Cracked Shaft Damage Identification via Symmetry Breaking Active Magnetic Bearing Control and Interrogation

2011 ◽  
Author(s):  
J. Zhao ◽  
H. A. DeSmidt
Keyword(s):  
Symmetry Breaking ◽  
Structural Damage ◽  
Damage Identification ◽  
Magnetic Bearing ◽  
Active Magnetic Bearing ◽  
Crack Model ◽  
Lagrange Principle ◽  
Disk System ◽  
Data Set ◽  
Loop Control

A new vibration-based damage identification methodology for cracked rotor systems with periodically time-varying dynamics is developed and demonstrated on a shaft-disk system. This approach is based Floquet theory and utilizes measured changes in the system natural frequencies to estimate the severity and location of shaft structural cracks during operation. The damage identification is enhanced through the use of an Active Magnetic Bearing with adjustable support stiffness and acceleration feedback. Here, a novel symmetry-breaking closed-loop control is employed during the iterative damage identification process to enrich the data set by removing the Eigen degeneracy of the symmetric shaft structure. This approach enables full damage identification from a single sensor and hence without requiring measured modeshape information. The dynamical model of system is built based on the Lagrange principle and the assumed mode method while the crack model is based on fracture mechanics. The method is synthesized via harmonic balance and numerical examples for a shaft/disk system demonstrate the effectiveness in detecting both location and severity of the structural damage.

scholarly journals A Mahalanobis Distance Cumulant-Based Structural Damage Identification Method with IMFs and Fitting Residual of SHM Measurements

2020 ◽  
Vol 2020 ◽  
pp. 1-17
Author(s):  
Chuang Chen ◽  
Yinhui Wang ◽  
Tao Wang ◽  
Xiaoyan Yang
Keyword(s):  
Mahalanobis Distance ◽  
Structural Damage ◽  
Damage Identification ◽  
Feature Vector ◽  
Recursive Algorithm ◽  
Intrinsic Mode Functions ◽  
Data Set ◽  
Identification Method ◽  
Structural Damage Identification ◽  
Emd Method

Data-driven damage identification based on measurements of the structural health monitoring (SHM) system is a hot issue. In this study, based on the intrinsic mode functions (IMFs) decomposed by the empirical mode decomposition (EMD) method and the trend term fitting residual of measured data, a structural damage identification method based on Mahalanobis distance cumulant (MDC) was proposed. The damage feature vector is composed of the squared MDC values and is calculated by the segmentation data set. It makes the changes of monitoring points caused by damage accumulate as “amplification effect,” so as to obtain more damage information. The calculation method of the damage feature vector and the damage identification procedure were given. A mass-spring system with four mass points and four springs was used to simulate the damage cases. The results showed that the damage feature vector MDC can effectively identify the occurrence and location of the damage. The dynamic measurements of a prestress concrete continuous box-girder bridge were used for decomposing into IMFs and the trend term by the EMD method and the recursive algorithm autoregressive-moving average with the exogenous inputs (RARMX) method, which were used for fitting the trend term and to obtain the fitting residual. By using the first n-order IMFs and the fitting residual as the clusters for damage identification, the effectiveness of the method is also shown.

scholarly journals Exploration of NDE Properties of AMB Supported Rotors for Structural Damage Detection

2010 ◽  
Author(s):  
Jerzy T. Sawicki ◽  
Dmitry L. Storozhev ◽  
John D. Lekki
Keyword(s):  
Structural Damage ◽  
Magnetic Bearing ◽  
Active Magnetic Bearing ◽  
Line Detection ◽  
Control Loop ◽  
Structural Damage Detection ◽  
Cracked Rotor ◽  
Rotating Shaft ◽  
On Line ◽  
Combination Frequencies

This paper addresses self-diagnostic properties of AMB (active magnetic bearing) supported rotors for on-line detection of the transverse crack on a rotating shaft. In addition to pure levitation, the rotor supporting bearing also serves as an actuator that transforms current signals additionally injected into the control loop into the superimposed specially selected excitation forces into the suspended rotor. These additional excitations induce combination frequencies in the rotor response, providing unique signatures for the presence of crack. The background of theoretical modeling, experimental and computer simulation results for the AMB supported cracked rotor with self-diagnostic excitation forces are presented and discussed.

