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International Review of Automatic Control (Theory and Applications) - November 2010 (Vol. 3 N. 6) - Papers

Analytic Prognostic Model for a Dynamic System
Modeling Issues and Structural Properties of a Class of Nonlinear Bioprocesses
A Finite Time Convergent Chattering Free Second Order Sliding Mode Observer for non Stationary Systems
Robust Fault Detection in Uncertain Hybrid Systems, a PI Observer Approach
Identification of Hybrid Switching Systems with Unknown Number of Models and Unknown Orders
A New Neural Adaptive Control Based on Neural Emulation of Complex Square MIMO Systems
Induction Motor Robust Control: A Quantitative Feedback Theory Approach
Photovoltaic Array, Fuel Cell and Electrolyzer Connection to Grid by Direct Non-Linear Controlled H-Bridge Multilevel Inverter
Decreasing Ferroresonance Oscillation in Potential Transformers Including Nonlinear Core Losses by Connecting Metal Oxide Surge Arrester in Parallel to the Transformer
ANN’s Sensorless Induction Motor Fuzzy Logic Speed Control
Implementation of Five Level Inverter Based UPFC System Using PIC Microcontroller
Design of a Robust Multivariable Controller for an AC-VSC- HVDC System
Self-Tuning Position Tracking Control of an Electro-hydraulic Servo System in the Presence of Internal Leakage and Friction
Nonlinear Damping Control Schemes Using the Unified Power Flow Controller and Fuzzy Theory
Design and Simulation of Nonlinear Power Controllers for Variable-Speed Wind Energy Conversion Systems
Parameter Identification and Synchronization of a Rotational Mechanical System with a Centrifugal Governor
An Enabling Vision-Based Approach for non-Calibrated Robot-Positioning Task
An Intelligent Speed Controller for Space Vector Modulated Induction Motor Drive

International Review of Automatic Control - Papers

  Analytic Prognostic Model for a Dynamic System
         by Abdo Abou Jaoude, Khaled El-Tawil, Seifedine Kadry, Hassan Noura, Mustapha Ouladsine
          Vol. 3. n. 6, pp. 568-577

Abstract - To ensure high availability of industrial systems, recent developments in system design technology like in aerospace, defense, petro-chemistry and automobiles, are represented earlier in literature by simulated models during the conception step. These developments have facilitated the integration of diagnostic-prognostic models in these industrial systems. The monitoring of degradation indicators is used indirectly in failure prognostic. It is just a measurment of an unwanted situation. Hence, the diagnostic is not only a failure detection procedure but it also indicates the actual state and the historic of the system. The subsequent prognostic model leads to a predictive maintenance. The Remaining Useful Life is estimated from a predefined threshold of degradation. We will present here a procedure to create a failure prognostic model based on a physical dynamic system. But instead of degradation abaci largely used in prognostic studies, we will adopt here analytic laws of degradation such as Paris’ law for fatigue degradation and Miner’s law for cumulative damage.

Keywords: Analytic Laws, Degradation, Diagnostic, Fatigue, Miner’s Law, Paris’ Law, Prognostic.

Modeling Issues and Structural Properties of a Class of Nonlinear Bioprocesses
by Monica Roman, Dan Selişteanu

Vol. 3. n. 6, pp. 578-587

Abstract - In this work, the analysis of a nonlinear dynamical model of a class of bioprocesses is carried out. First, some structural properties are widely discussed, such as the partition of the model in a linear part and a nonlinear term, the decoupling of the kinetics, the positivity of the model. By using the structural properties, an asymptotic observer is derived, in order to estimate the unavailable states of the bioprocess. Second, the singular perturbations method and quasi-steady state assumption are used to obtain reduced order models, practical for control design. The obtained results are tested by using a complex anaerobic bioprocess, utilized for wastewater treatment, which takes place into a Continuous Stirred Tank Bioreactor.

Keywords: Asymptotic Observers, Biotechnology, Nonlinear Systems, Reduced-Order Techniques.

