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International Review of
Automatic Control
March 2013
(Vol. 6 N. 2)

    A Comparative Study of Identification Techniques for Fractional Models

    by Abdelhamid Jalloul, Khaled Jelassi, Jean-Claude Trigeassou

    Vol. 6. n. 2, pp. 89-96


    Abstract - A comparative study of methods for fractional system identification is presented in this paper. The fractional system is modeled by the help of a non integer integrator which is approximated by a J+1 dimensional modal system composed of an integrator and first order systems. This identification method is compared to other techniques available in the Matlab toolbox. The model parameters are estimated by an output-error technique using a non linear iterative optimization algorithm. Numerical simulations show the performance of the modal approach for modeling and identification.

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    Keywords: Fractional Systems, Fractional Integrator, Non Integer Identification, Output Error Identification.


    A Robust LMI-based Stabilizing Control Method for Bilateral Teleoperation Systems

    by A. Roushandel, A. Khosravi, A. Alfi

    Vol. 6. n. 2, pp. 97-106


    Abstract - This paper introduces a novel structure to design a robust PID controller based on a Linear Matrix Inequality (LMI) approach. The objectives of the controller establishment are to achieve complete transparency and robust stability despite the large time-delay of communication channels and uncertainty in various parts of a teleoperation system. In this structure two local controllers must be implemented by applying an LMI-based H theory. One of these controllers is responsible for tracking the master position in the remote site which is called slave controller. The slave controller is a novel robust PID controller which is implemented by employing an LMI-based H framework. Furthermore, the other one controller called master controller is in charge of force tracking as well as guaranteeing stability of the closed-loop system and it requires to be established by applying an LMI-based multiobjective H2/H method. Finding optimal values for the parameters of the controllers can be ensured by applying the convex optimization method in both sites. As it can be seen from the simulation results, the proposed control method is highly effective in providing a stable transparent teleoperation system under uncertain, but bounded, time-delay in communication channel and task environment. Since the simulation results illustrates time responses of the system for nominal values of the parameters, μ-analysis has been used to investigate stability of the overall system in spite of changes in the parameters of the master and/or slave manipulators in modified range.

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    Keywords: Teleoperation systems, Transparency, Multiobjective H2/H controller, Linear Matrix Inequality, Robust PID controller.


    Wireless Control of a DC Motor Using a Four Quadrant Chopper

    by Satish Kumar Gudey

    Vol. 6. n. 2, pp. 107-114


    Abstract - This paper is a live demonstration of the speed control of a D.C. Motor and direction, achieved using radio frequency technology. However, PWM technique remains the underlying principle for the speed control. This circuit works with a variable on-off ratio, the average on time may be varied from zero to hundredpercentage. In this manner, a variable amount of power can be transferred to the load. The main advantage of a PWM circuit over a resistive power controller is the efficiency. The radio frequency(RF) modules used here are STT-433 MHz Transmitter, STR-433 MHz Receiver, HT640 RF Encoder and HT648 RF Decoder. As already mentioned, the RF transfer is made at a carrier frequency of 433MHZ and the encoder, decoder pair are designed to handle data at the same frequency. The remote circuit consists of 8 switches – ON/OFF, Clockwise/Counter clockwise, zero to hundred percent speeds, in steps of twenty and it for the RF module to transfer this data to the control circuit.At the receiving end, the RF receiver receives this data, gives it to RF decoder. This decoder converts the single bit data into 8-bit data and presents it to the microcontroller (Atmel 89C51). Now, it is the job of the controller to read the data and perform the corresponding action i.e., to rotate the dc motor clockwise, anticlockwise, increase or decrease the speed of the dc motor. 16X2 LCD is connected at the receiver end to display the speed level of the motor and the direction. LED indication is also provided for visual indication. The technology remains the characteristics of high reliability .Hardware result verifies the simulation results.