Destabilization of Forward Rub in Rotor Magnetic Bearing Systems Using Actively Controlled Auxiliary Bearings

2010 ◽  
Author(s):  
Iain S. Cade ◽  
M. Necip Sahinkaya ◽  
Clifford R. Burrows ◽  
Patrick S. Keogh
Keyword(s):  
Design Feature ◽  
Magnetic Bearing ◽  
Open Loop ◽  
Active Magnetic Bearing ◽  
Loop Control ◽  
Bending Mode ◽  
Operating Limits ◽  
Auxiliary Bearing ◽  
Contact Free ◽  
Bearing System

During fault conditions, rotor displacements in magnetic bearing systems may potentially exceed safety/operating limits. Hence it is a common design feature to incorporate auxiliary bearings adjacent to the magnetic bearings for the prevention of rotor/stator contact. During fault conditions the rotor may come into contact with the auxiliary bearings, which may lead to continuous rub type orbit responses. In particular, forward rub responses may become persistent. This paper advances the methodology by considering an actively controlled auxiliary bearing system. An open-loop control strategy is adopted to provide auxiliary bearing displacements that destabilize established forward rub orbit responses. A theoretical approach is undertaken to identify auxiliary bearing motion limits at which forward rub responses become unstable. Experimental validation is then undertaken using a rotor/active magnetic bearing system with an actively controlled auxiliary bearing system under piezoelectric actuation. Two different operating speeds below the first bending mode of the rotor are considered and the applied harmonic displacements of the auxiliary bearing are shown to be effective in restoring contact free levitation.

scholarly journals Harmonic Transfer Function Based Damage Identification of Breathing Cracked Jeffcott Rotor

2016 ◽  
Vol 2016 ◽  
pp. 1-13 ◽  
Author(s):  
Jie Zhao ◽  
Hans DeSmidt ◽  
Meng Peng
Keyword(s):  
Transfer Function ◽  
Damage Identification ◽  
Strain Energy Release ◽  
Damage Parameter ◽  
Rotor System ◽  
Crack Model ◽  
Identification Algorithm ◽  
Lagrange Principle ◽  
Jeffcott Rotor ◽  
Vibration Responses

This paper proposes a vibration-based damage identification method based on 6-dof Jeffcott rotor system, which is based on harmonic balance and Newton-Raphson methods. First, the equations of motion are derived by using energy method and Lagrange principle. The crack model is based on strain energy release rate (SERR) in fracture mechanics and modified to accommodate 6-dof Jeffcott rotor model. Then, Gear’s method is used to solve the vibration responses of nominal and damaged rotor systems. By processing vibration responses, the transfer function shifts between nominal and damaged systems are taken as the input of damage identification algorithm. Finally, damage severity can be correlated with the damage parameter estimated via developed damage identification model. Numerical examples are shown to demonstrate the effectiveness in identifying the breathing crack in the rotor system.

scholarly journals Exploration of NDE Properties of AMB Supported Rotors for Structural Damage Detection

2011 ◽  
Vol 133 (10) ◽  
Author(s):  
Jerzy T. Sawicki ◽  
Dmitry L. Storozhev ◽  
John D. Lekki
Keyword(s):  
Structural Damage ◽  
Transverse Crack ◽  
Magnetic Bearing ◽  
Active Magnetic Bearing ◽  
Control Loop ◽  
Structural Damage Detection ◽  
Cracked Rotor ◽  
Rotating Shaft ◽  
Simulation Results ◽  
Combination Frequencies

This paper addresses self-diagnostic properties of active magnetic bearing (AMB) supported rotors for online detection of the transverse crack on a rotating shaft. In addition to pure levitation, the rotor supporting bearing also serves as an actuator that transforms current signals additionally injected into the control loop into the superimposed specially selected excitation forces into the suspended rotor. These additional excitations induce combination frequencies in the rotor response, providing unique signatures for the presence of crack. The background of theoretical modeling, experimental, and computer simulation results for the AMB supported cracked rotor with self-diagnostic excitation forces are presented and discussed.

