提高无刷直流电动机负载能力的策略与实现

高速条件下 ,无刷直流电动机的电流换向产生严重滞后 ,导致转矩下降并伴随脉动 .采用超前导通控制法 ,可有效加快换向过程 ,改善转矩输出能力 ;并采用改进的黄金分割法寻优 ,在线调整最优超前导通角 .仿真与实验结果验证了该控制方案的可行性与有效性     

基于小波神经网络的定子电阻在线辨识的研究

电机定子电阻的变化影响了直接转矩控制系统的低速性能.定子电阻的变化具有非线性、时变性等特点,难以建立精确的数学模型,因此提出了基于小波神经网络的定子电阻线辨识的方案,该网络采用梯度下降算法训练,可用于对定子电阻进行在线的辨识.仿真实验测试结果表明该辨识器能够精确辨识定子电阻值,从而有效地改善了直接转矩控制系统的低速性能.     

一种无石棉纸基摩擦材料的摩擦磨损性能研究

采用湿法工艺研制了一种无石棉纸基摩擦材料，应用QM1000-Ⅱ型摩擦材料性能试验机研究了摩擦力矩特征和摩擦磨损性能。试验结果显示，新研制的无石棉纸基摩擦材料的动摩擦系数高、静／动摩擦系数适中，是一种适合于汽车自动变速器的纸基摩擦材料．具有作为汽车用摩擦材料的潜在应用前景。     

摩擦补偿下基于关节力矩的笛卡尔阻抗控制

为了研究基于关节力矩信息的笛卡尔阻抗控制策略及摩擦补偿的影响,利用关节本身具有的传感器,进行了辨识谐波驱动摩擦参数、摩擦补偿和笛卡尔阻抗控制的实验研究．与传统的基于机器人末端力／力矩信息的笛卡尔阻抗控制方案不同,考虑了5种基于关节力矩的笛卡尔阻抗控制方案,包括笛卡尔空间／关节空间基于力的、笛卡尔空间／关节空间基于位置的方案和刚度控制．其中,前4种方案分别在有／无摩擦补偿的条件下进行了相应的实验验证．实验比较结果表明：对于基于关节力矩信息来实现笛卡尔阻抗控制的机器人,基于力的阻抗控制策略比基于位置的策略更适合,并且摩擦对这类笛卡尔阻抗控制的稳定性有积极影响．     

Effects of fast-velocity eccentric resistance training on early and late rate of force development

This study examined whether short-term maximal resistance training employing fast-velocity eccentric knee extensor actions would induce improvements in maximal isometric torque and rate of force development (RFD) at early (<100 ms) and late phases (>100 ms) of rising torque. Twenty healthy men were assigned to two experimental groups: eccentric resistance training (TG) or control (CG). Participants on the TG trained three days a week for a total of eight weeks. Training consisted of maximal unilateral eccentric knee extensors actions performed at 180°s-1. Maximal isometric knee extensor torque (MVC) and incremental RFD in successive 50 ms time-windows from the onset contraction were analysed in absolute terms (RFD_INC) or when normalised relative to MVC (RFD_REL). After eight weeks, TG demonstrated increases in MVC (28%), RFD_INC (0–50 ms: 30%; 50–100 ms: 31%) and RFD_REL (0–50 ms: 29%; 50–100 ms: 32%). Moreover, no changes in the late phase of incremental RFD were observed in TG. No changes were found in the CG. In summary, we have demonstrated, in active individuals, that a short period of resistance training performed with eccentric fast-velocity isokinetic muscle contractions is able to enhance RFD_INC and RFD_REL obtained at the early phase of rising joint torque.     

