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multivariable-systems
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Conditions for static pre-compensation
, Article Electronics Letters ; Volume 46, Issue 24 , December , 2010 , Pages 1598-1600 ; 00135194 (ISSN) ; Sharif University of Technology
2010
Abstract
Static pre-compensators are used in industrial applications to reduce interactions of a multivariable system to facilitate implementation of decentralised single-loop control systems. Whilst a wide range of techniques exist for the design of static pre-compensators, not all types of system interactions will yield to a static design. Outlined is a simple test which constitutes a necessary condition for a solution to exist
Conditions for Integrity of Multivariable Systems with Input Saturation
, M.Sc. Thesis Sharif University of Technology ; Nobakhti, Amin (Supervisor)
Abstract
Multivariable control systems as used in the industry usually contain integral action in order to improve tracking of the output with respect to step reference changes. These systems are usually subject to input saturation due to actuator or sensor nonlinearities. The aim of this work is find the conditions for the integrity concept of such multivariable system, e.g. IS, IC, ICI and DIC. First we develop the conditions on the controller gains necessary stabilize the systems and then show that these conditions can changes when one examines integrity conditions
A state feedback strategy for decoupling a class of multivariable systems
, Article 3rd International Conference on Systems, ICONS 2008, Cancun, 13 April 2008 through 18 April 2008 ; 2008 , Pages 29-34 ; 9780769531052 (ISBN) ; Mobed, M ; Sharif University of Technology
2008
Abstract
Here a special state variable feedback or state feedback for short is introduced with the main objective of providing a convenient method for decoupling a MIMO transfer matrix. Decoupling in general and decoupling via state feedback in particular offer obvious advantages in the design and synthesis of controllers for MIMO systems. The early parts of this paper deal with the eigenvalues, poles, and zeros as well as the controllability and observability properties of the proposed closed-loop system as compared with those of the open-loop system. The proposed method is tested on a model of a realistic physical system and results are illustrated. © 2008 IEEE
Lebesgue function for multivariate interpolation by radial basis functions
, Article Applied Mathematics and Computation ; Volume 187, Issue 1 SPEC. ISS , 2007 , Pages 306-314 ; 00963003 (ISSN) ; Jokar, S ; Sharif University of Technology
Elsevier Inc
2007
Abstract
Multivariate interpolation and approximation is a powerful tool for intuition of real world. In this paper we study Lebesgue function and Lebesgue constant for multivariate interpolation by conditionally positive definite RBFs. Also we give a conjecture about similar Bernstein and Erdös problem to multivariate case. © 2006 Elsevier Inc. All rights reserved
Optimization of Sparse Control Structures in Multivariable Systems
, Ph.D. Dissertation Sharif University of Technology ; Nobakhti, Amin (Supervisor)
Abstract
In this thesis, the optimal control structure selection and design of sparse multi-variable control systems is addressed. A fundamental challenge which frequently emerges in engineering, social, and economic sciences, is the optimal selection of a subset of elements, in order to maximally fulfil a design objective. In practice, it is required to solve this underlying selection problem in conjunction with a non-linear or non-convex optimization which is designed to ensure desired performance. The requirement to solve these two problems simultaneously is what makes it inherently difficult; one which has thus far eluded efforts to develop a systematic means of determining its solution. In spite...
Robust and Nonlinear Control of the Boiler-Turbine Unit Performance in a Coal Fired Ultra-Supercritical Once Through Boiler Power Plant in Order to Optimize the Uncertain Problem
, M.Sc. Thesis Sharif University of Technology ; Moradi, Hamed (Supervisor)
Abstract
Nowadays electricity power has a key role in developing various aspects of the world. The great importance of fossil fuel power plants come from their large contribution in electricity power generation. Among the different fossil fuel power generation technologies, supercritical power plants have great advantages. They are an advanced power generation technology with high plant efficiency, high coal utilization and low emission. Their complexity and existing many unavoidable uncertainty sources in their dynamic such as changes of ambient temperature, climate condition and wear of components make their control challenging. To overcome mentioned problems and achieving a good performance, a...
