On the Control of Synchronous Vibration in Rotor/Magnetic Bearing Systems Involving Auxiliary Bearing Contact

2002 ◽  
Author(s):  
Patrick Keogh ◽  
Matthew Cole ◽  
Necip Sahinkaya ◽  
Clifford Burrows
Keyword(s):  
Controller Design ◽  
Magnetic Bearing ◽  
Contact Forces ◽  
Normal Operation ◽  
Design Parameters ◽  
Full Control ◽  
Bearing Contact ◽  
Vibratory Motion ◽  
Auxiliary Bearing ◽  
Bearing Design

During the normal operation of rotor/magnetic bearing systems, contacts with auxiliary bearings or bushes are avoided. However, auxiliary bearings are required under abnormal conditions and in malfunctions situations to prevent contact between the rotor and stator laminations. Studies in the open literature deal largely with rotor drop and the requirements of auxiliary bearing design parameters for safe run-down. Rotor drop occurs when the rotor is de-levitated and no further means of magnetic bearing control is available. This paper considers the case when full control is still available and rotor/auxiliary bearing contact has been induced by an abnormal operating condition or temporary fault. It is demonstrated that events leading to contact from a linearly stable rotor orbit can drive the rotor into a non-linear vibratory motion involving persistent contacts. Furthermore, the phase of the measured vibration response may be changed to such an extent that synchronous controllers designed to minimize rotor vibration amplitudes will worsen the rotor response, resulting in higher contact forces. A modified controller design is proposed and demonstrated to be capable of returning a rotor from a contacting to a non-contacting state.

On the Control of Synchronous Vibration in Rotor/Magnetic Bearing Systems Involving Auxiliary Bearing Contact

2004 ◽  
Vol 126 (2) ◽  
pp. 366-372 ◽  
Author(s):  
P. S. Keogh ◽  
M. O. T. Cole ◽  
M. N. Sahinkaya ◽  
C. R. Burrows
Keyword(s):  
Controller Design ◽  
Magnetic Bearing ◽  
Contact Forces ◽  
Normal Operation ◽  
Design Parameters ◽  
Rotor Vibration ◽  
Full Control ◽  
Bearing Contact ◽  
Vibratory Motion ◽  
Auxiliary Bearing

During the normal operation of rotor/magnetic bearing systems, contacts with auxiliary bearings or bushes are avoided. However, auxiliary bearings are required under abnormal conditions and in malfunction situations to prevent contact between the rotor and stator laminations. Studies in the open literature deal largely with rotor drop and the requirements of auxiliary bearings design parameters for safe rundown. Rotor drop occurs when the rotor is delevitated and no further means of magnetic bearing control is available. This paper considers the case when full control is still available and rotor/auxiliary bearing contact has been induced by an abnormal operating condition or a temporary fault. It is demonstrated that events leading to contact from a linearly stable rotor orbit can drive the rotor into a nonlinear vibratory motion involving persistent contacts. Furthermore, the phase of the measured vibration response may be changed to such an extent that synchronous controllers designed to minimize rotor vibration amplitudes will worsen the rotor response, resulting in higher contact forces. A modified controller design is proposed and demonstrated to be capable of returning a rotor from a contacting to a noncontacting state.

On the Use of Actively Controlled Auxiliary Bearings in Magnetic Bearing Systems

2008 ◽  
Author(s):  
Iain S. Cade ◽  
M. Necip Sahinkaya ◽  
Clifford R. Burrows ◽  
Patrick S. Keogh
Keyword(s):  
Controller Design ◽  
Control Strategies ◽  
Frictional Heating ◽  
Magnetic Bearing ◽  
Contact Forces ◽  
Active Magnetic Bearing ◽  
Physical Limit ◽  
Drop Tests ◽  
Auxiliary Bearing ◽  
And Control

Auxiliary bearings are used to prevent rotor/stator contact in active magnetic bearing systems. They are sacrificial components providing a physical limit on the rotor displacement. During rotor/auxiliary bearing contact significant forces normal to the contact zone may occur. Furthermore, rotor slip and rub can lead to localized frictional heating. Linear control strategies may also become ineffective or induce instability due to changes in rotordynamic characteristics during contact periods. This work considers the concept of using actively controlled auxiliary bearings in magnetic bearing systems. Auxiliary bearing controller design is focused on attenuating bearing vibration resulting from contact and reducing the contact forces. Controller optimization is based on the H∞ norm with appropriate weighting functions applied to the error and control signals. The controller is assessed using a simulated rotor/magnetic bearing system. Comparison of the performance of an actively controlled auxiliary bearing is made with that of a resiliently mounted auxiliary bearing. Rotor drop tests, repeated contact tests, and sudden rotor unbalance resulting in trapped contact modes, are considered.

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.

