Search for: control-theory
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    Control of diseases epidemic spreading through metapopulation models

    , Article International Journal of Control Theory and Applications ; Volume 8, Issue 2 , 2015 , Pages 769-784 ; 09745572 (ISSN) Afshar, M ; Razvan, M. R ; Sharif University of Technology
    International Sciences Press  2015
    We study a system of ordinary differential equations which describes the metapopulation SIR model. The main target is to control the epidemic spreading using the structure of connections between cities. For this purpose, we formulate optimal control strategy that the control represents a drug treatment and Prevention strategies . Some methods are given in numerical example section such as control through spectral radius of movement matrix or optimal control through travelling between cities. Existence results for the optimal control are studied  

    Compensation by fractional-order phase-lead/lag compensators

    , Article IET Control Theory and Applications ; Volume 8, Issue 5 , 2014 , Pages 319-329 ; ISSN: 17518644 Tavazoei, M. S ; Tavakoli Kakhki, M ; Sharif University of Technology
    This study deals with a generalised version of lead/lag compensators known as fractional-order lead/lag compensators. Exact and simple formulas are found for designing this introduced type of fractional-order compensators in order to provide the required magnitude and phase at a given frequency. Also, the region in the phase-magnitude plane, which is accessible by these compensators, is analytically found. Moreover, numerical examples and experimental results are presented to show the applicability of the achievements of this study in control system design  

    Position convergence of informed agents in flocking problem with general linear dynamic agents

    , Article IET Control Theory and Applications ; Volume 9, Issue 3 , February , 2015 , Pages 392-398 ; 17518644 (ISSN) Yazdani, S ; Haeri, M ; Sharif University of Technology
    Institution of Engineering and Technology  2015
    In most existing works on the flocking problem, results were obtained for the case where a double integrator dynamic is used to describe motion of agents and virtual leader. These results, however, may not be generalised to agents with general linear dynamic. In this study, it is shown that in the flocking of agents with a linear dynamic, the velocity convergence of agents does not generally lead to the position convergence of informed agents and the position convergence is possible only for a specified group of linear dynamics. In this study, a control protocol is proposed to flock agents with specified linear dynamics and guarantee the velocity convergence of all agents as well as average... 

    Effects of human pilot energy expenditure on pilot evaluation of handling qualities

    , Article Collection of Technical Papers - AIAA Atmospheric Flight Mechanics Conference, Providence, RI, 16 August 2004 through 19 August 2004 ; Volume 2 , 2004 , Pages 1381-1389 ; 1563477009 (ISBN) Malaek, S. M ; Sajjadi Kia, S ; Sharif University of Technology
    A new methodology has been proposed to model and predict the pilot rating of a typical aircraft for flights through turbulences. The main idea here is to correlate the so-called "pilot rating" to the pilot physical energy demanded by the aircraft in a given flight condition and flying task. The proposed methodology, in addition to the other known factors, accepts the level of the human pilot physical energy consumed in each suitable period of time as well as the rate of energy consumption in the same period. These two, form the prime factors to predict the pilot rating in flying tasks that have a reasonable duration. Different case studies conducted by the authors show that for cases like... 

    A study on vertical motions of high-speed planing boats with automatically controlled stern interceptors in calm water and head waves

    , Article Ships and Offshore Structures ; Volume 10, Issue 3 , 2015 , Pages 335-348 ; 17445302 (ISSN) Karimi, M. H ; Seif, M. S ; Abbaspoor, M ; Sharif University of Technology
    The controllable flaps and interceptors in planing crafts not only may reduce the resistance, but also could be designed to make a boat run at or near optimum attitude in various environments, which results in a reduction in both resistance and vertical motion in waves. Planing vessels suffer from porpoising instability and violent vertical motion at high forward speeds. The controllable flaps and interceptors can be used to control and reduce the vertical motion of planing crafts. In the present study, the impact of controlled interceptors on a planing craft seakeeping quality is investigated through application of experimental and theoretical methods. In the experimental part of the study,... 

