The volume 2001

Table of Contents

Radu-Emil PRECUP, Stefan PREITL: On A Takagi-Sugeno Fuzzy Controller With Non-Homogenous Dynamics
Abstract  Full Text

Daniela DANCIU, Vladimir RASVAN: Stability Criteria For Cellular Neural Networks
Abstract  Full Text

Radu DOBRESCU, Dana ANDONE, Matei DOBRESCU: Algorithms For Wireless Channel Equalization With Joint Coding And Soft Decision Feedback
Abstract  Full Text

Stelian JUDELE, Răzvan ŞOLEA and Viorel DUGAN: Limitations Of A Static VAr Compensator (SVC) With Switched Capacitor Operating As An Active Filter
Abstract  Full Text

C. Nichita, D.Luca, B. Dakyo, E. Ceanga, N.A. Cutululis: Modelling Non-Stationary Wind Speed For Renewablwe Energy Systems Control
Abstract  Full Text

Yiannis S. BOUTALIS, Adrian MOISE, B.G. MERTZIOS: Neural Network Schemes in Cartesian Space Control of Robot Manipulators
Abstract  Full Text

Cosmin IONETE, Emil PETRE, Dan SELISTEANU: Robust Control Methods for a Recycle Bioreactor
Abstract  Full Text

Dan SELISTEANU, Cosmin IONETE, Emil PETRE: On Exponential And Asymptotic Estimation Of State Variables In Bioprocesses
Abstract  Full Text

Virginia Ecaterina OLTEAN, Dorin CARSTOIU: Comments On Clock Models In Hybrid Automata And Hybrid Control Systems
Abstract  Full Text

Dorel Aiordachioaie: On Activity modelling in process modeling
Abstract  Full Text

Daniela Cristina CERNEGA and Viorel MÎNZU: Supervisory Control Technique For An Assembly Workstation As A Dynamic Discrete Event System
Abstract  Full Text

Sergiu CARAMAN, Laurentiu FRANGU, Maria TURTOI: Software System For Generating, Identification And Simulation Of The Biotechnological Processes Models
Abstract  Full Text

Maria TURTOI, Traian HOPULELE, Sergiu CARAMAN: Modeling of the biodegradation in multiphase stirred tank reactor
Abstract  Full Text

Ciprian-Daniel NEAGU, Daniela NEAGU, Lucian GEORGESCU, Vasile PALADE: Analysis Of A Neuro-Fuzzy Approach Of Air Pollution: Building A Case Study
Abstract  Full Text

Emilia PECHEANU, Diana STEFANESCU, Sabin Corneliu BURAGA
Adrian ISTRATE: Integrating Hypermedia Objects In An Intelligent Tutoring System
Abstract  Full Text

 

 

Radu-Emil PRECUP, Stefan PREITL: On A Takagi-Sugeno Fuzzy Controller With Non-Homogenous Dynamics
Abstract: The paper proposes a Takagi-Sugeno fuzzy controller with non-homogenous controller dynamics with respect to the two input channels, that means, in the linear case, different transfer functions with respect to the reference input and to the controlled output. The considered controller is dedicated to a class of third-order integral-type plants, specific to the field of electrical drives, which can be characterised in their simplified linearised forms by standard models. For these models even conventional linear control structures give satisfaction. There is proposed a development method for the fuzzy controller, based on the fact that fuzzy controllers can be, in some certain conditions, well approximated by linear controllers and, so, the Extended Symmetrical Optimum (ESO) method and the Modified Structure of ESO Method are applicable in this situation. The fuzzy controller and its corresponding development method are validated by an application example that can correspond to the speed control of an electrical drive.

Keywords: phase margin, Extended Symmetrical Optimum method, Modified Structure of Extended Symmetrical Optimum method, Takagi-Sugeno fuzzy controller, non-homogenous dynamics.

 



Daniela DANCIU, Vladimir RASVAN: Stability Criteria For Cellular Neural Networks

Abstract: A cellular neural network is an artificial neural network which features a multi-dimensional array of neurons and local interconnections among the cells. Neural networks are systems with several equilibrium states. It is exactly this fact (existence of several equilibria) that grants to the neural networks their computational and problem solving capabilities. The paper is concerned with dynamical properties of the model of a cellular neural network as a dynamical system with several equilibria displaying interaction delays. There are given sufficient conditions for stability of the cellular neural networks.

Keywords: Cellular neural networks, global stability, time delay.

