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    Optimal controller design for 3D manipulation of buoyant magnetic microrobots via constrained linear quadratic regulation approach

    , Article Journal of Micro-Bio Robotics ; Volume 15, Issue 2 , 2019 , Pages 105-117 ; 21946418 (ISSN) Pedram, A ; Nejat Pishkenari, H ; Sitti, M ; Sharif University of Technology
    Springer  2019
    Abstract
    We consider magnetic actuation and control of a spherical neutrally buoyant magnetic microrobot via magnetic coil setups and seek to design an optimal controller to reduce the required energy and coils’ currents. We showed that in currently employed setups, where the actuation frequency is few tens of Hertz, the nonlinear dynamics of the system can be well approximated by a set of linear constrained ones. The approximated model is obtained by consciously overlooking the rotational dynamics and the inertia terms in translational dynamics. We acquired the linear quadratic regulation (LQR) controller for the approximated model which is a constrained time-varying system. Finally, 3D manipulation... 

    Model-free LQR design by Q-function learning

    , Article Automatica ; Volume 137 , 2022 ; 00051098 (ISSN) Farjadnasab, M ; Babazadeh, M ; Sharif University of Technology
    Elsevier Ltd  2022
    Abstract
    Reinforcement learning methods such as Q-learning have shown promising results in the model-free design of linear quadratic regulator (LQR) controllers for linear time-invariant (LTI) systems. However, challenges such as sample-efficiency, sensitivity to hyper-parameters, and compatibility with classical control paradigms limit the integration of such algorithms in critical control applications. This paper aims to take some steps towards bridging the well-known classical control requirements and learning algorithms by using optimization frameworks and properties of conic constraints. Accordingly, a new off-policy model-free approach is proposed for learning the Q-function and designing the... 

    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
    Abstract
    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  

    Optimal station-keeping near Earth-Moon collinear libration points using continuous and impulsive maneuvers

    , Article Advances in Space Research ; Volume 52, Issue 12 , 2013 , Pages 2067-2079 ; ISSN: 02731177 Ghorbani, M ; Assadian, N ; Sharif University of Technology
    2013
    Abstract
    In this study the gravitational perturbations of the Sun and other planets are modeled on the dynamics near the Earth-Moon Lagrange points and optimal continuous and discrete station-keeping maneuvers are found to maintain spacecraft about these points. The most critical perturbation effect near the L1 and L2 Lagrange points of the Earth-Moon is the ellipticity of the Moon's orbit and the Sun's gravity, respectively. These perturbations deviate the spacecraft from its nominal orbit and have been modeled through a restricted five-body problem (R5BP) formulation compatible with circular restricted three-body problem (CR3BP). The continuous control or impulsive maneuvers can compensate the... 

    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
    2010
    Abstract
    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... 

    Design a LQG power system stabilizer for bistun power plant

    , Article AUPEC'09 - 19th Australasian Universities Power Engineering Conference: Sustainable Energy Technologies and Systems, 27 September 2009 through 30 September 2009, Adelaide ; 2009 ; 9780863967184 (ISBN) Keivanian, R ; Hossein Vahabie, A ; Nademi, H ; Ranjbar, A ; Sharif University of Technology
    Abstract
    Design of a classical controller is based on output feedback and structure of the controller. From modern control point of view, the information of input signals, output signals and internal behavior of the system are presented in state space model. In this paper, modern control is used to increase small-disturbance stability of power systems. Although many of existing power plants prefer to use classical Power System Stabilizers (PSS), these controllers have their own problems. Digital implementation of modern controllers is considered as a good advantage of modern PSS. In this paper, a modern control based PSS is designed for Bistun power plant and its output results are compared to the... 

