Statistical point cloud model to investigate measurement uncertainty in coordinate metrology

In this work an approach to investigate measurement uncertainty in coordinate metrology is presented, based on fitting Gaussian random fields to high-density point clouds produced by measurement repeats. The fitted field delivers a depiction of the spatial distribution of random measurement error over a part geometry, and can incorporate local bias information through further measurement or with the use of an external model to obtain a complete, spatial uncertainty map. The statistical model also allows the application of Monte Carlo simulation to investigate how error propagates through the data processing pipeline ultimately affecting the determination of features of size and the verification of conformance to specifications. The proposed approach is validated through application to simulated test cases involving known measurement error, and then applied to a real part, measured with optical and contact technologies. The results indicate the usefulness of the approach to estimate measurement uncertainty and to investigate performance and behaviour of measurement solutions applied to the inspection and verification of industrial parts. The approach paves the way for the implementation of automated measurement systems capable of self-assessment of measurement performance.     

动态模拟试验技术在汽车结构动强度分析中的应用

远程参数控制技术日益成为汽车台架模拟试验不可缺少的技术手段。以轿车车身为研究对象，利用远程参数控制技术实现了在实验室内对实际道路行驶状况的复现，并且对两种载荷作用下的试验数据数据进行分析对比，由此对汽车结构动强度模拟试验技术进行了研究和探索。     

Bayesian spatial defect pattern recognition in semiconductor fabrication using support vector clustering

Defects generated during integrated circuit (IC) fabrication processes are classified into global defects and local defects according to their generation causes. Spatial patterns of locally clustered defects are likely to contain the information related to their defect generation mechanisms. In this paper, we propose a model-based clustering for spatial patterns of local defects to reflect real situations. A flexible two-step approach is proposed to classify the spatial defects patterns via support vector clustering and Bayesian method. Support vector clustering is employed to separate global defects from the local ones to improve both clustering accuracy and computational efficiency in further analysis. A new mixture model is proposed for modeling the distribution of local defects on the wafers. Local defect clusters with amorphous/linear, curvilinear, and ring patterns are modeled by multivariate normal distribution, principal curve, and spherical shell, respectively. A Bayesian inference procedure is then applied for parametric pattern recognition of the local defects. Results from both simulated data and real wafer map data demonstrate potential in applying our approach to analyze general defect patterns in IC manufacturing.     

汽车台架耐久性试验与道路试验相关性探讨

在汽车耐久性试验中,等幅试验是最快速、最简单的方法,而应用路谱的随机加载试验是最复杂的方法。本文应用局部应力一应变法、雨流统计、Neuber法则等损伤原则计算了某车型前鼓包处随机和等幅疲劳试验结果与汽车试验场之间的关系。计算结论：应用等幅试验和适当的疲劳分析也可以给出很有价值的结果。     

非高斯随机振动试验并行控制策略研究

针对非高斯随机振动试验控制中功率谱均衡与峭度均衡相互干涉,影响控制精度的问题,提出非高斯随机振动试验并行控制策略。在提出整个系统控制流程的基础上,分别给出功率谱均衡控制算法和峭度均衡控制算法。对蕴含峭度信息的随机信号产生机理展开研究,先给出信号产生的流程图,然后推导出符合控制系统要求的随机信号设计参数。利用功率谱设计滤波器,通过卷积运算调制出用于系统控制的驱动信号。仿真与试验结果表明,采用非高斯随机振动试验并行控制策略进行系统控制,其输出响应谱与参考谱的误差完全满足工程中常用的±3 dB控制要求,峭度控制也达到很高的精度,满足工程试验要求,从而验证该控制策略的有效性。     

Wide roller guide machining by four-axis machine tools for cylindrical cams

The dynamic interaction between different machine tool subsystems can be exploited to increase the machine cutting performance. Simplified models are proposed to define useful guidelines that maximize the material removal rate in milling processes in different industrial situations. Two different cases are presented: in the first one, the machine influence on spindle dynamics is considered and optimized. In the second case, the interaction between the control system and the machine tool mechanical structure is analyzed, suggesting control tuning criteria that maximize cutting process stability. The procedure is applied to a real industrial case: a five-axis machine tool with a bi-rotative head. Moreover, requirements for the applicability of the proposed approach are investigated and described by analytical formulas.     

