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transient-response
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Total 23 records
Determination of Number and Location of Models to Improve Transient Response in a Multi-model Adaptive Control
, M.Sc. Thesis Sharif University of Technology ; Haeri, Mohammad (Supervisor)
Abstract
In recent decays, multiple model controllers have been attracted much attention due to their essential ability to control of non-linear systems with wide operating ranges. Number and location of models are two important factors. In this research an algorithm for determining number of models and their locations has been proposed which can be counted as an extension to existing algorithms. Utilizing the proposed algorithm, the minimum number of models which achieve closed-loop stability can be determined. If transient response of non-linear system with these models be not satisfactory, the number of models are increased by one using Binary Search method, and consequently the location of models...
Improving Transient Response in Data-Driven Control Systems
, M.Sc. Thesis Sharif University of Technology ; Tavazoei, Mohammad Saleh (Supervisor)
Abstract
The term "data-driven" was first introduced in computer science and has entered the vocabulary of controlled engineering in recent years. So far, several classes of data-driven-control (DDC) methods have been introduced, which are identified by different names in the literature such as data-driven control, data-based control, modeless control, model-free adoptive control, iterative feedback tuning and virtual reference feedback tuning.Data-driven control includes all control theories and methods in which the controller directly and using the input-output data of the control system or knowing the processed data and without explicit knowledge of the mathematical model of the system (unlike...
An analytical solution for dynamic behavior of thick doubly curved functionally graded smart panels
, Article Composite Structures ; Vol. 107, issue , January , 2014 , p. 88-102 ; Askari Farsangi, M. A ; Sharif University of Technology
Abstract
In this paper, an analytical solution is presented for free vibration and dynamic behavior of doubly curved laminated shell consisting of a functionally graded core layer and surface attached functionally graded piezoelectric layers. Shell through-thickness kinematics is based on higher order shear deformation theory of shells, whereas a quadratic variation is assumed for electric potential. Using Hamilton's principle and Maxwell's equation, the governing equations of motion under mechanical loads are derived as seven highly coupled partial differential equations. Implementing Laplace transformation, doing few mathematical operations and using Laplace inverse method, time dependencies of...
Small-signal modeling and fast response control strategy for DCVM Cúk converters in PFC applications.انجام شد
, Article Conference Proceedings - IEEE Applied Power Electronics Conference and Exposition - APEC ; 2011 , Pages 1795-1802 ; 9781424480845 (ISBN) ; Karimi, Y ; Zolghadri, M. R ; Ahmadian, M ; Moayedi, A ; Davoudi, A ; Sharif University of Technology
Abstract
Cúk Converter operating in discontinuous capacitor voltage mode is an inherent PFC converter in which, unity power factor can be achieved using constant duty cycle and switching frequency. In this paper, a reduced-order switch network modeling technique is applied to Cúk converter operating in DCVM in order to derive small-signal model of the converter assuming a dc voltage source as the input source of the converter. This model is extended to derive the small-signal behavior of the converter while operating as a PFC converter. The validity of the proposed model is confirmed by both simulation and experimental results. Afterwards, a new control strategy is proposed in which switching...
Smooth switching in a scheduled robust model predictive controller
, Article Journal of Process Control ; Volume 31 , 2015 , Pages 55-63 ; 09591524 (ISSN) ; Haeri, M ; Sharif University of Technology
Elsevier Ltd
2015
Abstract
Abstract This paper proposes a bumpless transfer method to overcome the problem of switching jumps in a scheduled robust model predictive control approach. A scheduled robust model predictive controller implements a set of local robust model predictive controllers based on an on-line switching strategy. This method could enlarge the domain of attraction efficiently but the transient response might be hampered by spikes appearing at the moment of switching between adjacent local controllers. The proposed algorithm could enhance the transient response by implementing some intermediate controllers augmented to the main control scheme to solve the problem without needing more computation. The...
