On Using a Strong High-Frequency Excitation for Parametric Identification of Nonlinear Systems

2017 ◽  
Vol 139 (5) ◽  
Author(s):  
Abdraouf Abusoua ◽  
Mohammed F. Daqaq
Keyword(s):  
High Frequency ◽  
Nonlinear Models ◽  
Modulation Frequency ◽  
Parametric Method ◽  
Harmonic Excitation ◽  
Restoring Force ◽  
Nonlinear Parameters ◽  
High Frequency Excitation ◽  
Frequency Excitation ◽  
Slow Modulation

This paper describes a new parametric method for the development of nonlinear models with parameters identified from an experimental setting. The approach is based on applying a strong nonresonant high-frequency harmonic excitation to the unknown nonlinear system and monitoring its influence on the slow modulation of the system's response. In particular, it is observed that the high-frequency excitation induces a shift in the slow-modulation frequency and a static bias in the mean of the dynamic response. Such changes can be directly related to the amplitude and frequency of the strong excitation offering a unique methodology to identify the unknown nonlinear parameters. The proposed technique is implemented to identify the nonlinear restoring-force coefficients of three experimental systems. Results demonstrate that this technique is capable of identifying the nonlinear parameters with relatively good accuracy.

The Rotationally Flexible Pendulum Subjected to a High Frequency Excitation

1990 ◽  
Vol 57 (3) ◽  
pp. 725-730 ◽  
Author(s):  
Bertram A. Schmidt
Keyword(s):  
High Frequency ◽  
Harmonic Excitation ◽  
Flexible Parts ◽  
High Frequency Excitation ◽  
Frequency Excitation ◽  
High Frequency Harmonic ◽  
Frequency Harmonic

A high frequency harmonic excitation is applied to the pivot of a rotationally flexible pendulum. It is found that various equilibrium positions occur depending on the stiffness of the flexible parts.

Experimental Evidence of Vibrational Resonance in a Bi-Stable Twin-Well Mechanical Oscillator

2017 ◽  
Author(s):  
Abdraouf Abusoua ◽  
Mohammed F. Daqaq
Keyword(s):  
Experimental Evidence ◽  
High Frequency ◽  
Harmonic Excitation ◽  
Nonlinear Phenomenon ◽  
Resonant Response ◽  
Mechanical Oscillator ◽  
Vibrational Resonance ◽  
Electrical Systems ◽  
High Frequency Excitation ◽  
Frequency Excitation

Vibrational Resonance (VR) is a nonlinear phenomenon which occurs when a bi-stable system is subjected to a bi-harmonic excitation consisting of a small-amplitude resonant excitation and a large-amplitude high-frequency excitation. The result is that, under some conditions, the high-frequency excitation amplifies the resonant response associated with the slow dynamics. While VR was studied extensively in the open literature, most of the research studies used optical and electrical systems as platforms for experimental investigation. This paper provides experimental evidence that VR can also occur in a mechanical bi-stable twin-well oscillator and discusses the conditions under which VR is possible.

The Radially Flexible Pendulum Subjected to a High-Frequency Excitation

1983 ◽  
Vol 50 (2) ◽  
pp. 443-448 ◽  
Author(s):  
B. A. Schmidt
Keyword(s):  
High Frequency ◽  
Radial Direction ◽  
Harmonic Excitation ◽  
Stable Motion ◽  
Fixed Direction ◽  
Approximate Equilibrium ◽  
High Frequency Excitation ◽  
Frequency Excitation ◽  
High Frequency Harmonic ◽  
Frequency Harmonic

A high-frequency harmonic excitation is applied to a pendulum that is flexible in the radial direction. Approximate equilibrium positions are found when the excitation is in a general and fixed direction. An approximate stable motion is found when the direction of the excitation changes constantly and slowly. It is found that the excitation causes a reduction of the radius.

Stiffening Effects of High-Frequency Excitation: Experiments for an Axially Loaded Beam

1999 ◽  
Vol 67 (2) ◽  
pp. 397-402 ◽  
Author(s):  
J. S. Jensen ◽  
D. M. Tcherniak ◽  
J. J. Thomsen
Keyword(s):  
High Frequency ◽  
Harmonic Excitation ◽  
General Tendency ◽  
Beam Model ◽  
Very High Frequency ◽  
Simple Analytical Expression ◽  
Theoretical Predictions ◽  
High Frequency Excitation ◽  
Frequency Excitation ◽  
Very High

According to theoretical predictions one can change the effective stiffness or natural frequency of an elastic structure by employing harmonic excitation of very high frequency. Here we examine this effect for a hinged-hinged beam subjected to longitudinal harmonic excitation. A simple analytical expression is presented, that relates the effective natural frequencies of the beam to the intensity of harmonic excitation. Experiments performed with a laboratory beam confirm the general tendency of this prediction, though there are discrepancies that cannot be explained in the framework of the linear Galerkin-discretized beam model. [S0021-8936(00)01302-7]

scholarly journals Empirical Expression for AC Magnetization Harmonics of Magnetic Nanoparticles under High-Frequency Excitation Field for Thermometry

Nanomaterials ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 2506
Author(s):  
Zhongzhou Du ◽  
Dandan Wang ◽  
Yi Sun ◽  
Yuki Noguchi ◽  
Shi Bai ◽  
...  
Keyword(s):  
Magnetic Nanoparticles ◽  
High Frequency ◽  
Planck Equation ◽  
Magnetization Dynamics ◽  
Excitation Field ◽  
Fokker Planck Equation ◽  
High Frequency Excitation ◽  
Frequency Excitation ◽  
Ac Magnetization ◽  
Fokker Planck

The Fokker–Planck equation accurately describes AC magnetization dynamics of magnetic nanoparticles (MNPs). However, the model for describing AC magnetization dynamics of MNPs based on Fokker-Planck equation is very complicated and the numerical calculation of Fokker-Planck function is time consuming. In the stable stage of AC magnetization response, there are differences in the harmonic phase and amplitude between the stable magnetization response of MNPs described by Langevin and Fokker–Planck equation. Therefore, we proposed an empirical model for AC magnetization harmonics to compensate the attenuation of harmonics amplitude induced by a high frequency excitation field. Simulation and experimental results show that the proposed model accurately describes the AC M–H curve. Moreover, we propose a harmonic amplitude–temperature model of a magnetic nanoparticle thermometer (MNPT) in a high-frequency excitation field. The simulation results show that the temperature error is less than 0.008 K in the temperature range 310–320 K. The proposed empirical model is expected to help improve MNPT performance.

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