冗余并联柔索机构姿态工作空间的研究

将冗余并联柔索机构应用于飞行器模型的风洞试验,而工作空间是评价冗余并联柔索机构工作能力的一个重要指标,是并联机构设计的重要基础.分析了该冗余并联柔索机构的姿态工作空间的算法,基于此算法提出了机构的非奇异工作空间和实际姿态工作空间的概念及其相应的算法.通过计算机仿真给出了一个具体的冗余并联柔索机构的非奇异姿态工作空间和实际姿态工作空间的三维可视化描述,为该冗余并联柔索机构的设计和使用提供了一些理论依据.     

冗余并联机构的内力及应用

明确给出了并联机构的内力定义,并对非冗余机构非奇异位置、非冗余机构奇异位置和冗余机构三种情况的内力状况分别进行了说明。对于冗余并联机构的内力问题,给出了内力空间的维数和基底,指出了每种内力状态都是内力空间中的一个元素。以该定义为基础,文章给出了可用内力空间的范围及其判别条件。还分析了采用内力的方法来消除铰链间隙,提高运动精度的措施。以一种冗余Stewart机构为例,考察了内力改变机构刚度的效果,发现内力对这种机构刚性的改变作用很有限。这些结论为冗余并联机构的运动控制以及靠冗余驱动提高机构性能提供参考。     

三自由度冗余驱动并联机构的奇异性和工作空间分析

基于4-SPS/S三自由度冗余驱动并联机构的位置逆解模型,运用微分法推导出了该并联机构的雅可比矩阵,结合Gosselin奇异性分析法和数值分析法,分析了该并联机构的奇异性。随后分析了影响4-SPS/S三自由度冗余驱动并联机构工作空间的主要因素,并对其各支链的行程限制、各球铰副的转角限制和各支链间的尺寸干涉限制等影响因素进行了解析化分析。最后,基于4-SPS/S三自由度冗余驱动并联机构的位置正解模型,设计了该并联机构回转工作空间的求解算法。该算法避免了数值方法及几何方法的复杂性和不确定性,实现了回转工作空间的直观性表达。     

基于球面并联机构的检测平台设计与性能研究

为提高光电产品自动视觉检测的准确性,研制了一种含冗余驱动支链的4SPS/S球面并联调姿平台样机。含冗余驱动支链的4SPS/S并联机构为调姿平台机构本体,具有绕动平台中心点的3个转动自由度,可以实现待检零件任意角度图像信息的获取。建立了该并联机构的运动学模型,导出了机构位置逆解方程和雅可比矩阵;基于雅可比矩阵的秩讨论了机构的奇异性,并验证了冗余驱动支链能消除机构内部奇异;基于雅可比矩阵的非冗余分解,提出了一种评价冗余驱动并联机构力传递性能的指标。分析机构动定平台球铰安装方式对机构运动学性能的影响,得到了机构姿态空间体积大、灵巧度好的动定平台球铰安装方式;设计制作了球面并联检测平台样机,分析并绘制了样机姿态空间以及灵巧度、力传递性能在姿态空间内的分布。结果表明,样机转动空间大,无内部奇异,灵巧度和力传递性能高且分布均匀,能满足光电产品瑕疵检测的工艺要求。     

一种新型闭环支链冗余并联机构

冗余驱动并联机构因具有更好的刚度和良好的力操作性,已越来越多应用于实际生产中。基于3-RPS并联机构,提出一种支链为五杆闭环结构的冗余型并联机构;通过对闭环支链结构和运动的分析,结合数学推导和Matlab,进一步分析了机构整体运动学性能;并根据运动学结果,分别对比引入冗余支链和未引入冗余支链下机构的工作空间情况。结果表明,引入冗余支链会使机构工作空间有所减小,总体减小量达20%左右,但由于机构刚度增加,在满足工作空间条件下,该机构依旧具有明显优势,也为今后冗余驱动并联机构的研究提供了一种新的构型和理论依据。     

