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Home>Products>Journal and Reviews>I.RE.A.CO.>Latest issue International Review of Automatic Control (Theory and Applications) - November 2009 - Papers
International Review of Automatic Control - Papers
Vol. 2. n. 6, pp. 614-620
Abstract - One of the important problems in AR model estimation is the model order selection problem. There are many model order selection criteria that have been applied to the AR order selection problem. Some of these criteria such as FPE, FSC, MFSC, and FPEF are typically based on minimizing the prediction error, but these criteria are not actually optimal in the sense of prediction error. Here, we will provide conditions under which optimal predictive order selection criterion for AR model will be achieved. Then, we will apply this criterion to simulated data and compare its performance with that of other AR order selection criteria. Simulation results show that the new criterion has lower prediction error than the other AR order selection criteria. Copyright © 2009 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Model order selection, AR model, Prediction error.
Vol. 2. n. 6, pp. 621-627
Abstract - This note deals with the design of H2 gain scheduled controllers for Linear Parameter Varying (LPV) systems with rational dependence on the varying parameters. Firstly, new sufficient LMI-based conditions for H2 performance analysis are proposed based on an equivalent affine descriptor LPV system. Accordingly, new LMI conditions for the H2 gain scheduled controller synthesis problem are proposed. Finally, a numerical example highlights the effectiveness of the proposed conditions. Copyright © 2009 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Linear Parameter Varying (LPV) systems, H2 control, LMI, gain scheduling.
by Ezzeddine Khadri, Moncef Tagina Vol. 2. n. 6, pp. 628-637
Abstract - In this article, a model-based diagnosis method is developed for disturbed hybrid systems. The considered systems comprise both discrete and continuous dynamics. So, the first part of the paper describes the design of a Proportional-Integral (PI) observer that allows the minimization of perturbation influences. Secondly, a robust hybrid observer is proposed for a hybrid system with unknown disturbances and faults. The robust hybrid observer consists of a discrete observer for mode identification and a continuous observer for continuous state estimation and mode transition detection. It is shown that the mode can be identified correctly and the continuous state estimation error is exponentially uniformly bounded. Robustness to model uncertainties and disturbances can be guaranteed for the hybrid observer by use of PI observer. This kind of observer is then used to construct banks of observers allowing to generate residuals. Occurrency of faults is then revealed by analysing these residuals. Lastly, on the basis of the robust hybrid observer, a robust fault detection and isolation scheme is presented also in the paper. Simulations of a hybrid two-tank system show the proposed approach is effective. Copyright © 2009 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Hybrid systems; Robust hybrid observers; Robustness; Fault detection; PI observer.
Vol. 2. n. 6, pp. 638-644
Abstract - In this paper, we present a novel method of control of complex systems with limited and unknown delay. It operates the Padé approximation and is based on the extension of the multi model approach to systems represented by a state equation. The success which has been achieved by the multimodel approach is essentially linked to its ability to represent complex systems by simple models forming the basis of models. In our case, these models are stabilized, each separately, with a state feedback control guaranteeing the same pole placement for the system. In real time, is makes a calculation of validities that determines at each moment the degree of validity of each basic model. At the same time, it generates the control for each. A control of the complex process with limited and unknown delay is obtained by fusion of partial controls weighted by the validity indexes of respective models. The development stages of this control method is detailed in this paper; its validation and robustness are verified on a benchmark. Copyright © 2009 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Systems with limited unknown delay, Multimodel approach, Theorem of Kharitonov, Calculation of validity, State-feedback control, Control of systems with delay, Approximation of Padé.
Vol. 2. n. 6, pp. 645-653
Abstract - In the paper we consider an electric drive having static load torque with a constant component and a speed proportional component, in the hypothesis of constant inertia moment and of proportionality between the electromagnetic torque and the load current. Using variational calculus, optimally condition and expression of optimal control and extremal trajectory are determined, which ensures the minimum of energy losses caused by the load current through a Joule effect in the acceleration processes. Using numerical computer we can obtain graphical representation of these variables as time functions. Copyright © 2009 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Analytic and numerical model, Electric drives, Optimal control, Variational calculus.
Vol. 2. n. 6, pp. 654-660
Abstract - This paper discusses a sampled-data control design for fuzzy systems with discrete and distributed delays. The zero-order control input can be represented as a delayed input. Then, the closed-loop system with such an input becomes a system with time-varying delay. Sufficient conditions for the closed-loop system to be stable are given in terms of linear matrix inequalities (LMIs). Based on such conditions, we propose a sampled-data control design for a fuzzy system with discrete and distributed delays. Copyright © 2009 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Takagi-Sugeno Fuzzy Model, Sampled-Data Control, Delay Systems.
