基于螺旋理论四、五自由度并联机器人构型设计新方法

利用螺旋理论,提出用约束添加法对四、五自由度并联机构进行构型设计,讨论了型综合步骤,其宗旨是让主动链控制所需的自由度,而从动链约束不需要的自由度,最后通过实例进一步阐明这一方法。     

基于单开链单元的三平移一转动并联机器人机构型综合及分类

以单开链支路为单元,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动的并联机器人机构型综合的一种系统,有效的新方法,型综合共得到50个新机构,并对其进行了分类,提出的4d.o.f,并联机器人机构型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。     

两平移-转动并联机构型综合研究

提出一种系统的基于螺旋理论的两平移一转动并联机构型综合的方法。它根据螺旋理论中运动螺旋与约束力螺旋之间的互易关系先构造出可能的分支机构,再组合出不同机型的机构。本文利用该方法进行了两移动一转动并联机构的型综合,给出了部分机型,其中包括一些新机型,同时也得到了一种适合作为减振平台的机型。有效的两平移一转动并联机构型综合的方法对扩大减振平台的优选空间,以及机型的创新设计都有一定积极的意义。     

Synthesis of branched chains with actuation redundancy for eliminating interior singularities of 3T1R parallel mechanisms

Although it is common to eliminate the singularity of parallel mechanism by adding the branched chain with actuation redundancy, there is no theory and method for the configuration synthesis of the branched chain with actuation redundancy in parallel mechanism. Branched chains with actuation redundancy are synthesized for eliminating interior singularity of 3-translational and 1- rotational(3T1R) parallel mechanisms. Guided by the discriminance method of hybrid screw group according to Grassmann line geometry, all the possibilities are listed for the occurrence of interior singularities in 3T1R parallel mechanism. Based on the linear relevance of screw system and the principles of eliminating parallel mechanism singularity with actuation redundancy, different types of branched chains with actuation redundancy are synthesized systematically to indicate the layout and the number of the branched chainsinterior with actuation redundancy. A general method is proposed for the configuration synthesis of the branched chains with actuation redundancy of the redundant parallel mechanism, and it builds a solid foundation for the subsequent performance optimization of the redundant actuation parallel mechanism.     

基于构型演变和李群理论的2T2R型四自由度并联机构型综合

基于构型演变和李群理论提出一类2T2R型四自由度并联机构型综合的系统方法。将6R平面机构某构件两端的R副替换为U副,并添加2条具有六自由度的支链SPS,演变成一个空间并联机构2RRU-2SPS;运用李群理论,综合出等效支链,构造一类2T2R型四自由度并联机构。对一种新型2RPU-2SPS机构,运用单开链法进行自由度的计算和主动副的选取,结果表明所提出的型综合方法正确可行。     

Conditions for parallel realizable configurations in synthesis of constraint-based flexure mechanisms

In synthesis of flexure mechanism, parallel arrangement is paid more attention due to its advantages, such as compact structure and higher stiffness. Researchers have derived many parallel flexure mechanisms, but seldom discuss which kind of flexure mechanism can be realized via fully parallel arrangement. The realizable conditions proposed in current work are complicated to engineering applications. To solve two problems on how to judge whether a flexure mechanism can be realized via fully parallel arrangement and how to realize those flexure mechanisms which cannot be realized via fully parallel arrangement, the algebraic condition is derived to judge whether a freedom space is parallel realizable after introducing the definition of parallel realizable and some propositions, and the condition is there exist 6-n independent line constraints in constraint space reciprocal to dimensional freedom space. Then the realizable constraint spaces reciprocal to freedom spaces with 1-3 dimensions are provided. As a result, not all freedom spaces are parallel realizable. For freedom spaces that are not parallel realizable, the criterion of decomposing DOF is proposed to achieve all motion patterns via parallel or hybrid arrangement, that is a high dimensional freedom space can be realized via combining several low dimensional freedom spaces which are parallel realizable. Specific decomposing strategies for 4 and 5 DOF are provided and a complete flowchart is presented to guide designing flexure mechanisms, particularly those which are not parallel realizable. As case studies, synthesis processes of two helical and 3T1R motions are provided to illustrate the proposed approach. The proposed method provides a feasible approach to realize all motion patterns.     