Isokinetic imbalance of adductor–abductor hip muscles in professional soccer players with chronic adductor-related groin pain

This study aims to compare the isokinetic profile of hip abductor and adductor muscle groups between soccer players suffering from chronic adductor-related groin pain (ARGP), soccer players without ARGP and healthy volunteers from general population. Study included 36 male professional soccer players, who were randomly selected and followed-up over two years. Of the 21 soccer players eligible to participate in the study, 9 players went on to develop chronic ARGP and 12 players did not. Ten healthy male volunteers were randomly selected from the general population as a control group. Comparison between the abductor and adductor muscle peak torques for players with and without chronic ARGP found a statistically significant difference on the dominant and non-dominant sides (p?p?p?=?.008). The adductor muscle strength was also significantly decreased on the affected side. This imbalance appears to be a risk factor for adductor-related groin injury. Therefore, restoring the correct relationship between these two agonist and antagonist hip muscles may be an important preventative measure that should be a primary concern of training and rehabilitation programmes.     

三相变频调速异步电动机设计与分析

分析由变频器供电的变频调速异步电动机气隙磁势，讨论恒转矩负载时三相变频调速异步电动机特性，结合研制的2极、功率3．5～4．5kW、频率80～100Hz变频调速木工同异步电动机样机的实测结果，阐述恒转矩负载时设计特点。     

基于多传感器信息融合的旋转机械扭矩测量

为提高旋转动力机械扭矩测量的精度和可靠性,基于多传感器信息融合技术,研制1套旋转机械扭矩遥测系统.该系统结构简单、可靠性好、测试精度高.     

Kinematics and kinetics of youth baseball pitching with standard and lightweight balls

Because youth athletes are smaller and weaker than their adult counterparts, smaller equipment and fields are often used in youth sports. Previous research has shown that youth baseball pitchers use similar motions to older pitchers, but generate lower kinetics and angular velocities at the shoulder and elbow. The purpose of this study was to determine potential biomechanical benefits for youth pitchers to use lighter baseballs. Thirty-four youth (11.1 ± 0.7 years) pitchers pitched both standard [5 ounce (142 g)] and lightweight [4 ounce(113 g)] baseballs in a laboratory setting. Kinematic and kinetic parameters were measured with a six-camera high-speed motion analysis system. Three repeated measures MANOVAs were used to compare (p > 0.05) position, velocity, and kinetic parameters between the standard and lightweight baseballs. Subjective data were also collected. Pitching the lightweight ball produced no difference in arm position, but greater shoulder, elbow, and ball velocities. With the lightweight ball, pitchers produced decreased kinetics.Post-hoc analysis of the kinetic data revealed significant decreases in elbow varus torque and shoulder internal rotation torque. The data suggest that playing with lightweight baseballs may reduce the risk of overuse injury in the youth pitcher and also help develop arm speed. However, before introducing lightweight baseballs into the youth game, the effect of lighter, faster pitched balls for the batters and fielders should also be considered.     

Gender Differences in Strength

The purpose of this study was to examine gender differences in upper and lower body strength as a function of lean body weight and the distribution of muscle and subcutaneous fat in the upper and lower limbs. The subjects were 103 physically active men (n = 48) and women (n = 55). The peak torques produced during shoulder flexion (SF) and knee extension (KE) were used as measures of upper body and lower body strength, respectively. Flexed arm girth, thigh girth, triceps skinfold, and thigh skinfold were used to estimate the distribution of muscle and subcutaneous fat in the limbs. Results of the MANOVA revealed that the overall strength of men was significantly greater than that of women. Results of MANCOVA indicated that the SF and KE strength of women and men did not differ significantly when differences in lean body weight, arm girth, thigh girth, triceps skinfold and thigh skinfold were statistically controlled. High levels of SF and KE strength were associated with a high lean body weight and a large arm girth. Results of the multiple regression analysis indicated that for men a substantial portion of the variance in both SF and KE strength was explained by lean body weight alone; whereas strength variations in women were explained more adequately by including limb variables along with lean body weight. Within the limitations of this study, it was concluded that gender differences in upper and lower body strength are a function of differences in lean body weight and the distribution of muscle and subcutaneous fat in the body segments. Upper body strength is relatively more important than lower body strength in characterizing the gender difference in strength.