Model-based fault diagnosis in continuous dynamic systems

Traditional fault detection and isolation methods are based on quantitative models which are sometimes difficult and costly to obtain. In this paper, qualitative bond graph (QBG) reasoning is adopted as the modeling scheme to generate a set of qualitative equations. The QBG method provides a unified approach for modeling engineering systems, in particular, mechatronic systems. An input-output qualitative equation derived from QBG formalism performs continuous system monitoring. Fault diagnosis is activated when a discrepancy is observed between measured abnormal behavior and predicted system behavior. Genetic algorithms (GA's) are then used to search for possible faulty components among a system of qualitative equations. In order to demonstrate the performance of the proposed algorithm, we have tested it on a laboratory scale servo-tank liquid process rig. Results of the proposed model-based fault detection and diagnosis algorithm for the process rig are presented and discussed.     

Multiple parametric faults diagnosis for power electronic circuits based on hybrid bond graph and genetic algorithm

Aiming at the problem to diagnosis multiple parametric faults in power electronic circuits, a new diagnosis framework based on hybrid bond graph (HBG) and genetic algorithm (GA) is presented. Firstly, the circuits are modeled by HBG modeling technique, in which the equivalent models of the key components are considered. Then, a set of residuals equations and a fault signature matrix (FSM) are derived from the HBG model. Each faulty component exhibits their degradation symptoms on residuals equations. Thus, faults can be detected by comparing residuals with fault detection thresholds and isolated based on FSM. Finally, GA method is employed to identify the component faults. The fitness function of GA is constructed by the residuals equations in which the faulty components are contained. Simulation and experiment are carried out to verify the feasibility and effectiveness. The results show that the developed method is applicable to diagnosis both single and multiple parametric faults.     

遗传程序设计在故障诊断中的研究与应用

作为一种新兴的强大的智能优化技术，遗传程序设计已经广泛地应用在工程科学的许多领域。这里重点研究了遗传程序设计方法在故障诊断领域中的应用，以推动和实现智能诊断。此外，在构建的实验台上模拟齿轮箱齿轮的典型故障形式，利用遗传程序设计方法对其提取的征兆参数进行处理分析，实现故障的模式识别。     

盾构机故障诊断专家系统综合推理机的研制

介绍了基于故障树模型的主知识库设计,着重论述了综合推理机的设计.综合推理机由基于实时参数的实时诊断推理机、基于规则的交互推理机、基于不确定性推理的自动推理机组成.将其应用于盾构机故障诊断,结果表明该综合推理机诊断迅速、准确率高且能满足多方面的故障诊断要求.     

Module level fault diagnosis for analog circuits based on system identification and genetic algorithm

This paper proposes a new module level fault diagnosis method for analog circuits. Firstly, the transfer function is constructed according to the relationship between output and input of the circuit under test (CUT). Every system parameter of the transfer function is expressed by several component parameters. These components are divided into several modules. Then, the way of objective function optimization based on genetic algorithm (GA) is adopted to solve nonlinear equations, which are obtained by multi-frequency testing. Finally, the module level faults are detected by comparing the estimated system parameters to their normal values. The results show that the proposed method is effective to identify system parameters and locate module level faults.     

一种改进的小波神经网络在故障诊断中的应用

针对现有BP网络在故障诊断中存在的问题,提出将小波函数与神经网络结合构成小波网络,代替BP网络用于故障诊断。对其存在的易将未知故障化为某一已知故障的问题,提出将小波网络加以改进,对诊断结果做最后的验证,以确保诊断结果的正确,同时也能准确地发现新的故障,并将其另开新类。仿真实验表明小波网络较BP网络更适用于故障诊断,且对小波网络进行的改进对新故障的发现也很有效。     

FTA在液压故障诊断系统中的应用

故障树原理是故障诊断系统的基础,在研究液压系统的基础上,对故障树分析法的原理、建立过程及特点进行了阐述,并建立了液压系统的故障树。液压系统故障树是通过分析液压系统的故障形式、液压系统的结构、液压系统中的零部件与系统之间的逻辑关系而建立的。将故障树与PLC点位监测相结合,由数控系统给出专家结论,提供了一种故障树原理在故障诊断系统中的应用实例。这种液压故障诊断系统在实际应用中具有推广价值。     