一类一平移两转动解耦并联机构及其位移分析

基于机构结构组成理论 ,揭示了机构运动解耦特性与机构活动度及其判定准则之间的内在联系 ,提出了拓扑解耦并联机构型综合的基本原理 :综合出一类 3自由度并联机构 ,其期望运动输出为一平移两转动 ,非期望运动输出为常量 :机构运动输入输出呈完全解耦关系 ,位置分析相当简单 ,从而显著简化了该类机构的控制与轨迹规划问题。     

Forward kinematic problem of 5-RPUR parallel mechanisms (3T2R) with identical limb structures

This paper investigates the formulation of the forward kinematic problem of the 5-DOF parallel mechanisms performing three translation and two independent rotations with identical limb structures. The mathematical framework used in this paper is based on algebraic geometry where the forward kinematic problem is explored in a seven-dimensional kinematic space by the means of the so-called Study parameters. In this paper, the algorithms proposed for obtaining the forward kinematic expression is based on two approaches which differ by their concept of eliminating passive variables. The first one is based on the application of the so-called resultant method and the second one, as a novel approach referred to as linear implicitization algorithm, uses an elimination procedure based on solving several systems of linear equations. The forward kinematic problem is solved using the homotopy continuation and it is revealed that it has 1680 finite solutions. Moreover, the forward kinematic problem is studied in three-dimensional Euclidean space where a class of simplified designs are proposed which admit a simpler formulation for the forward kinematic problem. Finally, based on the simplified designs, for a nearly general design a univariate expression of degree 220 is obtained.     

3P-1R四自由度并联机器人机构的自由度分析

简要介绍螺旋理论在并联机构自由度计算与运动特性分析中的应用,探讨反螺旋作为机构约束在并联机构自由度计算公式中所起到的作用,从而得出该公式的修正模型。用这种方法分析一种新型3-5R,1-SPS四自由度并联机器人机构的运动特性,并在ADAMS软件中验证机构的自由度数。     

Biped walking robot based on a 2-UPU+2-UU parallel mechanism

Existing biped robots mainly fall into two categories： robots with left and right feet and robots with upper and lower feet. The load carrying capability of a biped robot is quite limited since the two feet of a walking robot supports the robot alternatively during walking. To improve the load carrying capability, a novel biped walking robot is proposed based on a 2-UPU＋2-UU parallel mechanism. The biped walking robot is composed of two identical platforms（feet） and four limbs, including two UPU（universal-prismatic-universal serial chain） limbs and two UU limbs. To enhance its terrain adaptability like articulated vehicles, the two feet of the biped walking robot are designed as two vehicles in detail. The conditions that the geometric parameters of the feet must satisfy are discussed. The degrees-of-freedom of the mechanism is analyzed by using screw theory. Gait analysis, kinematic analysis and stability analysis of the mechanism are carried out to verify the structural design parameters. The simulation results validate the feasibility of walking on rugged terrain. Experiments with a physical prototype show that the novel biped walking robot can walk stably on smooth terrain. Due to its unique feet design and high stiffness, the biped walking robot may adapt to rugged terrain and is suitable for load-carrying.     

Optimal design of four-bar mechanisms using a hybrid multi-objective GA with adaptive local search

Responding to an increasing demand for mechanism synthesis tools that are both efficient and accurate, this paper presents a novel approach to the multi-objective optimal design of four-bar linkages for path-generation purposes. Three, often conflicting criteria including the mechanism's tracking error, deviation of its transmission angle from 90° and its maximum angular velocity ratio are considered as objectives of the optimization problem. To accelerate the search in the highly multimodal solution space, a hybrid Pareto genetic algorithm with a built-in adaptive local search is employed which extends its exploration to an adaptively adjusted neighborhood of promising points. The efficiency of the proposed algorithm is demonstrated by applying it to a classical design problem for one, two and three objective functions and comparing the results with those reported in the literature. The comparison shows that the proposed algorithm distinctly outperforms other algorithms both quantitatively and qualitatively (from a practical point of view).     

新型两驱动空间并联机构的结构分析

研究空间二自由度4R对称并联机构模型.基于螺旋理论,分析研究了该机构的构型,建立了各支链的运动螺旋系及其约束螺旋.利用经典的Kutzbach-Grübler计算公式得到该机构的自由度数为2,与实际驱动输入一致.研究结果为该类机构的进一步分析提供了理论依据.     

