三次指数平滑法预测管道腐蚀速率的应用

为准确预测管道腐蚀速率并得到精度较高的腐蚀速率预测模型,采用已有统计数据作为研究对象。首先,采用三次指数平滑法,建立管道腐蚀速率预测模型,对腐蚀速率数据进行拟合与预测分析;然后,得出预测模型中最合理的权重系数α;最后,通过与一次指数平滑法、二次指数平滑法进行对比分析,得出了三次指数平滑法预测精度较高,预测值与实际值相符合的结论。结果表明,三次指数平滑法预测模型符合管道腐蚀速率的特点,对有效预测管道腐蚀具有一定的参考价值和指导意义。     

镁合金轮毂中心浇注式挤压铸造工艺优化

以镁合金汽车轮毂为例,建立铸件三维模型,设计铸造工艺方案,运用CAE技术预测铸造缺陷,从而改进了铸造工艺。结果表明:对于镁合金轮毂中心浇注式挤压铸造工艺,应将螺栓孔填平,并尽量采用大尺寸浇口充型,以实现平缓顺序充型和顺序凝固,保证得到高品质的镁合金轮毂。     

弧齿锥齿轮齿顶倒棱锥形砂轮加工方法研究

为了实现弧齿锥齿轮齿顶倒棱高效加工,提出一种基于锥形砂轮的倒棱方法。建立弧齿锥齿轮和锥形砂轮的实体模型,以砂轮沿垂直于面锥方向切入最大深度为原则,采用实体接触分析方法,确定砂轮与齿轮的空间运动关系。基于空间运动关系完成倒棱仿真加工,仿真结果表明:该方法可同时加工两侧齿顶,加工效率较高且在通用五轴加工中心上即可实现。为了评价倒棱效果,提出一种倒棱效果的定量测量方法,在倒棱仿真模型上选定的多个测量位置,测量倒棱效果并与理论模型进行比较,依据比较结果可确定砂轮锥角的优化值。     

基于神经网络的铝合金汽车轮毂低压铸造工艺优化

以浇注温度、模具初始温度、浇注速度、铸造压力、浇注方式作为输入层函数,以力学性能作为输出层函数,采用5×30×1的三层拓扑结构构建了铝合金汽车轮毂低压铸造工艺神经网络优化模型,并对其进行了训练、预测验证和产线应用。结果表明,铝合金汽车轮毂低压铸造工艺神经网络优化模型具有较强的预测能力,精度较高,相对预测误差2.87%～4.31%,平均相对误差值为3.48%。神经网络优化工艺使试样的抗拉强度、屈服强度比产线原工艺分别增大了7.1%和6.9%,力学性能得到了显著提升。     

高阶劳厄点标定的新方法

通常标定高阶劳厄点位置时,首先预测该点的倒易矢量指数作为试标矢量,然后通过计算其在两个零层倒易矢量上的分量来对试标矢量进行验证,计算过程比较复杂。本文提出两种简便方法,可以迅速地对试标矢量进行验证;同时,为便于预测高阶劳厄点的倒易矢量指数,提出一个计算d值超差的近似公式。     

A NEW INDEXING METHOD FOR HIGH ORDER LAUE POINTS

通常标定高阶劳厄点位置时,首先预测该点的倒易矢量指数作为试标矢量,然后通过计算其在两个零层倒易矢量上的分量来对试标矢量进行验证,计算过程比较复杂。本文提出两种简便方法,可以迅速地对试标矢量进行验证;同时,为便于预测高阶劳厄点的倒易矢量指数,提出一个计算d值超差的近似公式。     

基于回归正交设计的快速成型件质量预测

以方形件为实验对象建立了尺寸偏差与5个工艺参数之间的关系模型;并根据该模型,对以方形为主要特征的按键导座进行了尺寸偏差预测,预测结果与实验值非常接近,这说明该关系模型是合理的,可以用来预测其他方形件的质量。     

