人手抓持识别与灵巧手的抓持规划

本文研究灵巧手采用指尖抓持方式时的抓持规划方法．在相同的操作环境和操作对象下 ，由人手决定抓持接触点的位置，利用人手运动测量装置测量人手抓持位置，通过一定的映 射关系将其转换为灵巧手的抓持位置及其掌系的位姿，再根据灵巧手自身的结构通过运动学 反解确定其抓持位形．     

机器人灵巧手抓持分类器的设计与实现

机器人灵巧手的抓持分类是抓持规划的一个主要问题．本文应用模式识别技术设计和实现了 一种基于高斯混合模型GMM的分类器． 采用Expectation Maximization(EM)算法估计GMM的 参数，对人手的抓持动作进行识别与分类，经过人手到机器人手的关节空间运动映射，实现 了机器人灵巧手的抓持动作分类．该分类器可以应用于在线抓持规划．     

虚拟环境中灵巧手主从抓持的实现

研究了虚拟现实环境中人手和灵巧手的抓持动作.利用数据手套采集人手的运动信息,将人手的运动 映射给灵巧手,通过搭建人手和灵巧手的模型,在虚拟环境下实现了主从抓持操作.探讨了关键技术问题:异构系统 运动映射、碰撞检测、虚拟力建模、稳定抓持的判据.􀁱     

自重影响下对称结构三指灵巧手的抓持规划与分析

将驱动电机置入灵巧手指内部，使得灵巧手指自重对操作性能的影响增大．文中对所设计的对称结构三指灵巧手进行了受力分析，并在此基础上建立了手指自重对灵巧手指关节力矩影响的优化目标函数，以寻求不同手掌方位角下关节的最优抓持位形．通过对不同手掌方位角下关节力矩的优化分析，确定了手掌方位角与手指最佳位形之间的映射关系．将优化结果应用于实际机器人系统，其运行结果表明了该分析方法的有效性．     

灵巧手抓持规划的虚拟仿真方法

本文介绍在虚拟环境中,通过仿真分析的手段来研究机器人灵巧手抓持规划方案的方法.研究中以人的经验为指导,根据手、物的形状及尺寸等相对关系初步给出定性的抓持方案,以此为基础在虚拟环境中对机器人灵巧手的抓持过程进行仿真分析,判定所给出的抓持规划是否能实现在虚拟环境中的稳定抓持.然后在可行方案的基础上进一步对灵巧手的抓持点位置及抓持姿态进行优化,最终可得到机器人灵巧手对于特定被抓持物的较令人满意的抓持规划方案.     

灵巧手抓持规划的虚拟仿真方法

本文介绍在虚拟环境中,通过仿真分析的手段来研究机器人灵巧手抓持规划方案的方法。研究中以人的经验为指导,根据手、物的形状及尺寸等相对关系初步给出定性的抓持方案,以此为基础在虚拟环境中对机器人灵巧手的抓持过程进行仿真分析,判定所给出的抓持规划是否能实现在虚拟环境中的稳定抓持。然后在可行方案的基础上进一步对灵巧手的抓持点位置及抓持姿态进行优化,最终可得到机器人灵巧手对于特定被抓持物的较令人满意的抓持规划方案。     

人手到灵巧手的运动映射实现

本文研究主从操作中人手到灵巧手的运动映射．提出了一种基于虚拟关节和虚拟手指的关节空间运动映射方法，实现了人手和灵巧手的三维运动仿真．以数据手套为人机接口，在虚拟环境下，通过直观地比较映射效果，验证了映射算法．     

4DOF仿人手概念设计与抓持能力分析

本文提出了一种4自由度仿人手的概念设计及自由度分配方案,拟通过进行自由度的合理分配,提高少自由度仿人手的抓持能力,从而解决仿人手目前面临的少自由度和高抓持性能需求的矛盾.借鉴人手抓持分类方法,分别就精度抓持、力度抓持及人手常用抓持手势、手语进行抓持规划,并利用虚拟样机技术进行抓持仿真,表明该手能够完成抓圆柱、圆锥、球及拇指与其余手指对捏等不同类型的抓持任务.同时该手还可做出握手、OK等手势以及13种聋哑人字母语的手语,表明该手具有一定的用人类手势手语方式与人交流的能力.     

