Determination method for power-saved driving motions of manipulators by heuristic algorithms (in case of PTP control)

This study proposed a method for suppressing torques and consumed energy of manipulators considering an effect of inertial forces in order to achieve power-saved drive. The present paper describes the case that the start and end points of a work path of a manipulator are specified and the path between the points can be determined arbitrarily, which is so-called point-to-point (PTP) control. The proposed method determines both the initial pose of a manipulator and input motions of its joints so that the torque or consumed energy is suppressed. The input motion of the joint is expressed by a motion curve that indicates the time profiles of input displacements, velocities and accelerations. The proposed method determines the motion curve as a polynomial with appropriate coefficients. Those coefficients and their values are decided by a heuristic algorithm in order to suppress the input torques or consumed energy of a manipulator. The paper actually determines the power-saved drive motion of “PUMA560” by the proposed method and reveals its effectiveness.     

对不同项目运动员躯体肌力的等动测试研究

用Cybex 6000以60°/sec的速度对柔道、体操和排球项目的36名优秀运动员躯干肌力进行了较为系统的等动测量与评价。结果表明,不同项目的运动员,躯干肌肉的生物力学特征是不同的。     

优秀女子短道速度滑冰运动员下肢肌力特征及与500米成绩的回归分析

摘要：目的：探讨短道速度滑冰运动员下肢肌力特征以及与500米成绩的回归分析,增强训练的优化性和对项目规律的认识。方法：运用ISOMED 2000多关节等速测力系统对我国10名女子短道速度滑冰国家队队员膝、踝关节肌肉力量进行测试。结果：1）相对峰力矩和总功指标角随速度增加而下降,各速度间呈显著性差异;而膝、踝关节屈伸比指标低于国际和国内标准;运动员的膝关节爆发能力较好,踝关节在高速度下表现不足。2）左右腿同名肌群除膝关节屈伸比、踝关节平均功率两项指标,均呈显著性差异（p<0.05）,多个指标超过10%的推荐值膝关节差值在4.5%～12.9%之间,踝关节差值在5.5%～14.5%之间。3）膝伸肌群峰力矩角度（240°/s）、膝屈肌群相对峰力矩（240°/s）和膝伸肌群平均功率（180°/s）3组指标进入与500 m成绩的逐步回归方程,相关系数为0.94,决定系数为0.90,方差检验p<0.05,方程有效。结论：优秀女子短道运动员下肢膝、踝关节屈伸力量符合生物力学特征,对于短道速度滑冰项目高速度区比低速度区的力量能力更重要,膝关节肌群相对踝关节在500 m项目中起到更大作用,短道运动员的膝、踝屈伸肌群比例较低,或具有项目特点,与技术相关的力量指标与成绩的相关性更高,训练中应加强两腿同名肌群力量的平衡性,减少由于肌群不平衡所引起的伤病和技术缺陷。     

立定跳远落地姿态的合理性

对30名受试者正常和“外八”两种落地姿态立定跳远成绩、走路步向角、踝关节内收、外展等动肌力测试,探讨“外八”姿态落地对立定跳远成绩的影响。结果发现：与正常姿态落地相比,立定跳远采用“外八”姿态落地对落地后身体稳定性的影响差异不具显著性;两种落地姿态的立定跳远成绩差异没有显著性;采用外八字姿态落地,50%(男8人,女7人)成绩下降,幅度为0.05 m,33.3%(男4人,女6人)成绩上升,幅度为0.07 m,百分率和升降幅度差异均不具显著性;采用外八字姿态落地立定跳远成绩升降幅度与步向角,踝关节快、慢速外展最大幅度均中等程度相关(P<0.05)。结果说明：与正常落地姿态相比,外八字落地姿态立定跳远的成绩升或降因人而异,与受试者步向角,踝关节快、慢速外展的最大幅度呈中等程度相关,步向角越小,踝关节外展最大幅度越大,采用外八字姿态落地立定跳远的成绩提高的几率越大。     

地面煤流201G皮带机改造方案

文章对地面煤流系统进行了改造,并提出了皮带机改造的方案及对策,对提高皮带机系统的可靠性,保证矿井安全、经济、稳定运行有重要的参考价值。     

临吹门控制方式改进

在电源点新建项目中,必须对锅炉过热汽,再热汽等管道进行蒸汽吹扫,已达到国家标准要求及机组运行要求,从而较好的保护机组设备。临吹门就是控制蒸汽吹扫过程的主要设备。这就要求临吹门具有较高的可靠性,动作灵活,控制方式安全、可靠,以适应吹管过程中的恶劣环境,保证吹管过程安全可靠的进行。     

Acute effects of static stretching on characteristics of the isokinetic angle – torque relationship,surface electromyography,and mechanomyography

