Search for: nonlinear-systems
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    Robust tracking control of attitude satellite with using new EKF for large rotational maneuvers

    , Article AIAA Guidance, Navigation, and Control Conference and Exhibit 2003, Austin, TX, 11 August 2003 through 14 August 2003 ; 2003 ; 9781563479786 (ISBN); 9781624100901 (ISBN) Jafarboland, M ; Sadati, N ; Momeni, H ; Sharif University of Technology
    American Institute of Aeronautics and Astronautics Inc  2003
    Control of a class of uncertain nonlinear systems which estimates unavailable state variables is considered. A new approach for robust tracking control problem of satellite for large rotational maneuvers is presented in this paper. The features of this approach include -a strong algorithm to estimate attitude, based on discrete extended kalman filter combined with a continuous extended kalman filter and attitude nonlinear model -a robust controller based on slidingmode with perturbation estimation. The estimation result of interval kalman filtering is a sequence of interval estimates that encompasses all possible optimal attitude estimates, which the interval system may generate. The... 

    Structural and electronic properties of YBa2Cu3O 7 and YSr2Cu3O7 under mechanical and strontium chemical pressures

    , Article Physical Review B - Condensed Matter and Materials Physics ; Volume 70, Issue 13 , 2004 , Pages 134509-1-134509-9 ; 01631829 (ISSN) Khosroabadi, H ; Mossalla, B ; Akhavan, M ; Sharif University of Technology
    Calculations of structural and electronic properties of two YBa 2Cu3O7 (YBCO) and YSr2Cu 3O7 (YSCO) high-Tc cuprate isofamilies for ambient and high mechanical pressures (-15 GPa≤pm≤15 GPa) have been carried out by pseudopotential density functional theory in the local density approximation employing VASP code. We have analyzed the changes of bond lengths and equilibrium ionic positions due to mechanical pressure on YBCO and YSCO. Negative pressure causes separation of the YBCO unit cell into Cu(1)-O(1)-O(4) and CuO2-Y-CuO2 blocks, similar to the effect of oxygen reduction in YBCO. We have also found that the nonlinear dependence for ionic positions by mechanical pressure, especially for... 

    On identification of nonlinear systems using volterra kernels expansion on Laguerre and wavelet function

    , Article 2010 Chinese Control and Decision Conference, CCDC 2010, 26 May 2010 through 28 May 2010, Xuzhou ; 2010 , Pages 1141-1145 ; 9781424451821 (ISBN) Moodi, H ; Bustan, D ; Sharif University of Technology
    Application of Volterra series to the modeling of static and dynamic nonlinear systems is investigated in this paper and compared to other methods. For nonlinear systems with memory, Volterra series serves as a generalization of convolution integral. To parameterize the Volterra kernels for limited dimension series, different methods are discussed. We use Laguerre functions and wavelet packets as orthonormal basis and we find the poles for the basis through a genetic algorithm search. Our test system is a hydraulic actuator with a highly nonlinear dynamics which is modeled with Volterra series. The results show that dynamic model with wavelet packets give a more accurate model with respect... 

    Some computable results on the existence of periodic solutions for singular non-autonomous third order systems

    , Article Applied Mathematics and Computation ; Volume 163, Issue 1 , 2005 , Pages 51-60 ; 00963003 (ISSN) Mehri, B ; Niksirat, M. A ; Sharif University of Technology
    Here we are concerned with the existence of periodic solution for nonlinear non-autonomous third order system of ordinary differential equations with singular terms. Our method here is based on the topological method in the sense that we conclude some computable results for the focal system from a homotopic nonsingular system. The aim is to obtain sufficient conditions for which the system has periodic solution whenever the value of deformation with respect to the first variation of the nonsingular subsystem is sufficiently small. The method presented here is constructive in the sense that the existence of periodic orbits can be verified numerically as well as computed if any. For this, we... 

    Steady-State Operability Analysis of Nonlinear Plants Using Output Controllability Index

    , M.Sc. Thesis Sharif University of Technology Moradpanah, Maryam (Author) ; Pishvaie, Mahmoud Reza (Supervisor)
    Selecting an appropriate control structure is an important subject in the design of control systems. Distillation column is one of the most popular and widely used unit operations in industry which complete understanding of its operability and controllability is one of the most important issues in the process control engineering. The present work studies the method of Output Controllability Index for nonlinear systems and compares it with Relative Gain Array and Condition Number. By using this index, the extent of intrinsic controllability of a process can be identified quantitatively in the absence of any controller. Also, the controllability of the process can be stated numerically or... 

