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Total 40 records

    Design of an stable GPC for nonminimum phase LTI systems

    , Article Wec 05: Fourth World Enformatika Conference, Istanbul, 24 June 2005 through 26 June 2005 ; Volume 6 , 2005 , Pages 88-91 ; 9759845857 (ISBN); 9789759845858 (ISBN) Yaghobi, M ; Haeri, M ; Sharif University of Technology
    2005
    Abstract
    The current methods of predictive controllers are utilized for those processes in which the rate of output variations is not high. For such processes, therefore, stability can be achieved by implementing the constrained predictive controller or applying infinite prediction horizon. When the rate of the output growth is high (e.g. for unstable nonminimum phase process) the stabilization seems to be problematic. In order to avoid this, it is suggested to change the method in the way that: first, the prediction error growth should be decreased at the early stage of the prediction horizon, and second, the rate of the error variation should be penalized. The growth of the error is decreased... 

    A novel method on singularity analysis in parallel manipulators

    , 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) Pendar, H ; Mahnama, M ; Zohoor, H ; Sharif University of Technology
    American Society of Mechanical Engineers  2006
    Abstract
    A parallel manipulator is a closed loop mechanism in which a moving platform is connected to the base by at least two serial kinematic chains. The main problem engaged in these mechanisms, is their restricted working space as a result of singularities. In order to tackle these problems, many methods have been introduced by scholars. However, most of the mentioned methods are too much time consuming and need a great amount of computations. They also in most cases do not provide a good insight to the existence of singularity for the designer. In this paper a novel approach is introduced and utilized to identify singularities in parallel manipulators. By applying the new method, one could get a... 

    Closed-loop finite element modeling for analysis of smart structures in ansys environment

    , Article 2006 ASME International Mechanical Engineering Congress and Exposition, IMECE2006, Chicago, IL, 5 November 2006 through 10 November 2006 ; 2006 ; 10716947 (ISSN); 0791837904 (ISBN); 9780791837900 (ISBN) Mahboobi, S. H ; Shahidi, A ; Abedian, A ; Meghdari, A ; Sharif University of Technology
    American Society of Mechanical Engineers (ASME)  2006
    Abstract
    It would be promising if one can simulate the closed-loop behavior of a smart system in an available FEM software such as "ANSYS". The ANSYS/Multiphysics software has the ability of coupling different physical domains and also modeling smart materials such as piezoelectric and piezoresistives, i.e. it has the capability of modeling smart structures. The dynamic modeling of the controlled structures is then realized by the ANSYS programming tool. This aspect highly facilitates the overall system behavior analysis and at the same time various control methods can be tested without noticing the time consuming structural analysis involved. In this research work, it is tried the mentioned idea to... 

    Design of a fuzzy controller for an underwater vehicle aiming at a stationary target

    , 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) Azarsina, F ; Sayyaadi, H ; Sharif University of Technology
    American Society of Mechanical Engineers  2006
    Abstract
    In this paper, on the basis of a robust algorithm for the analysis of the 6 DOF motion of an underwater vehicle in calm water, after presenting the dynamics model and simulating motion, the model is put in the closed loop control to perform a controlled mission. The mission is defined as to navigate the submarine toward a desired point in the vertical plane. In performing the mission, the least time and of course the least position error with respect to the target point is aimed. The designed controller based on fuzzy logic and thus adapted to the human patterns for navigation, with a simple structure, performs the mission accurately. The intelligent structure of the fuzzy controller,... 

    Development of a hybrid reference model for performance evaluation of resolvers

    , Article IEEE Transactions on Instrumentation and Measurement ; Volume 70 , 2021 ; 00189456 (ISSN) Khajueezadeh, M ; Saneie, H ; Nasiri Gheidari, Z ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2021
    Abstract
    Resolver is an electromagnetic position sensor typically used in the closed-loop control of permanent magnet synchronous motors (PMSMs). In terms of structure and principle of operation, resolvers are very similar to electrical machines. In this regard, different numerical and analytical models have been developed for the performance prediction of a resolver, with a compromise between computational burden and accuracy. Therefore, a fast and accurate hybrid model of the resolver is presented in this article, which can be used for resolvers with different structures. Additionally, this model can easily be implemented in software such as MATLAB/SIMULINK. The performance of different variable... 

