并联机器的起源和发展

目前，并联机器的发展已经从最初的实验原型样机走向实用化和商品化阶段。本文首先回顾了并联机器的起源，并阐述了其主要特点；然后探讨了并联机器的研究现状和存在的主要问题；最后介绍了清华大学在并联机器实用化研究中的主要进展。     

新型6-PSS并联机器人的位姿误差分析

在获得6-PSS并联机构位置反解的基础上,考虑杆长、铰链位置、铰链间隙等各类主要误差源对终端误差的影响,推导出此新型机构的位姿误差模型,且应用蒙特卡洛技术分析了位姿误差的分布规律,为这种机器人的理论设计与精度补偿提供了理论基础。     

Compliance modeling and analysis of a 3-RPS parallel kinematic machine module

The compliance modeling and rigidity performance evaluation for the lower mobility parallel manipulators are still to be remained as two overwhelming challenges in the stage of conceptual design due to their geometric complexities. By using the screw theory, this paper explores the compliance modeling and eigencompliance evaluation of a newly patented 1T2R spindle head whose topological architecture is a 3-RPS parallel mechanism. The kinematic definitions and inverse position analysis are briefly addressed in the first place to provide necessary information for compliance modeling. By considering the 3-RPS parallel kinematic machine（PKM） as a typical compliant parallel device, whose three limb assemblages have bending, extending and torsional deflections, an analytical compliance model for the spindle head is established with screw theory and the analytical stiffness matrix of the platform is formulated. Based on the eigenscrew decomposition, the eigencompliance and corresponding eigenscrews are analyzed and the platform＇s compliance properties are physically interpreted as the suspension of six screw springs. The distributions of stiffness constants of the six screw springs throughout the workspace are predicted in a quick manner with a piece-by-piece calculation algorithm. The numerical simulation reveals a strong dependency of platform＇s compliance on its configuration in that they are axially symmetric due to structural features. At the last stage, the effects of some design variables such as structural, configurational and dimensional parameters on system rigidity characteristics are investigated with the purpose of providing useful information for the structural design and performance improvement of the PKM. Compared with previous efforts in compliance analysis of PKMs, the present methodology is more intuitive and universal thus can be easily applied to evaluate the overall rigidity performance of other PKMs with high efficiency.     

Influence of kinematic redundancy on the singularity-free workspace of parallel kinematic machines

In this paper the effect of kinematic redundancy in order to reduce the singularity loci of the direct kinematics and to increase the operational, i.e., singularity-free, workspace is demonstrated. The proposed approach consists of additional prismatic actuators allowing one or more base joints to move linearly. As a result, a selective reconfiguration can be performed in order to avoid singular configurations. Exemplarily, kinematically redundant schemes of four structures, the 3RRR, the 3RPR, the 6UPS, and the 6RUS, are considered. The relationship between the redundancy and the operational workspace is studied and several analysis examples demonstrate the effectiveness of the proposed concept. Furthermore, the additional benefit of an increasing number of redundant actuators is discussed.     

新型两平移一转动并联机器人机构位置分析

分析了一种新型两平移一转动并联机器人机构．求出其运动学正解和反解封闭解．讨论了该机构的控制解耦性。与其它类似机构相比。该机构不仅结构简单、位置分析求解容易,而且正解具有完全控制解耦关系。该机构可广泛应用于工业装配机器人、微动机器人、虚拟轴并联机床、多维减振平台和推拿机器人等领域。     

Geometric approach for kinematic analysis of a class of 2-DOF rotational parallel manipulators

Euler angles are commonly used as the orientation representation of most two degrees of freedom (2-DOF) rotational parallel mechanisms (RPMs),as a result,the coupling of two angle parameters leads to c...     

Optimal design of a 3-leg 6-DOF parallel manipulator for a specific workspace

Researchers seldom study optimum design of a six-degree-of-freedom(DOF) parallel manipulator with three legs based upon the given workspace. An optimal design method of a novel three-leg six-DOF parallel manipulator(TLPM) is presented. The mechanical structure of this robot is introduced, with this structure the kinematic constrain equations is decoupled. Analytical solutions of the forward kinematics are worked out, one configuration of this robot, including position and orientation of the end-effector are graphically displayed. Then, on the basis of several extreme positions of the kinematic performances, the task workspace is given. An algorithm of optimal designing is introduced to find the smallest dimensional parameters of the proposed robot. Examples illustrate the design results, and a design stability index is introduced, which ensures that the robot remains a safe distance from the boundary of sits actual workspace. Finally, one prototype of the robot is developed based on this method. This method can easily find appropriate kinematic parameters that can size a robot having the smallest workspace enclosing a predefined task workspace. It improves the design efficiency, ensures that the robot has a small mechanical size possesses a large given workspace volume, and meets the lightweight design requirements.     