基于需求模型的航天软件测试用例生成方法

为了提高航天软件测试的效率和覆盖率,增加航天软件测试的有效性,提出了一种基于需求模型的软件测试用例设计方法。针对航天软件测试的特点,该方法采用从用例层深入至步骤层的测试优化策略。首先,基于元建模方法定义了一种测试需求模型;通过建立模型,将测试需求加以拆分,获取了测试需求之间的先后依赖关系以及测试需求与测试步骤之间的对应关系。然后,基于测试需求模型,构建了测试需求的路径图,进而通过对图的遍历获得了测试用例。最后,将该方法用于工程实践进行了实验验证。验证结果表明,该方法有效保证了测试活动的充分性和有效性,降低了测试用例约简的风险。与不约简的测试方法相比,该方法减少测试工作量达18%,减少测试用例数量为40%以上,软件测试的执行时间也减少了40%以上,在满足需求覆盖率的同时,有效提高了测试效率。     

采用光纤光栅传感器测量模型材料应变的原理和应用

应变是材料与结构的重要物理特性,最能反映结构局部特性,是材料和工程结构健康监测最为重要的参数。对材料应变测量,可以预知局部荷载的状态。光纤传感器具有灵敏度高、响应速度快、电磁兼容性强、无零漂、可靠性高、使用寿命长等特点。光纤光栅应变传感器是一种极具发展潜力和应用价值的应变传感器。研究了光纤光栅应变传感器的传感原理、应变传递规律及其在模型试验相似材料应变测量中的应用,测量得到的应变历程与实际物理过程相一致。     

混合单频激励下连续扫描激光多普勒振动测试

提出了一种混合单频激励下激光连续扫描振动测试方法,提高了连续扫描激光多普勒振动测试效率。首先,基于单频激励下连续扫描激光多普勒振动测试的原理,研究了混合单频激励下连续扫描激光多普勒振动测试技术,提出了适合混合单频激励的结构工作变形提取方法;其次,通过仿真测试,从理论上验证了方法的有效性;最后,以悬臂梁结构为例,进行了连续扫描和离散点扫描测试的试验验证。结果表明,混合单频激励下的连续扫描激光振动测试及分析方法可准确获得结构工作变形,具有效率高、空间分辨率高等优点,对进一步的工程应用具有实用价值。     

某轿车前副车架服役载荷模拟试验加速方法研究*

服役载荷模拟试验能准确地预测零部件的疲劳寿命。为节省试验时间,急需开发出一套合理、实用的加速试验方法。重点研究在不具备结构局部应变响应,仅具备外部激励载荷如力、位移、和加速度等情况下的试验加速方法。基于修正Miner准则,以伪损伤保留比例作为小载荷删除准则,并结合疲劳数据编辑(Fatigue data editing, FDE)技术,提出一套便于工程应用的服役载荷模拟试验加速方法。以某轿车前副车架的疲劳试验为例,分别编制伪损伤保留比例为99%、95%和90%的加速谱。综合考虑各加速谱的载荷特征和加速效果,选用95%加速谱、90%加速谱和原始谱分别建立台架试验。试验结果表明两种加速谱在有效节省试验时间的同时,均获得了与原始谱相同的试验结果,且90%加速谱的加速试验效果更为显著。本方法便于工程应用,可为其他汽车零部件的服役载荷模拟试验提供参考。     

A procedure for the wear prediction of collector strip and contact wire in pantograph–catenary system

The effects of friction and electrical phenomena like arcing and sparking govern the wear rate in the sliding contact between the contact wire and the collector strip, these two effects are mutually interconnected in a complex manner. A means of investigating the wear of the collector strip and the contact wire is to carry out laboratory tests that allow to perform comparative tests between different material combinations and to establish the dependence on the main parameters such as sliding speed, contact force and current intensity. A problem to be considered in the application of the laboratory test results is their extrapolation to the real operating conditions, in order to assess the effective benefit among different solutions. In this paper, a procedure that combines a wear model for the contact between collector strip and contact wire with the simulation of the dynamic interaction between pantograph and catenary is proposed. The adopted wear model is based on the wear map concept, including the effect of electrical current flow, and it is tuned by means of the results obtained on laboratory test rig.The dependence of the electrical contact resistance on the contact force between each contact strip of the pantograph and the contact wire of the overhead line is considered and the corresponding electrical current on each of the two collectors of the pantograph is evaluated. Instantaneous values of contact forces and electrical current are then fed into the wear model and the amount of the wear of the collector strips and of the contact wire along the overhead line is calculated, generating an irregular profile of the contact wire.The proposed procedure is applied to two cases: in the first one the wear of the contact wire using copper collector strips and graphite collector strips for dc line are compared. In the second one, the consequence of the variation of the mechanical tension of the contact wire on the wear levels is predicted.     

