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Total 1053 records

    Extension of nonlinear DMC for MIMO systems

    , Article Fourth International Conference on Control and Automation, Montreal, Que., 10 June 2003 through 12 June 2003 ; 2003 , Pages 375-379 ; 078037777X (ISBN); 9780780377776 (ISBN) Haeri, M ; Beik, H. Z ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2003
    Abstract
    In this paper an extended approach to the nonlinear DMC algorithm is proposed, which can handle constrained and MIMO systems under some defined conditions. This extension also admits higher control, M, and prediction, P, horizons that are required to increase the performance of the controller in most practical applications. Simulation results of the proposed method in the control of a stirred tank reactor with 2 inputs and 2 outputs nonlinear model are presented to illustrate effectiveness of the method and its justification. © 2003 IEEE  

    Estimation and stability over AWGN channel in the presence of fading, noisy feedback channel and different sample rates

    , Article Systems and Control Letters ; Volume 123 , 2019 , Pages 75-84 ; 01676911 (ISSN) ; https://www.sciencedirect.com/science/article/abs/pii/S0167691118301993 Sanjaroon, V ; Farhadi, A ; Khalaj, B. H ; Motahari, A. S ; Sharif University of Technology
    Elsevier B.V  2019
    Abstract
    This paper is concerned with estimation and stability of control systems over communication links subject to limited capacity, power constraint, fading, noisy feedback, and different transmission rate rather than system sampling rate. A key issue addressed in this paper is that in the presence of noisy feedback associated with channel, which models transmission of finite number of bits over such links as is the case in most practical scenarios, the well-known eigenvalues rate condition is still a tight bound for stability. Based on an information theoretic analysis, necessary conditions are derived for stability of discrete-time linear control systems via the distant controller in the mean... 

    Performance comparison of admission control policies for new calls in soft-handoff regions for CDMA cellular networks

    , Article Scientia Iranica ; Volume 11, Issue 3 , 2004 , Pages 193-202 ; 10263098 (ISSN) Ashtiani, F ; Aref, M. R ; Salehi, J. A ; Sharif University of Technology
    Sharif University of Technology  2004
    Abstract
    In this paper, two basic new call admission control policies in soft-handoff regions in Code-Division Multiple-Access (CDMA) cellular networks are compared. The two policies are Independent Decision Policy (IDP), which is, approximately, equivalent to a directed retry policy proposed for non-CDMA cellular networks and Collective Decision Policy (CDP). The merits in this comparison include the tradeoff between carried traffic and quality loss probability while maintaining other traffic parameters (such as blocking and dropping (handoff failure) probabilities) sufficiently low. Using numerical results, it is deduced that the CDP leads to a better overall performance. Another important issue... 

    Approximation of titration curves by artificial neural networks and its application to pH control

    , Article Scientia Iranica ; Volume 6, Issue 5 , 2000 , Pages 82-91 ; 10263098 (ISSN) Pishvaie, M. R ; Shahrokhi, M ; Sharif University of Technology
    Sharif University of Technology  2000
    Abstract
    Advanced model-based control of pH processes is noticeably a chemical modeling issue, because it can have a profound effect on the attainable control quality. This is especially the case when the pH regulation of streams, consisting of hundreds of constituents with varying concentrations, is encountered. The severe non-linear behavior of pH processes is reflected in the titration curve of the process stream. The performances of all model-based controllers are highly dependent on the accuracy of the model. Considering a great number of parameters such as dissociation constants, solubility products and characteristic concentrations places the designer in a dilemma of choosing between... 

    Comparison of four adaptive PID controllers

    , Article Scientia Iranica ; Volume 6, Issue 5 , 2000 , Pages 129-136 ; 10263098 (ISSN) Shahrokhi, M ; Fanaei, M. A ; Sharif University of Technology
    Sharif University of Technology  2000
    Abstract
    PID controllers have been used for many years in industry and if a controller is well tuned, its performance is acceptable for many industrial processes. When the operating point is changed, due to nonlinear behavior of most processes, the controller should be retuned. In this regard, several self-tuning PID controllers are proposed in the literature. In this paper, four such algorithms are compared through simulation and experimental studies. In the simulation study, the effects of factors such as process pole locations, non-minimum phase behavior and model changes on the performance of the schemes are investigated. Simulation and experimental results demonstrate that one of the schemes... 

