Selection of test nodes for analog fault diagnosis in dictionaryapproach

In this paper, the selection of test nodes has been studied extensively and efficient techniques are proposed. Two broad categories of methods called inclusion methods and exclusion methods are suggested. Strategies are presented to select or delete a test node without affecting the diagnosis capabilities. Examples show that these strategies give a lesser number of test nodes some times. Starting from the fault-wise integer coded table of the test circuit, sorting is employed to generate valid sets and minimal sets. The order of computation of these methods is shown to depend linearly on number of test nodes. It is also proportional to (f log f) where “f” is the number of faults. This is much faster than well-known methods. The concept of minimal set of test nodes is new in analog circuit fault diagnosis. Polynomial time algorithms are proposed in this paper for the first time to generate such sets     

A new analog voltage sorter

An analog circuit for comparing and sorting two input voltages is described. Using the circuit as a basic unit, a four-input sorter is designed. A technique to determine which of the four inputs corresponds to (address of the input of) a given output is also presented. The procedure can be extended to design an n-input sorter     

Automated selection of test frequencies for fault diagnosis in analog electronic circuits

This paper suggests three novel methods for selecting the frequencies of sinusoidal test signals to be used in fault diagnosis of analog electronic circuits. The first and second methods are based on a sensitivity analysis and show to be particularly effective in linear circuits where a priori information and designer experience can be exploited. Conversely, the third method selects the input frequencies to be used for diagnostic purposes without requiring any hypothesis about the circuit or testing design background. As such, the method is particularly appealing in complex -possibly nonlinear - circuits where the designer experience is of little value and an effective "blind" approach saves both designer and testing time. The suggested frequency selection methods are then contrasted to each other against performance and computational complexity.     

A new adaptive control of dual-motor driving servo system with backlash nonlinearity

In order to weaken the influence of backlash nonlinearity on a dual-motor driving servo system, we first establish the state-space model of the system. We then propose a new adaptive controller combining a projection algorithm with backstepping control for the first time, to the best of our knowledge, and analyze its stability. In the simulation analysis, we respectively choose a triangular wave, sawtooth wave, and random signal as the input signal. Simulation results validate a higher tracking accuracy and stronger adaptability of the proposed control law than that of mere backstepping control. In the experimental tests, we respectively choose a step signal and sine signal and simultaneously apply a white noise signal to the system output after 3 s in each test. The test results validate a stronger adaptability and robustness than that of mere backstepping control.     

A programmable real-time system for development and test of new ultrasound investigation methods

In vitro and/or in vivo experimental tests represent a crucial phase in the development of new ultrasound (US) investigation methods for biomedical applications. Such tests frequently are made difficult by the lack of flexibility of general purpose instruments and commercial US machines typically available in research laboratories. This paper presents a novel, real-time development system specifically designed for US research purposes. Main features of the system are the limited dimensions (it is based on a single electronic board), the capability of transmitting arbitrary waveforms to two probes, of storing the received radio-frequency (RF) echo data in a file and/or of processing them in real-time according to programmable algorithms. As an example of application, results of simultaneous hemodynamic and mechanic investigations in human arteries are reported. However, the high system flexibility and portability make it suitable for a large class of US applications.     

A brain-based system for adaptive automation

Adaptive automation refers to technology that can change its mode of operation dynamically. Further, both the technology and the operator can initiate changes in the level or mode of automation. One of the important issues surrounding this technology concerns the method for initiating changes in the state of automation. The present paper considers the potential of using brain activity to drive an adaptive automation system. Relevant research on EEG is presented followed by a review of several experiments in which EEG is used to trigger changes among system modes in an adaptive automation system. The system moderates operator task load based upon an index derived from a ratio of EEG power bands. The research shows that it may be feasible to build an adaptive automation system and use this index of brain activity to drive the system. The paper concludes with a discussion of several issues that still need to be addressed before this approach can move beyond the laboratory.     

A flowmeter test system

Translated from Izmeritel'naya Tekhnika, No. 1, pp. 20–21, January, 1988.     

基于自适应谐波小波和能量熵的转子系统故障诊断研究

针对转子系统非平稳振动时故障特征难以准确提取的问题,提出一种基于自适应谐波小波和能量熵的转子系统故障诊断方法。首先,采用连续谐波小波方法分解转子信号,克服二进制谐波小波包分解不能任意选取感兴趣频段的缺限,同时在分解过程中通过时间尺度变换的方式消除信号采集过程中不同转速及采样频率的影响;然后,通过设定合理的分解参数,提取出表征转子系统的故障特征信息并构建故障模式矩阵,得到转子系统早期局部碰摩、全周碰摩、油膜涡动和油膜振荡等4种工况下的能量熵值;最后,将特征向量输入支持向量机(support vector machine,SVM)判断出转子系统的故障类型。试验结果表明:该方法可以有效用于转子系统的故障诊断。     

网络化机载测试系统故障实时诊断技术

为便于维护网络化机载测试系统,及时定位测试系统故障,分析网络化机载测试系统架构及4种关键运行状态,设计一种基于关键运行状态实时监控的测试系统故障诊断方案,通过提取测试系统关键运行状态,利用遥测数据链路,实现测试系统关键状态实时监控及实时故障诊断。在某型飞机中进行方案验证,结果表明,该方案实现测试系统关键运行状态实时监控,能快速定位出测试系统故障。     

A new high resolution color flow system using an eigendecomposition-based adaptive filter for clutter rejection

We present a new signal processing strategy for high frequency color flow mapping in moving tissue environments. A new application of an eigendecomposition-based clutter rejection filter is presented with modifications to deal with high blood-to-clutter ratios (BCR). Additionally, a new method for correcting blood velocity estimates with an estimated tissue motion profile is detailed. The performance of the clutter filter and velocity estimation strategies is quantified using a new swept-scan signal model. In vivo color flow images are presented to illustrate the potential of the system for mapping blood flow in the microcirculation with external tissue motion.     

