Real-time monitoring of complex sensor data using wavelet-based multiresolution analysis

Advancements made in sensor technology have resulted in complex sensor data that captures multiple process events. Real-time monitoring of complex manufacturing processes, such as nano-scale semiconductor polishing, often requires analysis of such complex sensor data. The multiple events in a process occur at multiple scales or frequencies (also referred to as multiscale) and are localized at different points in time. Recent literature contains several wavelet decomposition based multiscale sensor data analysis techniques including those that are developed for process monitoring applications, such as tool-life monitoring, bearing defect monitoring, and monitoring of ultra-precision processes. However, most of the above mentioned wavelet-based sensor data analysis techniques are designed for offline implementation. In an offline method, one can perform wavelet decomposition of longer data lengths in order to capture information needed for monitoring. However, this is computationally involved and needs longer processing time, which becomes a serious challenge in online (real time) applications. This paper first presents a complete online multiscale process monitoring methodology. The methodology is designed to deal with real-time analysis and testing of very high rate of process data collected by sensors. This is particularly critical and becomes a challenge for high rate of data collection by the sensors which pose additional difficulty of matching data processing rate with the data acquisition rate. The methodology is capable of displaying the analysis results through real time graphs for ease of process supervisory decision making. The methodology is demonstrated via a nano-scale silicon wafer polishing application. Sufficient details of the application are provided to assist readers in implementing this methodology for other processes. The results show that the methodology has the ability to deal with high rate of data collection as well as multiscale event detection.     

数控机床高精度轨迹控制方法探讨

针对数控技术和装备向高速高精度发展的需求,研究开发了一种新的高精度轨迹控制技术。其核心内容是以高频高分辨率采样插补生成刀具运动轨迹,通过新型转角—线位移双位置闭环控制保证希望轨迹的准确实现,并以信息化轨迹校正消除机械误差和干扰对轨迹精度的影响,从而保证所控制的机床可在生产环境中长期高精度运行。由此构成的新型数控系统已在多种国产数控机床上进行了应用,取得了良好效果。     

高精度星敏感器标定方法研究

星敏感器是一种广泛应用在航天飞行器中的高精度姿态测量器件,精度标定是保证高精度测量的重要环节。为了尽量提高星敏感器的整体精度,对传统星敏感器标定方法进行了仿真分析,针对传统星敏感器标定方法模型参数难以解耦的弊端,提出单独标定主点,将星敏感器光学参数误差(如焦距、成像平面倾斜和畸变)等看作一个整体误差源,采用直接映射的方式进行标定。该方法简单方便、标定精度高,避免了传统方法中误差影响因素分析不全面及多次求取拟合近似值造成的累积误差。实验结果表明,该标定方法完全满足测量角误差2″的要求。     

Increasing the accuracy of ECG based biometric analysis by data modelling

Here an effort is made to use human electrocardiogram as a tool of biometric analysis for authentication. The proposed method is based on first accurate extraction of characteristic features from each ECG and then design of a suitable classification methodology to comment on the authenticity. As the feature matrix is a huge one, Principal Component Analysis (PCA) is applied to avoid handling of large amount of data. Next, the reduced features from PCA are fitted into a quadratic polynomial model by the method of least square. Then the fitted values for the allowed set of data is obtained and the range over which they vary, provides the signature matrix of a person. Finally the classification is done by a comparison based on nearest neighbor method. The method is tested on ECG of 20 individuals taken from PTB database. This method has accuracy more than 95% with the best fit modeling which becomes only 80% without data modeling proving the importance of best fit modeling of data before classification. This accuracy is comparable with conventional biometric techniques; moreover, ECG biometric can be used with other authentication scheme, with ECG providing liveliness proof.     

Reference trajectory analysis and trajectory control by bank angle for re-entry vehicle

The re-entry problem consists of guidance design and trajectory control. This paper summarizes the detailed relationships between the velocity, drag acceleration and altitude in determining reference trajectories. The computational issues are also addressed, and the performance of the proposed simple nonlinear control of a bank angle for the longitudinal/lateral trajectory is demonstrated. In particular, the fixed bank angle methods that can reduce the drag acceleration errors at low-speeds are proposed. The importance of bank reversals with respect to the azimuth errors is also elucidated.     