    Designing market-based control with a genetic algorithm

    , Article Scientia Iranica ; Vol. 21, Issue. 6 , 2014 ; ISSN: 10263098 Khorsand, S ; Amini, F ; Sharif University of Technology
    Abstract
    Semi-active devices are low-cost as well as small and by changing the properties of low-power intensive structures, the aims of control are accomplished. On the other hand, the limited control force which can be applied to the structure for each damper causes more dampers to be used in the structures compared to the larger and stronger control devices which are more costly. These dampers coupled with sensors and the structure themselves make a complex dynamic system which is best controlled by a decentralized method such as Market-Based Control (MBC). In MBC, the actuators and the supply energy are modeled as buyer and seller respectively in the market place. To define the demand function of... 

    Optimal state-feedback design for non-linear feedback-linearisable systems

    , Article IET Control Theory and Applications ; Volume 5, Issue 2 , 2011 , Pages 323-333 ; 17518644 (ISSN) Esfahani, P. M ; Farokhi, F ; Karimi-Ghartemani, M ; Sharif University of Technology
    2011
    Abstract
    This paper addresses the problem of optimal state-feedback design for a class of non-linear systems. The method is applicable to all non-linear systems which can be linearised using the method of state-feedback linearisation. The alternative is to use linear optimisation techniques for the linearised equations, but then there is no guarantee that the original non-linear system behaves optimally. The authors use feedback linearisation technique to linearise the system and then design a state feedback for the feedback-linearised system in such a way that it ensures optimal performance of the original non-linear system. The method cannot ensure global optimality of the solution but the global... 

    Control of a non observable double inverted pendulum using a novel active learning method based state estimator

    , Article Proceedings - UKSim 4th European Modelling Symposium on Computer Modelling and Simulation, EMS2010, 17 November 2010 through 19 November 2010 ; 2010 , Pages 21-26 ; 9780769543086 (ISBN) Ghatre Samani, A ; Bagheri Shouraki, S ; Eghbali, R ; Ghomi Rostami, M ; Sharif University of Technology
    Abstract
    In this paper a novel fuzzy approach exploiting Active Learning Method is employed in order to estimate the immeasurable states required to control a non-observable double inverted pendulum. Active Learning Method (ALM) is a fuzzy modeling method which exploits Ink Drop Spread (IDS) as its main engine. IDS is a universal fuzzy modeling technique which is very similar to the way human brain processes different phenomena. The ALM system is trained by the data obtained from Linear Quadratic Regulator (LQR) controller. LQR uses an optimal control approach which under certain conditions guarantees robustness. Instead of an expert's knowledge, the LQR controller output is used as a priori... 

    Designing a LQR controller for an electro-hydraulic-actuated-clutch model

    , Article Proceedings of 2016 2nd International Conference on Control Science and Systems Engineering, ICCSSE 2016, 27 July 2016 through 29 July 2016 ; 2016 , Pages 82-87 ; 9781467398725 (ISBN) Pourebrahim, M ; Selk Ghafari, A ; Pourebrahim, M ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2016
    Abstract
    During the past decade, Electro-Hydraulic system has performed a significant role in industrial engineering as an actuator for high performance and precision positioning applications. In this case, many control methods have been developed for an electro-hydraulic actuated clutch. In this paper a Linear Quadratic Regulators (LQR) is proposed to trajectory control of a wet clutch actuated by a hydraulic servo valve mechanism. Simulation study was performed using linearized mathematical model of the system implemented in MATLAB software. Based on the simulation results performance of the proposed controller was evaluated and discussed  

    Hardware-in-the-loop optimization of an active vibration controller in a flexible beam structure using evolutionary algorithms

    , Article Journal of Intelligent Material Systems and Structures ; Vol. 25, issue. 10 , 2014 , p. 1211-1223 Nobahari, H ; Hosseini Kordkheili, S. A ; Afshari, S. S ; Sharif University of Technology
    Abstract
    In this study, active vibration control of a cantilevered flexible beam structure equipped with bonded piezoelectric sensor/actuators is investigated. The linear quadratic regulator technique together with an observer is adopted to design the controller as well as to provide the full-state feedback. Two different approaches are subsequently used for simultaneously integrated optimization of the controller and observer parameters. In the first approach, a linear experimental model of the system is obtained using identification techniques, and the optimization is then performed based on a computer simulation of the system. However, in the second approach, a hardware-in-the-loop optimization... 

