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Mohammad Saleh Tavazoei - One of the best experts on this subject based on the ideXlab platform.

  • On time-constant robust tuning of fractional order proportional derivative controllers
    IEEE CAA Journal of Automatica Sinica, 2019
    Co-Authors: Vahid Badri, Mohammad Saleh Tavazoei
    Abstract:

    This paper deals with analyzing a newly introduced method for tuning of fractional order [ proportional derivative ] ( FO[ PD ] ) controllers to be used in motion control. By using this tuning method, not only the phase margin and gain Crossover Frequency are adjustable, but also robustness to variations in the plant time-constant is guaranteed. Conditions on the values of control specifications ( desired phase margin and gain Crossover Frequency ) for solution existence in this tuning method are found. Also, the number of solutions is analytically determined in this study. Moreover, experimental verifications are presented to indicate the applicability of the obtained results.

  • On Robust Control of Fractional Order Plants: Invariant Phase Margin
    Journal of Computational and Nonlinear Dynamics, 2015
    Co-Authors: Mohammad Hossein Basiri, Mohammad Saleh Tavazoei
    Abstract:

    Recently, a robust controller has been proposed to be used in control of plants with large uncertainty in location of one of their poles. By using this controller, not only the phase margin and gain Crossover Frequency are adjustable for the nominal case but also the phase margin remains constant, notwithstanding the variations in location of the uncertain pole of the plant. In this paper, the tuning rule of the aforementioned controller is extended such that it can be applied in control of plants modeled by fractional order models. Numerical examples are provided to show the effectiveness of the tuned controller.

  • Achievable Performance Region for a Fractional-Order Proportional and Derivative Motion Controller
    IEEE Transactions on Industrial Electronics, 2015
    Co-Authors: Vahid Badri, Mohammad Saleh Tavazoei
    Abstract:

    In recent years, design and tuning of fractional-order controllers for use in motion control have attracted much attention. This paper deals with one of the interesting methods that have been recently proposed for tuning fractional-order proportional and derivative (FOPD) motion controllers. The FOPD controller tuned based on the considered method results in simultaneously meeting the desired phase margin, the desired gain Crossover Frequency, and the flatness of the phase Bode plot at such a Frequency. Since, in this tuning method, the derivative parameter and order are determined in a graphical way, in the first view, it is not clear for which pairs of phase margin and gain Crossover Frequency an FOPD controller can be found to satisfy the mentioned specifications. In this paper, necessary and sufficient conditions are presented via an analytical approach to check the solution existence of the considered tuning method in both cases of absence and presence of time delay in feedback loop. Furthermore, the uniqueness of the controller parameters obtained from the method is investigated. Moreover, some numerical and experimental examples are presented to confirm the analytical results of this paper.

  • On tuning fractional order [proportional-derivative] controllers for a class of fractional order systems
    Automatica, 2013
    Co-Authors: Vahid Badri, Mohammad Saleh Tavazoei
    Abstract:

    Abstract This paper deals with a method recently proposed for tuning fractional order [proportional–derivative] (FO-[PD]) controllers. Using this tuning method, the tuned FO-[PD] controller can ensure the desired phase margin, the desired gain Crossover Frequency, and the flatness of the phase Bode plot at such a Frequency. In the present paper, the achievable region of this tuning method in the gain Crossover Frequency–phase margin plane is obtained analytically. Also, the continuity of this region and uniqueness of the tuned parameters are investigated. Moreover, the achievable region of the aforementioned tuning method in the presence of time delay in the feedback loop is found.

Vahid Badri - One of the best experts on this subject based on the ideXlab platform.

  • On time-constant robust tuning of fractional order proportional derivative controllers
    IEEE CAA Journal of Automatica Sinica, 2019
    Co-Authors: Vahid Badri, Mohammad Saleh Tavazoei
    Abstract:

    This paper deals with analyzing a newly introduced method for tuning of fractional order [ proportional derivative ] ( FO[ PD ] ) controllers to be used in motion control. By using this tuning method, not only the phase margin and gain Crossover Frequency are adjustable, but also robustness to variations in the plant time-constant is guaranteed. Conditions on the values of control specifications ( desired phase margin and gain Crossover Frequency ) for solution existence in this tuning method are found. Also, the number of solutions is analytically determined in this study. Moreover, experimental verifications are presented to indicate the applicability of the obtained results.