    Decentralized adaptive control of large-scale affine and nonaffine nonlinear systems

    , Article IEEE Transactions on Instrumentation and Measurement ; Volume 58, Issue 8 , 2009 , Pages 2459-2467 ; 00189456 (ISSN) Karimi, B ; Menhaj, M. B ; Karimi Ghartemani, M ; Saboori, I ; Sharif University of Technology
    This paper presents a decentralized adaptive control design for a class of large-scale nonlinear systems with unknown subsystems. When the subsystems are modeled by affine equations, a direct adaptive controller is devised based on the Lyapunov theory, so that the stability of the closed-loop system is guaranteed by introducing a suitably driven adaptive rule. A neuro-based structure is proposed when the subsystems are nonaffine, and the stability analysis is also performed based on the Lyapunov theory. Moreover, the unknown interactions among the subsystems are considered as having a nonlinear function against the simple form considered for the affine case. The proposed controllers are... 

    Design and construction of a fine drive system for scanning optical elements

    , Article Optics and Laser Technology ; Volume 40, Issue 6 , 2008 , Pages 803-808 ; 00303992 (ISSN) Golnabi, H ; Jafari, R ; Sharif University of Technology
    The design and operation of a simple mechanical drive system, which is able to perform a fine course of angular motion, are reported. The system consists of a lead screw, a drive nut, sine bar legs, and an output shaft that can scan the optical holder mount. With a stepper motor coupled to the lead screw and interfaced to a PC, it is possible to control the scanning operation. When a 800 step/turn motor is used, it is possible to have an angular resolution of about 0.5 mdegree for a dynamic range of about 23°. The reproducibility of the results is about 0.22% for the scan angle and the hysteresis effect of the system is in the range of 1.71%. For a total scan of 51,200 steps, a scan angle of... 

    Stochastic control of two-level nonlinear large-scale systems; Part II-Interaction balance principle

    , Article 2006 IEEE International Conference on Systems, Man and Cybernetics, Taipei, 8 October 2006 through 11 October 2006 ; Volume 5 , 2006 , Pages 3856-3861 ; 1062922X (ISSN); 1424401003 (ISBN); 9781424401000 (ISBN) Sadati, N ; Dehghan Marvast, E ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2006
    In this paper a new two-level method for stochastic control of large-scale systems is presented. This two-level approach is based on Interaction Balance Principle (Goal coordination) for optimization problem and a two-level computational algorithm using extended Kalman filter for the estimation one. The two-level optimizer uses a new coordinator which works by the gradient of interaction errors that improves the convergence rate of the solution. The significance and the applicability of the theoretical developments of this paper are also shown by a numerical example. © 2006 IEEE  

    Saturation and its application in the vibration control of nonlinear systems

    , Article Proceedings of the 7th Biennial Conference on Engineering Systems Design and Analysis - 2004, Manchester, 19 July 2004 through 22 July 2004 ; Volume 2 , 2004 , Pages 93-100 ; 0791841731 (ISBN); 9780791841730 (ISBN) Shoeybi, M ; Ghorashi, M ; Sharif University of Technology
    American Society of Mechanical Engineers  2004
    An investigation on the nonlinear vibrations of a system with two degrees of freedom when subjected to saturation is presented. The method is especially applied to a system that consists of a DC motor with a nonlinear controller and subjected to a harmonic forcing voltage. Approximate solutions are sought using the method of multiple scales. Also, singular point analysis is used to study stability of solutions. These findings are then compared with the corresponding numerical results. Good agreement between the two is observed  

    Static feedback versus fractionality of the electrical elements in the Van der Pol circuit

    , Article Nonlinear Dynamics ; Volume 72, Issue 1-2 , 2013 , Pages 365-375 ; 0924090X (ISSN) Tavakoli Kakhki, M ; Tavazoei, M. S ; Sharif University of Technology
    In this paper, it is shown that by benefiting from a static feedback control signal it is possible to reduce the effect of fractionality of the electrical capacitors on the amplitude of the oscillations produced by a Van der Pol circuit. The averaging method is used in this paper for the behavior analysis of the approximated responses of the under study circuits. Numerical simulation results are presented to confirm the effectiveness of the proposed control technique  

