Multi-State Transient Rotor Vibration Control Using Sampled Harmonics

2002 ◽  
Vol 124 (2) ◽  
pp. 186-197 ◽  
Author(s):  
P. S. Keogh ◽  
M. O. T. Cole ◽  
C. R. Burrows
Keyword(s):  
Magnetic Bearing ◽  
Measured Data ◽  
Rapid Decrease ◽  
Flexible Rotor ◽  
Rotor Vibration ◽  
Transient Vibration ◽  
Stability Boundaries ◽  
Vibration Attenuation ◽  
Harmonic Components ◽  
Bearing System

A technique is introduced to achieve transient vibration attenuation in a multi-input, multi-output flexible rotor/magnetic bearing system. The strategy employs feedback control of measured harmonic components of rotor vibration. Whereas previous harmonic controllers have been based only on steady state vibration characteristics, the new controller also incorporates the transient dynamics. The controller may still be designed from measured data and is determined from target transient vibrational responses arising from step changes in particular disturbances. Account is taken of delays arising from evaluation of harmonic components. Furthermore, stability boundaries for the controller are shown to have significant tolerance to measurement error. The controller is validated experimentally in a flexible rotor/magnetic bearing system and mass loss tests are used to demonstrate rapid decrease in vibration levels with near elimination of transient overshoot.

Optimized Design of Vibration Controllers for Steady and Transient Excitation of Flexible Rotors

1995 ◽  
Vol 209 (3) ◽  
pp. 155-168 ◽  
Author(s):  
P S Keogh ◽  
C Mu ◽  
C R Burrows
Keyword(s):  
Measurement Error ◽  
Controller Design ◽  
Optimized Design ◽  
Rotor Vibration ◽  
Transient Vibration ◽  
Flexible Rotors ◽  
Vibration Attenuation ◽  
Measured Displacement ◽  
Control Forces ◽  
Shaft Surface

Controller designs for the attenuation of rotor vibration are investigated. Disturbance inputs leading to vibration are classified and related to control forces and defined control states. Optimization based on the H∞ norm is then used to minimize the influence of forcing disturbances, modelling error and measurement error. The practicalities of applying the method to an experimental rotor-bearing system, with hardware constraints on controller order, are stated. The controller was implemented experimentally to conduct steady state and mass loss tests. Steady synchronous, non-synchronous and transient vibration attenuation was demonstrated. It was also shown that measurement error, caused by shaft surface roughness, can be incorporated into the controller design without the need to remove the roughness component from the measured displacement signals. If the roughness influence is not included in the design and the uncontrolled vibration is small, unnecessary control forces may result, causing an increase in vibration.

Robust Control for Flexible Rotor of Magnetic Bearing System

2018 ◽  
Vol 2018.67 (0) ◽  
pp. 111
Author(s):  
Takemitsu TAKAGI ◽  
Chen GAN ◽  
isao TAKAMI
Keyword(s):  
Robust Control ◽  
Magnetic Bearing ◽  
Flexible Rotor ◽  
Bearing System

The Control and Dynamical Analysis on Magnetic Bearing Flexible Rotor System Combining the Whirling with Swing

2011 ◽  
Vol 189-193 ◽  
pp. 1592-1596
Author(s):  
Hui Qun Yuan ◽  
Ying Li ◽  
Dong Li ◽  
Wen Bo Wu
Keyword(s):  
Rotation Axis ◽  
Magnetic Bearing ◽  
Dynamical Analysis ◽  
Rotational Axis ◽  
Flexible Rotor ◽  
Precision Control ◽  
And Control ◽  
Bearing Rigidity ◽  
Bearing System ◽  
Control Quantity

Considering gyroscopic effect and flexibility of the shaft, the eight freedoms dynamic model is established. The dynamic characteristic and control quantity in different bearing rigidity and rotation axis are studied and discussed by optimal control theory. Furthermore, the controlling and the responding are discussed. The simulation results show that the bearing rigidity has great effect on the control quantity so that the elasticity of bearing must be considered. The asymmetry rigidity of rotational axis has little influence on stability. The conclusion may bring up theoretical references for precision control for rotor magnetic bearing system.

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.