Model reference control of PMSM drive systems based on model predictive control
, Article 6th Annual International Power Electronics, Drive Systems, and Technologies Conference, PEDSTC 2015, 3 February 2015 through 4 February 2015 ; 2015 , Pages 395-399 ; 9781479976539 (ISBN) ; Fazli, M ; Tahami, F ; Sharif University of Technology
Abstract
Servo drive systems require a fast dynamic response for position control applications. Conventional cascade control structure has sluggish response due to bandwidth limitations on speed and current control loop. To achieve a fast output response, model reference adaptive control methods can be used to remove the dynamics of inner control loops. In this paper, feed-forward signals are generated using model predictive control which is combined with the conventional cascade structure. Using this approach, a fast transient response and satisfactory tracking ability can be achieved. The proposed control configuration is verified by the simulation results
Design, construction and simulation of a multipurpose system for precision movement of control rods in nuclear reactors
, Article Annals of Nuclear Energy ; Volume 37, Issue 12 , 2010 , Pages 1659-1665 ; 03064549 (ISSN) ; Aghanajafi, C ; Sadoughi, S ; Sharifloo, N ; Sharif University of Technology
Abstract
This article presents the design and implementation of a microcontroller-based system for the automatic movement of control rods in nuclear reactors of either power or research types. This system is controlled automatically, is linked to a personal computer system, and has manual controlling ability as well. The important features of this system are: automatic scram of the control rods, activation of alarm in emergency situations, and the ability to tune the control rod movement course both upwards and downwards. In this system, a small tank has been improvised as a coolant reservoir for pool type reactors such as Tehran Research Reactor and its water level is continuously adjusted by...
Coordinated control approaches for low-voltage ride-through enhancement in wind turbines with doubly fed induction generators
, Article IEEE Transactions on Energy Conversion ; Volume 25, Issue 3 , 2010 , Pages 873-883 ; 08858969 (ISSN) ; Parniani, M ; Sharif University of Technology
Abstract
This paper deals with the coordinated control of rotor- and grid-side converters in wind turbines with doubly fed induction generators (DFIGs) to improve the low-voltage ride-through capability. The rotor-side converter control and additional equipment, called stator damping resistor, are used to limit the rotor inrush current and to reduce the oscillations and settling time of DFIG transient response during the voltage dip. Also, the grid-side converter is controlled to limit the dc-link overvoltage during the voltage drop. It is found that the dynamics of the grid-side converter and dc-link voltage exhibit nonminimum phase behavior, and thus there is an inherent limitation on the...
Efficient control scheme of wind turbines with doubly fed induction generators for low-voltage ride-through capability enhancement
, Article IET Renewable Power Generation ; Volume 4, Issue 3 , May , 2010 , Pages 242-252 ; 17521416 (ISSN) ; Parniani, M ; Sharif University of Technology
2010
Abstract
As the penetration of wind power in electrical power systems increases, it is required that wind turbines remain connected to the grid and actively contribute to the system stability during and after grid faults. This study proposes an efficient control strategy to improve the low-voltage ride-through (LVRT) capability in doubly fed induction generators (DFIGs). The proposed scheme consists of passive and active LVRT compensators. The passive compensator is based on a new crowbar arrangement located in series with stator windings. It considerably reduces the rotor inrush current at the instants of occurring and clearing the fault. The active LVRT compensator is realised through rotor voltage...
Periodic characteristic ratio (PCR) method: An alternative method to determine the characteristic polynomial
, Article Mathematics and Computers in Simulation ; Volume 80, Issue 9 , May , 2010 , Pages 1841-1853 ; 03784754 (ISSN) ; Haeri, M ; Sharif University of Technology
2010
Abstract
This paper proposes an alternative method to determine the characteristic polynomial based on closed loop desired transient response. To develop the method, we have found optimal characteristic rations in simple arrangement of these parameters via performance map method. Despite its simplicity, the resulted system exhibits better transient response in comparison with the systems obtained from existing methods of determining the characteristics polynomials. Numerical simulations are used to illustrate the specifications of the proposed method
Investigation of a nonlinear dynamic hydraulic system model through the energy analysis approach
, Article Journal of Mechanical Science and Technology ; Volume 23, Issue 11 , 2010 , Pages 2973-2979 ; 1738494X (ISSN) ; Ehramianpour, M ; Mohammadi, M ; Sharif University of Technology
Abstract
The dynamics of a pressure regulator valve have been studied using the through Bondgraph simulation technique. This valve consists of several elements that can transmit, transform, store, and consume hydraulic energy. The governing equations of the system have been derived from the dynamic model. In solving system equations numerically, various pressure-flow characteristics across the regulator ports and orifices have been taken into consideration. This simulation study identifies some critical parameters that have significant effects on the transient response of the system. The results have been obtained using the MATLAB-SIMULINK environment. The main advantage of the proposed methodology...
