Transient Unbalance Response of Four Multilobe Journal Bearings

1980 ◽  
Vol 102 (3) ◽  
pp. 300-306 ◽  
Author(s):  
P. E. Allaire ◽  
D. F. Li ◽  
K. C. Choy
Keyword(s):  
Fourier Transform ◽  
Fast Fourier Transform ◽  
Transient Response ◽  
Journal Bearings ◽  
Stability Threshold ◽  
Unbalance Response ◽  
Fast Fourier Transform Analysis ◽  
Linearized Stability ◽  
The Stability

This work carries out an analysis of the transient response of four multilobe journal bearings (elliptical, offset, three-lobe, and four-lobe) subject to unbalance both below and above the linearized stability thresholds for the bearings. It extends the work of a previous paper on a balanced rotor in the same four bearing types. Transient orbits, bearing forces, and a numerical fast Fourier transform analysis of the orbits are presented. A comparison of bearing forces above the stability threshold for each bearing indicates that the elliptical bearing has the most violent whirl vibration amplitudes, while the offset bearing exhibits the least amount of subsynchronous vibration.

Stability and Transient Characteristics of Four Multilobe Journal Bearing Configurations

1980 ◽  
Vol 102 (3) ◽  
pp. 291-298 ◽  
Author(s):  
D. F. Li ◽  
K. C. Choy ◽  
P. E. Allaire
Keyword(s):  
Transient Analysis ◽  
Journal Bearing ◽  
Journal Bearings ◽  
Rigid Rotor ◽  
Frequency Content ◽  
Stability Threshold ◽  
Fast Fourier Transform Analysis ◽  
Linearized Stability ◽  
Nonlinear Transient ◽  
The Stability

Multilobe journal bearings are often used to improve the stability response of rotating machinery. Such machines operate near the stability threshold of the bearing-rotor system. This work determines the linearized stability threshold of four multilobe journal bearings: elliptical, offset elliptical, three lobe, and four lobe. A nonlinear transient analysis of a rigid rotor in each of these bearings is carried out above and below the threshold speed. Shaft orbits and bearing forces are calculated. A numerical fast Fourier transform analysis is used to obtain the frequency content of the nonlinear orbit.

Short Bearing Analysis Applied to Rotor Dynamics—Part 2: Results of Journal Bearing Response

1976 ◽  
Vol 98 (2) ◽  
pp. 319-329 ◽  
Author(s):  
R. G. Kirk ◽  
E. J. Gunter
Keyword(s):  
Transient Response ◽  
Journal Bearing ◽  
Rotor Dynamics ◽  
Journal Bearings ◽  
Radius Of Curvature ◽  
Extensive Investigation ◽  
Stability Threshold ◽  
Stability Maps ◽  
And Performance ◽  
The Stability

The results of an extensive investigation of the transient response of rotors supported in fluid-film journal bearings is presented in the form of computer generated orbits of rotor motion. The stability of the rotor-bearing system was determined by examination of the system characteristic equation in Part 1. Rotor transient response orbits demonstrate the rotor behavior below and above the stability threshold. The results show the effect of imbalance, steady loading, cyclic unidirectional and rotating loads upon the stability and performance of a short journal bearing. The results are compared to previous investigations and modified stability maps are deduced from the results obtained. The concept of whirl is examined and several plots presented of the instantaneous whirl ratio and radius of curvature versus cycles of motion (of the journal) for the various cases considered. Bearing forces are analyzed and the resulting plots of force versus cycles of motion are presented for selected cases.

Fast Fourier transform analysis as a new tool for Olympic rifle coaches

2016 ◽  
Vol 231 (1) ◽  
pp. 63-67 ◽  
Author(s):  
Grzegorz Gladyszewski ◽  
Bozena Gladyszewska
Keyword(s):  
Fourier Transform ◽  
Fast Fourier Transform ◽  
Average Frequency ◽  
Quantitative Information ◽  
Training System ◽  
Fast Fourier Transform Analysis ◽  
Study Results ◽  
Using Data ◽  
The Stability

The aim of this study was to examine the possibility of using data collected with an electronic training system to determine the influence of a shooter’s heartbeat on shooting precision. Shooting sessions of a rifle in prone position were studied with the use of an electronic training system. As a case study, results of an experienced shooter were analyzed. Fast Fourier transform was applied to raw data extracted from the system and then results were interpreted. The spectrum obtained revealed a wide peak at the frequency f = 2.6 Hz that was considered as the second harmonics of the average frequency corresponding to the heartbeat decreasing down to 69 beats/min when releasing a shot. The session finished with a very modest score of 611.3 points. When a small intentional change in the shooter’s equipment (a sling position) was introduced, the spectrum obtained did not reveal any peaks and the shooter reached a much better score of 621.8 points. The use of fast Fourier transform analysis is proposed as a new tool for Olympic rifle shooters and coaches. This new tool does not require any complicated procedures and provides quantitative information on the influence of a heartbeat on the stability of a shooter’s aim.

Investigation of the stability of periodic motions in a nonlinear automatic control system based on the fast fourier transform

2003 ◽  
Vol 3 ◽  
pp. 297-307
Author(s):  
V.V. Denisov
Keyword(s):  
Fourier Transform ◽  
Control System ◽  
Automatic Control ◽  
Fast Fourier Transform ◽  
Automatic Control System ◽  
Resonance Phenomenon ◽  
Periodic Motions ◽  
Multiply Connected ◽  
Non Linear ◽  
The Stability

An approach to the study of the stability of non-linear multiply connected systems of automatic control by means of a fast Fourier transform and the resonance phenomenon is considered.

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