Isabela Roxana Birs

Bio: Isabela Roxana Birs is an academic researcher from Technical University of Cluj-Napoca. The author has contributed to research in topic(s): Control theory & Fractional calculus. The author has an hindex of 9, co-authored 51 publication(s) receiving 288 citation(s). Previous affiliations of Isabela Roxana Birs include Control Group & Ghent University.

A Survey of Recent Advances in Fractional Order Control for Time Delay Systems

Abstract: Several papers reviewing fractional order calculus in control applications have been published recently. These papers focus on general tuning procedures, especially for the fractional order proportional integral derivative controller. However, not all these tuning procedures are applicable to all kinds of processes, such as the delicate time delay systems. This motivates the need for synthesizing fractional order control applications, problems, and advances completely dedicated to time delay processes. The purpose of this paper is to provide a state of the art that can be easily used as a basis to familiarize oneself with fractional order tuning strategies targeted for time delayed processes. Solely, the most recent advances, dating from the last decade, are included in this review.

A comparison between integer and fractional order pdµ controllers for vibration suppression

Abstract: Along the years, unwanted vibrations in airplane wings have led to passenger discomfort. In this study, the airplane wing is modeled as a cantilever beam on which active vibration suppression is tested. The paper details the tuning of both integer and fractional order Proportional Derivative type controllers based on constraints imposed in the frequency domain. The controllers are experimentally validated and the results prove once more the superiority of the fractional order approach.

Discrete-time implementation and experimental validation of a fractional order PD controller for vibration suppression in airplane wings

Abstract: Vibrations in airplane wings have a negative impact on the quality and safety of a flight. For this reason, active vibration suppression techniques are of extreme importance. In this paper, a smart beam is used as a simulator for the airplane wings and a fractional order PD controller is designed for active vibration mitigation. To implement the ideal fractional order controller on the smart beam unit, its digital approximation is required. In this paper, a new continuous-to-discrete-time operator is used to obtain the discrete-time approximation of the ideal fractional order PD controller. The efficiency and flexibility, as well as some guidelines for using this new operator, are given. The numerical examples show that high accuracy of approximation is obtained and that the proposed method can be considered as a suitable solution for obtaining the digital approximation of fractional order controllers. The experimental results demonstrate that the designed controller can significantly improve the vibration suppression in smart beams.

Tuning of fractional order proportional integral/proportional derivative controllers based on existence conditions:

Abstract: Fractional order proportional integral and proportional derivative controllers are nowadays quite often used in research studies regarding the control of various types of processes, with several pa...

Mathematical modelling with experimental validation of viscoelastic properties in non-Newtonian fluids.

Abstract: The paper proposes a mathematical framework for the use of fractional-order impedance models to capture fluid mechanics properties in frequency-domain experimental datasets. An overview of non-Newtonian (NN) fluid classification is given as to motivate the use of fractional-order models as natural solutions to capture fluid dynamics. Four classes of fluids are tested: oil, sugar, detergent and liquid soap. Three nonlinear identification methods are used to fit the model: nonlinear least squares, genetic algorithms and particle swarm optimization. The model identification results obtained from experimental datasets suggest the proposed model is useful to characterize various degree of viscoelasticity in NN fluids. The advantage of the proposed model is that it is compact, while capturing the fluid properties and can be identified in real-time for further use in prediction or control applications. This article is part of the theme issue 'Advanced materials modelling via fractional calculus: challenges and perspectives'.

I and i

Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

Formulas For Natural Frequency And Mode Shape

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Non-newtonian fluids.

Abstract: The Viscosity can be imagined as the force that should be applied to a layer of fluid belonging to the plane fixed to the velocity of the layer placed at a fixed distance. For example a fluid flowing in a tube at different speeds: the minimum speed is in the edge of the section (due to friction) and the maximum speed is at the center. The viscosity in this example is that pressure which is exerted on the wall allows a constant speed on the whole section.

Applications of Fractional Calculus

Abstract: Explicit formula and graphs of few special functions are derived in the paper on the basis of various definitions of various fractional derivatives and various fractional integrals. Their applications are also reviewed in the paper.

Fractional-order viscoelasticity in one-dimensional blood flow models

Abstract: In this work we employ integer- and fractional-order viscoelastic models in a one-dimensional blood flow solver, and study their behavior by presenting an in-silico study on a large patient-specific cranial network. The use of fractional-order models is motivated by recent experimental studies indicating that such models provide a new flexible alternative to fitting biological tissue data. This is attributed to their inherent ability to control the interplay between elastic energy storage and viscous dissipation by tuning a single parameter, the fractional order α, as well as to account for a continuous viscoelastic relaxation spectrum. We perform simulations using four viscoelastic parameter data-sets aiming to compare different viscoelastic models and highlight the important role played by the fractional order. Moreover, we carry out a detailed global stochastic sensitivity analysis study to quantify uncertainties of the input parameters that define each wall model. Our results confirm that the effect of fractional models on hemodynamics is primarily controlled by the fractional order, which affects pressure wave propagation by introducing viscoelastic dissipation in the system.