基于正则化的机床热误差自适应稳健建模算法

通过建立预测模型对机床热误差进行补偿,是有效解决热误差造成机床精度下降问题的常用方法。本文提出一种基于正则化的数控机床热误差自适应稳健建模算法,能够在建模过程中自适应选择温度敏感点(TSPs),并具有高预测精度和稳健性。首先基于结构风险最小化原则对热误差建模稳健性机理进行分析,进而利用正则化算法中LASSO解的稀疏性实现自适应TSP选择。然后基于不同实验条件的热误差数据,分析所提建模算法的预测效果,并与常用的多元线性回归、BP神经网络和岭回归算法进行比对分析。结果表明,本文所提建模算法具有最高的预测精度和稳健性,分别为5.22和1.69μm。最后,利用所建立的预测模型进行热误差补偿实验,以验证本文所提建模算法的实际补偿效果。     

基于偏最小二乘的数控机床热误差稳健建模算法

建立预测模型对热误差进行预测和补偿是解决机床热误差问题的常用方法,该方法中模型的预测精度和稳健性易受环境温度影响而明显下降,对此本文提出了基于偏最小二乘法的热误差稳健建模算法。首先使用相关系数法筛选温度敏感点,并建立热误差偏最小二乘回归预测模型。进而基于全年环境温度下的多批次热误差实验数据,分析最佳的温度敏感点个数。最后建立热误差偏最小二乘回归模型,并与普通多元线性回归模型的预测效果比对分析。结果表明本文所提算法平均预测精度为5.7μm,模型稳健性为0.56μm,相较于普通多元线性回归算法,预测精度和稳健性分别提高13.8%和49.5%。说明本文所提的热误差稳健建模算法能够在环境温度变化较大时保持高预测精度和高稳健性。     

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。     

变工况下基于迁移学习融合域内对齐的机床主轴热误差模型

热误差建模和补偿是提高机床加工精度的重要手段。 将得到的热误差模型应用到类似或相近任务中,对减少模型构建 和数据收集的成本具有重要意义。 本文提出了一种简易迁移学习(EasyTL)融合域内对齐的主轴热误差建模方法,以实现不同 工况下误差模型的迁移复用。 建立基于域内对齐和距离矩阵全组合择优的热误差迁移模型参数选取方法,获得最优组合。 进 一步分析不同类型的域内对齐和距离矩阵各自对模型迁移性能的影响。 最后,将迁移模型与 kNN 典型机器学习模型和卷积神 经网络深度模型进行比较验证,分别预测不同工况下主轴 Z 向和 Y 向的热误差。 此外,根据预测的主轴热误差进行工件补偿 加工实验。 该方法为热误差建模及补偿提供了一种新思路。     

精密数控车床主轴热误差建模

开展了精密数控车床主轴系统热误差补偿的实验与建模方法的研究。建立了精密数控车床主轴系统轴向与径向偏转热误差补偿模型以增强其误差补偿能力,并提高机床加工精度。构建了主轴系统热误差测试平台,应用五点法测试主轴系统热误差,使用热电偶与红外热像仪测量主轴系统温升关键点温度变化数据,应用灰色综合关联分析法实现温度敏感测点辨识。构建了基于粒子滤波重采样粒子群算法的热误差预测模型,对模型预测效果进行评价。结果表明:基于粒子滤波重采样粒子群热误差补偿模型得到的轴向热误差预测残差为-1.29μm~1.55μm,建模精度为95.04%;y向热偏转误差预测残差为-4.68×10~(-6°)~9.66×10~(-6°),建模精度为91.26%;z向热偏转误差预测残差为-5.83×10~(-6°)~8.59×10~(-6°),建模精度为93.24%。实验结果证明该热误差补偿模型具有较高的预测精度,具有较强的工程应用价值。     