Rotor Vibration Control of Active Magnetic Bearing System Using Adaptive Forced Balancing Method

2012 ◽  
Vol 268-270 ◽  
pp. 1527-1530
Author(s):  
Tao Zhang ◽  
Wei Ni ◽  
Sha Sha Wu ◽  
Hui Ping Zhang ◽  
Jian Xiang Ji
Keyword(s):  
Closed Loop ◽  
Rotational Frequency ◽  
Magnetic Bearing ◽  
Active Magnetic Bearing ◽  
Rotor Vibration ◽  
Loop Control ◽  
Closed Loop Control System ◽  
Loop Control System ◽  
Feedback Control Systems ◽  
Sinusoidal Disturbance

The adaptive forced balancing (AFB) method was used to estimate and eliminate the rotor vibration with unknown amplitudes and frequencies in active magnetic bearing (AMB) feedback control systems. Firstly, the rotor vibration producing mechanisms of AMB were analyzed. Then, the AFB under the assumption of unknown rotational frequency and amplitude are designed. Finally the simulation results show that the AFB method proposed in this paper makes it possible to completely reject unknown sinusoidal disturbance in a closed loop control system

scholarly journals Probability distribution of decay rate: a statistical time-domain damping parameter for structural damage identification

2018 ◽  
Vol 18 (1) ◽  
pp. 66-86 ◽  
Author(s):  
Ali M Ay ◽  
Suiyang Khoo ◽  
Ying Wang
Keyword(s):  
Statistical Analysis ◽  
Probability Distribution ◽  
Free Vibration ◽  
Decay Rate ◽  
Structural Damage ◽  
Damage Identification ◽  
Scale Model ◽  
Data Set ◽  
Comparison Results ◽  
Rate Method

This article proposes a novel vibration-based damage identification method, named the probability distribution of decay rate. By introducing a statistical framework, the probability distribution of decay rate method estimates the damage-induced changes in overall damping behaviour of a free-vibration dynamic system. Utilising free-vibration impulse response data, a one-dimensional data set of local maxima–minima points is constructed. A statistical analysis of this data set is then performed to derive damage-sensitive parameters. It is demonstrated that through the use of a statistical analysis framework, a number of enhancements are attained in terms of both robustness and leniency in estimating the significantly nonlinear property of overall damping. An impact hammer test is conducted in the laboratory to verify the efficacy of the proposed probability distribution of decay rate method. The test was performed on a scale-model steel Warren-truss bridge structure, subjected to bolt-connection failures. The comparison results between the probability distribution of decay rate method and the standard experimental modal analysis method confirm that the former is effective for damage identification of complex structures, particularly with real experimental data and steel-frame structure assemblies.

scholarly journals Nonlinear Dynamic Simulation of an Active Magnetic Bearing System With Non-Symmetric Coordinate Coupling Forces

1997 ◽  
Author(s):  
Horst Ecker ◽  
Josiah D. Knight ◽  
Lan Wu
Keyword(s):  
Equations Of Motion ◽  
Strong Dependence ◽  
Path Following ◽  
Spatial Arrangement ◽  
High Amplitude ◽  
Magnetic Bearing ◽  
Active Magnetic Bearing ◽  
Domains Of Attraction ◽  
Loop Control ◽  
Steady Load

Equations of motion are presented for a two degree of freedom system representing a rotor suspended with an active magnetic bearing. The rotor is subjected to both a rotating unbalance force and a steady load, which is balanced by differential bias in the vertical magnet pair. A coupling between the coordinate directions resulting from the spatial arrangement of magnets is included in the equations of motion, which renders them nonlinear even though the closed loop control on each axis is linear. Results of a path-following analysis of the equations show that the addition of a steady load has several effects. Compared with previous results for an unloaded system, the response is now asymmetric due to unequal stiffnesses, and the region of unacceptable high amplitude response extends over a larger frequency range. In addition, the frequency ranges over which multiple stable solutions coexist is expanded. New results for the unloaded case are also presented that show domains of attraction to large amplitude stable response due to an applied impulse. There is a strong dependence of the domains of attraction on the timing of the impulse.

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