scholarly journals Vibrations in Single-Degrees-of-Freedom Sampled-Data Linear Mechanical Systems

Author(s):  
Csaba Budai

This paper aims to present that the effect of sampling can result in multi-frequency vibration even in the case of a single-degree-of-freedom linear mechanical model. Even though the sampled-data systems have an infinite number of characteristic exponents due to sampling, the vibrations of these systems can still be characterized by an effective system model with a single dominant frequency. However, as this paper shows, additional harmonics become relevant, resulting in multi-frequency vibrations depending on the magnitude of applied control parameters. The vibrations presented by the time histories of vibration and their spectra resulted in numerical simulation of the sampled-data system.

Author(s):  
Takashi Ikeda ◽  
Yuji Harata ◽  
Hisashi Takahashi ◽  
Yukio Ishida

Vibration characteristics of three-blade wind turbines are investigated. The system is modeled by a coupled system of the flexible tower with two degrees of freedom and each blade with a single degree of freedom, and these blades are subjected to wind pressure which varies depending on the height from the ground. The vibrations of the three-blade wind turbines are theoretically analyzed to determine the natural frequency diagrams, frequency responses, stationary time histories and their FFT results. It is found that several peaks appear at the specific range of the rotational speed ω in the response curves because of both the wind pressure and the parametric excitation terms. In three-blade wind turbines, vibrations including predominant components of 3ω and its higher harmonics appear near these peaks. The response curves near the highest peak exhibit soft spring types due to the nonlinearities of the restoring moments of the blades. In the numerical simulations, “localization phenomena” in the blades, which vibrate at different amplitudes, are observed. The influence of an imperfection of the three blades is also examined.


1975 ◽  
Vol 97 (3) ◽  
pp. 769-775 ◽  
Author(s):  
Fan Y. Chen ◽  
N. Polvanich

The dynamic response of the cam-driven mechanism is investigated for a variety of cam motion profiles. Based on a linear, lumped system model of single degree of freedom, the results of the response characteristics of the follower are presented in the form of nondimensional primary and residual shock response spectra. These spectra are also recasted in four-coordinate log-log grid forms. The extension of this approach to treat the system model of two degrees of freedom is delineated. Furthermore, the analysis of a two-freedom model of the cam-driven system was also undertaken to clarify the effects of many system parameters and for obtaining an optimal design. Fundamental design charts are presented.


2020 ◽  
Vol 53 (2) ◽  
pp. 3482-3487
Author(s):  
Daehan Kim ◽  
Kunhee Ryu ◽  
Juhoon Back

Automatica ◽  
2021 ◽  
Vol 131 ◽  
pp. 109742
Author(s):  
Alexis J. Vallarella ◽  
Paula Cardone ◽  
Hernan Haimovich

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