    Application of neural networks to decentralized control of robot manipulators with high degree of freedom

    , Article ICTAI 2005: 17th IEEE International Conference on Tools with Artificial Intelligence, ICTAI'05, Hong Kong, 14 November 2005 through 16 November 2005 ; Volume 2005 , 2005 , Pages 484-488 ; 10823409 (ISSN); 0769524885 (ISBN); 9780769524887 (ISBN) Sadati, N ; Elhamifar, E ; Sharif University of Technology
    2005
    Abstract
    In this paper a neural network decentralized control for trajectory tracking of robot manipulators is developed. The proposed decentralized control allows the overall closed-loop system to be stabilized while making the tracking error to be uniformly ultimately bounded (UUB), without having any prior knowledge of the robot manipulator dynamics. The interconnections in the dynamic equations of each subsystem are considered with unknown nonlinear bounds. The RBF neural networks (RBFNNs) are proposed to model the unknown nonlinear dynamics of the robots and the interconnection terms. Using Lyapunov method, the stability of the overall system is investigated, © 2005 IEEE  

    Experimental investigation on the micro-step control disturbance rejection under random excitations

    , Article DETC2005: ASME International Design Engineering Technical Conferences and Computers and Information in Engineering Conference, Long Beach, CA, 24 September 2005 through 28 September 2005 ; Volume 1 B , 2005 , Pages 1747-1751 ; 0791847381 (ISBN) Ghafari, A. S ; Behzad, M ; Sharif University of Technology
    2005
    Abstract
    Effect of random signals with various powers, as current loads, on positioning and disturbance rejection problems on micro-step PID closed loop control system is addressed in this paper. Experimental results due to implementing different white noise power, speed, and a 0.3 N.m disturbance load torque show that, Random noise source changes current profile and affects the accuracy of positioning in tracking and disturbance rejection problems. Performance of the PID proposed controller under the implementation of random noise on phases of the HSM has been proved to be accurate enough even under disturbance torque acting on the system. Copyright © 2005 by ASME  

    Control of a nonlinear system using the saturation phenomenon

    , Article Nonlinear Dynamics ; Volume 42, Issue 2 , 2005 , Pages 113-136 ; 0924090X (ISSN) Shoeybi, M ; Ghorashi, M ; Sharif University of Technology
    2005
    Abstract
    In this paper, a theoretical investigation of nonlinear vibrations of a 2 degrees of freedom system when subjected to saturation is studied. The method has been especially applied to a system that consists of a DC motor with a nonlinear controller and a harmonic forcing voltage. Approximate solutions are sought using the method of multiple scales. It is shown that the closed-loop system exhibits different response regimes. The nature and stability of these regimes are studied and the stability boundaries are obtained. The effects of the initial conditions on the response of the system have also been investigated. Furthermore, the second-order solution is presented and the corresponding... 

    Output feedback adaptive decentralized control of cooperative robots

    , Article ICIECA 2005: International Conference on Industrial Electronics and Control Applications 2005, Quito, 29 November 2005 through 2 December 2005 ; Volume 2005 , 2005 ; 0780394194 (ISBN); 9780780394193 (ISBN) Sadati, N ; Elhamifar, E ; Sharif University of Technology
    IEEE Computer Society  2005
    Abstract
    In this paper a decentralized control scheme for multiple cooperative manipulators is developed to achieve the desired performance in motion and force tracking, in the presence of uncertainties in dynamic equations of the robots. To eliminate the effects of uncertainties in the closed-loop performance, a new adaptive control algorithm is proposed. Based on the Lyapunov stability method, it is proved that all the error signals in the closed-loop system which is compose of a robot, an observer and a controller asymptotically converge to zero. Also to avoid the difficulties of using velocity sensors within the cooperative system, an output feedback control scheme with a linear observer is used.... 

    Maestro: A high performance AES encryption/decryption system

    , Article Proceedings - 17th CSI International Symposium on Computer Architecture and Digital Systems, CADS 2013 ; October , 2013 , Pages 145-148 ; 9781479905621 (ISBN) Biglari, M ; Qasemi, E ; Pourmohseni, B ; Computer Society of Iran; IPM ; Sharif University of Technology
    IEEE Computer Society  2013
    Abstract
    High throughput AES encryption/decryption is a necessity for many of modern embedded systems. This article presents a high performance yet cost efficient AES system. Maestro can be used in a wide range of embedded applications with various requirements and limitations. Maestro is about one million times faster than the pure software implementation. The Maestro architecture is composed of two major components; the soft processor aimed at system initialization and control, and the hardware AES engine for high performance AES encryption/decryption. A ten stage implicit pipelined architecture is considered for the AES engine. Two novel techniques are proposed in design of AES engine which enable... 