虚拟手抓持规则融合策略研究

群体虚拟手抓持规则是虚拟手和虚拟物体进行抓持操作的交互规则,用于判定虚拟手是否能够成功抓持物体。对基于几何的虚拟手抓持规则和基于物理的虚拟手抓持规则分别进行了研究,针对基于几何的虚拟手抓持规则规则简单、仿真效果较差,基于物理模型的虚拟手抓持规则计算复杂、难以实现实时仿真的问题:（1）改进基于几何的虚拟手抓持规则,通过接触点位置、法矢和抓持面法矢制定抓持规则,使其效果逼近力封闭虚拟手抓持规则;（2）利用力封闭计算中抓持接触点和法矢不变的特性,通过内力配比避免了抓持操作中的非线性规划求解,使抓持操作阶段实现实时仿真;（3）通过几何约束进行初始抓持判断-力封闭计算校正-内力配比力封闭计算的策略,实现了完整的抓持过程实时仿真。设计的交互实验说明该抓持规则能实现高沉浸感和实时性的抓持仿真,可以应用到虚拟训练、虚拟装配等仿真平台。     

多指手操作:运动学算法和实验

本文探讨了多指手的运动学操作问题，即给出被抓物体所要运动的轨迹，如何用多指手进行操作以实现物体的运动，也即怎样根据物体的运动来确定各手指的运动．我们提出和考察了三种运动学操作算法：广义逆算法、接触轨迹控制算法和抓持优化算法．每种算法各有其特点，可根据具体的操作任务加以采用，甚至可综合用于复杂操作任务的不同阶段．在实验系统ＨＫＵＳＴＨＡＮＤ上以两指手操作蓝球的实验实现了这些算法，考察了其可行性和有效性．     

基于深度神经网络的多指灵巧手抓取手势优化

基于深度神经网络模型,提出了一种适用于多指灵巧手的抓取手势优化方法。首先,在仿真环境下构建了一个抓取数据集,并在此基础上训练了一个卷积神经网络,依据目标物体单目视觉信息和多指灵巧手抓取位形来预测抓取质量函数,由此可以将多指灵巧手的抓取规划问题转化为使抓取质量最大化的优化问题,进一步,基于深度神经网络中的反向传播和梯度上升算法实现多指灵巧手抓取手势的迭代与优化。在仿真环境中,比较该网络和仿真平台对同一抓取位形的抓取质量评估结果,再利用所提出的优化方法对随机搜索到的初始手势进行优化,比较优化前后手势的力封闭指标。最后,在实际机器人平台上验证本文方法的优化效果,结果表明,本文方法对未知物体的抓取成功率在80%以上,对于失败的抓取,优化后成功的比例达到90%。     

Automatic grasp planning for multifingered robot hands

In this paper the development of a planning environment is described which was especially tailored for grasping and manipulating with multifinger robot hands. The research has been concerned with the programming and simulation system of the Karlsruhe dextrous hand, which has been in development for two years. The work presents the result of a geometric-mechanic approach to the object-handling problem with dextrous multifinger hands by selecting grasp points and searching grasp forces to perform desired assembly tasks. The knowledge representation for the sequence planning and command execution is based on object and task restrictions combined with routines for successive optimization and a constraint propagation algorithm.     

Development of normative data for cylindrical grasp pressure

Normative data of grasp strength (GS) are commonly used in working and clinical environments. Squeezing two parallel bars of a handgrip instrument is a common method to measure GS. These instruments require the use of hook grasp position which differentiates from the other types of power grasp in terms of inclusion of the thumb. Therefore, strength performance measured with these types of dynamometers cannot be generalizable to the other types of power grasp. Although several studies have been conducted to form normative data of hook and spherical grasp strengths, a satisfactory cylindrical grasp strength norm has not been reported yet. The measurement of grasp pressure (GP) is another way of establishing the grasping capabilities of the hand and the preferred method for fragile and weak hands. The purposes of the study were to develop normative data of cylindrical GP in a healthy population and to analyze the changes in the means according to physical demands of the subjects’ jobs. 770 healthy subjects (382 females, 388 males) were found to be eligible to participate in the study. A custom-made adapted sphygmomanometer having a cylindrical air-filled bag was used to measure GP. Occupational categories of the subjects were determined based on the classification in the Dictionary of Occupational Titles. The subjects were accommodated to 12 age groups per gender of five-year intervals. The mean GP of the male subjects were higher than those of female subjects in each age group. There were significant differences between the dominant and non-dominant hands in both sexes. Subjects older than 70 years achieved the lowest values. The changes of the means over age were in compliance with the curvilinear function. Only age factor was found to be resulted in significant differences in GP means at both hands of the subjects. The minimum GP means were in the “sedentary” category at both sexes (F: 225, M: 315 mmHg in the dominant hands). Male subjects in the “very heavy” category produced the highest test means (M: 371 mmHg). Further analysis on 52 male subjects demonstrated that hand length, hand circumference and palm length had the highest correlations with GP scores in sequence.

Relevance to industry

Development of hand strength norms for a particular type of grasping is necessary for ergonomic evaluations and design purposes. By using this data, it is possible to estimate the relative load levels on a worker. Hand strength measurements are also important in determining the workers at risk and diagnosing some musculoskeletal problems.     