    Study on control input energy efficiency of fractional order control systems

    , Article IEEE Journal on Emerging and Selected Topics in Circuits and Systems ; Volume 3, Issue 3 , July , 2013 , Pages 475-482 ; 21563357 (ISSN) Tavakoli Kakhki, M ; Haeri, M ; Tavazoei, M. S ; Sharif University of Technology
    2013
    Abstract
    Control input energy efficiency is an important issue which should be considered in designing any control system. Due to the importance of this subject, in the present paper fractional order control systems are studied in the viewpoint of control input energy efficiency. In this study, the divergent terms of the control input energy function of fractional order control systems are obtained. It is shown that these terms have a significant role in the amount of the energy injected to the plant by the controller. Finally, two examples are provided to demonstrate the usefulness of the presented results in the paper  

    Robust D-stability test of LTI general fractional order control systems

    , Article IEEE/CAA Journal of Automatica Sinica ; Volume 7, Issue 3 , May , 2020 , Pages 853-864 Mohsenipour, R ; Liu, X ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2020
    Abstract
    This work deals with the robust D-stability test of linear time-invariant ( LTI ) general fractional order control systems in a closed loop where the system and - or the controller may be of fractional order. The concept of general implies that the characteristic equation of the LTI closed loop control system may be of both commensurate and non-commensurate orders, both the coefficients and the orders of the characteristic equation may be nonlinear functions of uncertain parameters, and the coefficients may be complex numbers. Some new specific areas for the roots of the characteristic equation are found so that they reduce the computational burden of testing the robust D-stability. Based on... 

    Robust adaptive fractional order proportional integral derivative controller design for uncertain fractional order nonlinear systems using sliding mode control

    , Article Proceedings of the Institution of Mechanical Engineers. Part I: Journal of Systems and Control Engineering ; Volume 232, Issue 5 , 1 May , 2018 , Pages 550-557 ; 09596518 (ISSN) Yaghooti, B ; Salarieh, H ; Sharif University of Technology
    SAGE Publications Ltd  2018
    Abstract
    This article presents a robust adaptive fractional order proportional integral derivative controller for a class of uncertain fractional order nonlinear systems using fractional order sliding mode control. The goal is to achieve closed-loop control system robustness against the system uncertainty and external disturbance. The fractional order proportional integral derivative controller gains are adjustable and will be updated using the gradient method from a proper sliding surface. A supervisory controller is used to guarantee the stability of the closed-loop fractional order proportional integral derivative control system. Finally, fractional order Duffing–Holmes system is used to verify... 

    Estimation and stability over AWGN channel in the presence of fading, noisy feedback channel and different sample rates

    , Article Systems and Control Letters ; Volume 123 , 2019 , Pages 75-84 ; 01676911 (ISSN) Sanjaroon, V ; Farhadi, A ; Khalaj, B. H ; Seyed Motahari, A ; Sharif University of Technology
    Elsevier B.V  2019
    Abstract
    This paper is concerned with estimation and stability of control systems over communication links subject to limited capacity, power constraint, fading, noisy feedback, and different transmission rate rather than system sampling rate. A key issue addressed in this paper is that in the presence of noisy feedback associated with channel, which models transmission of finite number of bits over such links as is the case in most practical scenarios, the well-known eigenvalues rate condition is still a tight bound for stability. Based on an information theoretic analysis, necessary conditions are derived for stability of discrete-time linear control systems via the distant controller in the mean... 

    A rule-based advanced static var compensator control scheme for transient stability improvement

    , Article Scientia Iranica ; Volume 13, Issue 4 , 2006 , Pages 327-336 ; 10263098 (ISSN) Abazari, S ; Ehsan, M ; Zolghadri, M. R ; Mahdavi, J ; Sharif University of Technology
    Sharif University of Technology  2006
    Abstract
    The paper presents the application of a rule- based control scheme for an Advanced Static Var Compensator (ASVC) to improve power system transient stability. The proposed method uses a current reference, based on the Transient Energy Function (TEF) approach. The proposed scheme provides, also, a continuous control of the reactive power flow. The performance of the proposed approach is compared with that of a system using a conventional control method and of a system without ASVC. A single-machine system and an IEEE three machine system are used to verify the performance of the proposed method. © Sharif University of Technology  

