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Fault-tolerant controller design for ALSTOM gasifier benchmark challenge
, Article Journal of Advanced Research in Dynamical and Control Systems ; Volume 7, Issue 1 , 2015 , Pages 90-116 ; 1943023X (ISSN) ; Babazadeh, M ; Sharif University of Technology
Institute of Advanced Scientific Research, Inc
2015
Abstract
In this paper, a new fully decentralized control strategy for the ALESTOM gasifier benchmark is presented. The proposed decentralized fault-tolerant control scheme overcomes the conventional drawbacks of the previously developed centralized strategies for the linearized model of gasifier system. To achieve the objective, first, the best pairing has been selected based on integrity screening tools as well as physical considerations. Then, a fully decentralized Proportional Integral (PI) controller has been proposed. Finally simulation results performed in MATLAB show that the designed controller is capable of achieving desired performance for three different scenarios, i.e., full, half and no...
A unified acceptance test framework for power plant gas turbine control systems
, Article ISA Transactions ; Volume 85 , February , 2018 , Pages 262-273 ; 00190578 (ISSN) ; Babazadeh, M ; Sharif University of Technology
ISA - Instrumentation, Systems, and Automation Society
2018
Abstract
Renovation and retrofit of gas turbine control systems yield significant economic savings, enhanced reliability, and improved performance. In recent years, the gas turbine industry is increasingly facing the need to well-established procedures for the acceptance tests of renovated control systems. This paper proposes a unified framework to evaluate the performance of renovated gas turbine control systems. Under a set of assumptions on the ambient and fuel conditions, a low-complexity modular model is presented and identified using optimization-oriented identification techniques. The accuracy of the proposed model is validated through experimental studies in full-load, min-load, and no-load...
A unified acceptance test framework for power plant gas turbine control systems
, Article ISA Transactions ; Volume 85 , 2019 , Pages 262-273 ; 00190578 (ISSN) ; Babazadeh, M ; Sharif University of Technology
ISA - Instrumentation, Systems, and Automation Society
2019
Abstract
Renovation and retrofit of gas turbine control systems yield significant economic savings, enhanced reliability, and improved performance. In recent years, the gas turbine industry is increasingly facing the need to well-established procedures for the acceptance tests of renovated control systems. This paper proposes a unified framework to evaluate the performance of renovated gas turbine control systems. Under a set of assumptions on the ambient and fuel conditions, a low-complexity modular model is presented and identified using optimization-oriented identification techniques. The accuracy of the proposed model is validated through experimental studies in full-load, min-load, and no-load...
Direct synthesis of fixed-order multi-objective controllers
, Article Optimal Control Applications and Methods ; Volume 41, Issue 3 , 2020 , Pages 849-865 ; Babazadeh, M ; Nobakhti, A ; Sharif University of Technology
John Wiley and Sons Ltd
2020
Abstract
This paper introduces a new methodology for the design of fixed-order multi-objective output feedback controllers. The problem comprises a set of linear matrix inequalities and an additional rank constraint. The primary idea is to classify convex subsets of the set of rank constrained matrices in such formulations, based on which two noniterative and relatively fast methods are developed. The proposed methods require solving a convex optimization problem at each step and can be applied with any weighted summation of design objectives such as (Formula presented.) performance, (Formula presented.) performance, passivity, and regional pole assignment. Several benchmark systems with performance...
Stabilizing control structures: An optimization framework
, Article IEEE Transactions on Automatic Control ; 2021 ; 00189286 (ISSN) ; Babazadeh, M ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2021
Abstract
This paper presents a new optimization-based approach to determine the class of stabilizing control structures with the necessary set of feedback links for interconnected systems. The proposed approach relies on a graph theoretic interpretation and its equivalence in terms of binary linear programs (BLP). To carry out the primary goal, first, the stabilizability of an LTI system under the decentralized control structure is presented in terms of a BLP. Next, two graph-based criteria are proposed to characterize stabilizing control structures with the required feedback links. Finally, all possible stabilizing control structures with the necessary feedback links are derived via solving a set of...
