Dynamic modeling of flexible-links planar parallel robots

This paper presents a finite element-based method for dynamic modeling of parallel robots with flexible links and rigid moving platform. The elastic displacements of flexible links are investigated while considering the coupling effects between links due to the structural flexibility. The kinematic constraint conditions and dynamic constraint conditions for elastic displacements are presented. Considering the effects of distributed mass, lumped mass, shearing deformation, bending deformation, tensile deformation and lateral displacements, the Kineto-Elasto dynamics (KED) theory and Lagrange formula are used to derive the dynamic equations of planar flexible-links parallel robots. The dynamic behavior of the flexible-links planar parallel robot is well illustrated through numerical simulation of a planar 3-RRR parallel robot. Compared with the results of finite element software SAMCEF, the numerical simulation results show good coherence of the proposed method. The flexibility of links is demonstrated to have a significant impact on the position error and orientation error of the flexible-links planar parallel robot.     

Analysis of the dynamic stress of planar flexible-links parallel robots

This paper presents a method for the dynamic stress analysis of planar parallel robots with flexible links and a rigid moving platform. The finite element-based dynamic model of flexible parallel robots is proposed. The relation between elastic deformations and elastic displacements of the flexible links is investigated, considering the coupling effects of elastic motion and rigid motion. The elastic deformations of links are calculated. Considering the effects of bending-shearing strain and tensile-compression strain, the dynamic stress of the links and its position are derived by using the Kineto-Elastodynamics theory and the Timoshenko beam theory. Due to the flexibility of the links, the dynamic stresses are well illustrated through numerical simulation. Compared with the results of the finite element software SAMCEF, the numerical simulation results show the good coherence and advantages of the analysis method. The dynamic stress analysis is demonstrated to have a significant impact on the analysis, design and control of flexible parallel robots.     

State-of-the-art on theories and applications of cable-driven parallel robots

Cable-driven parallel robot (CDPR) is a type of high-performance robot that integrates cable-driven kinematic chains and parallel mechanism theory. It inherits the high dynamics and heavy load capacities of the parallel mechanism and significantly improves the workspace, cost and energy efficiency simultaneously. As a result, CDPRs have had irreplaceable roles in industrial and technological fields, such as astronomy, aerospace, logistics, simulators, and rehabilitation. CDPRs follow the cutting-edge trend of rigid–flexible fusion, reflect advanced lightweight design concepts, and have become a frontier topic in robotics research. This paper summarizes the kernel theories and developments of CDPRs, covering configuration design, cable-force distribution, workspace and stiffness, performance evaluation, optimization, and motion control. Kinematic modeling, workspace analysis, and cable-force solution are illustrated. Stiffness and dynamic modeling methods are discussed. To further promote the development, researchers should strengthen the investigation in configuration innovation, rapid calculation of workspace, performance evaluation, stiffness control, and rigid–flexible coupling dynamics. In addition, engineering problems such as cable materials, reliability design, and a unified control framework require attention.     

Linear quadratic optimal controller for cable-driven parallel robots

In recent years, various cable-driven parallel robots have been investigated for their advantages, such as low structural weight, high acceleration, and large workspace, over serial and conventional parallel systems. However, the use of cables lowers the stiffness of these robots, which in turn may decrease motion accuracy. A linear quadratic (LQ) optimal controller can provide all the states of a system for the feedback, such as position and velocity. Thus, the application of such an optimal controller in cable-driven parallel robots can result in more efficient and accurate motion compared to the performance of classical controllers such as the proportional-integral-derivative controller. This paper presents an approach to apply the LQ optimal controller on cable-driven parallel robots. To employ the optimal control theory, the static and dynamic modeling of a 3-DOF planar cable-driven parallel robot (Feriba-3) is developed. The synthesis of the LQ optimal control is described, and the significant experimental results are presented and discussed.     

Module-based method for design and analysis of reconfigurable parallel robots

This paper presents a method for the design and analysis of reconfigurable parallel robots. The inherent modularity in a parallel robot lends itself as a natural candidate for reconfiguration. By taking the branches as building blocks, many modular parallel robots can be constructed, from which a reconfigurable parallel robot can be realized. Among three types of reconfigurations, namely, geometry morphing, topology morphing, and group morphing, the method presented here is for the last two reconfigurations, thereby advancing the current research that is mainly limited to geometry morphing. It is shown that the module-based method not only provides a systematic way of designing a reconfigurable parallel robot, but also offers a unified modeling for robot analysis. Two examples are provided, one showing the topology morphing and the other showing the group morphing.     