On the Use of Actively Controlled Auxiliary Bearings in Magnetic Bearing Systems

2008 ◽  
Vol 131 (2) ◽  
Author(s):  
Iain S. Cade ◽  
M. Necip Sahinkaya ◽  
Clifford R. Burrows ◽  
Patrick S. Keogh
Keyword(s):  
Controller Design ◽  
Control Strategies ◽  
Frictional Heating ◽  
Magnetic Bearing ◽  
Contact Forces ◽  
Active Magnetic Bearing ◽  
Physical Limit ◽  
Drop Tests ◽  
Auxiliary Bearing ◽  
And Control

Auxiliary bearings are used to prevent rotor/stator contact in active magnetic bearing systems. They are sacrificial components providing a physical limit on the rotor displacement. During rotor/auxiliary bearing contact significant forces normal to the contact zone may occur. Furthermore, rotor slip and rub can lead to localized frictional heating. Linear control strategies may also become ineffective or induce instability due to changes in rotordynamic characteristics during contact periods. This work considers the concept of using actively controlled auxiliary bearings in magnetic bearing systems. Auxiliary bearing controller design is focused on attenuating bearing vibration resulting from contact and reducing the contact forces. Controller optimization is based on the H∞ norm with appropriate weighting functions applied to the error and control signals. The controller is assessed using a simulated rotor/magnetic bearing system. Comparison of the performance of an actively controlled auxiliary bearing is made with that of a resiliently mounted auxiliary bearing. Rotor drop tests, repeated contact tests, and sudden rotor unbalance resulting in trapped contact modes are considered.

Effects of some design parameters on bifurcation behavior of a magnetically supported coaxial rotor in auxiliary bearings

2017 ◽  
Vol 34 (7) ◽  
pp. 2379-2395 ◽  
Author(s):  
Reza Ebrahimi ◽  
Mostafa Ghayour ◽  
Heshmatallah Mohammad Khanlo
Keyword(s):  
Magnetic Bearing ◽  
Active Magnetic Bearing ◽  
Design Parameters ◽  
Maximum Lyapunov Exponent ◽  
Content Type ◽  
Coaxial Rotor ◽  
Rotor Bearing ◽  
Auxiliary Bearing ◽  
Bearing Stiffness ◽  
Bifurcation Behavior

Purpose This paper aims to present bifurcation analysis of a magnetically supported coaxial rotor model in auxiliary bearings, which includes gyroscopic moments of disks and geometric coupling of the magnetic actuators. Design/methodology/approach Ten nonlinear equations of motion were solved using the Runge–Kutta method. The vibration responses were analyzed using dynamic trajectories, power spectra, Poincaré maps, bifurcation diagrams and the maximum Lyapunov exponent. The analysis was carried out for different system parameters, namely, the inner shaft stiffness, inter-rotor bearing stiffness, auxiliary bearing stiffness and disk position. Findings It was shown that dynamics of the system could be significantly affected by varying these parameters, so that the system responses displayed a rich variety of nonlinear dynamical phenomena, including quasi-periodicity, chaos and jump. Next, some threshold values were provided with regard to the design of appropriate parameters for this system. Therefore, the proposed work can provide an effective means of gaining insights into the nonlinear dynamics of coaxial rotor–active magnetic bearing systems with auxiliary bearings in the future. Originality/value This paper considered the influences of the inner shaft stiffness, inter-rotor bearing stiffness, auxiliary bearing stiffness and disk position on the bifurcation behavior of a magnetically supported coaxial rotor system in auxiliary bearings.

Dynamic Analysis for the Rotor Drop Process and Its Application to a Vertically Levitated Rotor/Active Magnetic Bearing System

2017 ◽  
Vol 139 (4) ◽  
Author(s):  
Yulan Zhao ◽  
Guojun Yang ◽  
Patrick Keogh ◽  
Lei Zhao
Keyword(s):  
High Speed ◽  
Sliding Friction ◽  
Engineering Application ◽  
Magnetic Bearing ◽  
Contact Forces ◽  
Active Magnetic Bearing ◽  
Detailed Model ◽  
Vertical Rotor ◽  
Auxiliary Bearing ◽  
Rotor Dynamic

Active magnetic bearings (AMBs) have been utilized widely to support high-speed rotors. However, in the case of AMB failure, emergencies, or overload conditions, the auxiliary bearing is chosen as the backup protector to provide mechanical supports and displacement constraints for the rotor. With lack of support, the auxiliary bearing will catch the dropping rotor. Accordingly, high contact forces and corresponding thermal generation due to mechanical rub are applied on the dynamic contact area. Rapid deterioration may be brought about by excessive dynamic and thermal shocks. Therefore, the auxiliary bearing must be sufficiently robust to guarantee the safety of the AMB system. Many approaches have been put forward in the literature to estimate the rotor dynamic motion, nonetheless most of them focus on the horizontal rotor drop and few consider the inclination around the horizontal plane for the vertical rotor. The main purpose of this paper is to predict the rotor dynamic behavior accurately for the vertical rotor drop case. A detailed model for the vertical rotor drop process with consideration of the rotating inclination around x- and y-axes is proposed in this paper. Additionally, rolling and sliding friction are distinguished in the simulation scenario. This model has been applied to estimate the rotor drop process in a helium circulator system equipped with AMBs for the 10 MW high-temperature gas-cooled reactor (HTR-10). The HTR-10 has been designed and researched by the Institute of Nuclear and New Energy Technology (INET) of Tsinghua University. The auxiliary bearing is utilized to support the rotor in the helium circulator. The validity of this model is verified by the results obtained in this paper as well. This paper also provides suggestions for the further improvement of auxiliary bearing design and engineering application.