Stabilizing control structures: An optimization framework
, Article IEEE Transactions on Automatic Control ; Volume 67, Issue 7 , 2022 , Pages 3738-3745 ; 00189286 (ISSN) ; Babazadeh, M ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2022
Abstract
This article presents a new optimization-based approach to determine the class of stabilizing control structures with the necessary set of feedback links for interconnected systems. The proposed approach relies on a graph-theoretic interpretation and its equivalence in terms of binary linear programs (BLPs). To carry out the primary goal, first, the stabilizability of a linear time-invariant (LTI) system under the decentralized control structure is presented in terms of a BLP. Next, two graph-based criteria are proposed to characterize stabilizing control structures with the required feedback links. Finally, all possible stabilizing control structures with the necessary feedback links are...
Model-free LQR design by Q-function learning
, Article Automatica ; Volume 137 , 2022 ; 00051098 (ISSN) ; Babazadeh, M ; Sharif University of Technology
Elsevier Ltd
2022
Abstract
Reinforcement learning methods such as Q-learning have shown promising results in the model-free design of linear quadratic regulator (LQR) controllers for linear time-invariant (LTI) systems. However, challenges such as sample-efficiency, sensitivity to hyper-parameters, and compatibility with classical control paradigms limit the integration of such algorithms in critical control applications. This paper aims to take some steps towards bridging the well-known classical control requirements and learning algorithms by using optimization frameworks and properties of conic constraints. Accordingly, a new off-policy model-free approach is proposed for learning the Q-function and designing the...
Pole assignment and distributed output feedback control via graph-based decomposition
, Article International Journal of Control ; 2022 ; 00207179 (ISSN) ; Babazadeh, M ; Sharif University of Technology
Taylor and Francis Ltd
2022
Abstract
A new distributed observer-based output feedback control design with an arbitrary control structure is proposed. Assuming that the linear time-invariant (LTI) system does not have any fixed-modes with respect to the control structure, the pole placement at the desired locations becomes theoretically feasible. In this paper, the structural output feedback controller design is transformed into equivalent problems based on a graph-theoretic approach. Two augmented structures are established and formulated as the solution of a set of binary linear programs (BLP). The first one facilitates the incorporation of the maximum number of edges in the principal bipartite graph and the second one results...
Improved bounds for the spectrum of interval matrices
, Article IET Control Theory and Applications ; Volume 7, Issue 7 , 2013 , Pages 1022-1028 ; 17518644 (ISSN) ; Babazadeh, M ; Nobakhti, A ; Karimi, H ; Sharif University of Technology
2013
Abstract
This study presents new sufficient conditions for Hurwitz and Schur stability of interval matrices. Tight bounds for the spectrum of interval matrices are estimated using computationally simple optimisation problems. The conservativeness is reduced further by application of ordinary similarity transformation. A necessary and sufficient vertex based criterion for the stability of a subclass of interval systems in continuous and discrete-time cases is also proposed. This enables the spectra for this class of interval systems to be determined exactly. A selection of various examples adopted from existing literature is used to demonstrate the utility of the proposed criteria
New sufficient conditions for robust stability analysis of interval matrices
, Article Systems and Control Letters ; Volume 61, Issue 12 , 2012 , Pages 1117-1123 ; 01676911 (ISSN) ; Babazadeh, M ; Karimi, H ; Nobakhti, A ; Sharif University of Technology
2012
Abstract
This letter presents new sufficient conditions for robust Hurwitz stability of interval matrices. The proposed conditions are based on two approaches: (i) finding a common Lyapunov matrix for the interval family and (ii) converting the robust stability problem into a robust non-singularity problem using Kronecker operations. The main contribution of the letter is to derive accurate and computationally simple optimal estimates of the robustness margin and spectral bound of general interval matrices. The evaluation of the condition relies on the solutions of linear matrix inequalities (LMIs) and eigenvalue problems, both of which are solved very efficiently. The improvements gained by using...
Partial integrity of unstable LTI systems
, Article 24th Mediterranean Conference on Control and Automation, 21 June 2016 through 24 June 2016 ; 2016 , Pages 1302-1306 ; 9781467383455 (ISBN) ; Nobakhti, A ; Babazadeh, M ; MCA ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
Abstract
This paper considers the Integral Stabilizability (IS) and partial integrity of Linear Time Invariant (LTI) systems with an unstable sub-system. The main contribution of the paper is to show that if the unstable sub-system can be stabilized by means of output feedback, then one obtains an integrity condition which is actually equivalent to that of open-loop stable systems, with two additional assumptions. This means the condition may be evaluated solely on the basis of plant information and does not rely on the knowledge of the values of the controller parameters