Baris Baykant Alagoz

Disturbance rejection performance analyses of closed loop control systems by reference to disturbance ratio.

This study investigates disturbance rejection capacity of closed loop control systems by means of reference to disturbance ratio (RDR). The RDR analysis calculates the ratio of reference signal energy to disturbance signal energy at the system output and provides a quantitative evaluation of disturbance rejection performance of control systems on the bases of communication channel limitations. Essentially, RDR provides a straightforward analytical method for the comparison and improvement of implicit disturbance rejection capacity of closed loop control systems. Theoretical analyses demonstrate us that RDR of the negative feedback closed loop control systems are determined by energy spectral density of controller transfer function. In this manner, authors derived design criteria for specifications of disturbance rejection performances of PID and fractional order PID (FOPID) controller structures. RDR spectra are calculated for investigation of frequency dependence of disturbance rejection capacity and spectral RDR analyses are carried out for PID and FOPID controllers. For the validation of theoretical results, simulation examples are presented.

Sonic crystal acoustic switch device.

This study reports a wave-controlled sonic crystal switch device that exhibits a destructive interference-based wave to wave reverse switching effect. By applying control waves, this acoustic device, composed of a two-dimensional square lattice sonic crystal block, reduces acoustic wave transmission from input to output. The finite difference time domain simulation and experimental results confirm the wave-to-wave reverse switching effect at the peak frequencies of the second band. The proposed sonic crystal switch prototype provides a contrast rate of 86% at 11.3 kHz frequency. This wave-to-wave switching effect is useful for controlling wave propagation for smart structure applications.

Improvement of IIR filter discretization for fractional order filter by discrete stochastic optimization

Fractional calculus has many implications for the field of signal processing, particularly in filter design. Fractional order filter functions are generalization of all rational filter structures including integer-order filter functions and it provides more options in term of frequency selectivity property. This study presents application of stochastic optimization methods for the improvement of IIR filter discretization of fractional order continuous filter structures. We used results of well-known fractional order discretization methods as initial filter model and improved the amplitude response of discrete filter for a better fitting to the continuous fractional-order filters. Illustrative examples demonstrate that it is possible to further improve amplitude responses of IIR filter discretization obtained for the fractional order differentiators, the first and second order continuous fractional-order filter structures by using basic random search algorithms. Digital filter design is very essential for digital signal processing applications and findings of this paper may contribute to digital filter design field in practice.

An integer order approximation method based on stability boundary locus for fractional order derivative/integrator operators.

This paper introduces an integer order approximation method for numerical implementation of fractional order derivative/integrator operators in control systems. The proposed method is based on fitting the stability boundary locus (SBL) of fractional order derivative/integrator operators and SBL of integer order transfer functions. SBL defines a boundary in the parametric design plane of controller, which separates stable and unstable regions of a feedback control system and SBL analysis is mainly employed to graphically indicate the choice of controller parameters which result in stable operation of the feedback systems. This study reveals that the SBL curves of fractional order operators can be matched with integer order models in a limited frequency range. SBL fitting method provides straightforward solutions to obtain an integer order model approximation of fractional order operators and systems according to matching points from SBL of fractional order systems in desired frequency ranges. Thus, the proposed method can effectively deal with stability preservation problems of approximate models. Illustrative examples are given to show performance of the proposed method and results are compared with the well-known approximation methods developed for fractional order systems. The integer-order approximate modeling of fractional order PID controllers is also illustrated for control applications.

PID controller design based on second order model approximation by using stability boundary locus fitting

This study presents a model reduction method based on stability boundary locus (SBL) fitting for PID controller design problems. SBL analysis was commonly applied for controller stabilization problems. However, we use SBL analysis for the reduction of high order linear time invariant system models to second-order approximate models to facilitate analytical design of closed loop PID control systems. The PID design is implemented by a multiple pole placement strategy which enforces the control system had real poles with a desired time constant specification. Illustrative design examples are presented for the analytical PID design of high-order plant models by means of second-order SBL model approximations.

