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    Performance of an offshore platform with MR dampers subjected to wave

    , Article 2011 IEEE International Conference on Mechatronics, ICM 2011 - Proceedings, 13 April 2011 through 15 April 2011 ; April , 2011 , Pages 242-247 ; 9781612849836 (ISBN) Sarrafan, A ; Hamid Zareh, S ; Khayyat, A. A ; Zabihollah, A ; Sharif University of Technology
    The vibration suppression of semi-actively controlled jacket-type offshore platforms using Magnetorheological (MR) dampers is studied. The main goal of using MR damper system is to reduce vibration caused by wave hydrodynamic forces. A fixed jacket-type offshore platform affected by wave-induced hydrodynamic forces and controlled by MR dampers is modelled as a semi-active controlled system with 30 DOFs. In comparison with earlier studies, an improvement in problem modelling is made. Based on the wave theory and Morison equation, an exosystem is designed to simulate regular wave forces. The necessary input voltage to MR dampers to generate desired damping force is derived by clipped optimal... 

    Semi Active Vibration Control of an Eleven Degree of Freedom Passenger Car Using Magnetorheological Shock Absorbers

    , M.Sc. Thesis Sharif University of Technology Zareh, Hamid (Author) ; Khayyat, Amir Ali Akbar (Supervisor)
    This thesis is presented to introduce a semi-active control of the suspension systems. The currently available semi-active damper technologies can be divided into two main groups. The first uses controllable electromagnetic valves and the second uses Magnetorheological (MR) fluid to control the damping characteristics of the system. A mass-spring model with eleven degrees of freedom, considering constant velocity for the car, is developed to model the suspension system. A semi-active vibration control system is presented to reduce the amplitude of automotive vibrations caused by the alteration of the road profile. The gravel road profile with Gaussian white noise as the road irregularity... 

    Study on Semi-Active Isolation Systems for Sensitive Equipment Subjected to Earthquake

    , M.Sc. Thesis Sharif University of Technology Zebarjad, Leila (Author) ; Bakhshi, Ali (Supervisor)
    Sensitive equipment, are vulnerable to strong earthquakes, and failure of these equipment may result in a heavy economic loss. Recent studies have revealed that a conventional passive seismic isolation system may induce an excessive displacement when it is subjected to a near-fault earthquake that possesses strong longperiod components.
    Semi-active control devices are capable of offering the adaptability of active devices and stability and reliability of passive devices that have been considered by many researchers.
    Magnetorheological (MR) damper is a reliable semi-active control device which works in a wide range of temperature besides its mechanical simplicity at a modest... 

    On the linear-quadratic regulator problem in one-dimensional linear fractional stochastic systems

    , Article Automatica ; Vol. 50, issue. 1 , 2014 , pp. 282-286 ; ISSN: 00051098 Sadeghian, H ; Salarieh, H ; Alasty, A ; Meghdari, A ; Sharif University of Technology
    In this paper, for one-dimensional stochastic linear fractional systems in terms of the Riemann-Liouville fractional derivative, the optimal control is derived. It is assumed that the state is completely observable and all the information regarding this is available. The formulation leads to a set of stochastic fractional forward and backward equation in the Riemann-Liouville sense. The proposed method has been checked via some numerical simulations which show the effectiveness of the fractional stochastic optimal algorithm  

    Computation time analysis of centralized and distributed optimization algorithms applied to automated irrigation networks

    , Article 2013 3rd Australian Control Conference, AUCC 2013, Fremantle, WA ; Nov , 2013 , Pages 263-269 ; 9781479924981 (ISBN) Farhadi, A ; Dower, P. M ; Cantoni, M ; Sharif University of Technology
    This paper compares the computation time of two algorithms for solving a structured constrained linear optimal control problem with finite horizon quadratic cost within the context of automated irrigation networks. The first is a standard centralized algorithm based on the active set method that does not exploit problem structure. The second is distributed and is based on a consensus algorithm, not specifically tailored to account for system structure. It is shown that there is a significant advantage in terms of computation overhead (the time spent computing the optimal solution) in using the second algorithm in large-scale networks. Specifically, for a fixed horizon length the computation... 

    Intelligent semi-active vibration control of eleven degrees of freedom suspension system using magnetorheological dampers

    , Article Journal of Mechanical Science and Technology ; Volume 26, Issue 2 , 2012 , Pages 323-334 ; 1738494X (ISSN) Zareh, S. H ; Sarrafan, A ; Khayyat, A. A. A ; Zabihollah, A ; Sharif University of Technology
    A novel intelligent semi-active control system for an eleven degrees of freedom passenger car's suspension system using magnetorheological (MR) damper with neuro-fuzzy (NF) control strategy to enhance desired suspension performance is proposed. In comparison with earlier studies, an improvement in problem modeling is made. The proposed method consists of two parts: a fuzzy control strategy to establish an efficient controller to improve ride comfort and road handling (RCH) and an inverse mapping model to estimate the force needed for a semi-active damper. The fuzzy logic rules are extracted based on Sugeno inference engine. The inverse mapping model is based on an artificial neural network... 

