基于动态松弛法的柔索驱动并联机器人位置正解分析

根据悬链线解析表达式推导出悬索两端固定时索端拉力与索长之间的关系,用于求解特定长度的驱动柔索对处于某一位姿的动平台的作用力.动态松弛法可以从任意的初始状态开始,通过简单迭代而使系统达到静平衡状态.将该方法应用到柔索驱动并联机器人的位置正解分析中,可以得到与特定索长对应的动平台位姿.以舱索系统为例验证了方法的正确性.     

并联机器人刚度与静力学研究现状与进展

并联机器人的刚度与静力学分析, 对于机构力学性能研究具有重要的理论价值和意义. 本文围绕杆支撑、绳牵引和钢带传动 3 种结构形式, 详细阐述了国内外并联机构刚度和静力学分析的研究现状. 着重从有限元、解析模型和性能分析 3 方面分析了杆支撑并联机构的刚度研究进展. 讨论了有关绳牵引并联机构中绳拉力、动载荷频率、绳牵引预紧力与刚度、静力学之间关系的研究成果. 根据钢带并联机器人结构的特殊性, 对钢带并联机构的刚度与静力学分析中可能遇到的失稳与振动问题进行了探讨. 最后, 对并联机器人技术发展情况进行总结与展望, 指出随着刚度分析与静力学分析的不断深入, 并联机器人的力学理论将会日趋成熟和完善, 为并联机器人机构优化设计提供更深入、系统的理论依据.      

基于视觉测量与神经网络的工业机器人位姿补偿

为提高六轴工业机器人的绝对定位精度，本文提出了一种利用视觉测量数据通过ELM(Extreme Learning Machine)神经网络实现机器人位姿补偿的新方法．利用固定在机器人末端的手眼相机获取机器人的末端位姿，并借助ELM实现机器人末端执行器从目标位姿到预测指令位姿之间映射，用修正转角代替原转角使机器人末端执行器运行至修正位姿，实现补偿．特别的是，对于使用的ELM，以网络预测均方误差为指标定量选取了网络的最佳参数．相比之前的方法，本文提出的算法具有能够同时高精度补偿姿态角及位置误差的显著优点．为验证该位姿误差补偿方法的有效性，本文进行了实验验证．结果表明，相比较于未补偿前的机器人末端位姿误差，经该方法补偿后的位姿误差被稳定控制在较低水平，平均位置误差降低89.1 %；平均姿态角误差降低96.8 %．除此以外，位置误差与姿态角误差的标准差也分别降低了85.66 %和93.24 %．     

双臂空间机器人系统末端惯性空间轨迹的反馈跟踪控制

本文讨论了载体位置不受控制的双臂空间机器人系统的载体姿态与机械臂末端抓手协调运动的控制问题.结合系统的动量守恒关系对双臂空间机器人系统的运动学、动力学作了分析,推导出了系统的载体姿态与机械臂末端抓手协调运动的增广广义Jacobi关系.并以此为基础,给出在载体位置不受控制的情况下,惯性坐标系内双臂空间机器人系统的载体姿态与机械臂末端抓手协调运动的反馈跟踪控制规律.研究结果表明,在系统动力学模型及参数较精确确定的情况下,本文提出的控制方案能够有效地控制双臂空间机器人机械臂的末端抓手与载体姿态准确地完成指定的运动,而不需对其载体的位置进行主动控制.仿真计算结果证实了方法的有效性.     

滑轮在索上滑行分析的索-轮单元法

为了分析索结构中滑轮在悬索上行走及连续长索从滑轮下绕行问题,创建了一种新的单 元. 被称为索-滑轮单元的三节点新单元模拟一段索支承滑轮,滑轮的中心取为中间节点, 索的两端点为另外两节点. 基于有限元分析的基本原理,并利用处于平衡状态时单元内力之间的关系,推导了单元的算法. 这种新单元可以通过自动调整滑轮两侧索段的长度使单元处于平衡状态,从而简化了计算. 算例证明了新单元的算法及所编制程序的正确性,同时说明了它在工程中的应用. 给出了构成刚度阵的各矩阵的显式表达式. 新单元可以直接用于常规的有限元分析中,分析处于工作状态或施工中的索结构.     

柔索构形与张力的测试装置和试验研究

现代工程中,柔索结构的应用日益广泛,简单的理论分析难以满足复杂工程的需要,柔索静动态空间构形与张力测试技术对柔索理论研究和工程应用具有重要的意义,而目前尚没有一套完备的测试装置和技术标准。针对上述情况,本文设计并制造了柔索空间构形与张力测试装置,并通过不锈钢圆环链条的静态空间构形和张力测试试验,与悬链线理论的计算结果进行对比,验证测试装置的可靠性与稳定性。试验结果表明:所建立的装置可以满足柔索的空间构形与张力测试的需要,结果准确,精度较好。证明该装置可以为柔索找形、空间构形、张力、运动轨迹和极限状态等柔索力学特性研究提供试验支持。     