新型3-DOF冗余并联机构运动学和工作空间分析

因具备更高刚度、更好动力学性能等特点,冗余驱动并联机构越来越多地应用于各行业中。提出一种支链为双滑块结构的3-DOF冗余并联机构,基于位置正、反解分别推导了机构的运动学方程,并结合反解方程和MATLAB对机构进行运动学仿真,绘制了驱动位移、速度曲线;结合运动学分析结果与正解方程对机构工作空间进行分析,绘制了机构三维工作空间;运动学、工作空间分析结果表明,机构在工作空间内运动平稳,无位移、速度突变等情况,且工作空间关于XOZ面具有良好的对称性;研究结果为该构型冗余并联机构的实际应用提供了基础。     

冗余并联机构的分类研究

在对并联机构的拓扑结构进行分析的基础上 ,提出了一种新的冗余并联机构的分类方法 ,即把冗余并联机构分为位形空间冗余 ,驱动冗余和末端执行器冗余三种类型。这种新的分类方法可以使我们对并联机构冗余的定义有明确的认识 ,并将有助于对冗余并联机构的研究和应用。     

空间2自由度冗余驱动并联机构运动学性能分析

面向建筑机器人领域的高性能机械臂需求,提出了一种空间2旋转自由度的3-UPS&U冗余驱动并联机构。基于螺旋理论和修正的G-K公式对机构的整体自由度进行分析,确定了其围绕恰约束支链万向副旋转的运动特性。建立驱动参数与末端参数之间的映射关系,得到其工作空间模型。通过主驱动并联、从动约束串联的独立建模,构造了该并联机构完整的广义雅可比矩阵,进一步得到动平台末端中心点线速度与驱动关节速度之间的无量纲化雅可比矩阵,并据此建立了特定工作空间下机构的灵巧度、承载能力和刚度性能评价指标。最后结果表明,3-UPS&U冗余驱动并联机构进行较高频次上下摆动作业时,在约束支链所布置的对应转轴方向上,具有更佳的综合运动学性能,且能大大降低性能衰减的幅度。     

一种冗余驱动并联机构的设计与奇异性分析

在Delta机构的基础上提出一种含冗余驱动的三平移并联机构。基于螺旋理论计算了该并联机构的自由度,分析了位置反解,推导出雅可比矩阵,结合Gosselin奇异分析法,对Delta机构的奇异位形进行分析并找出两种新的奇异位形。将Delta机构和冗余驱动并联机构的奇异性进行比较,为了验证理论分析结果,引入可操作度这一运动性能指标,基于数值法对两种机构的奇异性进行比较。理论分析结果表明冗余驱动并联机构可以实现和Delta机构相同的功能,但其第二类奇异位形明显比Delta机构少;数值分析结果表明选取合适的工作空间和机构参数可减少并联机构的奇异位形,同时也验证了理论分析结果的正确性。     

一种新型冗余驱动并联二维指向机构的研究

以球面5R机构为原型,通过添加冗余驱动支链的方法,得到了一种新型高精度、高承载和大工作空间的冗余驱动并联二维指向机构。以消除机构内部奇异、增大机构工作空间为目标,针对具有特定驱动螺旋的冗余驱动支链进行综合;通过对比各分支,筛选出了一种结构简单、精度高、承载能力强的分支,构成了新型冗余驱动并联二维指向机构,并对该机构的位置反解、雅可比矩阵及其奇异性进行了分析;针对机构工作空间、灵巧性和承载力等性能,绘制了机构的性能图谱;基于机构性能的均值指标和方差指标对机构进行了尺寸参数的优化设计,得到了一种性能优异的冗余驱动并联二维指向机构并制作了样机,为跟踪指向领域提供了一种高品质的机构。     

Force and torque analysis of constrained space mechanisms and plane mechanisms with offset links by matrix displacement-direct element method

Many constrained spatial mechanisms and plane mechanisms with offsets between the planes of motion of the links become statically indeterminate mechanisms, and their force and torque analyses require elastic analyses. The matrix displacement-direct element method, a finite element method with line elements, of force and torque analysis of statically indeterminate, as well as statically determinate, spatial and planar mechanisms is presented. All the links in a mechanisms may be elastic and they may experience flexural, torsional and axial deformations. The cross-sectional properties of a link may vary. The 4R plane mechanisms with and without offsets and the RCSSRC spatial screw generator are analyzed as examples, and force and torque distributions and the deformed geometries of these mechanisms are determined.     

