铰链点可互换的近似直线机构综合方法及解域研究

基于拐点圆极点理论,给出了一种可以综合出无穷多铰链四杆近似直线机构的方法。用解析法证明了该方法综合出近似直线机构的一个连架杆的固定铰链点和对应动铰链点可以互换,铰链点互换前后得到的两个机构具有相同的鲍尔点和直线方向,另外一个连架杆不变。推导了综合曲柄摇杆直线机构的公式,并绘制了曲柄摇杆机构解域图。计算示例表明该方法简单有效,能迅速综合出曲柄摇杆直线机构,且综合出的机构动铰链点和固定铰链点可互换。所得到的近似直线机构为实际工程应用提供了更多选择。     

铰链四杆直线机构综合的新方法

给出一种综合连杆曲线具有四个无限接近点（鲍尔点）直线的四杆机构的新方法，用该方法综合铰链四杆机构可事先给定钦逼近直线上的点、直线方向以及机架的位置，而且在每种给定条件下，都可以得到无穷多种机构供设计者选择。     

Solution region synthesis method of planar one-dof six-bar linkages for specifying 4-positions of a 3R open chain

This paper addresses the synthesis problem of one-dof six-bar linkage motion generation for four precision points. A novel and convenient synthesis approach is introduced. With our method, a 3R chain that guides the movement of its end-effector through a set of four specified task positions is given. We then attach two RR links to this 3R chain to obtain a six-bar linkage. Motion generation can produce an infinite number of solutions for four desired positions. It is difficult for designers to synthesize defect-free linkages and synthesize the best linkage through rapidly and precisely selecting curve points that satisfy every design condition. To solve this problem, a solution region method is given in this paper. With this method an infinite number of mechanism solutions can be expressed on a coordinate plane. In addition, the paper still puts forward a distinguishing method for testing circuit and branch defects for Watt-I six-bar linkages. The feasible mechanism solution regions without any defects are obtained by using the solution region method.     

Design of compliant straight-line mechanisms using flexural joints

Straight-line compliant mechanisms are important building blocks to design a linear-motion stage, which is very useful in precision applications. However, only a few configurations of straight-line compliant mechanisms are applicable. To construct more kinds of them, an approach to design large-displacement straight-line flexural mechanisms with rotational flexural joints is proposed, which is based on a viewpoint that the straight-line motion is regarded as a compromise of rigid and compliant parasitic motion of a rotational flexural joint. An analytical design method based on the Taylor series expansion is proposed to quickly obtain an approximate solution. To illustrate and verify the proposed method, two kinds of flexural joints, cross-axis hinge and leaf-type isosceles-trapezoidal flexural（LITF） pivot are used to reconstruct straight-line flexural mechanisms. Their performances are obtained by analytic and FEA method respectively. The comparisons of the results show the accuracy of the approach. Both examples show that the proposed approach can convert a large-deflection flexural joint into approximate straight-line mechanism with a high linearity that is higher than 5 000 within 5 man displacement. This can lead to a new way to design, analyze or optimize straight-line flexure mechanisms.     

四杆直线导向机构综合新方法的研究

提出了四杆直线导向机构综合的数值比较法,运用鲍尔点附近的连杆曲线以３阶精度逼近给定的直线,建立起了连杆曲线中具有直线段的四杆机构数据库。将给定的直线段条件与数据库中的参数进行比较,即可得到一系列满意的四杆直线导向机构。该数值比较法解决了四杆直线导向机构综合的难题。应用该方法编制了一套四杆直线导向机构综合的设计软件,对单、双直线导向机构进行了综合与仿真,实现了导路上无摩擦、磨损的四杆直线导向机构综合的自动化与可视化,大大缩短了设计周期。     

基于拓扑结构分析的求解6-SPS并联机构位置正解的研究

建立机构拓扑结构复杂性和位置正解求解难易性的关系,提出按机构耦合度k大小来分类求解并联机构位置正解全部实数解的数值法,可使正解问题求解容易,具体内容包括：对39种不同构型的6-SPS并联机构,按6种基本机型、33种衍生机型的拓扑结构及其耦合度值分为k=0、1、2、3四类,分析得到了动平台边数、支链类型影响耦合度k值大小的规律。对不同k值的并联机构的位置正解求解指明明确的求解方向,即：对k=0的机构可容易地直接求解其解析正解;对k>0的机构,通过虚设k个SPS型支链,使之转化为k=0的虚拟并联机构,并基于杆长条件建立k个仅含一个变量的杆长相容性方程,再采用k维搜索法求出实数解。以六自由度球面Stewart机构为例,给出了求解耦合度k=1的任意6-DOF SPS并联机构位置正解全部实数解一维搜索法的具体步骤。这种基于拓扑结构分析的6-SPS并联机构位置正解求解的数值法,求解原理简单,计算量小,且具有一般意义。     

On the synthesis of certain straight-line mechanismsSur la synthese des mechanismes reproduisant des droites

A direct method is presented for the synthesis of a large class of approximate straight line mechanisms based on a set of two equations describing the center of curvature of the path (the coupler curve) of an arbitrary point on the coupler of a crank-slider mechanism with an off-set. Several examples are discussed to establish the capability of the proposed set of equations to incorporate the classical approximate straight-line mechanisms (e.g. Watt, Chebyshev and Scott-Russell) as the special cases of the synthesis which can be constructed directly based on graphical considerations. A straightforward design of a luffing-crane mechanism and a graphical construction of a special mechanism which generates two mutually orthogonal straight lines are also presented to further illustrate the general versatility of the proposed method of synthesis.     