    Robust adaptive backstepping control of uncertain lorenz system [electronic resource]

    , Article Journal of American Institute of Physics ; 2010, Vol. 20, pp. 1-5 Nejat Pishkenari, H. (Hossein) ; Jalili, Nader ; Mahboobi, Seyed Hanif ; Alasty, Aria ; Meghdari, Ali ; Sharif University of Technology
    In this paper, a novel robust adaptive control method is proposed for controlling the Lorenz chaotic attractor. A new backstepping controller for the Lorenz system based on the Lyapunov stability theorem is proposed to overcome the singularity problem that appeared in using the typical backstepping control method. By exploiting the property of the system, the resulting controller is shown to be singularity free and the closed loop system is globally stable. Due to unavailability of system states measurement in practice, the controller is selected such that only one system state is needed. To overcome the problem of parameter uncertainty, an additional term to Lyapunov function is added and... 

    Duffing equations with cubic and quintic nonlinearities

    , Article Computers and Mathematics with Applications ; Volume 57, Issue 3 , 2009 , Pages 500-506 ; 08981221 (ISSN) Pirbodaghi, T ; Hoseini, H ; Ahmadian, M. T ; Farrahi, G. H ; Sharif University of Technology
    In this study, an accurate analytical solution for Duffing equations with cubic and quintic nonlinearities is obtained using the Homotopy Analysis Method (HAM) and Homotopy Pade technique. Novel and accurate analytical solutions for the frequency and displacement are derived. Comparison between the obtained results and numerical solutions shows that only the first order approximation of the Homotopy Pade technique leads to accurate solution with a maximum relative error less than 0.4%. © 2008 Elsevier Ltd. All rights reserved  

    Control of multi-agent systems based on redundant manipulator global optimization techniques

    , Article 2006 IEEE International Conference on Systems, Man and Cybernetics, Taipei, 8 October 2006 through 11 October 2006 ; Volume 3 , 2006 , Pages 2499-2504 ; 1062922X (ISSN); 1424401003 (ISBN); 9781424401000 (ISBN) Sadati, N ; Elhamifar, E ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2006
    In this paper, a new approach for path generation and control of multi-agent systems is proposed. This method is based on global optimization techniques used for solving the inverse kinematic problem of redundant manipulators. Convergence of any performance function such as obstacle avoidance, collision avoidance, and heading angle to its global optimum is guaranteed by introducing a control law which is based on the Pontryagin's Maximum Principle. The efficacy of the proposed algorithm is demonstrated through simulation experiments. © 2006 IEEE  

    Fault diagnosis in multivariate control charts using artificial neural networks

    , Article Quality and Reliability Engineering International ; Volume 21, Issue 8 , 2005 , Pages 825-840 ; 07488017 (ISSN) Akhavan Niaki, S. T ; Abbasi, B ; Sharif University of Technology
    Most multivariate quality control procedures evaluate the in-control or out-of-control condition based upon an overall statistic, like Hotelling's T2. Although T2 is optimal for finding a general shift in mean vectors, it is not optimal for shifts that occur for some subset of variables. This introduces a persistent problem in multivariate control charts, namely the interpretation of a signal that often discourages practitioners in applying them. In this paper, we propose an artificial neural network based model to diagnose faults in out-of-control conditions and to help identify aberrant variables when Shewhart-type multivariate control charts based on Hotelling's T2 are used. The results... 

    Peak Temperature Recduction in 3D NoCs using Task Migration

    , M.Sc. Thesis Sharif University of Technology Mohebbi Moghaddam, Monireh (Author) ; Hessabi, Shaahin (Supervisor)
    Combination of 3D stacking and network-on-chip (NoC), known as 3D NoC, has some advantages such as reduced propagation delay, chip area and interconnect, and power consumption, and bandwidth increase. Despite these advantages, the increased power density per chip area due to area decrease causes thermal problems in 3D NoCs to be more critical than 2D NoCs. Therefore, design of temperature management algorithms is essential for these systems. One of the dynamic thermal management techniques is task migration that balances generated thermal among cores.In this thesis, we propose a task migration scheme using feedback control for 3D NoCs. The main purpose of this scheme is to decrease the peak... 

