Influence of simultaneous bilateral exertion on muscle strength during voluntary submaximal isometric contraction

The influence of simultaneous bilateral exertion on muscle strength was tested under the conditions in which the same or different levels of strength were exerted by the right and left arm (or hand). Isometric muscle strength of elbow flexion, elbow extension and hand grip was studied. Subjects voluntarily exerted 25%, 50% and 75% of maximal strength based on their subjective judgement without the feedback of the strength actually exerted. Involuntary decrements of muscle strength were caused by the bilateral exertion. Muscle strength of both sides decreased under the condition where the same level of strength was exerted by the right and the left arm (or hand). When different levels of strength were exerted by each arm (or hand), the strength of the weaker side considerably decreased, while the strength of the stronger side did not decrease.     

Reproducibility of subjectively graded voluntary isometric muscle strength in unilateral and simultaneous bilateral exertion

Reproduction error of voluntary isometric muscle strength that was graded subjectively by the subject was investigated under unilateral and bilateral conditions. Six kinds of tasks, i.e. elbow flexion, elbow extension, hand grip, second digit abduction, knee extension and leg extension were employed. It was clear that absolute error (AE) increased with increase of exerted muscle strength in both unilateral and bilateral conditions. Mean of AE in each task was 4-5% of maximal muscle strength in the task in unilateral conditions. Algebraic or constant error (CE) decreased with increase of exerted strength. Demands for smaller strength tended to overshoot and larger ones tended to undershoot. In bilateral conditions when the different levels of strength for each limb were required to be exerted, AE on the weaker side tended to be larger than that in unilateral conditions. Thus a possibility that magnitude of AE might be affected by amount of attention was suggested. The subjectively graded criterion strength for a specific required level, when the strength was expressed as relative to the maximal strength, was almost the same in every task within a subject although it was different between subjects. It is suggested that each subject might have an awareness of relative magnitude of exerted strength.     

The influence of physical fitness training on the manual material handling capability of women

This study examined the influence of a generalized physical fitness training program on manual material handling (MMH) capability. Thirteen healthy women trained for 14 weeks, performing progressive resistance training three days per week and running with interval training two days per week. Subjects attended 85 ± 6% of the sessions. Compared to values obtained before training, subjects increased the maximum mass they could lift from floor to knuckle height by 19% (68–81 kg, p < 0.001) and from floor to chest height by 16% (49–57 kg, p < 0.001). They improved by 17% their ability to lift 15kg as many times as possible in 10 min(167–195 lifts, p < 0.001), while perception of effort (measured with the Borg Rating of Perceived Exertion) did not change. Total body mass did not change, but body fat mass was reduced by 9% (18.8–17.2 kg, p = 0.036) and fat-free mass increased by 6% (48.2–51.0 kg, p < 0.001). A short-term physical fitness program, conducted about 1 h per day, five days per week, can substantially improve women's MMH capability and provide favorable changes in body composition (increased fat-free mass and decreased body fat).     

Vector representations of human strength in whole body exertion

This paper summarises a number of studies of human strength in tasks of static whole body exertion. Measurements were made using a transducer bar which allowed the simultaneous recording of the vertical and horizontal components of any force applied to it by the subject. In each experimental condition, each subject exerted his or herself in all directions in the sagittal plane (ie, that plane which bisects an individual in the antero-posterior direction). Thirty conditions were investigated. Five heights of the bar above the ground, ranging from 1.75 m to 0.25 m, were tested. Various constraints were imposed upon the placement of the subjects' feet. In some conditions a 'ceiling' or 'wall' confined the subject. The results are presented in the form of diagrams which show the magnitude and direction of all possible force vectors in the sagittal plane.     

Anthropometric,muscle strength,and spinal mobility characteristics as predictors in the rating of acceptable loads in parcel sorting

The rating of acceptable load (RAL) attained with a standard test (RAL_st) and a work-simulating test (RAL_w) for postal parcel sorting was related to anthropometric, muscle strength, and spinal mobility characteristics of 18 male sorters. The subjects comprised a subsample of 103 experienced male sorters who carried out the RAL tests at postal sorting centres. The dynamic hand-grip endurance correlated significantly (p=0·036) to the RAL_st results. Correspondingly, there was a significant correlation ( p=0·044) between the ratio of maximal isometric strength of trunk extension to body weight and the RAL_w. The dynamic hand-grip endurance predicted 26% of the variation in the RAL_st; in the RAL_w the maximal isometric strength of trunk flexion to body weight ratio predicted 24%. The subjects who rated heavier weights for RAL_st, tended to have a better trunk mobility. The dynamic endurance of hand-grip muscles, trunk strength, and spinal flexibility seemed to be the most powerful predictors for the psychophysically assessed ‘acceptable loads’ in experienced workers performing manual materials handling tasks.     

