基于在线最小二乘支持向量机的数控机床热误差建模与补偿

为消除数控机床热误差对加工精度的影响,提出了基于在线最小二乘支持向量机的数控机床热误差建模方法。为构建机床热误差模型,进行了建模实验,采用智能温度传感器与激光位移传感器分别测量机床温度值与主轴热变形量。将获得的数据进行在线最小二乘支持向量机建模训练,构建机床热误差模型。在根据模型得出误差预测值的同时,可以不断根据在线输入的新数据修正热误差模型本身,运算时间短,适用于在线建模。实验结果表明,基于在线最小二乘支持向量机的数控机床热误差建模方法具有精度高、鲁棒性强和计算时间短的特点。在此基础上,根据在线模型进行热误差补差,可有效消除机床热误差影响,提高数控机床的加工精度。     

干切滚齿机热变形误差模型及其误差补偿技术研究

针对YDE3120CNC干切滚齿机床,运用热传导形成温度梯度原理、金属材料热膨胀原理、材料力学中梁的伸长和弯曲变形理论基础,分析了该机床热变形误差,并提出了一种滚刀与工件主轴相对位移热变形误差数学模型。在此基础上研制了一套用于干切滚齿机热变形误差补偿系统,利用该系统从间接和直接的角度测量出滚刀与工件主轴相对位移,然后进行热变形误差补偿实验。通过该实验,验证了该机床热变形误差数学模型的正确性及可靠性,为干切滚齿机床在线热变形误差检测及补偿打下了基础。     

基于球杆仪的五轴机床RTCP误差检测及补偿

针对五轴机床RTCP误差检测存在检测时间长、测量精度低的情况,提出用球杆仪检测RTCP误差的方法,分析可知AC双转台RTCP误差不仅有4项位置误差,而且存在4项角度误差和初始安装误差。根据机床运动链建立AC双转台RTCP误差模型,采用基于球杆仪的检测方法,并推导RTCP误差元素求解方法。通过误差补偿试验验证了误差模型和误差求解方法的准确性和有效性。     

基于动态自适应LS-SVM的数控机床热误差建模研究

热误差是造成切削加工工件精度低的重要因素,研究机床热误差是提高加工精度的有效措施。为此,综合考虑最小二乘法(LS)、支持向量机(SVM)和动态自适应算法的优势情况下,提出了一种基于动态自适应LS-SVM的数控机床热误差建模方法。为构建热误差模型,以数控机床XK713进行试验,通过温度和位移传感器分别获取机床温度值与主轴变形量,同时通过动态自适应算法,参数能够被优化,以及对所采集的数据进行最小二乘支持向量机建模,从而可得该数控铣床热误差模型。通过与LS热误差建模方法进行对比分析,结果表明:所提出的热误差模型的精度远优于LS模型。该方法为机床热误差建模的研究和应用奠定了基础。     

数控机床空间误差球杆仪识别和补偿

提出了多轴机床空间误差的球杆仪识别方法和补偿技术。建立了机床刀尖相对工件的空间误差的误差参数模型;给出了在机床工作空间中三个互相垂直的平面内,用球杆仪测量圆周运动的半径误差结合机床的空间误差模型识别定位、直线度、角度、垂直度和反向间隙等误差参数的方法。补偿试验结果证明该误差识别与补偿方法省时有效。     

数控机床热误差建模与补偿

数控机床热变形误差对零件加工精度有重大影响。基于GA-SVR(遗传算法-支持向量回归机)的数控机床热误差建模方法要点有三:其一是数据采样,用不同传感器测量机床关键点的温度与机床主轴变形量。其二是数据训练,把获得的数据进行支持向量回归机建模训练,同时使用遗传算法寻找支持向量回归机相关参数的最优值。其三是数据建模,建立机床热误差模型,并验证模型的准确度。仿真及实验结果表明,基于GA-SVR的数控机床热误差建模方法具有精度高和鲁棒性强的特点。并依此算法建立了以DSP和A/D为核心的热误差补差补偿器。     

基于OE-CM算法的机床主轴热误差建模与补偿分析

针对机床热误差建模过程中,误差信息不透明、数据特性不全面等不利因素,根据机床主轴热误差实验数据,分别采用GM(1,n) 模型和最小二乘支持向量机(LS-SVM)模型建立主轴热误差预测模型并进行线性叠加,然后采用预测有效度算法调整模型加权系数,建立了最优有效度复合预测模型（OE-CM）以获取最佳预测效果。在VXC-560型三轴数控机床上进行在线实验建模,实验结果表明：OE-CM具有预测精度高、鲁棒性好等特点,整体预测效果优于灰色GM(1,n)模型和LS-SVM模型,适合在复杂工况条件下对机床主轴热误差进行预测和补偿,为提高机床热误差补偿精度建立了理论模型。为了验证该预测模型的有效性,对所研究的机床主轴进行热误差在线补偿,机床主轴Z向最大误差从23.8μm减小到8μm,减幅达到66.4%,较好地提高了机床精度,具有一定的工程化推广前景。     

基于有限元的机床导轨热误差分析

机床热误差是影响高精密机床加工精度的重要因素之一,而目前对机床热误差的分析比较少,以机床导轨为研究对象提出了一种结合有限元理论的导轨热误差确定方法,将数值模拟技术和实际测量实验相结合,利用实验测量数据修正有限元分析边界条件,从而得到准确的导轨热变形计算结果,证明了该热误差确定方法应用到实际机床导轨热误差确定和补偿方面的...     

超精密平面度在线检测方法研究

磨削问题过实验,效性。介绍了一种用最小二乘逐次两点法对超精密平面度进行在线检测与误差分离的方法;针对平面光学玻璃设计了一套在线测量系统,所提出的方法可以精确而快速地分离出被测平面移动的导轨运动误差,通验证了该测量方法能在机床上直接测量工件的平面度误差,消除基准误差,从而保证实现在线测量的有     

基于机器视觉的车床主轴径向跳动误差测量方法研究

非接触测量是解决主轴在线测量的途径。为此研究一种机器视觉系统用于机床主轴径向跳动误差的测量。该系统由面阵CCD相机、镜头、光源、计算机和图像处理软件组成。CCD传感器记录主轴边缘点的跳动图像,经过图像数据处理得到边缘点的跳动数值。设计长像距镜头,使得物象比例接近1,结合亚像素定位算法,提高边缘实际定位精度。经过分析验证,系统测量得到的径向跳动误差达亚微米级。表明该方法可以用于检测机床径向跳动精度,适用于转速较低的加工机床主轴跳动误差在线测量。     

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.     

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....     

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.