并联机构奇异构型运动稳定性与其动力学参数

以3-RPR并联机构为例,研究了动平台动力学参数对并联机构奇异构型运动稳定性影响。采用Lagrange方法,建立该机构显含自身动力学参数的无乘子二次项非耦合质点系动力学解析方程,基于Lyapunov第一近似稳定性理论,将奇异构型运动稳定性问题转化为一阶线性近似系统特征根问题。研究表明:当动平台绝对速度中心落在奇异构型获得的旋转自由度回转中心临近区域内,并联机构奇异构型运动稳定性较差;增大与动平台回转方向一致的角速度值及输入参数项取值,有利于提高动平台奇异构型的运动稳定性。该研究对于利用机构动力学参数,在设计与实际控制阶段,消除并联机构奇异运动,或提高并联机构奇异构型的运动稳定性,具有积极的理论价值。     

一种含有闭环支链的5-DOF并联机械臂的动力学建模与分析

提出一种双闭环5-DOF机械臂,该机械臂在((2-UPS)+U)PU构型的基础上增加闭环结构,得到新的拓扑构型2-UPS+((2-UPS)+U)PU,闭环结构的引入使得机构获得更高的承载能力且为拓扑新的构型提供了新思路。应用矢量链法,建立了机构的位置模型;推导了支链驱动速度、支链摆动角速度与运动平台广义速度V_o的映射,建立了机构的独立变量q与运动平台广义速度V_o之间的解耦矩阵;建立了机构支链中的摆动杆、伸缩杆质心速度与运动平台广义速度V_o之间映射,并基于虚功原理建立了机构的动力学模型,将推导的动力学模型变换成具有Lagrange动力学形式的动力学模型;在Adams仿真软件中建立该机构的虚拟样机模型,通过仿真验证了推导的动力学模型的正确性。     

结构解耦6-PSS并联微操作平台的研究与开发

利用并联微操作机构的构型原理，提出了结构解耦6-PSS并联微操作平台新机构，描述了微操作平台的运动学模型、静刚度模型、一体化结构模型、几何误差模型和标定策略，研制了微操作平台样机，给出了其测试结果。研究表明，该并联微操作平台的结构解耦及一体化结构是成功开发的关键，为微操作平台机构构型和结构设计提供了新思路。     

耦合型少自由度车用稳定平台综合与分析

基于车辆六维扰动间的耦合运动特征,给出了车用稳定平台构型综合原则及方法,可实现机构少输入、动平台多轴稳定的目标。应用螺旋理论综合了一类具有耦合特征的三自由度并联机构,并提出了几种具有实际应用价值的新机型。以其中的一种构型为例,分析了机构的运动特性,并建立了其耦合运动约束方程,在此基础上提出了表征这种特性的耦合度评价指标,并给出了数值算例。文章基于车用稳定平台应用需求,将耦合型少自由度并联机构用于稳定平台多轴联动补偿,为稳定平台机型设计与分析提供了一种新思路。     

6-UPU电动平台安全性设计分析

在分析6-UPU电动平台运动学反解基础上,给出了平台速度、力Jacobian矩阵,针对影响平台安全性相关因素,考虑双端虎克铰这种特殊结构,分析了结构约束条件,找出平台16种极限工作位置,提出最大力奇异和最大力非奇异空间的判断方法,建立了一种新的平台工作安全性检验算法,并通过具体实例进行了分析验证。实例表明,此方法对类似构型的结构设计及安全稳定性定量分析具有重要的借鉴意义。     

并联机构运动分岔与稳定性分析

在奇异位置处,并联机构具有多个可能的运动趋势,使机构的运动不确定,从而导致并联机构运动失控.为了了解并联机构在奇异位置处的运动稳定性,本文根据并联机构在奇异位置附近的构型分岔特性,提出了一种判定机构构型失控的构型系数方法.该方法能够准确地判定机构的优先失控自由度,给出动平台各位姿分量的失控顺序,为机构的运动控制奠定了理论基础.     

基于新型二级杠杆机构微定位平台的设计与分析

针对传统杠杆放大机构在柔性平台构型设计中存在放大倍数低和响应速度较慢的不足,提出了一种新型二级杠杆放大机构,并在此基础上设计压电陶瓷驱动的单自由度微定位平台.根据柔性铰链的物理特性,通过差异化的铰链组合方式来实现并改善柔性平台的结构功能,进而综合设计一种具有敏捷响应速度和大范围输出位移的新型二级杠杆机构.基于拉格朗日定...     

