加工中心触发式测头在线检测的实现

介绍了加工中心在线检测系统的组成、工作原理和工作过程.对测头的工作原理以及BLUM测头测量循环的功能和使用方法进行了介绍.该系统可实现测量程序自动生成以及测量结果软件补偿.引入微机使得测量程序编写由原来复杂的手工编写转变为微机交互界面操作,并使复杂的综合误差补偿成为可能.     

Development of a touch probe based on five-dimensional force/torque transducer for coordinate measuring machine (CMM)

Systematic errors due to the pre-travel variation and the probe tip shape are irreducible to the traditional touch trigger probing systems. This paper describes the development of a probing system based on five-dimensional force/torque transducer for coordinate measuring machines. The compensation for pre-travel variation is accomplished through the five-dimensional force/torque information acquired by the integrated transducer and the stiffness matrix of the stylus. From the relationship between the obtained force/torque information and the geometrical shape equation, coordinates of the exact contact point immune from the contact error are acquired. After calibration, the combined measurement uncertainty is estimated to be less than ±0.3 μm.     

Autonomous robot calibration using a trigger probe

This paper presents a new robot autonomous calibration method using a trigger probe. The robot grips a simple probe (which was manufactured as a standard end-effector tool) automatically to touch constraint planes in a workspace (the locations of the constraint planes are not necessarily known exactly). The robot internal sensor measurements are recorded for kinematic calibration while the tip-point of the probe is in contact with the constraint plane. The kinematic constraint conditions are obtained from the known shape of the constraint surface, rather than from the measured reference locations in a workspace. The new method eliminates any use of external measuring devices for robot end-effector location measurements for robot calibration; thus it is suitable for a periodic robot re-calibration in a shop-floor environment. Both simulation and experimental results for a six degree-of-freedom (DOF) PUMA robot are given in this paper. The evaluation results using an external precision measuring device — Coordinate Measuring Machine(CMM) — are also presented.     

一种改进的数控机床工件坐标找正方法

测头测量存在随机误差,采用二点确定直线的方法进行坐标找正会带来较大误差,本文针对常用的测量垂直坐标系找正方法提出了一种改进算法,通过分别测量一组数据,采用最小二乘法拟合直线,可以较好的减小随机误差影响,得到更精确的坐标结果。     

Improving error compensation via a fuzzy-neural hybrid model

Factors that influence the accuracy of machining and in-cycle measuring processes are varied. It is very difficult or impossible to identify and fix each error by in-cycle measuring systems with touch trigger probes. Moreover, even where errors have been determined, the effects and relationships among them are very complicated, and there are no existing mathematical models to be applied to control or compensate the machining processes. This paper introduces a new in-cycle measuring and error compensation system based on a fuzzy controller combined with a supervised neural network. The fuzzy neural hybrid compensation model consists of a multilayer feed-forward neural network trained with the back propagation gradient descent algorithm. The fuzzy rules are implemented by the hidden layer of the network, and the fuzzy max-min operations are replaced by the feed-forward summation. The proposed system reveals that it is feasible to achieve an improved machining performance by adapting the fuzzy membership functions and generating linguistic control rules. A series of experiments is performed, and the characteristics of the system are evaluated and discussed.     

在线检测技术在飞机结构件检测中的应用

本文根据飞机结构件在线检测的工程实际应用特点,提出了基于触发式测头的在线检测系统构建方案,针对在线检测中存在的主要问题,对测量后置处理程序的设计、测头标定方法、测头误差补偿方法等关键技术进行了研究,并在五轴机床上实现了飞机结构件的在线检测,验证了方案的可行性。     

A configuration independent error model of machine tools: Hyperpatch model and metrology pallet

A machine tool error model based on a three-dimensional hyperpatch error map was developed to describe the machine tool error field over a workspace. The error map was generated by a set of measurement points without using a detailed relationship among joints and linkages of a machine tool. The modeling is based on the motion that an ideal workspace is distorted to an actual workspace through a prescribed parametric representation. The concept was implemented on a three-axis CNC machining center. A metrology pallet was designed to serve as a reference coordinate frame of the workspace. A touch trigger probe was used to collect the required data. Experimental results show that this error model is capable of modelling the warm machine tool distortion behavior. The proposed model is based on the observed phenomena rather than the structural configuration of machine tools. Therefore, the advantage of this approach is that only a few measurements are required to construct the prediction model for a variety of machine tool configurations and for working environments.     