  • Achievable Performance Region for a Fractional-Order Proportional and Derivative Motion Controller
    IEEE Transactions on Industrial Electronics, 2015
    Co-Authors: Vahid Badri, Mohammad Saleh Tavazoei
    Abstract:

    In recent years, design and tuning of fractional-order controllers for use in motion control have attracted much attention. This paper deals with one of the interesting methods that have been recently proposed for tuning fractional-order proportional and derivative (FOPD) motion controllers. The FOPD controller tuned based on the considered method results in simultaneously meeting the desired phase margin, the desired gain Crossover Frequency, and the flatness of the phase Bode plot at such a Frequency. Since, in this tuning method, the derivative parameter and order are determined in a graphical way, in the first view, it is not clear for which pairs of phase margin and gain Crossover Frequency an FOPD controller can be found to satisfy the mentioned specifications. In this paper, necessary and sufficient conditions are presented via an analytical approach to check the solution existence of the considered tuning method in both cases of absence and presence of time delay in feedback loop. Furthermore, the uniqueness of the controller parameters obtained from the method is investigated. Moreover, some numerical and experimental examples are presented to confirm the analytical results of this paper.

  • On tuning fractional order [proportional-derivative] controllers for a class of fractional order systems
    Automatica, 2013
    Co-Authors: Vahid Badri, Mohammad Saleh Tavazoei
    Abstract:

    Abstract This paper deals with a method recently proposed for tuning fractional order [proportional–derivative] (FO-[PD]) controllers. Using this tuning method, the tuned FO-[PD] controller can ensure the desired phase margin, the desired gain Crossover Frequency, and the flatness of the phase Bode plot at such a Frequency. In the present paper, the achievable region of this tuning method in the gain Crossover Frequency–phase margin plane is obtained analytically. Also, the continuity of this region and uniqueness of the tuned parameters are investigated. Moreover, the achievable region of the aforementioned tuning method in the presence of time delay in the feedback loop is found.

Dragan Maksimovic - One of the best experts on this subject based on the ideXlab platform.

  • an autotuning digital controller for dc dc power converters based on online Frequency response measurement
    IEEE Transactions on Power Electronics, 2009
    Co-Authors: Mariko Shirazi, Regan Zane, Dragan Maksimovic
    Abstract:

    This paper describes a hardware-description-language-coded autotuning algorithm for digital PID-controlled DC-DC power converters based on online Frequency-response measurement. The algorithm determines the PID controller parameters required to maximize the closed-loop bandwidth of the feedback control system while maintaining user-specified stability margins and integral-based no-limit-cycling criteria, as well as ensuring single-Crossover-Frequency operation and sufficiently high loop gain magnitude at low frequencies. Experimental results are provided for five different pulsewidth-modulated DC-DC converters, including a well-damped synchronous buck, a lightly damped synchronous buck with and without a poorly damped input filter, a boost operating in continuous-conduction mode, and a boost operating in discontinuous-conduction mode.

  • an online stability margin monitor for digitally controlled switched mode power supplies
    IEEE Transactions on Power Electronics, 2009
    Co-Authors: J. Morroni, Regan Zane, Dragan Maksimovic
    Abstract:

    This paper presents a practical injection-based method for continuous monitoring of the Crossover Frequency and phase margin in digitally controlled switched-mode power supplies (SMPS). The proposed approach is derived from Middlebrook's loop-gain measurement technique, adapted to a digital controller implementation. A digital square-wave signal is injected into the feedback loop and the injection signal Frequency is adjusted while monitoring loop signals to obtain the system Crossover Frequency and phase margin online, i.e., during normal closed loop SMPS operation. The approach does not require open loop or steady-state SMPS operation and is capable of convergence in the presence of load transients or other disturbances. A method for designing the stability margin monitor, based on small-signal models derived using an envelope modeling approach, is also presented. Experimental results are given for multiple power stage configurations demonstrating close matches between monitored and expected Crossover frequencies and phase margins.

  • design and implementation of an adaptive tuning system based on desired phase margin for digitally controlled dc dc converters
    IEEE Transactions on Power Electronics, 2009
    Co-Authors: J. Morroni, Regan Zane, Dragan Maksimovic
    Abstract:

    This letter presents an online adaptive tuning technique for digitally controlled switched-mode power supplies (SMPS). The approach is based on continuous monitoring of the system Crossover Frequency and phase margin, followed by a multi-input-multi-output (MIMO) control loop that continuously and concurrently tunes the compensator parameters to meet Crossover Frequency and phase margin targets. Continuous stability margin monitoring is achieved by injecting a small digital square-wave signal between the digital compensator and the digital pulsewidth modulator. The MIMO loop adaptively adjusts the compensator parameters to minimize the error between the desired and measured Crossover Frequency and phase margin. Small-signal models are derived, and the MIMO control loop is designed to achieve stability and performance over a wide range of operating conditions. Using modest hardware resources, the proposed approach enables adaptive tuning during normal SMPS operation. Experimental results demonstrating system functionality are presented for a synchronous buck SMPS.

