综合考虑关节及杆柔性的空间机器人动力学分析

提出了空间柔性转子梁单元模型,建立了考虑关节及杆柔性的空间机器人动力学方程。首次给出了一个四杆空间机器人的数值算例,说明了柔性空间机器人的弹性变形对方向误差及位置误差都具有很重要的影响,杆和关节的弹履变形之间有相互耦合影响作用。     

柔性机器人轨迹跟踪的逆动力学分析

基于绝对坐标,以期望轨迹而不是名义刚性位置作为机器人末端点的边界条件,建立了具有柔性关节和柔性杆的机器人的逆动力学模型,此方法可使柔性机器人非常准确地跟踪期望轨迹。最后,提出了求解此类非线性方程的数值算法。通过对３Ｒ机器人进行仿真,表明本方法优于通常的方法。     

柔性机械臂动力学建模理论与实验研究进展

总结了国内外学者在柔性机械臂建模理论及其相关实验等方面的最新研究进展,系统地阐述了柔性机械臂的变形描述方法、关节动力学建模、柔性机械臂系统的动力学建模方法、臂杆的刚化和软化效应、柔性机械臂实验方法等方面的研究现状,提出了现阶段机械臂动力学理论与实验研究存在的问题与不足,预测了柔性机械臂动力学研究的主要方向和核心技术,详细分析了柔性机械臂最佳模态阶数选取、基于动力学特性的柔性机械臂系统参数优化、关节驱动规律的确定、柔性机械臂在高速运转下刚化与软化效应、柔性机械臂关节精细建模、空间柔性机械臂超低速运行时爬行现象等待解决的关键技术问题。     

基于绝对坐标的柔性机器人逆动力学建模和轨迹跟踪

采用了 Timoshenko梁理论和有限元法 ,由 L agrange方程建立了基于绝对坐标的柔性机器人逆动力学模型。由提出的非线性方程数值解法 ,求解出柔性机器人的输入关节角或驱动力矩 ,以此作为输入参量 ,可使机器人能够非常准确地跟踪末端轨迹。文中就三柔性臂机器人进行了仿真 ,验证了本方法的有效性     

柔性冗余度机器人的可操作性桑度的研究

把机器人操作器的杆件的柔度按照势能等效原理附加到杆件的伺服关节柔度上,称为等效关节柔度;利用操作器的关节空间和直角坐标空间的对偶关系,得到操作器末端的等效柔度矩阵,并提出了综合柔度的概念,以表明操作器末端柔度大小;结合冗余度机器人操作器的可操作性能,提出了在柔性冗余度机器人中操作器的柔性和可操作性对其性能的综合影响指标——可操作性柔度。通过调整冗余度机器人的"自运动"最小化可操作性柔度,从而取得具有较低的柔性和较好的操作性能的操作器的最佳工作姿态,为柔性冗余度机器人的控制提供了依据。     

柔性冗余度机器人的可操作性柔度的研究

把机器人操作器的杆件的柔度按照势能等效原理附加杆件的伺服关节柔度上,称为等效关节柔度;利用操作器的关节空间和直角坐标的空间的对偶关系,得到操作器末端的等效柔度矩阵,并提出了综合柔度的概念,以表明操作器末端柔度大小;结合冗余度机器人操作器的可操作性能,提出了在柔性冗余度机器人中操作器的柔性和可操作性对其性能的综合影响指标－－可操作性柔度。通过调整冗余度机器人的“自运动”最小化可操作性柔度,从而取得具有较低的柔性和较好的操作性能的操作器的最佳工作姿态,为柔性冗余度机器人的控制提供了依据。     

平面柔性并联机器人动力学建模

利用有限元理论研究柔性并联机器人动力学建模的理论和方法,分析各支链的弹性位移及其耦合关系,建立柔性并联机器人系统的运动约束条件和动力约束条件。综合考虑构件的分布质量、集中质量以及杆件的剪切变形、弯曲变形、拉压变形和横向位移的影响,运用运动弹性动力学理论和Lagrange方程,推导出平面柔性并联机器人的动力学方程。以平面3-RRR柔性并联机器人为例,说明该动力学模型能正确反映柔性并联机器人的弹性振动特性,杆件的弹性变形对机器人动平台的位置误差和方向误差具有重要影响。     

机器人柔性臂动力学建模的D-Holzer法

从改进柔性臂的模化原则出发,提出了多连杆复杂的柔性臂系统动力学建模的更为一般化的简单有效的D-Holzer法。用该法推导了两连杆柔性臂系统的动力学模型,并进行了动力学仿真。     