    Fuzzy equations and Z-numbers for nonlinear systems control

    , Article 9th International Conference on Theory and Application of Soft Computing, Computing with Words and Perception, ICSCCW 2017, 22 August 2017 through 23 August 2017 ; Volume 120 , 2017 , Pages 923-930 ; 18770509 (ISSN) Razvarz, S ; Tahmasbi, M ; Sharif University of Technology
    Elsevier B.V  2017
    Various systems with nonlinearity can be modeled by utilizing uncertain linear-in-parameter models. In this paper, the uncertain parameters are in the form of Z-number coefficients. Fuzzy equations are utilized to represent the models of the uncertain nonlinear systems. The solutions associated with fuzzy equations are considered to be controllers while the desired references are outputs. The existence condition associated with the solution is laid down. Two various structure of neural networks are applied for approximating solutions of fuzzy equations with Z-number coefficients. The suggested techniques are validated by implementing an example. © 2018 The Authors. Published by Elsevier B.V  

    Computational load reduction in model predictive control of nonlinear systems via decomposition

    , Article 5th International Conference on Control, Instrumentation, and Automation, ICCIA 2017, 21 November 2017 through 23 November 2017 ; Volume 2018-January , 2018 , Pages 216-221 ; 9781538621349 (ISBN) Adelipour, S ; Rastgar, M ; Haeri, M ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2018
    The aim of this study is to reduce the computational load in model predictive control of multi-input nonlinear systems. First, the nonlinear system which has a high number of states and inputs is decomposed into several subsystems by solving a linear integer programming problem offline. Then, the model of each subsystem is revised by considering the effect of coupling and interactions of other subsystems. Next, the robust model predictive technique based on linear matrix inequalities is employed to compute control signal for each subsystem. An industrial chemical reaction example is used to illustrate the effectiveness of the proposed method. © 2017 IEEE  

    Instability of nanocantilever arrays in electrostatic and van der waals interactions

    , Article Journal of Physics D: Applied Physics ; Volume 42, Issue 22 , 2009 ; 00223727 (ISSN) Ramezani, A ; Alasty, A ; Sharif University of Technology
    The structural instability of an array of cantilevers, each of which interacts with two neighbouring beams through electrostatic and van der Waals forces, is studied. Distributed and lumped parameter modelling of the array result in a set of coupled nonlinear boundary value problems and a set of coupled nonlinear equations, respectively. These coupled nonlinear systems are solved numerically for different numbers of beams in the array to obtain the pull-in parameters. The pull-in parameters converge to constant values with an increase in the number of beams in the array. These constants, which are important in the design of cantilever arrays, are compared for the distributed and lumped... 

    A cascade multiple-model predictive controller of nonlinear systems by integrating stability and performance

    , Article 27th Iranian Conference on Electrical Engineering, ICEE 2019, 30 April 2019 through 2 May 2019 ; 2019 , Pages 951-955 ; 9781728115085 (ISBN) Rikhtehgar, P ; Ahmadi, M ; Haeri, M ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2019
    To deal with strong nonlinearity in nonlinear systems, a new method called cascade multiple-model predictive controller based on gap metric and stability margin, is proposed. The gap metric is utilized to describe the nonlinear system by a linear model bank. It is possible to select nominal local models from the linear model bank by an algorithm based on the gap metric and stability margin to avoid the redundancy of the local controllers. By scheduling proportional controller for each nominal local model, the robust stability is guaranteed whereas there will be no guarantee for the desired performance. Then, by designing a model predictive controller in the cascade structure, the closed loop... 

    Control of Unknown Control Direction System

    , M.Sc. Thesis Sharif University of Technology Hosseini Ardali, Mohsen (Author) ; Shahrokhi, Mohammad (Supervisor)
    This research is trying to investigate the control algorithms of unknown control direction systems. Since Nussbaum function is the most common method which in used for these systems this research focus on this algorithm to overcome control the effect of unknown control direction. This research study the performance of different control algorithms in controlling such systems followed by analysis of two control modes of continuous and discrete using Nussbam Function. Additionally, in continuous mode, the performance of two methods of backstepping and liding mode has been compared on the given system in variety of situation. Results demonstrate that backstepping method shows better performance... 