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    Keywords: Decoder, Encoder, Pulse Width Modulation, Receiver, Transmitter.


    Modeling of Heat Exchangers: Optimization of Control

    by M. A. Arbaoui, F. Bagui, A. Zatni

    Vol. 6. n. 2, pp. 115-120


    Abstract - The work presented in this paper deals with of study the solutions of the equations governing heat transfer in tubular heat exchangers steady state, to determine a correlation between the input parameters of the process giving the same state stationary. The obtained results showed that, for a imposed set point on the output of the process, the flow rates of the two fluids hot and cold are related by a linear equation. An analysis of this relationship in transient regime allowed us to add elements related criterion to be minimized for implementation of optimal control.

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    Keywords: Modeling, Heat exchangers, Simulation, Engineering of control.


    Effects of Three Phase AC Voltage Controller on Performance Characteristic of Induction Motor

    by Mohamed A. Enany

    Vol. 6. n. 2, pp. 121-126


    Abstract - This paper describes a MATLAB/Simulink realization of the induction motor speed control method by controlling the voltage applied to the stator winding using the three phase AC voltage controller. An attractive approach of RL model of induction motor is proposed. The proposed simulation model is checked by experimental work. Torque-speed characteristics are obtained for different values of firing angle to demonstrate its effect on the stability region and the maximum torque value.

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    Keywords: Matlab/Simulink, Induction Motor, Three Phase AC Voltage Controller.


    Robust Interline Power Flow Controller Design for Damping of Low Frequency Oscillations in Power System with Wind Power Sources

    by T. Kerdphol, K. Hongesombut, Y. Weerakamaeng

    Vol. 6. n. 2, pp. 127-133


    Abstract - This article proposes the robust controller design of the interline power flow controller (IPFC) in the power system consisting of the single synchronous generator connected to the infinite bus based on the modified Heffron-Phillip’s model. The controller is used so as to control the frequency robustly and to improve the power system stability due to the uncertainty of power produced from the installed wind turbine in the power system. The power from the installed wind turbine is introduced into the system and treated as the uncertainty during the design process. The H loop-shaping design procedure (HLSDP) is adopted as the design procedure in this study. The results reveal that HLSDP can achieve higher performance and more robustness compared with lead-lag compensators of which the parameters tuned by the genetic algorithm.

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    Keywords: Power System Oscillations, Interline Power Flow Controller, HLSDP, Robust Control, Wind Energy.


    Robust Sliding Mode Control of Class of Linear Uncertain Saturated Systems

    by B. Torchani , A. Sellami , G. Garcia

    Vol. 6. n. 2, pp. 134-146


    Abstract - This paper proposes a new design approach of continuous sliding mode control of linear systems in presence of uncertainty and saturation. The saturation constraint is reported on inputs vector and uncertainty being norm bounded reported on both dynamic and control matrices. In a first step, the design of the sliding surface is formulated as a pole assignment of linear uncertain and saturated system in a specific region through convex optimization. The solution to this problem is therefore numerically tractable via linear matrix inequalities (LMI) optimization, which leads to the development of a continuous and non-linear control law. In a second step, an approximation on the trajectory deviation of the uncertain saturated system compared to the ideal behavior is proposed to provide robustness of the nonlinear control. Finally, the validity and the applicability of this approach are illustrated by a multivariable numerical example of a robot pick and place.

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    Keywords: Sliding Mode Control, Norm Bounded Uncertainty, Saturation, Robustness.


