Browsing by Subject "Chaotic dynamics"
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Item Open Access Nanomechanical buckling for applications in nonlinear dynamics(Bilkent University, 2021-07) Demiralp, BerkeThere has not been enough attention on post buckling behavior at nano scale even though it reveals rich nonlinear and chaotic dynamics and has potential to be used on cutting edge sensing, actuation, computation and communication applications. Here, full motion of the nanomechanical buckling, starting from un-buckled position to large deformations at post buckling regime has been precisely measured with error bars of ±7 nm for large deformation regime and ±2.8 nm for √ initial bending, with a noise floor of 38.5 pm/ Hz. Line mode of SEM is used for deflection detection which uses secondary electrons collected from sample and relevant code is developed for data processing. Initial bending, initial buckling and inflection point are well defined which can help us to understand transition to post buckling regime and development of sensors and actuators. Additionally, one well oscillation, double well oscillation and chaotic trajectories are investi-gated using the system as forced double well oscillator. Trajectory plotting is performed with an image processing code which benefits from contrast difference of the device and environment. A new region within double well oscillation regime is observed where motion converts from one well oscillation to double well oscilla-tion which could be a candidate on mechanical computation and communication applications. Also, a preliminary design for synchronized chaos experiments using the same buckling platform is developed. Finally, an optomechanical experimental setup and chip is built for measure-ment of one or multiple NEMS beams. Fiber optic techniques are used for exper-imental setup and grating couplers, ring/racetrack resonators are develoxper-imental setup and grating couplers, ring/racetrack resonators are developed for beam measurements. Critical couplings on multiple devices are observed.Item Open Access Observer-based control of a class of chaotic systems(Elsevier, 2001) Solak, E.; Morgül, O.; Ersoy, U.We consider the control of a class of chaotic systems, which covers the forced chaotic oscillators. We focus on two control problems. The first one is to change the dynamics of the system to a new one which exhibits a desired behavior, and the second one is the tracking problem, i.e., to force the solutions of the chaotic system to track a given trajectory. To solve these problems we use observers which could be used to estimate the unknown states of the system to be controlled. We apply the proposed method to the control of Duffing equation and the Van der Pol oscillator and present some simulation results. © 2001 Elsevier Science B.V.Item Open Access A switching synchronization scheme for a class of chaotic systems(Elsevier, 2002) Morgül, Ö.; Akgül, M.In this Letter, we propose an observer-based synchronization scheme for a class of chaotic systems. This class of systems are given by piecewise-linear dynamics. By using some properties of such systems, we give a procedure to construct the gain of the observer. We prove various stability results and comment on the robustness of the proposed scheme. We also present some simulation results. © 2002 Elsevier Science B.V. All rights reserved.