Muscle forces analysis in the shoulder mechanism during wheelchair propulsion

This study combines an ergometric wheelchair, a six-camera video motion capture system and a prototype computer graphics based musculoskeletal model (CGMM) to predict shoulder joint loading, muscle contraction force per muscle and the sequence of muscular actions during wheelchair propulsion, and also to provide an animated computer graphics model of the relative interactions. Five healthy male subjects with no history of upper extremity injury participated. A conventional manual wheelchair was equipped with a six-component load cell to collect three-dimensional forces and moments experienced by the wheel, allowing real-time measurement of hand/rim force applied by subjects during normal wheelchair operation. An ExpertVision six-camera video motion capture system collected trajectory data of markers attached on anatomical positions. The CGMM was used to simulate and animate muscle action by using an optimization technique combining observed muscular motions with physiological constraints to estimate muscle contraction forces during wheelchair propulsion. The CGMM provides results that satisfactorily match the predictions of previous work, disregarding minor differences which presumably result from differing experimental conditions, measurement technologies and subjects. Specifically, the CGMM shows that the supraspinatus, infraspinatus, anterior deltoid, pectoralis major and biceps long head are the prime movers during the propulsion phase. The middle and posterior deltoid and supraspinatus muscles are responsible for arm return during the recovery phase. CGMM modelling shows that the rotator cuff and pectoralis major play an important role during wheelchair propulsion, confirming the known risk of injury for these muscles during wheelchair propulsion. The CGMM successfully transforms six-camera video motion capture data into a technically useful and visually interesting animated video model of the shoulder musculoskeletal system. The CGMM further yields accurate estimates of muscular forces during motion, indicating that this prototype modelling and analysis technique will aid in study, analysis and therapy of the mechanics and underlying pathomechanics involved in various musculoskeletal overuse syndromes.     

一种椭圆轮式轮椅爬楼梯辅助装置的设计

设计了一款椭圆轮式轮椅爬楼梯辅助装置,通过锁止轮毂与普通轮椅底架固定连接并套在其轮轴上。采用胎面装附有牙型花纹的防滑橡胶皮的椭圆轮爬楼和越障,装置使用马达作动力。同时对椭圆轮的特性和椭圆轮在台阶上的运动轨迹做了相应的说明。经过性能分析,设计的轮椅爬楼梯辅助装置满足功能要求,并具有爬楼梯安全稳定、操作简单、方便控制等特点。     

车轮多边形对高速列车车轴疲劳强度影响研究

车轮多边形是铁道车辆一种常见的非圆化病害,对轮对振动和车辆运行安全有明显的影响。在建立刚柔耦合拖车和动车车辆系统动力学模型基础上,将车轮多边形简化为简谐波并将其考虑为车轮轮径的变化,研究20阶车轮多边形对拖车和动车车轴疲劳强度的影响。结果表明,等效应力幅比值与速度呈非线性关系,且拖车和动车峰值出现位置有所不同,拖车峰值位置出现在速度为225 km/h,对应多边形激励频率432.7 Hz;动车不同截面分别在300 km/h、375 km/h时存在峰值,对应多边形激励频率分别为576.5Hz、721.2Hz。在各峰值位置处,多边形幅值的变化对拖车和动车部分截面的等效应力幅比值均有显著影响。拖车和动车车轴等效应力最大值均位于C截面,并且随着车轮多边形幅值的增加,其等效应力显著增大,超过车轴疲劳强度限值,降低车轴使用寿命。研究结果有助于改善20阶车轮多边形对高速列车车轴疲劳强度及弹性振动的影响。     

某炼钢厂100t渣车车轮轴频断裂原因分析

某炼钢厂100t渣车在使用过程中,出现车轮轴频繁断裂问题。从渣车车轮轴结构出发,计算车轮轴的受力情况,并综合分析设计制造环节等方面因素,总结了最终导致车轮轴在工作中频繁断裂的原因,对于改进渣车车轮轴的设计制造提供了一定的参考。     

轮力传感器及其在汽车道路试验中的应用

汽车轮力传感器串接在轮胎轮辋和车桥轮毂之间，用于在汽车实车道路试验和室内台架试验时测量由地面或激振器作用于轮胎的六分力。轮力传感器研制的关键技术包括可靠且准确的信号和能量传输、信号的解耦、强度和结构安装要求等。详细介绍了轮力传感器的研究进展、设计原理、性能评价和误差分析等，最后对其在汽车道路试验中的具体应用做了介绍。     

超轻型牵引火炮高平机优化设计研究

手轮力大小是评价高平机性能好坏的重要标准,而不平衡力矩是决定手轮力的重要因素。针对某超轻型牵引火炮的结构布置特点,研究了其螺杆式高平机工作原理,提出一种基于多岛遗传算法(MIGA)的高平机设计方法,建立以整个射角范围内的最大不平衡力矩为目标函数的优化模型,对结构参数进行优化匹配。结果表明:该方法相对于传统的设计方法,可以有效地降低最大不平衡力矩,改善设计水平,对今后研制火炮高平机具有指导意义。     

