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    Reference tracking of nonlinear dynamic systems over AWGN channel using the describing function

    , Article Scientia Iranica ; Volume 26, Issue 3 D , 2019 , Pages 1724-1735 ; 10263098 (ISSN) Parsa, A ; Farhadi, A ; Sharif University of Technology
    Sharif University of Technology  2019
    Abstract
    This paper presents a new technique for mean square asymptotic reference tracking of nonlinear dynamic systems over Additive White Gaussian Noise (AWGN) channel. The nonlinear dynamic system has periodic outputs and sinusoidal inputs and is cascaded with a bandpass filter acting as an encoder. By using the describing function method, the nonlinear dynamic system is represented by an equivalent linear dynamic system. Then, for this system, a mean square asymptotic reference tracking technique, including an encoder, a decoder, and a controller, is presented. It is shown that the proposed reference tracking technique results in mean square asymptotic reference tracking of nonlinear dynamic... 

    Reference tracking of nonlinear dynamic systems over AWGN channel using the describing function

    , Article Scientia Iranica ; Volume 26, Issue 3 D , 2019 , Pages 1724-1735 ; 10263098 (ISSN) Parsa, A ; Farhadi, A ; Sharif University of Technology
    Sharif University of Technology  2019
    Abstract
    This paper presents a new technique for mean square asymptotic reference tracking of nonlinear dynamic systems over Additive White Gaussian Noise (AWGN) channel. The nonlinear dynamic system has periodic outputs and sinusoidal inputs and is cascaded with a bandpass filter acting as an encoder. By using the describing function method, the nonlinear dynamic system is represented by an equivalent linear dynamic system. Then, for this system, a mean square asymptotic reference tracking technique, including an encoder, a decoder, and a controller, is presented. It is shown that the proposed reference tracking technique results in mean square asymptotic reference tracking of nonlinear dynamic... 

    Open synchronous cellular learning automata

    , Article Advances in Complex Systems ; Volume 10, Issue 4 , 2007 , Pages 527-556 ; 02195259 (ISSN) Beigy, H ; Meybodi, M. R ; Sharif University of Technology
    World Scientific Publishing Co. Pte Ltd  2007
    Abstract
    Cellular learning automata is a combination of learning automata and cellular automata. This model is superior to cellular learning automata because of its ability to learn and also is superior to single learning automaton because it is a collection of learning automata which can interact together. In some applications such as image processing, a type of cellular learning automata in which the action of each cell in the next stage of its evolution not only depends on the local environment (actions of its neighbors) but it also depends on the external environments. We call such a cellular learning automata as open cellular learning automata. In this paper, we introduce open cellular learning... 

    Comparison of kane's and lagrange's methods in analysis of constrained dynamical systems

    , Article Robotica ; Volume 38, Issue 12 , 2020 , Pages 2138-2150 Talaeizadeh, A ; Forootan, M ; Zabihi, M ; Nejat Pishkenari, H ; Sharif University of Technology
    Cambridge University Press  2020
    Abstract
    Dynamic modeling is a fundamental step in analyzing the movement of any mechanical system. Methods for dynamical modeling of constrained systems have been widely developed to improve the accuracy and minimize computational cost during simulations. The necessity to satisfy constraint equations as well as the equations of motion makes it more critical to use numerical techniques that are successful in decreasing the number of computational operations and numerical errors for complex dynamical systems. In this study, performance of a variant of Kane's method compared to six different techniques based on the Lagrange's equations is shown. To evaluate the performance of the mentioned methods,... 

    Passive dynamic object manipulation: A framework for passive walking systems

    , Article Proceedings of the Institution of Mechanical Engineers, Part K: Journal of Multi-body Dynamics ; Volume 227, Issue 2 , 2013 , Pages 185-198 ; 14644193 (ISSN) Beigzadeh, B ; Meghdari, A ; Sohrabpour, S ; Sharif University of Technology
    2013
    Abstract
    In this study, we deal with passive dynamic object manipulation. During passive dynamic object manipulation, a passive object is manipulated using passive manipulators. Like other passive robotic systems, there are no actuators in these systems. The object follows a path and travels along it under the effect of its own weight, as well as, the interaction force applied by each manipulator on it. The objects are not necessarily rigid, but we manipulate passive multibody objects as well as rigid ones. Thus, for a passive walking system, we assume that the passive walker is a multibody object and is manipulated by the ground (zero degree-of-freedom manipulator). As an example, we show that a... 