Simple Model for a Magnetic Bearing System Operating on the Auxiliary Bearing

2005 ◽  
Author(s):  
E. N. Cuesta ◽  
N. I. Montbrun ◽  
V. Rastelli ◽  
S. E. Diaz
Keyword(s):  
Systems Analysis ◽  
Magnetic Bearing ◽  
Flexible Rotor ◽  
Periodic Motions ◽  
Test Rig ◽  
Magnetic Actuator ◽  
Auxiliary Bearing ◽  
Non Linear Systems ◽  
System Operating ◽  
Bearing System

The present work studies the behavior of a magnetic bearing supported rotor when the flow of electric current to the magnetic actuator is suppressed In this condition the rotor is supported by the auxiliary bearing, which has looseness with the rotor, generating a series of impacts between these components. For the study of this state, a model of a flexible rotor is proposed, and the impacts are simulated using kinematical restitution coefficient theory. The results obtained from the theoretical model are compared with experimental data taken on a test rig using tools for non linear systems analysis such bifurcation diagrams. The comparison shows that, besides the simplification of the contact, the model predicts ranges chaotic, quasi-periodic, and periodic motions in the test rig.

Vibration control of a flexible rotor/magnetic bearing system subject to direct forcing and base motion disturbances

1998 ◽  
Vol 212 (7) ◽  
pp. 535-546 ◽  
Author(s):  
M O T Cole ◽  
P S Keogh ◽  
C R Burrows
Keyword(s):  
Gas Turbines ◽  
Controller Design ◽  
Magnetic Bearing ◽  
Pid Controllers ◽  
Control Force ◽  
Flexible Rotor ◽  
Current State ◽  
Direct Forcing ◽  
State Of Research ◽  
Bearing System

During operation, a rotor/magnetic bearing system may be subject to various sources of vibration, either directly applied to the rotor or transmitted through the bearings owing to base motion. This paper considers controller designs that are capable of attenuating vibration arising from either source. It advances the current state of research in the area since other controller designs have considered only the direct forcing case. If base motion is not considered in the design of the controller then this disturbance may cause the bearing clearance limits to be reached. Controller design is formulated as an H∞ optimization problem, with mixed design objectives. A new controller is derived that can simultaneously reduce vibration and minimize the effect of base motion on relative rotor to bearing displacement. Account is taken of the fact that the bearings can apply only limited control force. The design study was complemented by a programme of experimental work. The base of a rig was subjected to impulse inputs and the results show the effectiveness of the new controller design. It is demonstrated that proportional, integral and derivative (PID) controllers, or controllers designed for unbalance vibration attenuation only, may result in rotor contact with retainer bushes, while the new controller may prevent contact. The potential now exists for continuing safe operation of flexible rotor/magnetic bearing systems such as compressors, gas turbines, generators, etc., in transport applications, during seismic events or in environments with expected base input disturbances.

Fault Tolerant Magnetic Bearings

1999 ◽  
Vol 121 (3) ◽  
pp. 504-508 ◽  
Author(s):  
E. H. Maslen ◽  
C. K. Sortore ◽  
G. T. Gillies ◽  
R. D. Williams ◽  
S. J. Fedigan ◽  
...  
Keyword(s):  
Fault Tolerance ◽  
High Speed ◽  
Fault Tolerant ◽  
High Capacity ◽  
Magnetic Bearing ◽  
Magnetic Bearings ◽  
Flexible Rotor ◽  
Variable Reluctance ◽  
Modular Redundancy ◽  
Bearing System

A fault tolerant magnetic bearing system was developed and demonstrated on a large flexible-rotor test rig. The bearing system comprises a high speed, fault tolerant digital controller, three high capacity radial magnetic bearings, one thrust bearing, conventional variable reluctance position sensors, and an array of commercial switching amplifiers. Controller fault tolerance is achieved through a very high speed voting mechanism which implements triple modular redundancy with a powered spare CPU, thereby permitting failure of up to three CPU modules without system failure. Amplifier/cabling/coil fault tolerance is achieved by using a separate power amplifier for each bearing coil and permitting amplifier reconfiguration by the controller upon detection of faults. This allows hot replacement of failed amplifiers without any system degradation and without providing any excess amplifier kVA capacity over the nominal system requirement. Implemented on a large (2440 mm in length) flexible rotor, the system shows excellent rejection of faults including the failure of three CPUs as well as failure of two adjacent amplifiers (or cabling) controlling an entire stator quadrant.

scholarly journals The development of a flexible rotor active magnetic bearing system

2007 ◽  
Vol 98 (1) ◽  
pp. 8-12
Author(s):  
E.O. Ranft ◽  
G. van Schoor ◽  
J.G. Roberts
Keyword(s):  
Magnetic Bearing ◽  
Active Magnetic Bearing ◽  
Flexible Rotor ◽  
Bearing System
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