FANUC 0i C系列CNC数控机床手轮故障处理

针对数控车床的手轮移动操作方式进行研究。重点论述手轮进给的步骤,主要有手摇开关选择;手轮进给轴选择,选择一个机床要移动的轴;手轮进给率选择,选择机床移动的倍率;旋转手轮,机床沿选择轴移动。     

四轮并列式起落架焊接主起轮轴受载模型及分析

针对大飞机上常用的四轮并列式起落架,给出了飞机在着陆准稳态阶段,其起落架焊接主起轮轴的受载数学模型。以伊尔-76飞机为研究对象,采用有限元分析软件ANSYS,模拟了其机轮着陆过程中焊接主起轮轴受力状况。结果表明,主起轮轴上两道焊缝处应力最大,断裂几率最高,最先着陆机轮的轴颈处由于受到循环载荷作用,易发生疲劳断裂。     

不同类型CNC五轴工具磨床的运动参数转换原理

详细分析了CNC五轴立式砂轮平动工具磨床 (P型 )和砂轮摆动工具磨床 (B型 )的运动形式及其加工原理 ,并将之与传统机床进行了比较 ;从所要求的同一个几何参数刀具具有相同的几何本质出发 ,给出了P型和B型 2种类型CNC工具磨床的内在运动参数的转换关系。研究阐明了在刀具磨削成形的过程中 ,控制每个瞬时砂轮几何体和工件几何体在空间的相对位姿和相对运动趋势是精确成形的关键。     

Optimizing 4-bar crank-rocker mechanismOptimisation du mecanisme a quatre barres avec une manivelle et un balancier

Closed form equations are developed for the synthesis of the 4-bar crank-rocker mechanism in which the angle between dead-centre positions of the rocker and the corresponding angle turned by the crank are prescribed. All the four different situations are considered and the minimum transmission angle, for the complete rotation of the crank, is obtained for each case. The upper and lower bounds on the crank angle, corresponding to a dead centre position of the rocker, are obtained by using Grashof's criterion. The design is optimized by maximizing the minimum transmission angle. Each case is illustrated by providing a numerical example.     

齿轮减速器机械效率的自动测量

采用光电一弹性轴复合传感器，通过对弹性轴上相距为L的两截面上相对扭转角的测量，经过光电转换后测量传感器上输出电流的大小来测量减速器输入轴和输出轴的扭矩，从而测量减速器的动态机械效率。     

轮轴弯曲刚度对轮轨垂向动态载荷影响分析

以国内某型地铁车辆为例,研究轮轴弯曲刚度对轮轨垂向动态载荷和轮对垂向振动的影响。在常规多刚体动力学模型的基础上,结合BM3000轮对和北京地铁轮对两种不同的弹性轮对模型,对比分别采用刚性轮对模型和弹性轮对模型时的轮对垂向振动加速度和轮轨垂向力。结果表明,对BM3000弹性轮对模型来说,由于其弯曲刚度相对较小,随着运行速度的增大,轮对垂向振动加速度和轮轨力与刚性轮对的差距不断加大,而对于轮轴弯曲刚度较大的北京地铁轮对来说,其弹性轮对模型和刚性轮对模型的结果比较接近,在计算的速度下轮对的振动峰值及频率均有明显的降低。因而,通过加大轮轴弯曲刚度可明显改善轮对的垂向振动和轮轨垂向力,实现改善轮轨动态接触状态的目的。     

数控磨削回转面刀具时机床联动轴数的确定

根据回转面刀槽螺旋面的成形原理 ,阐释了回转面刀具数控磨削成形的过程实质上就是控制每一瞬时砂轮几何体与工件几何体在空间的相对位姿和相对运动趋势的过程 ;分析了砂轮平动型和砂轮摆动型CNC工具磨床的运动形式 ,讨论了机床联动轴数的确定原则并给出了计算实例     

水下捕捞机器人水动力学性能分析

海参捕捞机器人在水下捕捞作业时的性能受姿态变化的影响较大,为了使海参捕捞机器人始终保持最佳性能,需要在实际应用前对不同姿态下的捕捞机器人进行水动力学分析。利用计算流体力学软件 中的RNG 湍流模型作为仿真模型,考虑到仿真计算的精度,对近壁区域的处理进行了研究,在湍流模型的基础上加入了标准壁面函数。应用该模型对水下捕捞机器人水平直航、水平斜航和垂直斜航3种姿态下的水阻力和水阻力矩进行分析。结果表明:不同的姿态将影响水下捕捞机器人所受到的水阻力和水阻力矩的大小;在水平直航时捕捞机器人受到垂直向下的作用力较大,而产生的俯仰力矩较小;在水平斜航时漂角对捕捞机器人的影响较大;在垂直斜航时捕捞机器人的垂向力和俯仰力矩均随着流速和攻角的增大而增加。     