    Adaptive leader-following consensus in multi-agent systems with second-order nonlinear dynamics and directed switching topologies

    , Article 8th International Conference on Electrical and Electronics Engineering, ELECO 2013, Bursa, 28 November 2013 through 30 November 2013 ; 2013 , Pages 482-486 ; 9786050105049 (ISBN) Atrianfar, H ; Haeri, M ; Sharif University of Technology
    IEEE Computer Society  2013
    Abstract
    In this paper, we develop control algorithms for addressing second-order consensus problems in intrinsically second-order nonlinear multi-agent dynamical systems with switching topologies. The proposed adaptive controller applies a leader-following strategy in which all agents are assumed to be informed of the leader's state. Another feature of this work which specifically distinguishes it from others is that the proposed controller uses undirected and directed graphs to accommodate for a full range of possible graph information topologies without limitations of bidirectional communication  

    On the existence of periodic solutions in time-invariant fractional order systems

    , Article Automatica ; Volume 47, Issue 8 , 2011 , Pages 1834-1837 ; 00051098 (ISSN) Yazdani, M ; Salarieh, H ; Sharif University of Technology
    2011
    Abstract
    Periodic solutions and their existence are one of the most important subjects in dynamical systems. Fractional order systems like integer ones are no exception to this rule. Tavazoei and Haeri (2009) have shown that a time-invariant fractional order system does not have any periodic solution. In this article, this claim has been investigated and it is shown that although in any finite interval of time the solutions do not show any periodic behavior, when the steady state responses of fractional order systems are considered, periodic orbits can be detected  

    Periodic solutions for predator-prey systems with Beddington-DeAngelis functional response on time scales

    , Article Nonlinear Analysis: Real World Applications ; Volume 9, Issue 3 , 2008 , Pages 1224-1235 ; 14681218 (ISSN) Fazly, M ; Hesaaraki, M ; Sharif University of Technology
    2008
    Abstract
    This paper deals with the question of existence of periodic solutions of nonautonomous predator-prey dynamical systems with Beddington-DeAngelis functional response. We explore the periodicity of this system on time scales. New sufficient conditions are derived for the existence of periodic solutions. These conditions extend previous results presented in [M. Bohner, M. Fan, J. Zhang, Existence of periodic solutions in predator-prey and competition dynamic systems, Nonlinear. Anal.: Real World Appl. 7 (2006) 1193-1204; M. Fan, Y. Kuang, Dynamics of a nonautonomous predator-prey system with the Beddington-DeAngelies functional response, J. Math. Anal. Appl. 295 (2004) 15-39; J. Zhang, J. Wang,... 

    An Approach to Computation based on Discrete Dynamical Systems

    , M.Sc. Thesis Sharif University of Technology Dastgheib, Doratossadat (Author) ; Daneshgar, Amir (Supervisor)
    Abstract
    In this thesis, based on an idea of A. Daneshgar [On mathematical foundations of soft computing, 11th IFSC, Zahedan, Iran(2011).], we propose a general framework to model computation which is based on discrete dynamical systems. In this regard, we formulate and justify local property as the key concept characterizing computation machines within this framework. We show that our model covers most known computation machines as classical and BSS models, Petri nets, cellular automata, Markov chains and etc. . We also study the computational power of our machine based on a variant of restrictions imposed on its different components, as its memory, or its control, and we suggest that such a... 

    Radar HRRP modeling using dynamic system for radar target recognition

    , Article Radioengineering ; Vol. 23, issue. 1 , 2014 , p. 121-127 Aljorloo, A ; Hadavi, M ; Bastani, M. H ; Nayebi, M. M ; Sharif University of Technology
    Abstract
    High resolution range profile (HRRP) is being known as one of the most powerful tools for radar target recognition. The main problem with range profile for radar target recognition is its sensitivity to aspect angle. To overcome this problem, consecutive samples of HRRP were assumed to be identically independently distributed (IID) in small frames of aspect angles in most of the related works. Here, considering the physical circumstances of maneuver of an aerial target, we have proposed dynamic system which models the short dependency between consecutive samples of HRRP in segments of the whole HRRP sequence. Dynamic system (DS) is used to model the sequence of PCA (principal component... 