    A Conceptual Visualization of Industrial Control Systems: Electrical Power System

    by Sabah Al-Fedaghi, Faleh Faihan

    Vol. 6. n. 2, pp. 147-154


    Abstract - The latest progress in industrial control systems is to implement information technology solutions to support such features as administrative control based on network-based information connectivity. This paper focuses on an electrical power grid as a sample of such systems. A fundamental understanding of grid information hierarchy is essential to meet new challenges due to increasing needs of grid efficiency, flexibility, and control, and greater security risks and reliability challenges for large cyber-physical systems. Methods used in visualizing and representing electrical grids are an important tool for achieving comprehension and facilitating control (e.g., UML use cases). The problem is that current high-level representation grids are a heterogeneous mix of diagrams (e.g., UML use cases) flowcharts, graphs, technical drawings, and maps that do not furnish a base on which to discuss the characteristics, uses, behavior, interfaces, requirements, and standards of the grid. This paper proposes a solution in the form of a conceptual diagrammatic specification of grid architecture and applies it to the electric grid in the state of Kuwait. The approach is the skeleton of a method based on generic stages that make up any process and embraces input, processing, creation, and output. It provides a base that can be supplemented with extra notions from various current diagrammatic methods. The results indicate the viability of the proposed method as a foundation for zooming in and out on specifications of the grid in a uniform way.

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    Keywords: Industrial Control System, Electrical Power System, Visualization, Electric Grid, Conceptual Modeling.


    A New Ultrasonic Exponential Decay Pulser Technique for Low Concentrations Detection and Measurements

    by M. S. Salim, M. F. Abd Malek, Naseer Sabri, N. M. Noaman, K. M. Juni, N. A. Binti Abu Talib

    Vol. 6. n. 2, pp. 155-167


    Abstract - The objective of this study was to design and implement a new ultrasonic pulser with adjustable concentration detection. The new technique based on transmits a multiple ultrasound pulses with decay power through slurry to determine the lowest concentration that can provide an accurate attenuation measurement and wide measurement range. The ultrasonic pulser was designed to transmit a reliable pulsed-power decay set that can be reprogrammed with new output variables, e.g. ,the pulse amplitude, the pulse frequency, the set size, the decay power factor of the pulse amplitude, the transmit mode, and the time interval. Ultrasound attenuation measurements were obtain for kaolin-water slurries with1%, 10%, 20%, 30%, and 40% kaolin concentration by weight. Concentration attenuation measurements of less than 5% may prove useful for process control when detecting contaminants. A long measurement level is obtained from the pulsed-power transmission, regardless of the material used to construct the container. A signal in the receiver transducer provides the attenuation measurements, for each echo, a fast Fourier transform (FFT) of the appropriate signal was obtained and compared with the water signals to yield the attenuation (as a function of frequency). The data show the feasibility of measuring a kaolin concentration of less than 5 wt%. When using a commercial pulser with the same device setting, no detectable echo was observed. Therefore, new technique measurements may prove useful in detecting solid content in liquid. This study demonstrated that the proposed pulsed-power transmission technique is promising for evaluating low concentrations of solids in fluids and for measuring sedimentation in solid-liquid systems.

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    Keywords: Pulse-Power Decay System, Attenuation, Contaminates Detection, Process Control.


    Nonlinear Modeling and Estimation Techniques for a Fed-batch Prototype Bioprocess

    by Monica Roman

    Vol. 6. n. 2, pp. 168-176


    Abstract - This paper presents nonlinear modeling and estimation techniques dedicated to a fed-batch prototype bioprocess. More precisely, this prototype bioprocess is an aerobic microbial growth process coupled with an enzyme-catalyzed reaction, which is widely used in bioindustry. As a modeling procedure, the present work proposes an innovative methodology, namely the bond graph approach. In order to obtain a useful model for control purposes, it is necessary to derive estimation strategies for unmeasurable states and kinetic parameters. By using some model structural properties, an asymptotic state observer is derived. Also, the nonlinear and uncertain kinetic rates of this process are on-line estimated by using a high-gain observer. The performance and behavior of estimation techniques are analyzed via numerical simulations.

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    Keywords: Nonlinear Systems, Modeling, Bond Graphs, Estimation, Biotechnology.


