Search for: closed-loop-systems
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    Inferential closed-loop control of particle size distribution for styrene emulsion polymerization

    , Article Chemical Engineering Science ; Volume 63, Issue 9 , 2008 , Pages 2378-2390 ; 00092509 (ISSN) Abedini, H ; Shahrokhi, M ; Sharif University of Technology
    In this work, a new control strategy for controlling the particle size distribution (PSD) in emulsion polymerization has been proposed. It is shown that the desired PSD can be achieved by controlling the free surfactant concentration which in turn can be done by manipulating the surfactant feed rate. Simulation results show that the closed-loop control of free surfactant concentration results in a better control of PSD compared to open-loop control strategy, in presence of model mismatch and disturbances. Since the on-line measuring of ionic free surfactant concentration is difficult, conductivity which is related to it is measured instead and used for control purposes. The closed-loop... 

    Stability and performance preserving controller order reduction via Youla parameterization and lmis

    , Article 2003 10th IEEE International Conference on Electronics, Circuits and Systems, ICECS2003, Sharjah, 14 December 2003 through 17 December 2003 ; Volume 2 , 2003 , Pages 663-666 ; 0780381637 (ISBN); 9780780381636 (ISBN) Amirgar, R ; Sadati, N ; Sharif University of Technology
    This paper develops a stability and performance preserving controller order reduction method for linear time-invariant continuous-time single-input, single-output systems. In this method, the error between the complementary sensitivity functions of the nominal closed-loop system and closed-loop system using the reduced-order controller is converted to a frequency-weighted error between the Youla parameters of the full-order and reduced-order controllers and then the H∞norm of this error, subject to a set of linear matrix inequality constraints, is minimized. The main ideas of order reduction and stability preservation are contained in the constraints of the optimization problem. However,... 

    Robust adaptive backstepping control of uncertain lorenz system [electronic resource]

    , Article Journal of American Institute of Physics ; 2010, Vol. 20, pp. 1-5 Nejat Pishkenari, H. (Hossein) ; Jalili, Nader ; Mahboobi, Seyed Hanif ; Alasty, Aria ; Meghdari, Ali ; Sharif University of Technology
    In this paper, a novel robust adaptive control method is proposed for controlling the Lorenz chaotic attractor. A new backstepping controller for the Lorenz system based on the Lyapunov stability theorem is proposed to overcome the singularity problem that appeared in using the typical backstepping control method. By exploiting the property of the system, the resulting controller is shown to be singularity free and the closed loop system is globally stable. Due to unavailability of system states measurement in practice, the controller is selected such that only one system state is needed. To overcome the problem of parameter uncertainty, an additional term to Lyapunov function is added and... 

    CRA based Control of non-minimum phase fractional order systems

    , Article Proceedings of the IEEE International Conference on Control Applications ; 2012 , Pages 855-858 ; 9781467345033 (ISBN) Tabatabaei, M ; Haeri, M ; Sharif University of Technology
    In this paper the characteristic ratio assignment (CRA) method is employed to control transient response of a class of non-minimum phase fractional order systems. Since fractional order all-pass filter could not be realized, the fractional unstable zeros are converted to integer unstable zeros by multiplying complementary polynomials to numerator and denominator polynomials of system's transfer function. Doing so, the closed loop system would be an integer order all-pass filter multiple an all-pole fractional transfer function determined from CRA method. Computer simulation results are presented to illustrate the performance of the proposed method. m  

    Constrained tuning of two-parameter controllers: A centroid approach

    , Article Proceedings of the Institution of Mechanical Engineers. Part I: Journal of Systems and Control Engineering ; Volume 226, Issue 5 , 2012 , Pages 685-698 ; 09596518 (ISSN) Rahimian, M. A ; Tavazoei, M. S ; Sharif University of Technology
    The problem of tuning a two-parameter controller has been formulated as finding the centroid of the admissible region specified by the set of constraints that the controller should satisfy. The constraints can be as general as the closed-loop system stability or they may include several requirements on various stability, sensitivity, or performance measures. The design of stabilizing proportional-derivative (PD) controllers using the centroid of the stability region in the controller parameter space is considered as a case study. To this end, analytical formulas are derived to describe the stability boundaries of a class of integrating time delay systems, the stability region of which has a... 