    GDCluster: A general decentralized clustering algorithm

    , Article IEEE Transactions on Knowledge and Data Engineering ; Volume 27, Issue 7 , 2015 , Pages 1892-1905 ; 10414347 (ISSN) Mashayekhi, H ; Habibi, J ; Khalafbeigi, T ; Voulgaris, S ; Van Steen, M ; Sharif University of Technology
    IEEE Computer Society  2015
    Abstract
    In many popular applications like peer-to-peer systems, large amounts of data are distributed among multiple sources. Analysis of this data and identifying clusters is challenging due to processing, storage, and transmission costs. In this paper, we propose GDCluster, a general fully decentralized clustering method, which is capable of clustering dynamic and distributed data sets. Nodes continuously cooperate through decentralized gossip-based communication to maintain summarized views of the data set. We customize GDCluster for execution of the partition-based and density-based clustering methods on the summarized views, and also offer enhancements to the basic algorithm. Coping with... 

    Assisted passive snake-like robots: Conception and dynamic modeling using Gibbs-Appell method

    , Article Robotica ; Volume 26, Issue 3 , 2008 , Pages 267-276 ; 02635747 (ISSN) Vossoughi, G ; Pendar, H ; Heidari, Z ; Mohammadi, S ; Sharif University of Technology
    2008
    Abstract
    In this paper, we present a novel structure of a snake-like robot. This structure enables passive locomotion in snake-like robots. Dynamic equations are obtained for motion in a horizontal plane, using Gibbs-Appell method. Kinematic model of the robot include numerous nonholonomic constraints, which can be omitted at the beginning by choosing proper coordinates to describe the model in Gibbs-Appell framework. In such a case, dynamic equations will be significantly simplified, resulting in considerable reduction of simulation time. Simulation results show that, by proper selection of initial conditions, joint angles operate in a limit cycle and robot can locomote steadily on a passive... 

    Periodic solutions for a semi-ratio-dependent predator-prey dynamical system with a class of functional responses on time scales

    , Article Discrete and Continuous Dynamical Systems - Series B ; Volume 9, Issue 2 , 2008 , Pages 267-279 ; 15313492 (ISSN) Mostafa, F ; Hesaaraki, M ; Sharif University of Technology
    2008
    Abstract
    In this paper we explore the existence of periodic solutions of a nonautonomous semi-ratio-dependent predator-prey dynamical system with functional responses on time scales. To illustrate the utility of this work, we should mention that, in our results this system with a large class of monotone functional responses, always has at least one periodic solution. For instance, this system with some celebrated functional responses such as Holling type-II (or Michaelis-Menten), Holling type-III, Ivlev, mx (Holling type I), sigmoidal [e.g., Real and mx2/((A + x)(B +x))] and some other monotone functions, has always at least one ω-periodic solution. Besides, for some well-known functional responses... 

    A comprehensive evaluation of spine kinematics, kinetics, and trunk muscle activities during fatigue-induced repetitive lifting

    , Article Human Factors ; 2021 ; 00187208 (ISSN) Kazemi, Z ; Mazloumi, A ; Arjmand, N ; Keihani, A ; Karimi, Z ; Ghasemi, M. S ; Kordi, R ; Sharif University of Technology
    SAGE Publications Inc  2021
    Abstract
    Objective: Spine kinematics, kinetics, and trunk muscle activities were evaluated during different stages of a fatigue-induced symmetric lifting task over time. Background: Due to neuromuscular adaptations, postural behaviors of workers during lifting tasks are affected by fatigue. Comprehensive aspects of these adaptations remain to be investigated. Method: Eighteen volunteers repeatedly lifted a box until perceived exhaustion. Body center of mass (CoM), trunk and box kinematics, and feet center of pressure (CoP) were estimated by a motion capture system and force-plate. Electromyographic (EMG) signals of trunk/abdominal muscles were assessed using linear and nonlinear approaches. The L5-S1... 

    The Dynamics of a Group of Diffeomorphisms of the Sphere and the Linearization Problem

    , M.Sc. Thesis Sharif University of Technology Khodaeian Karim, Amir (Author) ; Safari, Mohammad (Supervisor) ; Nassiri, Meysan (Supervisor)
    Abstract
    In chis chcsis we consider a work by Dmitry Dolg:opyat and Raphac) Kriko­ rian (on Simulcanoous Lincariwtion of Diffcomorphisms of Sphere) and a recent preprint by Jonathan Dc\Vitt (Simulrn.ncous Lincarization of Diffco­ morphisms of Isotropic Manifolds). Suppasc /1,h,...,J.. arc pcrturbacions of rotations R1, R2 , ...,Rn of the sphere which generate SOd+I (d 2). \\Tc c". plian how it can be shown that all /; can besimn)tancously conjugated to some new rotations when all the Lyapunov cxponcms of the rcndom walk a.,:;.,sociatc to {/;}arc zero. This rcsn1t is applied to obtain stable ergodicity when d is even.The idea is co translate al1 the information co a linear setting and approach chc... 