A Finite Time Convergent Chattering Free Second Order Sliding Mode Observer for non Stationary Systems

by Mohamed Mihoub, Ahmed S. Nouri, Ridha Ben Abdennour

Vol. 3. n. 6, pp. 588-593

Abstract - In this work, a second order discrete sliding mode observer (2-DSMO) is proposed. The dilemma chattering-precision, that characterizes the first order sliding mode observer in case of relatively large parameter variations and /or external disturbances, is analyzed and illustrated via a simulation example. The proposed 2-DSMO is then introduced. The stability of the closed loop control system based on the proposed observer is analyzed. A simulation example of the 2-DSMO state estimation for a second order discrete sliding mode control (2-DSMC) of a non stationary system is given.

Keywords: State Estimation, Discrete Time Control, Second Order Sliding Mode, Chattering Reduction, Stability Analysis, LTV Systems.

Robust Fault Detection in Uncertain Hybrid Systems, a PI Observer Approach
by Ezzeddine Khadri, Moncef Tagina

Vol. 3. n. 6, pp. 594-603

Abstract - The requirement of quality and productivity led to an increase in the complexity of the technological processes, generally, being able to be modeled as hybrid dynamical systems, which poses a problem of reliability. If automation is currently well controlled, the problem of monitoring and diagnosis of the hybrid systems remains posed. In particular, in the presence of model uncertainties and disturbances. The goal is thus to work out robust faults detection procedures to the top of the layer of control in order to guarantee the objectives of safety, reliability and availability. This work lies within this general scope; it is interested particularly in faults detection in the uncertain hybrid dynamical systems. The method suggested is based on the states estimation of the system comprising model uncertainties and disturbances. In such a situation, the use of a traditional observer with proportional gain is not effective. To solve this problem, a proportional integral observer allows a robust state estimation of the system and a generation of robust faults indicator residues.

Keywords: Hybrid Systems; Uncertainty; Robustness; Fault Detection; PI Observer.

Identification of Hybrid Switching Systems with Unknown Number of Models and Unknown Orders
by K. Halbaoui, D. Boukhetala, F. Boudjema

Vol. 3. n. 6, pp. 604-611

Abstract - Switching systems are a particular class of hybrid systems. They are described by several operating regimes, called modes, each of them being active under certain particular conditions. When the parametric models of subsystems are perfectly known, it is easy to handle such systems because the knowledge of the active regime at any moment is available. On the other hand, in the case where there is no information about the switching mechanism, the situation is more complicated. In this configuration, it is difficult to carry out a fault diagnosis scheme or to synthesize a control law. The principal motivation of this article is the development of a formal expression for parameters estimation using an algebraic approach. This approach is dedicated to a general class of hybrid switching systems. The formal expressions of the unknown parameters are obtained in function of integrals taken for inputs and outputs. With this intention, we apply the following mathematical tools: Laplace transformation, Leibniz formula and tools resulting from operational calculus. We illustrate our approach through simulation results in the presence of noise with data.

Keywords: hybrid systems, parametric models, switched systems, system identification.

A New Neural Adaptive Control Based on Neural Emulation of Complex Square MIMO Systems
by A. Atig, F. Druaux, D. Lefebvre, K. Abderrahim, R. Ben Abdennour

Vol. 3. n. 6, pp. 612-623

Abstract - This paper deals with a new indirect adaptive control scheme with decoupled adaptive rates, developed for complex square systems with unknown dynamics. This scheme, based on fully connected neural networks, is inspired from the real time recurrent learning (RTRL) algorithm. Both neural emulator and neural controller networks do not learn the plant dynamics but only adapt their parameters using an online adaptation algorithm in order to track the process variations. The contributions of this paper are to propose a new structure of neural control with a full structure of neural controller and to demonstrate the efficiency of the relaxation of networks parameters relative to the new proposed structure. Advantages of Neural controller with full structure and relaxation of its parameters from neural emulator ones are suggested according to simulation of nonlinear system. Effectiveness of the new proposed control structure is established by its application to the well-known Tennessee Eastman Challenge Process.

Keywords: Adaptive control, Emulator, Fully connected recurrent neural networks, Parameters relaxation, RTRL algorithm.