  • adaptive tuning of digitally controlled switched mode power supplies based on desired phase margin
    Power Electronics Specialists Conference, 2008
    Co-Authors: J. Morroni, Regan Zane, Dragan Maksimovic
    Abstract:

    This paper presents an online adaptive tuning technique for digitally controlled switched-mode power supplies (SMPS). The approach is based on continuous monitoring of the system Crossover Frequency and phase margin, followed by a multi-input multi-output (MIMO) control loop that continuously and concurrently tunes the compensator parameters to meet Crossover Frequency and phase margin targets. Small-signal models are derived and the MIMO control loop is designed to achieve stability and performance over a wide range of operating conditions. Using modest hardware resources, the proposed approach enables adaptive tuning during normal closed-loop SMPS operation. Experimental results demonstrating system functionality are presented for a synchronous buck SMPS.

  • An online phase margin monitor for digitally controlled switched-mode power supplies
    2008 IEEE Power Electronics Specialists Conference, 2008
    Co-Authors: J. Morroni, Regan Zane, Dragan Maksimovic
    Abstract:

    This paper presents a practical injection-based method for continuous monitoring of the Crossover Frequency and phase margin in digitally controlled switched-mode power supplies (SMPS). The proposed approach is based on Middlebrook's loop-gain measurement technique, adapted to digital controller implementation. A digital square-wave signal is injected in the loop, and the injection signal Frequency is adjusted while monitoring loop signals to obtain the system Crossover Frequency and phase margin online, i.e., during normal SMPS operation. The approach does not require open loop or steady-state SMPS operation and is capable of convergence in the presence of load transients or other disturbances. Experimental results are presented for various power stage configurations demonstrating close matches between monitored and expected Crossover frequencies and phase margins.

Yangquan Chen - One of the best experts on this subject based on the ideXlab platform.

  • ON AUTO-TUNING OF FRACTIONAL ORDER PIλDµ CONTROLLERS
    2015
    Co-Authors: Concepción A. Monje, Yangquan Chen, Blas M. Vinagre, Vicente Feliu, Escuela De Ingenierías Industriales, Extremadura Badajoz Spain
    Abstract:

    Abstract: In this paper, a method for the auto-tuning of fractional order PIλDµ controllers using relay feedback tests is proposed. A design method for this kind of controllers is discussed, based on the magnitude and phase measurement of the plant to be controlled from relay feedback tests at a Frequency of interest. Simple relationships among the parameters of the fractional controller are established and specifications such as the static error constant (kss), phase margin (ϕm) and gain Crossover Frequency (ωc) can be fulfilled, with a robustness argument by inspecting the flatness of phase Bode plot of the controller. An illustrative example of application is presented to show the reliability and effectiveness of the method

  • time constant robust analysis of a fractional order proportional derivative controller
    Iet Control Theory and Applications, 2011
    Co-Authors: Y Jin, Yangquan Chen, Dingyu Xue
    Abstract:

    This study discusses fractional order [proportional derivative] (FO[PD]) controller tuning rules for robustness motion control systems. According to the proposed method, the controller is designed simultaneously satisfying the robustness property with respect to time-constant variation and the desired phase margin criteria. In this study, the authors focus on the first-order plus time delay model with an integrator. A systematic tuning rule is developed for the FO[PD] controller. Numerical computation of the tuning formulae and the relationship between design specifications and design parameters are both discussed. For simplifying the computation and achieving online tuning, the Crossover Frequency has been discussed. Experimental results are included to validate the proposed tuning method.