    Extracting Synergies in Nonlinear Dynamics and Investigating their Neural Basis

    , M.Sc. Thesis Sharif University of Technology Bayati, Hamid Reza (Author) ; Vosoughi Vahdat, Bijan (Supervisor)
    The existence of motor synergies in motor system as a tool for reducing degrees of freedom has been always debated. In the last two decades some experiments in vertebrates show the existence of motor primitives in spinal cord. In additional by recording electromyogram from frog some regular patterns have been shown. Recently, a motor coordination model based on stochastic optimal feedback control has extracted synergies by mathematical formulation. In addition, according to this model synergies are the optimal solution of the problem and not for simplifying it. However, this model is investigated in linear dynamics. In this thesis, first, an inverse method for extracting synergies is... 

    Evolutionary Dynamics of Tumorigenesis: An Application of Dynamical Systems

    , M.Sc. Thesis Sharif University of Technology Akbari, Mohammad Javad (Author) ; Alishahi, Kasra (Supervisor) ; Razvan, Mohammad Reza (Co-Supervisor)
    Application of optimal control in cancer modeling is studied through both linear and nonlinear modeling of the dynamics in ordinary differential equations. At the outset, a fairly straight-forward analysis of a linear model in presented. Through comparably simple machinery, this seminal work published at early 2000s covers some of most important techniques previously developed. The model here is infinite- dimensional, taking different number of gene amplifications into account. Thereafter by surveying recently published papers, the literature is reviewed and different lines of progress is followed, culminating in detailed study of a specific approach which is theoretically of interest.... 

    Geometric control of the brachiation robot using controlled Lagrangians method

    , Article 2014 2nd RSI/ISM International Conference on Robotics and Mechatronics, ICRoM 2014 ; 17 December , 2014 , Pages 706-710 Tashakori, S ; Vossoughi, G ; Yazdi, E. A ; Sharif University of Technology
    This paper studies a brachiation robot that is a long armed locomotion similar to apes. The robot has 2 revolute joints but only one of them is actuated. In this paper, after deriving dynamic model of the robot the Controlled Lagrangian (CL) method is used for stabilization. The matching conditions satisfied for the controller are derived and the extended λ-method is used to solve PDE's involved in the method of controlled lagrangian. Satisfactory controller's gains are chosen by PSO algorithm. Finally, feasibility of the developed controller is investigated by numerical simulations  

    Improved bounds for the spectrum of interval matrices

    , Article IET Control Theory and Applications ; Volume 7, Issue 7 , 2013 , Pages 1022-1028 ; 17518644 (ISSN) Firouzbahrami, M ; Babazadeh, M ; Nobakhti, A ; Karimi, H ; Sharif University of Technology
    This study presents new sufficient conditions for Hurwitz and Schur stability of interval matrices. Tight bounds for the spectrum of interval matrices are estimated using computationally simple optimisation problems. The conservativeness is reduced further by application of ordinary similarity transformation. A necessary and sufficient vertex based criterion for the stability of a subclass of interval systems in continuous and discrete-time cases is also proposed. This enables the spectra for this class of interval systems to be determined exactly. A selection of various examples adopted from existing literature is used to demonstrate the utility of the proposed criteria  

    Suppression of nonlinear regenerative chatter in milling process via robust optimal control

    , Article Journal of Process Control ; Volume 23, Issue 5 , 2013 , Pages 631-648 ; 09591524 (ISSN) Moradi, H ; Vossoughi, G ; Movahhedy, M. R ; Salarieh, H ; Sharif University of Technology
    During the milling process, self-excited vibration or chatter adversely affects tool life, surface quality and productivity rate. In this paper, nonlinear cutting forces of milling process are considered as a function of chip thickness with a complete third order polynomial (instead of the common linear dependency). An optimal control strategy is developed for chatter suppression of the system described through nonlinear delay differential equations. Counterbalance forces exerted by actuators in x and y directions are the control inputs. For optimal control problem, an appropriate performance index is defined such that the regenerative chatter is suppressed while control efforts are... 