TOOL LIFE PREDICTION USING RANDOM WALK BAYESIAN UPDATING

According to the Taylor tool life equation, tool life reduces with increasing cutting speed. The influence of additional factors can also be incorporated. However, tool wear is generally considered a stochastic process with uncertainty in the model constants. In this work, Bayesian inference is applied to predict tool life for milling/turning operations using the random walk/surface methods. For milling, Bayesian inference using a random walk approach is applied to the well-known Taylor tool life model. Tool wear tests are performed using an uncoated carbide tool and AISI 1018 steel work material. Test results are used to update the probability distribution of tool life. The updated beliefs are then applied to predict tool life using a probability distribution. For turning, both cutting speed and feed are considered. Bayesian updating is performed using the random surface technique. Turning tests are completed using a coated carbide tool and forged AISI 4137 chrome alloy steel. The test results are applied to update the probability distribution of tool life and the updated beliefs are used to predict tool life. While this work uses the Taylor model, by following the procedures described here, the technique can be applied to other tool life models as well.     

基于非齐次泊松过程和统计仿真的故障样本模拟生成

由于测试性虚拟试验具有成本低、效率高、风险小、故障注入受限少等优点,故障样本量几乎不受限制,可有效弥补测试性实物试验的不足,但同时也对故障样本生成提出新的要求。为此提出一种适用于测试性虚拟试验的基于非齐次泊松过程和统计仿真的故障样本模拟生成方法。分析指出可修系统的故障发生过程是随机过程,并用非齐次泊松过程及其参数化模型对其进行数学描述。给出故障样本模拟生成流程,建立故障事件发生间隔时间的概率分布函数,通过随机数生成和逆变换法,实现故障样本的模拟生成,仿真获得故障发生次数及其相继发生时间。以某型地平仪为案例进行试验和应用研究。试验结果表明,采用所提方法进行故障样本模拟生成是有效的,能科学指导可修系统测试性虚拟试验中的故障注入。     

Parallel Test Tasks Scheduling and Resources Configuration Based on GA-ACA

A Genetic Algorithm-Ant Colony Algorithm(GA-ACA),which can be used to optimize multi-Unit Under Test(UUT)parallel test tasks sequences and resources configuration quickly and accurately,is proposed in the paper.With the establishment of the mathematic model of multi-UUT parallel test tasks and resources,the condition of multi-UUT resources mergence is analyzed to obtain minimum resource requirement under minimum test time.The definition of cost efficiency is put forward,followed by the design of gene coding and path selection project,which can satisfy multi-UUT parallel test tasks scheduling.At the threshold of the algorithm,GA is adopted to provide initial pheromone for ACA,and then dual-convergence pheromone feedback mode is applied in ACA to avoid local optimization and parameters dependence.The practical application proves that the algorithm has a remarkable effect on solving the problems of multi-UUT parallel test tasks scheduling and resources configuration.     

飞机外挂物新型振动试验夹具研究

振动试验是考察飞机外挂物是否满足挂飞条件的重要试验项目,有科学合理的试验夹具才能准确模拟外挂物的实际挂飞状态。针对国内现有振动试验方法的不足,文中提出了一种新型试验夹具,并采用该夹具和传统刚性夹具对吊舱进行了随机振动仿真分析,最后将仿真结果与挂飞实测结果进行了对比分析。结果表明,新型夹具模拟出的振动环境更加逼近真实挂飞情况。该新型振动夹具弥补了国内现有试验夹具的不足,为行业内振动夹具乃至试验方法的改进探索出了一种新的可行方案。     

