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    Parameter and order estimation from noisy step response data

    , Article IFAC Proceedings Volumes (IFAC-PapersOnline) ; 2013 , Pages 492-497 ; 14746670 (ISSN) ; 9783902823274 (ISBN) Tavakoli Kakhki, M ; Tavazoei, M. S ; Mesbahi, A ; Sharif University of Technology
    2013
    Abstract
    In this paper, two integral based methods are proposed to estimate the order and the parameters of simple fractional order models from the noisy step response data. Numerical simulation results show the efficiency of the proposed methods in the presence of the measurement noise  

    Fractional order control of thermal systems: achievability of frequency-domain requirements

    , Article Nonlinear Dynamics ; Volume 80, Issue 4 , 2015 , Pages 1773-1783 ; 0924090X (ISSN) Badri, V ; Tavazoei, M. S ; Sharif University of Technology
    Abstract
    Fractional order models have been widely used in modeling and identification of thermal systems. General model in this category is considered as the model of thermal systems in this paper, and a fractional order controller is proposed for controlling such systems. The proposed controller is a generalization for the traditional PI controllers. The parameters of this controller can be obtained by using a recently introduced tuning method which can simultaneously ensure the following three requirements: desired phase margin, desired gain crossover frequency, and flatness of the phase Bode plot at this frequency. In this paper, it is found whether simultaneously achieving the mentioned... 

    Estimation of the order and parameters of a fractional order model from a noisy step response data

    , Article Journal of Dynamic Systems, Measurement and Control, Transactions of the ASME ; Vol. 136, issue. 3 , May , 2014 ; ISSN: 00220434 Tavakoli-Kakhki, M ; Tavazoei, M. S ; Sharif University of Technology
    Abstract
    This paper deals with integral based methods to estimate the order and parameters of simple fractional order models from the extracted noisy step response data of a process. This data can be obtained from both open-loop and closed-loop tests. Numerical simulation results are presented to verify the robustness of these proposed methods in the presence of the measurement noise  

    Fractional order control of thermal systems: achievability of frequency-domain requirements

    , Article Nonlinear Dynamics ; Volume 80, Issue 4 , June , 2014 , Pages 1773-1783 ; ISSN: 0924090X Badri, V ; Tavazoei, M. S ; Sharif University of Technology
    Abstract
    Fractional order models have been widely used in modeling and identification of thermal systems. General model in this category is considered as the model of thermal systems in this paper, and a fractional order controller is proposed for controlling such systems. The proposed controller is a generalization for the traditional PI controllers. The parameters of this controller can be obtained by using a recently introduced tuning method which can simultaneously ensure the following three requirements: desired phase margin, desired gain crossover frequency, and flatness of the phase Bode plot at this frequency. In this paper, it is found whether simultaneously achieving the mentioned... 

    The effect of fractionality nature in differences between computer simulation and experimental results of a chaotic circuit

    , Article Central European Journal of Physics ; Volume 11, Issue 6 , 2013 , Pages 836-844 ; 18951082 (ISSN) Faraji, S ; Tavazoei, M. S ; Sharif University of Technology
    2013
    Abstract
    In practice, some differences are usually observed between computer simulation and experimental results of a chaotic circuit. In this paper, it is tried to obtain computer simulation results having more correlation with those obtained in practice by using more realistic models for chaotic circuits. This goal is achieved by considering the fractionality nature of electrical capacitors in the model of a chaotic circuit  

    Identification of fractional order model structures using conversion of infinite terms of a response to finite terms

    , Article ELECO 2011 - 7th International Conference on Electrical and Electronics Engineering, 1 December 2011 through 4 December 2011 ; December , 2011 , Pages II391-II395 ; 9786050102048 (ISBN) Nazarian, P ; Haeri, M ; Sharif University of Technology
    2011
    Abstract
    In this paper, a new method is proposed to determine parameters of some types of fractional order models to represent a system dynamics using its step response. The model structure is assumed to have rational commensurateorder as α = M/N . By this assumption infinite terms of the model step response is converted into finite terms limited to N. The proposed method is practically applicable on all fractional order model structures due to the order approximation imposed by the limited precisions in available computational tools  

    A fractional order model for steer-by-wire systems

    , Article IECON Proceedings (Industrial Electronics Conference) ; 2009 , Pages 4161-4166 Tahami, F ; Afshang, H ; Sharif University of Technology
    Abstract
    The steer by wire system for vehicles has attracted much attention in recent years. Steer by wire systems provide many benefits in terms of functionality and at the same time present significant challenges too. It is essential to investigate the stability of steer by wire systems using a more sophisticated model rather than common approximated models. Fractional order modeling offers a good modeling framework for complex dynamical systems involving flexible structures such as multi-mass drives. In this paper a nonlinear fractional order model for steer by wire systems is presented  

