A direct method for the evaluation of instantaneous invariants of a given motion

Explicit formulas are derived for the evaluation of the instantaneous invariants for a given motion. The use of these formulas brings the application of the theory of mechanism synthesis for higher order approximations (first presented by Venkamp) to a practical level where a mechanism designer can readily use this elegant and computationally efficient theory for designing motion generating or function generating fourbar mechanisms.     

求解复杂机构运动瞬心的解析法

应用相对运动反转法及运动链矢量环路方程，导出了确定平面机构中任意2个构件之间的相对运动瞬心位置计算式。并由此推出瞬心速度、瞬心曲线、加速度瞬心的解析计算式，证明了三心定理是该计算式的特例。     

基于运动模式在线分类的移动机器人目标跟踪

区别于以往采用固定运动模式的目标跟踪研究,提出一种基于单目视觉传感器的人体运动模式在线识别算法,及基于此算法的人体目标跟踪方法。首先,利用视觉信息检测运动目标,并提取其视觉特征;然后通过单目视觉深度提取算法,获取目标的运动特征;接着将连续几帧的特征变化矢量送入随机森林(RF)进行学习,实现对人体运动模式的在线分类;最后根据分类结果在线选取不同的目标运动模型,并利用近似最优的粒子滤波器实现对目标运动状态的准确估计。实验结果证明了本文提出算法的有效性。     

Numerical analysis of TEHL line contact problem under reciprocating motion

This paper presents a full numerical analysis to simulate the thermal elastohydrodynamic lubrication (TEHL) of steel–steel line contact problem under reciprocating motion. The equation system is solved using multigrid techniques. General tribological behaviors of TEHL under reciprocating motion are explained. Comparison between thermal and isothermal results reveals the importance of thermal effect in prediction of the traction coefficient and film thickness. The influences of frequency, stroke length, and applied load on the variations of film thickness, pressure and traction coefficient during one working cycle are discussed. Furthermore, the influence of slide–roll ratio on tribo-characteristics of oil film under same entraining velocity is revealed.     

On the instantaneous acceleration of points in a rigid body

This work re-examines some classical results in the kinematics of points in space using modern vector-matrix methods. In particular, some very simple Lie theory allows the velocities and accelerations of points to be found in terms of the instantaneous twist of the motion and its derivative. From these results many of the classical results follow rather simply.Although most of the results are well known, some new material is presented. In particular, the discriminant curve that separates cases with one or three real acceleration axes is found and plotted. Another new result concerns the chords to the cubic of inflexion points. It is shown that for points on such a chord the osculating planes of the point's trajectories are parallel. Also a new result is found which distinguishes between cases where the Bresse hyperboloid of points whose velocities and accelerations are perpendicular, has one or two sheets.     

一种瞬时浮点ADC电路的设计

提出了一种瞬时浮点ADC电路的设计方案,论述了循环放大与自动校零算法、浮点ADC原理及其实现方法.该电路可实现失调误差自动补偿、快速增益自适应控制以及浮点模数转换等,其全局和瞬时动态范围分别达到150 dB、90 dB,采样速率达80～130 ks/s,有效精度达25 bit.     

基于动作分析的涡轮增压器装配线作业分析与优化

动作分析是规范动作标准及改善生产线作业绩效的重要方法。以某公司废气涡轮增压器装配二线操作人员为研究对象,运用动作分析对装配线所有工序操作人员的作业过程进行细微动作分析,对摄像视频进行作业时间分析并结合秒表测定法测定各个工序的作业时间,然后根据动作经济原则对作业动作进行优化,使用MOD法预测标准作业动作时间,得到适用于该装配线上操作人员的最合理、最有效、最省时、最经济的标准动作体系和标准作业时间,提高了整条线的作业效率与质量。     

某微型轿车踏板布置运动分析

在CATIA中对某微车的踏板进行了布置和运动分析,得出了踏板的运动曲线。根据轿车及其变型车的标准进行了校核,符合国家标准,这为后期优化设计提供了理论数据。     

随机模式投影双目测量系统中的单目测量方法

针对基于随机模式投影的双目立体测量系统的特点,提出了一种由单摄像机-投影器构成两个单目测量单元的测量方法。首先给出了一个简洁有效的标定算法,该算法只需从不同角度拍摄随机光场在普通白板上的图像（称为标定图像）,就可以标定纯随机模板上每一点经投影镜头发出的光线。无需标定投影镜头畸变,且精度不受投影镜头畸变的影响。然后将随机光场照射下的被测物体图像与标定图像进行亚像素精度的像点匹配,根据三角测量原理获取物体表面的三维点云数据。最后采用标准平面对该方法进行测量精度验证,并给出了具体的测量实例。实验结果表明：平面度测量精度为0.0175mm,不确定度<0.05mm(3σ)。由于采用单目测量单元进行测量时,空间一点无需在两个摄像机视场内均可见,因此避免了因局部高光、被测物体自身遮挡等原因引起的三维测量数据丢失,有效地弥补了双目测量系统的不足。     

Flow instabilities in a graft anastomosis: a study of the instantaneous velocity fields

The major cause of arterial bypass graft failure is intimal hyperplasia. Fluctuating wall shear stresses in the graft, which are associated with disturbed flow, are believed to be important factors in the development and localization of intimal hyperplasia. This study, based upon water as the working fluid, has investigated the flow structure inside a 30 degree Y-junction with different fillet radii at the intersection between the graft and the host artery at various Reynolds numbers and distal outlet segment (DOS) to proximal outlet segment (POS) flow ratios. The structure of the flow has been investigated experimentally using particle image velocimetry (PIV). The two-dimensional instantaneous velocity fields confirm the existence of a very complex flow, especially in the toe and heel regions for the different fillet radii and clearly identify features such as sinks, sources, vortices and strong time dependency.     