Precision analysis of a weakly-coupled parallel mechanism with three translational degrees of freedom

This paper analyzes the precision of the dissymmetrical parallel mechanism of 3-RRRP(4R) with three translational degrees of freedom (DOF). The parallel mechanism has weakly-coupled, decoupled and real-time characteristics, thus error compensation can be done using control software. Based on topology structure analysis, the inverse and forward solutions are analyzed and the precision is studied using complete differential method. The influencing factors of the manipulator’s precision are studied carefully and the means to enhance the precision are also discussed. It is found that the position errors of the moving platform have nonlinear relation with the position of the mechanism. The δθ’₃ error has the biggest influence on the nonlinear errors of the position. Otherwise, the original errors of the mechanism are the main reason leading to more errors. Thus enhancing machining and assembling precision is an important method to enhance the precision of the mechanism. __________ Translated from Journal of Jiangsu University (Natural Science Edition), 2005, 26(3) (in Chinese)     

欠秩3-UPU并联角台机构工作空间分析

针对欠秩3—UPU并联角台机构的结构特点,首先找出了该机构的几何约束,在此基础上建立了该机构移动副两端虎克铰平行或垂直布置时的位置反解方程。然后利用该机构的几何约束条件,进一步建立了该机构在两种情况下的工作空间的求解方程,为该机构的应用奠定了一定的基础。     

斜拉桥缆索检测机器人结构设计与运动仿真

以实现斜拉桥缆索高效检测为目的,提出了一种新型缆索检测机器人结构设计。在对检测机器人的附着条件进行分析的基础上,利用三维设计软件Pro/E对机器人进行运动仿真分析,为提高缆索检测机器人的爬升能力以及机器人总体结构的优化设计提供了一定的参考依据。     

Error Modeling and Sensitivity Analysis of a Parallel Robot with SCARA（Selective Compliance Assembly Robot Arm） Motions

Parallel robots with SCARA（selective compliance assembly robot arm） motions are utilized widely in the field of high speed pick-and-place manipulation. Error modeling for these robots generally simplifies the parallelogram structures included by the robots as a link. As the established error model fails to reflect the error feature of the parallelogram structures, the effect of accuracy design and kinematic calibration based on the error model come to be undermined. An error modeling methodology is proposed to establish an error model of parallel robots with parallelogram structures. The error model can embody the geometric errors of all joints, including the joints of parallelogram structures. Thus it can contain more exhaustively the factors that reduce the accuracy of the robot. Based on the error model and some sensitivity indices defined in the sense of statistics, sensitivity analysis is carried out. Accordingly, some atlases are depicted to express each geometric error’s influence on the moving platform’s pose errors. From these atlases, the geometric errors that have greater impact on the accuracy of the moving platform are identified, and some sensitive areas where the pose errors of the moving platform are extremely sensitive to the geometric errors are also figured out. By taking into account the error factors which are generally neglected in all existing modeling methods, the proposed modeling method can thoroughly disclose the process of error transmission and enhance the efficacy of accuracy design and calibration.     

新型并联机器人坐标测量机仿真建模的实现

为了验证新型5自由度并联机器人坐标测量机的设计方案和理论模型,缩短开发周期,降低开发费用,提高一次性设计成功率,将虚拟样机技术应用于该并联机器人坐标测量机的设计开发过程。利用SolidWorks软件建立该型并联坐标测量机的虚拟样机模型,应用OLE接口技术实现了该型并联坐标测量机的运动仿真和测量仿真,采用ADAMS软件实现了该型并联坐标测量机的动力学分析和仿真,并给出了仿真建模过程中关键问题的解决方案。计算机仿真结果证实了理论模型的正确性,验证了设计的合理性和可靠性。为此新型并联机器人坐标测量机的结构设计和数控系统设计提供了主要参数和理论依据,为并联坐标测量机的工程设计提供了一套有效的分析方法。     

新型6自由度并联机器人误差补偿

分析了新型6自由度并联机器人的位置误差和姿态误差。在误差概率分析与蒙特卡洛法的基础上,建立铰链间隙影响下的机器人实际误差模型。并在直接误差补偿法和工作空间补偿的基础上,结合并联机器人平台模型及误差模型提出一种适合该模型的误差补偿方法。该方法具有一定的普遍性。     

