Celaleddin Yeroglu

Classical controller design techniques for fractional order case

This paper presents some classical controller design techniques for the fractional order case. New robust lag, lag-lead, PI controller design methods for control systems with a fractional order interval transfer function (FOITF) are proposed using classical design methods with the Bode envelopes of the FOITF. These controllers satisfy the robust performance specifications of the fractional order interval plant. In order to design a classical PID controller, an optimization technique based on fractional order reference model is used. PID controller parameters are obtained using the least squares optimization method. Different PID controller parameters that satisfy stability have been obtained for the same plant.

A numerical investigation for robust stability of fractional-order uncertain systems

This study presents numerical methods for robust stability analysis of closed loop control systems with parameter uncertainty. Methods are based on scan sampling of interval characteristic polynomials from the hypercube of parameter space. Exposed-edge polynomial sampling is used to reduce the computational complexity of robust stability analysis. Computer experiments are used for demonstration of the proposed robust stability test procedures.

A stochastic multi-parameters divergence method for online auto-tuning of fractional order PID controllers

Abstract This paper presents a stochastic multi-parameters divergence method for online parameter optimization of fractional-order proportional–integral–derivative (PID) controllers. The method is used for auto-tuning without the need for exact mathematical plant model and it is applicable to diverse plant transfer functions. The proposed controller tuning algorithm is capable of adaptively responding to parameter fluctuations and model uncertainties in real systems. Adaptation skill enhances controller performance for real-time applications. Simulations and experimental observations are carried on a prototype helicopter model to confirm the performance improvements obtained by the online auto-tuning of fractional-order PID structure in laboratory conditions.

Design of Robust PI Controller for Vehicle Suspension System

This paper deals with the design of a robust PI controller for a vehicle suspension system. A method, which is related to computation of all stabilizing PI controllers, is applied to the vehicle suspension system in order to obtain optimum control between passenger comfort and driving performance. The PI controller parameters are calculated by plotting the stability boundary locus in the (k p , k i )-plane and illustrative results are presented. In reality, like all physical systems, the vehicle suspension system parameters contain uncertainty. Thus, the proposed method is also used to compute all the parameters of a PI controller that stabilize a vehicle suspension system with uncertain parameters.

Optimal fractional order PID design via Tabu Search based algorithm

This paper presents an optimization method based on the Tabu Search Algorithm (TSA) to design a Fractional-Order Proportional-Integral-Derivative (FOPID) controller. All parameter computations of the FOPID employ random initial conditions, using the proposed optimization method. Illustrative examples demonstrate the performance of the proposed FOPID controller design method.

Investigation of robust stability of fractional order multilinear affine systems: 2q-convex parpolygon approach

Abstract This paper discusses the robust stability problem of fractional order systems with the multi-linear affine uncertainty structure. The 2 q -convex parpolygon approach has been extended to compute the value set of the fractional order uncertain system and to investigate the robust stability via zero exclusion principle. An illustrative example is included for fractional order multi-linear affine system to present the advantages of the 2 q -convex parpolygon approach over classical value set computation methods in the stability investigation.

Design of PI and PID Controllers for Fractional Order Time Delay Systems

Abstract This paper deals with the computation of rational approximations of fractional derivatives and/or integrals. All rational approximations for fractional order of 0.1, 0.2,…, 0.9 are obtained using continued fraction expansion (CFE) method. Extension of the stability boundary locus approach to control systems with a fractional order transfer function is given for the computation of stabilizing PI and PID controllers using continuous approximations of fractional orders. Numerical examples are provided to illustrate the results and to show the effect of the order of approximation on the stability region.

Investigation of the characteristics of dielectric barrier discharge in transition region

In the paper, we study the dielectric barrier discharge (DBD) occurring in a metal?insulator?gas?insulator?metal system. We encounter these kinds of discharges in ozonator-type reactors used in gas electrochemistry. The experiments are done in air medium when the gap width value is 580??m and the pressure is in the interval of 1?100?mbar. The schematic diagram of the experimental mechanism and the drawing methods of the characteristics are given, and it is determined that the barrier discharge has an impulse character. Experimentally, we determine that the voltage?current (v?i) and voltage?charge (v?q) characteristics of the discharge are linear for the case of (pl) (pl)cr, and these cases are explained theoretically. Furthermore, the determination method of the ratio of the fading voltage depending on the width of the steps of the experimental v?i characteristic to the inception voltage is given in this paper.

Computation of the value set of fractional order uncertain polynomials: A 2q convex parpolygonal approach

Fractional order models are frequently used to describe real processes especially in the last decades. Uncertainties in this processes mostly yield to some bad results and brings computational complexity. So this comes up as a new problem waiting to be analyzed. In this paper, a 2q convex parpolygonal approach is applied to the computation of value set of fractional order uncertain polynomials to reduce the computational complexity. The analysis steps are given and the results are shown via graphical examples. It is shown that this approach is an effective way of analyzing fractional order uncertain polynomials and can be used to investigate the stability.

Development of a toolbox for frequency response analysis of fractional order control systems

The paper presents development of a program in the MATLAB for the analysis of Fractional Order Control Systems (FOCS). Using this program, frequency response plots such as Nyquist plot, Bode plots and Nichols plot can be obtained. Gain and phase margins of FOCS can be estimated and suitable controller can be designed for the related control system.