General Comparison between Ball Bearing Wheels and Magnetic Bearing Wheel

Gyrodynamics ◽  
1974 ◽  
pp. 100-109
Author(s):  
J. C. Oudin
Keyword(s):  
Ball Bearing ◽  
Magnetic Bearing

Dynamic Analysis of Active Magnetic Bearing Rotor Dropping on Auto-eliminating Clearance Auxiliary Bearing Devices

2015 ◽  
Vol 137 (6) ◽  
Author(s):  
Chengtao Yu ◽  
Chaowu Jin ◽  
Xudong Yu ◽  
Longxiang Xu
Keyword(s):  
Dynamic Models ◽  
Ball Bearing ◽  
Experimental Studies ◽  
Magnetic Bearing ◽  
Active Magnetic Bearing ◽  
Grease Lubrication ◽  
Successful Operation ◽  
Convex Shape ◽  
Auxiliary Bearing ◽  
The Impact

Auto-eliminating clearance auxiliary bearing devices (ACABD) can automatically eliminate the protective clearance between the ball bearing's outer race and the ACABD's supports, thus recenter the rotor when active magnetic bearing (AMB) system fails. This paper introduces the mechanical structure and working principles of the ACABD. When the rotor drops, numerical and experimental studies on the transient responses of the rotor and the ACABD's supports are also conducted as follows. First, we propose an equivalent clearance circle method to establish dynamic models of rotor dropping on the ACABD. Based on these models, the rotor dropping simulations are carried out to investigate the modes of lubrication and the ACABD's support shape's influences on the performance and execution time of clearance elimination. Second, various AMB rotor dropping tests are performed on our experimental setup with different ACABD supporting conditions. Indicated from the basically consistent simulation and experimental results, the correctness of the theoretical analysis and the successful operation of ACABD have been verified. Moreover, with the grease lubrication in the ball bearing and convex shape supports, the ACABD can eliminate the protective clearance within approximately 0.5 s upon the rotor drops and then sustain the rotor to operate stably around its original rotation center. Because of clearance elimination, the dramatic impact between the ball bearing and the supports is avoided and the impact forces among each part are effectively reduced. Meanwhile, the possibility of incurring full-clearance backward whirling motion is eliminated.

Vibration Control of a Nonlinear Rotor System through Electro-Magnetic Bearings

2012 ◽  
Vol 452-453 ◽  
pp. 1408-1414
Author(s):  
Jun Liu ◽  
Qiao Sun
Keyword(s):  
Vibration Control ◽  
Ball Bearing ◽  
Control Method ◽  
Nonlinear Effects ◽  
Magnetic Bearing ◽  
Rotor System ◽  
Delay Estimation ◽  
Rotor Imbalance ◽  
Speed Range ◽  
Electro Magnetic

In rotating machinery, vibration resonance with large amplitude and complex pattern occurs at critical speeds due to rotor imbalance and nonlinear effects. In this paper, a vibration control method is proposed for a rotor system supported by a ball bearing and an electro-magnetic bearing. In particular, a disturbance observer combined with the current delay estimation is implemented to improve the controller's ability of compensating for system's nonlinear effects and uncertainty. As a result, the rotor vibration is suppressed to very small amplitudes in the entire operating speed range. The proposed method is validated through numerical simulations and experiments.

Magnetic Bearing for Reaction Wheels in Space Applications

2005 ◽  
Author(s):  
T. R. Haridas ◽  
M. H. Ravichandran ◽  
P. V. Unnikrishnan ◽  
C. C. Joseph ◽  
Robert Devasahayam
Keyword(s):  
Attitude Control ◽  
Ball Bearing ◽  
Rate Capability ◽  
Magnetic Bearing ◽  
Friction Torque ◽  
Reaction Wheel ◽  
Space Applications ◽  
Imaging Application ◽  
Resolution Imaging ◽  
The Stability