基于MC464水火弯板机八轴运动控制系统的设计

针对目前手工经验型水火弯板工艺方法存在的劳动强度大、效率低的问题,设计了基于嵌入式运动控制器MC464的水火弯板机八轴运动控制系统,并通过以太网与上位工控机进行实时通信,实现人机交互,通过Modbus与PLC通信,实现数字输入输出口的扩展.设计的运动控制系统满足了水火弯板工艺要求,实现了水火弯板全自动控制和机电一体化,降低了劳动强度、提高了弯板质量和效率.     

Prediction and compensation of motion accuracy in a linear motion bearing table

In the present research, a corrective machining algorithm is introduced to improve the motion accuracy of linear motion bearing tables. The algorithm commences with reverse analysis, in which the rail form error is estimated from the measured linear and angular motion errors. In the next step, the rail is remachined to reduce the estimated form error. Then, the motion errors are measured again, and the procedure is repeated until the measured errors are sufficiently small. A transfer function, which represents the bearing force variation of a bearing block with respect to the spatial frequency components of the rail form error, is used to describe the characteristics of the linear motion bearings. Computations are carried out via the Hertz contact theory. From the theoretical evaluation, it is evident that the magnitude of the normalized transfer function quantitatively represents the accuracy averaging effect at each spatial frequency and that motion errors are not affected by the preload and the stiffness of the bearings. It is also clear that the algorithm can be used to estimate the equivalent rail form error in terms of motion errors. As a practical application, the algorithm is utilized to improve the motion errors of an XY table with linear motion bearings. The experimental results show that the motion accuracy of a linear motion bearing table can be improved to about 1 μm of linear motion error and about 1-2 arcsec of angular motion error by applying the proposed algorithm.     

用电容法测量瞬时接触线上油膜厚度的传感器设计和数据处理

本试验研究应用自己设计的传感器和微机数据采集处理系统，传感器沿瞬时接触线方向设置采用精度很高的线切割工艺切槽。设计了一套模拟电路，在ＧＺ１５０型封闭功率流高速齿轮实验台上，对斜齿圆柱齿轮多种工况条件下的齿面润滑状态进行了动态跟踪监测，并与理论计算进行了对比，结果表明：该方法是切实可行的。     

The performance of a new measuring method for three-dimensional ball motion in a ball-bearing

Recently, a new method for measuring ball motions three dimensionally was developed by one of the present authors and its principle was reported in the previous paper.Before its practical applications were examined, the calibration tests were carried out and the outputs obtained by this new method were compared with the values expected theoretically. By compensating for some undesirable effects, it was confirmed that the outputs were sufficient to analyse actual ball motions within an experimental error of 5%.In order to demonstrate its usefulness, an example of experimental results obtained by this new technique is shown.     

A numerical analysis of the elastohydrodynamic line contact film formation at motion start-up

A mathematical model is proposed of the process of formation of the elastohydrodynamic (EHD) lubricant layer between resilient cylinders that begin to rotate in the lubricating material medium from the resting state. The model assumes division of the whole contact region into three zones: the zone within which dry motion is described by the equations of the elastohydrodynamic theory of lubrication, the transient zone, and the dry contact zone. The method of the numerical solution of this system of equations is presented. The calculations are performed for the lubricating material that was used in the published experimental study of the process of formation of the EHD lubricating layer between the resilient ball and the flat resilient base. It is shown that the calculation results well agree with the experimental data both qualitatively and quantitatively providing that the transient region dimensions are adequately selected. The function of the pressure distribution, the lubricating layer thickness, the lubricating material flow, the rate of approach of the surfaces over the contact region at different moments of time, the time dependencies of the lubricating layer thickness at different points of the contact region, and the coordinates of the boundary points of the dry contact region is also presented.     

四高炉1#线保护系统的配置与完善

主要介绍了LFP-951、LFP-966保护系统性能特点及在太钢发电厂四高炉1#线上的应用.     

刨花板生产线中的铺装物料控制

针对刨花板生产线铺装带输送物料的特点,本文给出保证物料恒流量控制的策略、控制系统框图及软件设计方案。     

某钢厂中型生产线称重机系统升级改造

详细介绍莱钢型钢厂中型生产线称重机系统存在的主要故障及缺陷,进行了详细的分析,并相应提出了改进和改造措施,通过对称重机系统实施相应升级改造,确保原料称的称重精度和工作的稳定性。     

彩色电致发光线产品的剖析

采用扫描电镜/X射线能谱、红外光谱和原子吸收光谱等现代仪器测试方法对一种多涂层材料构成的电致发光线产品进行剖析,包括对各涂层材料成分的检测以及产品结构特性的分析,为进一步的开发和应用该种新产品提供技术参考依据。