    Adaptive observer-based synchronization of two non-identical chaotic systems with unknown parameters

    , Article JVC/Journal of Vibration and Control ; Volume 23, Issue 3 , 2017 , Pages 389-399 ; 10775463 (ISSN) Bagheri, P ; Shahrokhi, M ; Salarieh, H ; Sharif University of Technology
    SAGE Publications Inc  2017
    In this study, adaptive observer-based synchronization of chaotic systems is considered. The master and slaves systems have different dynamics and it is assumed that the master system parameters are unknown while its states are available. First, it is assumed that the slave system parameters are known but its states are not completely available. It is shown that an observer for the slave system can be designed and applied for the purpose of synchronization. Based on a Lyapunov function, an adaptive law for master parameters estimation and a control law for the synchronization goal are extracted. Stability of the entire system including the observer dynamics has been proved. Further, it is... 

    Decomposition and robust non-fragile stabilisation of singular time-delay systems

    , Article IET Control Theory and Applications ; Volume 12, Issue 13 , 2018 , Pages 1882-1888 ; 17518644 (ISSN) Zahedi, F ; Haeri, M ; Sharif University of Technology
    This study presents a new approach to decompose singular time-delay systems (STDSs) in a way that they can be transformable to normal time-delay systems (TDSs) with a lower order. Necessary and sufficient conditions are provided to determine which STDSs can be transformed to TDSs. Also, a stabilisation method is provided to stabilise the system, while the time delay in the system can belong to several distinct intervals or even everywhere. The proposed method is non-fragile towards controller parameters. This method also reveals one of the many applicable situations of the proposed decomposition. The effectiveness of the proposed method is illustrated through some examples. © 2018 The... 

    Comparing the performance of reference trajectory management and controller reconfiguration in attitude fault tolerant control

    , Article 2017 Asia Conference on Mechanical and Aerospace Engineering, ACMAE 2017, 29 December 2017 through 31 December 2017 ; Volume 151 , 2018 ; 2261236X (ISSN) Moradi, R ; Alikhani, A ; Jegarkandi, M. F ; Sharif University of Technology
    EDP Sciences  2018
    Reference trajectory management is a method to modify reference trajectories for the faulty system. The modified reference trajectories define new maneuvers for the system to retain its pre-fault dynamic performance. Controller reconfiguration is another method to handle faults in the system, for instance by adjusting the controller parameters (coefficients). Both of these two methods have been considered in the literature and are proven to be capable of handling various faults. However, the comparison of these two methods has not been considered sufficiently. In this paper, a controller reconfiguration mechanism and a reference trajectory management are proposed for the spacecraft attitude... 

    Trajectory following of a micro motion stage based on closed-loop FEM simulation

    , Article ASME International Mechanical Engineering Congress and Exposition, IMECE 2007, Seattle, WA, 11 November 2007 through 15 November 2007 ; Volume 11 PART A , 2008 , Pages 155-158 ; 079184305X (ISBN); 9780791843055 (ISBN) Shahidi, A ; Mahboobi, S. H ; Pirouzpanah, S ; Esteki, H ; Sarkar, S ; Sharif University of Technology
    Micro motion stages are one of the essential components in field of micro robotics and ultra fine positioning systems. This research presents the optimum design of a 3-DOF micro motion stage and its position control using FEM simulation. This stage to be studied uses a 3 RRR flexure hinge base compliant mechanism driven by three piezoelectric stack actuators to provide micro scale planar motion. First of all parametric modeling of the stage will be fulfilled in ANSYS environment utilizing a commercial piezostack and different types of flexure hinges. Hence the Jacobian matrix will be achieved for each case. The optimum selection of the hinge form will be achieved upon results of the previous... 