前桥轮毂拆卸专用拉具的结构设计

前桥轮毂拆卸是汽车修理中经常性的修理作业内容,针对汽车修理维修企业中不同车型前桥轮毂拆卸的修理实际需要,通过分析不同汽车前桥轮毂结构特点,设计了套筒式轮毂拆卸拉具和板条式轮毂拆卸拉具。套筒式轮毂拆卸拉具主要针对有前轮毂罩螺栓的前桥轮毂拆卸,板条式轮毂拆卸拉具主要解决没有前轮毂罩螺栓的前桥轮毂拆卸,板条式轮毂拆卸拉具刚性好,可满足重型车轮毂拆卸。两种设计能满足多种车型的轮毂结构的拆卸需要,有很好的通用性。     

A new derailment coefficient considering dynamic and geometrical effects of a single wheelset

A new derailment coefficient of a single wheelset was theoretically developed by considering the dynamic and geometric effects from lateral acceleration and gyro factors as well as mechanical factors like flange angle, frictional coefficient, wheel-unloading, wheel radius, track gauge and position of axle bearings. This new derailment coefficient (lateral force over vertical wheel load, P/Q) can predict the commencement of various derailments, such as wheel climbing and lifting types, roll-over types and their combined types. In addition, this derailment coefficient can analyze the various dynamic and geometrical effects of a wheelset, which are not considered in the conventional derailment coefficients of Nadal’s and Weinstock’s formulas. This derailment coefficient was verified by comparing its theoretical anticipations of several examples with numerical simulation results using a commercial dynamic S/W, RecurDyn.     

基于AutoCAD及Pro/E的天圆地方类结构件建模及展开研究

天圆地方类结构件精确三维建模一直是工程上的难点,以前的研究基本上是从各类三维软件的直接应用建立模型,缺点是不能精确建模。本研究基于天圆地方类结构件的表面特征进行精确建模,依据"曲面公共切平面定理",在椭圆锥面上求截面圆,此圆即是三维建模的平面基础,基于此截面圆利用AutoCAD及Pro/E等软件对其进行精确三维建模、获得实体。2D与3D作图有机结合,运用椭圆锥的截面圆性质求得椭圆锥实体,与四棱锥台进行并集运算获得天圆地方实体模型,为其CAD展开及更复杂的组合(相贯)件实体建模打下坚实的基础,同时,对其进行了精确的展开。     

轮履复合式救援工程机械底盘车桥设计与有限元分析

针对液压马达四轮驱动的动力方式,设计了轮履复合式救援工程机械底盘的车桥,对其在各行驶工况下的受力情况进行有限元分析和优化,并对优化的结构进行了模态分析。结果表明,该车桥结构在满足强度要求的基础上有良好的抗振性。     

基于轴箱振动与动力学模型驱动的高速列车车轮失圆状态识别方法

针对高速列车车轮失圆识别难以兼顾效率与精度问题,提出一种基于轴箱振动与动力学模型的高速列车车轮失圆状态智能识别方法。首先,利用静态检测设备采集车轮非圆原始数据,提出一种数据增强技术构建车轮非圆增强数据集。其次,将增强数据集输入至高速列车车辆—轨道耦合动力学模型,获取车轮不同失圆状态下轴箱振动样本集。最后,通过构建恰当结构与配置参数的一维卷积神经网络(1-dimensional convolutional neural network,1-DCNN),可对轴箱振动信号进行自适应特征提取,实现对车轮失圆状态的智能识别分类。结果表明：提出的车轮失圆状态智能识别方法能实现正常车轮、多边形车轮、擦伤车轮、随机非圆化车轮与局部缺陷车轮5类车轮失圆状态的智能分类,准确率达99.2%(标准差为0.05),且单个样本平均识别耗时为0.4 ms。结合现场试验,所提方法对实测轴箱振动具有较好识别能力,测试精度为95%。与经典的SVM和BP神经网络相比,1-DCNN模型具有更高的识别准确度。     

Study on stress states of a wheelset axle due to a defective wheel

High magnitude impact loads caused by a defective wheel may excite various vibration modes of the wheelset, and contribute to adversely increases in the stress states of wheelset axle in high-speed conditions. In this study, the wheelset is treated as a flexible body using the finite element method, then integrated to a multi-body dynamic model of a high-speed train coupled with a flexible track slab model. Through this model the effects of wheel defects considering wheel flats and wheel polygonalizations on the stress states of wheelset axle are evaluated in terms of bending stresses of the wheelset axle. The damage tolerances of the wheelset axle are subsequently predicted using the NASGRO algorithm. The results suggest that the impact forces caused by wheel flats and wheel polygonalizations at the wheel-rail interfaces can result in the resonance vibrations of a wheelset and give rise to severe variations in dynamic stresses of the wheelset axle. The wheel defects-induced stress load cycles considerably contribute to the propagations of the initial crack in the wheelset axle, especially for the wheel polygonalization.