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Home>Products>Journal and Reviews>I.RE.A.CO.>Latest issue International Review of Automatic Control (Theory and Applications) - May 2008 - Papers
International Review of Automatic Control - Papers
by Z. Ding Vol. 1. n. 1, pp. 1-7
Abstract - This paper deals with asymptotic rejection of disturbances generated from nonlinear exosystems. The dynamic system is assumed to be linear. A new strategy for internal model design is proposed, based on a dynamic extension of the existing nonlinear observer design for the nonlinear exosystem. Additional filters are used to estimate the invariant manifold in the state space subject to the nonlinear disturbances generated from the exosystem. The proposed design for the internal model and control ensures that the state variable asymptotically converge to the invariant manifold, which implies that the designated output state asymptotically converge to zero. Copyright © 2008 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Disturbance Rejection, Nonlinear Systems, Internal Model Design.
Vol. 1. n. 1, pp. 8-14
Abstract - This paper presents the application of genetic algorithm (GA) techniques to identify the induction motor parameters. The induction motor is a non linear system, which made the identification of it's parameters more difficult in operating mode. Genetic algorithm is one of the best soft computing techniques used for this object. In this paper, the GA cost function is the weighted sum of stator current and rotor speed errors between the plant and the model of the induction motor. The weights of the cost function are also optimized in order to improve the speed convergence of the GA. The simulation results show that the identification method based on optimized cost function of GA is feasible and gives high precision. Copyright © 2008 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Genetic Algorithm, Induction Motor, Parameters Identification, Cost Function.
Vol. 1. n. 1, pp. 15-18
Abstract - The problem of design of a controller for a large-scale system is studied. The design objective is to achieve behavior comparable with the standard controller that is LQ optimal. On the other hand the amount of interconnections between subsystems should be kept as small as possible. This is guaranteed by solving of an optimization problem where the number of interconnections is minimized while the difference in the values of the cost functional for the standard and decentralized controller is a constraint. To find the value of the cost of the decentralized control in presence of interconnections one can use linear matrix inequalities. Copyright © 2008 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Decentralized control, decomposition, linear matrix inequalities.
Vol. 1. n. 1, pp. 19-27
Abstract - Evolutionary approximation of the Pareto front with hardware in the loop (HiL) is chosen as an alternative to the time-consuming simulation studies. Thanks to this approach problems of unmodeled plant dynamics are alleviated and additional manual on-line tuning is not required. On the other hand the presence of noise in the HiL setup affects the performance of evolutionary multi-objective optimization. This influence is strongly problem-dependent, therefore there are no general results. In this paper the robustness of the state-of-the-art multi-objective evolutionary NSGA-II algorithm is considered. The novel motor drive speed controller is evolutionary optimized on-line. The final Pareto-optimal solution is selected according to the designer’s preference. It shows to be superior to alternative trade-off solutions. Copyright © 2008 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Control Design, Multiobjective Optimization, Evolutionary Algorithms.
Vol. 1. n. 1, pp. 28-35
Abstract - This paper presents the synthesis of a variable structure controller to resolve the tracking problem for a class of second order nonlinear systems. The use of wavelet neural network (WNN) as a universal approximator is proposed to achieve fast convergence. This work develops an enhanced version of WNN to compensate the unknown dynamics, parameters uncertainties and a part of variable structure controller. Furthermore, the adaptation mechanism is derived from the stability analysis. To ensure the robustness of the closed loop system and to reduce the starting energy without deteriorating the tracking performances, a variable sliding surface is adopted. Moreover, the prior knowledge about the upper bounds is not needed neither for the external disturbances nor for the approximation errors. With the proposed controller, the global stability of the closed loop system is guaranteed in the sense of Lyapunov while of the tracking error is uniformly ultimately bounded (UUB). To demonstrate the effectiveness of the proposed approach, a simulation example is considered. Copyright © 2008 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Adaptive Control, Wavelet Neural Network Systems, Nonlinear Systems, Sliding Mode Control.
Vol. 1. n. 1, pp. 36-41
Abstract - A comparison between the sensorless Direct Torque Control (DTC) of the induction machine, based on different observers is proposed in this paper. The two DTC systems adopt alternatively a simplified extended Kalman filter and the Luenberger observer in order to estimate the speed of the induction machine and other quantities. PI regulator is used to regulate the estimate speed and improve the performances of the whole system. Simulation results show that the ripples of both torque and flux are reduced remarkable and a good dynamic of the speed and torque are achieved. Copyright © 2008 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: DTC, extended Kalman filter, Induction machine, Luenberger observer, sensorless.