Feedback Control to Prevent Damage by Rotor Rubbing After an Impact Load

2009 ◽  
Author(s):  
Lucas Ginzinger ◽  
Benjamin Heckmann ◽  
Heinz Ulbrich
Keyword(s):  
Control System ◽  
Feedback Control ◽  
Control Strategy ◽  
Impact Load ◽  
Operation Mode ◽  
Rotor System ◽  
Contact Forces ◽  
Normal Operation ◽  
Control Force ◽  
Auxiliary Bearing

A new approach to control a rubbing rotor by applying an active auxiliary bearing has been developed. The control force is applied indirectly using the auxiliary bearing, only in case of rotor rubbing. The auxiliary bearing is actuated using two unidirectional actuators. A three-phase control strategy has been developed which stabilizes the rotor system in case of an impact load and effectively avoids “backward whirling” which is very destructive. As soon as the load ceased the auxiliary bearing is separated from the rotor again and normal operation mode is continued. During the normal operation state, the feedback control does not interfere with the rotor system at all. A test rig has been developed to experimentally verify the control system. Various experiments show the success of the control strategy. In case of rubbing, the contact forces are reduced up to 95 percent. At the same time, the rotor deflection is decreased too. The activation and deactivation of the control system is operated fully automatically. A simulation framework for an elastic rotor including the non-smooth nonlinear dynamics of contacts is presented, which has been used to develop the feedback controller.

Efficient and Robust Rub Control With an Active Auxiliary Bearing

2007 ◽  
Author(s):  
Lucas Ginzinger ◽  
Heinz Ulbrich
Keyword(s):  
Control System ◽  
Control Strategy ◽  
High Efficiency ◽  
Industrial Applications ◽  
Rotor System ◽  
Contact Forces ◽  
Smooth Transition ◽  
Normal Operation ◽  
Control Force ◽  
Auxiliary Bearing

In this contribution, a new approach to control a rubbing rotor by applying an active auxiliary bearing is presented. The auxiliary bearing is attached to the foundation via two unidirectional actuators. The control force is applied indirectly using the auxiliary bearing, only in case of rotor rubbing. During a normal operation state, the feedback control does not interfere with the rotor system at all. A robust control system has been developed which significantly reduces the intensity of rubbing by stabilizing the rotor system and assuring an optimal rubbing state in case of a too large rotor amplitude. The two-phase control strategy guarantees a smooth transition from free rotor motion to the state of synchronous full annular rub. A test rig has been developed to experimentally verify the control system. Various experiments show the success of the control strategy. In case of rubbing, the contact forces are reduced up to 80 per cent, which results in significantly lower loads. At the same time, the rotor deflection is decreased too. For industrial applications, the activation of the control system can be operated fully automatically. The high efficiency of the control algorithm allows an implementation on microcontrollers. The developed control of the auxiliary bearing reduces the load and the noise of the system during rotor rubbing significantly.

Design of Experiments for the Controller of Rotor Systems With a Magnetic Bearing

1997 ◽  
Vol 119 (2) ◽  
pp. 200-207 ◽  
Author(s):  
G. J. Sheu ◽  
S. M. Yang ◽  
C. D. Yang
Keyword(s):  
Controller Design ◽  
Design Method ◽  
Magnetic Bearing ◽  
Control Technique ◽  
Design Parameters ◽  
Control Engineering ◽  
Rotor Systems ◽  
Experimental Design Method ◽  
Loss Index ◽  
And Performance

A new design methodology for the vibration control of rotor systems with a magnetic bearing is developed in this paper. The methodology combines the experimental design method in quality control engineering and the conventional PD control technique such that their advantages in implementation feasibility and performance-robustness can be integrated together. A quality loss index defined by the summation of the infinity norm of unbalanced vibration is used to characterize the system dynamics. By using the location of the magnetic bearing and PD feedback gains as design parameters, the controller can be determined by a small number of matrix experiments to achieve the best system performance. In addition, it is robust to the vibration modes within a desired speed range. A rotor system consisting of 4 rigid disks, 3 isotropic bearings, and 1 magnetic bearing is applied to illustrate the feasibility and effectiveness of the experiment-aided controller design.

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