A proportional-resonant controller-based wireless control strategy with a reduced number of sensors for parallel-operated UPSs
, Article IEEE Transactions on Power Delivery ; Volume 25, Issue 1 , 2010 , Pages 468-478 ; 08858977 (ISSN) ; Caglar Onar, O ; Mokhtari, H ; Khaligh, A ; Sharif University of Technology
Abstract
In this paper, a novel droop method to control the power sharing of parallel uninterruptible-power-supply (UPS) systems is presented. In a clear-cut contrast to the previously reported works, the controller is a proportional-resonant controller which ensures good transient response and steady-state objectives. Furthermore, the need for sensing the output current for the power-sharing control is removed by implementing it in a software routine. This brings a less complicated and less expensive structure in which the number of feedback sensors is reduced from three to two. The droop paralleling strategy is based on the drop in the inverter output frequency and amplitude. The application of...
Transient response of the flexible blade of horizontal-axis wind turbines in wind gusts and rapid yaw changes
, Article Energy ; Volume 145 , 2018 , Pages 261-275 ; 03605442 (ISSN) ; Sekandari, M ; Sharif University of Technology
Elsevier Ltd
2018
Abstract
In this paper, the aeroelastic analysis of a large scale wind turbine rotor is performed with the aim of studying transient performance of turbine in extreme wind conditions, such as wind gusts and rapid yaw changes. The effect of the presence and/or lack of blade pitch control system on output power, rotor thrust, and blade deformation in sudden change of wind speed are investigated. The NREL 5 MW offshore wind turbine is used as the baseline case. In this regard, the modal approach is implemented for modeling the flexible blade structure with tension, bending and torsion degrees of freedom. The unsteady vortex lattice method is employed to obtain the aerodynamic loads. Moreover, the...
On discretization of second-order derivatives in smoothed particle hydrodynamics
, Article World Academy of Science, Engineering and Technology ; Volume 40 , 2009 , Pages 243-246 ; 2010376X (ISSN) ; Fayazbakhsh, M. A ; Taghizadeh Manzari, M ; Sharif University of Technology
2009
Abstract
Discretization of spatial derivatives is an important issue in meshfree methods especially when the derivative terms contain non-linear coefficients. In this paper, various methods used for discretization of second-order spatial derivatives are investigated in the context of Smoothed Particle Hydrodynamics. Three popular forms (i.e."double summation","second-order kernel derivation", and"difference scheme") are studied using one-dimensional unsteady heat conduction equation. To assess these schemes, transient response to a step function initial condition is considered. Due to parabolic nature of the heat equation, one can expect smooth and monotone solutions. It is shown, however in this...
On model predictive control of quasi-resonant converters
, Article Journal of Circuits, Systems and Computers ; Volume 18, Issue 7 , 2009 , Pages 1167-1183 ; 02181266 (ISSN) ; Ebad, M ; Sharif University of Technology
2009
Abstract
In this paper, different model predictive control synthesis frameworks are examined for DCDC quasi-resonant converters in order to achieve stability and desired performance. The performances of model predictive control strategies which make use of different forms of linearized models are compared. These linear models are ranging from a simple fixed model, linearized about a reference steady state to a weighted sum of different local models called multi model predictive control. A more complicated choice is represented by the extended dynamic matrix control in which the control input is determined based on the local linear model approximation of the system that is updated during each sampling...
