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.

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.

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.

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.

scholarly journals Drop analysis of Active Magnetic Bearing with rolling-sliding integrated auxiliary bearing

2021 ◽  
Vol 2048 (1) ◽  
pp. 012019
Author(s):  
Mingqi Wang ◽  
Xingnan Liu ◽  
Yulan Zhao ◽  
Guojun Yang ◽  
Jianqiang Chen ◽  
...  
Keyword(s):  
Analytical Model ◽  
Nuclear Power ◽  
Structural Characteristics ◽  
Complex Structure ◽  
Tangential Force ◽  
Rolling Bearing ◽  
Magnetic Bearing ◽  
Contact Forces ◽  
Active Magnetic Bearing ◽  
Auxiliary Bearing

Abstract The Active Magnetic Bearing (AMB) technology is introduced in the High Temperature Reactor-Pebble-bed Modules (HTR-PM) demonstration nuclear power plant, which is being constructed in Shandong province, China. The auxiliary bearing is one of the most important components guaranteeing the reliability of the AMB. It also has an important impact on the reliability of the whole reactor system. Compared with the traditional auxiliary bearing, a novel one proposed by the authors has a smaller impact force and the rotor center orbit is much more concentrated during the rotor drop. This paper establishes an analytical model of drop of rolling-sliding integrated auxiliary bearing to analyze the above phenomena. Based on the Hertz contact theory, the complex structure inside the rolling bearing is simplified through a spring damping model. The overall impact model of the rolling-sliding integrated auxiliary bearing is established. Then, according to the structural characteristics of the rolling-sliding integrated auxiliary bearing, the tangential force inside the rolling- sliding integrated auxiliary bearing can be obtained by applying the angular momentum theorem. Finally, a four-degree-of-freedom horizontal rotor drop model is established to analyze and calculate the center orbit and motion state of the rotor. The analytical model is helpful in the selection and design of auxiliary bearing for AMB. In further research this contact model can be used to calculate the center orbit and contact forces in the application of the rolling-sliding integrated auxiliary bearing.

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.

Wavelet Coefficient Characteristics During Rotor/Auxiliary Bearing Contact in Active Magnetic Bearing Systems

2007 ◽  
Author(s):  
Iain S. Cade ◽  
Patrick S. Keogh ◽  
M. Necip Sahinkaya ◽  
Clifford R. Burrows
Keyword(s):  
Control Strategies ◽  
Wavelet Coefficient ◽  
Radial Component ◽  
Magnetic Bearing ◽  
Active Magnetic Bearing ◽  
Wavelet Coefficients ◽  
Time Frequency ◽  
Bearing Contact ◽  
Rotor Bearing ◽  
Auxiliary Bearing

Auxiliary bearings are present in active magnetic bearing systems to prevent rotor/stator contact. If rotor/bearing contact occurs, significant impact forces may arise. Furthermore, linear control strategies may become ineffective due to the non-linear dynamics introduced by the auxiliary bearing. Rotor/auxiliary bearing contact is therefore an important consideration for the continued safe operation of an active magnetic bearing system. This work utilizes the localized nature of wavelets coefficients in characterising rotor/bearing contact responses. An experimental approach is adopted using a flexible rotor/active magnetic bearing test rig. Different disturbances resulting in periodic rotor contact and rotor/bearing rub were applied using a single active magnetic bearing. Rotor displacements were measured and the radial component and associated wavelet coefficients identified from off-line data processing. Variations of the wavelet coefficients characteristics corresponding to the periodic contact and rotor/bearing rub are assessed. The choice of mother wavelet is seen to have only a small effect on wavelet coefficient values. Wavelet analysis is shown as a feasible method for identifying time-frequency characteristics of rotor/bearing contact.

Commissioning and Control of the AMB Supported 3.5 kW Laboratory Gas Blower Prototype

2013 ◽  
Vol 198 ◽  
pp. 451-456 ◽  
Author(s):  
Rafał P. Jastrzębski ◽  
Alexander Smirnov ◽  
Katja Hynynen ◽  
Janne Nerg ◽  
Jussi Sopanen ◽  
...  
Keyword(s):  
Control System ◽  
Permanent Magnet ◽  
Induction Motor ◽  
Industrial Applications ◽  
Magnetic Bearing ◽  
Active Magnetic Bearing ◽  
Sensor Calibration ◽  
Full Potential ◽  
Disturbance Analysis ◽  
And Control

This paper presents the practical results of the design analysis, commissioning, identification, sensor calibration, and tuning of an active magnetic bearing (AMB) control system for a laboratory gas blower. The presented step-by-step procedures, including modeling and disturbance analysis for different design choices, are necessary to reach the full potential of the prototype in research and industrial applications. The key results include estimation of radial and axial disturbance forces caused by the permanent magnet (PM) rotor and a discussion on differences between the unbalance forces resulting from the PM motor and the induction motor in the AMB rotor system.