Vol. 2. n. 6, pp. 661-667
Abstract - The aim of this paper is to improve the integration of wind energy in existing power grids, more flexible transmission systems are required to accommodate the intermittent nature of wind. The synchronous generator normally has easy starting duty as it is brought up to speed by a prime mover. Then the rotor excitation winding is powered with DC current. We have the synchronous generator with a DC rectifier on the machine side and the inverter on the grid side between them the “DC intermediate circuit”. This system is characterized by a large speed range of the rotor. The fast development of power electronics in the past few decades made significant progress in electric power transmission technology which made it possible to use the system stated above and gained a reduction in harmonics current in the machine stator, we introduce a small-sized passive LC filter for the purpose of eliminating high-frequency shaft voltage and grid current from a grid inverter driven by a voltage-source pulse width-modulation controlled with SVM.. In order to verify the validity of the proposed method, a dynamic model of the proposed system has been simulated, for different operating points, to demonstrate the performance of the system. Copyright © 2009 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Synchronous Generator, PWM Rectifier, LC Filter, Wind Power, SVM.
Vol. 2. n. 6, pp. 668-678
Abstract - Permanent magnet synchronous motors (PMSM) are widely used in many applications that require rapid torque response and high-performance criteria such as robotic manipulators, CNC machine tools, elevators, electric vehicle and many other applications in the area of mechatronics. In this paper, the position control of a PMSM based on Matlab/Simulink software package is studied and as a challenging application, the developed control schemes are simulated for a two degree of freedom (2-DOF) direct-drive (DD) planar robotic arm. First, the field-oriented PMSM servo drive is implemented and the dynamic model of the system at nominal conditions is investigated. Then a 2-DOF direct drive robot is taken into consideration with two PMSMs as an example driving each link. Linear and nonlinear controllers are designed to track any given position trajectory under varying load effects. The aim of the controllers is to track the desired position trajectory with minimum error in both transient and steady state. The linear controllers are PD and PID type while the nonlinear controller is, a nonlinear model based controller, known as proportional-derivative-plus (PD+) controller. The performance of these controllers is tested under different load and reference conditions and compared for tracking performance. The superiority of PID and PD+ controllers is discussed based on the system operating conditions. Copyright © 2009 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Permanent magnet synchronous motor, Direct drive arm, Two degree of freedom, Position control, PD, PID and PD+ controller.
Vol. 2. n. 6, pp. 679-684
Abstract - A model reference adaptive control (MRAC) of speed for series-connected two-motor drive is presented in this paper. The system consists of a six-phase induction machine and a three-phase induction machine. The stators windings of both machines are connected in series in appropriate manner. Modeling and vector control of a series-connected two-motor drive supplied by a single inverter are presented in the first part. Then, the dynamic decoupling of each machine from the group is obtained using the indirect vector control algorithm. Mathematical modeling of the multi-machine system showed the possibility of independent control of each machine in the group. The proposed controller uses a MRAC control to satisfy the hyperstability condition for tracking care of the load and multi-machine parameters changes of the drive. The simulation results show that the closed-loop system performances are satisfactory using the proposed adaptive controller. Copyright © 2009 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Multi-machine system, Vector control and model reference adaptive control.
Vol. 2. n. 6, pp. 685-692
Abstract - This paper addresses the stabilization and performance of the voltage regulator by using the theory of the optimal control. Proposes a new technique, based on pole placement using optimal regulators, to overcome the difficulties of specifying the weighting matrices Q and R. The design method employs successive shifting of an either real pole or a pair of complex conjugate poles at a time. The proposed technique builds Q and R in such a way that the system's response also obeys conventional criteria for the system pole location. The effectiveness of the proposed method is illustrated by numerical examples. Copyright © 2009 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Power Systems, Voltage regulator, Optimal Control, Weighting Matrices.
Vol. 2. n. 6, pp. 693-699
Abstract - Shunt flexible AC transmission system (FACTS) devices are used for controlling transmission voltage, power flow, reducing reactive losses, and damping of power system oscillations for high power transfer levels. The paper explains the relationship between the 50-Hz resonance and the voltage stability phenomena and presents the approach for solving them in a long AC interconnection. It also describes the criteria used for the development of the configuration and control functions of the new Static VAr Compensator (SVC) at the 400 kV line terminals. A brief summary of the SVC design features is also given. Results of transient studies using MATLAB and EMTDC simulations and frequency-domain analysis are presented to demonstrate the problems and the effectiveness of the adopted solutions. Copyright © 2009 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: FACTS, SVC, Resonances, Voltage Stability.