    Adaptive prescribed performance control of switched MIMO uncertain nonlinear systems subject to unmodeled dynamics and input nonlinearities

    , Article International Journal of Robust and Nonlinear Control ; Volume 28, Issue 18 , 2018 , Pages 5981-5996 ; 10498923 (ISSN) Malek, S. A ; Shahrokhi, M ; Vafa, E ; Moradvandi, A ; Sharif University of Technology
    Abstract
    In this paper, the design of an adaptive tracking control for a class of switched uncertain multiple-input–multiple-output nonlinear systems in the strict-feedback form with unmodeled dynamics in the presence of three types of input nonlinearity under arbitrary switching has been addressed. By means of an intelligent approximator like a fuzzy logic system or a neural network, the unknown dynamics are estimated. The unmodeled dynamics have been tackled with a dynamic signal. A universal framework for describing different types of input nonlinearity including saturation, backlash, and dead zone has been utilized. By applying the backstepping approach and the common Lyapunov function method,... 

    Robust D-stability test of LTI general fractional order control systems

    , Article IEEE/CAA Journal of Automatica Sinica ; Volume 7, Issue 3 , May , 2020 , Pages 853-864 Mohsenipour, R ; Liu, X ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2020
    Abstract
    This work deals with the robust D-stability test of linear time-invariant ( LTI ) general fractional order control systems in a closed loop where the system and - or the controller may be of fractional order. The concept of general implies that the characteristic equation of the LTI closed loop control system may be of both commensurate and non-commensurate orders, both the coefficients and the orders of the characteristic equation may be nonlinear functions of uncertain parameters, and the coefficients may be complex numbers. Some new specific areas for the roots of the characteristic equation are found so that they reduce the computational burden of testing the robust D-stability. Based on... 

    An Extremely low ripple high voltage power supply for pulsed current applications

    , Article IEEE Transactions on Power Electronics ; Volume 35, Issue 8 , 2020 , Pages 7991-8001 Zarghani, M ; Mohsenzade, S ; Hadizade, A ; Kaboli, S ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2020
    Abstract
    This article describes the development of an 18 kV, 30 kW power supply for a pulsed current load with the maximum current of 20 A and a di/dt equal to 100 A/μs. The achieved output ripple is less than 0.01%. In such a high level of precision, the most important issues are considerable difference between the instantaneous and average output powers, as well as insufficient reaction speed of the converter to the fast load change. Very low level of the voltage feedback and its sensitivity to the noise. The first issue necessitates a notable overdesign of the converter switches if the output voltage precision is dedicated to the converter. The second issue raises the problems relevant to... 

    Stabilizing periodic orbits of chaotic systems using fuzzy adaptive sliding mode control

    , Article Chaos, Solitons and Fractals ; Volume 37, Issue 4 , August , 2008 , Pages 1125-1135 ; 09600779 (ISSN) Layeghi, H ; Arjmand, M. T ; Salarieh, H ; Alasty, A ; Sharif University of Technology
    2008
    Abstract
    In this paper by using a combination of fuzzy identification and the sliding mode control a fuzzy adaptive sliding mode scheme is designed to stabilize the unstable periodic orbits of chaotic systems. The chaotic system is assumed to have an affine form x(n) = f(X) + g(X)u where f and g are unknown functions. Using only the input-output data obtained from the underlying dynamical system, two fuzzy systems are constructed for identification of f and g. Two distinct methods are utilized for fuzzy modeling, the least squares and the gradient descent techniques. Based on the estimated fuzzy models, an adaptive controller, which works through the sliding mode control, is designed to make the... 

    A new multi-machine control system based on direct torque control algorithm

    , Article 7th Internatonal Conference on Power Electronics, ICPE'07, Daegu, 22 October 2007 through 26 October 2007 ; 2007 , Pages 1103-1108 ; 9781424418725 (ISBN) Mohktari, H ; Alizadeh, A ; Sharif University of Technology
    IEEE Computer Society  2007
    Abstract
    In this paper, a new and simple control method based on Direct Torque Control (DTC) of induction motors is proposed for a multi-machine system. Similar to a conventional DTC, the proposed method has two separate control loops. In the torque control loop, before selection of optimum voltage from the DTC look-up table, the system overall requirement is determined based on requirements of motors torque. Also, Switchable Master-Slave control is used in the flux control loop. The method, which is simulated for a two-parallel induction machine system, can be extended to a multi-machine system. Simulation results are also provided to investigate the performance of the proposed technique. © 2008... 

