Simultaneous fault detection and control design for switched systems with two quantized signals

The problem of simultaneous fault detection and control design for switched systems with two quantized signals is presented in this paper. Dynamic quantizers are employed, respectively, before the output is passed to fault detector, and before the control input is transmitted to the switched system. Taking the quantized errors into account, the robust performance for this kind of system is given. Furthermore, sufficient conditions for the existence of fault detector/controller are presented in the framework of linear matrix inequalities, and fault detector/controller gains and the supremum of quantizer range are derived by a convex optimized method. Finally, two illustrative examples demonstrate the effectiveness of the proposed method.     

一类线性离散时间系统的鲁棒故障检测

研究一类受白噪声影响的线性离散系统的鲁棒故障检测滤波问题。设计基于观测器的残差产生器。利用主元子空间算法。对观测器的参数矩阵进行设计。算例验证了提出方法的有效性。     

Fault detection and diagnosis for singular stochastic systems via B-spline expansions

This paper deals with the problem of fault detection and diagnosis (FDD) for singular stochastic systems. The outputs of singular stochastic systems are described by probability density functions (PDFs) based on square root B-spline expansions. Then, two non-linear observers are designed for the FDD. The conditions of stability of the correlative error estimation systems are given by using linear matrix inequalities (LMIs). Finally, the simulation results are presented to indicate that the approach can detect faults and estimate the size of faults.     

Leak detection systems in oil and gas fields: Present trends and future prospects

Early leak detection of liquid and gas of both buried and unburied pipelines remain a critical task for economical and safety reasons. Several techniques were recently suggested and tested in real-life conditions and the corresponding results are very encouraging since they offer low cost solution while they yield both true detection and accurate localization of the leak. However, most of the techniques are not robust enough for all possible scenarios and may fail under certain environmental conditions. This review paper presents the most recent findings in acoustic and infrared (IR)-based leak detection techniques which remain the most widely used techniques for liquid and gas leaks detections respectively. However, they may fail under some situations. For instance IR-based techniques are not adequate during rainy, humid, or sandy weather or when ppb sensitivity is required, while acoustic sensors are not adequate for gas leak detection or when additional sources of acoustic noise are in the vicinity of the target area. Thus, the paper provides other alternative techniques such as ground penetrating radar (GPR), temperature profiling, and photoacoustic sensing techniques. Several important research works and real-life applications are cited in an attempt to provide a reasonable cross-section of various techniques. The paper can be useful for either a fresh researcher in the area, or for a skilled R&D engineer involved in the design of a leak detection solution since it presents the most recent leak detection techniques.     

DMC与VDL数控铣床整机静刚度比较

在对DMC与VDL数控铣床整机结构特点研究的基础上,利用有限元法对其进行静力分析,并就加强筋与板壁孔等结构对刚度的影响进行了比较,为数控铣床结构的合理设计提供了经验和依据。     

同科室两种生化检测系统对10项生化项目测定结果的比对和偏倚分析

目的:通过本科室两种生化检测系统(BDS)对10项常规生化项目的检验结果进行比对分析和偏倚评估,探讨不同BDS对同一检测项目的结果是否具有可比性和偏倚可接受性。方法:根据美国临床实验室标准协会EP9-A2文件标准要求,每天随机选取8例新鲜血清样本在贝克曼AU2700[为参比系统]和XC8001[为试验系统]全自动生化分析仪上测定10项(谷丙转氨酶、谷草转氨酶、白蛋白、总蛋白、肌酐、尿素、总胆固醇、甘油三酯、高密度脂蛋白胆固醇和低密度脂蛋白胆固醇)常规生化项目,每例样本按正反序重复检测两次,连续测量5天,记录各测定值。计算Y与X之间的相关系数,直线回归方程和不同医学决定水平处的相对偏差。并以美国临床实验室改进修正案能力验证规则(CLIA,88)分析质量要求中规定可接受范围的1/2作为标准,判断两BDS之间的可比性和偏倚临床可接受性。结果:未发现有离群点出现,10个常规生化检测项目的r值均≥0.975,满足EP9-A2文件规定r≥0.975(或R2≥0.95)的要求。所检测数据经单因素方差分析,差异无统计学意义(P>0.05)。10个常规生化检测项目不同Xc的相对偏差SE%,结果均<可接受范围的1/2。结论:本院两种BDS通过方法学比对,对同一检测项目测定结果具有一致性,且各检测项目在各医学决定水平处出现偏倚临床是接受可接受性。     

Design of H(infinity) robust fault detection filter for linear uncertain time-delay systems