Vol. 2. n. 6, pp. 700-707
Abstract - Accurate wind power energy forecasting in the electric grid supply provides a significant tool for optimizing operating costs. In this paper, wind power forecasting of one turbine at the Sidi Daoud wind farm (Tunisia) is treated by the Artificial Neural Network (ANN) technique. Measured data from this wind farm have been used to develop an ANN solution. This model shows a satisfactory estimation of wind power production under variable wind conditions. After filtering and treating measured data, the most influential are considered as ANN inputs: specifically the wind speed and direction, the temperature, the pressure and the previous power production. As weather prediction is not available at this farm, a recurrent Neural Network is proposed using a real data base to predict the wind speed and direction for two hours ahead. This prediction allows the creation of a short-term wind power energy forecast. Results thus achieved are tested with real data. Copyright © 2009 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Prediction, Wind Power, Data Filtering, Artificial Neural Networks.
Vol. 2. n. 6, pp. 708-714
Abstract - In the deregulated power system environment, to maintain system security and power quality, ancillary services are obtained by the system operator in the ancillary service markets. Under the deregulated environments, the Automatic generation control (AGC) is also required to be innovated for the adaptation to be market systems with several kinds of the bidding strategies. The load frequency control (LFC) problem has been a major subject in electrical power system design/operation and is becoming more significant recently with increasing size, changing structure and complexity in interconnected power systems. In practice LFC systems use simple Integral (I) controller. However, since the I control parameters are usually tuned based on classical or trial-and-error approaches, they are incapable of obtaining good dynamic performance for various load changes scenarios in multi-area power system. For this reason, in this study the I control parameters are tuned based on Particle Swarm Optimization (PSO) algorithm method for LFC control in two-area power system. Because PSO is an optimization method, therefore, in the uncertainty area of controller parameters, finds the best parameters for controller and obtained controller is an optimal controller. In this paper, the dynamical response of the load frequency control problem in the deregulated environment is improved with a pragmatic viewpoint. A two-area power system example is given to illustrate proposed methods. To show effectiveness of proposed method and compare the performance of optimized I type controllers using PSO and GA, several time-domain simulation for various load changes scenarios are presented. Simulation results emphasis on the better performance of optimized I controller using PSO in compared to optimized I controller using GA in LFC. Copyright © 2009 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Automatic generation control (AGC), Load frequency control (LFC), Particle swarm optimization (PSO), Deregulated power systems.
Vol. 2. n. 6, pp. 715-724
Abstract - Applying the optimal control to the large scale systems is difficult due to their high dimensionality, nonlinearity, coupling, time delay and etc. in this paper two near optimum methods (aggregation and perturbation methods) to control the large scale systems are introduced and for each of them the optimum control rule is calculated. The proposed methods are implemented on a large scale system (synchronous generator) as a case study. To confirms the effectiveness of the proposed methods MATLAB/Simulink based simulations are carried out. Comparing the results of simulation with real system ones without dimension reduction, shows that they are acceptable. With respect to the results, it is possible to use them to control the large scale systems optimally. Copyright © 2009 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Near Optimum Control, Large Scale Systems, Aggregative, Perturbation.
Vol. 2. n. 6, pp. 725-730
Abstract - In this paper an attempt has been made to introduce a powerful strategy for enhancing the dynamic response of load frequency control (LFC) systems for two-area reheat thermal power networks. In the proposed method fuzzy tuning control scheme accompanied by thyristor-controlled phase shifter (TCPS) located on tie-line are employed. The simulation results show that the proposed strategy will damp the frequency and tie-line power oscillations due to sudden load change. Copyright © 2009 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Thyristor-controlled phase shifter (TCPS), load frequency control (LFC), Fuzzy tuning.
Vol. 2. n. 6, pp. 731-737
Abstract - This work deals with fault diagnosis of two-tank process based on analytical redundancy. Parity space and observers approaches are used to generate residuals. Since the studied process is a two time scale one, a singularly perturbed model is so defined. Consequently, a reduced residual, based on the slow reduced model, allows fault detection. Copyright © 2009 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Dynamic Parity Space, Fault Diagnosis, Observer, Reduced Residual, Singularly Perturbed System.
Vol. 2. n. 6, pp. 738-746
Abstract - Mechanical systems generally consist of three components; an actuator, a load and a power transmission mechanism such as the lead screw and gear coupling. Although there have been many studies on the controller design for mechanical systems with nonlinear friction, the compliance of the transmission mechanism has barely been considered. Because the effect of nonlinear friction is significant when the transmission mechanism has low stiffness, the compliance of the transmission mechanism should be considered in the mechanical controller design in order to achieve the superior control performance. This paper presents a new approach to the controller design of mechanical systems with nonlinear friction by considering the compliance of the transmission mechanism. Because the effect of friction is generally unknown in advance, we design a robust controller based on a variable structure control that requires only the maximum magnitude of difference between the current value and one-sample past estimate of friction. The effectiveness of the proposed controller is demonstrated by comparative experimental results with a conventional controller. Copyright © 2009 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Mechanical Control, Robust Control, Nonlinear Friction, Variable Structure Control.
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