数控机床几何误差与热误差综合建模及其实时补偿

为提高数控机床的精度,提出一种数控机床的几何与热的复合误差综合建模方法。通过分析机床在不同温度状态下的误差数据,得到机床误差分布规律;根据几何误差和热误差的不同特性进行误差分离,采用多项式拟合与线性拟合方法建立机床几何误差与热误差的综合数学模型;利用数控(Computer numerical control,CNC)系统的外部机床坐标系偏置功能,应用自行研发的综合误差实时补偿系统进行误差在线实时补偿。该误差补偿方法综合考虑机床几何误差及其在机床不同温度下的变化,全面分析整个温升过程直至热稳态的误差及其变化规律。经检测认证表明,应用该误差补偿方法及其实时补偿系统可使机床在常温下的定位误差由44.1μm降低到3.6μm,补偿91.8%;温升之后的定位误差由26.0μm降低到5.1μm,补偿80.4%,大幅度提高机床的精度。     

数控机床热误差建模及补偿研究

数控机床的热误差是影响机床精度的关键因素,因此需要对其进行预测和补偿。首先通过多工况下的定位误差测量和进给轴测量点的温度监测,分析了进给轴温度场和热误差的分布变化特征;利用多元线性回归表征温度变化与进给轴膨胀率的定量关系从而完成热误差的预测建模,针对三轴数控立式铣床进行了热误差补偿。实验结果显示:基于修正的最小二乘法的热误差参考点预测模型更符合实际工况,与补偿前相比机床进给轴的精度提升了47.5%。     

基于状态空间模型的数控机床热误差建模

为了减小机床运行参数变化导致的机床热误差变化对模型预测精度的影响,提出了状态空间建模算法,该算法可根据机床运行参数的变化而自动调整模型,从而使模型对机床运行参数的变化具有良好的自适应性。通过实验比较了模型对机床处于不同条件下的热误差预测精度,并基于状态空间模型在Leaderway V-450型数控机床上进行了平面切削的热误差补偿实验。实验结果表明：与传统热误差建模算法相比较,所提算法的预测精度提高了58.12%,稳健性也得到了有效提升,且实际热误差补偿效果显著。     

基于实时反馈的机床热误差在线补偿模型

为建立一种能够适应机床不同工况且具有准确预测能力的热误差补偿模型,提出一种基于限定记忆递推最小二乘法辨识热误差模型参数的机床热误差预测建模方法。该方法随着机床工作状况的改变,根据实时反馈的温度和热误差数据,采用递推方法对模型参数进行即时修正,使热误差模型能够及时跟踪机床系统的热特性变化,实现以较高的预测精度对机床热误差进行补偿。通过数控车床主轴轴向热误差辨识建模及补偿实验可以看出,限定记忆递推最小二乘法比一步最小二乘法辨识精度有较大提高,最大残差值减小了52.3%,标准差减小了67%。实验结果表明,利用该方法进行机床热误差模型参数辨识具有较高的预测精度和鲁棒性,有效可行。       

数控机床进给轴综合误差解耦建模与补偿研究

为建立高精度的数控机床综合误差补偿模型,提出一种针对机床定位误差的解耦分离建模方法。通过对数控机床温度场与定位误差进行测量,研究机床在不同工况下温度场与定位误差的变化规律,基于该规律定义机床定位误差敏感度的概念,采用灰色关联度算法建立定位误差敏感度矩阵并优化了测温点。根据机床定位误差变化规律,利用多元回归和GM(1,n)算法对机床几何基准误差和热误差进行解耦分离建模,并将上述模型进行线性叠加构建机床定位误差综合模型。在不同工况条件下对一台VXC-560型加工中心进行在线补偿,试验结果表明机床x轴在冷态条件下的定位误差从11.1μm降低到4.5μm,降幅为59.5%,在热态条件下的最大定位误差由34.9μm降低到8.2μm,降幅为76.5%,并验证了采用误差模型直接驱动机床硬件进行补偿的新思路,具有一定的工程应用前景。     

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.