数控机床造型设计评价方法的研究

对造型设计评价的方法进行了系统分析,介绍了单因素模糊评价的方法,在此基础上详细分析了多因素综合评价方法和步骤,构建了数控机床造型设计评价的指标体系,运用模糊数学的基本原理实现了对数控机床造型设计的评价,其评价结论以数字的形式表达出来,结果清晰、明确,并通过具体实例对这一方法的应用进行了验证.     

基于虚拟仪器的机械部件动态特性测试

介绍一种基于虚拟仪器的机械部件动态特性测试系统，设计中采用了通过PC机增强型并口EPP来完成调整数据采集电路与PC机之间的数据传输的通讯方式，仪器不但利用了PC机强大的硬件和软件资源，提高了性价比，实现了测量结果的存储，显示；也因为它比较卡式仪器相对独立于PC机，因而也方便于对计算机硬件生疏的技术人员。连接简单，便于推广。     

新型阻尼橡胶圈的动态特性测试

利用基础激振、共振质量法设计了专用的实验系统,对新型阻尼橡胶的动态特性进行了测试,获得了阻尼橡胶刚度系数、阻尼系数以及损耗因子等特征参数值,并分析了特征参数与使用频率之间的对应关系.     

动态联盟合作伙伴评价方法的动态重构模型

基于方法相容的思想,提出了一个评价方法的动态重构模型,使其根据评价对象的不同,动态选择最优的评价方法或相容方法组合,来实现不同项目环境下的联盟伙伴选择评价;详细描述该评价方法优化模型的建立,并结合案例分析证明该评价模型的有效性.     

应变式力传感器动态特性研究及动态补偿

通过测试传感器的固有频率和冲击响应,对不同结构的应变式力传感器的动态特性进行了研究。当力传感器动态特性不理想时,根据零极点配置法设计了动态补偿数字滤波器,对力传感器进行动态补偿,使之适用于动态测量。实验表明:柱式力传感器的动态特性优于S形力传感器。通过对S形传感器进行动态补偿,拓宽了力传感器的工作频带,提高了力传感器的动态性能,减小了动态误差。     

动力机械动态工况共振幅值特性研究

动力机械转速在其范围内变化的动态工况共振幅值特性,对动力机械强度分析和试验参数设定等问题有直接影响。首先应用杜哈梅积分对动态工况激振力响应进行理论分析,发现动态工况激振力的响应无解析解,但可利用数值积分法进行仿真分析。通过仿真分析得到动力机械动态工况共振幅值随提速率的增加逐渐减小,当提速率较低时动态工况共振幅值逐渐接近稳定工况共振幅值的结论。最后利用4100 QB型柴油机扭振共振幅值和JFZ172 L型发电机结构共振辐射噪声声压级随提速率变化规律进行试验验证。     

非线性动态特性系数对汽轮机转子-轴承-密封系统运动特性的影响

为准确地反应汽流激振下汽轮机转子-轴承-密封系统的运动特性,推导了包含非线性动态特性(非线性刚度、阻尼)的转子运动微分方程,将数值模拟获得的非线性汽流激振力拟合成方程耦合到运动方程中,采用龙格-库塔法求解对应的运动方程,基于试验对比验证了考察非线性因素的必要性与运动微分方程的准确性。在此基础上,分析汽流激振力作用下不同非线性动态特性系数对转子运动特性与稳定性的影响。结果表明：系统中的非线性动态特性会改变转子不同类型的混沌运动区域与位移,使1/2、1/3、2/3工频的出现范围及幅值改变,密频现象增加;耦合热、动载荷后高负荷区域转子位移减小。对比Lyapunov指数,考虑非线性动态特性后其均值有所上升;合理的非线性刚度能够改善系统的稳定性,高非线性阻尼值能提高系统稳定性;耦合热、动载荷后的系统高负荷运行时更稳定。     

冲击环境下PBGA焊点动态特性分析

根据焊点成形理论和影响焊点可靠性因素对PCB和PBGA256组件进行有限元建模，并以此为基础对其进行模态分析及瞬态冲击动态响应分析，得出了最大应力应变在PGBA256上分布曲线；并根据实际情况简化得出焊点局部模型应变分布，从而找出焊点最易断裂失效的区域。最后，通过激光测振系统测得的实验模态和计算结果比较，表明所建立的有限元模型，可作为以后进行焊点疲劳寿命估计和焊点形态优化的基础。     

简述数控机床的主轴组件

数控机床主轴组件的工作性能对整机性能和加工质量以及机床生产率有着直接影响。由于数控机床的转速高,功率大,并且在加工过程中不进行人工调整,因此要求其具有良好的回转精度、结构刚度、抗振性、热稳定性及精度的保持性。所以主轴组件的性能是决定机床性能和技术经济指标的重要因素。     