 



Radu DOBRESCU, Dana ANDONE, Matei DOBRESCU: Algorithms For Wireless Channel Equalization With Joint Coding And Soft Decision Feedback

Abstract: The paper proposes a new approach based on Joint Entropy Maximisation (JEM) using a soft decision feedback equalizer (S-DE) to suppress error propagation. In its first section, the paper presents the principle of the solution and the theoretical framework based on entropy maximisation, which allows introducing the soft decision device without assuming that the channel distortion is Gaussian. Because JE is a non-linear function, a gradient descent algorithm is used for maximising. Then an equivalence of JEM and ISIC (Inter-Symbol Interference Cancellation) is proved in order to establish that an equalised single carrier system using coded modulation (8-phase shift keying associated with a convolution code) offers similar performances when compared with multicarrier modulation. In the second section the paper develop an adequate receiver model for joint convolution coding and S-DFE. The error correction decoder uses a standard Viterbi algorithm. The DFE consists of a feedforward finite impulse response (FIR) filter (FFF) and a feedback filter (FBF) implemented as a transversal FIR filter. FFF eliminates the precursor ISI, while FBF minimise the effect of residual ISI using soft decisions by the joint coding and equalisation process. The third main section of the paper describes the proposed method for estimating optimum soft feedback using a maximum a posteriori probability (MAP) algorithm. Then, performances of the soft decision device in a simulated environment are analysed on a structure with 8 taps for FFF and 5 taps for FBF. Since the purpose of the evaluation was to compare the proposed S-DFE with a former H-EFE, the coded packet error rate was estimated in a two-path and in a six- path channel. We have shown that in some case the proposed algorithm offers better convergence rate and robustness when compared with the corresponding existing algorithm. Some conclusions on the extension of the S-DFE techniques in vary applications are finally presented.

Keywords: joint entropy, adaptive equalization, coded modulation, error correcting codes, communication channels.


 



Stelian JUDELE, Răzvan ŞOLEA and Viorel DUGAN: Limitations Of A Static VAr Compensator (SVC) With Switched Capacitor Operating As An Active Filter


Abstract: The goal of this paper is to analyze the limitations of a static VAr compensator (SVC) with switched capacitor, when this operate as an active filter.
The limitations considered and studied by simulation are in the zone of ability/inability of the active filter to produce current waveforms and waveforms with the desired di/dt of the desired line current, and from the zone of the operating constraints. The active filter limitations at the desired harmonic frequency hf were quantified with the help of two measures: percentage magnitude error and phase error, in the both capacitive and inductive operation modes.

Keywords: Static converter with switched capacitor, Modeling and simulation, Constraints and limitations in active filter operation mode.


 


C. Nichita, D.Luca, B. Dakyo, E. Ceanga, N.A. Cutululis: Modelling Non-Stationary Wind Speed For Renewablwe Energy Systems Control

Abstract: This paper deals with the modelling of the wind speed, treated as a non-stationary process. In the proposed modelling methods, the wind speed has two components: a long and medium term-component, described by an available spectral characteristic in the low frequency range, and a non-stationary turbulence component, which is “attached” to the medium and long-term component. Two procedures for turbulence component generation, using some shaping filters, are proposed. In both methods turbulence component proprieties are determined depending on current mean value of the medium and long-term component. Numerical results and comment concerning the implementation aspects are also presented

Keywords:. wind speed, turbulence, power spectral density, numerical simulation, non-stationary signals, shaping filters.

 


Yiannis S. BOUTALIS, Adrian MOISE, B.G. MERTZIOS: Neural Network Schemes in Cartesian Space Control of Robot Manipulators

Abstract: In this paper we are studying the Cartesian space robot manipulator control problem by using Neural Networks (NN). Although NN compensation for model uncertainties has been traditionally carried out by modifying the joint torque/force of the robot, it is also possible to achieve the same objective by using the NN to modify other quantities of the controller. We present and evaluate four different NN controller designs to achieve disturbance rejection for an uncertain system. The design perspectives are dependent on the compensated position by NN. There are four quantities that can be compensated: torque , force F, control input U and the input trajectory Xd. By defining a unified training signal all NN control schemes have the same goal of minimizing the same objective functions. We compare the four schemes in respect to their control performance and the efficiency of the NN designs, which is demonstrated via simulations.

Keywords: Manipulation Robot, Neural Network, Cartesian Space Control, Jacobian.

 


Cosmin IONETE, Emil PETRE, Dan SELISTEANU: Robust Control Methods for a Recycle Bioreactor

Abstract: The paper presents a robust control design strategy for bioprocesses, which are characterized by strongly nonlinear dynamics. More precisely, we present the H2 methodology in order to compute the controller for a recycle Continuous Stirred Tank Bioreactor (CSTB). We consider a general method of formulating control problem, which makes use of linear fractional transformation as introduced by Doyle (1978). The formulation makes use of the general two-port configuration of the generalized plant with a generalized controller. The H2 norm is the quadratic criterion used in optimal control as LQG. The overall control objective is to minimize the H2 norm of the transfer matrix function from the weighted exogenous inputs to the weighted controlled outputs. The advantage of H2 control technique, which uses the linearized model of the CSTB, is that it is completely automated and very flexible. Finally, we prove that the closed loop control structure has very good inner robustness.

Keywords: Biotechnology, Nonlinear Systems, Linear Fractional Transform, H2 controller.

