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Nonlinear resonance
 Date Issued:
 2011
 Summary:
 Sustained resonance in a linear oscillator is achievable with a drive whose constant frequency matches the resonant frequency of the oscillator. In oscillators with nonlinear restoring forces, i.e., Dungtype oscillators, resonant frequency changes with amplitude, so a constant frequency drive generates a beat oscillation instead of sustained resonance. Dungtype oscillators can be driven into sustained resonance, called autoresonance (AR), when drive frequency is swept in time to match the changing resonant frequency of the oscillator. It is found that nearoptimal drive linear sweep rates for autoresonance can be estimated from the beat oscillation resulting from constant frequency excitation. Specically, a least squares estimate of the slope of the TeagerKaiser instantaneous frequency versus time plot for the rising halfcycle of the beat response to a stationary drive provides a nearoptimal estimate of the linear drive sweep rate that sustains resonance in the pendulum, Dung and DungVan der Pol oscillators. These predictions are confirmed with modelbased numerical simulations. A closedform approximation to the AMFM nonlinear resonance beat response of a Dung oscillator driven at its lowamplitude oscillator frequency is obtained from a solution to an associated Mathieu equation. AR time responses are found to evolve along a Mathieu equation primary resonance stability boundary. AR breakdown occurs at sweep rates just past optimal and map to a single stable point just off the Mathieu equation primary resonance stability boundary. Optimal AR sweep rates produce oscillating phase dierences with extrema near 90 degrees, allowing extended time in resonance. AR breakdown occurs when phase difference equals 180 degrees. Nonlinear resonance of the van der Pol type may play a role in the extraordinary sensitivity of the human ear.
Title:  Nonlinear resonance: determining maximal autoresonant response and modulation of spontaneous otoacoustic emissions. 
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Name(s): 
Witkov, Carey. Charles E. Schmidt College of Science Center for Complex Systems and Brain Sciences 

Type of Resource:  text  
Genre:  Electronic Thesis Or Dissertation  
Date Issued:  2011  
Publisher:  Florida Atlantic University  
Physical Form:  electronic  
Extent:  xv, 89 p. : ill. (some col.)  
Language(s):  English  
Summary:  Sustained resonance in a linear oscillator is achievable with a drive whose constant frequency matches the resonant frequency of the oscillator. In oscillators with nonlinear restoring forces, i.e., Dungtype oscillators, resonant frequency changes with amplitude, so a constant frequency drive generates a beat oscillation instead of sustained resonance. Dungtype oscillators can be driven into sustained resonance, called autoresonance (AR), when drive frequency is swept in time to match the changing resonant frequency of the oscillator. It is found that nearoptimal drive linear sweep rates for autoresonance can be estimated from the beat oscillation resulting from constant frequency excitation. Specically, a least squares estimate of the slope of the TeagerKaiser instantaneous frequency versus time plot for the rising halfcycle of the beat response to a stationary drive provides a nearoptimal estimate of the linear drive sweep rate that sustains resonance in the pendulum, Dung and DungVan der Pol oscillators. These predictions are confirmed with modelbased numerical simulations. A closedform approximation to the AMFM nonlinear resonance beat response of a Dung oscillator driven at its lowamplitude oscillator frequency is obtained from a solution to an associated Mathieu equation. AR time responses are found to evolve along a Mathieu equation primary resonance stability boundary. AR breakdown occurs at sweep rates just past optimal and map to a single stable point just off the Mathieu equation primary resonance stability boundary. Optimal AR sweep rates produce oscillating phase dierences with extrema near 90 degrees, allowing extended time in resonance. AR breakdown occurs when phase difference equals 180 degrees. Nonlinear resonance of the van der Pol type may play a role in the extraordinary sensitivity of the human ear.  
Summary:  The mechanism for maintaining the cochlear amplifier at its critical point is currently unknown. The possibility of openloop control of cochlear operating point, maintaining criticality on average through periodically varying damping (superregeneration) motivates a study of spontaneous otoacoustic emission (SOAE) amplitude modulation on a short (msec) time scale. An example of periodic amplitude modulation within a wide filter bandwidth is found that appears to be a beat oscillation of two SOAEs.  
Identifier:  748270123 (oclc), 3174314 (digitool), FADT3174314 (IID), fau:3682 (fedora)  
Note(s): 
by Carey Witkov. Thesis (Ph.D.)Florida Atlantic University, 2011. Includes bibliography. Electronic reproduction. Boca Raton, Fla., 2011. Mode of access: World Wide Web. 

Subject(s): 
Otoacoustic emissions Chaotic behavior in systems Nonlinear theories Pattern recognition systems 

Persistent Link to This Record:  http://purl.flvc.org/FAU/3174314  
Use and Reproduction:  http://rightsstatements.org/vocab/InC/1.0/  
Host Institution:  FAU 