3-RTT并联机器人奇异位形空间分析

采用基于机构瞬时运动分析的方法,建立了3—RTT并联机器人的奇异位形判别阵。分析了3—RTT机器人处于奇异位形时机构所满足的几何条件。编制了基于三维搜索算法的奇异位形空间分析程序,时实例进行搜索计算和分析,给出了3-RTT机器人的奇异位形空间的图形,并对其分布规律进行了分析。     

3-RRRT并联机器人工作空间与灵巧度的分析

旨在研究和分析3-RRRT并联机器人的工作空间和灵巧度。运用了齐次坐标系法对3-RRRT并联机器人机构进行了分析，给出属于工作空间点的判别条件，并进行了数值仿真；给出了3-RRRT并联机器人灵巧度的计算公式，并进行了数值仿真。     

A robust forward-displacement analysis of spherical parallel robots

The forward-displacement analysis of spherical parallel robots (SPRs) is revisited. A robust approach, based on the input–output (I/O) equation of spherical four-bar linkages, is proposed. In this approach, the closed-loop kinematic chain of a SPR is partitioned into two four-bar spherical chains, whose I/O equations are at the core of the analysis reported here. These equations lead to a trigonometric equation in the joint angles, which is solved semigraphically to obtain the joint variables for the determination of the moving plate orientation. Examples are included to demonstrate the application of the method.     

新型并联机器人坐标测量机误差建模与仿真

介绍了一种新型五自由度并联机器人坐标测量机机构,该测量机机构具有五个驱动分支和一个约束分支,可以实现三维移动和二维转动。为了给该坐标测量机实际误差的补偿和控制奠定理论基础,提高测量精度,改善测量性能,根据其位置反解数学模型,导出了测头位姿误差与各运动副位置误差、调节器运动误差及测头长度误差之间的相互关系,建立了该测量机的误差模型,并通过计算机仿真对误差模型的正确性进行了验证。     

基于柔体动力学分析的平面并联机器人结构优化设计

针对高速高精度机器人的结构柔性问题，提出了一种基于柔体动力学分析的结构参数优化设计方法，并对一种含平行四边形结构的平面并联机器人进行了结构参数优化。采用离散梁模型来仿真机器人的柔性，轴套模型来仿真机器人关节的柔性，建立了参数化的柔体动力学模型。利用动力学仿真软件ADAMS对机器人的动态响应、驱动力矩和固有频率进行了计算，据此对机器人的结构参数进行了优化。最后通过固有频率测试和动态响应实验结果验证了优化设计的有效性和准确性。     

挖掘机器人的模型与自适应模糊滑模控制

为实现挖掘机器人的自动挖掘,在挖掘机器人的轨迹规划器给出铲斗期望运动轨迹的情况下,需要挖掘机器人的控制系统能够控制其工作装置实现对给定轨迹的准确跟踪.利用拉格朗日方法建立了挖掘机器人工作装置的三自由度动力学方程,设计了自适应模糊滑模变结构控制器.利用模糊控制动态调节切换增益,将滑模控制的切换项转化为连续的模糊系统,增强了控制系统对挖掘机器人工作装置不确定性和外界干扰的鲁棒性,削弱了滑模控制的抖振现象,并且有较强的自适应跟踪能力.利用MATLAB7.4/Simulink工具箱对所设计的控制器进行了仿真,给出了自适应模糊滑模控制的跟踪性能及误差.     

套装式助力机器人动力学建模与仿真

针对老年人或者下肢功能较弱患者自主行走存在一定困难的问题,研究了一种能够辅助其行走的套装式助力机器人.机器人工作时绑缚在人体上,为行走提供动力.机器人左右对称,单侧机构包括髋关节和膝关节两部分,分别由直流电机驱动丝杠螺母机构的电动缸实现.基于Matlab/Simulink和SimMechanics建立了套装式助力机器人...     