索托桥结构分析的滑移索单元法

为在索托桥的结构分析中精确模拟连续长索的滑动,本文创建了一种新的单元。被称为“滑移索单元”的新单元有三个节点,以点接触的形式模拟索从下方绕过滑轮,它可以通过自动调整两侧索段的长度而使单元处于平衡状态,从而简化了计算。新单元算法的推导基于有限元分析的基本原理和弹性悬链线的解析解,并利用了平衡状态时单元内力之间的关系。本文介绍滑移索单元的推导过程,用设计的算例验证了它的正确性,分析了连续长索的滑移对索托桥桥面竖向变形的影响。新单元可以直接用于常规的有限元分析中,研究处于工作状态或在施工中的索结构。     

冲击波荷载作用下拉线塔的非线性动力分析

拉线塔是一种含有柔索的非线性结构。在冲击波荷载作用下,拉线塔在三维空间内会产生大范围的非线性位移,用工程上常用的模型简化方法来分析大变形拉线塔的误差比较大。本文采用非线性有限元法编制的可在微机上运行的拉线塔非线性静、动力分析程序,计算了单根柔索的阶跃冲击响应与冲击波荷载作用下拉线塔的非线性几何大变形动力响应,计算结果与有关文献的计算结果以及试验结果非常吻合。     

基于能力评估的空间翻滚目标抓捕策略优化

由于目标的翻滚运动, 空间双臂机器人对动态目标的抓捕相比于静态目标更具有挑战性. 对抓捕策略进行优化可以提高空间双臂机器人对翻滚目标的操作能力以保证任务的成功. 本文提出了一种基于能力评估的抓捕策略优选方法. 空间双臂机器人捕获目标时, 双臂末端执行器与目标同时接触形成闭链系统, 闭链约束的引入使操作能力的评估更加复杂. 在对双臂空间机器人协调操作翻滚目标的运动学与动力学分析基础上, 建立了考虑闭链约束的协调工作空间, 并分析了基于任务兼容度的消旋能力评估指标. 建立的协调工作空间同时包含位置和姿态信息, 可以用于灵巧度的计算. 接着, 基于协调工作空间的全局灵巧度指标确定机械臂末端执行器对目标的最优抓捕点, 以及考虑相机视角约束和末端执行器对目标速度跟踪约束下的力任务兼容度指标确定空间双臂机器人捕获翻滚目标时的最优抓捕构型. 利用能力评估确定抓捕策略可以充分利用双臂的协调性以增加对动态目标的操作能力, 通过仿真验证了所提抓捕策略的可行性和有效性.      

双臂空间机器人相对载体运动的增广自适应控制方法

本文讨论了载体位置、姿态均不受控制情况下,漂浮基双臂空间机器人末端爪手基联坐标系内轨迹跟踪的自适应控制问题.系统运动学、动力学分析结果表明,结合系统动量守恒关系得到的双臂空间机器人系统动力学方程,可以表示为一组新的适当选择的系统组合惯性参数的线性函数;从而克服了惯常的空间机器入系统动力学方程,关于系统惯性参数呈非线性函数关系的难点.以此为基础,并借助于增广变量法,针对双臂空间机器人末端爪手所持载荷参数未知的情况,设计了漂浮基双臂空间机器人末端爪手基联坐标系内轨迹跟踪的增广自适应控制方案.提出的控制方案具有不需要反馈、测量漂浮基的位置、移动速度及移动加速度的显著优点.系统数值仿真,证实了方法的有效性.     

Real solutions of the direct geometrico-static problem of under-constrained cable-driven parallel robots with 3 cables: a numerical investigation

This paper addresses the direct geometrico-static problem of under-constrained cable-driven parallel robots with 3 cables. The task at hand consists in finding all equilibrium configurations of the end-effector when the cable lengths are assigned. This problem is known to admit 156 solutions in the complex field, but the upper bound on the number of real solutions is as yet an open issue. Finding this bound is the objective of the paper. For this purpose, three numerical approaches are developed, namely a continuation procedure adapted from an algorithm originally proposed by Dietmaier and two evolutionary techniques based on a genetic algorithm and particle swarm optimization. In all cases, a number of sets of robot parameters for which the direct geometrico-static problem provides at the most 54 real configurations is found. The coherence of the obtained results leads to conjecture that the achieved bound is tight. However, formal proof is yet to be discovered.     

Three-dimensional static and dynamic stiffness analyses of the cable driven parallel robot with non-negligible cable mass and elasticity

This study investigates the three-dimensional static and dynamic stiffness analyses of the cable driven parallel robot by considering cable mass, elasticity, and mass of end-effector. According to these models, optimization of cable tensions and cable lengths using fminimax solver is performed to determine the static stiffness. Static and dynamic stiffness of the cables are obtained with simulations. Results show that analyses in three-dimension are very important to measure the actual performance of the cable driven parallel robot. This demonstrates potential for general applicability and motion of the cable driven parallel robot.     