 


Dan SELISTEANU, Cosmin IONETE, Emil PETRE: On Exponential And Asymptotic Estimation Of State Variables In Bioprocesses
Abstract: The paper presents on-line estimation strategies for bioprocesses, which are characterized by strongly nonlinear dynamics. A general form for the state observers is analysed and the exponential observability of bioprocesses is discussed. For those biotechnological processes that possess the property of exponential observability, an extended Luenberger observer is implemented. If exponential observers cannot be used, a solution is the design of asymptotic observers. The proposed observers are implemented for a microbial growth process coupled with an enzyme-catalysed reaction, which is a usual bioprocess that takes place in a fed-batch bioreactor. Illustrative computer simulations and conclusions are included.

Keywords: Biotechnology, Nonlinear Systems, Exponential Observability, Asymptotic Observers
 


Virginia Ecaterina OLTEAN, Dorin CARSTOIU: Comments On Clock Models In Hybrid Automata And Hybrid Control Systems

Abstract: Hybrid systems have received a lot of attention in the past decade and a number of different models have been proposed in order to establish mathematical framework that is able to handle both continuous and discrete aspects. This contribution is focused on two models: hybrid automata and hybrid control systems with continuous-discrete interface and the importance of clock models is emphasized. Simple and relevant examples, some taken from the literature, accompany the presentation.

Keywords: hybrid systems, hybrid automaton, discrete event system (DES)

 


Dorel Aiordachioaie: On Activity modelling in process modeling
Abstracts: The paper is looking to the dynamic feature of the meta-models of the process modelling process, the time. Some principles are considered and discussed as main dimensions of any modelling activity: the compatibility of the substances, the equipresence of phenomena and the solvability of the model. The activity models are considered and represented at meta-level.

Keywords: Activity modelling, meta-modelling, concurrent engineering, methodology engineering, tools, computer based process modelling, simulation.

 


Daniela Cristina CERNEGA and Viorel MÎNZU: Supervisory Control Technique For An Assembly Workstation As A Dynamic Discrete Event System

Abstract. This paper proposes a control problem statement in the framework of supervisory control technique for the assembly workstations. A desired behaviour of an assembly workstation is analysed. The behaviour of such a workstation is cyclic and some linguistic properties are established. In this paper, it is proposed an algorithm for the computation of the supremal controllable language of the closed system desired language. Copyright © 2001 IFAC.

Keywords: discrete event dynamic systems, assembly systems, supervisory control

 


Sergiu CARAMAN, Laurentiu FRANGU, Maria TURTOI: Software System For Generating, Identification And Simulation Of The Biotechnological Processes Models

Abstract: The paper deals with the development of a software system (BIOCALC) for the modelling, identification and simulation of the biotechnological processes. BIOCALC is based on the algorithm developed by George Bastin and Daniel Dochain in (Bastin, et al., 1990), starting with the reaction scheme of the process. The BIOCALC software generates the differential equations of the process, identifies the model coefficients and allows the model simulation comparing the results to the experimental data.

Keywords: biotechnology, reaction scheme, model identification, numerical simulation


 


Maria TURTOI, Traian HOPULELE, Sergiu CARAMAN: Modeling of the biodegradation in multiphase stirred tank reactor

Abstract: The surface response methodology is used to verify predicted models and to adapt them on particular conditions of growth. The effect of solvent addition during the linear cell growth on the enhancement of biodegradation is presented and used to study the enhancement of mass transfer.

Keywords: biotechnology, bioreactor design, mass transfer, surface response methodology.
 


Ciprian-Daniel NEAGU, Daniela NEAGU, Lucian GEORGESCU, Vasile PALADE: Analysis Of A Neuro-Fuzzy Approach Of Air Pollution: Building A Case Study


Abstract: This work illustrates the necessity of an Artificial Intelligence (AI)-based approach of air quality in urban and industrial areas. Some related results of Artificial Neural Networks (ANNs) and Fuzzy Logic (FL) for environmental data are considered: ANNs are proposed to the problem of short-term predicting of air pollutant concentrations in urban/industrial areas, with a special focus in the south-eastern Romania. The problems of designing a database about air quality in an urban/industrial area are discussed. First results confirm ANNs as an improvement of classical models and show the utility of ANNs in a well built air monitoring center.

Keywords: artificial neural networks, fuzzy logic, air quality prediction.
 



Emilia PECHEANU, Diana STEFANESCU, Sabin Corneliu BURAGA
Adrian ISTRATE: Integrating Hypermedia Objects In An Intelligent Tutoring System

Abstract: The paper describes the internal architecture of an Intelligent Tutoring System, CS-Tutor. The architectural design of the tutorial system was developed in a collaborative work at the Department of Computer Science of the University of Galati and the Department of Applied Informatics of the Faculty of Computer Science of Iasi. Intelligent Tutoring Systems (ITS) are software packages which use the Artificial Intelligence techniques to aid in learning of some subject or skill. In recent years, Hypermedia has been gained the interest of many researchers working in the teaching field of study. The CS-Tutor internal architecture is based upon integrating Hypermedia Objects in an Intelligent Knowledge-Based frame.

Keywords: Pedagogical Model, Hypermedia Object, Pedagogical Unit.

 

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