模块化可展天线机构展开动力学建模与运动规划

模块化可展开天线具有拓展灵活、通用性好、适应性强等特点，是满足未来天线大口径发展趋势的一种新型航天装备。为掌握模块化可展开天线展开过程的动态特性，提出一种六棱柱模块化可展开天线机构展开动力学建模及运动规划方法。首先，阐述了六棱柱模块化可展开天线的结构组成及展开原理，建立了天线机构数值仿真模型，研制了单模块原理样机，并验证了原理方案的正确性；其次，基于多刚体系统动力学Lagrange方法，建立了天线机构在展开过程的动力学模型，得到了缓释电机驱动力随展开时间的变化规律；最后，开展天线机构展开过程运动规划，建立了天线机构S型运动速度曲线模型。研究结果表明：运动规划减小了天线展开过程始末的速度突变，提高了天线展开过程的平稳性，为该构型天线的展开试验及工程应用提供了一种可供参考的速度控制方案。     

高压带电作业机器人升降系统振动分析及控制补偿策略

介绍了高压带电作业机器人的结构和工作原理；建立了高压带电机器人升降系统的非线性动力学模型，用非线性动力学理论对上述模型进行理论分析，求出其二阶非线性近似解，对系统的运动稳定性进行了研究，得出升降平台在受导线交变作用力时在水平平面的轨迹；最后给出了控制补偿策略。     

基于模糊干扰观测器的电动Stewart平台自适应模糊控制

建立了一个电动Stewart平台的统一动力学模型,并基于它设计了一种新型的自适应模糊控制算法。这个统一的动力学模型在任务空间中使用了Newton-Euler方法建立,同时结合了平台动力学和执行器动力学模型。自适应模糊控制算法使用计算力矩方法设计运动平台标称模型的逆动力学控制器,然后使用基于模糊干扰观测器的自适应模糊控制器对模型的不确定性和外部扰动进行补偿。通过数值仿真分析表明,在不引入高增益控制器的情况下,成功地消除了平台参数的不确定性和外部干扰的影响,保证了平台的跟踪性能。     

Minimal Realization of Linear Graph Models for Multi-physics Systems

An engineering system may consist of several different types of components,belonging to such physical"domains"as mechanical,electrical,fluid,and thermal.It is t...     

INTEGRAL EQUATION METHOD＇S APPLICATION IN HOLE-EDGE STRESS OF COMPOSITE MATERIAL PLATE WITH DIFFERENT SHAPED HOLES

The strength of composite plate with different hole-shapes is always one of the most important but complicated issues in the application of the composite material. The holes will lead to mutations and discontinuity to the structure. So the hole-edge stress concentration is always a serious phenomenon. And the phenomenon makes the structure strength decrease very quickly to form dangerous weak points. Most partial damage begins from these weak points. According to the complex variable functions theory, the accurate boundary condition of composite plate with different hole-shapes is founded by conformal mapping method to settle the boundary condition problem of complex hole-shapes. Composite plate with commonly hole-shapes in engineering is studied by several complex variable stress fimction. The boundary integral equations are founded based on exact boundary conditions. Then the exact hole-edge stress analytic solution of composite plate with rectangle holes and wing manholes is resolved. Both of offset axis loadings and its influences on the stress concentration coefficient of the hole-edge are discussed. And comparisons of different loads along various offset axis on the hole-edge stress distribution of orthotropic plate with rectangle hole or wing manhole are made. It can be concluded that hole-edge with continuous variable curvatures might help to decrease the stress concentration coefficient; and smaller angle of outer load and fiber can decrease the stress peak value.     

Non-monotonic material contrast in scanning ion and scanning electron images

30 keV Ga⁺ focused ion beam induced secondary electron (iSE) imaging was used to determine the relative contrast between several materials. The iSE signal compared from C, Si, Al, Ti, Cr, Ni, Cu, Mo, Ag, and W metal layers does not decrease with an increase in target atomic number Z₂, and shows a non-monotonic relationship between contrast and Z₂. The non-monotonic relationship is attributed to periodic fluctuations of the stopping power and sputter yield inherent to the ion–solid interactions. In addition, material contrast from electron-induced secondary electron (eSE) and backscattered electron (BSE) images using scanning electron microscopy (SEM) also shows non-monotonic contrast as a function of Z₂, following the periodic behavior of the stopping power for electron–solid interactions. A comparison of the iSE and eSE results shows similar relative contrast between the metal layers, and not complementary contrast as conventionally understood. These similarities in the contrast behavior can be attributed to similarities in the periodic and non-monotonic function defined by incident particle–solid interaction theory.     

