机器人多指操作的抓取力分析和实时优化

在非线性摩擦锥约束转换为对称矩阵正定线性约束的基础上,首先将抓取力摩擦锥约束进一步转换为线性矩阵不等式约束,使抓取力封闭判别问题转化为带线性矩阵不等式约束的可行解问题,完成抓取的力封闭条件判别,然后根据摩擦锥的正定线性约束矩阵和抓取力平衡约束矩阵的分块特性和稀疏特性,实现多指滚动操作实时抓取力优化计算.最后在多指手实验平台上实现并验证了算法.     

A quasistatic manipulation for multifingered robotic hands

A generalized algorithm for the motion/force planning of the multifingered hand is proposed to generate finite displacements and changes in orientation of objects by considering sliding contacts as well as rolling contacts between the fingertips and the object at the contact point. Specifically, an optimization problem is firstly formulated and solved to find joint velocities and contact forces to impart a desired motion to the object at each time step. Then the relative velocity at the contact point is found by calculating velocity of the fingertip and the velocity of the object at the contact point. Finally, time derivatives of the surface variables and the contact angle of the fingertip and the object at the present time step are computed using the Montana’s contact equation to find the contact parameters of the fingertip and the object at the next time step. To show the validity of the proposed algorithm, a numerical example is illustrated by employing the robotic hand manipulating a circular cylinder with three fingers each of which has four joints.     

ESTIMATION OF OBJECT GRAVITY AND WRENCH EXERTED ON OBJECT USING MULTIFINGERED HAND WITH FORCE/TORQUE SENSORS

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基于虚拟构架模型分析手指包容抓取内力

在手指包容抓取物体时的内力分析中 ,基于虚拟构架模型来分析手指抓取内力 ,手指任一接触点处的内力通常能分解成该构架虚拟连接点两个 (二维平面 )或三个 (三维空间 )杆轴方向的分力 ,由虚拟构架内力 ,我们给出了二手指和三手指内力表达式。这种内力分析法为处理机器人手的抓力大小、操作规划与优化以及力控制设计等问题提供了理论基础     

一种欠驱动多指杆机器人手

提出的欠驱动多指杆机器人手能用直指或曲指方式履行各种工业操作任务。本文描述了三指多指杆手的工作原理,手指位移与力分析,这种手抓取物体的适应性,稳定性,抓力都优于常规手爪,提出的手指结构能减少控制复杂性,重量和成本,并能实现多功能地抓取不同物体的能力。     

机器人多指滚动操作的协调运动生成

分析了多指手操作基于运动学速度控制方法和主从规划方法的缺点,指出这些方法都不是真正的协调运动规划方法。通过引入最优抓取所确定的抓取姿态集合约束和衡量抓取质量指标的函数,为多指操作提出了一协调运动生成算法。当初始的抓取姿态是最优抓取时,算法协调各手指运动保持抓取最优,当初始的抓取姿态不是最优抓取时,通过定义抓取质量指标,算法生成手指运动优化抓取姿态。应用ＨＫＵＳＴ多指灵巧手验证了生成算法。     

METHOD OF CLASSIFYING GRASPS BY ROBOT HANDS

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夹具中接触力的计算

以无摩擦的点接触假设为前提，建立夹具中工件与定位元件和夹紧元件之间接触力计算模型，并针对欠定位、完全定位和过定位等不同的定位模式，讨论接触力的计算方法问题。利用提出的接触力计算模型可以检验工件夹紧的封闭性，并为定位元件和夹紧元件的结构设计提供理论指导。最后，给出一个事例验证导出的计算模型。     

基于力螺旋理论进行手指包容抓取静力分析

在手指包容抓取静力分析中，给出了基于力螺旋理论来分析手指包容抓取问题，对于给定的物体，手指模型及手指与物体间的接触方式，给出手指抵抗外力的能力，这种静力分析法对于处理机器人手的抓取操作规划与优化以及力控制设计等问题提供了理论基础。     

DLR/HIT机器人灵巧手手指位置控制的研究

手指的位置控制是灵巧手进行力控制和多指协调等操作的基础。针对DLR／HIT灵巧手手指,首先建立了手指的坐标系,划分了层次化的手指控制空间。基于驱动空间的滑膜位置控制器和轨迹规划算法,设计和实现了关节空间及笛卡尔空间的手指位置控制策略。     

On position/force tracking control problem of cooperative robot manipulators using adaptive fuzzy backstepping approach

In this paper, the position and force tracking control problem of cooperative robot manipulator system handling a common rigid object with unknown dynamical models and unknown external disturbances is investigated. The universal approximation properties of fuzzy logic systems are employed to estimate the unknown system dynamics. On the other hand, by defining new state variables based on the integral and differential of position and orientation errors of the grasped object, the error system of coordinated robot manipulators is constructed. Subsequently by defining the appropriate change of coordinates and using the backstepping design strategy, an adaptive fuzzy backstepping position tracking control scheme is proposed for multi-robot manipulator systems. By utilizing the properties of internal forces, extra terms are also added to the control signals to consider the force tracking problem. Moreover, it is shown that the proposed adaptive fuzzy backstepping position/force control approach ensures all the signals of the closed loop system uniformly ultimately bounded and tracking errors of both positions and forces can converge to small desired values by proper selection of the design parameters. Finally, the theoretic achievements are tested on the two three-link planar robot manipulators cooperatively handling a common object to illustrate the effectiveness of the proposed approach.     