In this paper, the robust fault detection filter design problem for linear time-delay systems with both unknown inputs and parameter uncertainties is studied. Using a multiobjective optimization technique, a new performance index is introduced, which takes into account the robustness of the fault detection filter against disturbances and sensitivity to faults simultaneously. The reference residual model is then designed based on this performance index to formulate the robust fault detection filter design problem as an H(infinity) model-matching problem. By applying robust H(infinity) optimization control technique, the existence condition of the robust fault detection filter for linear time-delay systems with both unknown inputs and parameter uncertainties is presented in terms of linear matrix inequality formulation, independently of time delay. In order to detect the fault, an adaptive threshold which depends on the inputs is finally determined. An illustrative design example is used to demonstrate the validity of the proposed approach.     

DMC与VDL数控铣床整机静刚度比较

在对DMC与VDL数控铣床整机结构特点研究的基础上，利用有限元法对其进行静力分析，并就加强筋与板壁孔等结构对刚度的影响进行了比较，为数控铣床结构的合理设计提供了经验和依据。     

基于FPGA和DSP的高精度多通道信号检测系统硬件设计

针对电磁检测、电能质量检测应用领域中,大量传感器或参数需要实时检测处理的问题,对检测过程中采样时刻的设定、检测通道的选择、采样速率的设定、检测精度、数据处理能力进行了分析研究,对采样方式、控制策略、系统运行效率等进行了总结。提出了一种以DSP为主机,FPGA为从机的双CPU硬件结构,并将其应用到了检测系统的硬件设计中。系统中通过FPGA完成了数据采集相关的通道选择,采样时刻、采样速率设定等工作;通过DSP完成了工作参数配置,检测数据处理,以及与上位机通讯等工作;通过工作分工建立了控制主机与检测通道、采样时刻、检测数据之间的联系,实现了数据的采集、存储、处理及显示。研究结果表明,该双CPU结构的检测系统具有检测通道选择、采样时刻控制灵活、检测精度高、数据处理方便的优点。     

Comparison of the efficacies of two different fiber post‐removal systems: A micro‐computed tomography study

The aim of this in vitro study was to compare the efficacies of two different fiber post‐removal systems. Thirty extracted single‐rooted mandibular premolar teeth were used. After RelyX fiber posts were cemented, the teeth were divided into two groups with regard to the post removal techniques: ultrasonic vibration and D.T. Light‐Post removal kit. Residual material, tooth volume changes, working time and micro‐crack formation were assessed using micro‐computed tomography. All data were analyzed using Wilcoxon signed‐rank and Mann–Whitney U tests. There was significantly more tooth root volume change in the ultrasonic group than removal kit group (p < .05). Fiber post removal time for the ultrasonic group was significantly longer than the removal kit group (p < .01).     

MRF‐ANN: a machine learning approach for automated ER scoring of breast cancer immunohistochemical images

Molecular pathology, especially immunohistochemistry, plays an important role in evaluating hormone receptor status along with diagnosis of breast cancer. Time‐consumption and inter‐/intraobserver variability are major hindrances for evaluating the receptor score. In view of this, the paper proposes an automated Allred Scoring methodology for estrogen receptor (ER). White balancing is used to normalize the colour image taking into consideration colour variation during staining in different labs. Markov random field model with expectation‐maximization optimization is employed to segment the ER cells. The proposed segmentation methodology is found to have F‐measure 0.95. Artificial neural network is subsequently used to obtain intensity‐based score for ER cells, from pixel colour intensity features. Simultaneously, proportion score – percentage of ER positive cells is computed via cell counting. The final ER score is computed by adding intensity and proportion scores – a standard Allred scoring system followed by pathologists. The classification accuracy for classification of cells by classifier in terms of F‐measure is 0.9626. The problem of subjective interobserver ability is addressed by quantifying ER score from two expert pathologist and proposed methodology. The intraclass correlation achieved is greater than 0.90. The study has potential advantage of assisting pathologist in decision making over manual procedure and could evolve as a part of automated decision support system with other receptor scoring/analysis procedure.     