BKX-I型并联运动机床的实验模态分析及灵敏度分析

在对BKX-I型并联运动机床进行实验模态分析的基础上,获得了机床在典型位姿下的低阶固有频率、振型、阻尼比,同时通过对机床系统进行灵敏度分析确定其薄弱环节,并提出提高并联运动机床动态特性的具体措施,为并联运动机床结构的动态设计和优化设计提供了有效的方法。     

超声检测并联机器人位姿分析研究

针对多自由度超声检测机器人检测曲面工件时位姿调整困难问题,通过分析超声检测并联机器人的运动学模型,提出了超声背散射检测与并联机器人一体化技术。以实现超声检测探头姿态的特殊控制要求为目标,对检测并联机器人建立了数学模型,提出了一种位姿控制计算方法,并利用Matlab对位姿控制进行了仿真分析,为计算机控制检测探头进行曲面检测提供准确的控制参数。通过超声C扫查实验,对比了超声图像中噪声所占的面积比例和图像轮廓清晰度。实验结果表明,超声检测并联机器人在提高超声探头的位姿控制精度后,能够降低噪声,提高信噪比。     

Evaluation of the power consumption of a high-speed parallel robot

An inverse dynamic model of a high-speed parallel robot is established based on the virtual work principle. With this dynamic model, a new evaluation method is proposed to measure the power consumption of the robot during pick-and-place tasks. The power vector is extended in this method and used to represent the collinear velocity and acceleration of the moving platform. Afterward, several dynamic performance indices, which are homogenous and possess obvious physical meanings, are proposed. These indices can evaluate the power input and output transmissibility of the robot in a workspace. The distributions of the power input and output transmissibility of the high-speed parallel robot are derived with these indices and clearly illustrated in atlases. Furtherly, a low-power-consumption workspace is selected for the robot.     

新型四足步行机器人串并混联腿的运动学分析

针对串联四足机器人行走惯量大,自重/载重比大的问题,提出一种新型串并混联四足步行机器人,并对该机器人的串并混联腿进行运动学分析。该机器人由一个运载平台和四条结构相同的串并混联腿组成,每条腿均由髋关节、大腿、小腿顺次连接构成,其中髋关节为3-RRR并联机构。以能耗最小姿态为最优姿态,基于矢量法求解了该串并混联腿的运动学正解和反解,利用MATLAB和ADAMS软件验证了正解和反解的正确性;基于矢量法和微分变换法求出了该混联腿的速度雅克比矩阵和加速度矩阵,分析了其奇异性,并利用MATLAB软件绘制出该腿的工作空间。结果表明:该腿在髋关节连杆直径d=22mm,大腿杆件直径D=50mm,膝关节转角θ4∈[105°,155°]时,工作空间呈球冠形,最大内接圆半径R=400mm,高度为H∈[500mm,900mm]。本研究对该新型串并混联四足步行机器人的刚度分析、动态性能、机构优化设计和系统控制等的进一步研究具有重要意义。     

一种新型二自由度并联机构的运动学及静力学分析

针对物料搬运机构需要较大横向位移的特点,对一种新型平面二自由度并联机构的位置正反解、奇异性、速度雅可比矩阵、工作空间、滑块驱动力等方面进行了研究,提出了该种机构的运动学及静力学分析方法。首先通过所建立的运动学模型,推导了该机构的位置正反解和雅可比矩阵,得到了在符合实际约束条件下的工作空间。然后利用虚功原理建立静力学模型,获得了具体的静力学模型表达式。最后通过Solid Works及Matlab仿真得到了机构在一定负载下运动时的各驱动力变化图谱。研究结果表明,该二自由度并联机构确实具有大横向位移的特点,且机构末端越接近驱动滑块,在相同输入步长下机构末端沿横向移动距离越大,驱动滑块所需的最大驱动力也越大。     

单开链法在并联机器人设计中的应用

以单开链的基本理论为基础,通过对运动副的合理配置,以单开链支路为单元,设计出一种新型的并联机器人机构.该机构具有3个完全相同的结构,保持了结构的对称,满足了各向同性的要求.研究结果表明,该机构具有二维移动和三维转动5个自由度.     

新型6-PRRS并联机器人工作空间与结构参数研究

针对一种新构型的6-PRRS并联机器人,研究了该机构中长杆、短杆、固定平台、动平台结构参数的变化对其工作空间的影响.根据此类并联机器人工作空间形状的特点,提出一种比较简便的工作空间大小比较方法.不同的结构参数对应于不同的工作空间,通过机构参数影响的分析,为此类并联机器人的应用与设计提供直接的依据.