Grasp evaluation and contact points planning for polyhedral objects using a ray-shooting algorithm

Grasp evaluation and planning are two fundamental issues in robotic grasping and dexterous manipulation. Most traditional methods for grasp quality evaluation suffer from non-uniformity of the wrench space and a dependence on the scale and choice of the reference frame. To overcome these weaknesses, we present a grasp evaluation method based on disturbance force rejection under the assumption that the normal component of each individual contact force is less than one. The evaluation criterion is solved using an enhanced ray-shooting algorithm in which the geometry of the grasp wrench space is read by the support mapping. This evaluation procedure is very fast due to the efficiency of the ray-shooting algorithm without linearization of the friction cones. Based on a necessary condition for grasp quality improvement, a heuristic searching algorithm for polyhedral object regrasp is also proposed. It starts from an initial force-closure unit grasp configuration and iteratively improves the grasp quality to find the locally optimum contact points. The efficiency and effectiveness of the proposed algorithms are illustrated by a number of numerical examples.     

Grasp stability analysis based on acceleration convex polytopes for multi-fingered robot hands

In this paper, we present the analysis of grasp stability for multi-fingered robot hands that is based on translational and rotational acceleration convex polytopes. The aim of the grasp stability analysis is to find the resistance forces and moments of robot hands that can withstand the external disturbance forces and moments applied on objects. We calculate the resistance forces and moments respectively which are considered the properties of objects and robots. Therefore, the resistance forces and moments depend on the joint driving torque limits, the posture and the mass of robot fingers, the configuration and the mass of objects, the grasp position, the friction coefficients between the object surface and the end-effectors of robot fingers. We produce the critical resistance force and moment which are absolutely stable about external disturbances in all directions, the global resistance force and moment which are whole grasp capability of robot hands, and the weighted resistance forces and moments which can be properly used by controlling two indices according to the importance of robot hands. The effectiveness of this method is verified with simulation examples. Recommended by Editorial Board member Hyoukryeol Choi under the direction of Editor Jae-Bok Song. Myeong Eon Jang received the B.S. and M.S. degrees in Mechanical Engineering from Chonnam National University, Gwangju, Korea in 1987 and 1990, the Ph.D. degree in the Department of Mechatronics Engineering at Chungnam National University, Daejeon, Korea in 2009, respectively. Since 1993, he has been a Researcher in the Agency for Defense Development (ADD), Daejeon, Korea. His research interests include robotics and intelligent control. Jihong Lee received the B.S. degree in Electronics Engineering from Seoul National University, Korea in 1983, and the M.S. and Ph.D. degrees from the Korea Advanced Institute of Science and Technology (KAIST), Daejeon, Korea, in 1985 and 1991, respectively, all in Electrical and Electronics Engineering. Since 2004, he has been a Professor in the Mechatronics Engineering Department of Chungnam National University, Daejeon, Korea. His research interests include robotics, intelligent control, multi-robot localization and path planning.     

The role of quantitative information about slip and grip force in prosthetic grasp stability

Prosthetic hands introduce an artificial sensorimotor interface between the prosthesis wearer and the environment that is prone to perturbations. We analyze theoretically and evaluate psychophysically the performance in stable grip control in conditions of physical grasps perturbation, such as object slip. Simulation results suggest that user-centered stable grasp control depends on two primal user parameters: reaction time to slip and grip force intensity. Experiments with human users indicate that a user’s response time can be controlled by relaying information about the speed of the slipping object, while minimal grip force intensity can be adjusted with information about grip force at the onset of the slip. Based on our theoretical and experimental findings, we propose a stable grasp control method for prosthetic hands.     

Grasp capability analysis of multifingered robot hands

This paper addresses the problem of grasp capability analysis of multifingered robot hands. The aim of the grasp capability analysis is to find the maximum external wrench that the multifingered robot hands can withstand, which is an important criterion in the evaluation of robotic systems. The study of grasp capability provides a basis for the task planning of force control of multifingered robot hands. For a given multifingered hand geometry, the grasp capability depends on the joint driving torque limits, grasp configuration, contact model and so on. A systematic method of the grasp capability analysis, which is in fact a constrained optimization algorithm, is presented. In this optimization, the optimality criterion is the maximum external wrench, and the constraints include the equality constraints and the inequality constraints. The equality constraints are for the grasp to balance the given external wrench, and the inequality constraints are to prevent the slippage of fingertips, the overload of joint actuators, the excessive forces over the physical limits of the object, etc. The advantages of this method are the ability to accomodate diverse areas such as multiple robot arms, intelligent fixtures and so on. The effectiveness of the proposed method is confirmed with a numerical example of a trifingered grasp.