Vol. 1. n. 1, pp. 42-48
Abstract - In this paper, the author studied the introduction of fuzzy sliding mode control in a novel reformuation of the model of induction motor without speed sensor. So, first a new linearized and decoupled model of the motor is elaborate followed by the application of an approach of sliding mode control destined to ensure robustness to the overall system proposed. Furthermore, the speed is estimated by using the adaptive method with model of reference (MRAS). This method consists in working out two models one of reference and the control adjustable one for the estimate of two components of stator flux starting from the measurement of the currents and stator tensions. The estimated speed is obtained by canceling the difference between stator flux of the model of reference and those of the adjustable model. Very satisfactory results of simulation are presented at the end of this article. Copyright © 2008 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Induction motor, Feed Back Linearization Control, Fuzzy Sliding Mode Control, Adaptive Method with model of Reference.
Vol. 1. n. 1, pp. 49-56
Abstract - Several field-oriented induction motor drive methods without speed sensors have been proposed. These methods have a disadvantage that the rotor resistance variation causes an estimation error of the motor speed. Therefore, simultaneous estimation of the motor speed and the rotor resistance is required. This paper deals with compensation of the rotor inverse time constant variation using direct field oriented induction motor control (DFOC) without speed sensor. The proposed method based on the model reference adaptive system (MRAS) theory and a direct rotor inverse time constant calculation method. The effectiveness of the proposed method was verified by digital simulation result. Copyright © 2008 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Speed sensorless, induction motor, MRAS, rotor inverse time constant estimator.
Vol. 1. n. 1, pp. 57-64
Abstract - This paper compares two observer structures suitable for high performance induction motor vector control. The first one is the Extended Kalman Filter (EKF) and the second one is the Extended Luenberger Observer (ELO), the both are controlled by a Fuzzy-PI. The comparison between these two observers is made in order to compare their performance to tracking and accuracy the actual rotor speed; Simulation results show the effectiveness of these proposed observers to monitor the drive. Copyright © 2008 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Extended Kalman Filter, Extended Luenberger Observer, Fuzzy-PI, Induction Machine Drive, IRFOC, Sensorless Control.
Vol. 1. n. 1, pp. 65-71
Abstract - The effect of constraints in generalized predictive control (G.P.C.) is implemented using a model of the motor in fixed stator reference frame (a-b). The variables to be controlled are the rotor speed and the rotor flux norm, required to implement the predictive control algorithm is estimated using Kalman Filter algorithm. The NGPC law minimizes a simple quadratic cost function of the predicted tracking error following the receding horizon strategy. Structure called GPC (Generalized Predictive Control) ensures rotor speed and rotor flux tracking despite uncertainties on rotor resistance and load torque variations. Simulations are carried out in order to show the effectiveness of the drive and the robustness to parameters variations. Copyright © 2008 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Generalized predictive control, Nonlinear Control, Induction Motors, field orientation, Kalman Filter.
Vol. 1. n. 1, pp. 72-80
Abstract - In variable structure sliding mode control schemes, one has to adjust the controller gains in order to obtain an acceptable response. The controller gains are required to be readjusted under variation of the disturbance load torque and/or of the parameters of the induction motor. To compensate automatically for the uncertainties experienced by the system, the controller gains are adjusted by a fuzzy inference mechanism. In this paper, an adaptive fuzzy sliding mode controller is proposed. It combines the merits of sliding mode control, fuzzy inference mechanism and the adaptive algorithm of robust control, fast dynamic response, minimum control effort and reduced chattering. First, a sliding mode controller is designed, and then a fuzzy inference mechanism is used to compensate for the uncertainties experienced by the system, by adjusting the reaching rates of the sliding mode controller. Finally an adaptation algorithm is used to adjust the centers of the fuzzy sets in order to reduce the control effort and chattering. Copyright © 2008 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Variable structure control, Fuzzy logic control, Induction motor drives, Adaptive control.
Vol. 1. n. 1, pp. 81-86
Abstract - Operator based nonlinear control design for a water level experimental process is presented in this paper. In details, a design method using operator based robust right coprime factorization for the real nonlinear process is considered, as a result, robust stability of the nonlinear control system is guaranteed. For the obtained robust stable process, an operator based process output tracking controller is designed to realize the desired output tracking performance. This paper applies the design method to the water level experimental process. Copyright © 2008 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Operator, Robust right co-prime factorization, Nonlinear output feedback control, Output tracking.
