Magnetic Bearing/Damper Effects on Unbalance Response of Flexible Rotors

1987 ◽  
Author(s):  
P. E. Allaire ◽  
R. R. Humphris ◽  
M. E. F. Kasarda ◽  
M. I. Koolman
Keyword(s):  
Magnetic Bearing ◽  
Unbalance Response ◽  
Flexible Rotors

Rotor vibration with auxiliary bearing contact in magnetic bearing systems Part 1: Synchronous dynamics

2003 ◽  
Vol 217 (4) ◽  
pp. 377-392 ◽  
Author(s):  
P S Keogh ◽  
M O T Cole
Keyword(s):  
Position Control ◽  
Magnetic Bearing ◽  
Physical Interaction ◽  
Flexible Rotor ◽  
Rotor Vibration ◽  
Full Control ◽  
Flexible Rotors ◽  
Bearing Contact ◽  
Auxiliary Bearing ◽  
Control Capability

Magnetic bearing systems incorporate auxiliary bearings to prevent physical interaction between rotor and stator laminations. Rotor/auxiliary bearing contacts may occur when a magnetic bearing still retains a full control capability. To actively return the rotor to a non-contacting state it is essential to determine the manner in which contact events affect the rotor vibration signals used for position control. An analytical procedure is used to assess the nature of rotor contact modes under idealized contacts. Non-linearities arising from contact and magnetic bearing forces are then included in simulation studies involving rigid and flexible rotors to predict rotor response and evaluate rotor synchronous vibration components. An experimental flexible rotor/magnetic bearing facility is also used to validate the predictions. It is shown that changes in synchronous vibration amplitude and phase induced by contact events causes existing controllers to be ineffective in attenuating rotor displacements. These findings are used in Part 2 of the paper as a foundation for the design of new controllers that are able to recover rotor position control under a range of contact cases.

Isotropic Optimal Control of Active Magnetic Bearing System

1996 ◽  
Vol 118 (4) ◽  
pp. 721-726 ◽  
Author(s):  
Cheol-Soon Kim ◽  
Chong-Won Lee
Keyword(s):  
Optimal Control ◽  
System Analysis ◽  
Control Method ◽  
Magnetic Bearing ◽  
Active Magnetic Bearing ◽  
Control Effort ◽  
Response Component ◽  
Unbalance Response ◽  
Control Scheme ◽  
Bearing System

As a new rotor control scheme, isotropic control of weakly anisotropic rotor bearing system in complex state space is proposed, which utilizes the concepts on the eigenstructure of the isotropic rotor system. Advantages of the scheme are that the controlled system always retains isotropic eigenstructure, leading to circular whirling due to unbalance and that it is efficient for control of unbalance response. And the system analysis and controller design becomes simple and yet comprehensive since the order of the matrices treated in the complex domain approach is half of that in the real approach. The control scheme is applied to a rigid rotor-active magnetic bearing system which is digitally controlled and the control performance is investigated experimentally in relation to unbalance response and control energy. It is found that the isotropic optimal control method, which essentially eliminates the backward unbalance response component, is more efficient than the conventional optimal control in that it gives smaller major whirl radius and yet it often requires less control effort.

Aseismic Vibration Control of Flexible Rotors Using Active Magnetic Bearing

2001 ◽  
Vol 124 (1) ◽  
pp. 49-57 ◽  
Author(s):  
Osami Matsushita ◽  
Toshio Imashima ◽  
Yoshitaka Hisanaga ◽  
Hiroki Okubo
Keyword(s):  
Seismic Waves ◽  
Control Method ◽  
Magnetic Bearing ◽  
Active Magnetic Bearing ◽  
Flexible Rotor ◽  
Feed Forward Control ◽  
Kobe Earthquake ◽  
Flexible Rotors ◽  
Additional Control ◽  
Modal Model

The wide application of active magnetic bearing (AMB) requires an aseismic evaluation with respect to AMB rotor vibrations caused by actual earthquakes. A flexible rotor supported by AMB is selected for this purpose. A shaking simulation obtained using the quasi-modal model and the actual Kobe earthquake was completed. A corresponding test rotor was excited by seismic waves and the resulting vibration was measured for the vibration evaluation. In order to reduce the response severity against earthquakes, we propose an additional feed forward control method which is proportional to the signal detected by the accelerometers attached to the bearing housings. Since this additional control can cancel rotor vibration generated by the earthquakes, AMB rotor vibrations are successfully suppressed at a low level.

Unbalance Response of Flexible Rotors Coupled With Torsion

1989 ◽  
Vol 111 (2) ◽  
pp. 179-186 ◽  
Author(s):  
H. Diken ◽  
I. G. Tadjbakhsh
Keyword(s):  
Shear Deformation ◽  
Equations Of Motion ◽  
Continuous System ◽  
Internal Damping ◽  
Governing Equations ◽  
Disk System ◽  
Torsional Oscillations ◽  
Unbalance Response ◽  
Flexible Rotors ◽  
Mass Eccentricity

The effect of coupling with torsion on the unbalance response of flexible rotors, supported by isotropic flexible and damped bearings is investigated. Flexural vibrations of the shaft-disk system are coupled with torsional oscillations through mass eccentricity. The governing equations of motion of the continuous system are solved numerically with a modified Myklestad-Prohl method without the necessity of considering an equivalent lumped system. The cases of constant or harmonic torque applied to the disk are considered. Gyroscopic, rotary inertia, shear deformation, external and internal damping effects are taken into account.

