Contact Dynamic Response With Misalignment in a Flexible Rotor/Magnetic Bearing System

2004 ◽  
Vol 128 (2) ◽  
pp. 362-369 ◽  
Author(s):  
P. S. Keogh ◽  
M. O. T. Cole
Keyword(s):  
Dynamic Behavior ◽  
Experimental System ◽  
Magnetic Bearing ◽  
Contact Dynamics ◽  
Radial Clearance ◽  
Flexural Mode ◽  
Auxiliary Bearing ◽  
Run Up ◽  
Control Forces ◽  
Bearing System

This paper investigates the vibration characteristics of rotor displacement signals in a magnetic bearing system under conditions when rotor contact with auxiliary bearings is possible. Since these signals may be used for feedback control, it is necessary to determine how they may affect the ability of the controller to regain rotor levitation. An experimental system is used to demonstrate the sensitivity of the rotor nonlinear dynamic behavior to unbalance, which is sufficient to cause contact during rotor run-up through rigid-body and flexural mode critical speeds. Complex rotor dynamics may involve contact with more than one auxiliary bearing or bush. Application of appropriate rotating forces to the rotor through a magnetic bearing is also shown to induce similar contact dynamics. Thus, an alternative procedure for assessing the nonlinear rotor dynamic behavior is established with the potential for identification of appropriate control forces. The contact dynamics are also considered in the presence of auxiliary bearing misalignment. Misalignment may arise through physical translation of a housing or through steady-state offset errors in sensor measurements. A misalignment of 50% of the nominal radial clearance is applied at an auxiliary bearing. Various contact modes are evident as the rotor is run up in speed. During rundown, different contact dynamics may be encountered and the level of such hysteresis is assessed.

Contact Dynamic Response With Misalignment in a Flexible Rotor/Magnetic Bearing System

2004 ◽  
Author(s):  
Patrick S. Keogh ◽  
Matthew O. T. Cole
Keyword(s):  
Dynamic Behavior ◽  
Experimental System ◽  
Magnetic Bearing ◽  
Contact Dynamics ◽  
Radial Clearance ◽  
Flexural Mode ◽  
Non Linear ◽  
Auxiliary Bearing ◽  
Run Up ◽  
Bearing System

This paper investigates the vibration characteristics of rotor displacement signals in a magnetic bearing system under conditions when rotor contact with auxiliary bearings is possible. Since these signals may be used for feedback control, it is necessary to determine how they may affect the ability of the controller to regain rotor levitation. An experimental system is used to demonstrate the sensitivity of the rotor non-linear dynamic behavior to unbalance, which is sufficient to cause contact during rotor run up through rigid body and flexural mode critical speeds. Complex rotor dynamics may involve contact with more than one auxiliary bearing or bush. Application of appropriate rotating forces to the rotor through a magnetic bearing is also shown to induce similar contact dynamics. Thus an alternative procedure for assessing the non-linear rotor dynamic behavior is established with the potential for identification of appropriate control forces. The contact dynamics are also considered in the presence of auxiliary bearing misalignment. Misalignment may arise through physical translation of a housing or through steady state offset errors in sensor measurements. A misalignment of 50% of the nominal radial clearance is applied at an auxiliary bearing. Various contact modes are evident as the rotor is run up in speed. During run down different contact dynamics may be encountered and the level of such hysteresis is assessed.

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.

Traction Characteristics of a Rolling Element Bearing Under Rapid Acceleration and Implications for Auxiliary Operation in Magnetic Bearing Systems

2006 ◽  
Author(s):  
Matthew O. T. Cole ◽  
Theeraphong Wongratanaphisan
Keyword(s):  
Dynamic Behavior ◽  
Magnetic Bearing ◽  
Rolling Element Bearing ◽  
Elastic Behavior ◽  
Friction Forces ◽  
Auxiliary Operation ◽  
Rolling Element ◽  
Rolling Elements ◽  
Auxiliary Bearing ◽  
Bearing Assembly

The application of rolling element bearings for auxiliary operation in magnetic bearing systems is quite common, yet such operation is very different to that for which standard bearings are designed. During initial touchdown of a spinning rotor with an auxiliary bearing, rapid acceleration of the bearing inner race results in large inertial and friction forces acting on the rolling elements. Complex dynamic behavior of the bearing assembly and resulting traction forces are difficult to predict but, nonetheless, have important implications for both rotor dynamic behavior and thermo-elastic behavior of the bearing components. The aim of this work is to obtain an insight into bearing behavior by analyzing component interaction forces that would arise based on the assumption that the overall bearing traction torque is dependent only on instantaneous load, speed and acceleration. How such an analysis can be verified by experimental measurements of traction during rapid acceleration is discussed and some initial experimental results are presented. The implications for modeling and prediction of rotor-magnetic bearing system behavior during touchdown are also discussed.