A new high resolution color flow system using an eigendecomposition-based adaptive filter for clutter rejection

We present a new signal processing strategy for high frequency color flow mapping in moving tissue environments. A new application of an eigendecomposition-based clutter rejection filter is presented with modifications to deal with high blood-to-clutter ratios (BCR). Additionally, a new method for correcting blood velocity estimates with an estimated tissue motion profile is detailed. The performance of the clutter filter and velocity estimation strategies is quantified using a new swept-scan signal model. In vivo color flow images are presented to illustrate the potential of the system for mapping blood flow in the microcirculation with external tissue motion.     

分形特征的模拟电路故障诊断方法

针对模拟电路中存在的非线性问题,提出一种以模拟电路分形特征为输入量的故障诊断方法。通过对多测试分量数据进行分形特征提取,输入神经网络建立信息融合中心融合处理各分形特征量,利用多源性互补信息减少模拟电路故障诊断的不确定性。实验结果表明,该故障诊断方法可准确地检测出模拟电路中的故障现象。     

基于系统搜索的容差模拟电路多参数故障诊断

针对容差条件下非线性模拟电路的多参数故障诊断问题,提出一种系统搜索算法求解故障参数,实现故障元件的定位和参数辨识。首先将非线性测试方程的多解求解转化为差分方程的初值问题;然后采用牛顿法迭代生成简单曲线簇,沿曲面方向进行测试方程的解搜索,并通过四阶龙格库塔法计算初值问题的数值解,显著提高方程组解的求解效率,降低漏解的风险;最后将故障集验证转化为容差约束下的线性规划问题求解,实现故障元件定位,并通过实际电路实验验证该算法的有效性。该算法适用于含BJT和CMOS等非线性电路的故障诊断,具有较高的诊断准确度和参数辨识准确度。     

一种用于跨域轴承故障诊断的深度自适应网络EI北大核心CSCD

针对轴承在不同工况条件下的振动数据存在分布差异,导致诊断精度低的问题,提出一种新的深度自适应网络用于跨域条件下的轴承故障诊断。采用傅里叶变换将原始时域振动信号转换为频域信号并通过深度特征提取器提取其分类特征;利用最大均值差异(maximize mean discrepancy,MMD)来进行深度特征的边缘分布对齐;利用Wasserstein度量网络将源域中有标签数据的类别结构与目标域中无标签数据的类别结构进行匹配,即对齐不同域的类别条件分布,使得故障数据在不同域的分布能够更好的对齐,从而提高模型在目标域未标签数据集上的分类准确率。试验利用凯斯西储大学公开的故障轴承数据集进行了两种跨域条件的模型迁移,验证了该网络在不同迁移场景中都具有较高的准确率,且优于其他深度自适应网络。     

一种新的自适应扩频数字音频水印

水印技术已经在多媒体版权保护中得到广泛的应用。针对扩频相关性检测模型在实际应用中的问题--短时均值和方差不满足假设,导致检测正确率降低,通过在MCLT变换域嵌入扩频水印,提出了一种新的嵌入强度自适应和检测期望自适应的水印算法。以期获得更高的检测正确率和较好的稳健性,隐蔽性。实验结果表明文中所提出的方法能在人耳不易察觉的情况下消除这种相关检测干扰,并有效抵抗攻击,有很高的检测正确率,对扩频音频水印有一定的参考价值。     

A new finite-volume approach with adaptive upwind convection

A new finite-volume approach is developed and applied to the two-dimensional continuity and convective-diffusive energy equations. The variation of the field variables is approximated by bi-quadratic interpolation formulae over the space occupied by the finite volume and the region surrounding it. These are used in the integral conservation laws for energy and mass. The convective transport is modelled using a new upstream-weighting approach which uses volume averages for the energy transported across the boundaries of the finite volume. The weighting is dependent on the skewness of the velocity field to the surfaces of the finite volume as well as its strength. It is adaptive to local flow conditions. Two test cases are treated which have exact solutions. The first is not new and involves a rotating shaft. The errors are less than 0.06 per cent for this case. The second case is new and involves convection past a source and sink. In contrast to the first case, the global Peclet number is a strong parameter, and cell Peclet numbers (Pe_h) range from 0 to 20. The maximum error is 2.3 per cent for Pe_h = 4, and there is no evidence of numerical diffusion for even the largest value of Pe_h. For both test cases, the maximum error occurs at moderate values of Pe_h and diminishes at the extreme low and high values.     

A new shape-vector quantization-based adaptive predictive image coder

In this paper, a new lossless image compression technique, shape-vector quantization (VQ)-based adaptive predictive coder (SAPC), is introduced. In the proposed scheme, the local shape information of the image block is obtained through shape-VQ. This information is utilized by a novel predictive coder, shape-differential pulse code modulation (DPCM), to adaptively select the optimum predictor on a pixel-by-pixel basis. The prediction errors can be further compressed by an error-adjusting process. The proposed scheme achieves a breakthrough in prediction by utilizing the local feature of the image block through shape-VQ, thus improving the accuracy of the prediction while reducing the overhead of the side information. It also simplifies the complicated procedures involved in the computation of the prediction parameters. Although the proposed scheme outperforms many traditional lossless image-coding schemes, it produces comparable results to the newly developed context-based scheme with lower computational complexity. On the basis of the promising compression results, the proposed scheme could be the best candidate for the lossless image coding. © 2000 John Wiley & Sons, Inc. Int J Imaging Syst Technol, 10, 419–426, 1999