Abstract

The aims of this study were to examine the acute effects of static stretching on peak torque, work, the joint angle at peak torque, acceleration time, isokinetic range of motion, mechanomyographic amplitude, and electromyographic amplitude of the rectus femoris during maximal concentric isokinetic leg extensions at 1.04 and 5.23 rad · s^?1 in men and women. Ten women (mean ± s: age 23.0 ± 2.9 years, stature 1.61 ± 0.12 m, mass 63.3 ± 9.9 kg) and eight men (age 21.4 ± 3.0 years, stature 1.83 ± 0.11 m, mass 83.1 ± 15.2 kg) performed maximal voluntary concentric isokinetic leg extensions at 1.04 and 5.23 rad · s^?1. Following the initial isokinetic tests, the dominant leg extensors were stretched using four static stretching exercises. After the stretching, the isokinetic tests were repeated. Peak torque, acceleration time, and electromyographic amplitude decreased (P≤ 0.05) from pre- to post-stretching at 1.04 and 5.23 rad · s^?1; there were no changes (P > 0.05) in work, joint angle at peak torque, isokinetic range of motion, or mechanomyographic amplitude. These findings indicate no stretching-related changes in the area under the angle – torque curve (work), but a significant decrease in peak torque, which suggests that static stretching may cause a “flattening” of the angle – torque curve that reduces peak strength but allows for greater force production at other joint angles. These findings, in conjunction with the increased limb acceleration rates (decreased acceleration time) observed in the present study, provide tentative support for the hypothesis that static stretching alters the angle – torque relationship and/or sarcomere shortening velocity.     

Determining the minimum number of passive stretches necessary to alter musculotendinous stiffness

Abstract

In this study, we examined the minimum number of constant-torque passive stretches necessary to reduce musculotendinous stiffness. Thirteen healthy individuals (mean age 22 years, s = 3; stature 1.67 m, s = 0.1; mass 66 kg, s = 13 kg) volunteered to participate in the investigation and underwent four 30-s constant-torque passive stretches of the plantar flexor muscles. Musculotendinous stiffness was examined from the angle–torque curves generated prior to the passive stretches, at the beginning of each 30-s stretch, and immediately following the four 30-s passive stretches. The results indicated that musculotendinous stiffness of the plantar flexors was reduced following two 30-s constant-torque passive stretches (P < 0.05) compared with the pre- musculotendinous stiffness assessment. Musculotendinous stiffness remained depressed following the third and fourth stretches, but did not decrease further. These findings suggest that two 30-s bouts of constant-torque passive stretching may be necessary to cause a significant decrease in musculotendinous stiffness of the plantar flexor muscles.     

Size–strength relationships of the elbow flexors and extensors are not affected by age or gender

Abstract

In the present study, we examined the relationships between muscle volume and joint torque for the elbow flexors and extensors in young and elderly individuals, with the aim of evaluating age effects on these relationships. The participants were 45 young (27 men and 18 women aged 20–37 years) and 51 elderly (19 men and 32 women aged 60–77 years) individuals. The joint torques developed during isometric maximal voluntary elbow flexion and extension were measured using a torque meter. The muscle volumes of the elbow flexors and extensors were determined by magnetic resonance imaging. For the elbow flexors, joint torque was significantly correlated with muscle volume in both young and elderly individuals (r=0.564–0.872). There were also significant correlations between muscle volume and joint torque for the elbow extensors in elderly men and women as well as in young men and women (r=0.715–0.826). None of the y-intercepts of the regression lines between muscle volume and joint torque were significantly different from zero. Furthermore, no significant age or gender effects on the joint torque per muscle volume of the elbow flexors and extensors were observed. The present results suggest that muscle volume is a main determinant of joint torque regardless of age and gender, for both muscle groups.     

Does a water-training macrocycle really create imbalances in swimmers' shoulder rotator muscles?

Abstract

The continuous execution of swimming techniques may cause muscle imbalances in shoulder rotators leading to injury. However, there is a lack of published research studies on this topic. The aim of this study was to analyze the influence of a competitive swim period on the shoulder rotator–cuff balance in young swimmers. A randomized controlled pretest–posttest design was used, with two measurements performed during the first macrocycle of the swimming season (baseline and 16 weeks). Twenty-seven young male swimmers (experimental group) and 22 male students who were not involved in swim training (control group) with the same characteristics were evaluated. Peak torque of shoulder internal and external rotators was assessed. Concentric action at 1.04 rad s^?1 (3 repetitions) and 3.14 rad s^?1 (20 repetitions) was measured using an isokinetic dynamometer (Biodex System 3). External/internal rotators strength ratios were also obtained. For both protocols, there were significant training effects on internal rotator strength and external/internal rotator ratios (p ≤ .05). This trend was the same for both shoulders. Within-group analysis showed significant changes from baseline to 16 weeks for internal rotators strength and unilateral ratios of the experimental group. Swimmers' internal rotator strength levels increased significantly. In contrast, a significant decrease of the unilateral ratios was observed. Findings suggest that a competitive swim macrocycle leads to an increase in muscular imbalances in the shoulder rotators of young competitive swimmers. Swimming coaches should consider implementing a compensatory strength-training program.