灰色理论在旋转机械故障诊断与预报中的应用

利用灰色理论的关联度分析实现了旋转机械故障的精密诊断 ,利用灰色模型( GM)实现了旋转机械的状态预测及故障预报 ,并用 C语言编制了一套完整的旋转机械灰色故障诊断、状态预测与故障预报软件。同时本文对某厂透平机进行了全面的计算机诊断与预报 ,通过现场对该透平机检查发现故障与本软件诊断结果一致 ,进而揭示了利用灰色理论开发旋转机械故障诊断和预报系统的可行性。本软件为旋转机械故障诊断专家系统的开发提供了新的借鉴     

Hierarchical diversity entropy for the early fault diagnosis of rolling bearing

Nonlinear Dynamics - Intelligent fault diagnosis provides great convenience for the prognostic and health management of the rotating machinery. Recently, the multiscale diversity entropy has been...     

An enhanced domain-adversarial neural networks for intelligent cross-domain fault diagnosis of rotating machinery

Nonlinear Dynamics - In recent years, numerous studies have explored fault diagnosis methods for rotating machinery based on deep learning. For deep learning-based algorithms, the performance of...     

分形维数在大型旋转机械故障诊断中的应用

为了识别大型旋转机械的故障模式,运用分形理论,提出了分段关联维数的计算方法,并以分段关联维数为特征量,通过建立状态距离函数,实现了模式识别。该方法克服了通常只通过计算一段数据的关联维数就进行故障识别的缺点。通过对仿真信号、滚动轴承实测信号的诊断,表明所提出方法的有效性,具有实用价值。     

竖向动载荷作用下平面框架结构水平动力响应分析

固定旋转机械引起的结构振动及其减、隔振控制是设备减、隔振领域一个十分重要的研究课题.以往的研究主要关注结构的竖向振动,而结构水平向振动往往被忽略.论文以设置有固定旋转设备的单层框架结构为例,分析了结构水平和竖向动位移幅值与结构固有频率、设备安装位置及设备运转频率之间的关系.研究结果表明,在特定条件下,结构水平向振动响应可能大于竖向振动响应,这一现象在设计时应引起足够的重视.     

FAULT DIAGNOSIS OF ROTATING MACHINERY USING KNOWLEDGE-BASED FUZZY NEURAL NETWORK

A novel knowledge-based fuzzy neural network (KBFNN) for fault diagnosis is presented.Crude rules were extracted and the corresponding dependent factors and antecedent coverage factors were calculated firstly from the diagnostic sample based on rough sets theory.Then the number of rules was used to construct partially the structure of a fuzzy neural network and those factors were implemented as initial weights,with fuzzy output parameters being optimized by genetic algorithm.Such fuzzy neural network was called KBFNN.This KBFNN was utilized to identify typical faults of rotating machinery. Diagnostic results show that it has those merits of shorter training time and higher right diagnostic level compared to general fuzzy neural networks.     

Dual-mode global stabilization of high-order saturated integrator chains: LMI-based MPC combined with a nested saturated feedback

Nonlinear Dynamics - In the active magnetic bearings (AMBs) supported rotating machinery, touchdown bearings are considered as safety devices to support the rotor in the deficiency of...     

Nonlinear design analysis of centrifugal pendulum vibration absorbers: an intrinsic geometry-based framework

Nonlinear Dynamics - The centrifugal pendulum vibration absorber (CPVA) is a device whose purpose is the reduction in torsional vibrations in rotating and reciprocating machinery. Over the last...     

The numerical modeling of rotor–stator rubbing in rotating machinery: a comprehensive review

Nonlinear Dynamics - The rotor–stator rubbing in rotating machinery generated as a consequence of rotor imbalance, shaft misalignment, and casing deformation is a potential threat to the...     

Nonlinear modeling and analysis of rotors supported by magnetorheological squeeze film journal bearings

Meccanica - The driver coupled to a driven system through mechanical couplings is very common in rotating machinery. These couplings can present angular and parallel misalignments with more or less...     

Research on Haar Spectrum in fault diagnosis of rotating machinery

In this paper,Haar Transform(HT)is used in the fault diagnosis of rotatingmachinery,and the“Impulse Sharpness”is presented as a diagnostic index.At present,Fourier Spectrumanalysis is most widely used Compared with FFT,HT is more rapid incomputation and more effective in discrete approximation.It’s very suitable for theextraction of pulses in the signal.However,HT has some shortcomings.It’s greatlyaffected by the starting point and length of the sample.Here,the authors present a methodto improve the stability and comparability of Haar Spectrum.The fault imitating test ofrolling bearing is carried out,and the results obtained have verified the sensitivity of HaarSpectrum and Impulse Index to the fault.     

Dynamic instability and steady-state response of an elliptical cracked shaft

An elliptical front crack has been found to be more accurate and realistic for modeling the transverse surface crack in rotating machinery compared with the widely used straight front crack. When the shaft rotates, the elliptical crack opens and closes alternatively, due to gravity, and thus, a “breathing effect” occurs. This variance in shaft stiffness is time-periodic, and hence, a parametrically excited system is expected. Therefore, the dynamic instability and steady-state response of a rotating shaft containing an elliptical front crack are studied in the paper. The local flexibility due to the crack is derived, and the governing equations of the crack shaft system are established using the assumed modes method. Utilizing the Bolotin’s method and harmonic balance method, the boundaries of two typical instability regions and maximum response amplitude of the cracked shaft could be computed numerically. The elliptical crack parameters (depth, shape factor and position) and damping are, respectively, considered and discussed for their effects on the dynamic behavior of the elliptical cracked shaft. Some research results might be helpful for the crack detection in rotating machinery.     