    Fractional Simplification of Linear Fractional Order Models

    , Ph.D. Dissertation Sharif University of Technology Tavakoli-Kakhki, Mahsan (Author) ; Haeri, Mohammad (Supervisor)
    Abstract
    In recent years, increasing attention has been paid to the fractional calculus as a powerful tool for more precise modeling of real world phenomena. Also, it has been shown that using this tool in designing control systems results in controllers that are more efficient in comparison with their traditional integer order counterparts. In spite of the advantages of fractional order models, the difficulties in the implementation of this type of models are still the main concern of the control system community. Clearly, as a model becomes simpler, its implementation becomes more convenient. Therefore, one way to rectify the implementation problems is to model the intended system as simple as... 

    Fractional Order Modeling and Control of Flexible Satellite

    , M.Sc. Thesis Sharif University of Technology Hosseini, Masoud (Author) ; Assadian, Nima (Supervisor)
    Abstract
    In recent decades the structure of space systems has gained more complexity due to the development of space technology. Usage of larger structure in spacecraft could cause undesirable structural vibration. mNeglecting this phenomena would affect the performance of satellite subsystems specially the accuracy of satellite control subsystem. By implementing fractional order calculus in modeling of flexible satellite, the damping effect could be modeled better than classical damping model. Also using fractional order integrator and differentiator operator will increase the performance of control subsystem. In this research, the fractional order calculus has been used in modeling and control of... 

    Proportional stabilization and closed-loop identification of an unstable fractional order process

    , Article Journal of Process Control ; Vol. 24, Issue. 5 , 2014 , pp. 542-549 ; ISSN: 09591524 Tavakoli-Kakhki, M ; Tavazoei, M. S ; Sharif University of Technology
    Abstract
    This paper deals with proportional stabilization and closed-loop step response identification of the fractional order counterparts of the unstable first order plus dead time (FOPDT) processes. At first, the necessary and sufficient condition for stabilizability of such processes by proportional controllers is found. Then, by assuming that a process of this kind has been stabilized by a proportional controller and the step response data of the closed-loop system is available, an algorithm is proposed for estimating the order and the parameters of an unstable fractional order model by using the mentioned data  

    On dynamic models of human emotion

    , Article ICEE 2012 - 20th Iranian Conference on Electrical Engineering, 15 May 2012 through 17 May 2012 ; May , 2012 , Pages 874-878 ; 9781467311489 (ISBN) Tabatabaei, S. S ; Yazdanpanah, M. J ; Tavazoei, M. S ; Karimian, A ; Sharif University of Technology
    2012
    Abstract
    This paper contains analysis and simulation of recent dynamic models, describing human emotion. The pharmacological discussions lead to a new model of drug taking, which also have a better performance for description of psychological and psychiatric phenomena. Studying the effects of the order of fractional model, obtains an advantage of the fractional order model over the integer order one  

    Speed control of servo drives with a flexible couplings using fractional order state feedback

    , Article PEDSTC 2014 - 5th Annual International Power Electronics, Drive Systems and Technologies Conference ; 2014 , p. 25-30 Tahami, F ; Moghadam, B. E ; Sharif University of Technology
    Abstract
    Using elastic couplings in servo motor drives may lead to torsional oscillations which are usually extinguished by reducing the bandwidth of the control system as a countermeasure. A high performance servo drive however needs fast dynamic characteristics. The conventional controllers, such as PI controllers, may not be able to improve the dynamic response while keeping the system stable. Fractional order modeling offers a good framework for flexible structures such as two mass servo drives. In this paper, the dynamic response and stability of two-mass servo drive is improved using a fractional order controller. The fractional order controller allows increasing the phase margin of the system... 

    Fractional order model reduction approach based on retention of the dominant dynamics: Application in IMC based tuning of FOPI and FOPID controllers

    , Article ISA Transactions ; Volume 50, Issue 3 , July , 2011 , Pages 432-442 ; 00190578 (ISSN) Tavakoli Kakhki, M ; Haeri, M ; Sharif University of Technology
    2011
    Abstract
    Fractional order PI and PID controllers are the most common fractional order controllers used in practice. In this paper, a simple analytical method is proposed for tuning the parameters of these controllers. The proposed method is useful in designing fractional order PI and PID controllers for control of complicated fractional order systems. To achieve the goal, at first a reduction technique is presented for approximating complicated fractional order models. Then, based on the obtained reduced models some analytical rules are suggested to determine the parameters of fractional order PI and PID controllers. Finally, numerical results are given to show the efficiency of the proposed tuning... 

