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Critical speed

About: Critical speed is a research topic. Over the lifetime, 2764 publications have been published within this topic receiving 31365 citations.


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TL;DR: In this article, the dynamics of an overhung rotor system near the regimes of Sommerfeld effect was studied by using a discrete and a continuous shaft-rotor model coupled with the model of the non-ideal motor drive.
Abstract: Deflection of a rotor-disk at the free end of a flexible overhung rotor-shaft causes rotation about diametral axis and consequently leads to a strong gyroscopic coupling in a spinning overhung rotor system. When the rotor is spun up about its axis, the unbalance in the rotor-disk causes transverse and rotational vibrations to increase as the spin speed approaches the critical speed of the rotor. These transverse and rotational vibrations dissipate a lot of energy, and if the rotor is driven through a non-ideal drive, i.e., a motor which can supply a limited amount of power, then the entire motor power may be spent to account for the energy dissipation. As a result, the rotor speed may get stuck in resonance at the critical speed or jump through the critical speed to a much higher speed with lower transverse and rotational vibration levels. These symptoms, normally referred to as the Sommerfeld effect, occur due to the intrinsic energetic coupling between the drive and the driven systems and are important design considerations for development of various rotating machinery with flexible rotor-shafts or supports (bearings). Sommerfeld effect in a strongly gyroscopic rotor dynamic system is studied in this article. The dynamics of an overhung rotor system near the regimes of Sommerfeld effect is studied by using a discrete and a continuous shaft-rotor model coupled with the model of the non-ideal motor drive. The models are developed using multi-energy domain modeling approach in bond graph model form. A steady-state analysis of power transfer mechanism is used to postulate the ideal characteristics of Sommerfeld effect in the neighborhood of the critical speed, and thereafter, full transient analysis is performed with aid of the bond graph model-generated coupled equations of motion to validate the postulated characteristics of the Sommerfeld effect.

23 citations

Journal ArticleDOI
TL;DR: In this paper, a dynamic model of the vehicle system including a semi-carbody and a bogie is established, and the bifurcation diagrams of the two types of high speed vehicles are extensively studied.
Abstract: The China high speed railway vehicles of type CRH2 and type CRH3, modeled on Japanese high speed Electric Multiple Units (EMU) E2 series and Euro high speed EMU ICE3 series possess different stability behaviors due to the different matching relations between bogie parameters and wheel profiles. It is known from the field tests and roller rig tests that, the former has a higher critical speed while large limit cycle oscillation appears if instability occurs, and the latter has lower critical speed while small limit cycle appears if instability occurs. The dynamic model of the vehicle system including a semi-carbody and a bogie is established in this paper. The bifurcation diagrams of the two types of high speed vehicles are extensively studied. By using the method of normal form of Hopf bifurcation, it is found that the subcritical and supercritical bifurcations exist in the two types of vehicle systems. The influence of parameter variation on the exported function Rec 1(0) in Hopf normal form is studied and numerical shooting method is also used for mutual verification. Furthermore, the bifurcation situation, subcritical or supercritical, is also discussed. The study shows that the sign of Re(λ) determinates the stability of linear system, and the sign of Rec 1(0) determines the property of Hopf bifurcation with Rec 1(0)>0 for supercritical and Rec 1(0)<0 for subcritical.

23 citations

Journal ArticleDOI
TL;DR: In this paper, a model-based mechatronic approach for the design of ball-screw driven servomechanisms is proposed, aimed at selecting the optimal combination of electric motor and ball screw which minimizes the motor torque, while ensuring the achievement of the prescribed dynamic performances of the closed loop system.

23 citations

Journal ArticleDOI
TL;DR: In this paper, the effect of elastic motor connection on the bogie frame is examined by linear and nonlinear calculations, which shows that stiffness and damping properties of motor connection have a strong influence on vehicle stability.
Abstract: Considering the specific case of a concentrated power locomotive with motors mounted on the bogie frame, the paper reviews the criteria for nonlinear assessment of vehicle stability based on the simulation of vehicle response to random track irregularity, showing the need for more objective criteria than the ones based on physical testing for vehicle homologation. The effect of elastic motor connection on the bogie frame is examined by linear and nonlinear calculations, which shows that stiffness and damping properties of motor connection have a strong influence on vehicle stability.

23 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
20241
202343
2022120
202182
202092
2019102