Short-Term Relay Quality Prediction Algorithm Based on Long and Short-Term Memory

The fraction defective of semi-finished products is predicted to optimize the process of relay production lines, by which production quality and productivity ar...     

End-to-End Multiview Gesture Recognition for Autonomous Car Parking System

The use of hand gestures can be the most intuitive human-machine interaction medium.The early approaches for hand gesture recognition used device-based methods....     

Application of Feature Extraction through Convolution Neural Networks and SVM Classifier for Robust Grading of Apples

This paper proposes a novel grading method of apples,in an automated grading device that uses convolutional neural networks to extract the size,color,texture,an...     

分布动态载荷识别的抗噪处理

针对正交多项式频域法在用多种响应对矩形薄板进行载荷识别中抗噪性较差的问题,综合运用平均法、矩阵预处理和奇异值截断法等方法对之进行改善,并引入空间映射的思想,将该方法的应用范围拓展为复杂的模型.利用仿真算例,证实了该方法具有较好的抗噪性.     

基于MELTAC-N平台的核电厂安全级DCS环网研究与测试

针对工程实践中环网通讯相关问题的处理缺乏理论基础及国产化安全级DCS平台的开发缺乏成熟经验借鉴问题,对基于MELTAC-N平台核电厂安全级DCS环网的软硬件实现进行了研究。提出了安全级DCS环网双环网冗余设计、光切换开关设计等硬件设计方法,以及以RPR协议为基础,采用全数据收发策略的软件设计方法。在CPR1000安全级DCS平台上对安全级DCS环网的可靠性及实时性进行了评价,并进行了容错能力、响应时间及响应时间稳定性测试验证实验。结果表明,基于MELTAC-N平台安全级DCS环网软硬件设计具有较好的容错能力及响应时间稳定性。     

The laboratory simulation of abrasive wear

Abrasive wear has long been recognised as one of the most potentially serious tribological problems facing the operators of many types of plant and machinery; several industrial surveys have indicated that wear by abrasion can be responsible for more than 50% of unscheduled machine and plant stoppages. Locating the operating point of a tribological contact in an appropriate operational ‚map’︁ can provide a useful guide to the likely nature and origins of the surface degradation experienced in use, though care must be exercised in choosing the most suitable parameters for the axes of the plot. Laboratory testing of materials and simulations of machine contacts are carried out for a number of purposes; at one level for the very practical aims of ranking candidate materials or surface hardening treatments in order of their wear resistance, or in an attempt to predict wear lives under field conditions. More fundamentally, tests may be aimed at elucidating the essential physical mechanisms of surface damage and loss, with the longer term aim of building an analytical and predictive model of the wear process itself. In many cases, component surface damage is brought about by the ingress of hard, particulate matter into machine bearing or sealing clearances. These may be running dry although, more usually, a lubricant or service fluid is present at the interface. A number of standardised wear test geometries and procedures have been established for both two- and three-body wear situations, and these are briefly described. Although abrasive wear is often modelled as following an ‚Archard’︁ equation (i.e. a linear increase in material loss with both load and time, and an inverse dependence on specimen hardness) both industrial experience and laboratory tests of particularly lubricated contacts show that this is not always the case: increasing the hardness differential in an abrasively contaminated lubricated pair may not always reduce the rate of damage to the harder surface.     

ANGULAR DISTORTION ALLOWABLE VALUE AND ASSESS METHOD OF WELD ON COKE TOWER

A graph as the new engineering method for estimate the safety of bulging deformation of coke tower is proposed. Through stresses analysis of circumferential weld of coke tower and comparing the stresses produced by pressure with heat stress of steady state, residual stress, bending stress produced by both itself weight and wind loads, it showed that the stresses produced by pressure on the angle distortion are the main factor of equivalent stress of the combined stress. After comparing four kinds of stress controlling conditions, the relation to stress with depth of angular distortion, grade of curvature of angular distortion and half of region of angular distortion has been inferred. Graph of deformation allowable value of coke tower for different condition by angular distortion and half of region of angular distortion has been plotted. The five steps for its engineering use have been explained. The lighter the grade of curvature is, the larger of bulge allowance, may be, and the bigger of depth of angular distortion may pose too. For the coke tower with a popular structure of Dg 5 400 mm×28 mm, the result by graph is nearly more than the result of two formulas formed by other research, the error is less than 7.0%. But, the graph can be easily applied to different size of angular distortion.