    Support Vector Machine for MPPT Efficiency Improvement in Photovoltaic System

    by Ameer A. Kareim, , Muhamad Bin Mansor

    Vol. 6. n. 2, pp. 177-182


    Abstract - This paper is aimed at enhancing the effectiveness of maximum power point tracking (MPPT) controller for PV systems. The Support Vector Machine (SVM) is proposed to accomplish the MPPT controller. Furthermore, the proposed SVM technique has been validated with hypothetical, the perturbation and observation (P&O), and incremental conductance (IC) algorithms. We have also implemented MATLAB models for PV module, theoretical, SVM, P&O, and IC algorithms. The optimum voltage of the PV system has been predicted by the enhanced MPPT by employing the SVM method, for the purpose of extracting the maximum power point (MPP). The solar radiation and room temperature of the modeled PV module are the two types of inputs employed by the SVM technique, and ultimately the optimum voltage of the PV system is the output of the SVM model. The results of the validation have revealed that, the proposed SVM technique has minimized Root Mean Square Error (RMSE) and performs far better than P&O and IC methods. Thus, it has been proved that, the proposed SVM method is efficient enough as against the P&O and IC methods, and extracts high power from PV system.

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    Keywords: Photovoltaic System (PV), Maximum Power Point (MPP), Maximum Power Point Tracker (MPPT), Perturbation And Observation (P&O), Incremental Conductance (IC), Support Vector Machine (SVM).


    New Control Of a Doubly-Fed Induction Generator of a Variable Speed Wind Turbine with Ku Transformation

    by N. Hamdi, A. Bouzid

    Vol. 6. n. 2, pp. 183-188


    Abstract - In this paper we present the sliding mode control (SMC) for variable speed wind turbines (WT) based on Doubly-Fed Induction Generator (DFIG). A new optimal control method based on KU transformation to control the generator stator active and reactive power is proposed. This kind of system has already been considered in the past by other researchers, mainly by using Park transformation. The global controller is firstly tested with a simplified mathematical model of the aero turbine and DFIG. Secondly, the aero turbine controller is validated upon a flexible wind turbine simulator. The simulation was performed using Simulink of Matlab to show the effectiveness of the proposed control strategy.

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    Keywords: Doubly Fed Induction Generator (DFIG), Wind Turbine (WT), Sliding Mode Control (SMC), KU Transformation.


    Speed Sensorless of PMSM Control, Using Fuzzy Set and Gopinath Observer

    by K. Hachemi, M. Laouer, Y. Miloud

    Vol. 6. n. 2, pp. 189-193


    Abstract - This paper describes a new approach to the observer-based on sensor less control method using a minimum order state observer of Gopinath for the mechanical state estimation of the motor. The disturbance torque estimation for permanent magnet synchronous motors is included. We have constructed the linear reduced order observer for estimating rotor speed and disturbance torque based on non-linear model of the synchronous motor.

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    Keywords: Fuzzy Set, Vector Control, Permanent Magnet Motors, Gopinath Observer, Rotor Speed, Disturbance Torque.


    Robust Controller Design Using Edge Theorem and Genetic Algorithm

    by Mária Hypiusová, Slavomír Kajan

    Vol. 6. n. 2, pp. 194-200


    Abstract - This paper deals with the robust controller design using Edge Theorem and genetic algorithm for uncertain SISO systems. The controller is designed using the Edge Theorem and the Neymark D-partition method for the affine model, this approach guarantees the required degree of stability. The genetic algorithm is used for modification of Edge Theorem method. The genetic algorithm represents an optimisation procedure, where the cost function to be minimized comprises the closed-loop simulation of the controlled process and a selected performance index evaluation. Using this approach, the parameters of the PID controller were optimised in order to obtain the required behaviour of the controlled process. Practical implementation is illustrated by the robust controller design for a DC motor with various parameters.

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    Keywords: Edge Theorem, Genetic Algorithm, Robust Controller, Uncertain System.