Optimal path planning of a cable-suspended robot with moving boundary using optimal feedback linearization approach

In this paper, the optimal path of a cable-suspended robot between two boundaries is assessed subject to its maximum load, while the initial and target points are moving boundary. Considering the fact that the most important application of cable robots is load carrying between two boundaries, planning the optimal path in which the heaviest load can be carried is extremely applicable. A closed loop optimal path planning algorithm is proposed in this paper for non-linear dynamic of a cable robots based on optimal feedback linearization. This method not only produces the optimal path of the end-effector, but also is robust to external disturbances and parametric uncertainties as a result of its closed loop nature. Moreover, considering the fact that in many automation applications the target of load handling is a sort of moving boundary like conveyors, finding the optimal point of this boundary which produces the optimal path with the maximum dynamic load carrying capacity (DLCC) amongst the other points of the boundary is obviously a useful study. Therefore, an online solution, based on variational algorithm is proposed here to solve the moving boundary problem which is compatible with the presented closed loop optimal path planning. This method is developed for both the initial and final moving boundaries. Finally maximum DLCC is obtained using an iterative method to check the optimality of the proposed method. The efficiency of the proposed algorithm is verified at the end by the aid of some simulation scenarios performed on a spatial six DOFs cable robot with six cables. The motors’ torque, motors’ speed, and resultant DLCCs are calculated for both simple optimal path and moving boundary cases and comparison of the results proves the mentioned claims based on superiority of the proposed algorithm of moving boundary in saving the energy and increasing the DLCC. All simulation results are supported by conducting an experimental study on the cable robot of IUST (ICaSbot) for regulation movement of the end-effector with moving boundary.     

On the determination of the force distribution in overconstrained cable-driven parallel mechanisms

This paper addresses the determination of the force distribution in the cables of a redundantly actuated cable-driven parallel mechanism. First, the static model of cable-driven parallel mechanisms is derived based on the wrench matrix. Then, four performance indices are considered in order to solve the underdetermined problem associated with the distribution of the forces. A simple numerical example is then developed in order to provide insight into the problem, which leads to a geometric interpretation of the results. Based on the presented results, it is proposed to use a p-norm (e.g. a 4-norm) to optimize the distribution of the forces in a cable-driven parallel mechanism in order to minimize the largest deviations from the median forces (or other target values) while maintaining continuity in the solution. A non-iterative polynomial formulation is then proposed for the 4-norm. It is also pointed out that this formulation leads to a unique real solution.     

STATIC ANALYSIS OF CABLE STRUCTURE

Based on the nonlinear geometric relation between strain and displacement for flexible cable, the equilibrium equation under self-weight and influence of temperature was established and an analytical solution of displacement and tension distribution defined in Eulerian coordinate system was accurately obtained. The nonlinear algebraic equations caused by cable structure were solved directly using the modified Powell hybrid algorithm with high precision routine DNEQNE of Fortran. For example, a cable structure consisting of three cables jointly supported by a vertical spring and all the other ends fixed was calculated and compared with various methods by other scholars.     

绳索的大变形问题

根据绝对柔韧杆在大变形时应变与位移的准确关系以及平衡方程;推导出绳索在自重作用下的精确关系以及平衡方程,推导出绳索在自重作用下的精确解析解．并举例对电缆进行了分析和讨论．     

An evolutionary approach for the motion planning of redundant and hyper-redundant manipulators

The trajectory planning of redundant robots is an important area of research and efficient optimization algorithms are needed. The pseudoinverse control is not repeatable, causing drift in joint space which is undesirable for physical control. This paper presents a new technique that combines the closed-loop pseudoinverse method with genetic algorithms, leading to an optimization criterion for repeatable control of redundant manipulators, and avoiding the joint angle drift problem. Computer simulations performed based on redundant and hyper-redundant planar manipulators show that, when the end-effector traces a closed path in the workspace, the robot returns to its initial configuration. The solution is repeatable for a workspace with and without obstacles in the sense that, after executing several cycles, the initial and final states of the manipulator are very close.     

Interaction solutions for a reduced extended $$\mathbf{(3}\varvec{+}{} \mathbf{1)}$$ ( 3 + 1 ) -dimensional Jimbo–Miwa equation

Heavy-duty industrial robots have great advantages in the manufacturing industry. Considering the heavy process load and low stiffness of the robot, an accurate and efficient dynamic model plays an important role in the behavior analysis and performance improvement in the robot. This paper presents a novel methodology for the inverse dynamic analysis of the heavy-duty industrial robot with elastic joints. In particular, high-order kinematics and dynamics are concisely deduced using Lie group to deal with elastic joints for the robot inverse dynamic analysis. Meanwhile, position errors of the end-effector due to elastic joints are evaluated through the inverse dynamic analysis when the robot is in heavy-duty applications. Compared with previous approaches, the advantage of proposed method is that new formulas for inverse dynamic analysis are shown to be more concise and computationally efficient using Lie group. Moreover, the position error evaluation method considering dynamic forces is proved to be more accurate than the traditional method when the robot is in the high-speed application. Because of the high computational efficiency and accurate evaluation results, the proposed approach is applicable to trajectory optimization and position error compensation, especially for the robot in heavy-load and high-speed applications.