Induction Motor Robust Control: a Quantitative Feedback Theory Approach
by Faraz Dara, Asghar Akbari Foroud

Vol. 3. n. 6, pp. 624-632

Abstract - This paper synthesizes and develops a robust controller which is capable of dealing with internal and external disturbances within specific boundaries. In order to design the controllers a simplified equivalent model of induction machines, which is derived based on decoupling of flux and speed, is used. Quantitative Feedback Theory (QFT) is used to design controller for both system’s outputs- speed and flux. Simulation results are presented to illustrate that the proposed control scheme guarantees highly robust reference tracking when exposed to internal and external disturbances.

Keywords: Induction Motor, Robust Control, Quantitative Feedback Theory.

Photovoltaic Array, Fuel Cell and Electrolyzer Connection to Grid by Direct Non-Linear Controlled H-Bridge Multilevel Inverter
by M. Nazari, M. Abedi, G. B. Gharehpetian, H. Toodeji

Vol. 3. n. 6, pp. 633-640

Abstract - This paper presents a nonlinear controller, which is based on feedback linearization method for cascaded H-bridge multilevel inverters, to connect Photovoltaic (PV) arrays, Fuel Cells (FC) and electrolyzers to the AC grid. The multilevel inverters produce less voltage harmonics and operate in higher voltage levels such that the size of the output filter can be reduced and step-up transformer can be omitted. In the proposed Multiple Input Multiple Output (MIMO) control method, DC voltages and q-axis current are controlled and the capacitor voltage is directly regulated. The result is the possibility of controlling all DC voltages of the multilevel inverter, independently. This capability of controller permits elimination of DC-DC converters, usually used for Maximum Power Point Tracking (MPPT). Also, controllability of q-axis current results in the ability of the reactive power control.

Keywords: Direct Non-Linear Control, Electrolyzer, Fuel Cell, Multilevel Inverter, Photovoltaic.

Decreasing Ferroresonance Oscillation in Potential Transformers Including Nonlinear Core Losses by Connecting Metal Oxide Surge Arrester in Parallel to the Transformer
by Hamid Radmanesh, Mehrdad Rostami

Vol. 3. n. 6, pp. 641-650

Abstract - This paper studies the effect of MOV surge arrester on chaotic ferroresonance over voltages in potential transformer (PT) including nonlinear core losses effect. It is expected that MOV generally can cause ferroresonance ‘dropout'. Time-domain study has been carried out to study this effect. Simulation has been done on a potential transformer rated 100VA, 275 kV. The magnetization characteristic of the transformer is modeled by a single-value two-term polynomial with order seven. The core loss is modeled by nonlinear resistance. Simulation results reveal that connecting the MOV in parallel with the potential transformer, exhibits a great controlling effect on ferroresonance over voltages. Phase plane, voltage waveforms, along with bifurcation diagrams are also derived. Significant effect on the onset of chaos, the range of parameter values that may lead to chaos along with ferroresonance over voltages has been obtained and presented.

Keywords: Ferroresonance Oscillation, Stabilizing, Chaos Control, Potential Transformer, Nonlinear Core Losses, MOV Surge Arrester.

ANN’s Sensorless Induction Motor Fuzzy Logic Speed Control
by Ben Hamed. Mouna, Sbita. Lassaâd

Vol. 3. n. 6, pp. 651-657

Abstract - In this paper, an improved speed estimation method of an induction motor (IM) drives using artificial neural networks (ANN) combined with a fuzzy logic controller (FLC) is presented. The ANN speed estimator is trained off line using the error back propagation algorithm and the used data base is restricted to the positive speed values, reducing the memory capacity and the complexity of the ANN speed estimator. Based on the stator currents equations, the ANN speed estimator measured inputs are limited to only one stator current sensor. An implemented function for rotor speed direction detection is associated to the designed ANN speed estimator to extend the validity of the later one covering the entire speed range from positive to negative values. Experimental results for a 1kw IM are presented and analyzed, using dSpace system with DS1104 controller board, to show the validity and usefulness of the proposed observation algorithm and fuzzy logic controller.

Keywords: Induction Motor, Speed Sensorless, ANN, Speed Estimation, Scalar Control and FLC.