    Model predictive orbit control of a Low Earth Orbit satellite using Gauss's variational equations

    , Article Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering ; Vol. 228, issue. 13 , Oct , 2014 , p. 2385-2398 Tavakoli, M. M ; Assadian, N ; Sharif University of Technology
    Abstract
    In this paper, an autonomous orbit control of a satellite in Low Earth Orbit is investigated using model predictive control. The absolute orbit control problem is transformed to a relative orbit control problem in which the desired states of the reference orbit are the orbital elements of a virtual satellite which is not affected by undesirable perturbations. The relative motion is modeled by Gauss's variational equations including J2 and drag perturbations which are the dominant perturbations in Low Earth Orbit. The advantage of using Gauss's variational equations over the Cartesian formulations is that not only the linearization errors are much smaller, but also each orbital element can be... 

    Optimal tuning of sliding mode controller parameters using LQR input trend

    , Article IS'2012 - 2012 6th IEEE International Conference Intelligent Systems, Proceedings ; 2012 , Pages 297-303 ; 9781467327824 (ISBN) Azad, R. K ; Banazadeh, A ; Ahadi, A ; Sharif University of Technology
    2012
    Abstract
    This paper presents a novel method fortuning the parameters of an sliding mode (SM) controller to obtain near-optimal performance. In order to do so the Linear Quadratic Regulator (LQR) was implemented on a linearized system. The input history of the LQR was used as a reference to obtain an optimal space for sliding mode controller parameters. Afterwards, the optimal space boundaries were dedicated to Genetic Algorithm (GA) to search for the optimal parameter for the nonlinear model. Also, the center of the obtained optimal space was used as an initial guess to the Particle Swarm Optimization (PSO) Algorithm. The proposed algorithm was implemented to regulate SM controller for the attitude... 

    The design of LQR and fuzzy logic controller for a thermal system with large time delay

    , Article Proceedings of the 2010 International Conference on Mechanical, Industrial, and Manufacturing Technologies, MIMT 2010, 22 January 2010 through 24 January 2010 ; January , 2010 , Pages 293-298 ; 9780791859544 (ISBN) Zareh, S. H ; Jahromi, A. F ; Sarafan, A ; Akbar Khayyat, A. A ; Sharif University of Technology
    2010
    Abstract
    This paper will first describe the Linear Quadratic Regulator (LQR) and Fuzzy logic controller when the Proportional-Integral-Derivative (PID) controllers are inactive for procedures that have large delay time (LDT) in transfer stage. Therefore in those states, LQR and Fuzzy controllers perform better than the PID controllers. The constrained LQR is optimal and stabilizing. The solution algorithm is guaranteed to terminate in finite time with a computational cost that has a reasonable upper bound compared to the minimal cost for computing the optimal solution. The system determines the amount of fuel required from a fuzzy algorithm to arrive at the desired temperature. The parameters of the... 

    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
    Abstract
    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... 

    Nonlinear analysis and attitude control of a gyrostat satellite with chaotic dynamics using discrete-time LQR-OGY

    , Article Asian Journal of Control ; 2016 ; 15618625 (ISSN) Abtahi, S. M ; Sadati, S. H ; Salarieh, H ; Sharif University of Technology
    Wiley-Blackwell  2016
    Abstract
    Quasi-periodic and chaotic behavior, along with the control of chaos for a Gyrostat satellite (GS), is investigated in this work. The quaternion-based dynamical model of the GS is first derived, and then the influences of the reaction wheels in the GS structure, under the gravity gradient perturbation that causes a route to chaos through quasi-periodicity mechanism, is investigated. For the suppression of chaos in the system, a chaos control system with the quaternion feedback is designed for the GS based on the extension of the Ott-Grebogi-Yorke (OGY) method using the linearization of the Poincaré map. In the extended OGY controller, the Poincaré map is estimated using the Least Square... 