    Simple fractional order model structures and their applications in control system design

    , Article European Journal of Control ; Volume 16, Issue 6 , 2010 , Pages 680-694 ; 09473580 (ISSN) Tavakoli Kakhki, M ; Haeri, M ; Tavazoei , M. S ; Sharif University of Technology
    2010
    Abstract
    In this paper, firstly a four-parameter fractional order model structure is introduced to approximate processes having S-shaped step responses. Three different strategies are presented in order to determine the parameters of the proposed model. In a special case where the proposed model is not satisfactory, another fractional order model structure with five free parameters is introduced to improve the model approximation. Also in this case, a procedure is provided to estimate the parameters of the introduced five-parameter model. Then, some common classical integer order control design approaches are modified or extended to their fractional order counterparts in order to incorporate the... 

    An efficient method for tuning of FOPI controllers: robustness to order variations of the plant

    , Article 26th Iranian Conference on Electrical Engineering, ICEE 2018, 8 May 2018 through 10 May 2018 ; 2018 , Pages 821-826 ; 9781538649169 (ISBN) Basiri, M. H ; Tavazoei, M. S ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2018
    Abstract
    Existence of uncertainties in the model of real-world plants can trouble the control system designer in achievement of control objectives in control of such plants. In modeling of these plants by benefiting from fractional order models, one of the most commonplace types of uncertainties is the order uncertainty. This paper deals with presenting a method for tuning fractional order PI (FOPI) controllers to be used in control of plants, modeled by fractional order transfer functions consisting of a fractional order pole in addition to a time delay, such that the control system is robust against order variations. By the proposed tuning method, values of phase margin and gain crossover frequency... 

    Free vibration analysis of sandwich conical shells with fractional viscoelastic core

    , Article Composite Structures ; Volume 214 , 2019 , Pages 62-72 ; 02638223 (ISSN) Permoon, M. R ; Shakouri, M ; Haddadpour, H ; Sharif University of Technology
    Elsevier Ltd  2019
    Abstract
    The vibration characteristics, including fundamental frequencies and loss factors, of a sandwich conical shell with constrained viscoelastic layer is presented. The mechanical properties of viscoelastic core is modeled using Zener fractional order model. The equations of motion are derived employing Donnell representation of classical shell theory and solved using Raighly-Ritz method. The results are compared with other investigations and the effects of geometric parameters including the length to radius, radius to thickness and core to facing thickness on fundamental frequencies and loss factors are studied. © 2019 Elsevier Ltd  

    Dynamic analysis of three-layer cylindrical shells with fractional viscoelastic core and functionally graded face layers

    , Article JVC/Journal of Vibration and Control ; Volume 27, Issue 23-24 , 2021 , Pages 2738-2753 ; 10775463 (ISSN) Shakouri, M ; Permoon, M. R ; Askarian, A ; Haddadpour, H ; Sharif University of Technology
    SAGE Publications Inc  2021
    Abstract
    Natural frequency and damping behavior of three-layer cylindrical shells with a viscoelastic core layer and functionally graded face layers are studied in this article. Using functionally graded face layers can reduce the stress discontinuity in the face–core interface that causes a catastrophic failure in sandwich structures. The viscoelastic layer is expressed using a fractional-order model, and the functionally graded layers are defined by a power law function. Assuming the classical shell theory for functionally graded layers and the first-order shear deformation theory for the viscoelastic core, equations of motion are derived using Lagrange’s equation and then solved via Rayleigh–Ritz... 

    Dynamic analysis of three-layer cylindrical shells with fractional viscoelastic core and functionally graded face layers

    , Article JVC/Journal of Vibration and Control ; 2020 Shakouri, M ; Permoon, M. R ; Askarian, A ; Haddadpour, H ; Sharif University of Technology
    SAGE Publications Inc  2020
    Abstract
    Natural frequency and damping behavior of three-layer cylindrical shells with a viscoelastic core layer and functionally graded face layers are studied in this article. Using functionally graded face layers can reduce the stress discontinuity in the face–core interface that causes a catastrophic failure in sandwich structures. The viscoelastic layer is expressed using a fractional-order model, and the functionally graded layers are defined by a power law function. Assuming the classical shell theory for functionally graded layers and the first-order shear deformation theory for the viscoelastic core, equations of motion are derived using Lagrange’s equation and then solved via Rayleigh–Ritz...