A three-dimensional computerized isometric strength measurement system

The three-dimensional Computerized Isometric Strength Measurement System (CISMS) reliably and accurately measures isometric pull and push strengths in work spaces of paraplegic populations while anticipating comparative studies with other populations. The main elements of the system were: an extendable arm, a vertical supporting track, a rotating platform, a force transducer, stability sensors and a computerized data collection interface. The CISMS with minor modification was successfully used to measure isometric push-up and pull-down strengths of paraplegics and isometric push, pull, push-up and pull-down strength in work spaces for seated and standing able-bodied populations. The instrument has satisfied criteria of versatility, safety and comfort, ease of operation, and durability. Results are accurate within 2N for aligned forces. Costing approximately $1,500 (US) including computer, the system is affordable and accurate for aligned isometric strength measurements.     

One-handed dynamic pulling strength with special reference to speed, handle height and angles of pulling

A laboratory study was conducted to determine the effects of pulling speed, handle height and angle of pull from the horizontal plane on one-handed dynamic pulling strength. The dynamic strength of nineteen male subjects for a 1 m pull was measured at four different handle heights (40%, 50%, 60% and 70% of shoulder height), at three different angles above the horizontal plane (15°, 25° and 35°), and at three different speeds of pulling (mean speed = 0.7, 1 and 1.1 ms⁻¹). In addition, ratings of perceived exertion were recorded for elbow, shoulder and back. Also, the subjects were required to rate the overall comfort for the pull.

Pulling speed, handle height and angle all had a significant effect on both mean and peak dynamic pulling strengths (p 0.01). Among the three variables, pulling speed was found to be the most critical. The mean dynamic strength was 360, 250 and 180 N and the peak strength was 600, 425 and 320 N at 0.7, 1 and 1.1 ms⁻¹, respectively. The strengths decreased with an increase in handle height from 100% at 40% shoulder height to 83% at 70% of shoulder height and were the highest at an angle of 25° from the horizontal plane.

The ratings of perceived exertion for all three body parts decreased with an increase in speed of pulling (p 0.01). The high speed pulls were perceived as being more comfortable than low speed pulls (p 0.01). The handles at 50% and 60% of shoulder height and at an angle of 25° were perceived as being more comfortable than those at other heights and angles (p 0.01).

It is suggested that biomechanical stresses need to be considered along with physical strength and ratings of perceived exertion and comfort to determine optimum speed, height and angle of pulling for high speed pulling tasks.     

基于力控与ADAM模块的电机温升计算机监控系统

利用力控组态软件与研华ADAM5000E与ADAM5018模块开发电机堵转温升计算机监控系统,详细介绍了该控制系统结构、监控系统的SQL转储功能和网络发表功能及上/下位机的参数设置等。该系统投运结果表明,达到了规定的设计性能指标和要求。     

基于人体肌肉力量的数据分析系统的设计

论文将计算机技术应用到运动生物力学的研究中,提出并实现了针对人体肌肉力量中握力、背力的实时数据采集与分析系统。系统采用运动生物力学测量装置精确采集肌肉力量的数据,利用数据库技术存储和处理测量的数据,图形化显示肌肉力量的变化曲线,计算人体肌肉力量的多种参数,对肌肉力量进行综合分析比较。文中着重介绍了系统结构、功能及软件实现。     

转子凸极效应对同步电动机矢量控制的影响研究

本文在气隙合成磁链矢量旋转坐标系上,研究了转子凸极效应对同步电动机矢量控制的影响．严格的数学分析、推导和仿真结果表明,由于凸极同步电动机气隙不均匀,转子纵横轴磁路不对称,以气隙合成磁链矢量定向的旋转坐标系并不能使同步电动机的控制解耦．此外还首次得出考虑转子凸极效应后的同步电动机矢量控制数学表达式,并讨论了不解耦性对转子阻尼绕组的影响．     