一种新型柔性直线导向机构及其运动精度分析

Roberts机构是一种近似直线机构,由于机构中不存在交叉的杆件,使得它适合应用在一体化加工的柔性机构中,从而设计出大行程高精度的柔性直线导向机构。单个Roberts机构可由四个参数完全决定几何特征,其中轨迹点P的位置参数对机构运动直线度的影响最大。文中通过对Roberts柔性机构的伪刚体模型进行分析,说明了对应某一行程,轨迹点P的位置存在最优解使其运动直线度最高,并给出一种直线度等值线图方法确定最优解的大概位置,最后借助有限元方法进行进一步的优化。单个Roberts机构只能提供点的直线运动,可将两个Roberts机构进行并联得到一个柔性导向机构。本文对这种柔性导向机构进行了设计加工、仿真以及试验,结果表明这类柔性导向机构可以在毫米级行程时,垂直运动方向上的偏移小于1um。     

精确直线可展机构及其动力学分析

将Hart直线机构和剪叉机构相结合,提出一种仅含转动副的直线可展单元,并设计得到一种精确直线可展机构。根据机构结构学分析理论,阐述可展机构的模块化组成原理,将机构的组成分解为底部模块、中部模块和顶部模块,3种模块均由直线可展单元构成;对单个直线可展单元进行运动学建模,结合机构的模块化组成原理,推导得到任意模块间的运动学递推关系,求解得到多层模块条件下机构的整体运动学模型,运用Lagrange方程构建机构的整体动力学模型;以3层可展机构为例,对其进行动力学数值计算和虚拟仿真,验证所建运动学和动力学模型的正确性和有效性。通过给定末端执行器的输出运动规律,求解得到机构所需的驱动力矩,结果表明：末端执行器为正弦加速度曲线时,机构在整个工作周期内无冲击,运动稳定性好。     

含R、P副空间5杆单回路的过约束分析

对于常规位置分析为一解的空间单回路 ,本文提出了过约束机构存在条件的一种新方法 ,它能有效地区分位置分析的有限解与无穷解 ,并且给出输入输出方程的解析式 ;阐明了过约束机构存在条件包含过约束条件和封闭条件 ,而封闭条件又需探讨其独立性 ;检验了两个已有的 5杆过约束机构的存在条件 ,并进行了适当修正。这一方法为发现新的过约束机构提供了理论依据。     

计算机辅助机构选型的实现

将机构选型的初始要求划分成运动功能和功能质量两种类型,用规范化方法描述运动功能,用人类自然语言描述功能,在计算机辅助机构造型过程中,由计算机完成精确的推理过程,得到满足运动功能的机构解空间,由设计者根据知识库提供的机构功能质量评价知识,选择满足功率质量要求的机构解,完成模糊的推理过程,由此简化了计算机辅助机构造型的推理机制,实现了机构选型的自动化,解决了机械运动方案CAD中的一大难点,为运动方案CAD的实现奠定了良好的基础。     

Highest-order coupler points of Watt-1 linkages, tracing symmetrical 6-bar curves

Certain non-symmetrical Watt-1 linkage mechanisms may produce symmetrical curves. The dimensions of such mechanisms then have to meet five precise conditions. They have been derived from the two possibilities that symmetrize the Assembly Configuration containing the four 6-bar curve cognates. Each possibility leads to a different mechanism. The one that can be driven without additional conditions, contains a kite 4-bar, carrying rigid triangles that are similar and otherwise related. Then, a ‘kite-cell’ is involved, transforming the input-circle into a symmetrical Watt-1 curve of the 8th or of the 12th degree, depending on the choice of coupler-plane. The second possibility leads to a mechanism in which not only a point, but also a straight-line reaches the image positions. This type, however, must move through a ‘stretched position’ with a two-fold coupler motion. Then, gear-pairs or the like are necessary to overcome such a bifurcated position.     

A unified synthesis method based on solution regions for four finitely separated and mixed “Point-Order” positions

For rigid-body guidance mechanism synthesis reaching four specified task positions, Burmester curve equations are presented by a displacement matrix method. These equations are suitable for both four-finite and four-mixed position cases. With the transformation of coordinates, and based on the projective geometry theory that a series of intersections of two pencils-of-low-order curves constitute a high-order curve, Burmester curves can be expressed by the intersections of a pencil-of-circles and a pencil-of-lines. Then the expressions of Burmester points are parameterized with the angle φ by employing a solution region method. Therefore, Burmester curves can be single-valuedly and orderly expressed, and an infinite number of mechanism solutions can be expressed on a finite coordinate plane.     