    Predictive directional compensator for systems with input constraints

    , Article ISA Transactions ; Volume 45, Issue 3 , 2006 , Pages 393-405 ; 00190578 (ISSN) Haeri, M ; Aalam, N ; Sharif University of Technology
    ISA - Instrumentation, Systems, and Automation Society  2006
    Abstract
    Nonlinearity caused by actuator constraint plays a destructive role in the overall performance of a control system. A model predictive controller can handle the problem by implementing a constrained optimization algorithm. Due to the iterative nature of the solution, however, this requires high computation power. In the present work we propose a new method to approach the problem by separating the constraint handling from the predictive control job. The input constraint effects are dealt with in a newly defined component called a predictive directional compensator, which works based on the directionality and predictive concepts. Through implementation of the proposed method, the... 

    Model reference adaptive control of SUT building energy management system

    , Article 2005 ASME International Mechanical Engineering Congress and Exposition, IMECE 2005, Orlando, FL, 5 November 2005 through 11 November 2005 ; Volume 10 , 2006 , Pages 25-28 ; 0791842274 (ISBN) Fardadi, M ; Selk Ghafari, A ; Hannani, S. K ; Sharif University of Technology
    2006
    Abstract
    Model Reference Adaptive Controller (MRAC) design, for Sharif University of Technology (SUT) Building Energy Management System (BEMS) is addressed in this paper. A reference model with fuzzy adaptive control rules was employed to design the controller for a system with time delay and model parameter uncertainties. Simulation study shows good performance of the closed loop system with optimum energy consumption for this system under external load disturbance. Copyright © 2005 by ASME  

    Non-linear feedback optimal control law for minimum-time injection problem using fuzzy system

    , Article Aircraft Engineering and Aerospace Technology ; Volume 77, Issue 5 , 2005 , Pages 376-383 ; 00022667 (ISSN) Pourtakdoust, S. H ; Rahbar, N ; Novinzadeh, A. B ; Sharif University of Technology
    2005
    Abstract
    Purpose - To devise a new technique to synthesise optimal feedback control law for non-linear dynamic systems through fuzzy logic. Design/methodology/approach - The proposed methodology utilizes the open-loop optimal control solutions (OCSs) of the non-linear systems for the training of the fuzzy system in the process of developing closed-loop fuzzy logic guidance (FLG). This is achieved through defining a set of non-dimensionalised variables related to the system states. Findings - FLG is capable of generating closed-loop control law for the non-linear problem investigated. Since the proposed fuzzy structure is independent of the system equations, the approach is potentially applicable to... 

    Hybrid modeling and control of a DC-DC boost converter via Extended Mixed Logical Dynamical systems (EMLDs)

    , Article PEDSTC 2014 - 5th Annual International Power Electronics, Drive Systems and Technologies Conference ; 2014 , pp. 373-378 Hejri, M ; Mokhtari, H ; Sharif University of Technology
    Abstract
    The objective of this paper is to expand the concept of hybrid modeling and control in power electronics area. A new precise and non-averaged model of a DC-DC boost converter is developed on the basis of Mixed Logical Dynamical (MLD) systems, and the approach is extended by a new version of such systems which is called as Extended Mixed Logical Dynamical (EMLD) systems in this paper. A Model Predictive Controller (MPC) based on the Mixed Integer Quadratic Programming (MIQP) is designed for the MLD and EMLD models of the DC-DC boost converter considering all possible dynamics in Continuous and Discontinuous Conduction Modes of operations (CCM-DCM). The simulation results show the satisfactory... 

    A new method to control heat and mass transfer to work piece in a GMAW process

    , Article Journal of Process Control ; Volume 22, Issue 6 , 2012 , Pages 1087-1102 ; 09591524 (ISSN) Mousavi Anzehaee, M ; Haeri, M ; Sharif University of Technology
    2012
    Abstract
    It is proposed to employ melting rate, heat input, and detaching droplet diameter as controlled variables to control heat and mass transfer to work piece in a gas metal arc welding process. A two-layer architecture with cascade configuration of PI and MPC controllers is implemented to incorporate existing constraints on the process variables, improve transient behavior of the closed-loop responses and reduce interaction level. Computer simulation results are presented to indicate usefulness of the proposed controlled variables selection and applying two-layer control architecture to control heat and mass transfer to work piece