多自由度并联机构输入选取理论的研究及应用

将Klein映射理论应用到多自由度输入选取的判别中,讨论了3力3偶螺旋系的相关性,给出了相关性的判据,使相关性判别变得非常简单,避免了输入选取判别中复杂的数学运算和机构参数未知的问题,从而解决了输入选取的判别难题。利用提出的判别理论研究了一种新型3-RPUR并联机构的输入合理性。     

基于螺旋理论的5R三自由度并联机器人奇异形位分析

并联机器人每个支链由5个转动副组成,通过对支链结构采用坐标变换方法,从而使每个支链等效为一个串联机械手的形式,从而在分析过程中使得原来所要分析的参数由5个减少至4个,降低了分析的难度,这一方法对于今后并联机器人的结构分析方面做出了重要的贡献。为今后的动力学、运动学分析中避免奇异形位做出了理论探索。     

基于螺旋理论的3T1R完全解耦并联机构型综合

利用螺旋理论和独立驱动原则对3T1R类完全解耦并联机构进行型综合。首先根据期望3T1R完全解耦并联机构的运动特征(沿X、Y、Z轴方向的移动和绕Z轴方向的转动)和完全解耦并联机构的正逆雅可比矩阵必为对角阵的要求,利用螺旋理论来构造满足所期望形式的正逆雅可比矩阵;然后根据正逆雅可比矩阵所要满足的条件,确定支链驱动副作用于动平台上的使动螺旋,再得到该使动螺旋对应支链上的表示驱动副的驱动螺旋和除驱动螺旋之外的其他运动螺旋系,根据支链连接度的不同,可以配置支链的所有可能构型;最后根据并联机构运动原理依次取出四条支链连接动平台和定平台得到3T1R完全解耦并联机构。综合的并联机构的输出运动是由支链上独立的输入驱动提供的,且机构的正逆雅可比矩阵在运动过程中始终保持为对角阵,所以属于完全解耦并联机构,此类机构控制简单,具有一定的应用前景。     

完全各向同性3自由度平面并联机构的型综合

提出了完全各向同性3自由度平面并联机构型综合的系统方法。首先,根据螺旋理论讨论了完全各向同性平面并联机构的运动学必要条件。然后,基于机构各分支对动平台控制功能的不同,通过互易螺旋理论推导出各分支的驱动螺旋、主动螺旋和可动非主动螺旋,并按照分支连接度的不同列举出所有可行的分支运动链。最后,按照机构各分支相应的装配条件,选取所综合出的3条分支运动链将动平台和静平台连接起来得到预期的机构,共得到新型机构3167种。由于综合出的并联机器人机构的运动雅可比矩阵均为单位阵,即条件数恒为1,因此这类机构具有良好的运动学和力传递性能,在工业机器人、微操作机器人和医用机器人等领域具有潜在的应用前景。     

2-UPR-SPR并联机构尺度综合

五自由度Exechon机器人被广泛应用于高端制造业,其由具有两转一移三自由度的2-UPR-SPR并联机构和RR串联机构组成(U代表虎克铰,P代表移动副,R代表转动副,S代表球副)。目前对Exechon中并联机构的尺度综合鲜见报道。运用基于螺旋理论的运动/力传递性能指标对Exechon中并联机构2-UPR-SPR进行尺度综合。建立机构运动学反解模型,并对机构进行螺旋分析,得到2-UPR-SPR并联机构的局部传递性能指标和全域性能指标,作为机构运动/力传递性能评价准则。结合空间模型法,获得2-UPR-SPR并联机构的相关指标性能图谱,且根据工程实际需要确定最优区域,在该区域内选取多组数值实例并进行最优筛选。     

螺旋理论在并联机构中的应用

螺旋理论是研究高等空间机构学较为简便的一种数学方法,它是在线性代数的基础上发展起来的。文中介绍了螺旋理论在并联机构自由度分析、反螺旋求解、型综合等方面的应用,并且通过具体数值算例来验证了该方法的可行性、简便性以及优越性。最后可以清晰地总结出螺旋理论是诸种研究并联机构学中最实用的工具。