    Adaptive integrated guidance and fault tolerant control using backstepping and sliding mode

    , Article International Journal of Aerospace Engineering ; Volume 2015 , September , 2015 ; 16875966 (ISSN) Jegarkandi, M. F ; Ashrafifar, A ; Mohsenipour, R ; Sharif University of Technology
    Hindawi Publishing Corporation  2015
    A new method of integrated guidance and control for homing missiles with actuator fault against manoeuvring targets is proposed. Model of the integrated guidance and control system in the pitch plane with actuator fault and some uncertainty is developed. A control law using combination of adaptive backstepping and sliding mode approaches is designed to achieve interception in the presence of bounded uncertainties and actuator fault. Simulation results show that new approach has better performance than adaptive backstepping and has good performance in the presence of actuator fault  

    Design of hydractive optimal suspension for a passenger vehicle

    , Article ASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE), 12 November 2010 through 18 November 2010, Vancouver, BC ; Volume 8, Issue PARTS A AND B , 2010 , Pages 351-359 ; 9780791844458 (ISBN) Sarshari, E ; Asadi, N ; Yousefi, R ; Sharif University of Technology
    In this study a hydractive suspension system is designed for a passenger car. By using a mathematical validated model with eight degrees of freedom for a vehicle which is equipped with hydractive suspension, optimal damping forces derived for suspension system on the base of optimal control theory which uses linear quadratic regulators for improving ride comfort of vehicle and saves vehicles stability at the same time. Existing limitations for applying damping forces and time lag of controlling component are considered. The results are being derived according to a bump excitation and nonlinearity effects of the hydractive suspension components. Simulation results for the hydractive optimal... 

    Closed-form optimal cooperative guidance law against random step maneuver

    , Article IEEE Transactions on Aerospace and Electronic Systems ; Volume 52, Issue 1 , 2016 , Pages 319-336 ; 00189251 (ISSN) Nikusokhan, M ; Nobahari, H ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc 
    Based on the optimal control theory, the present study proposes a novel approach to derive a cooperative guidance law for two pursuers with an arbitrary-order linear dynamics against one zero-lag evader with random step maneuver. This approach is intended to minimize the mean value of the resultant control effort taken over a set of possible evader maneuvers which is modeled as a step function, the parameters of which are unknown. Since the resultant control effort is the minimum effort among the pursuers, we encounter the nonlinear "min" function in the performance index. By introducing binary parameters, it is changed to a linear function including binary parameters and continuous... 

    Adaptive observer-based synchronization of two non-identical chaotic systems with unknown parameters

    , Article JVC/Journal of Vibration and Control ; Volume 23, Issue 3 , 2017 , Pages 389-399 ; 10775463 (ISSN) Bagheri, P ; Shahrokhi, M ; Salarieh, H ; Sharif University of Technology
    SAGE Publications Inc  2017
    In this study, adaptive observer-based synchronization of chaotic systems is considered. The master and slaves systems have different dynamics and it is assumed that the master system parameters are unknown while its states are available. First, it is assumed that the slave system parameters are known but its states are not completely available. It is shown that an observer for the slave system can be designed and applied for the purpose of synchronization. Based on a Lyapunov function, an adaptive law for master parameters estimation and a control law for the synchronization goal are extracted. Stability of the entire system including the observer dynamics has been proved. Further, it is... 

    Some relations between rank, chromatic number and energy of graphs

    , Article Discrete Mathematics ; Volume 309, Issue 3 , 2009 , Pages 601-605 ; 0012365X (ISSN) Akbari, S ; Ghorbani, E ; Zare, S ; Sharif University of Technology
    The energy of a graph G, denoted by E (G), is defined as the sum of the absolute values of all eigenvalues of G. Let G be a graph of order n and rank (G) be the rank of the adjacency matrix of G. In this paper we characterize all graphs with E (G) = rank (G). Among other results we show that apart from a few families of graphs, E (G) ≥ 2 max (χ (G), n - χ (over(G, -))), where n is the number of vertices of G, over(G, -) and χ (G) are the complement and the chromatic number of G, respectively. Moreover some new lower bounds for E (G) in terms of rank (G) are given. © 2008 Elsevier B.V. All rights reserved