    An Analysis of a Mathematical Model Describing the Geographic Spread of Dengue Disease

    , M.Sc. Thesis Sharif University of Technology Hashemifar, Alireza (Author) ; Hesaraki, Mahmoud (Supervisor)
    We consider a system of nonlinear partial differential equations corresponding to a generalization of a mathematical model for geographical spreading of dengue disease. the mosquito population is divided into subpopulations: winged form (mature female mosquitoes) and aquatic form (comprising eggs, larvae and pupae); the human population is divided into the subpopulations:susceptible, infected and removed (or immune). On the other hand we allow higher spatial dimensions and also parameters depending on space and time. is last generalization is done to cope with possible abiotic effects as variations in temperature, humidity, wind velocity, carrier capacities, and so on; thus, the results... 

    A New Method for Suboptimal Control of a Class of Non-Linear Systems

    , M.Sc. Thesis Sharif University of Technology Dehghan, Ali Reza (Author) ; Hesaaraki, Mahmoud (Supervisor)
    In this thesis, a new non-linear control synthsis technique (θ - D) approximation) is discussed. This approach achieves suboptimal solutions to a class of non-linear optimal control problems characterized by a quadratic cost function and a plant model that is a_ne in control. An approximate solution to the Hamilton-Jacobi-Bellman (HJB) equation is sought by adding perturbations to the cost function. By manipulating the perturbation terms both asymptotic stability and suboptimality properties are obtained. The new technique overcomes the large-control-for-large-initial-states problem that occurs in some other Taylor series expansion based methods. Also this method does not require excessive... 

    Integrated guidance and control of elastic flight vehicle based on robust MPC

    , Article International Journal of Robust and Nonlinear Control ; 2014 Shamaghdari, S ; Nikravesh, S. K. Y ; Haeri, M ; Sharif University of Technology
    Integrated guidance and control of an elastic flight vehicle based on constrained robust model predictive control is proposed. The design is based on a partial state feedback control law that minimizes a cost function within the framework of linear matrix inequalities. It is shown that the solution of the defined optimization problem stabilizes the nonlinear plant. Nonlinear kinematics and dynamics are taken into account, and internal stability of the closed-loop nonlinear system is guaranteed. The performance and effectiveness of the proposed integrated guidance and control against non-maneuvering and weaving targets are evaluated using computer simulations  

    Prediction of inter-modulation rejection values for the first and second adjacent channels in feed-forward linearised microwave amplifiers using closed-form expressions

    , Article IET Microwaves, Antennas and Propagation ; Volume 1, Issue 3 , 2007 , Pages 782-789 ; 17518725 (ISSN) Hemmatyar, A. M. A ; Farzaneh, F ; Sharif University of Technology
    Feed-forward is one of the main methods for linearising microwave power amplifiers. The level of inter-modulation rejection (IMR) values can be predicted by appropriate modelling of the feed-forward microwave amplifier. Here, we have presented closed form expressions, which can be used for predicting the IMR for the first and second adjacent channels. Fifth- and third-order nonlinear models have been used for the main and error amplifiers, respectively. The predicted values have been verified using ADS simulator and a MATLAB program. © The Institution of Engineering and Technology 2007  

    Compact basis free relations for stress tensors conjugate to Hill's strain measures

    , Article 8th Biennial ASME Conference on Engineering Systems Design and Analysis, ESDA2006, Torino, 4 July 2006 through 7 July 2006 ; Volume 2006 , 2006 ; 0791837793 (ISBN); 9780791837795 (ISBN) Naghdabadi, R ; Asghari, M ; Ghavam, K ; Sharif University of Technology
    American Society of Mechanical Engineers  2006
    If the double contraction of a stress tensor such as T and rate of a Lagrangean strain tensor such as E, i.e. T : Ė produces the stress power then these stress and strain tensors are called a conjugate pair. The applications of the conjugate stress and strain measures are in the development of the basic relations in nonlinear continuum mechanics analysis such as modeling of constitutive equations of elastic-plastic materials. In this paper relations for stress tensors conjugate to an arbitrary Lagrangean strain measure of Hill's class are obtained. The results of this paper are more compact and simpler in compare with those available in the literature. The results are valid for the three...