Transient response of porous FG nanoplates subjected to various pulse loads based on nonlocal stress-strain gradient theory
, Article European Journal of Mechanics, A/Solids ; Volume 74 , 2019 , Pages 210-220 ; 09977538 (ISSN) ; Mohasel Afshari, B ; Barati, M. R ; Hamouda, A. M. S ; Sharif University of Technology
Elsevier Ltd
2019
Abstract
Based on nonlocal strain gradient theory (NSGT), transient behavior of a porous functionally graded (FG) nanoplate due to various impulse loads has been studied. The porous nanoplate has evenly and unevenly distributed pores inside its material structure. Impulse point loads are considered to be rectangular, triangular and sinusoidal types. These impulse loads lead to transient vibration of the nanoplate which is not studied before. NSGT introduces a nonlocal coefficient together with a strain gradient coefficient to characterize small size influences due to non-uniform stress and strain fields. Galerkin's approach has been performed to solve the governing equations and also inverse Laplace...
A novel approach for robust control of single-link manipulators with visco-elastic behavior
, Article 10th International Conference on Computer Modelling and Simulation, EUROSIM/UKSim2008, Cambridge, 1 April 2008 through 3 April 2008 ; 2008 , Pages 685-690 ; 0769531148 (ISBN); 9780769531144 (ISBN) ; Jahed, M ; Sharif University of Technology
2008
Abstract
Overwhelming number of control laws has been studied for control of robot manipulators with rigid links and joints. However controllers designed under this assumption may not accurately control the manipulator link due to visco-elastic properties that appear in the link behavior. In this study, a novel approach for robust control of a single-link manipulator is presented to force the link to have rigid motions, while it has visco-elastic behavior. In this regard, initially robot dynamics is extracted, followed by the design of four appropriate controllers through the loop-shaping approach. The obtained model is first represented in state space, however later converted to transfer function...
An extended dynamic matrix control design for quasi-resonant converters
, Article 2008 IEEE 2nd International Power and Energy Conference, PECon 2008, Johor Baharu, 1 December 2008 through 3 December 2008 ; January , 2008 , Pages 1147-1151 ; 9781424424054 (ISBN) ; Ebad, M ; Sharif University of Technology
2008
Abstract
The Extended dynamic matrix control (EDMC) has been proved to extend the existing version of the linear model predictive control to control nonlinear systems. In this method, the control input is determined based on the linear model approximation of the system that is updated during each sampling interval. In this paper, by using this method, a new control scheme for quasi-resonant converters is described. This control offers an excellent transient response and a good tracking. © 2008 IEEE
Adaptive critic-based neurofuzzy controller for the steam generator water level
, Article IEEE Transactions on Nuclear Science ; Volume 55, Issue 3 , 2008 , Pages 1678-1685 ; 00189499 (ISSN) ; Boroushaki, M ; Sharif University of Technology
2008
Abstract
In this paper, an adaptive critic-based neurofuzzy controller is presented for water level regulation of nuclear steam generators. The problem has been of great concern for many years as the steam generator is a highly nonlinear system showing inverse response dynamics especially at low operating power levels. Fuzzy critic-based learning is a reinforcement learning method based on dynamic programming. The only information available for the critic agent is the system feedback which is interpreted as the last action the controller has performed in the previous state. The signal produced by the critic agent is used alongside the backpropagation of error algorithm to tune online conclusion parts...
An optimal fractional order controller for an AVR system using particle swarm optimization algorithm
, Article 2007 Large Engineering Systems Conference on Power Engineering, LESCOPE'07, Montreal, QC, 10 October 2007 through 12 October 2007 ; January , 2007 , Pages 244-249 ; 9781424415830 (ISBN) ; Zamani, M ; Sadati, N ; Parniani, M ; Sharif University of Technology
2007
Abstract
Application of Fractional Order PID (FOPID) controller to an Automatic Voltage Regulator (AVR) is presented and studied in this paper. An FOPID is a PID whose derivative and integral orders are fractional numbers rather than integers. Design stage of such a controller consists of determining five parameters. This paper employs Particle Swarm Optimization (PSO) algorithm to carry out the aforementioned design procedure. A novel cost function is defined to facilitate the control strategy over both the time-domain and the frequencydomain specifications. Comparisons are made with a PID controller from standpoints of transient response, robustness and disturbance rejection characteristics. It is...