基于VRML的模具边界提取方法与加工轨迹优化研究

为解决气压砂轮进动抛光在模具边界区域的振动加剧、边界棱线过度磨损和气压砂轮失效等问题,将VRML技术应用到气压砂轮进动抛光轨迹规划中。经过对VRML文本内容的分析,采用一系列三角形平面取代原始的多边形平面和自由曲面的VRML描述模型表面的方法,建立了文本数据与模型边界线之间的对应关系,提出了一种基于VRML的模具边界线三维解析式提取方法,并将该方法应用到气压砂轮进动抛光轨迹优化中;通过限制气压砂轮切削速度方向与模具边界外法向量的夹角,获得了理想的切削速度分布特性。实验及研究结果表明:通过该优化方法获得的模具边界线数据具有较好的完整性和准确性,适用于各种复杂形貌的模具零件的轨迹优化,并可通过调整阈值来满足具有不同曲率曲面的识别要求。     

电路噪声对星敏感器星点定位精度的影响

提出了一种测量星敏感器电路模块带来的图像噪声的方法。在实验室条件下,用星敏感器拍摄多幅背景图像,分析表明:不同背景图像上相同像素的灰度差值代表了电路模块带来的图像噪声,该噪声服从正态分布。模拟产生该正态分布的随机矩阵作为图像噪声加到理想的星点上,采用亚像素细分质心算法计算出带噪声的星点质心坐标,从而得到噪声带来的星点位置偏差。计算结果表明:实验室条件下,星敏感器实测6等星的质心测量精度为1/25 Pixel,而电路噪声将引起1/200 Pixel量级的标准偏差;电路噪声,尤其是DC/DC电源纹波噪声对星敏感器星点定位带来的误差是不容忽视的。     

Pneumatic intracranial pressure transducer: Design and accuracy analysis

A new intracranial pressure transducer, based on the miniature pneumatic nozzle-flapper amplifier with negative feedback, is described. The problem of steady-state accuracy of intracranial pressure measurement in relation to the stiffness of the transducer membrane and dura mater is also discussed. The transducer has successfully undergone clinical testing on 61 patients and proved to be practical and convenient. Its manufacture is under way.     

平面磁力研磨轨迹的研究与分析

利用自行设计的试验装置,改善了磁力刷的研磨轨迹。结果表明:改善磁力刷研磨轨迹后,不仅可以减小表面粗糙度值、提高平面精度,还改善了研磨截面微观形状均匀性。另外,可通过采取理论分析的方法对研磨效果进行预测。     

电能表数据传感器的设计

电能表数据传感器是一种通过机电变换方式将电磁式电能表的待记录数据转换为电脉冲信号的传感装置,主要功用是进行数据远程传输和电子显示,主要介绍电能表数据传感器的组成和工作原理,重点介绍电能表数据传感器的结构和运作过程。     

船载高精度星敏感器安装角的标定

星敏感器测量船体姿态精度与星敏感器与甲板之间的安装角标定精度密切相关。本文介绍了船载星敏感器的相关坐标系及安装角的定义,建立了船载星敏感器蒙气差修正模型,提出了一种船载高精度星敏感器安装角标定方法。船进坞坐墩时,船载经纬仪通过拍摄方位标确定航向,星敏感器通过星图识别获得视场内星点的赤经、赤纬,构成地心惯性系参考矢量,经岁差、章动、极移、船位等修正,得到各恒星在惯导地平系下的参考矢量。然后,根据蒙气差模型对星点逐个修正俯仰角,重构惯导地平系下的参考矢量。最后,依据姿态确定算法原理,解算星敏感器安装矩阵,求解安装角。实验表明,使用该方法可使方位角、俯仰角的标定精度达10"以内。该方法有效发挥了星敏感器指向精度高的优点,改善了程序自动化程度,提高了船体姿态测量精度。     

时间配准在多传感器数据处理中的应用

在应用多传感器进行数据采集的系统中,需要对源于同一目标、同一时刻的不同传感器数据进行融合处理,但由于各传感器的工作方式、传输时延等原因造成数据不同步的问题。因此,在对多传感器数据融合前,应该对多传感器数据进行时间配准。本文提出了采用内插、外推时间配准法解决多传感器时间配准问题,通过仿真验证,该算法可以较好的解决问题。     

