基于螺旋理论的两转一移解耦并联机构型综合

强耦合性是并联机构的一个显著特点,如果能使并联机构的运动部分解耦或者完全解耦,将使并联机构的理论分析、实际应用等方面变得容易。为此,本文基于螺旋理论、机构运动螺旋系与分支运动螺旋系之间的关系,提出了移动解耦分支型综合准则和转动解耦分支型综合准则,确定了并联机构转动条件及输入运动副选择原则,形成了两转一移解耦并联机构型综合方法,并以此对两转一移解耦并联机构进行了综合并得到了许多新型机构,从而验证了该方法的正确性和可行性。     

约束综合法及新型4、5自由度对称并联机构

少自由度并联机器人的研究和应用近年来吸引了各国研究者的广泛注意。本文简要介绍了我们提出的基于螺旋理论的少自由度并联机构的约束综合法，并列举了以约束综合法得到的新型4和5自由度对称并联机构。     

Type Synthesis of Fully-Decoupled 3R2T Parallel Mechanisms Based on Driven-Chain Principle

To avoid the existence of nonlinear and strong coupling in parallel mechanisms,it is necessary to address special care to the type synthesis of mechanisms,especially for the type synthesis of fully-decoupled parallel mechanisms. Based on the screw theory and the driven-chain principle,a methodology of structural synthesis for fully-decoupled three-rotational( 3R) and two-translational( 2T)parallel mechanisms was proposed by analyzing the characteristics of the input-output relations for fully-decoupled parallel mechanisms.Firstly,according to the desired kinematic characteristics of fullydecoupled parallel mechanisms,a method was presented by virtue of screw theory to synthesize the desired forms for both the direct and the inverse Jacobian matrices. Secondly,according to the feature of the direct and the inverse Jacobian matrices,the effective screws,the actuated screws and the mobile un-actuated screws of each leg were established based on the reciprocal screw theory and all possible topology structures fulfilling the requirements were obtained.Finally,the desired fully-decoupled parallel mechanisms could be synthesized by using the structural synthesis rule and structural synthesis of fully-decoupled 3R2 T parallel mechanisms could be obtained exploiting the abovementioned methodology. Furthermore,the Jacobian matrix of a synthesized 3R2 T parallel mechanism was deduced to demonstrate the decoupling feature of the parallel mechanism,which also validated the correctness of the methodology of the type synthesis for fully-decoupled 3R2 T parallel mechanisms.     

一种新型两自由度高速并联机械手的尺度综合

对含被动支链的两自由度平动并联机构的概念设计进行了研究,归纳了被动支链的几种可能构型.运用螺旋理论对被动支链进行自由度分析,进而提出了一种新型高速并联机械手机构,该机械手包含两条主动支链和两条被动支链,其中被动支链用来对动平台的姿态进行约束,并提高机械手的刚度.在进行运动学分析的基础上,以机械手雅克比矩阵条件数在工作空间上的平均值和最大值的加权值为性能指标,对该并联机械手机构进行了尺度综合.研究表明,该两自由度平动并联机械手可与一单自由度进给机构组合,构成一个三自由度平动混联机械手,适用于工业领域的高速拾放操作.     

Numeration and type synthesis of 3-DOF orthogonal translational parallel manipulators

Low-degree-of-freedom （Low-DOF） parallel manipulators （PMs） have drawn extensive interests, particularly in type synthesis in which two main formal approaches were established by using the reciprocal screw system theory and Lie group theory. This paper aims at numeration and type synthesis of orthogonal translational parallel manipulators （OTPMs） by resorting to an integration of the group- based method and graphical representation of the topology. For this purpose, the concept of Cartesian DOF-characteristic matrix, orig- inated from displacement subgroup and displacement submanifold, is proposed. A new approach based on the combination of the atlas of Cartesian DOF-characteristic matrix and the displacement group-theoretic method is addressed for both exhaustive classification and type synthesis of OTPMs. The proposed approach is prone to construct an orthogonal structure and is easy to realize the complete classification and exhaustive enumeration of this class of low-DOF PMs.     

完全各向同性解耦3T1R型并联机器人构型综合

为综合得到完全各向同性解耦并联机器人构型,基于GF集理论提出了一种简单而有效的构型综合方法.阐述GF集的基本概念、运算法则,转动特征存在条件;给出机构输入运动副选择原则和分支设计准则,确保了并联机构运动各向同性及解耦性;根据该构型综合原理,实现了3T1R的4自由度完全各向同性解耦并联机构型综合,得到了大量新构型;针对所综合的一种新型并联机构,运用螺旋理论求解其机构的自由度并推导其雅克比矩阵,验证了该机构的完全各向同性,也进一步证明了该构型综合方法的有效性.     

