。基于对该机构的综合结果 ,开发了平行分度凸轮轮廓自动设计和机构运动仿真的CAD程序。设计示例表明 :新机构的运动原理是可行的     

The method of cut-joint kinematic constraint: velocity propagations

Based on a recent formulation for parametric design of mechanical systems using kinematic analysis, we reported an approach to automated design by converting mechanical part geometry into a mechanism by breaking the part into sub-parts attached by higher pair joints. In order to evaluate the performance of a mechanism where a design change has been introduced into one of its links, we extend the formulation in this paper to address the propagation of this change and its effect on the velocity of other members. This analysis will limit itself to mechanisms. Velocity propagations due to modifications in the design of a mechanical part are analytically addressed using a proposed working coordinates formulation based on the cut-joint kinematic constraint method (presented earlier). Velocity vectors in state-vector notation are derived and treated as variables such that propagations of working coordinates of a link are obtained with respect to position and orientation. The underlying theory is presented and several planar and spatial mechanisms are treated.     

Topology Search of 3-DOF Translational Parallel Manipulators with Three Identical Limbs for Leg Mechanisms

Three-degree of freedom(3-DOF) translational parallel manipulators(TPMs) have been widely studied both in industry and academia in the past decades. However, most architectures of 3-DOF TPMs are create...     

Analysis and simulation for a parallel drill point grinder

Based on the 3-PRS parallel mechanism, a new drill point grinder is presented in this paper. The relationship between the drill point geometry parameters and the grinding kinematic parameters are described for the most commonly used conical twist drill, and the grinding kinematic equation is also derived accordingly. The virtual prototype modeling and the kinematic simulation using MSC/ADAMS are then carried out for the proposed parallel drill point grinder. The related kinematic analysis, such as the displacement and velocity analysis of the drill point and grinding wheel, the rotation angle analysis of the ball joints with respect to the initial position, etc., is obtained. From the simulation results, we can see that the proposed structure is capable of implementing the function of drill point grinding. The virtual prototype simulation can help in the parametric design and the structural design for the new grinder.     

Design and analysis of the gripper mechanism based on generalized parallel mechanisms with configurable moving platform

Generalized parallel mechanisms with a configurable moving platform have become popular in the research field of parallel mechanism. This type of gripper mechanism can be applied to grasp large or heavy objects in different environments that are dangerous and complex for humans. This study proposes a family of novel (5 + 1) degrees of freedom (three translations and two rotations plus an additional grasping motion) gripper mechanisms based on the generalized parallel mechanisms with a configurable moving platform. First, the configurable moving platform, which is a closed loop, is designed for grasping manipulation. The hybrid topological arrangement is determined to improve the stiffness of the manipulator and realize high load-to-weight ratios. A sufficient rule based on Lie group theory is proposed to synthesize the mechanism. The hybrid limb structure is also enumerated. A family of novel gripper mechanisms can be assembled through the hybrid limbs by satisfying the rule. Two examples of the gripper mechanisms with and without parallelogram pairs are shown in this study. A kinematic analysis of the example mechanism is presented. The workspace shows that the mechanism possesses high rotational capability. In addition, a stiffness analysis is performed.     

新型PURU+RR+S球面并联人形机器人踝关节机构动力学性能分析

提出了一种新型PURU+RR+S球面并联人形机器人踝关节机构,根据机构的几何约束关系和速度合成定理,建立包括各个构件位姿、速度的机构运动学模型。在此基础上,考虑各构件惯性力的影响,基于虚功原理和拉格朗日方程,建立了机构动力学模型。通过实验测量,得到一组人体踝关节的运动学数据,利用傅里叶公式进行拟合,得到人体踝关节的位姿函数。将此位姿函数分别作为理论模型、踝关节虚拟样机的输出,得到踝关节机构输入的数值解、仿真数据,验证了运动学和动力学模型的正确性。研究结果为该人形机器人踝关节机构在工程中的结构设计与应用提供了动力学理论基础和依据。     

平面七杆机构混合驱动器运动链分析和综合

使用传统RTNA(realtimenon adjustable)马达和RTA(realtimeadjustable)马达混合驱动平面两自由度七杆机构 ,达到既可以提供输出的柔性 ,又可以降低费用的目的。先就平面两自由度七杆机构进行型综合 ,得到平面两自由度七杆机构的四种运动链 ;然后逐一分析每一种运动链 ,得出适合于混合驱动器的一种运动链。为平面两自由度七杆机构混合驱动器的分析和设计打下基础。