Implementation of Five Level Inverter Based UPFC System Using PIC Microcontroller
by S. Muthukrishnan, A. Nirmalkumar

Vol. 3. n. 6, pp. 658-662

Abstract - This paper deals with digital simulation and implementation five level inverter based UPFC system to improve the power quality. The UPFC is capable of improving transient stability in a power system. It is the most complex power electronic system for controlling the power flow in an electrical power system. The real and reactive powers can be easily controlled in a power system with a UPFC. The circuit model is developed for UPFC using rectifier and inverter circuits. The control angle of the converters is varied to vary the real and reactive powers at the receiving end. The Matlab simulation results are presented to validate the model. The hardware is tested and the experimental results are furnished.

Keywords: UPFC, Power Quality, Statcom, Compensation and Matlab Simulink.

Design of a Robust Multivariable Controller for an AC-VSC- HVDC System
by R. K. Mallick, P. K. Dash

Vol. 3. n. 6, pp. 663-672

Abstract - In this paper a voltage source converter based high voltage direct current (VSC-HVDC) transmission link is considered for the development of a multivariable robust controller to stabilize the AC-VSC-HVDC power system. To maintain the dc voltage and control the active and reactive power at the converter and inverter stations simultaneously a robust H_∞ control design methodology is adopted here. For designing the controller output feedback quantities like the converter side dc voltage and reactive power and the inverter side active and reactive power are obtained and used to satisfy an and H_∞ norm of the closed loop transfer function matrix. The proposed controller is evaluated for different power system operating conditions like the three-phase short-circuits on the converter and inverter buses, short-circuit on the dc line, loading changes, etc. and its performance show better results than the earlier used PI controllers in respect of the reduction of overshoots, faster settling times, and improved damping for the electromechanical oscillations of the generators.

Keywords: VSC-HVDC System, Output Feedback, H_∞ Controller.

Self-Tuning Position Tracking Control of an Electro-hydraulic Servo System in the Presence of Internal Leakage and Friction
by Mohd F. Rahmat, Zulfatman, Abdul R. Husain, Kashif Ishaque, Mukhtar Irhouma

Vol. 3. n. 6, pp. 673-683

Abstract - Friction and the internal leakage significantly deteriorates the performance of an electro-hydraulic servo system. Hence, an adaptive scheme could be better choice to handle these effects. Therefore, in this paper a Self-tuning fuzzy PID (SFPID) control scheme is employed for the position tracking performance of an electro-hydraulic servo system. A mathematical model of the system was designed with the consideration of internal leakage and friction inside the system. The internal leakage flow was implemented by introducing several levels and the friction was modeled using LuGre model. The self tuning capability of PID controller was achieved through fuzzy logic theory and the PID controller parameters namely, Kp, Ki and Kd were tuned by selecting appropriate fuzzy rules. The capability of the proposed controller was examined through simulation works in Matlab Simulink and validation was carried out in the real system. The results indicate that the proposed controller successfully improves the positioning performance of the system. The proposed controller can be applied potentially to control the modern equipments positioning applications.

Keywords: Hydraulic servo, position tracking, self-tuning fuzzy PID, leakage, friction.

Nonlinear Damping Control Schemes Using the Unified Power Flow Controller and Fuzzy Theory
by Tsao-Tsung Ma

Vol. 3. n. 6, pp. 684-691

Abstract - This paper presents a novel UPFC damping control scheme using fuzzy controllers working on local signals. The principle of damping control is based on the time-domain analysis of power system transient energy function (TEF) and implemented by using fuzzy controllers to eliminate low frequency electromechanical power oscillations. Mathematical models of the UPFC and TEF are firstly addressed followed by the detailed design procedure of a fuzzy based damping control scheme. Comprehensive computer simulations are then carried out to verify the feasibility of the proposed control scheme. The control effectiveness of using a combination of different control modes in the UPFC system with respect to different local input signals to improve the transient performance of power systems is investigated and discussed in full. The simulation results on the IEEE 9-bus test system reconfirm that the proposed damping control scheme is practically implementable and the UPFC is the most powerful FACTS device which is able to provide flexible control functions required for the real-time power flow regulation and fast transient control of power systems.

Keywords: Flexible Ac Transmission System, Power Flow Control, Unified Power Flow Controller, Transient Energy Function.

