五轴机床分类运动学建模及后置处理验证

针对常见的三大类型正交结构的五轴机床,根据齐次坐标变换和运动链关系,推导建立了双转台型、摆头转台型、双摆头型五轴机床的运动学模型。根据矩阵方程的逆解,确定了A、C轴的旋转角度取值范围,基于UG-post开发了后置处理器,在UG环境中以凹球面为例,生成5轴铣削刀路,AC型五轴机床的实际加工验证了后置处理算法的正确性和有效性。     

非正交五轴联动数控机床后置处理算法

针对转动工作台与主轴成45°倾角的特殊双转台五轴联动数控机床,在分析机床结构和运动特点的基础上,提出了两种刀位后置处理坐标变换的计算方法,并推导出相应的坐标变换公式。该算法基于三维图形几何变换理论,解决了非正交旋转轴机床后置处理的坐标转换问题。经CAD/CAM软件C im atron E6.0的图形验证及DMU70V的机床验证,均表明该算法正确可靠。     

经济型五轴数控机床后置处理系统研究与应用

在双转台五轴数控机床结构的基础上,通过分析机床结构坐标系和CAM加工坐标系的关系,建立其机床加工刀头运动轨迹的数学模型,推导出该类型机床的后置处理转角计算公式和坐标转换计算公式。根据推导结果,在UG/PostBuilder通用后置处理器的基础上,针对不同类型五轴联动数控机床选配特定数控系统,设定机床参数、程序和刀轨参数、NC代码格式设置,编制了双转台式五轴数控机床的专用后置处理程序,经实际加工验证可以满足经济型五轴联动后置处理的要求。     

双转台五轴数控机床后置处理算法研究

通过分析双转台五轴数控机床坐标系和CAM加工坐标系的关系。建立其数学模型。进行机床运动学求解。推导出该类机床后置处理转角计算公式和坐标转换计算公式。根据推导结果。开发了UCP600五轴数控机床专用后置处理程序，经实验验证可以满足五轴联动后置处理的要求。     

非正交三转动二平动五轴机床运动学分析

针对旋转轴非正交三转动二平动的五轴机床,提出一种通用的机床运动学分析和求解的方法,并把该方法推广到任意结构的三转动二平动五轴机床的运动学分析中。分析旋转轴正交和非正交的五轴机床的结构,将绕空间任意轴旋转的非正交结构机床的运动学变换统一到旋转轴正交结构机床的运动学变换中。对自由曲面和整体式叶轮的刀位文件进行后置处理,并利用Vericut软件进行加工仿真验证,证明该运动学分析方法的正确性。     

带倾斜回转工作台的四坐标后置处理方法

针对带倾斜回转工作台的四坐标数控加工的后置处理,提出了一种非正交多轴联动数控机床的逆运动学求解方法。基于矢量绕任意轴线的旋转变换,建立了非正交情况下四坐标机床各运动坐标同刀位数据之间的映射关系,从而实现了机床平动坐标和转动坐标的计算。该方法同样适用于非正交情况下五坐标机床的逆运动学求解。利用刀具同加工表面相切的控制方式,给出了实际加工中进刀及退刀过程的构造方法。本文方法稳定可靠,并已成功应用于工程实际中。     

DMU50 eVolution非正交五轴机床的后置处理研究

由于DMU50 eVolution五轴加工机床具有高精度、高性价比,因此被广泛使用。然而机床工作台的B轴与机床的Y轴不重合,属于非正交结构,使得加工程序的后置处理相对困难。通过对双转台五轴机床开展结构分析,对任意刀具轨迹数据点,先求解出机床双转台的B轴和C轴后置处理转角大小,然后利用求解出的转角大小,通过坐标变换,求解出该刀具轨迹数据点对应的机床位置。利用后置处理算法开发了DMU50 eVolution五轴机床程序后置处理软件,该软件可将UG软件编制的加工程序转换为通用G代码程序。     

双摆头型五轴数控机床的坐标变换关系研究

以双摆头五轴数控加工中心结构为例,包括两个旋转轴A/C和X、Y、Z三个直线轴。分别研究刀具在平动与转动中刀位点的变换关系,建立刀位点换算关系式;根据该机床结构搭建相应的运动学方程,从机床的动态角度出发,分析五轴联动过程中刀位点及刀轴矢量的运动变化规律,运用工程数学计算方法建立A/C轴旋转角度与X/Y/Z轴向坐标数据补偿关系式,实现C-A(X)型双摆头型五轴联动机床的运动求解,为后续的后置处理器的构造作理论基础。     

双转台五轴立式机床专用后置处理算法

通过分析WABECOH双转台五轴立式数控机床各轴的运动关系,建立各轴运动关系的数学模型,并开展机床运动学求解,给出了该五轴机床后置处理的转动角度和坐标变换计算公式。根据转动角度和坐标变换的计算公式,利用C++语言开发了WABECOH五轴数控机床专用后置处理程序,基于所提后置处理方法进行了叶轮类复杂零件的加工仿真与实验验证。结果表明,所开发的专用后置处理软件生成的数控代码可以满足该机床五轴联动的要求,较好地解决了该类机床的后置处理问题。     

双转台五轴数控机床运动变换及求解方法的研究

数控加工后置处理是实现多坐标数控机床正确、高效完成加工任务的关键步骤.在后置处理器系统设计中,机床运动变换尤为重要,它的任务是将刀位点信息和刀轴矢量信息.转化为各运动轴在机床坐标系中的运动量.五轴数控加工后置处理的难点是机床坐标运动变换;以双转台机床为例,利用机构运动学原理,推导出了刀位矢量及刀位点运动变换模型,给出了其表达式;通过仿真分析对该算法进行了验证;检验结果表明所提出方法是正确可行的而且适用于其他任何类型的五轴机床.     

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.     

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.