Adaptive PIV algorithm based on seeding density and velocity information

An adaptive particle image velocimetry (PIV) processing algorithm to increase local spatial resolution and obtain accurate results is presented. Adaptive sampling criterion is based on seeding density and the analysis of velocity information. The proposed methodology places more measurement points in the region where high seeding density exists or flow parameters vary drastically. This methodology is effective in PIV image processing, especially in non-optimal PIV experimental conditions. The working principle of the adaptive processing method in this paper is to generate spring force on the bias of the deviation between the ideal and actual distances of measurement points. Under artificial force, the sampling points are moved to desirable places to satisfy sampling density function. Sampling density function is important in processing and ingeniously conceived based on the combination of vorticity and velocity gradients. The viability of the method is elaborated through synthetic and experimental tests. The synthetic test verifies the effectiveness of the adaptive processing on the basis of flow information. The bias and random error can be reduced by 7.3% and 4.0%, respectively. The result of the experimental test shows that the sampling points and the interrogation window size can be arranged according to the spatial distribution of seeding density and the actual flow features. Compared with iterative window deformation method, spatial resolution is locally enhanced, and the robustness and reliability of the result are increased, particularly in poor seeding regions.     

汽车磁流变悬架垂直振动控制与试验研究

在对整车振动系统进行分解和简化的基础上,提出一种分级智能控制系统,设计了用仿人智能思想来在线修改模糊控制器参数的1/4车磁流变悬架振动模糊自适应局部控制器,设计了整车悬架垂直振动的协调控制规则用于调整4个局部控制器的输出值。在MATLAB平台上对分级控制系统进行仿真,构建了磁流变悬架系统垂直振动的整车测控与评价系统,在不同条件下进行了道路试验。相对于被动悬架,分级控制的磁流变悬架使汽车底板振动加速度下降了约15％,使座椅振动加速度下降了约23％,表明用分级控制来减小磁流变悬架系统的垂直振动是可行的,可降低因模型的简化带来的影响,提高汽车的平顺性。     

置信对比检验理论

提出两母体特征值(如均值、方差、变异系数、百分位值和百分率等)置信对比检验理论,该理论包括强对比检验和弱对比检验两种方法,能够满足不同工程对比检验的需求。传统对比检验属于一种假设检验,依据的是“小概率原则”,而置信对比检验则事先不作任何假设,依据的是“大概率原则”。所以,置信对比检验能够以高概率确认两母体特征值之间的大小和比例关系,大大提高对比检验精度,克服了传统对比检验当接受原假设时仅仅意味着不拒绝原假设的缺点。文中详细给出两正态母体均值、方差、变异系数、百分位值和百分率的置信对比检验方法及其步骤,特别是两母体百分位值和百分率的置信对比检验方法解决了长期以来工程上急需而传统方法又未能解决的难题。此外,还提出两正态母体变异系数比值及百分位值之差的置信限估计量,并建立相应的置信对比检验简便方法。     

An identification method for joint structural parameters using an FRF-based substructuring method and an optimization technique

A new method is proposed to identify the joint structural parameters of complex systems using a frequency response function (FRF)-based substructuring method and an optimization technique. The FRF method is used to estimate the joint parameters indirectly by minimizing the difference between the reference and calculated responses using a gradient-based optimization technique with analytical gradient information. To assess the robustness of the identification method with respect to noisy input data, FRFs contaminated by uniformly distributed random noise were tested in a numerical example. The effects of the random noise and the magnitude of the connection stiffness values on the accuracy of the method were investigated while identifying the joint parameters. When the FRFs were contaminated with random noise, the proposed procedure performed well when used to identify the stiffness values, but the accuracy of identification is deteriorative when used to identify the damping coefficients. The joint parameters of a real bolted structure were also identified by the proposed method. The results show that it can be applied successfully to real structures, and that a hybrid approach using both calculated and measured FRFs in the substructure model can enhance the quality of the identification results.     

射线图象的自适应增强算法研究

在现代无损检测技术中,图象处理技术用来定量或定性分析和发现设备的故障,并得到了普遍应用。本文根据射线图角的特点,介绍一种在实时成象检测中,对所得的图角进行空间域自适应对经度增强的算法,试验表明,该算法实时性好,能使原图象中较模糊、对比度差的细节得到明显的增强。同时根据以变换的多分辨率特性,在小波域也进行了尝试。