对称结构Stewart 并联机器人的位置正解及构型分析

对具有对称结构的6－6SPSStewart并联机器人的位置正解问题进行了研究，以活动平台的铰链坐标为未知量，按定杆长约束条件建立了对称并联机器人位置正解的数学模型；以结构参数和杆长为量作为修正变量，构造了一种新的系数同伦方程，运用该方法可以快速得到同类并联机器人的全部28组位置正确。这种方法可以方便地求出不同结构参数和杆长变量同类机构的位置正解，其数学模型简单，并且不依赖初值。基于位置正解对Stewart并联机器人存在的装配构型进行了分析，给出了数值计算实例。     

A 3-DOF Pseudo-Rigid-Body Model for Tension-Based Compliant Bistable Mechanisms

Compliant bistable mechanisms, devices with two distinct stable equilibrium positions, are used in a variety of applications, such as switches, clasps, and valves. Many kinds of compliant bistable mechanisms were proposed and studied during the past decade. Among them, tension-based compliant bistable mechanisms, that incorporate tension pivots as their flexible members, feature in short travel distance and low power consuming. So far, the design of this kind of bistable mechanisms is done using finite element method through trial and error, thus is time-consuming. By treating the tension pivots as fixed-guided segments and their elongation as a spring, we developed a novel three degree-of-freedom (3-DOF) pseudo-rigid-body model (PRBM) for this kind of bistable mechanisms. The principle of virtual work is used to derive the force-deflection relationship of the PRBM model. The comparison between the PRBM results and the experimental results of the force-deflection characteristics shows that the PRBM can predict not only the bistable behavior of the tension-based bistable mechanisms, but also their soft spring-like post-bistable behavior and the spring-like force-deflection characteristics when pulling in the reverse direction from the as-fabricated position, which is called reverse behavior. The 3-DOF PRBM can be used to design and identify tension-based bistable mechanisms. Using the PRBM instead of the trial-and-error method can greatly reduce the development time of this kind of bistable mechanisms.     

作平面运动滚子从动件形锁合凸轮机构的第Ⅱ类机构综合问题

形锁合凸轮机构在工程应用中具有广泛性和重要性,在综合的理论方法方面具有复杂性和特殊性。基于"浮动数轴"、"瞬时、整程区间套"等概念并通过引入"往程"、"返程"和"向径标刻线"等新概念,深入系统地讨论共轭、槽道和等径凸轮等形锁合凸轮机构的第Ⅱ类机构综合问题。研究结果表明:形锁合机构的综合,并非力锁合机构综合的简单组合、叠加,而是蕴含着诸多复杂深刻、特殊独到的异质性研究内涵。以最具典型性、代表性的等径凸轮机构为例,其在往、返程运动角和远、近休止角的内在规律性关系,运动学尺寸、行程与初始位置参数的内在特征关系,输出件返程角位移规律的求解,滚子中心容许选择区段、凸轮理论基圆半径许用取值范围确定等方面,都具有较力锁合凸轮机构来得复杂深刻、特殊独到的研究思想、方法和结论。给出等径凸轮机构的一个综合算例。     

Spring-joint method for topology optimization of planar passive compliant mechanisms

There is seldom approach developed for the initial topology design of flexure-based compliant mechanisms. The most commonly-used approaches, which start with an existing rigid-body mechanism, do not consider the performances between different topologies. Moreover, they rely heavily on the rigid-body topology, therefore limit the diversity of compliant mechanisms topology. To obtain the optimal initial topology of such mechanisms directly from problem specifications without referencing to the existing mechanism topologies, a spring-joint method is presented for a restricted class of the serial passive flexure-based compliant mechanisms, which are the building blocks of parallel compliant mechanisms. The topology of the compliant mechanisms is represented by a serial spring-joint mechanism（SSJM） that is a traditional rigid-body mechanism with a torsional spring acting on each joint, and is described by position vectors of the spring-joints. A simplified compliance matrix, determined by the position vectors, is used to characterize the tip of the SSJM kinematically, and is optimized to ensure the desired freedoms of the compliant mechanisms during optimization. The topology optimization problem is formulated as finding out the optimal position of the spring-joints in a blank design domain with an objective function derived from the simplified compliance matrix. In design examples, syntheses of the compliant mechanisms with both single freedom and two decoupled freedoms are presented to illustrate the proposed method. The proposed method provides a new way for the initial design of flexure-based compliant mechanisms.     