Decomposition via QP
, Article IEEE Transactions on Control Systems Technology ; Volume 20, Issue 6 , October , 2012 , Pages 1630-1637 ; 10636536 (ISSN) ; Nobakhti, A ; Sharif University of Technology
Abstract
This brief presents an algorithm for decoupling multivariable systems based on quadratic programming (QP). A single framework is presented which can be used to design centralized, decentralized, and sparse structures of arbitrary dynamical order. A worked example and a case study are presented to demonstrate the usage and performance. It is shown that only previous methods based on Evolutionary Algorithms are able to achieve slightly higher performance than the proposed algorithm. However, these minor improvements are outweighed by the huge increase in time and costs associated with evolutionary optimizations
Application of fuzzy set modeling in infrastructure visual impact assessment
, Article 10th East Asia-Pacific Conference on Structural Engineering and Construction, EASEC 2010, Bangkok, 3 August 2006 through 5 August 2006 ; Volume 2 , 2006 , Pages 263-268 ; Tolouei, R ; Namazi, S ; Sharif University of Technology
2006
Abstract
Infrastructure visual impact assessment based on an opinion survey and fuzzy set modeling was attempted. Photographs reflecting various transportation infrastructure and environment features were displayed to a group of transportation professionals and users. The group was asked to complete a relevant questionnaire regarding the highway infrastructure appearance acceptability of photographs. A set of visual impact descriptive variables was identified and directly measured from the photographs. Information about the descriptive variables, questionnaire responses and fuzzy set theory was used to develop membership functions of visual acceptability. More than two hundred candidate membership...
Two-internal variable thermodynamics modelling of severe plastic deformation: Dislocation and flow stress evolutions
, Article Materials Science and Technology (United Kingdom) ; Volume 31, Issue 14 , Jan , 2015 , Pages 1788-1793 ; 02670836 (ISSN) ; Kazeminezhad, M ; Sharif University of Technology
Maney Publishing
2015
Abstract
Two-internal variable thermodynamics model is presented to investigate the evolution of microstructure and flow stress during severe plastic deformation. Previous studies have shown that due to heterogeneous distribution of dislocations during severe plastic deformation, the use of multivariable models is needed. In this regard, a two-internal variable model is presented. In the present paper, the dislocation densities in the subgrain boundaries and interiors are considered as internal variables. The model uses general laws of thermodynamics and describes the evolution of the dislocation densities on the basis of parameters such as the self-diffusion activation energy and the stacking fault...
A real-time algorithm for variable-objective motion planning over terrain and threats
, Article Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering ; Volume 229, Issue 6 , 2015 , Pages 1043-1056 ; 09544100 (ISSN) ; Pourtakdoust, S. H ; Sharif University of Technology
SAGE Publications Ltd
2015
Abstract
A major issue required to enhance the autonomy level of unmanned vehicles is real-time motion planning. In this context, optimal trajectories need to be generated online considering the vehicle's dynamic potentials and constraints. However, autonomous air vehicles often need to plan and execute their missions with varying objectives that may even be dictated in flight. Therefore, the current study introduces and focuses on the new concept of variable-objective motion planning. In this regard, a new dynamic multi-objective heuristic optimization algorithm is developed for path and motion planning of autonomous air vehicles in presence of deterministic terrain obstacles as well as random...
Design and assessment of variable-structure LQG PID multivariable controllers
, Article Optimal Control Applications and Methods ; 2016 ; 01432087 (ISSN) ; Nobakhti, A ; Sharif University of Technology
John Wiley and Sons Ltd
2016
Abstract
Control Performance Assessment (CPA) and tuning of PID controllers are studied in this paper. We propose a framework for systematic analysis of the tradeoff between the structural complexity of the controller and its performance. As the measure of the controller performance, an LQG based index is used. The problem is augmented with an additional term which forces sparsity on the complexity of a decentralized PID controller. The desired complexity is controlled via a weighting parameter which determines the cost of each additional element (i.e., P, I, and D terms). The result is a decentralized multivariable PID controller in which the complexity of each loop controller is optimized such that...