铝合金轮毂低压铸造中的缺陷预测及模具优化

低压铸造工艺生产出的汽车铝合金轮毂具有尺寸精度高、充型平稳以及铸件质量高等特点,但是铸件中也存在缩松缺陷。针对汽车铝合金轮毂在低压铸造条件下,出现的缩松以及缩孔等缺陷的现象,应用数值模拟技术进行了缺陷预测以及模具优化。     

基于STL分解的平均故障间隔时间组合预测

由于影响数控机床刀架系统平均故障间隔时间的因素较多,采用单一的模型作预测无法充分提取已知数据中的隐含信息,导致预测困难。应用基于STL进行时间序列分解的组合模型预测算法,将原始故障数据分解为趋势项、季节项和随机项,应用指数平滑法和支持向量机回归分别对前两项数据进行预测,根据时序分解的加法模型将其结合,得到组合模型预测结果,并将组合模型与单一的预测模型进行对比分析。实例证明:组合模型预测优于单一模型预测。此方法应用于MTBF的预测,有助于工作人员针对故障发生时间点提前采取措施,同时为数控机床可靠性评估提供了新的研究方法。     

不同材料模型和测量方法对冲压回弹预测精度的影响

针对回弹预测的精度问题,首先以帽形件为例,通过对3种材料模型:36#材料模型、37#材料模型、125#材料模型以及两种不同的测量方法:惯性释放法、节点约束法进行组合,对其回弹值进行预测.再与实际回弹值进行对比,试验得出了与实际回弹结果重合度最高的最优材料模型和测量方法的组合.将此组合应用到汽车车门外板零件的回弹模拟上,...     

Prediction of metal futures price volatility and empirical analysis based on symbolic time series of high-frequency

The metal futures price fluctuation prediction model was constructed based on symbolic high-frequency time series using high-frequency data on the Shanghai Copper Futures Exchange from July 2014 to September 2018, and the sample was divided into 194 histogram time series employing symbolic time series. The next cycle was then predicted using the K-NN algorithm and exponential smoothing, respectively. The results show that the trend of the histogram of the copper futures earnings prediction is gentler than that of the actual histogram, the overall situation of the prediction results is better, and the overall fluctuation of the one-week earnings of the copper futures predicted and the actual volatility are largely the same. This shows that the results predicted by the K-NN algorithm are more accurate than those predicted by the exponential smoothing method. Based on the predicted one-week price fluctuations of copper futures, regulators and investors in China’s copper futures market can timely adjust their regulatory policies and investment strategies to control risks.     

Corner rounding of linear five-axis tool path by dual PH curves blending

The widespread linear five-axis tool path (G01 blocks) is usually described by two trajectories. One trajectory describes the position of the tool tip point, and the other one describes the position of the second point on the tool axis. The inherent disadvantages of linear tool path are tangential and curvature discontinuities at the corners in five-axis tool path, which will result in feedrate fluctuation and decrease due to the kinematic constraints of the machine tools. In this paper, by using a pair of quintic PH curves, a smoothing method is proposed to round the corners. There are two steps involved in our method. Firstly, according to the accuracy requirements of the tool tip contour and tool orientation tolerances, the corner is rounded with a pair of PH curves directly. Then, the control polygon lengths of PH curves are adjusted simply to guarantee the continuous variation of the tool orientation at the junctions between the transition curves and the remainder linear segments. Because the PH curves for corner rounding can be constructed without any iteration, and those two rounded trajectories are synchronized linearly in interpolation, which makes this smoothing method can be applied in a high efficiency way. Its high computational efficiency allows it to be implemented in real-time applications. This method has been integrated into a CNC system with an open architecture to implement on-line linear five-axis tool path smoothing. Simulations and experiments validate its practicability and reliability.     

大型风机状态趋势随机建模与预测

风机状态监测时间序列大多是变均值非平稳随机序列。本文采用指数平滑建模与预测,并调整权值后,可获得去均值后的平稳随机序列,再经自回归ＡＲ（ｎ）建模与预测,可以明显提高预测精度。     

Active integration of tool deflection effects in end milling. Part 2. Compensation of tool deflection

This study presents a compensation method in milling machining in order to take into account tool deflection during tool-path generation. Tool deflection that occurs during machining, and especially when flexible tools such as end mills are used, can result in dimensional errors on workpieces. The study presented here is part two of a two-part paper. In part one the cutting force models and the surface prediction method have been presented.Here the focus is on tool deflection effects' integration during the generation of the tool path. A strategy is proposed that modifies the nominal tool trajectory, compensates for the machining errors due to tool deflection, without degrading the production performance and the machined accuracy. The methodology allows optimization of the tool path trajectory in order to achieved a specified tolerance. Some experimental results are presented.     