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.

scholarly journals Development and Experimental Validation of Auxiliary Rolling Bearing Models for Active Magnetic Bearings (AMBs) Applications

2019 ◽  
Vol 2019 ◽  
pp. 1-19 ◽  
Author(s):  
Anna Tangredi ◽  
Enrico Meli ◽  
Andrea Rindi ◽  
Alessandro Ridolfi ◽  
Pierluca D’Adamio ◽  
...  
Keyword(s):  
Load Capacity ◽  
Critical Phenomenon ◽  
Magnetic Bearing ◽  
Design Tool ◽  
Magnetic Bearings ◽  
Active Magnetic Bearing ◽  
Active Magnetic Bearings ◽  
Short Period ◽  
Auxiliary Bearing ◽  
Bearing System

Nowadays, the search for increasing performances in turbomachinery applications has led to a growing utilization of active magnetic bearings (AMBs), which can bring a series of advantages thanks to their features: AMBs allow the machine components to reach higher peripheral speeds; in fact there are no wear and lubrication problems as the contact between bearing surfaces is absent. Furthermore, AMBs characteristic parameters can be controlled via software, optimizing machine dynamics performances. However, active magnetic bearings present some peculiarities, as they have lower load capacity than the most commonly used rolling and hydrodynamic bearings, and they need an energy source; for these reasons, in case of AMBs overload or breakdown, an auxiliary bearing system is required to support the rotor during such landing events. During the turbomachine design process, it is fundamental to appropriately choose the auxiliary bearing type and characteristics, because such components have to resist to the rotor impact; so, a supporting design tool based on accurate and efficient models of auxiliary bearings is very useful for the design integration of the Active Magnetic Bearing System into the machine. This paper presents an innovative model to accurately describe the mechanical behavior of a complete rotor-dynamic system composed of a rotor equipped with two auxiliary rolling bearings. The model, developed and experimentally validated in collaboration with Baker Hughes a GE company (providing the test case and the experimental data), is able to reproduce the key physical phenomena experimentally observed; in particular, the most critical phenomenon noted during repeated experimental combined landing tests is the rotor forward whirl, which occurs in case of high friction conditions and greatly influences the whole system behavior. In order to carefully study some special phenomena like rotor coast down on landing bearings (which requires long period of time to evolve and involves many bodies and degrees of freedom) or other particular events like impacts (which occur in a short period of time), a compromise between accuracy of the results and numerical efficiency has been pursued. Some of the elements of the proposed model have been previously introduced in literature; however the present work proposes some new features of interest. For example, the lateral and the axial models have been properly coupled in order to correctly reproduce the effects observed during the experimental tests and a very important system element, the landing bearing compliant suspension, has been properly modelled to more accurately describe its elastic and damping effects on the system. Furthermore, the model is also useful to characterize the frequencies related to the rotor forward whirl motion.

Design and Analysis of a Multimodal Grasper Having Shape Conformity and Within-Hand Manipulation With Adjustable Contact Forces

2019 ◽  
Vol 11 (5) ◽  
Author(s):  
Nagamanikandan Govindan ◽  
Asokan Thondiyath
Keyword(s):  
Control Strategies ◽  
Low Cost ◽  
Active Surface ◽  
Force Sensor ◽  
Contact Forces ◽  
Geometrical Shape ◽  
Planning And Control ◽  
Control Scheme ◽  
And Control ◽  
Compact Mechanism

Abstract This paper presents the design, analysis, and testing of a novel multimodal grasper having the capabilities of shape conformation, within-hand manipulation, and a built-in compact mechanism to vary the forces at the contact surface. The proposed grasper has two important qualities: versatility and less complexity. The former refers to the ability to grasp a range of objects having different geometrical shape, size, and payload and perform in-hand manipulations such as rolling and sliding, and the latter refers to the uncomplicated design, and ease of planning and control strategies. Increasing the number of functions performed by the grasper to adapt to a variety of tasks in structured and unstructured environments without increasing the mechanical complexity is the main interest of this research. The proposed grasper consists of two hybrid jaws having a rigid inner structure encompassed by a flexible, active gripping surface. The flexibility of the active surface has been exploited to achieve shape conformation, and the same has been utilized with a compact mechanism, introduced in the jaws, to vary the contact forces while grasping and manipulating an object. Simple and scalable structure, compactness, low cost, and simple control scheme are the main features of the proposed design. Detailed kinematic and static analysis are presented to show the capability of the grasper to adjust and estimate the contact forces without using a force sensor. Experiments are conducted on the fabricated prototype to validate the different modes of operation and to evaluate the advantages of the proposed concept.

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