基于Petri网的虚拟装配环境建模及其应用

通过分析虚拟装配环境的结构及性能,针对场景图数据结构在虚拟装配应用中的不足,定义了一种基于知识的层次对象时间Petri网,并用于建立虚拟装配环境的应用层模型。该模型以虚拟手的位姿作为输入,运行后输出具体的操作事件更新场景图,完成装配活动,以满足虚拟装配环境的实时和并发等动态性能要求,实现了虚拟装配大量离散事件的处理及装配意图的响应。给出了基于知识的层次对象时间Petri网的产品装配模型表达,不仅表达了产品结构及装配关系,同时记录零部件在装配过程中的方位及约束状态等动态信息,从而在虚拟装配环境中实现了装配与拆卸并存的实际装配活动。此外,还给出了由产品装配层次图生成的基于知识的层次对象时间Petri网装配模型的算法,说明了基于应用层模型的装配、拆卸操作以及装配过程仿真,开发了原型系统。     

面向机械产品装配过程的在线故障诊断策略研究

针对机械产品装配过程扰动因素复杂众多、在线故障诊断机制响应不及时的问题，提出了一套面向机械产品装配过程的在线故障诊断策略。首先通过数据采集终端对装配过程信息的实时动态采集分析，构建装配过程故障实时状态模型；然后建立了融合故障树分析技术的专家系统诊断机制，并运用控制图对故障源持续关注，从而实现对机械产品装配过程故障的实时在线诊断。通过实例验证，该策略使得车间技术人员能够及时掌握和有效处理装配过程故障事件，提高了对装配过程的精益化控制。     

面向增强现实装配的虚实遮挡技术研究

目前增强现实中的虚实遮挡算法大多数是一般性方法,缺少相关文献针对虚拟装配的特点研究增强现实装配中的虚实遮挡问题.分析了增强现实装配场景中虚实零件、装配特征、上下文导航等元素间的遮挡关系,提出了针对增强现实装配的虚实遮挡方法.原型系统试验证明该方法能够有效解决增强现实装配中虚实遮挡问题.     

增强现实诱导拆卸序列规划研究

装配体的拆卸序列规划研究对于增强现实维修诱导系统具有重要意义。为能以较高效率求解诱导拆卸装配体的序列方案,基于装配体中零件之间的干涉矩阵,提出并建立目标装配体的拆卸混合层次图模型。通过拆卸影响因子的分析,进一步得到装配体拆卸时间数学模型,并运用自适应遗传算法求解最优的拆卸路径。最后,通过增强现实诱导拆卸系统仿真实例,验证了此方法的可行性和准确性,为增强现实诱导拆装系统的进一步开发和改进奠定了基础。     

基于数字孪生的增强现实多人协作装配

为了保证复杂产品在关键装配阶段的一次成功率和质量一致性,提出一种基于数字孪生的增强现实(AR)多人协作装配方法。首先提出基于数字孪生的AR多人协作装配架构,根据协作装配的复杂性对装配序列进行过程分解;其次将装配过程上下文数据构造为装配工艺知识图谱,明确了协同过程装配信息的传递与迭代机制,提高了AR协作装配的工况自适应性。在此基础上采用基于根锚点的协同方法实现多人装配过程的AR场景协同,并通过装配工艺知识图谱提供的实时知识实现数据协作,保证了协同装配的质量和效率。以某钢厂复杂轧机的装配为例,建立了基于增强现实的多人协作数字孪生装配系统,验证了所提方法的有效性和可行性。     