水下机械臂电动静液作动器的模型预测控制

电动静液作动器(EHA)作为水下液压机械臂的作动系统具有诸多优势。为提高EHA的控制性能,采用基于卡尔曼滤波的模型预测控制(MPC)方法,为提高预测效率,MPC的预测模型采用线性化的EHA模型。在Simulink环境中实现水下机械臂EHA的MPC控制,并与PID和滑模控制(SMC)进行对比。仿真结果表明：MPC的位置跟踪稳态误差约为SMC的10%~24%,为PID的3%~37%;出现负载扰动之后,MPC的平均受扰偏差仅为SMC的31%~66%,为PID的3%~48%;随着油液弹性模量的降低,3种控制方法下的受扰偏差均呈上升趋势,但MPC的上升趋势更加平缓,平均偏差值也较低。这表明MPC控制方法具有更高的位置跟踪精度和更强的鲁棒性。     

Application of fuzzy logic for modeling surface roughness in turning CFRP composites using CBN tool

In recent days, carbon fiber reinforced polymer (CFRP) composites play a vital role in various engineering and technological applications. They are replacing conventional materials due to their excellent properties. Tubes made of these materials are made up of either hand layup process or filament winding processes and are widely used in aircraft, automobile, sports industries, etc., The objective of this study is to examine the influence of machining parameters combination so as to obtain a good surface finish in turning of CFRP composite by cubic boron nitride (CBN) cutting tool and to predict the surface roughness values using fuzzy modeling. The results indicate that the fuzzy logic modeling technique can be effectively used for the prediction of surface roughness in machining of CFRP composites.     

机械故障指数平滑预测的实验分析

指数平滑预测方法由于采用对时间序列加权平滑（平均）和非线性预测模型，而且计算简单方便，因此适用于车间现场机械故障预测。本文通过对滚动轴承的实验研究，分析了预测中权的选择和预测误差。     

Five-axis tool orientation smoothing using quaternion interpolation algorithm

In five-axis machining, abrupt changes of tool axes may deteriorate the part surface, hence smoothing of tool orientations becomes an important issue. In the present tool path generation procedure, the tool orientation smoothing method (TOS method) is coupled with the cutting error improvement method (CEI method). TOS method is used to smooth tool orientations in order to reduce cutting errors and increase the machining efficiency. CEI method modifies existing cutter location data (CL data) so that final cutting errors are kept within the required tolerance. Experimental results show that the tool paths generated by the present procedure have better machining efficiency, better surface quality, and no interferences between the tool and part surfaces.     

华法林PPK/PD模型与多元回归法剂量模型的预测准确度比较

目的：比较华法林PPK/PD模型与多元线性回归法建立的6个剂量模型的预测准确度，以期为华法林PPK/PD模型的临床应用提供参考。方法：收集本院使用华法林钠片口服抗凝治疗的住院患者的相关临床资料，分别用PPK/PD模型与其他6个模型模拟预测值。利用SPSS 23.0软件进行实测值与预测值的配对t检验，采用平均预测绝对偏差和预测偏差百分比两个评价指标并绘制预测偏差箱式图并从数据总体、不同剂量组、不同基因型组分别比较。结果：研究共纳入50例患者，7个模型中，只有PPK/PD模型、Wen等人模型和都丽萍等人模型的预测值与实测值无统计学差异（P>0.05）。PPK/PD模型的预测准确度在总体数据、低中剂量、不同基因型患者间的预测准确度更高。Wen等人模型和李传保等人模型在高剂量组中的预测准确度较高。结论：华法林PPK/PD模型临床预测性能良好，可望为华法林精准给药提供参考。