Vol. 1. n. 1, pp. 87-93
Abstract - In This paper a robust control and a simple concept of the sliding mode control using to control of the active and reactive power generated by a doubly-fed induction generator (DFIG) is presented. It provides robust regulation of the primary side active and reactive currents and it is suitable for both electric energy generation and drive applications. The mathematical model of the machine written in an appropriate d-q reference frame is established to investigate simulations. In order to control the power flowing between the stator of the DFIG and the power network, a decoupled control of active and reactive power is synthesized using sliding mode controllers. Their respective performances are in terms of stator currents references tracking. Copyright © 2008 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Active and Reactive Power, DFIG, Sliding Mode Strategy, Simple Concept, Robustness.
by T. Tafticht, K. Agbossou, A. Chériti, K. P. Adzakpa Vol. 1. n. 1, pp. 94-101
Abstract - This paper proposes the output power maximization control of wind energy systems with battery energy storage. A permanent magnet synchronous generator (PMSG) is used as a variable speed generator in the proposed wind energy system. In most of the peak power extraction methods for wind turbine generation systems described in the current literature, the wind energy systems are designed to be efficient in high wind speeds and have a cut-off wind speed which is the minimum threshold to obtain energy. In order to achieve the maximum power control of the wind turbine across a wide range of wind speeds, a dynamic behaviour of the wind system with battery energy storage including wind disturbances is theoretically analyzed in this paper. A buck-boost converter is designed to allow the wind generator output voltage to be controlled, while allowing a constant DC voltage to the load. Then, the proposed maximum power point tracking (MPPT) control method, where the information on wind velocity is not required, is used to analyze the maximum power point of the wind turbine. Copyright © 2008 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Wind turbine, Variable-Speed, PMSG, MPPT, Buck-boost converter, Energy transfer.
by K. Mhatli, M. Selmi, H. Rehaoulia, B. Ben Salah Vol. 1. n. 1, pp. 102-108
Abstract - The Switched Reluctance Motor (SRM) is characterized by a high nonlinear static torque. This feature is a limitation in the operation of the SRM in positioning applications. This paper presents an approach to overcome this drawback. The proposed approach predicts the rotor position considering the applied load torque and a given reference position. First, the nonlinear static torque characteristic of SRM is established by means of the Finite Element Method (FEM). Then two neural networks will be developed over the resulting data of the SRM using a back-propagation technique. In order to validate the proposed approach, a configuration based on these two networks, is designed. The simulation results showed the efficiency of suggested approach. Copyright © 2008 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Back-propagation neural network, finite element method, load torque, positioning, switched reluctance motor.
Vol. 1. n. 1, pp. 109-117
Abstract - The Rapidly Exploring Random Tree (RRT) algorithm is a probabilistic motion planning method. It builds a graph in the configuration space of a robot such that its motion equation is taken into account. The basic RRT algorithm is able to plan a path which avoids the collision with static obstacles. This paper discusses the required modifications if the environment of the robot contains moving obstacles as well. Two different methods are presented. The first one can only be used if the graph is a single tree. The main modification w.r.t. the original RRT algorithm is that the graph is built in an extended space and a special distance-like pseudo-metric is applied. The second algorithm may work with several trees as well and it is based on the time-scaling of the reference path. Copyright © 2008 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Mobile robots, moving obstacles, probabilistic motion planning, RRT, time-scaling.
Vol. 1. n. 1, pp. 118-124
Abstract - This paper describes the application of the backstepping based approach for the control of rotary drilling system, in order to arrive at a robust controller capable of dealing with the torsional oscillations (stick-slip), known to cause damages. Up to now, classical regulators have been implemented only. This work is motivated by the complex problem of the nonlinearity in drillstring, which is rotated at a constant angular velocity by an electric motor, but exhibits superimposed torsional vibrations caused by a non linear relationship between torque and angular velocity at the rock-crushing tool. The effectiveness of the designed controller has been tested on the rotary drilling system through numerical simulations in order to point out the level of the improvements that advanced control may bring. Copyright © 2008 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Backstepping, Robustness, Rotary Drilling System.
Vol. 1. n. 1, pp. 125-131
Abstract - Genetic Algorithms are one the most widely known evolutionary search algorithms. Their approach to optimization has proved very successful in a series of applications in science and engineering in the last decades. In this paper their application in the performance optimization of a cellular wideband code division multiple access network is explored. The problem objective is to maximize the total deliverable downlink bit rate by allocation of power and bit rate to individual users. Simulation results exhibit the advantages of the proposed technique comparing with the equal–rate allocation strategy as well with well–known dynamic programming algorithms. Interesting conclusions about the relation between the downlink throughput, the positions of the mobile units, the base station transmission power, and the deliverable bit rate to each user have been obtained. Based on the derived results a practical implementation of a rate allocation scheme for wireless wideband communication systems is finally proposed. Copyright © 2008 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Optimization, Genetic Algorithm, Dynamic Programming Method, Capacity, WCDMA.
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