Phd Degree / Doktora

Now showing 1 - 3 of 3

Stability Analysis of Nonlinear Dynamical Systems With Lévy Typeperturbations
(01. Izmir Institute of Technology, 2023) Tamcı, Ege; Batal, Ahmet; Savacı, Ferit Acar
In order to model the noise in power networks, generally, normal distribution is used. However, normal distribution is not convenient in modelling noise which has sudden peaks. Instead, combination of a continuous process and a jump processes is much more suitable. With this idea in mind, in this thesis, the stability and control of two equations used in modeling power grids is analyzed, under the assumption that they are exposed to Lévy process noise which includes jumps. These equations are the swing equation and the Kuramoto Model. The swing equation is used to model the single machine infinite bus system (SMIBS). Kuramoto Model is used when a large number of generators are considered as a network of coupled oscillators with their own natural frequencies. In our stability control study in the SMIBS, the noise in the system has sudden and finite changes is assumed and therefore should be modelled with a modified tempered α-stable process obtained by adding a finite jump condition on the tempered α-stable process when α < 1. The control functions depending on the mechanical power input and damping parameters are designed in order to make the system stable in probability and exponential stable at its equilibrium point. These theoretical results are supported by numerical studies. For Kuromato model, assuming that the power network consists of two layers, namely oscillator, and control layers and that is affected with a general Lévy process which has finite jumps, functions which provide the stability of phase and frequencies are obtained, depending on oscillator and coupling strengths. In the light of the numerical studies, the control of frequency and phase synchronization up to a certain noise intensity level can be evaluated, but it is not possible beyond that level is concluded.
Development of Nonlinear Robust Control Techniques for Unmanned Aerial Vehicles
(Izmir Institute of Technology, 2015) Tanyer, İlker; Tatlıcıoğlu, Enver
In this thesis, model reference output tracking control of unmanned aircraft vehicles are aimed. The control problem is complicated due to the lack of accurate knowledge of nonlinear system dynamics and additive state-dependent nonlinear disturbancelike terms. Only the output of the vehicle is considered to be available for control design purposes. A novel robust controller is designed that ensured a global asymptotic stability result. In the design of the controller, proportional integral controller is fused with the integral of the signum of the tracking error to compensate uncertainties. Lyapunov type stability analysis are utilized to prove asymptotic convergence of the output tracking error. Extensions to optimal, adaptive and neural network controllers are also designed. Simulation and experiment results are presented to illustrate the performance of the robust controllers.
Online Time Delay Identification and Adaptive Control for General Classes of Nonlinear Systems
(Izmir Institute of Technology, 2013) Bayrak, Alper; Tatlıcıoğlu, Enver
In this dissertation, online identification of time delays is discussed. Specifically, a novel online time delay identification algorithm for nonlinear systems is presented. As a novel departure from the existing literature, in the design of the time delay identification algorithm, time delays are considered as nonlinear parameters effecting the system and nonlinear parameter estimation techniques are adopted. The presented time delay iden~ tification technique is based on a min-max optimization algorithm. The stability of the proposed time delay identification algorithm is investigated via Lyapunov-based stability analysis techniques. It is shown that the developed estimator identifies unknown time delays, upon satisfaction of a nonlinear persistent excitation condition, within a desireq precision that may be adjusted to be very small. The proposed time delay identification method is then modified to be applicable for sig~ nal processing applications. Afterwards, the control of nonlinear systems subject to state delays is considered. The control objective is to ensure output tracking of a time-varying reference trajectory while identifying unknown state delays. Two cases are considered~ First, only the state delays are assumed to be unknown in the nonlinear system dynamics, Second, linear parameters in the system dynamics are assumed to be unknown along witll unknown time delays. To meet the control objectives, the proposed time delay identifica~ tion technique is fused with a control algorithm, and in both cases, both identification anq control objectives are ensured.

Phd Degree / Doktora

Browse

Filters

Settings

Sort By

Results per page

Search Results