基于偏差传递的二维多工位装配夹具系统公差可行稳健设计

提出一种基于偏差传递的二维多工位装配夹具系统公差可行稳健设计方法。分析二维多工位装配尺寸偏差传递关系,建立由定位销和零件定位孔(槽)公差引起夹具定位偏差的偏差流状态空间模型。采用数论网格方法对定位销和零件定位孔(槽)公差进行采样,将得到的公差样本代入夹具定位偏差模型,求得夹具定位偏差样本空间,将夹具定位偏差作为状态空间模型的输入偏差,提出基于状态空间模型的二维多工位装配成功率计算方法。继而应用Taguchi正交试验直观分析方法,分析得到影响装配成功率的主要因素即夹具系统定位销副关键公差,运用回归正交组合设计拟合得到二维多工位装配成功率与夹具系统定位销副关键公差的响应面模型。以定位销、零件定位孔(槽)制造成本所构成的装配成本最小化为目标,二维多工位装配成功率为约束,建立二维多工位装配夹具系统定位销和零件定位孔(槽)公差可行稳健设计模型。以汽车车身地板二维三工位装配为例,建立其公差可行稳健设计模型并对该模型进行计算与分析,结果表明在装配成本增幅较小的情况下,采用稳健约束后可显著提高公差设计的可行稳健性。该方法为二维多工位装配夹具系统公差稳健设计提供了一种新途径。     

基于Kinect的投影式增强现实 装配诱导系统研究

针对大批量定制中产品装配工艺转换快、效率低、易出现差错等问题,提出并设计了一种投影式增强现实装配诱导系统。对装配诱导过程中操作者所需穿戴设备和手动操作计算机设备优缺点进行了归纳,系统将文字、图片和三维动画等诱导信息投影到真实装配场景中,诱导操作者完成了产品装配,并对此进行了测试;利用骨骼跟踪技术和人手边缘轮廓提取方法进行了手势识别研究,提出了一种装配诱导过程中的徒手交互方法,利用Kinect跟踪操作者头部方位,提出了一种基于视点跟踪自动变换投影图像,以及使投影内容随操作者视点变化的投影增强现实方法。研究结果表明:该系统可提高装配诱导过程中的人机交互性能和装配效率,具有一定的工程应用价值。     

基于图像自然特征的增强装配引导系统

基于增强现实的产品装配引导有助于提高装配过程的人机效率,研究了增强装配引导信息的建模技术,实现装配过程引导信息的统一组织管理;基于图像自然特征,利用BRIEF算法进行图像匹配,实现虚实装配零件注册;基于虚实注册信息,实现装配引导信息在真实装配场景中的叠加,并建立了增强装配引导原型系统。增强装配引导作为一种新型的人机交互方式,可用于辅助工人进行装配作业,有助于提高装配培训的效率。     

增强现实装配工艺信息内容编辑技术

为了解决增强现实装配的工艺信息内容编辑困难的问题,从装配作业常用工艺出发,根据面向增强装配工艺信息的表达特点,对装配作业常用工艺进行分类,提取基本装配工艺类型,运用IDEF1X方法建立基本装配工艺信息模型;通过增强现实可视化技术,对基本装配工艺信息模型进行增强可视化表达;最后对增强装配工艺信息内容编辑数据的管理进行研究;开发了面向增强现实的装配工艺编辑原型系统,并通过典型基本装配工艺的编辑,对系统的有效性进行了验证。     

基于实时信息的飞机装配技术状态管理方法研究

为了解决飞机装配过程中的实时数据采集和分析问题,提出了一种基于实时信息的飞机装配技术状态管理方法。方法的核心是建立技术状态数据网络模型,利用RFID技术来配置模型;同时,建立沿时间轴的技术状态数据网络,实现装配过程中的信息跟踪、监控、识别及溯源。     

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.     

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。     

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....     

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.     

Limits of topographic measurement by the scanning tunnelling and atomic force microscopes

Parameters describing the topographic character of a surface (height, surface wavelength, slope and curvature) can be derived from equivalent sinusoidal profiles. The response of a surface-measuring instrument may be modelled in terms of instrument parameters such as stylus radius, and scanning range and resolution. The performance of the instrument may then be mapped as a zone in amplitude-wavelength (AW) space to show the sinusoidal profiles it is capable of measuring. In a first-order analysis the STM and AFM are considered as equivalent to contact-stylus instruments with a notional stylus radius equal to the tip radius plus the gap. Comparisons between different instruments and types of instrument are readily made by mapping in AW space. The error arising from convolution of the sinusoidal profile with that of the finite tip may be quantified and plotted as contours in AW space.