Loading...
Search for:
unknown-parameters
0.005 seconds
Adaptive synchronization of two different chaotic systems with time varying unknown parameters
, Article Chaos, Solitons and Fractals ; Volume 37, Issue 1 , 2008 , Pages 125-136 ; 09600779 (ISSN) ; Shahrokhi, M ; Sharif University of Technology
2008
Abstract
In this paper a nonlinear control method based on Lyapunov stability theorem is proposed to design an adaptive controller for synchronizing two different chaotic systems. It is assumed that the unknown parameters of the drive and the response chaotic systems are time varying. It is shown that the proposed scheme can identify the system parameters if the system parameters are time invariant and the richness conditions is satisfied. To demonstrate the effectiveness of the proposed technique it has been applied to Lorenz-Chen dynamic systems, as drive-response systems. Simulation results indicate that the proposed adaptive controller has a high performance in synchronizing two chaotic systems....
Application of particle swarm optimization in chaos synchronization in noisy environment in presence of unknown parameter uncertainty
, Article Communications in Nonlinear Science and Numerical Simulation ; Volume 17, Issue 2 , 2012 , Pages 742-753 ; 10075704 (ISSN) ; Vatankhah, R ; Boroushaki, M ; Salarieh, H ; Alasty, A ; Sharif University of Technology
Abstract
In this paper, particle swarm optimization (PSO) is applied to synchronize chaotic systems in presence of parameter uncertainties and measurement noise. Particle swarm optimization is an evolutionary algorithm which is introduced by Kennedy and Eberhart. This algorithm is inspired by birds flocking. Optimization algorithms can be applied to control by defining an appropriate cost function that guarantees stability of system. In presence of environment noise and parameter uncertainty, robustness plays a crucial role in succeed of controller. Since PSO needs only rudimentary information about the system, it can be a suitable algorithm for this case. Simulation results confirm that the proposed...
The simultaneous determination of archie's parameters by application of modified genetic algorithm and hdp methods: A comparison with current methods via two case studies
, Article Petroleum Science and Technology ; Volume 30, Issue 1 , Mar , 2011 , Pages 54-63 ; 10916466 (ISSN) ; Najafi, I ; Najafi, A ; Ghazanfari, M. H ; Sharif University of Technology
2011
Abstract
Although different procedures have been proposed to calculate the parameters of Archie's (1942) equation, most of them suffer from lack of accuracy because these are not solved simultaneously In this article, by applying two novel methods, a modified genetic algorithm (MGA) and homogeneous distribution of parameters (HDP), the above-mentioned unknown parameters were determined simultaneously. Furthermore, for two case studies using two data sets from Permian Glerito and Permian Clearfork reservoirs, a comparison is made between other methods (e.g., traditional graphical method and SmnaM; Frailey et al., 2001) and the proposed methods that demonstrated the greater accuracy of the two newly...
Application of the homotopy perturbation method to linear and nonlinear fourth-order boundary value problems
, Article Physica Scripta ; Volume 77, Issue 5 , 2008 ; 00318949 (ISSN) ; Rasi Marzabadi, F ; Farjami, Y ; Sharif University of Technology
2008
Abstract
In this study, we applied the homotopy perturbation (HP) method for solving linear and nonlinear fourth-order boundary value problems. The analytical results of the boundary value problems have been obtained in terms of a convergent series with easily computable components. Comparisons between the results of the HP method and the analytical solution showed that this method gives very precise results with a few terms. In the implied HP method, some unknown parameters in the initial guess are introduced, which are identified after applying boundary conditions. This improvement results in higher accuracy. © 2008 The Royal Swedish Academy of Sciences
Modeling catalyst deactivation in dehydrogenation of ethylbenzene to styrene
, Article AIChE Annual Meeting, Conference Proceedings, 13 March 2011 through 17 March 2011 ; March , 2011 ; 9780816910670 (ISBN) ; Baghalha, M ; Sharif University of Technology
Abstract
Long-term deactivation of a commercial K-promoted Fe 2O 3 catalyst used in the dehydrogenation of ethylbenzene to styrene monomer was studied using 30 months of operating data of three industrial SM radial fixed bed adiabatic reactors. The Langmuir-Hinshelwood, Hougen-Watson model (LHHW) was used for reaction kinetics modeling. The kinetics of coking from ethylbenzene and styrene and the short-term deactivation function due to the quick coke formation were also considered in the model. The kinetics of long-term deactivation of the catalyst for ethylbenzene dehydrogenation to styrene between 550 and 630 °C were determined by allowing the effects of temperature and time on the catalyst...