Reaction wheels are used as actuators for attitude control of satellites. Ball bearing is being used in reaction wheel application since many decades. Even small variations in friction torque in ball bearings affects the pointing stability of the satellites used for high resolution imaging application. Also the bi-directional operation of reaction wheel requires frequent zero speed crossing. The stiction present in ball bearing wheels affects the stability during zero speed cross over. Magnetic Bearings have distinct advantages over conventional bearings, like zero friction (due to non-contact operation), no lubrication, long life, less power, etc. Absence of lubrication in magnetic bearing makes it compatible to harsh environments like vacuum. It provides smooth zero speed cross over due to negligible stiction, which is advantageous to achieve better pointing stability. The context of this paper benchmarks the design, simulation and test results of a two axes actively controlled magnetic bearing. The wheel is designed to have adequate slew rate capability to ensure non-contact operation during satellite maneuvers.

Vibrations of turbo-molecular vacuum pumps with high stable magnetic bearings operating within electronic microscope systems

1991 ◽  
Vol 49 ◽  
pp. 368-369
Author(s):  
C. A. Thomas ◽  
K. P. Reimer
Keyword(s):  
Ball Bearing ◽  
Low Frequency ◽  
Magnetic Bearing ◽  
Dynamic Effects ◽  
Rotating Shaft ◽  
Low Frequency Stimulation ◽  
Pump Housing ◽  
Frequency Stimulation ◽  
Electronic Microscope ◽  
Bearing System

In order to operate Electronic Microscopes vibration free, it is necessary to assemble the apparatus on a vibration free isolated desk. Similarly, strict requirements, regarding vibrations, are demanded from the attached vacuum pump which provides vacuum for the system. The rotor and rotating shaft of Turbo Molecular Pumps with mechanical bearings are connected to the pump housing by means of ball bearings. The inertia and vibration component resulting from the ball bearing dynamic effects produce the vibration results as indicated in Fig. 1.In order to design a Turbo Molecular Pump with minimum vibration effects it was necessary to provide the pump with a magnetic bearing system containing 4 passive and 1 active controlled axis. This magnetic bearing system is less sensitive to vibration and simpler in assembly than other existing more complicated 5-axis active controlled versions. However it is more complication than the mechanical bearing type. The magnet bearing is provided with a touch-down bearing. Larger pump movements due to high or low frequency stimulation recieved via the microscope desk could result in forcing the shaft out of its magnet-bearing-centre position, the touch-down bearing now re-centres the shaft allowing immediate magnetic bearing centre recovery.

Effect of Misalignment of Retainer Bearings on Dynamic Responses of Rotor System During Emergency Stop

2007 ◽  
Author(s):  
Antti Y. J. Ka¨rkka¨inen ◽  
Marlene Helfert ◽  
Beat Aeschlimann ◽  
Aki M. Mikkola ◽  
Jussi T. Sopanen
Keyword(s):  
Simulation Model ◽  
Ball Bearing ◽  
Magnetic Bearing ◽  
Magnetic Bearings ◽  
Active Magnetic Bearing ◽  
Dynamic Responses ◽  
Active Magnetic Bearings ◽  
Detailed Simulation ◽  
Emergency Stop ◽  
The Magnetic Field

The active magnetic bearings present a technology which has many advantages compared to traditional bearing concepts. Active magnetic bearings, however, require retainer bearings in order to prevent damages in the event of a component, power or a control system failure. In the drop-down, when the rotor drops from the magnetic field on the retainer bearings, the design of the retainer bearings has a significant influence on the dynamic behavior of the rotor. In this study, the dynamics of an active magnetic bearing supported rotor during the drop on retainer bearings is studied employing a detailed simulation model. The retainer bearings are modeled using a detailed ball bearing model while the flexibility of the rotor is described using the component mode synthesis. The model is verified by comparing measurements carried out using an existing test rig and simulation results. In this study, the verified simulation model is employed studying the effect of misalignment of retainer bearings during the rotor drop-down on the retainer bearings. It is noted that the misalignment of the retainer bearings is harmful and can produce whirling motion of the rotor.