电容式力感知牙周探针设计建模与实验研究

针对当前牙周探针在探诊力控制方面的不足,提出一种基于悬臂梁挠曲效应的差动电容式力感知牙周探针解决方案,设计了探针验证结构,建立了探诊力作用下具有不规则形状的探针工作尖的挠曲模型,导出了探诊力和差动电容之间的求解方程,并通过仿真和实验对模型与方程进行了验证。结果表明,所建立的探针工作尖挠曲模型与静应力仿真结果的最大相对误差不超过±4.5%,所设计的力感知牙周探针多次重复探诊力检测实验的标准差小于均值的0.1%,所导出的求解方程的计算值与实验数据之间趋向一致,以探诊力为拟合权重进行修正后全量程的平均偏差为2.49%,具备进一步产品开发的可行性。     

Adaptive diagnosis in distributed systems

Real-time problem diagnosis in large distributed computer systems and networks is a challenging task that requires fast and accurate inferences from potentially huge data volumes. In this paper, we propose a cost-efficient, adaptive diagnostic technique called active probing . Probes are end-to-end test transactions that collect information about the performance of a distributed system. Active probing uses probabilistic reasoning techniques combined with information-theoretic approach, and allows a fast online inference about the current system state via active selection of only a small number of most-informative tests. We demonstrate empirically that the active probing scheme greatly reduces both the number of probes (from 60% to 75% in most of our real-life applications), and the time needed for localizing the problem when compared with nonadaptive (preplanned) probing schemes. We also provide some theoretical results on the complexity of probe selection, and the effect of "noisy" probes on the accuracy of diagnosis. Finally, we discuss how to model the system's dynamics using dynamic Bayesian networks (DBNs), and an efficient approximate approach called sequential multifault; empirical results demonstrate clear advantage of such approaches over "static" techniques that do not handle system's changes.     

Depth perception using blurring and its application in VLSI wafer probing

In this paper, we present a technique for measuring the amount of blur of an edge and using this information to determine the distance of a micromanipulator probe from a wafer surface in very large scale integration (VLSI) wafer probing. In this application, a soft and reliable touch of the probe with a metal pad in the wafer is a sensitive operation. The wafer is focused and several images of the probe while approaching the wafer are analyzed. In our theory, the amount of blur is calculated from the height of the step edge and the slope of the intensity profile at the zero crossing. Hence, our formula is simple and easy to use. We estimate the distance of the probe from the surface of the wafer and obtain a robust measure, i.e., one which is valid even in the presence of significant noise in the images. In order to validate our methods, we have experimented with various VLSI patterns as backgrounds.     

一种改进的WSN异常检测和定位算法研究

异常快速检测和定位对于保证无线传感器网络的有效运行具有重要作用.提出了一种改进的传感器网络异常检测和定位方法.该方法通过两个阶段的探查来收集端到端测量数据以实现异常检测和定位.第1阶段探查的目的是选择可以覆盖最大数量异常链路的探点,缩小可疑区域范围,供第2阶段探查,这一阶段的探点选择问题被建模为预算有限条件下的覆盖范围最大化问题,提出一种基于对偶线性规划的高效近似方法来求解此问题.第2阶段的目的是以最小的通信代价,定位出导致观察到的端到端异常现象的具体链路,并根据多环置信度传播算法(LBP)采预测诊断质量.在不同网络设置下展开实验,结果表明,相比于精确求解方法,提出的算法性能略有下降但运行速度更快.     

A pair of parallel differential magnetic‐field probes with high measurement accuracy and high electric‐field suppression ratio

Magnetic‐field probes can be used for electromagnetic interference measurement of high‐speed circuits. The main magnetic probe performance includes sensitivity, spatial resolution, electric‐field suppression ratio (EFSR), and measurement accuracy. In this article, a pair of differential magnetic‐field probes is proposed to improve measurement accuracy without reducing sensitivity. The proposed differential probes consist of two asymmetric loop probes, which are designed in the same plane and separated by a row of periodic vias. The proposed differential probes are fabricated under PCB process. High accuracy can be achieved by measuring difference between outputs of the two probes. In addition, EFSR can be improved by size optimization of the differential magnetic‐field probes. Simulation and measurement results show the operating bandwidth is from 100 MHz to 12 GHz, the measurement error is 3.4% and the EFSR is about 40 dB. The proposed probes have higher measurement accuracy and higher EFSR than the conventional single probe, and larger operation bandwidth than the stacked differential probes.     

Active probing based Internet service fault management in uncertain and noisy environment

In Internet service fault management based on active probing, uncertainty and noises will affect service fault management. In order to reduce the impact, challenges of Internet service fault management are analyzed in this paper. Bipartite Bayesian network is chosen to model the dependency relationship between faults and probes, binary symmetric channel is chosen to model noises, and a service fault management approach using active probing is proposed for such an environment. This approach is composed of two phases： fault detection and fault diagnosis. In first phase, we propose a greedy approximation probe selection algorithm （GAPSA）, which selects a minimal set of probes while remaining a high probability of fault detection. In second phase, we propose a fault diagnosis probe selection algorithm （FDPSA）, which selects probes to obtain more system information based on the symptoms observed in previous phase. To deal with dynamic fault set caused by fault recovery mechanism, we propose a hypothesis inference algorithm based on fault persistent time statistic （FPTS）. Simulation results prove the validity and efficiency of our approach.     

