Gas Foil Bearings with Radial Injection: Multi-domain Stability Analysis and Unbalance Response

Rotors supported on gas foil bearings have low damping characteristics, which limits its application. A possible solution could be an integration of a gas foil bearing with an electromagnetic actuator. This paper discusses the effect of electromagnetic actuators on the stability of a rotor supported on gas foil bearings. A coupled dynamic model combining the dynamics of gas foil bearing and electromagnetic actuator has been developed. The fluid film forces from the gas foil bearings and the electromagnetic forces from the electromagnetic actuators are integrated into the equations of motion of the rotor. The sub-synchronous vibration present in case of conventional gas foil bearings is reduced and the stability band of the rotor is increased due to the implementation of electromagnetic actuator.

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Dynamic predictor-based controls: a time-domain stability analysis

IEEE Latin America Transactions ◽

10.1109/tla.2019.8931210 ◽

2019 ◽

Vol 17 (07) ◽

pp. 1207-1213

Author(s):

Luis Juarez ◽

Sabine Mondie

Keyword(s):

Stability Analysis ◽

Time Domain ◽

Domain Stability

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Parameter Conditions for TCP/AQM Routers Based on 2-D s-z Domain Stability Analysis

IEEE Communications Letters ◽

10.1109/lcomm.2010.072910.100796 ◽

2010 ◽

Vol 14 (9) ◽

pp. 869-871 ◽

Cited By ~ 2

Author(s):

Pengxuan Mao ◽

Yang Xiao ◽

Kiseon Kim

Keyword(s):

Stability Analysis ◽

Z Domain ◽

Domain Stability

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Complex-Coefficient Frequency Domain Stability Analysis Method for a Class of Cross-Coupled Antisymmetrical Systems and Its Extension in MSR Systems

Mathematical Problems in Engineering ◽

10.1155/2014/765858 ◽

2014 ◽

Vol 2014 ◽

pp. 1-11 ◽

Cited By ~ 3

Author(s):

Yuan Ren ◽

Jiancheng Fang

Keyword(s):

Stability Analysis ◽

Frequency Domain ◽

Stability Criterion ◽

Mimo System ◽

Multiple Input Multiple Output ◽

Complex Coefficient ◽

Analysis Method ◽

Multiple Input ◽

Input Multiple Output ◽

Domain Stability

This paper develops a complex-coefficient frequency domain stability analysis method for a class of cross-coupled two-dimensional antisymmetrical systems, which can greatly simplify the stability analysis of the multiple-input multiple-output (MIMO) system. Through variable reconstruction, the multiple-input multiple-output (MIMO) system is converted into a single-input single-output (SISO) system with complex coefficients. The pole locations law of the closed-loop system after the variable reconstruction has been revealed, and the controllability as well as observability of the controlled plants before and after the variable reconstruction has been studied too, and then the classical Nyquist stability criterion is extended to the complex-coefficient frequency domain. Combined with the rigid magnetically suspended rotor (MSR) system with heavy gyroscopic effects, corresponding stability criterion has been further developed. Compared with the existing methods, the developed criterion for the rigid MSR system not only accurately predicts the absolute stability of the different whirling modes, but also directly demonstrates their relative stability, which greatly simplifies the analysis, design, and debugging of the control system.

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Experimental Analysis of the Unbalance Response of Rigid Rotors Supported on Aerodynamic Foil Bearings

Journal of Vibration and Acoustics ◽

10.1115/1.4031409 ◽

2015 ◽

Vol 137 (6) ◽

Cited By ~ 8

Author(s):

Franck Balducchi ◽

Mihai Arghir ◽

Romain Gauthier

Keyword(s):

Vibration Spectrum ◽

Rotation Speed ◽

Nonlinear Behavior ◽

Structural Damping ◽

Foil Bearings ◽

Unbalance Response ◽

Theoretical Predictions ◽

Air Film ◽

Rigid Rotors ◽

Cubic Stiffness

The paper presents the experimental unbalance response of two slightly different rigid rotors supported by aerodynamic foil bearings. Impulse (Pelton) turbines manufactured directly in the mass of the rotors (on the outer surface) entrain both rotors at rotation speeds comprised between 50 krpm and 100 krpm. The displacements in the two foil bearings are measured during coast down and are depicted as waterfall plots. They show typical nonlinear behavior, i.e., subsynchronous vibrations accompanying the synchronous component. The measurements clearly show that the subsynchronous components bifurcate or jump at typical rotation speeds (mostly rational fractions of the rotation speed). The nonlinear behavior of the rigid rotor supported on foil bearings is also emphasized by varying the added unbalance: with increasing unbalance the vibration spectrum becomes gradually more diverse as new subsynchronous vibrations appear. The experimental results are compared with very simplified theoretical predictions based on the assumption that the air film in the two bearings is infinitely stiff compared to the foil structure. The latter is characterized by a cubic stiffness and a structural damping coefficient. The comparisons show only a rough qualitative agreement.

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