Support vector machine based decision for mechanical fault condition monitoring in induction motor using an advanced Hilbert-Park transform

In this work we suggest an original fault signature based on an improved combination of Hilbert and Park transforms. Starting from this combination we can create two fault signatures: Hilbert modulus current space vector (HMCSV) and Hilbert phase current space vector (HPCSV). These two fault signatures are subsequently analysed using the classical fast Fourier transform (FFT). The effects of mechanical faults on the HMCSV and HPCSV spectrums are described, and the related frequencies are determined. The magnitudes of spectral components, relative to the studied faults (air-gap eccentricity and outer raceway ball bearing defect), are extracted in order to develop the input vector necessary for learning and testing the support vector machine with an aim of classifying automatically the various states of the induction motor.     

Motor square current signature analysis for induction motor rotor diagnosis

Induction machines play an important role in today’s industry. Thus, preventive maintenance combined with fault diagnosis techniques have become an essential issue. One of the most used techniques for the diagnosis of faults in the induction machine is motor current signature analysis (MCSA). This approach presents some limitations for induction motor rotor diagnosis, particularly for small faults. In this paper, a new motor square current signature analysis (MSCSA) fault diagnosis methodology is presented. The proposed technique is based on three main steps: first, the induction motor current is measured; secondly, the square of the current is computed; and finally a frequency analysis of the square current is performed. This technique allows more information to be obtained from a motor with a rotor fault than the classical MCSA approach. Simulation and experimental results are presented in order to confirm the theoretical assumptions. This methodology has also been tested for the identification of two distinct faults (broken bars and rotor eccentricity).     

车用电机轴校正的动力学分析

主要分析了径向位移对转轴传动的危害,找出校正力与校正位移的关系。通过建立材料力学模型、动力学模型,获得理论上的计算数据,并与试验数据进行对比,对结果进行处理、分析,得出动力学模型的校正系数,利于进一步仿真电机轴径向跳动中力与位移的关系。     

旋转机械常见故障诊断的非线性动力学研究综述

对旋转机械中常见的转子偏心、松动、裂纹、碰摩四种故障诊断的非线性分析方法进行了综述,探讨了这些机械系统中可能出现的复杂运动,比较了各种方法的优缺点并对其发展方向做了展望。     

GENERATOR VIBRATION FAULT DIAGNOSIS METHOD BASED ON ROTOR VIBRATION AND STATOR WINDING PARALLEL BRANCHES CIRCULATING CURRENT CHARACTERISTICS

Rotor vibration characteristics are first analyzed,which are that the rotor vibration of fundamental frequency will increase due to rotor winding inter-turn short circuit fault,air-gap dynamic eccentricity fault,or imbalance fault,and the vibration of the second frequency will increase when the air-gap static eccentricity fault occurs.Next,the characteristics of the stator winding parallel branches circulating current are analyzed,which are that the second harmonics circulating current will increase when the rotor winding inter-turn short circuit fault occurs,and the fundamental circulating current will increase when the air-gap eccentricity fault occurs,neither being strongly affected by the imbalance fault.Considering the differences of the rotor vibration and circulating current characteristics caused by different rotor faults,a method of generator vibration fault diagnosis,based on rotor vibration and circulating current characteristics,is developed.Finally,the rotor vibration and circulating current of a type SDF-9 generator is measured in the laboratory to verify the theoretical analysis presented above.     

Fault diagnosis of roll shape under the speed variation in hot rolling mill

The metal processing system usually consists of various components such like motors, work rolls, backup rolls, idle rolls, sensors, etc. Even a simple fault in a single component in the system may cause a serious damage on the final product. It is therefore necessary to diagnose the faults of the components to detect and prevent system failure. Especially, the defects in a work roll are critical to the quality of strip. It is especially difficult to detect faults of a roll by using the existing frequency analysis method if the speed of the roll is changing. In this study, a new diagnosis method for roll eccentricity under the roll speed changes was developed. The new method was induced from analyzing the rolling mechanism by using rolling force models, radius-speed relationship, and measured rolling force, etc. Simulation results by using the field data show that the proposed method is very useful.     