Invariant activity detection of a constant magnitude signal with unknown parameters in white Gaussian noise
, Article IET Communications ; Volume 3, Issue 8 , 2009 , Pages 1420-1431 ; 17518628 (ISSN) ; Tadaion, A. A ; Gazor, S ; Nayebi, M. M ; Sharif University of Technology
2009
Abstract
The authors propose invariant tests for the detection of a complex signal with unknown constant amplitude and unknown phase variation in additive white Gaussian noise (AWGN). The authors show that in this problem, the uniformly most powerful invariant (UMPI) detector does exist only if the number of samples N is two. For more than two samples N≥3, the authors derive the most powerful invariant (MPI) detector in known signal-to-noise ratio (SNR) and use its performance as the upper bound benchmark for any invariant test. In addition, the authors derive the generalised likelihood ratio (GLR) detector and evaluate its performance against the MPI performance bound. This detector is very simple...
Assessing dynamic response of multispan viscoelastic thin beams under a moving mass via generalized moving least square method
, Article Acta Mechanica Sinica/Lixue Xuebao ; Volume 26, Issue 5 , October , 2010 , Pages 721-733 ; 05677718 (ISSN) ; Nikkhoo, A ; Mehri, B ; Sharif University of Technology
Abstract
Dynamic response of multispan viscoelastic thin beams subjected to a moving mass is studied by an efficient numerical method in some detail. To this end, the unknown parameters of the problem are discretized in spatial domain using generalized moving least square method (GMLSM) and then, discrete equations of motion based on Lagrange's equation are obtained. Maximum deflection and bending moments are considered as the important design parameters. The design parameter spectra in terms of mass weight and velocity of the moving mass are presented for multispan viscoelastic beams as well as various values of relaxation rate and beam span number. A reasonable good agreement is achieved between...
Adaptive synchronization of two chaotic systems with stochastic unknown parameters
, Article Communications in Nonlinear Science and Numerical Simulation ; Volume 14, Issue 2 , 2009 , Pages 508-519 ; 10075704 (ISSN) ; Alasty, A ; Sharif University of Technology
2009
Abstract
Using the Lyapunov stability theory an adaptive control is proposed for chaos synchronization between two different systems which have stochastically time varying unknown coefficients. The stochastic variations of the coefficients about their unknown mean values are modeled through white Gaussian noise produced by the Weiner process. It is shown that using the proposed adaptive control the mean square of synchronization error converges to an arbitrarily small bound around zero. To demonstrate the effectiveness of the proposed technique, it is applied to the Lorenz-Chen and the Chen-Rossler dynamical systems, as some case studies. Simulation results indicate that the proposed adaptive...
Parametric analyses of multispan viscoelastic shear deformable beams under excitation of a moving mass
, Article Journal of Vibration and Acoustics, Transactions of the ASME ; Volume 131, Issue 5 , 2009 , Pages 0510091-05100912 ; 10489002 (ISSN) ; Nikkhoo, A ; Mehri, B ; Sharif University of Technology
2009
Abstract
This paper presents a numerical parametric study on design parameters of multispan viscoelastic shear deformable beams subjected to a moving mass via generalized moving least squares method (GMLSM). For utilizing Lagrange's equations, the unknown parameters of the problem are stated in terms of GMLSM shape functions and the generalized Newmark-β scheme is applied for solving the discrete equations of motion in time domain. The effects of moving mass weight and velocity, material relaxation rate, slenderness, and span number of the beam on the design parameters and possibility of mass separation from the base beam are scrutinized in some detail. The results reveal that for low values of beam...