一种可重构空间四杆机构

提出一种可重构空间四杆机构,其具有两种不同的工作模式,模式Ⅰ为一个转动运动,模式Ⅱ为一个平移平动,两种运动模式进行切换的初始位形具有瞬时的一个转动和一个平动.将可重构空间四杆机构与一个具有两移动和两转动的串联支链相连,构成一种具有两种不同工作模式的可重构混联支链.利用3条可重构混联支链连接并联机构的固定平台和运动平台,可得到一种新型可重构并联机构,通过控制3条可重构混联支链分别在两种不同工作模式间切换,可重构并联机构可实现4种不同的三自由度运动模式.利用螺旋理论分析和证明了上述结论.     

Structural Synthesis of 3T2R Five-Degree-of-Freedom Hybrid Mechanism

The structural synthesis of mechanisms is a prerequisite of mechanical design,thereby,it is necessary to pay attention to the structural synthesis of mechanisms,especially for the type synthesis of hybrid mechanisms.A very simple yet very effective method was presented for the structural synthesis of hybrid mechanisms based on the set theory.The basic concept and mathematical operation of G_F set were firstly introduced.Based on the G_F set,a type synthesis principle for serial mechanisms,parallel mechanisms and hybrid mechanisms was presented,especially,a detailed algorithm of type synthesis for hybrid mechanisms was proposed as well.It is shown that type synthesis of hybrid mechanisms can be developed by the combination of elements of G_F set and rotation axis transfer theorem.Further investigation shows that structures of 3T2R fivedegree-of-fteedom(DoF) hybrid mechanism only have one category,i.e.,G_F~I.Finally structural synthesis of 3T2R hybrid mechanism for this category is illustrated with example to demonstrate the applicability of the type synthesis principle.     

空间机构运动分析的正交螺旋法

本文用正交螺旋法对一个自由度单环空间机构的运动进行了分析,导出其速度、加速度的度算公式,并对输入构件为连杆和不同运动副的组合进行了讨论,最后以具有三平行轴的七杆空间机构为例作了数字计算。     

基于一种半开式滑槽球副的3-PSP并联平台设计

提出在并联机构中应用一种1移动3转动半开式滑槽球副结构,该运动副将1个移动副和1个球副集成为一个复合的运动副,可以缩短并联机构中支链的尺寸链,有助于提高并联机构精度.基于半开式滑槽球副设计了一种3自由度(3-DOF)PSP三轴并联平台,通过对此机构进行的运动分析和支链的精度分析,导出各个支链的逆解方程,同时根据影响支链运动精度的各个因素给出支链系统误差的线性补偿方程,证明此并联机构具有易于控制、运动精度高的优势.     

并联机构4-RPR(RR)的基础分析

讨论了一种新型少自由度并联机构4-RPR(RR),描述了机构的特性并利用螺旋理论分析了它的运动,计算了自由度,给出了机构的位置反解,利用虚设机构法建立了一阶影响系数矩阵并对机构进行了速度分析及仿真。这些是对该机构进一步分析的基础,包括其运动学、动力学分析,因此是具有实际价值的。     

空间少自由度并联机构瞬时螺旋运动轴线曲面的几何表示方法

对于单自由度的平面机构或单自由度空间机构来说,机构中各个点的运动都是确定的。机构在运动过程中的一系列瞬时螺旋运动轴线所形成的曲面也是唯一的,比较容易求解,可以得到其数学表达式。但对于多自由度的空间机构来说,由于在每一个位形下,机构的运动有多种可能性,瞬时运动轴线所形成的曲面也不是唯一的,很难得到其数学表达式。本文通过求解空间机构在运动过程中的一系列瞬时运动轴线,利用几何方法绘制出空间少自由度并联机构的瞬轴曲面,从而可以更直观地了解少自由度并联机构的空间运动。     

Kinematic Characteristics Analysis of 3-PRS Parallel Manipulator

The 3 - PRS parallel mechanisms, whose kinematic chain is connected by prismatic joint P, revolute joint R and spherical joint S, have two rotational and one translational DOF. But the DOF of 3 - PRS parallel mechanism cannot be explained by the Grubler-Kutzbach method or Herve method. To illuminate the special kinematic characteristics of 3 - PRS parallel mechanism, a novel analytical approach is proposed in this paper. All the feasible instantaneous motions of 3 - PRS mechanism are studied by using this method. The analysis of kinematic characteristics of 3 - PRS mechanism help to understand the mechanism and estimate the motion capacity of mechanism. Finally, it is also helpful to optimize the topology of the mechanism and the trajectory for desired performance.     