数控机床精度评价新方法

传统的定位精度与重复定位精度等指标是在准静态下评价数控机床(CNC)性能的,无法反映数控机床在运动和加工过程中的精度。首先从数控机床的数控、伺服、机械等环节在服役态下所表现出来的性能出发,提出一种对数控机床更有针对性的,以运动精度为指标的机床精度评价新方法,通过数控指令与运动轴实际位移的符合程度即运动精度来评价机床精度,然后给出了具体的评价指标,并提出了评价指标的测量方法。分析表明,这种新的机床运动精度描述评价方法能够系统、全面地评价数控机床关键性能的优劣。最后从数控、伺服和机械角度分别阐述了影响运动精度的因素。     

Evaluation method of dynamic characteristics of whole NC machine tool

The dynamic characteristics is an important index to measure the performance of machine tools.However, there is no better method to evaluate the dynamic characteristics of whole NC (numerical control) machine tool. Through the excitation of real dynamic cutting force to the NC machine tool, the dynamic characteristics of the machine tool under the action of cutting force can be quickly obtained. In view of the fact that the cutting parameters would affect the amplitude of cutting force corresponding to each frequency component, a dynamic excitation force model was established based on the dynamic cutting forces under different sample materials and cutting parameters.The dynamic characteristics of the NC machine tool in different frequency bands could be tested by frequency band excitation. Through the finite element simulation analysis, the dynamic characteristics of NC machine tool in each frequency band was judged. The main frequency components in the vibration of machine tool were obtained by fast Fourier transform of vibration signal, which could provide guidance for optimizing the dynamic characteristics of machine tool. The dynamic stiffness of different machine tools under excitation of various dynamic cutting forces was compared to distinguish which machine tool had better dynamic characteristics. Finally, the simulation results were verified by the excitation test. The results indicate that the above method is simple and practical, and can quickly evaluate the dynamic characteristics of NC machine tool, which has certain practical value.     

Clamping effects on the dynamic characteristics of composite machine tool structures

Substituting composite structures for conventional metallic structures has many advantages for structural dynamic characteristics because composite materials have the higher specific stiffness and damping characteristics than conventional materials. However, the dynamic characteristics such as the fundamental natural frequency and damping of composite structures are influenced much by their joints. In this work, the effects of clamping conditions on the dynamic characteristics of cantilever type composite machine tool structures with clamped joint were investigated to increase the natural frequency and damping of structures. In order to improve the shear property of the clamping part of composite machine tool bar, a new method for the clamping part was developed with metal core or sleeve inserted in the composite body at the clamping part. From the finite element and experimental results, suitable clamping conditions for the maximum dynamic stiffness were obtained for the composite structures with clamped joint.     

基于CSO-SVM的数控机床主轴热误差建模

针对数控机床多热源所致的温升与主轴热误差之间复杂的非线性关系问题,提出一种鸡群优化（chicken swarm optimization, CSO）算法与支持向量机（support vector machines, SVM）相结合的主轴热误差预测模型（以下简称热误差模型）。以某精密数控机床的主轴单元为研究对象,采用五点法对其在空转状态下的轴向热变形进行测量,并借助热电偶传感器对机床的4个关键温度测点的温度进行采集。以SVM为理论基础,随机选取75%的数据样本进行训练,进而构建主轴热误差模型。其中,利用CSO算法优化SVM模型的惩罚参数c和核参数g,以提升热误差模型的预测能力及鲁棒性。以余下的25%的样本作为测试数据集,对所得热误差模型进行验证。利用CSO-SVM模型对不同工况下主轴的热误差进行预测,并将预测结果与测量结果进行对比。结果表明：当主轴转速为3 000 r/min时,CSO-SVM模型的平均预测精度高达97.32%,相较于多元线性回归模型和基于粒子群优化的SVM模型分别提升了6.53%和4.68%;当主轴转速为2 000, 4 000 r/min时,CSO-SVM模型的平均预测精度分别为92.53%、91.82%,表明该模型具有较高的预测能力和良好的鲁棒性。CSO-SVM模型具有较强的实用性和工程应用价值。     

WA-21M数控系统数控化改造XA5032铣床

机床数控化改造可大大提高设备的自动化能力和生产率水平,满足企业对生产设备更高的要求。通过对XA5032铣床改造方案分析和进给传动系统的设计计算,应用WA-21M数控系统,完成铣床的数控化改造。阐述了数控系统的选配原则及选配方案、伺服电机的选择与电气系统的数控化改造方案,分析了系统控制软件的组成和工作原理。机床改造后,机床精度在X,Y,Z向步进精度为0.005,0.005,0.01 mm/setp;轴向定位精度为0.015 mm;重复定位精度为0.008 mm。改造后加工精度和生产率有较大提高,改造取得成功,为提高企业数控化率提供了一条切实可行的途径。     

基于并行计算的三自由度并联机床动力学解析模型

基于运动学分析、凯恩动力学方程和数字-符号方法,建立了三自由度并联机床的动力学解析模型.将广义坐标、构件的质量和转动惯量处理为符号量.将动力学模型矩阵的推导问题转化为特定条件下运用运动学和动力学计算公式求解驱动力的问题,由计算机自动生成动力学模型矩阵中的各元素的实时代码.文中引入了一种新的标量矩阵与矢量矩阵的乘法运算,研究了广义坐标和构件的质量对驱动力的影响规律.构造了动力学解析模型的并行算法,节省了计算时间.给出了动力学模型矩阵元素的实时代码生成和驱动力矩与参数关系的具体数值实例.     