    Optimal Design of Passive Control Systems Using Siffness Reduction and Viscous Damping Devices Using Instantaneous Optimal Control and Polynomial Control Algorithms

    , M.Sc. Thesis Sharif University of Technology Sahami, Kaveh (Author) ; Ahmadizadeh, Mehdi (Supervisor)
    In this study, an active control strategy is used for design of passive energy dissipation systems using viscous fluid dampers and structural stiffness modification. The combination of supplemental damping and modification (usually reduction) of stiffness is used to minimize the two main structural response parameters, namely the maximum inter-story drifts and maximum absolute accelerations. In this manner, both structural and nonstructural damages can be controlled.
    While active control systems are expected to improve the structural esponse beyond what can be achieved in passive control, the practical implementation of control systems are mostly of passive type.... 

    Effects of structural configuration on vibration control of smart laminated beams under random excitations

    , Article Journal of Mechanical Science and Technology ; Volume 24, Issue 5 , 2010 , Pages 1119-1125 ; 1738494X (ISSN) Zabihollah, A ; Sharif University of Technology
    The influence of structural configuration on vibration responses of smart laminated beams under random loading is studied. The effect of laminate configurations and locations of sensors/actuators in the smart system is also investigated. The layer-wise approximation for displacement and electric potential is utilized to construct the finite element model. The closed-loop control response is determined through an optimal control algorithm based on the Linear Quadratic Regulator (LQR). The correlation coefficient between the input random force and the applied actuating voltage for various configurations is also computed. It is revealed that for softer configurations, the correlation... 

    Vibration control of beams on elastic foundation under a moving vehicle and random lateral excitations

    , Article Journal of Sound and Vibration ; Volume 331, Issue 6 , March , 2012 , Pages 1217-1232 ; 0022460X (ISSN) Zarfam, R ; Khaloo, A. R ; Sharif University of Technology
    The formulation of three-dimensional dynamic behavior of a Beam On Elastic Foundation (BOEF) under moving loads and a moving mass is considered. The weight of the vehicle is modeled as a moving point load, however the effect of the lateral excitation is considered by modeling: (case 1) a lateral moving load with random intensity for wind excitation and (case 2) a moving mass just in lateral direction of the beam for earthquake excitation. A Dirac-delta function is used to describe the position of the moving load and the moving mass along the beam. The beam foundations are considered as elastic Winkler-type in two perpendicular transverse directions. This model is proposed to investigate the... 

    Optimal tuning of linear controllers for power electronics/power systems applications

    , Article Electric Power Systems Research ; Volume 81, Issue 12 , 2011 , Pages 2188-2197 ; 03787796 (ISSN) Hasanzadeh, A ; Edrington, C. S ; Mokhtari, H ; Sharif University of Technology
    This paper presents a new method for tuning various linear controllers such as Proportional-Integral (PI), Proportional-Integral-Derivative (PID) and Proportional-Resonant (PR) structures which are frequently used in power electronics and power system applications. The linear controllers maintain a general structure defined by the Internal Model Principle (IMP) of control theory. The proposed method in this paper is twofold. The first perspective uses the well-known concept of the Linear Quadratic Regulator (LQR) to address the problem as a regulation problem. The Q matrix of the LQR design is then finely adjusted in order to assure the desired transient response for the system. The second... 

    Semi active vibration control of a passenger car using magnetorheological shock absorber

    , Article ASME 2010 10th Biennial Conference on Engineering Systems Design and Analysis, ESDA2010, Istanbul, 12 July 2010 through 14 July 2010 ; Volume 3 , 2010 , Pages 21-27 ; 9780791849170 (ISBN) Fellah Jahromi, A ; Zabihollah, A ; Sharif University of Technology
    A novel semi-active control system for suspension systems of passenger car using Magnetorheological (MR) damper is introduced. The suspension system is considered as a mass-spring model with an eight-degrees-of-freedom, a passive damper and an active damper. The semi-active vibration control is designed to reduce the amplitude of automotive vibration caused by the alteration of road profile. The control mechanism is designed based on the optimal control algorithm, Linear Quadratic Regulator (LQR). In this system, the damping coefficient of the shock absorber changes actively trough inducing magnetic field. It is observed that utilizing the present control algorithm may significantly reduce...