平面四杆机构的可靠性分析

将诸原始误差均视为随机变量，对平面四杆机构具有杆长尺寸误差、铰链间隙误差及磨损量等各项随机变量分别进行了分析；应用微小位移的线性叠加原理综合出各项误差导致的机构运动输出总误差，建立了机构运动精度可靠性分析模型；利用计算机数字仿真技术，考察了机构中杆长尺寸误差和铰链间隙(或磨损)误差随机变量均值和方差的改变，对机构输出运动精度可靠度的影响，从中获得了一些有意义的结论。     

VB在平面四连杆机构运动分析中的应用

介绍了基于VB实现对平面四连杆机构进行全面运动分析的方法.通过一种简单有效的方法建立了数学模型,采用计算机模拟技术,能动态演示机构的运动和自动绘制连杆上任意点的轨迹曲线,并能输出各运动构件的位移图、速度图和加速度图.为平面四连杆的运动分析提供了一条简单易行的途径.     

3-RRR平面并联机构刚度分析

刚度是并联机构重要性能指标,为了评价并联机构刚度,提出了一种刚度评价方法.基于3-RRR机构的逆运动学模型,推导出其雅可比矩阵.在力雅可比矩阵的基础上,给出了刚度评价指标,该指标不仅适用于3-RRR并联机构,而且可以应用于其它并联机构.将提出的刚度指标应用于3-RRR并联机构,数值仿真结果表明3-RRR机构在工作空间中具有对称的刚性.     

Characteristic surfaces for extreme values of angular velocity ratio in planar four-bar mechanisms

The extreme values of the angular velocity ratio of a planar four-bar mechanism are considered. A sixth order polynomial is used to find the exact roots for the double change point mechanisms. The range of the extreme values is defined for all of the Grashof cases. Characteristic surfaces are developed which prove to be useful for synthesizing linkages with prescribed extreme values of angular velocity ratio.     

Atlas of spherical four-bar mechanisms

An atlas or catalogue of mechanisms provides a useful aid in the synthesis of mechanisms for new applications. The atlas stores mechanisms together with their coupler paths. Fourier techniques can be used as a convenient means for representing, in normalized form, curves for planar mechanisms. This paper looks at the extension to spherical four-bar mechanisms. In particular, a means for projecting a spherical curve onto a plane is discussed which depends only on the geometry of the curve and not on the choice of world coordinate system.     

A complete classification of planar four-bar linkages

A system of classification of planar four-bar mechanisms is presented in which the three major categories are Grashof, non-Grashof and change point. The Grashof and non-Grashof categories are each organized to include four classes while the change point has six classes. The classification system is closely related to a partitioning of the positive octant of a three-dimensional space in which the coordinate axes are nondimensional ratios of the bar lengths. The positive octant is first reduced in size by four zero mobility planes which eliminate from consideration regions where the bar lengths would not permit assembly. The remaining volume is designated as the solution space, and it is partitioned by three change point planes into eight volumes each of which represent a class of Grashof and non-Grashof mechanism. All of the change point classes reside in the change point planes. This paper describes the classification system and the geometry of the solution space, and lays the foundation for future work to study the properties of planar four-bar mechanisms. Because all of the mechanisms within a particular volume share in common characteristics of the bar lengths which are unique to their class, they also share particular properties with regard to the maximum and minimum values of position angles, the range and average value of the position angles, the maximum and minimum value of angular velocity and angular acceleration, as well as time ratio. Hence all of the significant properties can be represented as characteristic surfaces within the solution space. The trace of the characteristic surfaces in the base plane can be used to construct design charts which will permit choosing mechanisms with desirable properties. The method can also be used to synthesize mechanisms by locating intersections of characteristic surfaces. These topics will be presented in forthcoming publications.     

车辆转向平面四杆机构的运动综合

基于实现转向条件，结合四杆机构的环路方程，建立起了车辆转向四杆机构近似运动综合的目标函数。根据极值条件，获得相应的方程组。基于消元法，推导出只含一个变量的多项式方程，以获得机构综合的所有解，从而可选择出最优解。     

Real inflections of hinged planar four-bar coupler curves

Plücker's and Klein's equations provide an upper bound on the number of real inflections on the coupler curve of a hinged planar four-bar mechanism. Generally, for any configuration of the four-bar, the coupler points whose trajectories exhibit inflections lie on a circle. The coupler plane is partitioned by the envelope of the inflection circles into connected regions within which every coupler point has the same number of inflections on its trajectory. This enables us to locate coupler curves exhibiting the maximum possible number of inflections.     

并联机构的奇异点分析

采用微分几何的方法详细分析了并联机构三种类型奇异点、即位形空间奇异点，驱动奇异点和末端执行器奇异点的数学定义、物理意义以及它们之间的相互关系，并采用具体的并联机构实例来解释说明。     

非惯性系下平面连杆机构动态静力分析的键合图

介绍非惯性系下平面连杆机构动态静力分析的键合图法。给出非惯性系平面连杆机构键合图模型的建立方法。基于键合图的基本概念,推导出便于计算机自动生成的机构平衡力矩运动副约束反力的统一公式。将约束反力视为未知热源加在机构键合图相应的０－结处,克服微分因果关系给建立机构平衡力矩及运动副约束反力统一公式所带来的极大的代数困难,通过实例表明本文方法的有效性。     