柔性欠驱动机械臂动力学耦合分析

为建立柔性3R欠驱动机械臂的动力学方程,采用Euler-Bernoulli梁模型并添加经迭代计算的边界条件,对柔性机械臂进行了动力学耦合与仿真分析。在对柔性机械臂进行模态分析的基础上,将柔性机械臂视为包含边界条件的悬臂梁和简支-自由梁模型,采用假设模态法建立柔性3R欠驱动机械臂的动力学模型。仿真结果证明：添加经迭代计算的边界条件的柔性梁模型能更好地反映自由关节的加速度耦合情况。最后对柔性欠驱动机械臂与刚性欠驱动机械臂进行关节耦合指标分析,结果表明柔性欠驱动机械臂的自由关节包含更复杂的耦合情况,对柔性机械臂弹性振动的控制是对柔性欠驱动机械臂控制的关键。     

A nonlinear finite element model for dynamics of flexible manipulators

A general nonlinear dynamics model is developed for three-dimensional flexible manipulators. A manipulator link is modelled as a beam undergoing both large gross rigid body motion and elastic deformation. The beam is discretized by the finite element method with its inertia lumped at the nodes of each element. A nonlinear strain-displacement relationship is developed to retain the geometric nonlinearity resulting from the large relative elastic deflections. The geometric nonlinearity is specifically treated so that the significance of the geometric nonlinear effects can be easily included not only in the fully nonlinear model, but also in the linearized model. Numerical results are presented to demonstrate the significant effects of geometric nonlinearity on the dynamic response of a flexible manipulator.     

Design and implementation of a novel modal space active force control concept for spatial multi-DOF parallel robotic manipulators actuated by electrical actuators

Robotic spine brace based on parallel-actuated robotic system is a new device for treatment and sensing of scoliosis, however, the strong dynamic coupling and anisotropy problem of parallel manipulators result in accuracy loss of rehabilitation force control, including big error in direction and value of force. A novel active force control strategy named modal space force control is proposed to solve these problems.Considering the electrical driven system and contact environment, the mathematical model of spatial parallel manipulator is built. The strong dynamic coupling problem in force field is described via experiments as well as the anisotropy problem of work space of parallel manipulators. The effects of dynamic coupling on control design and performances are discussed, and the influences of anisotropy on accuracy are also addressed. With mass/inertia matrix and stiffness matrix of parallel manipulators, a modal matrix can be calculated by using eigenvalue decomposition. Making use of the orthogonality of modal matrix with mass matrix of parallel manipulators, the strong coupled dynamic equations expressed in work space or joint space of parallel manipulator may be transformed into decoupled equations formulated in modal space. According to this property, each force control channel is independent of others in the modal space, thus we proposed modal space force control concept which means the force controller is designed in modal space. A modal space active force control is designed and implemented with only a simple PID controller employed as exampled control method to show the differences, uniqueness, and benefits of modal space force control. Simulation and experimental results show that the proposed modal space force control concept can effectively overcome the effects of the strong dynamic coupling and anisotropy problem in the physical space, and modal space force control is thus a very useful control framework, which is better than the current joint space control and work space control.     

Dynamic analysis of an axially moving robot manipulator supported by bearings

In this study, a robot manipulator is modelled as a cantilever beam, which moves in an axial direction, has a lumped mass at the end, and is supported by intermediate springs. Considering the tip mass and intermediate springs in the modeling, we derive the equations of motion in which the rigid-body motion is coupled with the flexible motions, and then analyze the transverse vibrations of the beam. Furthermore, we study the tip mass effects on the natural frequencies and the corresponding mode shapes. The natural frequency loci veering is analyzed for variations in the tip mass and the spring position/stiffness. In addition, we investigate the exchange and localization of modes around these veering regions as well as the parameter effects on the mode shapes. Using a Short-time Fourier transform (STFT), the relationship between the dynamic characteristics and dynamic responses are described. It is found that the dynamic characteristics of the beam are dependent on the veering distance. It is also shown via dynamic responses that the mode exchanges occur when a veering distance is close.     

一种柔性冗余度机器人振动抑制的复模态法

研究了柔性机器人末端振动的抑制控制问题,方法是将机器人动力学方程进行分解,再将分解得到的柔性振动动力学方程写成状态空间的形式,根据复模态分析的原理对其进行分析,利用柔性冗余度机器人具有的自运动优化能力,提出了一种自运动优化选择的复模态法,该方法通过自运动的优化选择在复模态空间中零化低阶模态的激励力,以实现对机器人末端振动的抑制。针对一个末杆为柔性杆的3维4自由度机器人进行了控制仿真,仿真同时对比使用了其它2种同类方法,仿真结果验证了本方法的有效性,并显示复模态法取得了比其同类方法好很多的末端振动抑制效果。     

COUPLING EFFECT OF FLEXIBLE JOINT AND FLEXIBLE LINK ON DYNAMIC SINGULARITY OF FLEXIBLE MANIPULATOR

The coupling effect of the flexible joint and the flexible link on the dynamic singularity of the flexible manipulator is addressed. Firstly, the dynamic equations of a flexible manipulator with a flexible joint and a flexible link are derived. Secondly, the relationship and property between the flexible joint and the flexible link are analyzed. It shows that the flexible joint＇s amplitude will increase abruptly, thereby the dynamic singularity occurs if the frequency of a flexible joint is near or equal to some natural frequency of a flexible link. Finally, some numerical simulations which will verify the correctness of the theoretical analysis, are carded out. The results are fundamental for the design of a flexible manipulator and for the avoidance of the dynamic singularity.     