Multiple manifolds analysis and its application to fault diagnosis

A novel approach to fault diagnosis is proposed using multiple manifolds analysis (MMA) to extract manifold information from the vibration signals collected from a mechanical system. The basic idea of MMA is to reconstruct a manifold by embedding time series into a high-dimensional phase space. The tangent direction of the neighborhood for each point is then used to approximate its local geometry. The variation of the multiple manifolds representing different states of the mechanical system can be revealed by performing multi-way principal component analysis. The vibration signals acquired from roller bearings are employed to validate the proposed algorithms. Test results show that the proposed MMA-based approach can interpret different machine conditions and is effective to the fault diagnosis, and the MMA-based fault clustering and trend analysis algorithms have outperformed the conventional fault diagnosis methods.     

A hybrid fault diagnosis approach based on mixed-domain state features for rotating machinery

To make further improvement in the diagnosis accuracy and efficiency, a mixed-domain state features data based hybrid fault diagnosis approach, which systematically blends both the statistical analysis approach and the artificial intelligence technology, is proposed in this work for rolling element bearings. For simplifying the fault diagnosis problems, the execution of the proposed method is divided into three steps, i.e., fault preliminary detection, fault type recognition and fault degree identification. In the first step, a preliminary judgment about the health status of the equipment can be evaluated by the statistical analysis method based on the permutation entropy theory. If fault exists, the following two processes based on the artificial intelligence approach are performed to further recognize the fault type and then identify the fault degree. For the two subsequent steps, mixed-domain state features containing time-domain, frequency-domain and multi-scale features are extracted to represent the fault peculiarity under different working conditions. As a powerful time-frequency analysis method, the fast EEMD method was employed to obtain multi-scale features. Furthermore, due to the information redundancy and the submergence of original feature space, a novel manifold learning method (modified LGPCA) is introduced to realize the low-dimensional representations for high-dimensional feature space. Finally, two cases with 12 working conditions respectively have been employed to evaluate the performance of the proposed method, where vibration signals were measured from an experimental bench of rolling element bearing. The analysis results showed the effectiveness and the superiority of the proposed method of which the diagnosis thought is more suitable for practical application.     

滚动轴承数据库设计及其在故障诊断中的应用

针对国内外滚动轴承种类繁多、编号复杂以及轴承故障特征频率难以获得的现状,利用Power Builder强大的数据库功能,设计出一套数据完整、查询快捷方便,并与瑞典SKF公司的轴承故障特征频率参数相吻合的数据库系统,同时举例说明该系统可广泛应用于设备状态监测、故障诊断和预知维修领域。     

Support vector machine with genetic algorithm for machinery fault diagnosis of high voltage circuit breaker

Based on empirical mode decomposition (EMD) method and support vector machine (SVM), a new method for the fault diagnosis of high voltage circuit breaker (CB) is proposed. The feature extraction method based on improved EMD energy entropy is detailedly analyzed and SVM is employed as a classifier. Radial basis function (RBF) is adopted as the kernel function of SVM and its kernel parameter γ and penalty parameter C must be carefully predetermined in establishing an efficient SVM model. Therefore, the purpose of this study is to develop a genetic algorithm-based SVM (GA-SVM) model that can determine the optimal parameters of SVM with the highest accuracy and generalization ability. The classification accuracy of this GA-SVM approach is tried by real dataset and compared with the SVM, which has randomly selected kernel function parameters. The experimental results indicate that the classification accuracy of this GA-SVM approach is more superior than that of the artificial neural network and the SVM which has constant and manually extracted parameters.     