Ultrastructural and immunohistochemical study of early repair of alveolar sockets after the extraction of molars from alendronate‐treated rats

The aim of the present research was to analyze ultrastructural and immunohistochemical aspects of the alveolar repair after the extraction of molars of alendronate (ALN)‐treated rats. Wistar rats received 2.5mg/kg body wt/day of ALN during 14 days previously and 7, 14 and 21 days after the extraction of the second mandibular molar. Specimens were fixed in 2% glutaraldehyde + 2.5% formaldehyde under microwave irradiation, decalcified in 4.13% EDTA and paraffin embedded for TRAP histochemistry and immunohistochemistry for OPN, BSP and endoglin, or embedded in Spurr epoxy resin for TEM analysis. Additional specimens had their soft tissues removed and were processed for scanning electron microscopy. The ALN group presented latent TRAP‐positive osteoclasts and nonresorbed alveolar crests with bacterial infection. Mild bone necrosis signs were observed at all time points studied. Ultrastructurally, empty osteocyte lacunae were observed and bone trabeculae surface presented hyalinized aspect. A significant delay in alveolar repair occurred, as well as decreased angiogenesis. ALN treatment provoked mild signs of bone necrosis, despite the high dose employed. The present findings add new information about the ultrastructural aspect of the early repair of rats under ALN treatment and highlight for giving attention when oral surgeries are performed in patients using this drug. Microsc. Res. Tech. 76:633–640, 2013. © 2013 Wiley Periodicals, Inc.     

一类非线性系统的执行器偏差故障检测与诊断

针对一类具有系统建模误差以及含传感器模型不确定项的非线性控制系统，本文提出了一种用于执行器故障检测与诊断的观测器方法。观测器中引入了自适应补偿项，当出现偏差后将对故障及建模不确定项进行补偿。自适应算法中采用了死区算子，增强了算法的鲁棒性。利用自适应阈值进行故障检测，同时利用自适应律进行偏差估计。仿真结果表明了该方法的有效性。     

Neural adaptive observer-based sensor and actuator fault detection in nonlinear systems: Application in UAV

A new online detection strategy is developed to detect faults in sensors and actuators of unmanned aerial vehicle (UAV) systems. In this design, the weighting parameters of the Neural Network (NN) are updated by using the Extended Kalman Filter (EKF). Online adaptation of these weighting parameters helps to detect abrupt, intermittent, and incipient faults accurately. We apply the proposed fault detection system to a nonlinear dynamic model of the WVU YF-22 unmanned aircraft for its evaluation. The simulation results show that the new method has better performance in comparison with conventional recurrent neural network-based fault detection strategies.     

Comparison of microtensile bond strength and resin–dentin interfaces of two self‐adhesive flowable composite resins by using different universal adhesives: Scanning electron microscope study

The aim of this in‐vitro study was to evaluate microtensile bond strength (μTBS) of two different self‐adhesive composites (SACs) on the permanent dentin by applying five different universal adhesive systems. In this study, two different SACs [Vertise Flow (VF), Fusio Liquid Dentin (FLD)] and five different bonding systems [Clearfil Universal Bond Quick (CUB), Single Bond Universal (SBU), All Bond Universal (ABU), Prime Bond Universal (PBU), Futurabond U (FBU)] were used. A total of 22 groups were created in which SACs were applied without adhesive and with five different universal bonding agents in total‐etch (TE) and self‐etch (SE) modes. Two hundred and forty test sticks were obtained using 48 healthy human molar teeth in total with groups having 10 samples each. The μTBS test was applied to each sample in the Universal test device and the data obtained were analyzed statistically by variance analysis and Tukey HSD test. In addition, the resin–dentin interface and fractures modes in the groups were examined by SEM. Upon examining the μTBS results, the highest values were seen in the use of SBU adhesive in TE mode in VF group, while the lowest values were seen in the FLD control group. The difference between the control and experimental groups was found statistically significant (p < .05). Upon comparing the control groups with each other, it was seen that VF group had higher μTBS values than FLD group and the difference between the groups was found statistically significant (p < .05). The μTBS results and SEM images of the study showed that the use of SACs with universal adhesive systems provides a more effective bond strength.     

基于生成对抗网络和自动编码器的机械系统异常检测

现有的机械系统智能诊断模型需要不同健康状态下大量的历史数据和相对应的标签来完成模型训练,但有些机械系统难以采集到异常样本。在无异常样本训练情况下,本文提出一种新的机械系统异常检测方法。新方法结合生成对抗网络和自动编码器,构建了一种编码-解码-再编码的网络模型。所提模型首先通过早期采集的正常样本进行训练,然后用于对未知状态的实时监测样本进行测试,输出两次编码得到的潜在特征的差异值,最后通过观察差异值的变化对系统进行监测。3组实验分析结果验证了方法的有效性。与传统方法相比,新方法检测出异常的时间更早,所得差异值指标在异常发生时幅度增加得更大,且能更稳定表征故障演化过程。