考虑偏心误差的圆弧齿线圆柱齿轮传动特性分析

基于偏心误差对圆弧齿线圆柱齿轮系统啮合性能影响的研究相对较少的现状,介绍了不同加工工艺所得圆弧齿线圆柱齿轮特点,建立轴孔中心存在几何偏心的圆弧齿线圆柱齿轮三维模型,利用商业软件Adams建立考虑偏心误差的圆弧齿线圆柱齿轮动力学仿真模型,分别研究了主动轮存在偏心和从动轮存在偏心及主、从动轮同时存在偏心时圆弧齿线圆柱齿轮系统从动轮速度波动情况。研究结果表明,3种偏心工况下,圆弧齿线圆柱齿轮系统从动轮速度波动情况均呈现周期性变化,偏心量对系统从动轮速度波动情况有一定影响。研究结果为齿轮润滑、故障诊断及齿廓修形等提供了理论基础。     

DWT analysis of numerical and experimental data for the diagnosis of dynamic eccentricities in induction motors

The behaviour of an induction machine during a startup transient can provide useful information for the diagnosis of electromechanical faults. During this process, the machine works under high stresses and the effects of the faults may also be larger than those in steady-state. These facts may help to amplify the magnitude of the indicators of some incipient faults. In addition, fault components with frequencies dependant on the slip evolve in a particular way during that transient, a fact that allows the diagnosis of the corresponding fault and the discrimination between different faults. The discrete wavelet transform (DWT) is an ideal tool for analysing signals with frequency spectrum variable in time. Some research works have applied with success the DWT to the stator startup current in order to diagnose the presence of broken rotor bars in induction machines. However, few works have used this technique for the study of other common faults, such as eccentricities. In this work, time–frequency analysis of the stator startup current is carried out in order to detect the presence of dynamic eccentricities in an induction motor. For this purpose, the DWT is applied and wavelet signals at different levels are studied. Data are obtained from simulations, using a finite element (FE) model of an induction motor, which allows forcing several kinds of faults in the machine, and also from experimental tests. The results show the validity of the approach for detecting the fault and discriminating with respect to other failures, presenting for certain applications (or working conditions) some advantages over the traditional stationary analysis.     

浅谈内燃机机械维修中的问题与应对策略

在我国现阶段工业及机械制造领域发展的过程中,对内燃机的使用是非常广泛的。因此,本文首先分析了内燃机内部常见故障,阐述了现阶段内燃机机械维修中存在的问题,并对内燃机机械维修中的应对策略进行了研究。期待与各位学者共同交流,对我国内燃机机械的维修与养护做出贡献。     

车轴加工基准定位对轴表面残余应力的影响分析

加工基准对车轴表面加工质量有一定影响,为了定量分析由于偏心切削造成的影响程度,从理论上对加工基准误差与加工后车轴表面残余应力的相对关系进行了分析,针对偏心切削对表面残余应力的影响规律进行了研究。设计了在不同偏心量下的切削加工试验,对切削后试件轴表面残余应力进行了测量,试验结果表明,偏心切削对表面残余应力存在一定影响,但是影响程度不是很大。     

Detecting dominant resonant modes of rolling bearing faults using the niching genetic algorithm

In this paper we propose an improvement of methods for adaptive selection of frequency bands containing transients which indicate the presence of the dominant resonant modes of rolling bearing faults using niching genetic algorithm optimization. The main aim of this approach is to diagnose the condition of the bearings and to be able to recognize faults on various parts of bearings and possible combinations of faults. Because the vibration signals corresponding to faults on bearings are typically transients with a wide frequency range occurring around the excited mechanical resonant modes and drowned in the acquired vibration signals, it is necessary to emphasize these excited transients using a matched bank of filters. The dominant resonant modes of a bearing and the system modes produced from fault source are usually unknown, and so there is a need for robust global search methods able to deal with non-linear problems with multiple optima. Instead of applying an optimization method repeatedly for every optimum, non-dominated extensions of the genetic algorithm can be applied only one time to find and maintain multiple optimal solutions. The efficiency of the proposed approach - niching genetic algorithm with fitness sharing - was evaluated using vibration signals acquired on four tapered roller bearings with defined combinations of seeded faults.     