基于单开链单元的三平移一转动并联机器人机构型综合

以单开链支路的单元,揭示了欠秩并联机器人机构结构组成的某些规律,提出了输出运动为三平移及一定向转移并联机器人机构综合的一种系统,有效的新方法,型综合共得到50个新机构,并进行了分类,提出了4d.o.f并联机器人机械综合方法具有普遍性意义,并已用于其它运动输出类型的欠秩并联机器人机构的型综合。     

3-PRRU并联机器人位置反解和奇异位形的研究

针对一种新型机构3自由度3-PRRU并联机器人,应用Denavit-Hartenberg(D-H)方法建立了该机构的运动学方程,得出理论上具有64组位置反解的结论,采用matlab软件对反解进行了数值仿真.最后用雅可比矩阵行列式获得奇异位形条件方程,对此并联机构的奇异问题进行了分析.     

基于螺旋理论的3-RRR并联机构设计与仿真

基于螺旋理论分析了一种3-RRR并联机构的自由度和构型.通过分析动平台和各分支机构的约束螺旋系,构造3-RRR串联分支,运用修正Crübler-Kutabath公式计算出其自由度满足3个转动自由度.基于虚拟样机技术建立3-RRR并联机构虚拟仿真模型,进行正向运动学仿真和工作空间分析,从而找到该机构存在的缺陷,为少自由度并联机构运动学和动力学分析提供保证.     

Numeration and type synthesis of 3-DOF orthogonal translational parallel manipulators

Low-degree-of-freedom (Low-DOF) parallel manipulators (PMs) have drawn extensive interests, particularly in type synthesis in which two main formal approaches were established by using the reciprocal screw system theory and Lie group theory. This paper aims at numeration and type synthesis of Orthogonal Translational Parallel Manipulators (OTPMs) by resorting to an integration of the group-based method and graphical representation of the topology. For this purpose, the concept of Cartesian DOF-characteristic matrix, originated from displacement subgroup and displacement submanifold, is proposed. A new approach based on combination of the atlas of Cartesian DOF-characteristic matrix and displacement group-theoretic method is addressed for both exhaustive classification and type synthesis of OTPMs. The proposed approach is prone to construct an orthogonal structure and is easy to realize the complete classification and exhaustive enumeration of this class of low-DOF PMs.     

机器人及空间机构的螺旋运动分析

任一刚体的空间运动都可以视为沿某一轴线作螺旋运动。基于这一观点,本文用螺旋理论对机器人的相对运动作了分析。文中提出的螺旋运动方程对闭式运动链,即空间机构同样适用。     

基于李群理论的2R1T并联机构构型综合

应用李群理论,对2R1T(两转动—移动)并联机构的型综合问题进行了系统地研究. 通过分析满足2R1T自由度性质的动平台的李群代数结构,并依据李群代数结构与刚体运动的对应关系,确定出各支链的李群代数结构和它们的等效运动链,最终综合出4394种2R1T并联机构新构型,并绘制了支链机构简图和部分机构简图. 研究结果表明,该方法简单、规范、有效,可作为构型评价及优化的基础,也适用于其他类型并联机构的型综合研究.      

叶梢带端板螺旋桨的性能研究

1 概述 若使螺旋桨叶片的梢部保持一定的弦长,并装有一小块弧形端板,则能阻止叶端的横向绕流,维持较大的环流强度,从而增加叶片推力。此外还能消除梢涡,降低噪声。80年代初,叶梢带端板的螺旋桨用于实船试航,获得以14％～15％的节能效益,从而引起人们的关注,并对这种推进器开展了广泛的研究和讨论。 作者1985年以来也对叶梢带端板螺旋桨进行了研究。以一艘单桨船舶的常规螺旋桨模型为对比基础,保持其叶面积不变,使桨叶修改成具有宽叶梢的外形。同时先后安装五种方案的叶梢端板,进行了理论计算和模型敞水试验。桨模的叶数为4;直径144.4mm;