Research on reliability allocation technology for NC machine tool meta‐action

The reliability of machine tool is getting more and more attention. Reasonable reliability allocation is beneficial to improve the inherent reliability of machine tool. However, the existing reliability allocation methods for machine tool have some limitations. For example, static part is selected as the reliability allocation object of machine tool, which cannot reflect the characteristics “function realized by motion”; factors affecting reliability allocation are not considered comprehensively, weights of experts are treated as the same, and the allocation results are not optimized or the impact of time on enterprise is neglected in the optimization. To solve these problems, a new multiobjective optimization reliability allocation method for machine tool is proposed in this paper. Firstly, the latest achievements about meta‐action are given, and meta‐action is set as the reliability allocation object. Secondly, more reasonable and comprehensive factors affecting reliability allocation are extracted. Thirdly, expert weight coefficient is brought to reduce the subjective impact of expert scoring. Fourthly, time factor is brought to make the optimized allocation results more reasonable and accurate. Finally, a numerical control (NC) machine tool made in China is taken as an example, with a comparison on the reliability allocation results of current methods and proposed method. The results verify the applicability, rationality, and accuracy of the proposed method, which lays a foundation for the subsequent study on the quality characteristics of machine tool based on meta‐action.     

新型数控雕刻机运动控制系统设计

为解决传统雕刻机数控内核封闭而导致加工对象受局限的问题,将新型数控雕刻机运动控制系统采用NC嵌入PC型开放式构架,把PC机的海量运算能力与运动控制器实时控制能力有效结合起来．上位机PC利用VC调用运动控制器的动态链接库函数实现了加工过程智能化控制、CAD/CAM集成等人机交互功能,下位机利用GE-400-SV运动控制器的强大的实时控制能力实现了雕刻机的三轴联动伺服、高速电主轴控制以及硬件层智能安全保护．该控制系统为提升数控雕刻机的系统集成化程度和柔性加工能力提供了一条有效解决途径．     

并联机床的动力学特性对加工精度影响的分析

为了提高并联机床的加工精度,分析了并联机床的动力学特性对加工精度的影响。根据牛顿—欧拉方程,得到并联机床的动力学方程,解得连杆的驱动力;根据杆件轴向伸长量与受力之间的关系,得到连杆的长度误差;以无长度误差的连杆长度为优化目标,用优化的方法,得到动平台的位姿,并与连杆有长度误差时动平台的位姿比较,得动平台的位姿误差;根据刀具在动平台坐标系中位置,得刀具加工位置误差及对被加工零件精度的影响。结果表明：并联机床连杆的长度误差,引起刀具加工位置误差,使被加工零件产生形位误差和尺寸误差;并联机床电主轴偏心引起连杆的长度误差的扰动,产生刀具加工位置的扰动误差,影响被加工零件的表面粗糙度。     

Simulation of random tool lives in metal cutting on a flexible machine

Much research into multi-level lot-sizing problems has concentrated on fixed horizon problems ignoring more realistic conditions such as appending new demand(s) in the planning periods. The aim of this paper is to illustrate that a heuristic, which was developed earlier by the authors, is applicable to the multilevel lot-sizing problem with a bottleneck under a rolling schedule environment. The results illustrate that the Silver-Meal (SM) approach performed better than the Economic Order Quantity (EOQ) approach in terms of cost measures, when incorporated within the heuristic procedure. The results also show that, although the total cost of the problem is increased in a rolling schedule environment, the heuristic continues to perform favourably in producing low cost solutions.     

A dynamic method for the production lot sizing with machine failures

This paper presents a dynamic method to deal with two economic lot sizing models with exponential machine failures. Its main difference from the static method is that the machine failure is separately treated from the perspective of failure realisation. The optimal lot size is derived through the equation between the incurred average cost and the marginal cost, which has to be performed for each lot due to the random failures. In the first no-resumption model, the simulation shows that two methods have the similar performance as the lot number increases. For the resumable model, we propose a zero-inventory resumption policy that always resumes the production after each machine failure but delays the resumption until the on-hand inventory is depleted. The simulation result indicates that the new policy by the dynamic method outperforms the initial abort/resume policy, and it also shows the convergence as the production continues.