车轴加工基准定位对轴表面残余应力的影响分析

加工基准对车轴表面加工质量有一定影响,为了定量分析由于偏心切削造成的影响程度,从理论上对加工基准误差与加工后车轴表面残余应力的相对关系进行了分析,针对偏心切削对表面残余应力的影响规律进行了研究。设计了在不同偏心量下的切削加工试验,对切削后试件轴表面残余应力进行了测量,试验结果表明,偏心切削对表面残余应力存在一定影响,但是影响程度不是很大。     

Stability behaviour of finite MHD journal bearings

The instability of a rigid rotor supported on MHD journal bearings under the influence of an axial magnetic field and a radial electric field is theoretically analysed in this paper. The MHD Reynold's equation is solved by using the finite element method and stiffness and damping coefficients are obtained. The stability is determined by Routh's criteria. The analysis reveals that the threshold of instability is extended with low values of dimensionless currents at which the load carrying capacities are relatively low. For a bearing with length equal to diameter operating at an eccentricity ratio of 0.6, and Hartmann number of 2, the threshold speed increases by 11% for a dimensionless current of ?1, while there is decrease of 18% when the dimensionless current is ?5, when compared with the hydrodynamic case.     

柱塞泵组件球面缝隙流动特性分析

球面缝隙流动常见于多种机械结构,如柱塞泵中的球面配流副、球铰副等,然而针对球面副半径不等及存在偏心的缝隙流动特性研究较少。针对2个半径不相等的球面元件形成球面缝隙且其球心存在一定偏心时,根据球坐标系下的N-S方程对其缝隙中流体的速度分布、压力分布、泄漏流量及流体的承载量进行了分析,得到了相应的解析表达式,依此可知,半径相等且球心存在一定偏心时球面缝隙中流体的相关解析表达式;同时,得到了仅与球面缝隙流动自身结构有关的球面支撑泄漏系数和球面支撑承载系数,进一步为形成球面缝隙的机械结构(如柱塞泵中的球面配流副、球铰副等)相关设计提供理论参考;最后以柱塞泵中球铰副形成的球面缝隙为例,对其缝隙中流体的压力分布、速度分布等参数进行了分析。     

Erosion,treatise on materials science and technology,volume 16: Edited by Carolyn M. Preece; published by Academic Press,New York, 1979; 450 pp.; price, $49.00

A generalized Reynolds equation has been derived for a magnetohydrodynamic journal bearing with the magnetic field perpendicular to the bearing axis and the electric current in the axial direction. Solution of the Reynolds equation is expressed in the form of a double series. The analysis is supported by sample results of static characteristics computed for an aspect ratio λ of 1.0 and an eccentricity ratio ? of 0.6.     

静偏心对挤压油膜阻尼器转子抗振性能的影响及控制方法

研究了静偏心对挤压油膜阻尼器减振与转子抗振性能的影响。结果表明,随着静偏心增大,阻尼器的减振性能先增强再减弱,而转子抗振性能则大幅下降。分析了引起阻尼器静偏心的原因,并根据各因素的特征提出了控制方法。采用预置偏心,合理的结构、工艺设计有利于控制转子自重与设计、加工装配引起的静偏心。采用较小的设计偏心比,有利于提高机动条件下阻尼器转子的抗振性能。     