仿人四指灵巧手的抓持能力分析

对四指仿人灵巧手的结构及单手指运动学及动力学进行了分析,为深入地研究该灵巧手的控制提供了理论依据。在ADAMS中进行了灵巧手抓取物体仿真实验,实时得到手指与抓取物体间的接触力值。并利用有限元方法分析了灵巧手在强力抓取时的手指结构的力学性能,验证了该灵巧手可以达到实现设计目标所要求的抓取载荷。为抓取实验提供了抓取物体重量的理论分析依据。     

基于最大力螺旋多指手抓取规划

机器人多指手抓取物体时,为了保证抓取稳定性,必须对手指与被抓物体之间的接触位置进行合理的布局,寻求最佳的抓取位置.基于此,提出基于最大力螺旋的多指手抓取规划方法,将多指手可以平衡的最大外力螺旋作为评价规划的性能指标,建立力封闭约束条件下抓取位置与最大外力螺旋优化模型,并运用神经网络进行仿真,将该方法与基于广义力椭球方法进行比较.前者弥补了广义力椭球方法的局限性,可以清楚地描述多指手抓取位置与可平衡外力螺旋之间的对应关系,定量地描述被抓物体的稳定性程度,使得抓取规划的判断更直观、更具有实用性.     

Kinematics and dynamic modeling for holonomic constrained multiple robot systems through principle of workspace orthogonalization

This paper deals with an efficient mathematical modeling for multiple robot manipulators (or multifingered robot hands) holding and transporting a rigid common object on the constraint surfaces, subject to a set of holonomic (integrable) constraints. First, the kinematics and dynamics of the multiple robot systems are formulated. After a series of model transformations, a combined dynamic model is derived from a unified viewpoint. Then the system dynamics can be decomposed into two orthogonal subsystems the (reduced-order) motion subsystem and the force subsystem. From a practical point of view, the new dynamic model presented in this paper is suitable form for dynamic analysis and hybrid (position/force) control synthesis.     

工业机械手视觉/力混合控制方案研究

对于未标定刚性环境,给出一种基于位置的视觉/力混合控制策略,实现对机械手的运动控制。在视觉引导下,机械手的末端寻找并稳定接触目标物体;当接触完全建立后,采用视觉和力同时控制机械手的运动。在任务空间内,基于边缘的刚体跟踪器把动态过程中的线性动态误差提供给局部稳定的观测器。实验和仿真结果证明了该方法的有效性。     

A dexterous robot hand with a bio-mimetic mechanism

This paper describes a development of bio-mimetic robot hand and its control scheme. This robot hand has four independently moving fingers, which are driven by four-coupled link mechanism with two linear actuators. By using the linear actuators, we make the hand similar to human hand in its structure and motion. The coupled link mechanism makes the hand compact in structure and efficient in power. The robot hand is designed considering the dexterity and the compact size suited for various tools and objects in daily life. The hand has tactile sensors mounted on the palm and the fingertips at each finger. With tactile sensor based feedback control and force closure method, the paper shows the control of the robot hand which is very stable in grasping and handling various objects.     

Superunderactuated Multifingered Hand for Humanoid Robot

A novel underactuated finger mechanism was designed. Finger mechanism was incorporated into a humanoid robot hand to obtain more degrees of freedom with less actuators and good grasping functions with shape adaptation, therefore decreasing the requirements for the control system. A novel superunderactuated multifingered hand (TH-2 Hand) for a humanoid robot was designed based on a previous underactuated finger mechanism. The TH-2 Hand was attached to a humanoid robot because of its high personification, superunderactuation, compactness, easy real-time control, small volume, light weight, and strong grasping function. This work was translated from the Journal of Tsinghua University (Science and Technology), 2004, 44(5) (in Chinese) This research is funded by the National Natural Science Foundation of China (grant 50275083) and the Education Prosperity Plan of the National Ministry of Education     

一种自适应拟人手指抓持力分析与结构优化

采用齿轮齿条传动机构，设计了一种新型自适应拟人手指。该手指自身不带驱动器，适合抓取不同形状、尺寸的物体，使机器人多指手以较少的驱动器驱动较多关节自由度。电机的数量大大减少使机器人手具有许多优点。另外，该手指与人的手指相似，适合用于拟人多指手。分析了该手指抓持力与其设计参数的关系，提出了该手指的结构优化设计原则。     

面向任务和基于几何特征的机器人多指手抓取模式规划

针对机器人多指手自身的特点,通过分析人手的抓取特性,对其可能具有的抓取模式进行分类。考虑被抓取物体的几何特征和任务要求,采用基函数为高斯核函数的RBF神经网络来表示被抓物体的样本特征和抓取模式之间的复杂非线性映射。将抓取模式分为10类,对于新的被抓物体,利用训练好的神经网络自动生成抓取模式,并利用VC++/OpenGL建立了可视化仿真平台,进行了抓取模式分类仿真实验,结果表明对于新的物体,机器人可以选择适当的抓取模式进行抓取。     

三自由度自适应抓持仿人手的设计研究

设计完成了用于仿人形机器人上的具有自动适应被抓持物体几何特征的三自由度仿人手。论文首先设计了具有自适应抓持能力的手指机构，进一步对该手指机构各关节之间的运动耦合关系进行了分析研究，并通过虚拟样机技术验证了所设计的仿人手机构传动系统的正确性和自适应抓持的可行性，最后提出了衡量仿人手抓持能力的指标，分析了所设计的仿人手的抓持能力。所有结果都表明手指机构是合理实用的，所设计完成的仿人手达到了设计要求。