主干线协调控制的改进算法研究

为改善传统主干线协调控制方法中存在的问题,对传统主干线协调控制算法进行了深入的研究和改进。改进算法为有效提高绿时利用率,减小车辆延误,对单路口实施了改进的模糊控制算法;同时,对主干线上车辆到来情况进行实时检测,若有大规模车队到来,则中断模糊控制器,即时疏散车队,从而实现对主干线的实时协调控制。将此算法应用于城市主干道交通协调控制,对减小整个主干线的停车延误和排队延误有很好效果,并且对路况变化具有较强的鲁棒性,适合在大中城市中推广。     

垂直姿态的非正交测量优化与校正

垂直小角度时,采用的非正交姿态测量方法旨在解决传感器输出信号极微弱和解算精度低等问题。描述了非正交坐标系的理论模型,对其进行了优化,确定了最佳偏置角度。利用补偿矩阵对因测斜仪安装问题引入的位置误差进行校正,通过井斜角和工具面角的解算结果验证校正效果。测试结果表明,在偏置角为45°时,姿态参数具有较高的解算精度;而数据校正能大幅度降低位置误差,进一步提高测量精度。     

超声电机测控系统的一种实现方法

设计了一套基于微机的超声电机速度和位置测试与控制系统.该系统解决了超声电机长时间工作时由于压电陶瓷特性的改变导致电机速度不稳定问题,采用PI算法的闭环控制时,电机速度可以稳定在3%之内.位置控制实验结果表明:采用模糊推理 PI控制器对电机进行位置精密伺服控制是完全可行的,精度可以达到0.09°.     

On the addition of integral action to port-controlled Hamiltonian systems

A technique that provides closed loop integral action depending on the passive outputs of port-controlled Hamiltonian systems is already available. This paper addresses a new method that allows us to add integral action also on system variables having relative degree higher than one, while still preserving the Hamiltonian form and, thus, closed loop stability. The new approach is applied to design speed regulation controllers for the permanent magnet synchronous motor. Closed loop stability and asymptotic rejection of unknown piecewise constant load torques are formally proved. This theoretically predicted control system performance is illustrated via simulation experiments, which also show that the properties hold under parameter uncertainties. This is in line with the usual practice of including integral action in a controller with the aim of improving its closed loop robustness. The fact that the method enhances the range of possible integral actions in the controller, enriched with this robustness property, allows us to assess it as a practically important complement to the well-known interconnection and damping assignment techniques developed in the framework of port-controlled Hamiltonian systems.     

永磁同步电机系统在电动叉车上的应用

电动叉车驱动电机及其控制系统一直是国内外各大叉车制造公司研究的热点,文中简单介绍了一种电动叉车用永磁同步电机及其控制系统的功能、特点和技术参数,并与直流电机系统做了比较。     

无刷直流电动机换相控制的研究

无刷直流电动机在运行中，由于受到电磁干扰、负载扰动等因素的影响，换相脉冲发生畸变或混有尖峰，由此带来换相抖动或抗负载扰动能力变差。针对这一问题，通过对换相信号的分析找到了换相抖动的原因，并提出了根据换相时间间隔延时屏蔽换相中断来消除换相抖动的方法：中断延时屏蔽换相法：实验证明该方法行之有效，尤其适用于在平均负载较轻、负载抖动较大以及电磁干扰较大情况下无刷直流电动机的换相控制。     

热连轧生产线卷取机控制技术的创新

介绍唐山国丰钢铁有限公司2#1450热连轧全液压地下卷取机自动控制系统的创新点。     

嵌入式系统的多路步进电机控制系统的设计

本文设计实现了一种三路步进电机控制系统,它基于RT Thread嵌入式实时系统,提高了系统的实时性和后期的功能扩展能力.系统控制电路采用STM32 F4系列的微控制器,结合小功率步进电机驱动器A4988,完成了硬件电路板设计.软件中运用操作系统自带的finsh机制,实现对指令的初步解析,控制系统可以通过读取G指令,控制多路电机按照一定轨迹运动,同时可以调节电机运动的加减速参数.实际项目验证证明该系统具有很好的稳定性.     

真空变化对火电机组协调控制策略修正方法的研究及实现

真空是机组运行监视的主要参数之一,它关系到机组的安垒运行,决定了机组的理想焓降、发电效率和出力能力.在以往的机组控制中,仅把真空作为机组的保护参数,而没有将真空变化对控制参数的影响考虑在内,使得机组在真空不同时控制调节品质相差较多.本文介绍了通过试验方法获取真空改变对机组运行状态的影响数据,增加协调控制中对真空的修正部分达到控制优化目的试验过程.