Model Identification of a Rotor With Magnetic Bearings

2001 ◽  
Author(s):  
José A. Vázquez ◽  
Eric H. Maslen ◽  
Hyeong-Joon Ahn ◽  
Dong-Chul Han
Keyword(s):  
Dynamic Stiffness ◽  
Model Identification ◽  
Magnetic Bearing ◽  
Measured Data ◽  
Response Functions ◽  
Flexible Rotor ◽  
Experimental Identification ◽  
Rotor Model ◽  
Reconciliation Process ◽  
Piano Wire

The experimental identification of a long flexible rotor with three magnetic bearing journals is presented. Frequency response functions (FRFs) are measured between the magnetic bearing journals and the sensor locations while the rotor is suspended horizontally with piano wire. These FRFs are compared with the responses of a rotor model and a reconciliation process is used to reduce the discrepancies between the model and the measured data. In this identification, the wire and the fit of the magnetic bearing journals are identified as the sources of model error. As a result of the reconciliation process, equivalent dynamic stiffness are calculated for the piano wire and the fit of the magnetic bearing journals. Several significant numeral issues that were encountered during the process are discussed and solutions to some of these problems are presented.

Model Identification of a Rotor With Magnetic Bearings

2002 ◽  
Vol 125 (1) ◽  
pp. 149-155 ◽  
Author(s):  
J. A. Va´zquez ◽  
E. H. Maslen ◽  
H.-J. Ahn ◽  
D.-C. Han
Keyword(s):  
Frequency Response ◽  
Dynamic Stiffness ◽  
Model Identification ◽  
Magnetic Bearing ◽  
Response Functions ◽  
Flexible Rotor ◽  
Frequency Response Functions ◽  
Rotor Model ◽  
Reconciliation Process ◽  
Piano Wire

The experimental identification of a long flexible rotor with three magnetic bearing journals is presented. Frequency response functions are measured between the magnetic bearing journals and the sensor locations while the rotor is suspended horizontally with piano wire. These frequency response functions are compared with the responses of a rotor model and a reconciliation process is used to reduce the discrepancies between the model and the measured data. In this identification, the wire and the fit of the magnetic bearing journals are identified as the sources of model error. As a result of the reconciliation process, equivalent dynamic stiffness are calculated for the piano wire and the fit of the magnetic bearing journals. Several significant numeral issues that were encountered during the process are discussed and solutions to some of these problems are presented.

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.

Experimental Identification of Linearized Oil Film Coefficients of Cylindrical and Tilting Pad Bearings

1995 ◽  
Vol 117 (3) ◽  
pp. 593-599 ◽  
Author(s):  
P. Arumugam ◽  
S. Swarnamani ◽  
B. S. Prabhu
Keyword(s):  
Journal Bearings ◽  
Response Functions ◽  
Flexible Rotor ◽  
The Finite Element Method ◽  
Theoretical Simulation ◽  
Oil Film ◽  
Damping Coefficients ◽  
Experimental Identification ◽  
Tilting Pad ◽  
Stiffness And Damping

The dynamic behavior of the rotating machinery supported by the hydrodynamic journal bearings is significantly influenced by the dynamic characteristics of the oil film. In the present work an efficient identification method is used to identify the stiffness and damping coefficients of the tilting pad and cylindrical journal bearings of a flexible rotor-bearing system. The method uses FRFs (Frequency Response Functions) obtained by the measurements and the finite element method. The accuracy and feasibility of the method were tested and demonstrated by theoretical simulation. The possible effects of oil-film inertia is also verified by the theoretical simulation. The method can be further extended to identify twelve linearized oil-film coefficients.

Rotordynamic Response and Identification of AMB Machining Spindle

2007 ◽  
Author(s):  
Jerzy T. Sawicki ◽  
Eric H. Maslen
Keyword(s):  
High Speed ◽  
Element Model ◽  
Calibration Procedure ◽  
Magnetic Bearing ◽  
Modal Identification ◽  
High Speed Machining ◽  
Response Functions ◽  
Active Magnetic Bearings ◽  
Rotor Model ◽  
Machining Spindle

Active magnetic bearings (AMBs) are a very promising technology for machining applications. They offer a number of advantages compared to classical bearings, such as high speed capability, rotation accuracy, high stiffness, and possibility of active displacement tracking. This paper presents a modeling approach for a high-speed machining spindle-AMBs system based on finite-element model analysis coupled to experimental modal identification. The extracted frequency response functions, measured between the magnetic bearing journals and the sensor locations, are compared with the responses of a rotor model, and a calibration procedure is applied to reduce the discrepancies between the model and the measured data.