    Blackstart of Combined Cycle Power Plants in Slovak Power System

    by J. Murgaš, M. Ernek

    Vol. 6. n. 2, pp. 201-205


    Abstract - Major blackouts of power systems in recent years show the importance of power system stability studies. One of the most discussed stability problems is island operation. Combined cycle power plants are one of the major supplies of Slovak power system nowadays. Their mainly purposes are power generation and household heating. Gas turbines are very well known for their fast response, so it is necessary to discuss their application in blackstart service and restoration process in island operation. One of the most important variables that has to be observed in the island operation is frequency, because power plants could operate safely only in region of 48 to 51.5 Hz. The aim of this paper is to provide a study of blackstart of combined cycle power plants in Slovak Power System and stability of an islanded power system. Simulation results are given. One of the most important results of this paper is to show the behaviour of combined cycle power plants on restoration process in island operation.

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    Keywords: Power System, Gas Turbines, Load, Frequency And Speed Control, Dynamic Turbine Models, CCGT, Control Of Islanded Power System, Blackstart.


    Neural-Genetic Control Algorithm of Nonlinear Systems

    by Slavomír Kajan, Zuzana Dideková, Štefan Kozák, Marek Linder

    Vol. 6. n. 2, pp. 206-210


    Abstract - Control of nonlinear systems is a challenging task. One of the ways of control of such systems is the use of neural networks as controllers. In this paper a methodology is proposed, where for neural controller design the genetic algorithm has been used. This method allows find optimal adjustment of neural network weights so that high performance is obtained. The proposed control method is realized in Matlab/Simulink and demonstrated on two examples of nonlinear dynamical systems.

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    Keywords: Genetic Algorithm, MLP Network, Neural Controller, Neural Network, Nonlinear Dynamic System Control.


    Procedure For Constructing Linear Functional Observers

    by Benoit Larroque, Farid Noureddine, Frederic Rotella

    Vol. 6. n. 2, pp. 211-220


    Abstract - In this paper a straightforward procedure, to obtain a linear functional observer with order equal to the dimension of the vector to be estimated, is proposed. Inspired by [3], we have developed a procedure to construct this type of observer in which some significant simplifications have been made and allow computational burden reduction. The procedure developed in this work has the originality and the great advantage that all required matrices are obtained without calculating any generalized inverse. A novel approach which constitutes the coupling of a coordinates transformation and the use of the {1}-inverse property requires only the inversion of a nonsingular matrix. A procedure where all steps are clearly identified is written and a numerical example is provided to illustrate the effectiveness of the observer.

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    Keywords: Linear Functional Observers, State Observers, Estimation.


    An Adaptive Motion Estimator Design for High Performances H.264/AVC Codec

    by Salah Dhahri, Abdelkrim Zitouni, Kholdoun Torki

    Vol. 6. n. 2, pp. 221-227


    Abstract - An evident trend in modern world is the digital convergence in the current electronic consumer products which have various functions like Video on Demand (VOD), Digital Multimedia Broadcasting (DMB), Global Positioning System (GPS), Portable Multimedia Player (PMP) and so on. Due to such demand, it is necessary to support the widely used video compression standards in a single system-on-chip (SoC) platform. In this paper, we present a cost-sharing and adaptive GFS (Gradient-Four Search) architecture that integrates the gradient and the four step search algorithms to support the slow and rapid H264AVC video sequences. The proposed architecture can be configured dynamically by the appropriate algorithm depending on the video nature (slow or rapid). It uses only one data path to reduce the hardware cost significantly and it is based on stoppable clock technique to reduce dissipated power. The shared architecture is synthesized in CMOS 0.35 nm technology. The results show that the proposed design satisfies the requirement of the two types of video sequences with a maximum PSNR video quality. The scheme is also suitable for low-cost implementation in modern multi-codec systems.

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    Keywords: H.264, Adaptive Motion Estimation, Four Step Search, Gradient Search, Low Power , Area reduction, Portable codec.