Destabilization of Forward Rub in Rotor Magnetic Bearing Systems Using Actively Controlled Auxiliary Bearings

2010 ◽  
Author(s):  
Iain S. Cade ◽  
M. Necip Sahinkaya ◽  
Clifford R. Burrows ◽  
Patrick S. Keogh
Keyword(s):  
Design Feature ◽  
Magnetic Bearing ◽  
Open Loop ◽  
Active Magnetic Bearing ◽  
Loop Control ◽  
Bending Mode ◽  
Operating Limits ◽  
Auxiliary Bearing ◽  
Contact Free ◽  
Bearing System

During fault conditions, rotor displacements in magnetic bearing systems may potentially exceed safety/operating limits. Hence it is a common design feature to incorporate auxiliary bearings adjacent to the magnetic bearings for the prevention of rotor/stator contact. During fault conditions the rotor may come into contact with the auxiliary bearings, which may lead to continuous rub type orbit responses. In particular, forward rub responses may become persistent. This paper advances the methodology by considering an actively controlled auxiliary bearing system. An open-loop control strategy is adopted to provide auxiliary bearing displacements that destabilize established forward rub orbit responses. A theoretical approach is undertaken to identify auxiliary bearing motion limits at which forward rub responses become unstable. Experimental validation is then undertaken using a rotor/active magnetic bearing system with an actively controlled auxiliary bearing system under piezoelectric actuation. Two different operating speeds below the first bending mode of the rotor are considered and the applied harmonic displacements of the auxiliary bearing are shown to be effective in restoring contact free levitation.

Study on Bifurcation of Rigid Rotor Roller Bearings System Considering Nonlinear Dynamic Behavior

2010 ◽  
Vol 34-35 ◽  
pp. 467-471
Author(s):  
Li Cui ◽  
Jian Rong Zheng
Keyword(s):  
Dynamic Behavior ◽  
Nonlinear Dynamic ◽  
Roller Bearing ◽  
Radial Clearance ◽  
Rigid Rotor ◽  
Rotating Speed ◽  
Rotor Bearing ◽  
Nonlinear Dynamic Behavior ◽  
Bifurcation And Stability ◽  
Bearing System

Rigid rotor roller bearing system displays complicated nonlinear dynamic behavior due to nonlinear Hertzian force of bearing. Nonlinear bearing forces of roller bearing and dynamic equations of rotor bearing system are established. The bifurcation and stability of the periodic motion of the system in radial clearance-rotating speed and ellipticity-rotating speed parametric domains are studied by use of continuation-shooting algorithm for periodic solutions of nonlinear non-autonomous dynamics system. Results show that the parameters of rotor bearing system should be designed carefully in order to obtain period-1 motion.

Reliability Improvement of Auxiliary Bearing in Magnetic Bearing System

2003 ◽  
Vol 2003.78 (0) ◽  
pp. _11-43_-_11-44_
Author(s):  
Satoshi KAMEI ◽  
Yoshiki KADOYA ◽  
Yoshitaka INOUE
Keyword(s):  
Magnetic Bearing ◽  
Reliability Improvement ◽  
Auxiliary Bearing ◽  
Bearing System

Adaptive Control of Active Magnetic Bearings to Prevent Rotor-Bearing Contact

2006 ◽  
Author(s):  
Abdul-Hadi G. Abulrub ◽  
M. Necip Sahinkaya ◽  
Clifford R. Burrows ◽  
Patrick S. Keogh
Keyword(s):  
Adaptive Control ◽  
Sudden Change ◽  
Experimental System ◽  
Magnetic Bearing ◽  
Open Loop ◽  
Contact Dynamics ◽  
Magnetic Bearings ◽  
Control Force ◽  
Active Magnetic Bearings ◽  
The Impact

Active Magnetic Bearing (AMB) systems offer various advantages over conventional bearings but due to their limited force capacity, with high levels of vibrations the rotor may come into contact with retainer bearings. Under conventional PID control, when a rotor comes into contact with its retainer bearings it remains in contact, until the rotor is run down and the system shut down. This may not be acceptable in some applications, such as aerospace and automotive applications. In this paper, a recursive open-loop adaptive control (ROLAC) algorithm is presented, as an extension of the existing open loop adaptive controller (OLAC), that updates the control force amplitude and phase at each sampling period for rapid response to changes in external excitations. The effectiveness of the algorithm in counteracting a sudden change of rotor unbalance is demonstrated by simulation and experimental results. The experimental system consists of a flexible 2 m long rotor with a mass of 100 kg supported by two radial active magnetic bearings. A simulation model of the system, including the contact dynamics, was used to assess the feasibility of the suggested controller before applying it to the experimental system. Depending on excitation levels, it is shown that the proposed controller is fast enough to prevent contact in most cases. If contact does occur the impact is minimized, and the method is able to recover the rotor position quickly. The proposed controller is implemented in real time and applied to the experimental system. It is shown that the controller works efficiently as predicted by the simulation studies.

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.

Dynamic Behavior Analysis of Touchdown Process in Active Magnetic Bearing System Based on Kalman Filtering

2014 ◽  
Author(s):  
Zhe Sun ◽  
Xiao Kang ◽  
Jingjing Zhao ◽  
Guojun Yang ◽  
Zhengang Shi
Keyword(s):  
Dynamic Analysis ◽  
Dynamic Model ◽  
Kalman Filtering ◽  
Experimental System ◽  
Magnetic Bearing ◽  
Active Magnetic Bearing ◽  
Extended Kalman Filtering ◽  
Experiment Data ◽  
Filtering Technique ◽  
Bearing System

Magnetic bearings are widely applied in High Temperature Gas-cooled Reactor (HTGR) and auxiliary bearings are important backup and safety components in AMB systems. The dynamic analysis of the AMB rotors touchdown process is an important foundation for designing auxiliary bearings. In this paper, a data-based dynamic analysis of the touchdown process is proposed. The dynamic model of the touchdown process is firstly established and then the nonlinear extended Kalman filtering technique is applied. Based on the dynamic model and Kalman filtering technique, the proposed method can offer estimations of rotor’s displacements, velocities and accelerations from noisy observations. The proposed method is validated by the experiment data from touchdown experiments. The touchdown experiments are performed on an experimental system with a 440kg heavy rotor, the rotational speed in the experiments is 5000RPM and no brake is applied.

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