平面2自由度驱动冗余并联机器人的输出速度分析

机器人的性能分析是机器人机构设计的前提和基础。以一种平面2自由度驱动冗余并联机器人为研究对象，根据该并联机器人机构的空间模型和运动学反解，探讨了该并联机器人机构的末端输出速度性能指标与杆件尺寸之间的关系，并绘制了相应的性能图谱，这些图谱是该并联机器人机构设计的重要参考依据。     

Elasto-geometrical error modeling and compensation of a five-axis parallel machining robot

Parallel manipulators have the potentials of high efficiency and high precision in the field of machining and manufacturing. However, accuracy improvement of the parallel manipulator is still an essential and challenging issue, encountering two important problems. Firstly, the ignorance of elastic deformation caused by gravity or deviations of static stiffness model restricts further improvement of accuracy. To solve this problem, an elasto-geometrical error modeling method is proposed. The comprehensive effects of structural errors, elastic deformation under gravity and compliance parameter errors on pose deviations are disclosed. On this basis, the identification equation of actual structural errors and compliance parameter errors can be established. Secondly, the ill-conditioned identification matrix and the identification equation with anisotropic residual error can lead to inaccurate identification results. To solve this problem, a weighted regularization method is proposed. The identification equation with isotropic residual error is built, and accurate identification can be realized with the regularization method. Based on the proposed methods, the error compensation experiment is conducted on the prototype of a five-axis parallel machining robot using a laser tracker. Experiment results show that the accuracy of the machining robot is significantly improved after compensation. An M1_160 test piece and an S-shaped test piece are machined and measured to further validate the effectiveness of the proposed methods. The elasto-geometrical error modeling method and the weighted regularization method can be applied to other parallel manipulators’ accuracy improvement.     

高速并联机械手动力学建模及计算力矩控制

基于模型的计算力矩控制由于考虑了非线性补偿而极大地提高了其控制品质。然而,并联机械手动力学模型的计算是非常耗时的,从而限制该控制器在工程中的应用。为此,针对2-DOF并联机械手Diamond 600,首先导出了机械手的位置、速度和加速度逆解模型,并根据动能定理独立计算出机械手的质量惯性矩阵,实现了控制算法解耦,然后利用虚功原理建立能用于实时控制的动力学简化模型。在此基础上,设计了适舍于并联机械手的计算力矩控制器。最后,将设计的控制器应用到2-DOF并联机械手,仿真和实验结果验证了算法的有效性和正确性。     

平面2自由度并联机器人的动力学设计

通过对平面二自由度并联机器人动力学的研究和系统存在耦合原因的分析,得出了机构设计的五点措施。采用这些措施对提高平面二自由度并联机构系统的动态特性、易控性,以及增强系统运行的稳定性和精度等都具有重要的作用。最后,通过两个算例验证了这些措施的可行性和效果,经过参数调整后的系统大大降低了驱动力矩和能耗。     

2TPR&2TPS 并联机构的位姿误差建模与补偿研究

位姿精度是评价机器人性能好坏的一个重要指标,建立有效的补偿算法是提高机器人位姿精度的重要保证。 本文以 一种 2TPR&2TPS 并联机器人为研究对象,建立了基于正解的误差模型,根据该误差模型得出了动、静平台位置参数误差及 驱动杆零点长度误差与机器人末端位姿误差的关系,同时建立了基于逆解的补偿算法。 通过粒子群算法对误差函数的最小 值寻优,得到了机器人驱动杆补偿量和位姿补偿量,仿真得出该机器人的平均位置精度提升了 98. 148% ;将驱动杆补偿量与 理想位姿对应的驱动杆长叠加作为机器人的驱动杆输入量进行实验验证,实验得出机器人的平均位置精度提升了 87. 457% ,补偿效果显著。     

基于并行计算的可调节型6-SPS并联机器人运动学和动力学分析

利用一种矩阵的广义标量积,导出6-SPS并联机器人动平台和驱动腿的速度及加速度显式表达式,并运用虚功原理和达朗伯原理建立了动力学模型。根据其计算特点,构造动力学并行算法,减少在线计算量和时间,为机构的实时控制提供有利条件。还对其作为可调节型机构,研究了平台半径和构件质量对驱动力的影响。给出的仿真实例证明此方法的有效性。     

基于交流伺服电机驱动的并联机器人动态滑模控制

并联机器人具有刚度大、承载能力强、误差小等特点,针对以交流伺服电机驱动的并联机器人机构--GPM-200并联机构,建立了控制系统模型,并在其工作空间中进行了轨迹规划,而后设计了一种动态滑模控制算法,在Matlab/Simulink上进行了仿真实验,结果表明:该算法鲁棒性好,且系统抗干扰能力强,对系统参数变化不敏感,具有良好的跟踪性能,实现了对该并联机器人的高精度实时控制.     

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。