    Synchronization of uncertain chaotic systems using active sliding mode control

    , Article Chaos, Solitons and Fractals ; Volume 33, Issue 4 , 2007 , Pages 1230-1239 ; 09600779 (ISSN) Haeri, M ; Tavazoei, M. S ; Naseh, M. R ; Sharif University of Technology
    We apply the active sliding mode controller to synchronize two uncertain chaotic systems. Uncertainties are considered both in linear and nonlinear parts of the system dynamics. We have also studied the case that the signals are contaminated by measuring channel noise. It is shown that having some conditions on the uncertainties and noise magnitude, the closed loop stability can be guaranteed. The synchronization errors are shown to be confined into some bounded value. Numerical simulations are presented to evaluate the analysis and effectiveness of the controller. © 2006 Elsevier Ltd. All rights reserved  

    Performance analysis of CDM as an AQM congestion controller in dynamic networks

    , Article EUROCON 2005 - The International Conference on Computer as a Tool, Belgrade, 21 November 2005 through 24 November 2005 ; Volume I , 2005 , Pages 680-683 ; 142440049X (ISBN); 9781424400492 (ISBN) Bigdeli, N ; Haeri, M ; Sharif University of Technology
    IEEE Computer Society  2005
    The performance of a new robust AQM strategy for dynamically varying TCP/AQM networks is proposed. Network variations include in both network topology and traffic variations. The developed AQM is designed based on Coefficient Diagram Method (CDM), which is a new indirect pole placement method that considers the speed, stability and robustness of the closed loop system in terms of time domain specifications. Simulation results show different features of the proposed method. ©2005 IEEE  

    A new variable structure control methodology for electrical/mechanical parameter estimation of induction motor

    , Article 2003 American Control Conference, Denver, CO, 4 June 2003 through 6 June 2003 ; Volume 5 , 2003 , Pages 4047-4052 ; 07431619 (ISSN) Akbarzadeh-T, M. R ; Faezian, G ; Tabatabaei Y, H ; Sargolzaei, N ; Sharif University of Technology
    Induction motor parameter estimation is generally needed for such purposes as fault detection and the achievement of high dynamic performance drives. This paper is an attempt to use variable structure control (VSC) methodology for the on-line estimation of several significant mechanical and electrical induction motor parameters. The estimated parameters are rotor resistance, magnetizing inductance, stator resistance and viscous damping coefficient In this combined control/estimation method, we propose to apply field-oriented control to the non-linear model of induction motor, and then transform the model by Input-state linearization into canonical form. Application of variable structure... 

    Multi-Echelon Mixed-loop Supply Chain Network Design under Disruption Conditions

    , M.Sc. Thesis Sharif University of Technology Beheshti, Saeed (Author) ; Haji, Rasoul (Supervisor) ; Haji, Alireza (Supervisor)
    Fulfilling the demands of customers, used to be the main purpose of Supply Chain Network Designers. Soon after that, the environmental concerns created the concept of Reverse Logistic in order to prevent goods from being scattered in the environment after their disposal. Governmental regulations and people's concerns, forced the factories to gather the created pollutions of the environment. They gradualy confessed the positive impacts of these ruturns on their financials. The flow of forward and reverse logistics establishes a Closed-Loop in which the returning economical circumstances were transferd into original factories. Later, Open-Loops were created. In open-loops the returns have to... 

    Optimal PID control of a nano-Newton CMOS-MEMS capacitive force sensor for biomedical applications

    , Article Mechanics and Industry ; Vol. 15, issue. 2 , January , 2014 , p. 139-145 Mozhdehi, R. J ; Ghafari, A. S ; Sharif University of Technology
    This paper presents closed loop simulation of a CMOS-MEMS force sensor for biomedical applications employing an optimal proportional-integral-derivative controller. Since the dynamic behavior of the sensor under investigation is nonlinear the iterative feedback tuning approach was proposed for optimal gains tuning of the proposed controller. Simulation results presented in this research illustrate that the proposed controller suppresses the undesired in-plane vibration induced by environment or gripper 40 times faster than the nonlinear controller proposed in the literature. To suppress the maximum input disturbance the maximum voltage was approximately 18 V which was less than the pull-in... 

    Boundary stabilization of non-classical micro-scale beams

    , Article Applied Mathematical Modelling ; Volume 37, Issue 20-21 , 2013 , Pages 8709-8724 ; 0307904X (ISSN) Vatankhah, R ; Najafi, A ; Salarieh, H ; Alasty, A ; Sharif University of Technology
    In this paper, the problem of boundary stabilization of a vibrating non-classical micro-scale Euler-Bernoulli beam is considered. In non-classical micro-beams, the governing Partial Differential Equation (PDE) of motion is obtained based on the non-classical continuum mechanics which introduces material length scale parameters. In this research, linear boundary control laws are constructed to stabilize the free vibration of non-classical micro-beams which its governing PDE is derived based on the modified strain gradient theory as one of the most inclusive non-classical continuum theories. Well-posedness and asymptotic stabilization of the closed loop system are investigated for both cases... 