Tuning of fractional order PID with master-slave stochastic multi-parameter divergence optimization method

This paper presents master-slave stochastic multi-parameters divergence optimization (SMDO) method for tuning of fractional order proportional-integral-derivative (FOPID) controllers. Bodes ideal control loop (BICL) is used as a reference model that guides the optimization process. Master-slave SMDO performs optimization of FOPID and BICL parameters together. In the first stage called as locking, step responses of FOPID and BICL approximate each other. In the second stage called as drifting, BICL guides tuning of the FOPID towards a desired step response. One of the advantages of presented optimization approach is that both optimization of the reference model (BICL) and controller (FOPID) cooperates and the tuning of FOPID is governed by BICL in the drifting stage. Operation and performance of the proposed algorithm are demonstrated by simulation examples.

An analysis of corona field charging kinetics for polydisperse aerosol particles by considering concentration and mobility

In this paper, the kinetics of the charging process of polydisperse aerosol particles in a unipolar corona field is analysed and the effects of the particle concentration and particle mobility on the charging kinetics are investigated theoretically. An equation for time constant is derived to evaluate charging time of the particles.

Detection of RR interval alterations in ECG signals by using first order fractional filter

Sleep apnea syndrome deteriorates sleeping quality and daily performance of many individuals. This study presents utilization of fractional-order low pass filtering for the detection of RR interval alteration from electrocardiogram (ECG) signals. In the case of sleeping apnea, cardiac interbeat intervals prolong and it is viewed as an indication of obstructive sleep apnea state. The prolonged interbeat intervals manifest themselves as the decrease of R peak frequency (increase of RR intervals) in ECG signals. It results in shifting of spectral components composing R peaks towards lower frequencies in energy signal of ECG. In order to detect prolonging interbeat intervals, energy signal calculated from ECG is applied to low-pass fractional-order filter. Transition band of the low-pass filter is used as a ramp filter in order to detect frequency variations in the energy of R peaks. We compare results of the first order fractional-order and integer order low-pass filters and demonstrate that the fractional-order filter can improve the detection performance of low-pass filtering by modifying transition band slope of low-pass filters.

A note on robust stability analysis of fractional order interval systems by minimum argument vertex and edge polynomials

By using power mapping, stability analysis of fractional order polynomials was simplified to the stability analysis of expanded degree integer order polynomials in the first Riemann sheet. However, more investigation is needed for revealing properties of power mapping and demonstration of conformity of Hurwitz stability under power mapping of fractional order characteristic polynomials. Contributions of this study have two folds: Firstly, this paper demonstrates conservation of root argument and magnitude relations under power mapping of characteristic polynomials and thus substantiates validity of Hurwitz stability under power mapping of fractional order characteristic polynomials. This also ensures implications of edge theorem for fractional order interval systems. Secondly, in control engineering point of view, numerical robust stability analysis approaches based on the consideration of minimum argument roots of edge and vertex polynomials are presented. For the computer-aided design of fractional order interval control systems, the minimum argument root principle is applied for a finite set of edge and vertex polynomials, which are sampled from parametric uncertainty box. Several illustrative examples are presented to discuss effectiveness of these approaches.

Opportunities for energy efficiency in smart cities

Rapid migration from rural to urban areas leads to the emergence of urbanization and sustainability problems. Management and monitoring of resources and infrastructures are getting more important today in crowded cities. Energy consumption is increasing with the growing population and intensified in highly populated parts of cities. This increased energy consumption results in high energy demand as well as the production of more pollutants and heat in these city parts. The management of pollution and heat problems leads to an additional energy demand. Therefore, energy efficiency is becoming central challenge for urban life similar to energy efficient structuring of living organisms. Practically, all activities arranging city life require energy. For instance, job activities, transportation, security, climate, catering, entertainment, commerce etc. In this study, we review active and passive approaches, which can be utilized for improvement of energy efficiency and thus sustainability of urbanization in todays cities. We give a discussion to present a vision for future smart cities in term of improvement of energy utilization and efficiency, and relieve of environmental issues. These approaches can be helpful for future cities for relieving issues originating from population increase.