Estimating urban ground-level PM10 using MODIS 3km AOD product and meteorological parameters from WRF model
, Article Atmospheric Environment ; Volume 141 , 2016 , Pages 333-346 ; 13522310 (ISSN) ; Sotoudeheian, S ; Arhami, M ; Sharif University of Technology
Elsevier Ltd
2016
Abstract
Satellite remote sensing products of AOD from MODIS along with appropriate meteorological parameters were used to develop statistical models and estimate ground-level PM10. Most of previous studies obtained meteorological data from synoptic weather stations, with rather sparse spatial distribution, and used it along with 10 km AOD product to develop statistical models, applicable for PM variations in regional scale (resolution of ≥10 km). In the current study, meteorological parameters were simulated with 3 km resolution using WRF model and used along with the rather new 3 km AOD product (launched in 2014). The resulting PM statistical models were assessed for a polluted and largely variable...
Design and assessment of variable-structure LQG PID multivariable controllers
, Article Optimal Control Applications and Methods ; Volume 38, Issue 4 , 2017 , Pages 634-652 ; 01432087 (ISSN) ; Nobakhti, A ; Sharif University of Technology
John Wiley and Sons Ltd
2017
Abstract
Control Performance Assessment (CPA) and tuning of PID controllers are studied in this paper. We propose a framework for systematic analysis of the tradeoff between the structural complexity of the controller and its performance. As the measure of the controller performance, an LQG based index is used. The problem is augmented with an additional term which forces sparsity on the complexity of a decentralized PID controller. The desired complexity is controlled via a weighting parameter which determines the cost of each additional element (i.e., P, I, and D terms). The result is a decentralized multivariable PID controller in which the complexity of each loop controller is optimized such that...
Evaluation of partial least-squares regression with multivariate analytical figures of merit for determination of 10 pesticides in milk
, Article International Journal of Environmental Analytical Chemistry ; March , 2020 ; Balsini, P ; Parastar, H ; Sharif University of Technology
Taylor and Francis Ltd
2020
Abstract
A multi-residue method using gas chromatography coupled with flame ionisation detector has been developed for simultaneous determination of 10 pesticides in milk. The methodology involved a sample clean-up procedure using ‘quick, easy, cheap, effective, rugged and safe’ followed by a preconcentration step based on dispersive liquid–liquid microextraction. In this regard, acetonitrile was added to the milk sample with specific pH and ionic strength, and the mixture was rigorously shaken. The extracts were centrifuged; then, the organic phase (acetonitrile) was transferred to a test tube and was mixed with deionised water. The mixture was sonicated and chloroform was added as an acceptor phase...
Evaluation of partial least-squares regression with multivariate analytical figures of merit for determination of 10 pesticides in milk
, Article International Journal of Environmental Analytical Chemistry ; Volume 102, Issue 8 , 2022 , Pages 1900-1910 ; 03067319 (ISSN) ; Balsini, P ; Parastar, H ; Sharif University of Technology
Taylor and Francis Ltd
2022
Abstract
A multi-residue method using gas chromatography coupled with flame ionisation detector has been developed for simultaneous determination of 10 pesticides in milk. The methodology involved a sample clean-up procedure using ‘quick, easy, cheap, effective, rugged and safe’ followed by a preconcentration step based on dispersive liquid–liquid microextraction. In this regard, acetonitrile was added to the milk sample with specific pH and ionic strength, and the mixture was rigorously shaken. The extracts were centrifuged; then, the organic phase (acetonitrile) was transferred to a test tube and was mixed with deionised water. The mixture was sonicated and chloroform was added as an acceptor phase...