Optimum Bearing and Support Damping for Unbalance Response and Stability of Rotating Machinery

1978 ◽  
Vol 100 (1) ◽  
pp. 89-94 ◽  
Author(s):  
L. E. Barrett ◽  
E. J. Gunter ◽  
P. E. Allaire
Keyword(s):  
Approximate Method ◽  
Critical Speed ◽  
Exact Methods ◽  
Mass Model ◽  
Unbalance Response ◽  
Flexible Rotors ◽  
Bearing Stiffness ◽  
Single Mass ◽  
Internal Rotor ◽  
Stability Limits

This paper presents a rapid approximate method for calculating the optimum bearing or support damping for multimass flexible rotors to minimize unbalance response and to maximize stability in the vicinity of the rotor first critical speed. A multimass rotor is represented by an equivalent single-mass model for purposes of the analysis. The optimum bearing damping is expressed as a function of the bearing stiffness and rotor modal stiffness at the rigid bearing critical speed. Stability limits for aerodynamic cross coupling and viscous internal rotor friction damping are also presented. Comparison of the optimum damping obtained by this approximate method with that obtained by full scale linearized transfer matrix methods for several rotor-bearing configurations shows good agreement. The method has the advantage of being quickly and easily applied and can reduce analysis time by eliminating a time consuming search for the approximate optimum damping using more exact methods.

Operating Characteristics of Three-Lobe Bearings

1984 ◽  
Vol 106 (1) ◽  
pp. 61-69 ◽  
Author(s):  
R. D. Flack ◽  
P. E. Allaire
Keyword(s):  
Carrying Capacity ◽  
Operating Characteristic ◽  
Instability Threshold ◽  
Load Carrying Capacity ◽  
Operating Characteristics ◽  
Unbalance Response ◽  
Flexible Rotors ◽  
Load Carrying ◽  
Offset Factor ◽  
Bearing Preload

Three-lobe bearings were studied for both rigid and flexible rotors from three aspects: instability threshold, load carrying capacity, and unbalance response. Offset factor, preload factor, and load orientation were parametrically varied for the bearings and their influences on the foregoing characteristics were studied both theoretically and experimentally. Results indicate that, in general, all three operating characteristics cannot be optimized for the same bearing parameters. For example, the lowest unbalance response was found for small bearing preload factors, while the highest instability thresholds were found for large preload factors. As a result, when choosing a bearing for a particular application, the designer must consider which operating characteristic is most important and choose the bearing accordingly.

Synchronous Unbalance Response of an Overhung Rotor With Disk Skew

1979 ◽  
Author(s):  
O. J. Salamone ◽  
E. J. Gunter
Keyword(s):  
Phase Angle ◽  
Critical Speed ◽  
Rapid Phase ◽  
Single Plane ◽  
Unbalance Response ◽  
Flexible Rotors ◽  
All Speeds

This paper deals with the influence of disk skew on the synchronous unbalance of flexible rotors in damped bearings. A simple overhung rotor 1E treated to illustrate the effects of various combinations of unbalance and disk skew on the amplitude and phase angle response at the disk and bearings. The paper shows that it is impossible to balance the rotor at all speeds by single plane balancing even if three correction planes are employed. The presence of disk skew may be best detected by monitoring the far bearing for a rapid phase angle decrease after passing through the first critical speed.

Unbalance response of a magnetic suspended dual-rotor system

2019 ◽  
Vol 233 (15) ◽  
pp. 5758-5772
Author(s):  
Dongxiong Wang ◽  
Nianxian Wang ◽  
Kuisheng Chen
Keyword(s):  
Magnetic Bearing ◽  
Rotor System ◽  
Magnetic Bearings ◽  
Active Magnetic Bearing ◽  
Active Magnetic Bearings ◽  
Maximum Displacement ◽  
Critical Speeds ◽  
Unbalance Response ◽  
Rotor Imbalance ◽  
Aero Engine

The magnetic suspended dual-rotor system applied in more electric aero-engine can eliminate the wear and lubrication system of mechanical bearings and solve the vibration control issue of system effectively, which provides the possibility to improve the performance of aero-engine significantly. This research focuses on the unbalance response of the magnetic suspended dual-rotor system. First, a structure of dual-rotor system supported by two active magnetic bearings and two permanent magnetic bearings is presented. With proportional derivative (PD) control adopted, the bearing characteristics of active magnetic bearings are modeled as the equivalent stiffness and equivalent damping, and the permanent magnetic bearings are modeled as elastic support. Then, the Riccati transfer matrix method with good numerical stability is used to establish the model of the magnetic suspended dual-rotor system unbalance response. Subsequently, the validity of the present formulation has been tested against some known results available in literature and the simulation results obtained by finite element method (FEM). Finally, the dynamic characteristics of the unbalance response are investigated. The results reveal that the influence of the inner rotor imbalance excitation on the magnetic suspended dual-rotor system unbalance response is much larger than that of the outer rotor imbalance excitation. In addition, the critical speeds increase with the proportional coefficient, and the derivative coefficient can affect the amplitudes of the unbalance response, but not critical speeds. From the perspectives of the maximum bearing capacity and maximum displacement of active magnetic bearing-rotor system, the possibility of the magnetic suspended dual-rotor system safely crossing the critical speeds of the first three orders is investigated.

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