Satellite attitude control using three reaction wheels
, Article 2008 American Control Conference, ACC, Seattle, WA, 11 June 2008 through 13 June 2008 ; 2008 , Pages 4850-4855 ; 07431619 (ISSN) ; 9781424420797 (ISBN) ; Farooq, U ; Alasty, A ; Issa, J ; Sharif University of Technology
2008
Abstract
This work addresses the attitude control of a satellite by applying MIMO quantitative feedback approach. The objective is to design a set of proper controllers in presence of unknown disturbances and parametric uncertainties for a nonlinear MIMO system. The physical model of satellite utilizes three reaction wheels as actuators. The controller goal is to change the rotational speed of reaction wheels to adjust the satellite in desired course. First, the mathematical model of satellite and its actuators using angular kinematics and kinetic equations is developed. Quantitative feedback theory is then applied to synthesize a set of linear controllers that deals with both nonlinearities in the...
Geometry control of the deposited layer in a nonplanar laser cladding process using a variable structure controller
, Article Journal of Manufacturing Science and Engineering, Transactions of the ASME ; Volume 130, Issue 3 , 2008 , Pages 0310031-03100311 ; 10871357 (ISSN) ; Khajepour, A ; Durali, M ; Toyserkani, E ; Sharif University of Technology
2008
Abstract
This paper presents a closed-loop laser cladding process used in nonplanar deposition of desired metallic materials. In the proposed system, the deposited layer geometry is continuously controlled via a sliding mode controller (SMC). The controller, which uses the scanning speed as the control input, is designed based on a parametric Hammerstein model. The model is a parametric dynamic model with several unknown parameters, which are identified experimentally using the recursive least squares method. The designed SMC is robust to all model parameters' uncertainties and disturbances. The results showed that the tracking accuracy improves and the chattering effect reduces if an integrator on...
A new non-linear algorithm for complete pre-flight calibration of magnetometers in the geomagnetic field domain
, Article Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering ; Volume 223, Issue 6 , 2009 , Pages 729-739 ; 09544100 (ISSN) ; Pourtakdoust, S. H ; Samani, M ; Sharif University of Technology
2009
Abstract
A new algorithm for complete pre-flight calibration of triple magnetometers is developed. The traditional approach for calibrating these sensors are based on a cumbersome procedure called 'swing' that involves levelling and rotating the vehicle containing the magnetometers through a series of known headings. Application of such a procedure is difficult and costly. Recently, new approaches have been developed to calibrate magnetometers without the need of attitude information. Such methods are used mostly for the calibration of biases and scale factors. Additionally in situations where misalignment errors are also to be estimated, they are usually modelled as errors of a non-orthogonal frame...
Structured multiblock body-fitted grids solution of transient inverse heat conduction problems in an arbitrary geometry
, Article Numerical Heat Transfer, Part B: Fundamentals ; Volume 54, Issue 3 , July , 2008 , Pages 260-290 ; 10407790 (ISSN) ; Kazemzadeh Hannani, S ; Farhanieh, B ; Sharif University of Technology
2008
Abstract
The aim of this study is to develop iterative regularization algorithms based on parameter and function estimation techniques to solve two-dimensional/axisymmetric transient inverse heat conduction problems in curvilinear coordinate system. The multiblock method is used for geometric decomposition of the physical domain into regions with patched-overlapped interface grids. The central finite-difference version of the alternating-direction implicit technique together with structured body-fitted grids is implemented for numerical solution of the direct problem and other partial differential equations derived by inverse analysis. The approach of estimating unknown parameters and functions is...