RGRR-Ι构造混联6R机器人

新型并联双自由度转动关节(RGRR-Ⅰ)活动构件少、工作空间大,利用RGRR-Ⅰ构造混联6R机器人可以实现高刚度、大工作空间、机构紧凑等。提出混联机构的求解新方法,即建立少自由度并联机构的运动坐标参数与机构运动输入参数之间的关系,把混联机构的求解转化为各少自由度并联机构的求解和运动坐标参数之间的串联求解,降低了求解难度,可以方便地推导出位置的正解和反解。此方法对其他混联机器人的运动学分析有借鉴作用。     

点啮合高副机构误差与变异关系的运动几何模型

在点啮合分度凸轮机构原理、蜗轮蜗杆传动原理与技术的基础上,详细讨论了点啮合高副机构的误差条件下的传动问题,误差和变异的基本概念与表现形式等;建立了点啮合高副机构误差与变异关系的基本方程,揭示了误差与变异间的内在规律性。这对指导设计和制造,提供了良好的技术准备与理论依据。     

Stiffness modeling of a family of 6-DoF parallel mechanisms with three limbs based on screw theory

The stiffness modeling of a family of six degrees of freedom (DoF) parallel mechanisms with configurations of 3-RUPU is presented. The mobility of the mechanisms is firstly analyzed, and then the stiffness analysis and modeling of the family of mechanisms is developed by a novel screw-theory based method. The method employs screw theory as a tool for force analysis and deformation analysis. Based on the developed stiffness model, two global flexibility indices, which refer to the maximum and minimum singular values of compliance matrix, are introduced to evaluate the compliance of parallel mechanisms. Finally, a case study is presented to demonstrate the effectiveness of the method in analyzing and evaluating the stiffness behavior of the presented parallel mechanisms.     

区间参数柔性机构设计的混合元胞自动机方法

进行柔性机构设计时,应考虑不确定性参数对机构性能的影响。基于此,将柔性机构物理参数及其外载荷视为区间变量,基于柔性机构的刚性测度和柔性测度,建立在连续域中利用结构拓扑优化设计柔性机构的数学模型。采用固体各向同性惩罚方法进行设计域材料的参数化,将材料相对密度作为设计变量,结构受载时的应变能和交互势能线性加权的极大化作为目标函数,结构体积作为约束。优化设计求解策略采用混合元胞自动机方法,用区间有限元法进行结构总体分析以获取优化过程中的每次迭代信息,设计变量中的局部改变由基于比例—积分—微分控制律的局部设计规则来确定。数值算例证明了所建模型及其解法的有效性。按照数值算例结果之一进行等比例尺寸放大后的实物制造,并进行简单试验验证。     

Design principle of high-precision flexure mechanisms based on parasitic-motion compensation

In design of flexure mechanism, diminishing the parasitic-motion is a key point to improve the accuracy. However, most of existing topics concentrate on improving the accuracy of linear-motion flexure mechanisms via compensating the parasitic error, but few research the multi-dimensional flexure mechanisms. A general design principle and method for high-precision flexure mechanisms based on the parasitic-motion compensation is presented, and the proposed method can compensate the parasitic rotation in company with translation, or the parasitic translation in company with rotation, or both. The crucial step for the method is that the parasitic motion of a flexure mechanism is formulated and evaluated in terms of its compliance. The overall compliance matrix of a general flexure mechanism is formulated by using screw theory firstly, then the criteria for the parasitic motions is introduced by analyzing the characteristics of the resultant compliance matrix as well as with aid of the concept of instantaneous rotation center. Subsequently, a compliance-based compensation approach for reducing parasitic-motion is addressed as the most important part. The design principles and procedure are further discussed to help with improving the accuracy of flexure mechanisms, and case studies are provided to illustrate this method. Finally, an analytical verification is provided to demonstrate that the symmetry design philosophy widely used in flexure design can effectively improve accuracy in terms of the proposed method. The proposed compensation method can be well used to diminish the parasitic-motion of multi-dimensional flexure mechanisms.