    Modelling of a complex system using the dynamic rule prediction

    , Article WSEAS Transactions on Systems ; Volume 5, Issue 12 , 2006 , Pages 2833-2838 ; 11092777 (ISSN) Damangir, S ; Jafarijashemi, G ; Zohoor, H ; Sharif University of Technology
    2006
    Abstract
    Presented in this paper are a method, named the Dynamic Rule Prediction (DRP), which predicts the behavior of a system and its application in designing a controller. The aim of the study is to overcome some of the limitations and shortcoming of the other modeling methods. The effectiveness of this method is verified. The controller based on DRP possesses two main features. It can control the system without any prior knowledge of the controlled plant. It is, also, superior as its high-speed prediction. This paper focuses on the robot manipulator controllers and applications of this approach in it  

    Low-order H∞ controller design for an active suspension system via LMIs

    , Article IEEE Transactions on Industrial Electronics ; Volume 53, Issue 2 , 2006 , Pages 554-560 ; 02780046 (ISSN) Amirifar, R ; Sadati, N ; Sharif University of Technology
    2006
    Abstract
    An application of a new controller order reduction technique with stability and performance preservation based on linear matrix inequality optimization to an active suspension system is presented. In this technique, the rank of the residue matrix of a proper rational approximation of a high-order H∞controller subject to the H∞-norm of a frequency-weighted error between the approximated controller and the high-order H∞ controller is minimized. However, because solving this matrix rank minimization problem is very difficult, the rank objective function is replaced with a nuclear-norm that can be reduced to a semidefinite program so that it can be solved efficiently. Application to the active... 

    Identification and adaptive control of the uncertain lorenz system

    , Article 2005 ASME International Mechanical Engineering Congress and Exposition, IMECE 2005, Orlando, FL, 5 November 2005 through 11 November 2005 ; Volume 74 DSC, Issue 2 PART B , 2005 , Pages 1105-1111 ; 0791842169 (ISBN); 9780791842164 (ISBN) Pishkenari, H. N ; Shahrokhi, M ; Sharif University of Technology
    2005
    Abstract
    In this paper an identification method which can estimate the unknown parameters of a general nonlinear system based on three techniques (gradient, least-squares and rapid identification) has been developed. The stability of the proposed schemes has been shown using the Lyapunov stability theorem. The properties of each identification technique have been discussed briefly. Open loop identification of the Lorenz chaotic system is presented to show the effectiveness of the proposed approach. To illustrate the efficiency of the identification method for control purposes, it has been applied for controlling the well-known Lorenz system. By exploiting the property of the system a novel... 

    Feedback channel in linear noiseless dynamic systems controlled over the packet erasure network

    , Article International Journal of Control ; Volume 88, Issue 8 , 2015 , Pages 1490-1503 ; 00207179 (ISSN) Farhadi, A ; Sharif University of Technology
    Taylor and Francis Ltd  2015
    Abstract
    This paper is concerned with tracking state trajectory at remote controller, stability and performance of linear time-invariant noiseless dynamic systems with multiple observations over the packet erasure network subject to random packet dropout and transmission delay that does not necessarily use feedback channel full time. Three cases are considered in this paper: (1) without feedback channel, (2) with feedback channel intermittently and (3) with full time availability of feedback channel. For all three cases, coding strategies that result in reliable tracking of state trajectory at remote controller with asymptotically zero mean absolute estimation error are presented. Asymptotic mean... 

    Reference tracking of nonlinear dynamic systems over AWGN channel using the describing function

    , Article Scientia Iranica ; Volume 26, Issue 3 D , 2019 , Pages 1724-1735 ; 10263098 (ISSN) Parsa, A ; Farhadi, A ; Sharif University of Technology
    Sharif University of Technology  2019
    Abstract
    This paper presents a new technique for mean square asymptotic reference tracking of nonlinear dynamic systems over Additive White Gaussian Noise (AWGN) channel. The nonlinear dynamic system has periodic outputs and sinusoidal inputs and is cascaded with a bandpass filter acting as an encoder. By using the describing function method, the nonlinear dynamic system is represented by an equivalent linear dynamic system. Then, for this system, a mean square asymptotic reference tracking technique, including an encoder, a decoder, and a controller, is presented. It is shown that the proposed reference tracking technique results in mean square asymptotic reference tracking of nonlinear dynamic... 