    Stochastic robust hybrid observer with applications to automotive slip angle estimation

    , Article ASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE) ; Vol. 4B, issue , 2014 ; ISBN: 9780791846483 Merat, K ; Razavi, H ; Salarieh, H ; Alasty, A ; Meghdari, A ; Sharif University of Technology
    Abstract
    In this article, the state estimation for Automotive Slip Angle considering the measurement noise in sensor is addressed. Realtime measurement of the slip angle is applicable to many active vehicle safety applications, such as rollover prevention and yaw stability control. As the sensors that measure slip angle directly are expensive, the method to extract slip angle from other available sensors in vehicle is considered. First from the simplified nonlinear dynamic system of vehicle, a Piecewise Affine (PWA) model with calculated uncertainties is obtained. The uncertainties are the result of nonlinear system deviation from PWA model. Then using the PWA model, a Stochastic Robust Hybrid... 

    Introducing neural networks as a computational intelligent technique

    , Article Applied Mechanics and Materials ; Vol. 464 , 2014 , pp. 369-374 ; ISSN: 16609336 Azizi, A ; Entessari, F ; Osgouie, K. G ; Rashnoodi, A. R ; Sharif University of Technology
    Abstract
    Neural networks have been applied very successfully in the identification and control of dynamic systems. The universal approximation capabilities of the multilayer perceptron have made it a popular choice for modeling nonlinear systems and for implementing general-purpose nonlinear controllers. In this paper we try to model and control the mass-spring-damper mechanism as a 1 DOF system using neural networks. The control architecture used in this paper is Model reference controller (MRC) as one of the popular neural network control architectures  

    A GPU based simulation platform for adaptive frequency Hopf oscillators

    , Article ICEE 2012 - 20th Iranian Conference on Electrical Engineering ; 2012 , Pages 884-888 ; 9781467311489 (ISBN) Soleimani, H ; Maleki, M. A ; Ahmadi, A ; Bavandpour, M ; Maharatna, K ; Zwolinski, M ; Sharif University of Technology
    2012
    Abstract
    In this paper we demonstrate a dynamical system simulator that runs on a single GPU. The model (running on an NVIDIA GT325M with 1GB of memory) is up to 50 times faster than a CPU version when more than 10 million adaptive Hopf oscillators have been simulated. The simulation shows that the oscillators tune to the correct frequencies for both discrete and continuous spectra. Due to its dynamic nature the system is also capable to track non-stationary spectra. With the help of this model the frequency spectrum of an ECG signal (as a non-stationary signal) obtained and was showed that frequency domain representation of signal (i.e. FFT) is the same as one MATLAB generates  

    A homotopy analysis method for limit cycle of the van der Pol oscillator with delayed amplitude limiting

    , Article Applied Mathematics and Computation ; Volume 217, Issue 22 , July , 2011 , Pages 9404-9411 ; 00963003 (ISSN) Eigoli, A. K ; Khodabakhsh, M ; Sharif University of Technology
    2011
    Abstract
    In this work, a powerful analytical method, called Liao's homotopy analysis method is used to study the limit cycle of a two-dimensional nonlinear dynamical system, namely the van der Pol oscillator with delayed amplitude limiting. It is shown that the solutions are valid for a wide range of variation of the system parameters. Comparison of the obtained solutions with those achieved by numerical solutions and by other perturbation techniques shows that the utilized method is effective and convenient to solve this type of problems with the desired order of approximation  

    A fresh insight into Kane's equations of motion

    , Article Robotica ; 2015 ; 02635747 (ISSN) Pishkenari, H. N ; Yousefsani, S. A ; Gaskarimahalle, A. L ; Oskouei, S. B. G ; Sharif University of Technology
    Cambridge University Press  2015
    Abstract
    With rapid development of methods for dynamic systems modeling, those with less computation effort are becoming increasingly attractive for different applications. This paper introduces a new form of Kane's equations expressed in the matrix notation. The proposed form can efficiently lead to equations of motion of multi-body dynamic systems particularly those exposed to large number of nonholonomic constraints. This approach can be used in a recursive manner resulting in governing equations with considerably less computational operations. In addition to classic equations of motion, an efficient matrix form of impulse Kane formulations is derived for systems exposed to impulsive forces....