空间刚柔性机械臂动力学模型与轨迹跟踪控制

针对双连杆刚柔性空间机械臂建立了非线性动力学方程,运用基于模型的非线性解耦反馈控制方法,得到刚柔性机械臂部分解耦形式的控制方程。讨论了空间机械臂的轨迹跟踪问题,通过二例数值仿真计算,表明了该方法的有效控制。     

具有外部扰动的参数未知漂浮基柔性空间机械臂的对角递归神经网络控制

讨论载体位置和姿态均不受控情况下,存在外部扰动的参数未知漂浮基柔性空间机械臂系统关节运动的动力学控制问题。由假设模态法,利用拉格朗日方法建立漂浮基柔性空间机械臂的系统动力学方程。以此为基础,针对存在外部扰动和系统参数未知的情况,利用对角递归神经网络逼近柔性空间机械臂系统的逆动力学模型,设计基于对角递归神经网络的控制方案,以控制柔性空间机械臂的关节铰跟踪在关节空间的期望运动轨迹,同时能抑制柔性杆的振动。该方案由于没有专门设计主动控制器抑制柔性振动,因此不需要测量、反馈柔性振动模态,大大简化控制器的结构;无需预知控制对象的精确模型和系统参数,且能克服外部扰动的影响。计算机数值仿真证实所提方案的有效性和可行性。     

垂直平面三杆柔性机械手动力学建模及仿真

为解决柔性机械手动力学建模常用的有限元等方法导致模型精度不高的问题,将柔性机械手视为连续整体,用矢量法建立了机械手的动力学模型。对比了矢量法和FEM法建立的动力学模型以及理想状态下机械手刚体动力学模型的仿真结果。对比结果表明,用矢量法建立的柔性机械手动力学模型是可行的,精度也较高。     

机器人协调操作刚性负载效率的研究

针对工业机器人的使用情况，考虑机器人臂的弹性变形，提出了以机器人关节输入功率最小作为规划目标，规划各协调机器人的承载比例和相对位置的方法。此方法可使系统效率最高并且其它动力特性较好。以具有冗余驱动的机器人协调操作系统为例，将所提目标的规划结果与通常即标的规划结果进行了比较，分析了影响系统效率和其它动力特性的因素。     

A comprehensive study of modal characteristics of a cylindrical manipulator with both link and joint flexibility

A thorough understanding of modal characteristics of vibrating manipulators is essential for improved dynamic positioning accuracy. Presented in this work is an extensive investigation of a cylindrical manipulator, consisting of a revolute and a prismatic joint. In general, for high-speed, flexible manipulators, modal properties depend mainly upon the following factors: (1) physical dimensions and material properties of components (such as arms and joints), which remain unchanged for a chosen manipulator; (2) a manipulator's position (or orientation) as a result of joint actuations; (3) the rigid-elastic coupling effect; and (4) the centrifugal stiffening effect due to the influence of internal axial force on the lateral stiffness. This work is intended to study the effects of each of the above factors on modal characteristics of the manipulator, and gives insight into the susceptibility of the modal parameters to each factor. In addition, joint flexibility has substantial influence on modal properties of a robotic system, depending on the relative importance of joint torsional stiffness to the stiffness of other members, such as the bending stiffness of arms. In the situation where the manipulator moves at a high speed, both rigid-elastic coupling and centrifugal stiffening effects can become important.     

平面柔性3-RRR并联机构自标定方法

平面柔性并联机构具有柔性机构和少自由度并联机构两者的优点,是当前研究的热点之一.提出并验证一种简单、有效的平面柔性3-RRR并联机构自标定方法.从误差建模出发,利用矢量链法推导出标定参数辨识方程.借助静平台上的标准定位圆孔,通过仪器对拉线式编码器(线尺)进行标定,进而利用线尺在线地测量、记录机构运行中的实际位姿,结合数控系统中的理论轨迹,辨识出系统模型误差.根据辨识结果对控制模型进行补偿,使平面柔性3-RRR运动平台轨迹误差得到了明显的减小,有效提高了机构的精度,完成了利用线尺进行机构自标定方法的研究.由于测量工具和建模方法通用性强,且具有在线实际位姿测量能力,该试验研究为平面柔性少自由度并联机构的自标定提供了一种切实可行的解决途径,同时为全闭环控制提供了可行的测量方法.