    Reference tracking of nonlinear dynamic systems over AWGN channel using the describing function

    , Article Scientia Iranica ; Volume 26, Issue 3 D , 2019 , Pages 1724-1735 ; 10263098 (ISSN) Parsa, A ; Farhadi, A ; Sharif University of Technology
    Sharif University of Technology  2019
    Abstract
    This paper presents a new technique for mean square asymptotic reference tracking of nonlinear dynamic systems over Additive White Gaussian Noise (AWGN) channel. The nonlinear dynamic system has periodic outputs and sinusoidal inputs and is cascaded with a bandpass filter acting as an encoder. By using the describing function method, the nonlinear dynamic system is represented by an equivalent linear dynamic system. Then, for this system, a mean square asymptotic reference tracking technique, including an encoder, a decoder, and a controller, is presented. It is shown that the proposed reference tracking technique results in mean square asymptotic reference tracking of nonlinear dynamic... 

    Performance evaluation of communication networks for parallel and distributed systems

    , Article Parallel Computing ; Volume 32, Issue 11-12 , 2006 , Pages 775-776 ; 01678191 (ISSN) Sarbazi Azad, H ; Ould Khaoua, M ; Zomaya, A. Y ; Sharif University of Technology
    2006

    Non-linear feedback optimal control law for minimum-time injection problem using fuzzy system

    , Article Aircraft Engineering and Aerospace Technology ; Volume 77, Issue 5 , 2005 , Pages 376-383 ; 00022667 (ISSN) Pourtakdoust, S. H ; Rahbar, N ; Novinzadeh, A. B ; Sharif University of Technology
    2005
    Abstract
    Purpose - To devise a new technique to synthesise optimal feedback control law for non-linear dynamic systems through fuzzy logic. Design/methodology/approach - The proposed methodology utilizes the open-loop optimal control solutions (OCSs) of the non-linear systems for the training of the fuzzy system in the process of developing closed-loop fuzzy logic guidance (FLG). This is achieved through defining a set of non-dimensionalised variables related to the system states. Findings - FLG is capable of generating closed-loop control law for the non-linear problem investigated. Since the proposed fuzzy structure is independent of the system equations, the approach is potentially applicable to... 

    Optimal yaw moment control law for improved vehicle handling

    , Article Mechatronics ; Volume 13, Issue 7 , 2003 , Pages 659-675 ; 09574158 (ISSN) Esmailzadeh, E ; Goodarzi, A ; Vossoughi, G. R ; Sharif University of Technology
    2003
    Abstract
    A new optimal control law for direct yaw moment control, to improve the vehicle handling, is developed. Although, this can be considered as part of a multi-layer system, for the traction control of a motorized wheels electric vehicle, but the results of this study are quite general and can be applied to other types of vehicles. The dynamic model of the vehicle system is initially developed and, using the well-known optimal control theory, an optimal controller is designed. Two different versions of control laws are considered here and the performance of each version of the control law is compared with the other one. The numerical simulation of the vehicle handling with and without the use of... 

    Direct yaw moment control for motorized wheel electric vehicles

    , Article 18th Biennial Conference on Mechanical Vibration and Noise, Pittsburgh, PA, 9 September 2001 through 12 September 2001 ; Volume 6 A , 2001 , Pages 215-222 Goodarzi, A ; Esmailzadeh, E ; Vossoughi, G. R ; Sharif University of Technology
    2001
    Abstract
    A new control law for direct yaw moment control of an electric vehicle is developed. Although this study is considered as part of a global control system for the traction control of a four motorized wheel electric vehicle, but the results of this study is quite general and can be applied to other types of vehicles. The dynamic model of the system has been analyzed and, in accordance with the optimal control theory, an optimal controller is designed. Two different versions of the control law have been considered and the performance of each version has been separately studied and compared with each other. Finally, the numerical simulation of the vehicle-handling model with and without the use...