基于集合理论的机构自动化选型系统

将机构自动化选型系统分为问题空间和解空间两大部分,建立了基于集合理论的人机结合式机构自动化选型模式。从问题空间到解空间,对运动特性和功能质量采用不同的映射方式,即：由计算机精确推理,选择满足运动功能要求的机构,形成新解空间Ω'J;由人类根据Ω'J中机构的功能质量选择符合功能质量要求的可行机构和最优机构。解决了机构选型要求规范化描述和机构信息规范化表达的难点。根据提出的原理,较好地实现了机构选型的自动化。     

做平面运动滚子从动件盘形凸轮机构的深度广义第Ⅱ类综合问题

提出了“深度广义第Ⅱ类机构综合问题”,拓展了机构综合的“对象空间”和“解集空间”。通过引入偏距e,得到求解的一整套解析公式和解存在性(态)的一系列解析判据。揭示了“脊点对”和“新脊线”的存在性及物理意义,给出了“谷底特征点”的求解方法,提出了“子劣解/子非劣解区域套”等新概念及解析表达式。选取机构图和坐标系为背景,构造面向“超二维第Ⅱ类机构综合问题”的离散曲线族——{C#2}em、{C#1}em、{C**}em以及r0min-e、r0max-e、r0opt-e、[α]**-e,提出了“全局最优解”的存在性和求解方法。通过两个综合实例论证了偏置式机构较正置式机构具有“你无我有、你有我优”的固有潜质和显著优越性。     

弹流润滑点接触问题数值解研究

采用微机对弹性流体动力润滑点接触问题的数值解进行了研究，得出了不同工况下该问题的数值解。经比较所得数值解与公开发表的研究结果一致，且所用方法简明、直观，结果可靠。     

基于Metaball的过渡曲线

利用基于Metaball的约束变形技术，改变原来势函数计算中空间点到约束中心直线距离r的定义，用参数曲线的参数t代替直线距离r，提出了根据被连接曲线构造过渡曲线的新方法。该方法对被连接曲线的种类没有限制，得到的过渡曲线可光滑连接被连接曲线，形状更自然，并且可从被连接曲线的中间点开始过渡。     

Optimal design of a main driving mechanism for servo punch press based on performance atlases

The servomotor drive turret punch press is attracting more attentions and being developed more intensively due to the advantages of high speed,high accuracy,high flexibility,high productivity,low noise,cleaning and energy saving.To effectively improve the performance and lower the cost,it is necessary to develop new mechanisms and establish corresponding optimal design method with uniform performance indices.A new patented main driving mechanism and a new optimal design method are proposed.In the optimal design,the performance indices,i.e.,the local motion/force transmission indices ITI,OTI,good transmission workspace good transmission workspace(GTW) and the global transmission indices GTIs are defined.The non-dimensional normalization method is used to get all feasible solutions in dimensional synthesis.Thereafter,the performance atlases,which can present all possible design solutions,are depicted.As a result,the feasible solution of the mechanism with good motion/force transmission performance is obtained.And the solution can be flexibly adjusted by designer according to the practical design requirements.The proposed mechanism is original,and the presented design method provides a feasible solution to the optimal design of the main driving mechanism for servo punch press.     

瞬心无穷远时近似直线轨迹的四杆机构综合

连杆拐点圆上点附近曲线段与直线之间的近似度很高,工程上常利用其机构作为直线导引机构。针对铰链四杆机构连杆瞬心无穷远时拐点圆不存在,现有的方法不能综合出近似直线轨迹四杆机构的问题,提出瞬心无穷远时连杆曲率叠加原理,根据运动学原理进行分析,推导连杆上任意点曲率计算公式,证明曲率叠加原理的正确性,并得到求解铰链四杆机构连杆两铰链线上零曲率点的图解法。利用图解法能够解决瞬心无穷远时近似直线导引机构的综合问题,从理论上解决了瞬心无穷远时这一特定位置近似直线轨迹导引机构的综合问题。得到的方法简单、直观、适用,是拐点圆理论有力的补充和完善。     

Electromagnetic Location System for Trapped Miners

Electromagnetic signals in very low frequency range (VLF, below 10kHz) can penetrate rock sufficiently in order to locate a miner with nearly no disturbance of the field structure, if the near field condition is fulfilled. The relevant solutions of Maxwell's equations for a magnetic dipole (transmitting antenna to be carried by the miner) in a dissipative medium then are independent of the medium. From these equations the magnetic field strength at any point of reception can be calculated. The key for the location method is the inverse distance function (locus curve), describing the possible location of the dipole from the measured field strength and direction at a point of reception (performed by the rescue team). At least two of these measurements give locus curves intersecting at two points, the correct solution can be found by means of an additional direction information calculated at the points of interest. A system has been built and successfully tested with miner's transmitters which can be activated by a coded signal from the rescue team, a receiver device measuring the field amplitude and field direction and a software package to calculate the miners's location on a notebook directly in the mine.