Dynamic Analysis of Rotor System With Misaligned Retainer Bearings

2008 ◽  
Vol 130 (2) ◽  
Author(s):  
Antti Kärkkäinen ◽  
Marlene Helfert ◽  
Beat Aeschlimann ◽  
Aki Mikkola
Keyword(s):  
Simulation Model ◽  
Ball Bearing ◽  
Magnetic Bearing ◽  
Magnetic Bearings ◽  
Active Magnetic Bearing ◽  
System Failure ◽  
Active Magnetic Bearings ◽  
The Finite Element Method ◽  
Whirling Motion ◽  
The Magnetic Field

Active magnetic bearings present a technology that has many advantages compared to traditional bearing concepts. Active magnetic bearings, however, require retainer bearings in order to prevent damages in the event of a component, power, or a control system failure. In the drop-down, when the rotor drops from the magnetic field on the retainer bearings, the design of the retainer bearings has a significant influence on the dynamic behavior of the rotor. In this study, the dynamics of an active magnetic bearing supported rotor during the drop on retainer bearings is studied employing a simulation model. The retainer bearings are modeled using a detailed ball bearing model while the flexibility of the rotor is described using the finite element method with component mode synthesis. The model is verified by comparing measurements carried out using an existing test rig and simulation results. In this study, the verified simulation model is employed studying the effect of misalignment of retainer bearings during the rotor drop-down on the retainer bearings. It is concluded in this study that the misalignment of the retainer bearings is harmful and can lead to whirling motion of the rotor.

Ball bearing turbocharger vibration management: application on high speed balancer

2020 ◽  
Vol 21 (6) ◽  
pp. 619
Author(s):  
Kostandin Gjika ◽  
Antoine Costeux ◽  
Gerry LaRue ◽  
John Wilson
Keyword(s):  
Dynamic Behavior ◽  
High Speed ◽  
Internal Combustion Engines ◽  
Ball Bearing ◽  
Squeeze Film ◽  
Design And Technology ◽  
Squeeze Film Damper ◽  
Damping Coefficients ◽  
Bearing Loads ◽  
Stiffness And Damping

Today's modern internal combustion engines are increasingly focused on downsizing, high fuel efficiency and low emissions, which requires appropriate design and technology of turbocharger bearing systems. Automotive turbochargers operate faster and with strong engine excitation; vibration management is becoming a challenge and manufacturers are increasingly focusing on the design of low vibration and high-performance balancing technology. This paper discusses the synchronous vibration management of the ball bearing cartridge turbocharger on high-speed balancer and it is a continuation of papers [1–3]. In a first step, the synchronous rotordynamics behavior is identified. A prediction code is developed to calculate the static and dynamic performance of “ball bearing cartridge-squeeze film damper”. The dynamic behavior of balls is modeled by a spring with stiffness calculated from Tedric Harris formulas and the damping is considered null. The squeeze film damper model is derived from the Osborne Reynolds equation for incompressible and synchronous fluid loading; the stiffness and damping coefficients are calculated assuming that the bearing is infinitely short, and the oil film pressure is modeled as a cavitated π film model. The stiffness and damping coefficients are integrated on a rotordynamics code and the bearing loads are calculated by converging with the bearing eccentricity ratio. In a second step, a finite element structural dynamics model is built for the system “turbocharger housing-high speed balancer fixture” and validated by experimental frequency response functions. In the last step, the rotating dynamic bearing loads on the squeeze film damper are coupled with transfer functions and the vibration on the housings is predicted. The vibration response under single and multi-plane unbalances correlates very well with test data from turbocharger unbalance masters. The prediction model allows a thorough understanding of ball bearing turbocharger vibration on a high speed balancer, thus optimizing the dynamic behavior of the “turbocharger-high speed balancer” structural system for better rotordynamics performance identification and selection of the appropriate balancing process at the development stage of the turbocharger.

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