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。     

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。     

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。     

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.     

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。     

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.     

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。     

一种五自由度铣削机器人的运动分析和仿真

在加工形状复杂、切削力小、尺寸大的非金属工件时,可以采用工作空间大的串联机器人代替专用的数控加工系统进行铣削加工.针对特定工件的加工设计五自由度铣削机器人,用D-H方法对该机器人进行了正、逆运动学分析,根据工件加工特点对机器人末端操作器位置进行轨迹规划,最后利用MATLAB软件的Robotics Toolbox工具进行了仿真.     

Quantitative evaluation method for machining accuracy retention of CNC machine tools considering degenerate trajectory fluctuation

Accuracy retention is an important performance index of CNC machine tools. At present, research on the evaluation of machining accuracy retention of CNC machine tools mainly focuses on accuracy value of a fixed time point or different time periods, but studies on the fluctuation degree of degradation trajectory related to time change are limited. Extracting simple and effective degradation characteristics of machining accuracy and then evaluating machining accuracy retention considering fluctuation of degradation trajectory are necessary. The volume error model of CNC machine tools is established on the basis of multibody system theory in this study. Three-dimensional volume error vector is transformed into one-dimensional machining accuracy degradation by calculating offset distance between spatial error and origin points. Degradation data obtained via regular measurement and calculation are used to establish the complete degradation trajectory model of the CNC machine tools machining accuracy using radial basis function interpolation method according to the fluctuation degree of degradation trajectory, and concepts of average degradation rate and average degradation amount are defined. Lastly, examples showed that these two indicators can intuitively reflect fluctuation degree of machining accuracy degradation of CNC machine tools and effectively and quantitatively evaluate accuracy retention of CNC machine tools. The quantitative evaluation method of accuracy retention of CNC machine tools defined in this study considers the fluctuation degree of accuracy degradation trajectory. The quantitative evaluation index of accuracy retention demonstrates satisfactory engineering application because it can reflect not only the accuracy change of a single machine tool but also accurately compare the accuracy retention between different machine tools.

     

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.     

铣削串联机器人运动分析与轨迹规划

在加工形状复杂、切削力小、尺寸大的非金属工件时,可以采用工作空间大的串联机器人代替专门的数控加工系统进行铣削加工。本文针对特定工件的加工设计了一个6自由度铣削串联机器人,用D—H方法对该机器人进行了正、逆运动学分析,根据工件加工特点对机器人末端操作器位置进行了轨迹规划,最后利用MATLAB软件的Robotics toolbox工具进行了建模和仿真。本文为在铣削加工方面应用的工业机器人进一步的动力学分析,提供了理论基础。     

焊接机器人运动学分析及轨迹规划研究

针对梁构、石化容器等大型焊件普遍存在的焊接难的问题,研制了一种新型7自由度大型焊接机器人.首先,分析了该机器人的机械结构,基于D-H坐标系理论建立了机器人的运动学方程,并对该方程进行了求解,得到了其运动学正反解;其次,在关节空间内,采用过路径点的三次多项式插值方法,结合机器人操作空间运动参数对关节轨迹插值计算,实现了对机器人关节空间的轨迹规划;最后,在Matlab7.8平台上,利用机器人工具箱建立了该机器人模型,并且对机器人运动学、轨迹规划进行了仿真分析.仿真及研究结果表明:该机器人各连杆参数的设计是合理的,在关节空间内利用三次多项式进行轨迹规划具有可行性;同时,这也为机器人动力学的研究打下了基础.目前该技术已应用于机器人的点焊及角焊的现场作业中.     

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。