  • a fractional order proportional and derivative fopd motion controller tuning rule and experiments
    IEEE Transactions on Control Systems and Technology, 2010
    Co-Authors: Ying Luo, Yangquan Chen
    Abstract:

    In recent years, it is remarkable to see the increasing number of studies related to the theory and application of fractional order controller (FOC), specially PI ? D ? controller, in many areas of science and engineering. Research activities are focused on developing new analysis and design methods for fractional order controllers as an extension of classical control theory. In this paper, a new tuning method for fractional order proportional and derivative (PD ?) or FO-PD controller is proposed for a class of typical second-order plants. The tuned FO-PD controller can ensure that the given gain Crossover Frequency and phase margin are fulfilled, and furthermore, the phase derivative w. r. t. the Frequency is zero, i.e., the phase Bode plot is flat at the given gain Crossover Frequency. Consequently, the closed-loop system is robust to gain variations. The FOC design method proposed in the paper is practical and simple to apply. Simulation and experimental results show that the closed-loop system can achieve favorable dynamic performance and robustness.

  • a fractional order proportional and derivative fopd controller tuning algorithm
    Chinese Control and Decision Conference, 2008
    Co-Authors: Hongsheng Li, Yangquan Chen
    Abstract:

    In recent years, it is remarkable to see the increasing number of studies related to the theory and application of fractional order controller (FOC), especially PID controller, in many areas of science and engineering. Research activities are focused on developing new analysis and design methods for fractional order controllers as an extension of classical control theory. In this paper, a new tuning method for fractional order proportional and derivative (PD) or FOPD controller is proposed for a class of typical second-order plants. The tuned PD controller can ensure that the given gain Crossover Frequency and phase margin are fulfilled, and furthermore the phase derivative w.r.t. the Frequency is zero, i.e., phase bode plot is flat, at the given gain Crossover Frequency so that the closed-loop system is robust to gain variations and the step response exhibits an iso-damping property. The FOC design method proposed in the paper is practical and simple to apply. Simulation results show that the closed-loop system can achieve favorable dynamic performance and robustness.

Ronald G Larson - One of the best experts on this subject based on the ideXlab platform.

  • determining the dilution exponent for entangled 1 4 polybutadienes using blends of near monodisperse star with unentangled low molecular weight linear polymers
    Macromolecules, 2019
    Co-Authors: Ryan Hall, Beomgoo Kang, Taihyun Chang, David C Venerus, Nikos Hadjichristidis, Jimmy W Mays, Ronald G Larson
    Abstract:

    We determine experimentally the “dilution exponent” α for entangled polymers from the scaling of terminal Crossover Frequency with entanglement density from the linear rheology of three 1,4-polybutadiene star polymers that are blended with low-molecular-weight, unentangled linear 1,4-polybutadiene at various star volume fractions, ϕs. Assuming that the rheology of monodisperse stars depends solely on the plateau modulus GN(ϕs) ∝ ϕs1+α, the number of entanglements per chain Me(ϕs) ∝ ϕs–α, and the tube-segment frictional Rouse time τe(ϕs) ∝ ϕs–2α, we show that only an α = 1 scaling superposes the Me(ϕs) dependence of the terminal Crossover Frequency ωx,t of the blends with those of pure stars, not α = 4/3. This is the first determination of α for star polymers that does not rely on any particular tube model implementation. We also show that a generalized tube model, the “Hierarchical model”, using the “Das” parameter set with α = 1 reasonably predicts the rheological data of the melts and blends featured in...

  • Determining the Dilution Exponent for Entangled 1,4-Polybutadienes Using Blends of Near-Monodisperse Star with Unentangled, Low Molecular Weight Linear Polymers
    2019
    Co-Authors: Ryan Hall, Beomgoo Kang, Taihyun Chang, David C Venerus, Nikos Hadjichristidis, Sanghoon Lee, Jimmy Mays, Ronald G Larson
    Abstract:

    We determine experimentally the “dilution exponent” α for entangled polymers from the scaling of terminal Crossover Frequency with entanglement density from the linear rheology of three 1,4-polybutadiene star polymers that are blended with low-molecular-weight, unentangled linear 1,4-polybutadiene at various star volume fractions, ϕs. Assuming that the rheology of monodisperse stars depends solely on the plateau modulus GN(ϕs) ∝ ϕs1+α, the number of entanglements per chain Me(ϕs) ∝ ϕs–α, and the tube-segment frictional Rouse time τe(ϕs) ∝ ϕs–2α, we show that only an α = 1 scaling superposes the Me(ϕs) dependence of the terminal Crossover Frequency ωx,t of the blends with those of pure stars, not α = 4/3. This is the first determination of α for star polymers that does not rely on any particular tube model implementation. We also show that a generalized tube model, the “Hierarchical model”, using the “Das” parameter set with α = 1 reasonably predicts the rheological data of the melts and blends featured in this paper