Elimination of periodic coefficients from the equations of motion of asymmetric shafts in anisotropic bearings

Summary A method is given for eliminating periodic coefficients from rotordynamic systems in which imperfections are accounted for simultaneously in the stationary and rotating components. It is well known that periodic coefficients are unavoidable in such systems whether the equations of motion are formulated in the stationary frame or the rotating frame of reference. Since such equations are more difficult to solve compared to those with constant coefficients, it is desirable to devise a transformation procedure which eliminates periodic coefficients from the governing equations. In this paper, such a procedure is presented. A considerable simplification is thereby obtained of the equations of motion of rotating machinery in which imperfections exist stators and rotors.     

Time-resolved particle imaging velocimetry for the investigation of rotating stall in a radial pump

The operating range of turbomachines is limited in terms of the low flow rate by instabilities appearing in flow-leading parts of the machinery resulting in the creation of vortices. If the flow is further throttled, stall cells can start to propagate in the impeller at a fraction of the rotor speed. This article presents an investigation of rotating stall at different flow rates in a radial pump using time-resolved particle imaging velocimetry (PIV). This technique was used to investigate the flow field at the same position in every channel of the impeller during several revolutions. Frequency analysis was applied to the measured velocities to calculate the angular speed of the rotating stall in the impeller. The interest of time-resolved PIV to understand rotating stall is demonstrated, as it allows measurement of transient, irregularly appearing flow fields.     

Non-linear dynamic analysis of a HSFD mounted gear-bearing system

An investigation is carried out on the systematic analysis of the dynamic behavior of the hybrid squeeze-film damper (HSFD) mounted a gear-bearing system with strongly non-linear oil-film force and gear meshing force in the present study. The dynamic orbits of the system are observed using bifurcation diagrams plotted using the dimensionless unbalance coefficient, damping coefficient and the dimensionless rotating speed ratio as control parameters. The non-dimensional equations of the gear-bearing system are solved using the fourth order Runge-Kutta method. The onset of chaotic motion is identified from the phase diagrams, power spectra, Poincaré maps, bifurcation diagrams, maximum Lyapunov exponents and fractal dimension of the gear-bearing system. The results presented in this study provide some useful insights into the design and development of a gear-bearing system for rotating machinery that operates in highly rotating speed and highly non-linear regimes.     

A comparison of stability computational methods for periodic solution of nonlinear problems with application to rotordynamics

In this paper a comparative study of five different stability computational methods based on the Floquet theory is presented. These methods are compared in terms of accuracy and CPU performance. Tests are performed on a set of nonlinear problems relevant to rotating machinery with rotor-to-stator contact and a variable number of degrees of freedom, whose periodic solutions are computed with the Harmonic Balance Method (HBM).     

Bifurcations in the response of a rigid rotor supported by load sharing between magnetic and auxiliary bearings

Auxiliary bearings are utilized in practical installations of magnetically suspended rotating machines with the main functions to provide support to the rotating machines during their non-operational period, and to protect the magnetic bearings and the rotating assembly from being damaged due to power loss during operation. The relatively small clearances of these bearings, which are typically half of that of the magnetic bearings, may at time cause contact between the rotor and these bearings to occur even during normal operation of the rotating machines. The work presented herein examines the bifurcations in the response of a rigid rotor supported by load sharing between magnetic and auxiliary bearings, which occurs during contact between the rotor and the auxiliary bearings. Numerical results revealed the occurrence of period-doubling bifurcation resulting in vibrations of period-2, -4, -8, -16 and -32, as well as quasi-periodic and chaotic vibrations. The results further showed that for a relatively small rotor imbalance magnitude, which is within the prescribed level of certain classes of practical rotating machinery, such nonlinear dynamical phenomena would not have been discovered had the auxiliary bearings forces been omitted in the model of the rotor-bearing system. As these bearings are essential elements in practical installations of magnetically supported rotating machines, failure to include them in the rotor-bearing model may result in incorrect prediction of the rotor’s vibration response.     

C- METHOD AND ITS APPLICATION TO ENGINEERING NONLINEAR DYNAMICAL PROBLEMS

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Response analysis of a dual-disc rotor system with multi-unbalances–multi-fixed-point rubbing faults

Rotor unbalance and rub-impact are major concerns in rotating machinery. In order to study the dynamic characteristics of these machinery faults, a dual-disc rotor system capable of describing the mechanical vibration resulting from multi-unbalances and multi-fixed-point rub-impact faults is formulated using Euler beam element. The Lankarani–Nikravesh model is used to describe the nonlinear impact forces between discs and casing convex points, and the Coulomb model is applied to simulate the frictional characteristics. To predict the moment of rub-impact happening, a linear interpolation method is carried out in the numerical simulation. The coupling equations are numerically solved using a combination of the linear interpolation method and the Runge–Kutta method. Then, the dynamic behaviours of the rotor system are analysed by the bifurcation diagram, whirl orbit, Poincaré map and spectrum plot. The effects of rotating speed, phase difference of unbalances, convex point of casing and initial clearance on the responses are investigated in detail. The numerical results reveal that a variety of motion types are found, such as periodic, multi-periodic and quasi-periodic motions. Moreover, the energy transfer between the compressor disc and the turbine disc occurs in the multi-fixed-point rubbing faults. Compared with the parameters of the turbine disc, those of the compressor disc can affect the motion of the rotor system more significantly. That is, the responses exhibit simple 1T-periodic motion in the wide range of rotating speed under the conditions of sharp convex point and larger initial clearance. These forms of dynamic characteristics can be effectively used to diagnose the fixed-point rub-impact faults.