Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 126 for “"Limit Cycle"”.
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Identification of Thermoacoustic Dynamics Exhibiting Limit Cycle Behavior
… of thermoacoustic dynamics that exhibit limit cycle behavior is needed to gain a better intuitive feel of the system, to design complex control strategies, and to validate modeling efforts. Limit cycle oscillations arise in thermoacoustic systems due to the coupling between a nonlinear …
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Synchronization in Coupled Opto-thermal Silicon MEMS Limit Cycle Oscillators
… oscillators exhibit nonlinear phenomena such as limit cycle oscillations, self-synchronization, and frequency entrainment to an external drive. In this work, we chart the behavior of silicon MEMS oscillators that are nominally 40 µm long and 205 nm thick, mechanically coupled, and opto-thermally …
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Limit Cycle PIO Analysis With Simultaneously Acting Multiple Asymmetric Saturation
… with nonlinearities including stick position limiting, elevator deflection limiting, and elevator rate limiting. These analyses involve the use of dual input describing functions which enable the prediction of frequency, amplitude, and mean point of oscillation.
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A formulation of nonlinear limit cycle oscillation problems in aircraft flutter
Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1993.
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Time Spectral Adjoint Based Design for Flutter and Limit Cycle Oscillation Suppression
… does not overlap with regions of flutter or Limit Cycle Oscillation (LCO). A quick assessment of these dynamic aeroelastic for various design candidates is key to successful design. Flutter based design requires the sensitivity of flutter parameters to be known with the respect of design …
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Prediction of Limit Cycle Oscillation in an Aeroelastic System using Nonlinear Normal Modes
… flutter analysis method capable of predicting limit cycle oscillation in aeroelastic systems. A review is conducted of analysis methods and experiments that have attempted to better understand and model limit cycle oscillation (LCO). The recently developed method of nonlinear normal modes (NNM) …
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Suppression of limit cycle oscillations in an aeroelastic system using robust and adaptive control
… the purpose of control. First the existence of limit cycle oscillations and domain of stability (attraction) of prototypical aeroelastic wing sections with pitch structural nonlinearity using the describing function method is determined. The model includes unsteady aerodynamics based on …
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Robust and Adaptive Nonlinear Control of Limit Cycle Oscillations in UAVs Using Synthetic Jet Actuators
<p>Limit cycle oscillations (LCO), also known as utter, cause significant challenges in fight control of unmanned aerial vehicles (UAVs), and could potentially lead to structural damage and catastrophic failures. LCO can be described as vibrational motions in the pitching and plunging displacements …
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Numerical Study in Wind Energy Extraction from Controlled Limit-Cycle Oscillations in Modified Glauert Airfoil
… Glauert (MG) airfoil experiencing aeroelastic limit cycle oscillation (LCO) from which energy may be extracted. Synthetic jet actuators (SJA)s are used along with the unique geometry of the MG airfoil to control flow separation and amplify the LCO and energy generation potential of the system. …
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Development of Reduced-Order Flame Models for Prediction of Combustion Instability
… in the combustion chamber. The thermoacoustic limit cycle is generated by the unsteady heat release dynamics coupled to the combustor acoustics. In this dissertation, we focused on reduced-order modeling of the dynamics of a laminar premixed flame. From first principles of combustion dynamics, …
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Pilot Variability During Pilot-Induced Oscillation
… after a PIO. Often, PIO''s can be explained by limit cycles occurring in a non-linear system where the non-linearities cause a sustained, constant amplitude oscillation. The primary instigators in such a PIO are usually a non-linear element (i.e. rate limit saturation) and a trigger event (i.e. …
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Suppression of Limit Cycles in Digital Filters
The injection of randan dither to suppress limit cycle oscillations in second-order direct form digital filter sections is discussed. Three types of dither signal are used: uniformly distributed random dither, binary randan dither and bandstop dither. All the limit cycles in the second-order filter …
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Robust Nonlinear Estimation and Control Applications using Synthetic Jet Actuators
<p>Limit cycle oscillations (LCO), also known as utter, cause significant challenges in flight control of small unmanned aerial vehicles (SUAVs), and could potentially lead to structural damage and catastrophic failures. LCO can be described as vibrational motions in the rocking, pitching and …
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Fast prediction of transonic aeroelasticity using computational fluid dynamics
… include the transonic flutter dip and limit cycle oscillations. An intensive research effort is underway to account for aerodynamic nonlinearity at a practical computational cost.To achieve this a large reduction in the numbers of degrees of freedoms is required and leads to the …
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Application of Bifurcation Theory to Subsynchronous Resonance in Power Systems
… system oscillates subsynchronously with a small limit-cycle attractor. As the compensation level increases, the limit cycle grows and then loses stability via a secondary Hopf bifurcation, resulting in the creation of a two-period quasiperiodic subsynchronous oscillation, a two-torus attractor. …
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A dynamo case study of Mercury, and the early orbital and thermal evolution of the Moon
… mechanism. We find an alternative mechanism, a limit cycle, that can reduce angular momentum over a much broader parameter range. We couple the orbital evolution with lunar magma ocean solidification to assess the mutual effects of orbital processes and the Moon's thermal profile on each other. …
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A study of synchronization of nonlinear oscillators: Application to epileptic seizures
… is a dimension reduction technique for a stable limit cycle, is applied to the system. The results propose a possible mechanism for the initiation of the drug-induced seizure as a result of a bifurcation. In the last part, a theoretical framework is developed to obtain the statistics for the …
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Investigation of slow oscillations in blood pressure
… short-term control of blood pressure, and soft-limiting nonlinearities inherent in this loop, are thought to give rise to a slow limit cycle oscillation in blood pressure at 0.1 Hz in the human. Measurement of the strength of this slow oscillation has been proposed as the basis for the …
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Modeling and design of digital current-mode constant on-time control
… the voltage regulator module. One issue is the limit cycle oscillation problem caused by the quantization effect from the ADC and DPWM of the digital control chip. Another issue is the delay problem coming from the sample-hold effect. In this thesis, the modeling, analysis and design methodology …
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Composing motion primitives under disturbances: a switched systems approach
… the capability to reason about these dynamic limitations. This dissertation exploits and expands on existing switched system's literature to encode these dynamic limitations as an upper bound on the frequency of switching among the motion primitives. These easy to implement constraints on the …
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