Design and Simulation of Nonlinear Power Controllers for Variable-Speed Wind Energy Conversion Systems
by M. Rajabzadeh, H. Khomami, M. Alizadeh Bidgoli

Vol. 3. n. 6, pp. 692-701

Abstract - This paper focuses on the problem of controlling power generation in variable-speed wind energy conversion systems (VS-WECS) which is the second-order model of wind power system. In order to get the maximum power from the wind, the variable-speed wind turbine should run at different speed when wind speed changes. Three types of nonlinear controllers, such as sliding mode control strategy, Backstepping control strategy and feedback linearization control, are proposed to ensure stability in operation regions and to impose the ideal feedback control solution despite of model uncertainties. The three proposed control approaches have been simulated on a 1.5-MW three-blade wind turbine to evaluate its consistency and performance. Simulation results demonstrate that the presented controlling methods can effectively achieve constant power control of variable speed wind power system under large-scale changing of wind speed. The results are comparable and explain the difference of the control strategies.

Keywords: Wind power system, Sliding mode control, Feedback linearization, Backstepping, Nonlinear control.

Parameter Identification and Synchronization of a Rotational Mechanical System with a Centrifugal Governor
by E. G. Razmjou, A. Ranjbar, M. Hosseini

Vol. 3. n. 6, pp. 702-709

Abstract - In this paper, synchronization together with parameter identification of two identical centrifugal governor chaotic systems is proposed where initial conditions of the master and slave systems are different. Parameters of the master system are also assumed unknown, which are identified using Lyapunov and adaptive control methods. In this paper a two-step controller is designed whereas it causes simpler structure and less control signal magnitude. Synchronization error between master and slave are shown in the simulations. Simulation results signifies the efficiency of the proposed method during synchronization and parameter identification of the centrifugal governor chaotic system.

Keywords: Centrifugal Governor, Synchronization, Parameter Identification, Lyapunov Stability, Adaptive Control.

   An Enabling Vision-Based Approach for non-Calibrated, Robot-Positioning Task
         by Luis A. Raygoza-Pérez, Emilio J. González-Galván, Ambrocio Loredo-Flores, Jorge J. Pastor, Eric T. Baumgartner
           Vol. 3. n. 6, pp. 710-722

Abstract - The application of calibration-free methods in robot positioning and path-tracking tasks involves aspects like the use of a camera model required to establish a non-linear, algebraic relationship between camera and robot-joint spaces. Among other advantages, the orthographic camera-model allows for robust model parameter estimation. With the purpose of compensating for the reduced accuracy of this model, several measures are applied including those designed to correct camera-space samples so they become more compatible with an orthographic projection. The corrections to the samples are based on the geometric representation provided by the perspective projection. The application of both the orthographic model and the subsequent measures for accuracy improvement increases the dificulty for developing robot and path-tracking tasks. In this paper, a calibration-free approach involving the use of a relationship between camera and robot joint spaces, based on a perspective projection, is proposed. Such a relationship simplifies the execution of precise robot-positioning maneuvers as no further accuracy-improvement measures are required. The presented methodology also provides a robust way for determining model-parameters, suitable for non-calibrated tasks. Experimental results have shown convergence of the nonlinear estimation procedure involved in the calculation of the proposed camera parameters yielding high accuracy when tested in a large number of robot-positioning maneuvers, using an industrial robot manipulator.

Keywords: Parameter Estimation, Calibration-Free, Vision-Based Robot Control.

   An Intelligent Speed Controller for Space Vector Modulated Induction Motor Drive
         by R. Arulmozhiyal, K. Baskaran
           Vol. 3. n. 6, pp. 723-733

Abstract - This paper presents design and implementation of voltage source Inverter type SVPWM based speed control of Induction motor using Fuzzy PI Controller. This scheme enables us able to adjust the speed of the motor by controlling the frequency and amplitude of the stator voltage; the ratio of stator voltage to frequency should be kept constant. The model of fuzzy control system is implemented in Real time Xilinx FPGA XC3S 400E and dsPIC 30F4011 controller and also introduced to control a speed to be constant when the load varies.

Keywords: Space Vector Pulse Width Modulation (SVPWM), Fuzzy PI Controller, Field Programmable Gate Array (FPGA), Digital Signal Peripheral Interface Controller (Dspic), Induction Motor Drive.