面向大规模感知数据的实时数据流处理方法及关键技术

为了在大规模历史感知数据基础上实现针对高速传感数据流的实时计算,提出一种面向大规模历史数据的数据流处理方法RTMR,通过中间结果缓存、流水化和本地化改进了MapReduce的数据流处理能力.在此基础上,为了适应性地构造RTMR集群,利用模型分析方法根据应用特征和集群环境配置节点类型和拓扑结构.为实现集群的负载均衡,通过计算负载状态转换关系分组空闲节点和过载节点,将NP难的动态负载均衡问题快速分解为规模较小的子问题,并且综合执行时间和数据移动代价作为子问题的优化目标,提高应对负载倾斜的反应速度.实验表明,上述方法和技术能够保障大规模历史数据上数据流处理的可伸缩性.     

Damage detection using self-powered wireless sensor data: An evolutionary approach

A major limitation in implementation of self-powered wireless sensors pertains to considerable loss of the sensed information. Consequently, interpretation of the limited but valued data generated by the self-powered wireless sensing technology becomes a challenging problem. To tackle this issue, this study presents an evolutionary computational approach for structural damage detection using the self-powered wireless sensor data. The proposed data interpretation system is based on the integration of a robust evolutionary technique, called gene expression programming (GEP), and finite element (FE) method. Several damage indicator variables are extracted upon the simulation of the compressed data stored in memory chips of self-powered sensors. For the analysis, the complicated case of gusset plate of bridge is considered. Different damage scenarios are introduced to the plate and for each scenario and sensor configuration, a damage detection model is derived. Bases on a logistic regression analysis, probabilities are assigned to each model to find the most probable damage state. The damage detection models are presented as MATLAB and Visual Basic codes for further analysis. An uncertainty analysis is performed through the contamination of the damage indicator features with different noise levels. The results indicate that the proposed method is efficiently capable of detecting different damage states in spite of high-level noise contamination.     

Effectiveness of rotatable sensor to improve image accuracy of ECT system

This paper presents a new design of rotatable sensor for ECT systems that can be mounted on a multi-phase flow installation. In order to attest how the performance of the sensor is affected by the rotatable frame, the effectiveness of the rotatable sensor is analyzed in terms of SNR (Signal-to-Noise Ratio) and image accuracy, which is dependent on the number of independent measurements, the image reconstruction strategy and the size of the mesh. The results confirm that with a sensor equipped with 16 electrodes, the optimum number of rotation steps is 3 in order to get the best compromise in terms of image accuracy and image reconstruction time. Results also show that this configuration achieves results similar to a classical sensor equipped with 32 electrodes.     

Vortex flowmeter with enhanced accuracy and reliability by means of sensor fusion and self-validation

Due to the complementary qualities of the principles of vortex frequency estimation and vortex time of flight estimation they are ideally suited for an effective sensor fusion within flow measurement. A flow meter which combines the results of the two individual systems in an intelligent manner was built and beside theoretical considerations the performance of the fused system is demonstrated by a variety of measurements. In comparison with conventional vortex meters which only use the vortex frequency to estimate the flow rate, the measuring range can be extended by a factor of 8–10 and the accuracy of the system as well as the robustness to disturbances like a second fluid phase or depositions on the bluff body are strongly increased.     

压力传感器数据采集系统的设计

设计了一种实时压力数据采集系统,数据采集卡主要由采集传感器数据的ADuC824单片机和实现UART转USB的CP2101桥接芯片组成,再通过USB接口与上位机实现数据通信。基于VB6.0软件编写了上位机的应用程序,实现了对采集数据的实时显示和曲线显示。系统具有结构紧凑、便于携带和稳定的特点。     

提高自动站观测数据准确性的探讨

本文从两种不同观测方法的观测结果差异产生的原因和实际情况入手,对自动气象站的自动观测和台站人工观测这两种观测体制下的观测准确度进行探讨,进而提出确保自动观测数据准确、可靠并具有可比性的技术保障措施。