Simultaneous Analysis of Aliphatic Alcohols Mixtures Using an Electronic Nose Based on Nano/Microstructured Conducting Polypyrrole Film Prepared by Catalytic Electropolymerization on Cu/Au Interdigital Electrodes Using Multivariate Calibration
, Article IEEE Sensors Journal ; Volume 16, Issue 2 , 2016 , Pages 418-425 ; 1530437X (ISSN) ; Babaei, M ; Alizadeh, M. S ; Mani Varnosfaderani, A ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
Abstract
In this paper, nano/microstructured-conducting polypyrrole has been prepared on Cu/Au interdigital electrode surfaces by using constant potential amperometry technique. The Fe(II) ions were used as catalyst and X = ClO4 -, pTs-, Cl-, TCA-, DS-, DBS- was implemented as anion dopants. The morphologies of the films were investigated by field emission scanning electron microscope. A remarkable dependence was observed between the type of anion dopant and the morphology of polypyrrole (PPy). The sensing behavior of the PPy-X sensor has been studied toward acetone, methanol, ethanol, 1-propanol, 2-propanol, nitromethane, propylamine, pyridine, and gas mixtures of aliphatic alcohols. The responses...
Polynomial datapath optimization using partitioning and compensation heuristics
, Article Proceedings - Design Automation Conference, 26 July 2009 through 31 July 2009, San Francisco, CA ; 2009 , Pages 931-936 ; 0738100X (ISSN); 9781605584973 (ISBN) ; Alizadeh, B ; Fujita, M ; Sharif University of Technology
2009
Abstract
Datapath designs that perform polynomial computations over Z 2n are used in many applications such as computer graphics and digital signal processing domains. As the market of such applications continues to grow, improvements in high-level synthesis and optimization techniques for multivariate polynomials have become really challenging. This paper presents an efficient algorithm for optimizing the implementation of a multivariate polynomial over Z2n in terms of the number of multipliers and adders. This approach makes use of promising heuristics to extract more complex common sub-expressions from the polynomial compared to the conventional methods. The proposed algorithm also utilizes a...
Nonlinear dynamics and control of bifurcation to regulate the performance of a boiler-turbine unit
, Article Energy Conversion and Management ; Vol. 68 , 2013 , pp. 105-113 ; ISSN: 01968904 ; Alasty, A ; Vossoughi, G ; Sharif University of Technology
Abstract
The economical operations of power plants and environmental awareness are the major factors affecting the importance of control in boiler-turbine units. In this paper, a multivariable nonlinear model of boiler-turbine unit is considered. Drum pressure, electric output and water level of drum (as output variables) are adjusted at desired values by manipulation of valve positions for fuel, steam and feed-water flow rates (as input variables). Nonlinear dynamics of the unit is investigated through the concepts of bifurcation and limit cycles behaviour. In the presence of harmonic disturbances, some coefficients of the dynamic model, fuel and steam flow rates play as the bifurcation parameters....
Nonlinear dynamics and control of bifurcation to regulate the performance of a boiler-turbine unit
, Article Energy Conversion and Management ; Volume 68 , 2013 , Pages 105-113 ; 01968904 (ISSN) ; Alasty, A ; Vossoughi, G ; Sharif University of Technology
2013
Abstract
The economical operations of power plants and environmental awareness are the major factors affecting the importance of control in boiler-turbine units. In this paper, a multivariable nonlinear model of boiler-turbine unit is considered. Drum pressure, electric output and water level of drum (as output variables) are adjusted at desired values by manipulation of valve positions for fuel, steam and feed-water flow rates (as input variables). Nonlinear dynamics of the unit is investigated through the concepts of bifurcation and limit cycles behaviour. In the presence of harmonic disturbances, some coefficients of the dynamic model, fuel and steam flow rates play as the bifurcation parameters....
Linear multi-variable control technique for smart power management of wind turbines
, Article 2012 International Conference onAdvanced Mechatronic Systems, ICAMechS 2012 ; 2012 , Pages 559-564 ; 9780955529382 (ISBN) ; Banazadeh, A ; Sharif University of Technology
2012
Abstract
Variable speed wind turbines are widely used in the modern power industry. These turbines that are usually driven by doubly fed induction generators (DFIG) contain two groups of controlling variables; mechanical variables like pitch angle, and electrical variables like rotor voltage. During the turbine operation, with variable wind speed, power must be managed in two different regimes; power optimization and power limitation. In the current research, initially a non-linear simulation, based on the general wind turbine dynamic model is presented. Then, the desired controllers for both pitch angle and generator voltage components are constructed. To validate turbine behavior and controller...