小波分析在深孔加工刀具故障诊断中的应用

在小波分析的理论基础上 ,讨论小波包在故障信息提取中的应用。小波包频段能量故障特征提取方法 ,克服了传统的信号处理方法不易提取微弱故障信息的不足。并举例说明该法的实用性     

A novel fault diagnosis model for gearbox based on wavelet support vector machine with immune genetic algorithm

A novel intelligent diagnosis model based on wavelet support vector machine (WSVM) and immune genetic algorithm (IGA) for gearbox fault diagnosis is proposed. Wavelet support vector machine is a powerful novel tool for solving the diagnosis problem with small sampling, nonlinearity and high dimension. Immune genetic algorithm is developed in this study to determine the optimal parameters for WSVM with the highest accuracy and generalization ability. Moreover, the feature vectors for fault diagnosis are obtained from vibration signal that preprocessed by empirical mode decomposition (EMD). The experimental results indicate that this proposed approach is an effective method for gearbox fault diagnosis, which has more strong generalization ability and can achieve higher diagnostic accuracy than that of the artificial neural network and the SVM which has randomly extracted parameters.     

第二代小波变换及其在故障诊断中的应用

第二代小波变换是一种基于提升原理的时域变换方法,介绍了第二代小波变换原理,给出了一种第二代小波变换过程中预测算子和提升算子的求取方法,在此基础上将第二代小波变换应用于矿用通风机的故障诊断中。结果表明该方法可以有效地分解信号和提取特征信息,在矿山机械故障诊断中具有良好的应用前景．     

Using genetic algorithms for the optimization of mechanisms

This work examines the possibility of using genetic algorithms for the optimization of the loads transmitted in mechanisms. The variables of design are the relative positions of the various connections, considered in a comparative manner. The minimization of the loads transmitted in the connections is achieved by optimizing the respective positions of those lead to less expensive solutions for bearings and sections of beams. The examples show that using this stochastic method is an efficient way to minimize loads in mechanisms.     

Random forests classifier for machine fault diagnosis

This paper investigates the possibilities of applying the random forests algorithm (RF) in machine fault diagnosis, and proposes a hybrid method combined with genetic algorithm to improve the classification accuracy. The proposed method is based on RF, a novel ensemble classifier which builds a number of decision trees to improve the single tree classifier. Although there are several existing techniques for faults diagnosis, the application research on RF is meaningful and necessary because of its fast execution speed, the characteristics of tree classifier, and high performance in machine faults diagnosis. The proposed method is demonstrated by a case study on induction motor fault diagnosis. Experimental results indicate the validity and reliability of RF-based diagnosis method.     

模糊神经网络在电气设备故障检测与诊断中的应用

电力变压器故障的机理难以应用准确的数学模型加以描述,故障现象与故障原因之间存在着很多不确定因素。本文应用人工网络理论,并利用模糊理论预处理数据,建立了基于模糊神经的变压器故障检测诊断模型。结果表明,该方法对变压器进行故障检测诊断是有效的,同时对其它电气设备的故障诊断也具有参考意义。     

人工神经网络在机械故障诊断中的应用

针对传统的机械故障诊断方法的局限性,提出将人工神经网络应用于机械故障诊断中。由于BP算法存在收敛速度慢及易陷入局部极小等缺陷,利用实数编码改进遗传算法对神经网络的权值和阈值进行优化训练,并把训练好的神经网络用于机械振动信号预测及机械故障诊断中。通过对机械设备振动信号的预测,可以及早发现故障,及时消除故障隐患,为企业节省大量的维修时间和维修费用,提高企业的生产率。     

CNC装置故障诊断专家系统的研究与应用

简述了专家系统应用于ＣＮＣ故障诊断的重要意义。结合ＣＮＣ系统故障诊断问题的特点，探讨了ＣＮＣ故障诊断专家系统的结构以及实现方法     

基于键合图的RV减速器动力学仿真

为研究RV减速器系统的弹性特性、齿轮间啮合刚度和阻尼对系统动态特性的影响,需要对系统进行建模和仿真分析。简述了RV减速器的结构、传动特点并对功率流进行分析,基于键合图理论建立RV减速器的动态仿真模型,推导出系统的状态方程,用Matlab进行系统动力学仿真分析,得到输出转速及加速度曲线,较好地反映了系统的动态特性。为RV减速器的设计、改进提供一定的理论依据。仿真结果表明:键合图模型是一种相当优越的数学模型,键合图理论与方法为RV减速器动力学特性的研究提供了一种新方法与途径。