Identification of Flexible Rotor Suspended by Magnetic Bearings

2013 ◽  
Author(s):  
Zhe Sun ◽  
Jingjing Zhao ◽  
Zhengang Shi ◽  
Suyuan Yu
Keyword(s):  
Experimental System ◽  
Magnetic Bearing ◽  
Magnetic Bearings ◽  
Flexible Rotor ◽  
Role Identification ◽  
Bearing Stiffness ◽  
The Mathematical Model ◽  
Rotor Model ◽  
Bearing System ◽  
High Temperature Gas

Magnetic bearings are widely applied in High Temperature Gas-cooled Reactor (HTGR), where the rotating machineries are running under high purely helium environment. In designing and adjusting a magnetic bearing system, the mathematical model of the rotor plays an important role. Identification is a useful method to obtain the model of a rotor. However, there are some practical difficulties of identifying a magnetic bearing-rotor system without force sensors. This paper proposes an identification method for flexible rotor suspended by magnetic bearings. In this method, two experiments under different bearing stiffness are performed, the models obtained by these two experiments are then transformed to the desired rotor model and the influence of bearing stiffness is eliminated in this transformation. The proposed method is validated on an experimental system with a five degree-of-freedom suspended flexible rotor.

scholarly journals Experimental Identification of Linearized Oil Film Coefficients of Cylindrical and Tilting Pad Bearings

1994 ◽  
Author(s):  
P. Arumugam ◽  
S. Swarnamani ◽  
B. S. Prabhu
Keyword(s):  
Journal Bearings ◽  
Response Functions ◽  
Flexible Rotor ◽  
The Finite Element Method ◽  
Theoretical Simulation ◽  
Oil Film ◽  
Damping Coefficients ◽  
Experimental Identification ◽  
Tilting Pad ◽  
Stiffness And Damping

The dynamic behavior of the rotating machinery supported by the hydrodynamic journal bearings is significantly influenced by the dynamic characteristics of the oil-film. In the present work an efficient identification method is used to identify the stiffness and damping coefficients of the tilting pad and cylindrical journal bearings of flexible rotor-bearing system. The method uses FRFs (Frequency Response Functions) obtained by the measurements and the finite element method. The accuracy and feasibility of the method were tested and demonstrated by theoretical simulation. The possible effects of oil-film inertia is also verified by the theoretical simulation. The method can be further extended to identify twelve linearized oil-film coefficients.

Dynamic Analysis of Flexible Rotor Suspended by Active Magnetic Bearings With LQR Controller

2018 ◽  
Author(s):  
Yixin Su ◽  
Yanhui Ma ◽  
Qian Shi ◽  
Suyuan Yu
Keyword(s):  
Dynamic Characteristics ◽  
Beam Theory ◽  
Magnetic Bearing ◽  
Active Magnetic Bearing ◽  
Flexible Rotor ◽  
Linear Quadratic ◽  
State Response ◽  
Lagrange’S Equation ◽  
Linear Quadratic Regulation ◽  
Lqr Controller

Dynamic characteristics of active magnetic bearing (AMB)-flexible rotor system are closely related to control law. To analyze dynamic characteristics of flexible rotor suspended by AMBs with linear quadratic regulation (LQR) controller, a simple and effective method based on numerical calculation of unbalanced response is proposed in this article. The model of flexible rotor is established based upon Euler-Bernoulli beam theory and Lagrange’s equation. Disc on the rotor and its Gyro effect are taken into account. LQR controller based on error and its derivative is developed to control electromagnetic force of AMB at each degree of freedom (DOF) in real time. Under the unbalanced exciting force, the steady-state response and transient response in time domain of each node of flexible rotor at 0–4000 rad/s are calculated numerically. The critical speeds of rotor are obtained by identification method quickly and easily.

scholarly journals The Active Magnetic Bearing Enables Optimum Damping of Flexible Rotor

1984 ◽  
Author(s):  
Helmut Habermann ◽  
Maurice Brunet
Keyword(s):  
Control System ◽  
Rotation Axis ◽  
Magnetic Bearing ◽  
Active Magnetic Bearing ◽  
Flexible Rotor ◽  
Mechanical Contact ◽  
Electronic Control System ◽  
Electromagnetic Coils ◽  
Automatic Balancing ◽  
Ferromagnetic Ring

The active magnetic bearing is based on the use of forces created by a magnetic field to levitate the rotor without mechanical contact between the stationary and moving parts. A ferromagnetic ring fixed on the rotor “floats” in the magnetic fields generated by the electromagnets, which are mounted as two sets of opposing pairs. The current is transmitted to the electromagnetic coils through amplifiers. The four electromagnets control the rotor’s position in response to the signals transmitted from the sensors. The rotor is maintained in equilibrium under the control of the electromagnetic forces. Its position is determined by means of sensors which continuously monitor any displacements through an electronic control system. As in every control system, damping of the loop is provided by means of a phase advance command from one or more differenciating circuits of the position error signal. The capability of modifying the electromagnetic force both in terms of amplitude and phase leads to the benefit of specific properties for the application, in particular: - automatic balancing characterized by the rotation of the moving part around its main axis of inertia, and not around the axis of the bearings allowing operation without vibrations, - adjustable damping of the suspension allowing easy passing of the critical speeds of the rotor, - high and adjustable stiffness yielding maximum accuracy of rotor equilibrium position, - permanent diagnosis of machine operation due to the knowledge of all rotation characteristics (speed, loads on the bearings, position of the rotation axis, eccentricity, out-of-balance, disturbance frequency).

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