Manual dexterity of older Mexican American adults: a cross-sectional pilot experimental investigation

This paper reports results from an experimental pilot study performed to quantify the manual dexterity of older Mexican American adults. The Purdue pegboard test, a two-arm coordination test, and a hand-tool dexterity test were used in this study. To enable cross-sectional comparisons of manual dexterity measures of older Mexican American adults with young Mexican American adults, these tests were administered to 18 older Mexican American adults aged 63–85 (mean age: 71.3 years, SD: 7.0 years), recruited from senior recreation centers in El Paso, and eighteen young adults aged 21–32 (mean age: 25.6 years, SD: 3.8 years) recruited from the student body at the University of Texas at El Paso. For the Purdue pegboard test, the number of pegs placed in 30 s using the preferred hand, the non-preferred hand, and both hands were first individually monitored. Then, scores on an assembly task using the Purdue pegboard were obtained. For the two-arm coordination test, participants were required to trace a star pattern with a stylus using both hands. The time for task completion and the number of errors made during task performance were monitored. For the hand-tool dexterity test, participants were required to use common hand tools and remove nuts and bolts from one side of a wooden upright, and to assemble nuts and bolts in the corresponding holes on the other side of the upright. The time taken for task completion was recorded. Since modified Levene's test showed equality of variances, two sample t-tests, comparing the mean responses of older adults with the mean responses of young adults for each individual test, were conducted. Results indicate that responses for the older adults were statistically significant different (p<0.001) from young adults for all Purdue pegboard tasks. On the average, older adults performed significantly slower (p<0.001) than young adults on the two-arm coordination test, and committed more errors before task completion (p<0.05). Older adults also took longer to complete the hand-tool dexterity task compared to their younger counterparts (p<0.05). In addition to the t-tests, manual dexterity performance measures from older adults were regressed with age to determine the cross-sectional age effects on manual dexterity measures. Results indicate that all Purdue pegboard performance measures were significantly affected by age (p<0.05). The time to complete the two-arm coordination test was significantly linearly related to age (p<0.05). However, the number of errors committed by older adults in the performance of the two-arm coordination test was not significantly linearly related to age. Time to complete the hand-tool dexterity was also significantly linearly related to age (p<0.05). Accommodating age-related changes in manual dexterity is important for job design in industry, especially in industries employing older adults requiring significant assembly and hand-tool use.

Relevance to industry

Given the aging of the industrial workforce, it is important to understand how manual dexterity is affected by age, so that jobs requiring significant manual dexterity for task initiation, task performance and task completion are designed to fit older adult dexterity levels.     

3-TPT并联机构运动性能研究

以3-TPT并联机构作为研究对象,建立该机构的运动学正、反解方程,求出该机构的雅可比矩阵及其逆矩阵,并在此基础上运用MATLAB软件和LabVIEW软件对该机床的奇异性、灵,5性和平稳性性进行仿真分析。仿真结果表明：3-TPT并联机构不存在奇异位形,并且拥有较好的灵巧性和平稳性,这为并联机构的最优化设计及控制系统设计提供了理论基础,并为确定工作形位和机构尺寸提供了设计依据。     

Planning Motions of Polyhedral Parts by Rolling

The nonholonomic nature of rolling between rigid bodies can be exploited to achieve dextrous manipulation of industrial parts with minimally complex robotic effectors. While for parts with smooth surfaces a relatively well-developed theory exists, planning for parts with only piecewise smooth surfaces is largely an open problem. The problem of arbitrarily displacing and reorienting a polyhedron by means of rotations about edges belonging to a fixed plane is considered. Relevant theoretical results are reviewed, and a polynomial time algorithm is proposed that allows planning such motions. The effects of finite accuracy in representing problem data, as well as the operational and computational complexity of the method are considered in detail. Received November 15, 1996; revised February 12, 1998.     

3－TRS型关联机器人的几何特性分析

本文根据３－ＴＲＳ型机器人的结构特点，分析了它的工作空间，灵活性，奇异位形等几何特性。     

Formulating Jacobian matrices for the dexterity analysis of parallel manipulators

The condition number of the Jacobian matrix has been commonly used in determining the dexterous regions of a manipulator workspace. This has been successful when applied to manipulators having either solely spherical or solely Cartesian degrees of freedom. However, for manipulators having a mix of both rotational and translational degrees of freedom, i.e., complex degree of freedom manipulators, the condition number of the Jacobian matrix may not be used due to dimensional inconsistencies with its elements. This paper furthers earlier work introduced in obtaining a Jacobian matrix which may be used to determine the dexterity of parallel mechanisms regardless of the number and type of degrees of freedom of the mechanism. The result of the method introduced in this paper is a dimensionally homogeneous Jacobian matrix mapping m actuator velocities to n independent end effector velocities. In the typical case where m = n, the Jacobian matrix is also square. As opposed to earlier works, the singular values of the Jacobian matrix obtained here have an evident physical significance. Furthermore, the ratio of the maximum and minimum singular values, i.e., the condition number may be used to measure the dexterity of the manipulator at a given pose. To illustrate the concepts introduced in this paper, the 3-PRS manipulator is analyzed.     

新型激光切割并联机床的工作空间研究

提出了一种新型激光切割并联机床.在其位置逆解的基础上,通过边界搜索法获得了并联机床的工作空间,探讨了其结构参数对工作空间的影响.最后研究了并联机床的灵活性.研究表明该机床具有较大的工作空间且在有效的工作空间内不产生奇异,是一种理想的应用于激光切割的并联机床.     

基于灵巧特性的三平动并联机构的尺度综合研究

考虑机构的灵巧性提出一种新型3-PUU并联机器人,对该并联机构进行运动学分析,得到了3-PUU并联机器人的运动学反解,在此基础上,建立了并联机构的雅可比矩阵;引入运动灵巧性指标。对该并联机器人的运动灵巧性进行了尺度综合分析,为并联机构的构型设计和进一步提供了依据。研究结果表明,该种机器人具有较好的实际应用前景。     

3－TRS型关联机器人的几何特性分析

本文根据３－ＴＲＳ型机器人的结构特点，分析了它的工作空间，灵活性，奇异位形等几何特性。     

Kinematic Analysis and Application Research on a High-Speed Travelling Double Four-Rod Spatial Parallel Mechanism

In view of the existing problems of parallel mechanisms, and in order to meet the requirements of developing a new generation of high-speed virtual axis machine tools with a large working space, a novel high-speed travelling double four-rod spatial parallel mechanism is presented. The kernel issues are studied and related solutions are given to the key problems, such as forward and inverse kinematics and dexterity calculation. Computer simulation has been carried out to verify the correctness of the theoretical analysis. As an application example, a new type of five-coordinate robotic machine tool is introduced that is made based on this parallel mechanism. Theoretical analysis and application research show that the new mechanism has the advantages of long travel, large rotating angles and high moving speed, giving it a good prospect of application.     

5-UPS/PRPU五自由度并联机床基准位形的确定

确定了5-UPS/PRPU五自由度并联机床的刀尖点的空间搜索范围,计算出该搜索范围内动平台的位姿,将这些动平台位姿进行几何约束条件的检验,通过对满足几何约束条件的动平台位姿的雅可比矩阵的3个灵巧度指标分析,以综合误差系数为机床性能评价指标,搜索出并联机床的基准位形,为并联机床工件坐标系定位算法的研究提供了理论基础。