一种新型平面连杆机构——四偏心机构

为扩大传统平面连杆机构的应用范围、丰富其结构形式,通过完全采用以偏心构件代替连杆,以转动副代替铰接,构成一种新型的四偏心式平面四连杆机构,即带有大转动副的微型平面四连杆机构.为促进此机构向实用阶段转化,给出了两种基本的结构形式,并对其进行了初步的结构分析、运动分析、CAE仿真以及实验验证.给出了各构件的基本尺寸关系和结构优化的方法,求出了从动构件的转角位移运动方程和曲线.通过仿真获得了与理论推导结果相同的从动构件的转角位移运动曲线;同时得出了此机构与传统平面田连杆机构的运动仿真轨迹曲线一致.指出了此机构相对于传统四连杆机构的特点和实施要点.上述分析证明此机构与传统平面田连杆机构的运动规律在本质上具有一致性.     

广义逆矩阵在平面四杆机构综合中的应用

将平面R－R刚体导引的位移约束方程简化为四个变量的超静定拟线性方程组，应用广义逆矩阵以及适当的变量代换，将求解方程归结为一个四次代数方程的求根问题。进而不用初值就能求出最小二乘意义下机构参数全部最优解的近似值，通过适当参数替换，证明该方法能推广至四杆机构实现函数及点位－角移量综合问题中，由此解决了此类机构近似综合问题中的机构参数初值选取问题。     

扫描平面激光坐标测量系统校准方法的优化

介绍了一种基于旋转平面激光单站测角、多站交汇的坐标测量系统,并对其校准方法进行了优化.分析了系统的测角方式和多传感器交汇测量的特点,阐述了基于传统方法的单基站方位信息测量原理及系统结构,并提出了相应的单站结构参数和系统参数校准方法.针对转轴直线和光平面的特点,设计了配套附件并借助经纬仪标定了结构参数,同时通过接收器确定...     

Kinematic analysis of planar higher pair mechanisms

In this paper, theory of kinematics analysis of planar higher pair mechanisms is presented. It has been found that the analysis procedure will be analytical or numerical depending on whether the geometry of the contacting surface(s) is given in an analytical form or in terms of coordinates of discrete points on the surface(s). For either of these options, solution procedures have been described. For the case when profile data is given in numerical form, a numerical scheme of kinematic analysis using cubic spline curve fitting technique has been developed. Two examples are presented: one to illustrate the analytical procedure and the other to illustrate the numerical technique.     

平面四连杆机构位置综合的最小误差算法

针对平面连杆运动位置数多于确定机构的精确点数的运动综合问题,提出运用最小误差为目标函数的参数辩识法算法。通过分析典型的平面四连杆机构的非线性解析方程,根据给定的位置,分解方程,构建线性方程组,引入最小误差目标函数和伪逆的处理方法,得出最优的参数值。通过例证说明该算法的正确性、通用性和有效性。     

平面四连杆机构运动综合线性优化算法

针对平面连杆运动位置数多于确定机构的精确点数的运动综合问题,提出了以最小误差为目标函数的线性优化算法.根据角度的范围有限性,降低了平面连杆机构运动的非线性方程维数,然后根据所得到的结果将平面四连杆机构的非线性方程转换为线性方程组.按照线性方程组的最小误差优化方法可解出最优参数值.例证说明该算法的正确性,线性优化与一般优化算法相比具有快速性和通用性.     

基于并行计算的平面可调七杆机构动力学解析模型研究

基于运动学分析、凯恩动力学方程及数字-符号法,提出采用并行计算建立平面可调七杆机构动力学解析模型的方法,并研究了构件杆长及惯性参数变化对驱动力/力矩的影响.利用封闭矢量法对平面可调七杆机构进行运动学分析,得到各构件的速度和加速度表达式;将独立广义坐标、杆长及惯性参数作为符号量,其余参数处理为数值量,导出动力学解析模型的数字-符号表达式,并构造了解析模型的并行算法.由于动力学模型及实时代码优化是离线建立的,并且采用并行计算结构,减少了在线计算时间,从而为实时控制打下了基础.给出的仿真实例证明了此方法的有效性.     

Kinematic analysis of combined roller-chain and planar mechanisms

This paper presents a suggested mechanical system comprising of two sprocket roller-chains (flexible system) in combination with rigid planar links either crank-coupler or drag-link linkage. The paper discusses and analyzes two alternatives in which the roller-chain is driving the rigid links and “inverse” possibility when the crank of the rigid planar links is the input element and the output motion is taken from the roller-chain. Moreover, replacing the crank of the rigid links by a variable length is discussed, and obtained by considering the coupler as being joined with a point on a drag-link mechanism. The merits of each version are presented and discussed. Of interest, is the unique advantage of obtaining particular output/input velocity ratios which no available mechanism can achieve. Moreover, the obtained results indicate quite a useful applicability of the analyzed system in the industrial packing process, motion transmission and, in particular, in conveying machinery. The kinematic analysis procedure is presented in simple formulation using trigonometric relations.     

平面机构误差分析的同伦法

提出考虑机构原始误差及由弹性变形等造成的平面机构位置误差分析的一种新的方法 ,其基本思路是 :建立平面理想机构与实际机构的位置方程组的同伦方程组 ,用同伦法求出实际机构的位置 ,从而得出平面机构的位置误差。最终得到平面机构误差的变化曲线图