    Robust stability check for fractional PID-based control systems

    , Article Transactions of the Institute of Measurement and Control ; Volume 35, Issue 2 , 2013 , Pages 236-246 ; 01423312 (ISSN) Akbari Moornani, K ; Haeri, M ; Sharif University of Technology
    This paper considers a closed-loop system consisting of a fractional/integer order system and a fractional PID controller. Assuming that the uncertain coefficients of the fractional PID controller lie in some known intervals independently (i.e. that controller is a member of an interval family), the paper presents some easy to use theorems to investigate the robust bounded-input bounded-output stability of the resultant closed-loop system. Moreover, a finite frequency bound required in drawing the related graphs has also been provided. Finally, some numerical examples are presented to illustrate the results  

    Sensitivity analysis of CRA based controllers in fractional order systems

    , Article Signal Processing ; Volume 92, Issue 9 , September , 2012 , Pages 2040-2055 ; 01651684 (ISSN) Tabatabaei, M ; Haeri, M ; Sharif University of Technology
    Elsevier  2012
    This paper focuses on robust performance analysis of a closed loop fractional order system through a sensitivity approach. The characteristic ratio assignment method is selected to attain a desired closed loop transient response. Then, we compute the sensitivity of such a desired transfer function with respect to its characteristic ratio and we explore its specifications. The relation between the coefficient diagram shape and the relative stability of the closed loop system is discussed. Also, the closed loop poles variations due to the changes in the characteristic ratios are investigated. Finally, we study a pseudo second order process to verify the robust performance of the characteristic... 

    Welding current and arc voltage control in a GMAW process using ARMarkov based MPC

    , Article Control Engineering Practice ; Volume 19, Issue 12 , December , 2011 , Pages 1408-1422 ; 09670661 (ISSN) Mousavi Anzehaee, M ; Haeri, M ; Sharif University of Technology
    A predictive functional controller based on ARMarkov model structure has been designed to control welding current and arc voltage in a GMAW process. The closed loop system performance is investigated through computer simulations and is compared by those achieved from implementing two commonly used controllers i.e. PI and feedback linearization based PID. The local stability of the closed loop system is analyzed in the presence of uncertainties in the linearized model of the process as well as the control parameters. Finally it is shown that the proposed controller performs like a PI controller along with a pre-filter compensator  

    Robustness in fractional proportional-integral-derivative-based closed-loop systems

    , Article IET Control Theory and Applications ; Volume 4, Issue 10 , Volume 4, Issue 10 , 2010 , Pages 1933-1944 ; 17518644 (ISSN) Akbari Moornani, K ; Haeri, M ; Sharif University of Technology
    Robustness of a fractional proportional-integral-derivative (PID)-based control system is investigated. At first the largest pathwise connected region subset of a box in three-dimensional space of the parameters of the model is determined such that the closed-loop system is bounded-input bounded-output stable for any point inside it. Then a value that represents the size (in a specified sense) of the calculated region in the first stage and can be considered as a margin for the robustness of the closed-loop system is computed. Furthermore, lower and upper frequency bounds required in depiction of boundaries of the region and computing the mentioned margin are provided. Some special cases in... 

    Design of sliding mode and model reference adaptive control strategies for multivariable tape transport mechanism: a performance comparison

    , Article Microsystem Technologies ; Volume 22, Issue 2 , 2016 , Pages 419-431 ; 09467076 (ISSN) Abbasi, M. H ; Moradian, H ; Moradi, H ; Sharif University of Technology
    Springer Verlag 
    This paper presents sliding mode control and model reference adaptive control strategies for the tape transport mechanism. A nonlinear multivariable MIMO model of the process, consisting of take-up and supply reel servos for tape tension control and capstan servo for speed control is considered. The sliding mode control is applied for the nonlinear dynamic model of the process, while the model reference adaptive control deals with the linearized one. Moreover, in order to associate with the realistic model of system, design of controllers is accomplished with respect to parametric uncertainties. It is shown that both control strategies can guarantee asymptotic stability of the closed-loop...