A multiple test arbors-based calibration method for a hybrid machine tool

Kinematic calibration is a necessary way to guarantee the accuracy of hybrid machine tools. The traditional calibration methods have high requirements for the measuring instruments and the measurement environment, and the measurement is extremely complex. The contradiction between measurement complexity and identification accuracy is an important problem in calibration. In this paper, a multiple test arbors-based calibration method for a hybrid machine tool is presented. The tool center point (TCP) position errors of multiple test arbors are measured sequentially by virtual TCP position constraints. The error parameters can be accurately identified based on these position errors without orientation measurement. The corresponding measurement scheme is described in detail according to whether the ball diameters of the test arbors are the same. The influence of the length and number of test arbors on the calibration results is investigated, and the basic principle for the selection of test arbors is given. Finally, the proposed method is validated by simulations and experiments. The proposed method can achieve overall high-accuracy calibration with simple measurement devices and convenient measurement steps, which provides a basis for automated calibration.     

基于多源信息融合的气象无人机平台可靠性评估研究

针对气象无人机平台可靠性评估中现场试验数据样本小的特点,提出了将气象无人机平台各个分系统的试验数据折合为系统试验数据,然后融合可靠性历史数据以及可靠性仿真数据,对气象无人机平台的可靠性进行评估的方法.结果表明,该方法具有可行性,能够达到在不降低置信度的前提下减少定型试验次数、节省经费的目的.     

车站列控中心测试平台——通信仿真子系统研究

车站列控中心测试平台是对列控中心系统进行可靠性、安全性测试及评估的平台。通信仿真子系统是平台的一个子系统,它主要实现被测对象与平台中相关模拟子系统之间数据的交互。采用面向对象的多线程串口通信技术对通信仿真子系统进行了研究。详细地阐述了测试平台与被测对象之间的接口方式与通信协议,并给出仿真实例,满足了平台对通信仿真子系统的要求。     

Isoparametric line sampling for the inspection planning of sculptured surfaces

This paper presents a new approach for the sampling of sculptured surfaces using continuous scanning coordinate measuring machine probe heads. This approach is based on scanning isoparametric lines on the sculptured surface. This paper addresses the issue of isoparametric line sampling. The problem is to determine the locations of the sample lines extracted from the surface CAD model. These lines are fitted to construct a substitute geometry of the surface. The accuracy of the sampling plan is characterised by the maximum deviation between the substitute geometry and the surface CAD model. Two new algorithms for sampling isoparametric lines are proposed. These are, automatic sampling, and surface curvature-based sampling. Both algorithms are constrained by the maximum number of scan lines, and the step over distance between subsequent sample lines. Automatic sampling uses the deviations between the substitute geometry, and the surface CAD model to determine the sample locations. Curvature change-based sampling uses the change in surface curvature to determine the sampling line locations. Both algorithms are compared to uniform iso-planar sampling. The algorithms, their implementation, and a case study are presented in this paper.     

基于电容式传感测头的电容检测系统的设计

针对纳米尺寸测量领域的不同测量要求,尝试开发一种基于电容传感器的微触觉测头及其电容检测系统。阐述了测头的结构原理和电容传感器的工作原理,研制了基于电容传感器的微触觉测头。测头的测量原理表明:微小电容检测电路是整个电容检测系统的关键部分。该微小电容检测电路选用电容/数字转换器(CDC)AD7747芯片,分别编写了单片机与该芯片的I2C通信程序和单片机与上位机间的串行通信程序,实现了微小电容的采集和处理,简单进行了电容式传感测头的轴向性能的测试实验。实验表明:电容式微触觉测头的分辨率为0.02μm,重复性较好,证实了此电容式微触觉测头的可行性。     

四路摄像头协同多重触控系统标定方法

四路摄像头协同多重触控系统通过拟合四路摄像头得到触点方向线,以解决多触点遮档问题。针对该原理中触点方向线构建问题,提出查找表法、消失点法和立体标定法3种系统标定方法,以实现多触点精确定位。查找表法在交互区边框上设定标定点,通过插值查找对应标定点,以光心和标定点构建触点方向线;消失点法利用触点方向上的消失点和光心构建触点方向线;立体标定法利用极线几何反投影射线构建触点方向线。误差分析实验结果表明,查找表法适用于较小尺寸平台,消失点法适用于大尺寸平台,立体标定方法精度有待提高。     

三坐标测量机一般表面上的自适应采样规划

针对CAD模型已知的三坐标测量机一般表面(连续或非连续的基本特征表面)上的常用采样策略中存在的问题,提出一种自适应采样方法,并对测量边和面的情况分别给出了具体的采样算法.通过对选取的表面进行分析,采取步长自适应再分迭代自动规划出相应数目的采样点分布;并使采样点达到均匀分布且避开非连续区域.实验结果表明,该方法对于各种复杂情况的一般表面都有比较好的适应性,弥补了随机采样难以均匀化和基于数字序列采样对表面要求完整连续的不足.