An identification algorithm for rigid body mode systems

2002 ◽  
Author(s):  
K. Ohnishi
Keyword(s):  
Rigid Body ◽  
Identification Algorithm ◽  
Rigid Body Mode

Five Pad Tilting Pad Bearing Design and Lateral Vibration Characteristics of Small Gas Turbine Supported by It and Roller Bearing

2011 ◽  
Author(s):  
Jin Woong Ha ◽  
Ji Ho Myung ◽  
Jhin Ik Suk
Keyword(s):  
Rigid Body ◽  
Gas Turbine ◽  
Dynamic Properties ◽  
Roller Bearing ◽  
Rigid Body Mode ◽  
Conical Shape ◽  
Tilting Pad ◽  
Bearing Design ◽  
Industrial Gas Turbine ◽  
Selection Of

In tilting pad bearing design process, the selection of the proper configuration type of either a Load-Between-Pad (LBP) or Load-On-Pad (LOP) as well as preload and pivot offset conditions is to be carefully considered. Also the bearing needs to be designed in order to be suited for the rotor-bearing system and operating condition. In this paper, it is observed that the static and dynamic characteristics of a five pad tilting pad bearing for the LBP and LOP configurations are influenced by the variation of preload and pivot offset. In this context, rotor dynamic analysis of the 5 MW industrial gas turbine supported by the tilting pad bearing at the front and roller bearing at the rear is carried out based on the dynamic coefficients of the tilting pad bearing investigated. The result shows that two rigid body critical modes experience various changes according to the influence of the tilting pad bearing uniquely applied to one side of this machine. Mainly, the second critical speed, the rigid body mode of conical shape with high whirling in the tilting pad bearing, is significantly changed by preload and pivot offset regardless of the LBP and LOP configurations. And the first critical mode, the rigid body mode of conical shape with high whirling in the roller bearing, is sensitively affected by preload applied to the LOP configuration and by its asymmetric dynamic properties.

Calculation of Rigid-Body Motion of Integrated Raft Isolation System

2012 ◽  
Vol 184-185 ◽  
pp. 80-85
Author(s):  
Zhi Qiang Lv ◽  
Wei Xu ◽  
Chang Geng Shuai
Keyword(s):  
Rigid Body ◽  
Rigid Body Motion ◽  
Body Motion ◽  
Design Stage ◽  
Motion Model ◽  
Isolation System ◽  
Rigid Body Mode ◽  
Mode Behavior ◽  
Elastic Couplings ◽  
Six Degree Of Freedom

Integrated raft isolation system (IRIS) has some advantages over raft system of much smaller scale, such as higher isolation efficiency, less use of elastic couplings, etc. But the calculation of IRIS’s dynamic characteristics is complex. Finite element method usually adopted by raft designers is inefficient due to the iterative nature of design process. In this paper a six-degree-of-freedom rigid-body motion model is presented to calculate the static，quasi-static and rigid-body mode behavior of IRIS. The model is especially suitable to compare different design schemes and select out feasible ones efficiently at the initial design stage of IRIS.

scholarly journals Suppression of vertical bending and rigid-body-mode vibration in railway vehicle car body by primary and secondary suspension control: Results of simulations and running tests using Shinkansen vehicle

2009 ◽  
Vol 223 (6) ◽  
pp. 517-531 ◽  
Author(s):  
Y Sugahara ◽  
A Kazato ◽  
R Koganei ◽  
M Sampei ◽  
S Nakaura
Keyword(s):  
Rigid Body ◽  
Ride Comfort ◽  
Ride Quality ◽  
Railway Vehicle ◽  
Quality Level ◽  
Bending Vibration ◽  
Car Body ◽  
Rigid Body Mode ◽  
Bending Mode ◽  
Mode Vibration

To improve ride comfort in railway vehicles, the suppression of vertical bending vibration and rigid-body-mode vibration in the car body is essential. In this paper, a system is proposed that aims to reduce bending and rigid-body-mode vibration simultaneously by introducing damping control devices in the primary and secondary suspensions. The technique involves a control system of primary vertical dampers and air springs; the former are used to suppress the first bending mode vibration; the latter, to suppress the rigid-body-mode vibration. The results of both simulations and vehicle running tests on the Sanyo—Shinkansen line demonstrate that this system reduced vertical vibrations in the bogies and the car body using the sky-hook control theory. In the running tests in particular, the system reduced the vertical vibration acceleration PSD peak value in the first bending mode to almost 20 per cent and in the rigid body mode to almost 50 per cent compared with the case when the system was not used. As a result, the ride quality level LT (a widely used index of ride comfort in Japan) decreased by at least 3 dB, indicating greater ride comfort.

scholarly journals Comparison of Force Reconstruction Methods for a Lumped Mass Beam

1997 ◽  
Vol 4 (4) ◽  
pp. 231-239 ◽  
Author(s):  
Vesta I. Bateman ◽  
Randall L. Mayes ◽  
Thomas G. Carne
Keyword(s):  
Rigid Body ◽  
Applied Force ◽  
Mode Shapes ◽  
Reconstruction Method ◽  
Lumped Mass ◽  
Elastic Mode ◽  
Rigid Body Mode ◽  
Reconstruction Methods ◽  
Weighting Vector ◽  
Force Reconstruction

Two extensions of the force reconstruction method, the sum of weighted accelerations technique (SWAT), are presented in this article. SWAT requires the use of the structure’s elastic mode shapes for reconstruction of the applied force. Although based on the same theory, the two new techniques do not rely on mode shapes to reconstruct the applied force and may be applied to structures whose mode shapes are not available. One technique uses the measured force and acceleration responses with the rigid body mode shapes to calculate the scalar weighting vector, so the technique is called SWAT-CAL (SWAT using a calibrated force input). The second technique uses the free-decay time response of the structure with the rigid body mode shapes to calculate the scalar weighting vector and is called SWAT-TEEM (SWAT using time eliminated elastic modes). All three methods are used to reconstruct forces for a simple structure.

On the quasi-rigid body motion of the head actuator assembly in hard disk drives

2002 ◽  
Vol 216 (12) ◽  
pp. 1259-1262
Author(s):  
S Zeng
Keyword(s):  
Rigid Body ◽  
Vibration Mode ◽  
Hard Disk Drives ◽  
Hard Disk ◽  
Areal Density ◽  
Body Motion ◽  
Fe Model ◽  
Disk Drives ◽  
Rigid Body Mode ◽  
Set Up

A quasi-rigid (QR) vibration mode between 3 and 5 kHz is common in current hard disk drives (HDDs), which hinders servo bandwidth improvement and thus limits growth in the areal density (numbers of bits that can be stored per unit area) of HDDs. In this paper, a finite element (FE) model of a head actuator assembly (HAA) is developed and an experimental set-up is established to study the quasi-rigid body mode. The FE model result is compared with the experimental data. It is found that the quasi-rigid body mode is in fact a butterfly-like mode, which integrates the flexibility of the pivot assembly as well as the flexibility and the mass of the whole head actuator body.

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