    Decentralized polynomial trajectory generation for flight formation of quadrotors

    , Article Proceedings of the Institution of Mechanical Engineers, Part K: Journal of Multi-body Dynamics ; Volume 231, Issue 4 , 2017 , Pages 690-707 ; 14644193 (ISSN) Sayyaadi, H ; Soltani, A ; Sharif University of Technology
    Abstract
    This paper deals with the decentralized polynomial trajectory generation for the formation flight of a leader-follower network of quadrotors. The proposed decentralized trajectory planning method guarantees stability of the formation in missions with aggressive trajectories or low information exchange frequencies or data loss. Moreover, designed formation protocol ensures robustness of the formation against variations of the network communication topology. First, quadrotor translational dynamics is represented as a quadruple integrator by linearizing and differentiating its equations of translational motion. Then, a formation control law for a leader-follower network of the quadruple... 

    Using optimal controller to parallel three-phase 4-leg inverters with unbalance loads

    , Article 1st IEEE International Conference on Power Electronics, Intelligent Control and Energy Systems, ICPEICES 2016, 4 July 2016 through 6 July 2016 ; 2017 ; 9781467385879 (ISBN) Nazaripouya, H ; Mokhtari, H ; Amiri, E ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2017
    Abstract
    In this paper; control and parallel operation of multi-modular 3-phase inverters are investigated. Active current sharing approach is selected as the fundamental control technique for parallel operation of inverters due to its high reliability. Among different methods for active current sharing; average load sharing is employed due to its acceptable stability. For this purpose; optimal control strategy and Linear Quadratic Regulator (LQR) method is proposed to parallel 3-phase 4-leg inverters. The system is modeled to be compatible and solvable with LQR equations. Using dq technique; 3-phase inverters are paralleled and controlled. The proposed method obtains both current sharing and voltage... 

    Wind-tolerant optimal closed loop controller design for a domestic atmospheric research airship

    , Article Mechanics Based Design of Structures and Machines ; 2020 Amani, S ; Pourtakdoust, S. H ; Pazooki, F ; Sharif University of Technology
    Taylor and Francis Inc  2020
    Abstract
    Airships are inherently sensitive to random atmospheric disturbances that could potentially make their data gathering and observation missions a formidable task. In this context robust closed loop feedback controllers are important. The present study is therefore focused on optimal feedback controller design of an indigenous domestically designed airship (DA) for added robustness against atmospheric disturbances. While the general airship six degrees of freedom (6DoF) governing equations of motion are mathematically nonlinear, one often needs to resort to local linearization methods to benefit from proven linear closed loop controller (CLC) design approaches. In this sense an optimal linear... 

    Wind-tolerant optimal closed loop controller design for a domestic atmospheric research airship

    , Article Mechanics Based Design of Structures and Machines ; Volume 50, Issue 6 , 2022 , Pages 2046-2066 ; 15397734 (ISSN) Amani, S ; Pourtakdoust, S. H ; Pazooki, F ; Sharif University of Technology
    Taylor and Francis Ltd  2022
    Abstract
    Airships are inherently sensitive to random atmospheric disturbances that could potentially make their data gathering and observation missions a formidable task. In this context robust closed loop feedback controllers are important. The present study is therefore focused on optimal feedback controller design of an indigenous domestically designed airship (DA) for added robustness against atmospheric disturbances. While the general airship six degrees of freedom (6DoF) governing equations of motion are mathematically nonlinear, one often needs to resort to local linearization methods to benefit from proven linear closed loop controller (CLC) design approaches. In this sense an optimal linear...