MISEP盲分离算法在振动信号分析中的应用

利用MISEP算法对直升机齿轮箱振动信号的非线性混叠进行了盲源分离,分离出了轴承故障振动信号,并将该方法应用于实际的飞机发动机的振动信号分析,分离结果表明MISEP盲源分离算法是机械故障诊断领域的一个有效的信号处理方法。     

Detection of combined faults in induction machines with stator parallel branches through the DWT of the startup current

The main objective of this paper is to diagnose the presence of combined faults in induction machines. For this purpose, a methodology based on the application of the Discrete Wavelet Transform (DWT) to the stator startup current is used. This approach was applied in previous works with success to the diagnosis of rotor asymmetries and mixed eccentricities in motors with different sizes and conditions. However, as most of the diagnosis methods hitherto developed, the application of the proposed approach was circumscribed to situations in which a single fault was present in the machine. In addition, the influence of other phenomena such as load torque oscillations or voltage fluctuations was studied, but without considering the combination of these phenomena and the fault in the machine. This work is intended, first, to apply the proposed transient-based methodology to several cases in which different faults (rotor asymmetries, mixed eccentricities and inter-turn and inter-coil stator short-circuits) are simultaneously present in the machine and, second, to apply it to cases regarding faults combined with other phenomena making difficult the diagnosis, such as load torque oscillations. Interesting considerations regarding the preponderance of the effects of some of the faults are also done in the paper. The application of the methodology is focused on induction machines with stator parallel branches; in this sense, the suitability of the use either of the phase current or of the branch current for the diagnosis of each particular fault is analysed. The results look promising with regard to the validity of the methodology for the reliable discrimination of simultaneous electromechanical faults and the diagnosis of faults combined with other phenomena.     

盲解卷积的机械振动信号分离技术

针对机械振动信号往往是多个信号卷积混合的结果,阐述了卷积混合的模型和原理.利用扩展的H-J网络结构,给出了在线实时的盲解卷积迭代算法,并通过仿真试验验证了算法的有效性和准确性.该法与传统的傅里叶变换频谱分析相比,能获得更多的振源振动信息,可更准确地进行机械故障诊断.     

Transient tracking of low and high-order eccentricity-related components in induction motors via TFD tools

The present work is focused on the diagnosis of mixed eccentricity faults in induction motors via the study of currents demanded by the machine. Unlike traditional methods, based on the analysis of stationary currents (Motor Current Signature Analysis (MCSA)), this work provides new findings regarding the diagnosis approach proposed by the authors in recent years, which is mainly focused on the fault diagnosis based on the analysis of transient quantities, such as startup or plug stopping currents (Transient Motor Current Signature Analysis (TMCSA)), using suitable time-frequency decomposition (TFD) tools. The main novelty of this work is to prove the usefulness of tracking the transient evolution of high-order eccentricity-related harmonics in order to diagnose the condition of the machine, complementing the information obtained with the low-order components, whose transient evolution was well characterised in previous works. Tracking of high-order eccentricity-related harmonics during the transient, through their associated patterns in the time-frequency plane, may significantly increase the reliability of the diagnosis, since the set of fault-related patterns arising after application of the corresponding TFD tool is very unlikely to be caused by other faults or phenomena. Although there are different TFD tools which could be suitable for the transient extraction of these harmonics, this paper makes use of a Wigner-Ville distribution (WVD)-based algorithm in order to carry out the time-frequency decomposition of the startup current signal, since this is a tool showing an excellent trade-off between frequency resolution at both high and low frequencies. Several simulation results obtained with a finite element-based model and experimental results show the validity of this fault diagnosis approach under several faulty and operating conditions. Also, additional signals corresponding to the coexistence of the eccentricity and other non-fault related phenomena making difficult the diagnosis (fluctuating load torque) are included in the paper. Finally, a comparison with an alternative TFD tool - the discrete wavelet transform (DWT) - applied in previous papers, is also carried out in the contribution. The results are promising regarding the usefulness of the methodology for the reliable diagnosis of eccentricities and for their discrimination against other phenomena.