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structured-uncertainties
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Decentralized integral controllability of linear uncertain systems with correlated and independent uncertainties
, Article Chemical Engineering Science ; Volume 94 , 2013 , Pages 120-126 ; 00092509 (ISSN) ; Nobakhti, A ; Sharif University of Technology
2013
Abstract
Decentralized integral controllability (DIC) is an important property of industrial and process multivariable control systems. In this paper, some of the previously proposed conditions for the study of the DIC of certain systems are extended to treat systems with correlated and independent uncertainty. These conditions are based on the concept of the stability of Polytopic and Interval family of matrices, and evaluation of the Lyapunov condition only at special vertices of these families. By comparison with previous sufficient conditions, and known necessary conditions, it is demonstrated that the newly proposed criteria are significantly less conservative, especially in the case of...
On the integrity of uncertain systems with structured uncertainty
, Article Industrial and Engineering Chemistry Research ; Volume 50, Issue 24 , 2011 , Pages 13940-13946 ; 08885885 (ISSN) ; Nobakhti, A ; Sharif University of Technology
Abstract
The integrity of decentralized controllers with integral action, with respect to loop failures, has been researched relatively well. Important results have been found, with respect to the Relative Gain Array (RGA). However, less has been done on the treatment of the integrity of uncertain systems. This paper builds on the more-recent progress on the analysis of uncertain systems and presents new conditions for the integrity of closed-loop systems. The developed Integral Controllable (IC), Integral Controllable with Integrity (ICI), and Decentralized Integral Controllability (DIC) conditions are derived using a model of uncertainties that allows both unstructured and structured independent...
Robust stability and performance analysis of positive systems using linear programming
, Article 24th Mediterranean Conference on Control and Automation, 21 June 2016 through 24 June 2016 ; 2016 , Pages 100-105 ; 9781467383455 (ISBN) ; Nobakhti, A ; MCA ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
Abstract
This work presents a new necessary and sufficient condition for robust stability and robust performance of positive linear time invariant (LTI) systems with structured uncertainties. It is known that robustness analysis of LTI systems with structured uncertainties requires evaluation of structured singular value (SSV), which is known to be NP-hard. This paper shows that for positive systems, the structured singular value can be estimated efficiently using linear programming. Thus, the robustness analysis of positive systems is simplified to easily verifiable conditions that scale linearly with the dimensions of the system. This property finds great utility in analysis and synthesis of large...
μ-Synthesis control for an islanded microgrid with structured uncertainties
, Article IECON Proceedings (Industrial Electronics Conference), 7 November 2011 through 10 November 2011 ; November , 2011 , Pages 3064-3069 ; 9781612849720 (ISBN) ; Karimi, H ; Sharif University of Technology
2011
Abstract
This paper presents a robust control scheme for an islanded microgrid in the presence of structured uncertainties. The microgrid consists of parallel connection of two Distributed Generation (DG) units and a passive load. The DG units are connected to the passive load by using the power electronics converters. The microgrid model is structurally uncertain due to the large perturbations in the load parameters. To deal with the uncertainties, a Linear Fractional Representation (LFR) of the parametrically uncertain system is obtained. To achieve robust performance, the μ-synthesis approach is applied to the derived LFR model to design a μ controller. The resultant controller is structurally...
A class of globally convergent velocity observers for robotic manipulators
, Article IEEE Transactions on Automatic Control ; Volume 54, Issue 8 , 2009 , Pages 1956-1961 ; 00189286 (ISSN) ; Sharif University of Technology
2009
Abstract
We present a method for global estimation of joint velocities in rigid manipulators. A class of velocity observers with smooth dynamics are introduced whose structure depend on freely selectable functions and gains giving the flexibility of achieving multiple design objectives at the same time. Unlike most methods, no a priori knowledge of an upper bound for velocity magnitude is used. An adaptive version of the observer is also presented to handle a class of structured uncertainties in manipulator model. Simulation example illustrates low noise sensitivity of the globally convergent observer in comparison with semi-globally convergent observers. © 2009 IEEE
Multi model robust control design for a floating offshore variable speed wind turbine with tension leg platform
, Article Ocean Engineering ; Volume 266 , 2022 ; 00298018 (ISSN) ; Sadati, N ; Member, IEEE ; Sharif University of Technology
Elsevier Ltd
2022
Abstract
This paper presents a multi-model robust control (MMRC) design for an offshore variable speed wind turbine with tension leg platform. The proposed control scheme covers the model uncertainty in the above rated wind speed, and it provides a reliable control for power regulation while minimizing the mechanical loads on the wind turbine structure. For this purpose, the above rated wind speed region is divided into several wind speed groups, and a set of linearized models are obtained from the Fatigue, Aerodynamics, Structures, and Turbulence (FAST) simulator for various mean wind speeds of each group. Using Weibull wind speed distribution, a nominal model with additive uncertainty is generated...
Robust flutter analysis and control of a wing
, Article Aircraft Engineering and Aerospace Technology ; Volume 84, Issue 6 , 2012 , Pages 423-438 ; 00022667 (ISSN) ; Moghaddam, M ; Rahim, M ; Sharif University of Technology
2012
Abstract
Purpose - The purpose of this paper is to present a novel approach in aeroservoelastic analysis and robust control of a wing section with two control surfaces in leading-edge and trailing-edge. The method demonstrates how the number of model uncertainties can affect the flutter margin. Design/methodology/approach - The proposed method effectively incorporates the structural model of a wing section with two degrees of freedom of pitch and plunge with two control surfaces on trailing and leading edges. A quasi-steady aerodynamics assumption is made for the aerodynamic modeling. Basically, perturbations are considered for the dynamic pressure models and uncertainty parameters are associated...