2017-09-20T10:20:31Z
http://ijste.shirazu.ac.ir/?_action=export&rf=summon&issue=252
Iranian Journal of Science and Technology Transactions of Electrical Engineering
2228-6179
2228-6179
2003
27
4
A proposed fuzzy RDBMS and its test results on an osteoporosis patient database
The new trend in database design is to store both crisp and inexact data, and have the possibility of fuzzy querying in both crisp and fuzzy databases. Traditional databases use only crisp data and they are only capable of manipulating them using Boolean logic, while in a reasonable number of situations we are faced with uncertain, approximate and vague data. In those situations, it may not be reasonable to transform these data into crisp forms. Fuzzy databases, on the other hand, are capable of storing and retrieving both, crisp and non-crisp data and to manipulate them using fuzzy logic. This paper proposes a possibility-based fuzzy relational database management system. Mechanisms to design and implement the database are shown and query processing methods are described. Fuzzy queries are first translated into SQL and then passed to the MS-SQL server to process them. The result is finally fuzzified. A user can express his (her) request using linguistic terms and can choose different retrieval threshold values. The system is then used to store information about patients whose bone density is measured for diagnosis of osteoporosis. It is shown to be more flexible and has produced more accurate results compared to a crisp database
Fuzzy relational data model
database
fuzzy query processing
Osteoporosis
2013
02
17
651
667
Iranian Journal of Science and Technology Transactions of Electrical Engineering
2228-6179
2228-6179
2003
27
4
Position control of three-phase induction motors using sliding mode control strategy and its implementation
Speed control of induction motors has been the focus of attention in previous last decades, but controlling the position of rotor of induction motors has received little attention. In induction motors, the rotor voltage is induced by a stator field, therefore producing static torque and controlling the position of the rotor is quite difficult. Vector control has been proposed for this problem, however it requires huge calculations and an exact model of the system. In this paper a very simplified model is used and sliding control strategy has been proposed to overcome the shortcomings of the previous model. This approach requires fewer calculations and does not need an exact model. Nevertheless, the simulation results show a very good performance compared with other approaches. To show the strength of the control strategy, it has been implemented on a 2.2 kw three-phase induction motor.
Induction motor
variable structure
sliding mode
position control
2013
02
17
669
678
Iranian Journal of Science and Technology Transactions of Electrical Engineering
2228-6179
2228-6179
2003
27
4
A modified reaching phase sliding mode controller for a speed sensorless inducting motor drive using feedback linearization theory
A speed sensorless induction motor drive (IMD) with a modified reaching phase sliding mode controller is introduced. The rotor flux is estimated first, with a simplified rotor flux observer in the rotor reference frame and the feedback linearization theory is used to decouple the dynamic of the motor torque and rotor flux amplitude. Then, a modified reaching sliding mode controller is designed to control the speed of the IMD so that the chattering effects associated with the classical sliding mode speed controllers is eliminated and a fast transient response is also achieved. In addition, a Luenberger speed observer is designed to estimate the IMD speed from the measured terminal voltages and currents. The effectiveness of the proposed approach is demonstrated by a digital simulation study.
Induction motor
sliding mode
speed controller
sensorless
feedback linearization
2013
02
17
679
689
Iranian Journal of Science and Technology Transactions of Electrical Engineering
2228-6179
2228-6179
2003
27
4
Design of active suspension control using singular perturbation theory
The presence of fast and slow modes in vehicle suspension systems based on a half car model, is utilized in the design of active suspension control using singular perturbation theory. This strategy is based on the slow-fast control design. The suspension system performance is optimised with respect to ride comfort, road holding and suspension rattle space as expressed by the mean-square-values of body acceleration (including effects of heave and pitch), tire deflections and front and rear suspension travels. The method of design in this study is based on LQG feedback control combined with singular perturbation theory, and at the end, a composite LQG controller has been proposed. Numerical simulations in the time domain evaluate the performance of the active suspension system. In spite of the simplified structure of the composite model, simulation results indicate that its performance is comparable to that of the full-state feedback design.
Active suspension system
optimal control
singular perturbation theory
LQG
Kalman filter
2013
02
17
691
700
Iranian Journal of Science and Technology Transactions of Electrical Engineering
2228-6179
2228-6179
2003
27
4
Optimal pulse shapes for periodic reverse electroplating
In this report, time-dependent carrier concentration in electrolytic cells, due to some basic periodic shapes of excitation signal, has been studied. Exact analytical solutions for step, sinusoidal and periodic pulse reverse inputs are derived. The effect of frequency, forward and reverse amplitudes and duty cycle are investigated. An analytical solution of the model is obtained as Fourier series using Laplace transformations applied to a one-dimensional model with linearized Butler-Volmer electrode kinetics. The results are applied to an acid-copper bath. It is shown that optimal operation points exist. Optimal current waveforms for obtaining an efficient and enhanced deposition process, and faster deposition rate compared to simple DC electroplating is discussed.
Electroplating
Laplace transformation
diffusion
Optimization
electrolyte
Butler-Volmer
2013
02
17
701
711
Iranian Journal of Science and Technology Transactions of Electrical Engineering
2228-6179
2228-6179
2003
27
4
Design of power system stabilizers based on robust control theory
This paper describes the design of robust power system stabilizers (PSS) for a single generator tie line (SGTL) power system. Unlike the conventional PSS design based on a single system operating point, the proposed method develops a more realistic approach by taking into account various uncertainties involved in power system operation and modelling such as disturbances, modelling errors, changes in the system parameters, system structure and operating conditions. This approach provides a technique for determining stabilizer transfer function for a region of power system operating points establishing a demarcation line between stable and unstable areas on the complex power plane. The Nevanlinna-Pick theory is applied to obtain the final transfer function. The design procedure is demonstrated for a system with typical parameters. Extensive simulation results are presented to confirm the superiority of the proposed PSS in comparison with a conventional PSS.
Power systems
dynamic stability
stabilizers
PSS
robust stability
2013
02
17
713
726
Iranian Journal of Science and Technology Transactions of Electrical Engineering
2228-6179
2228-6179
2003
27
4
Application of unified power flow controller (UPFC) for damping torsional oscillations
This paper investigates the feasibility of application of a unified power flow controller (UPFC) to damp subsynchronous resonance in a power system. The basic dynamic characteristics of the UPFC and its parameters impact on SSR modes are investigated, and based on the introduced control strategy, its ability of damping SSR for sample study systems is demonstrated.
UPFC
subsynchronous resonance
FACTS
2013
02
17
727
736
Iranian Journal of Science and Technology Transactions of Electrical Engineering
2228-6179
2228-6179
2003
27
4
Computer simulation of vector controlled slip-energy recovery induction machine drives
This paper describes the vector control of a high capacity power slip-energy recovery induction machine drive below and above the synchronous speed. Using an x and y rotating reference frame with an x-axis coincides with the stator vector flux. The stator and rotor variables are transformed on to this reference frame first. The nonlinear equations of the drive system are derived based on the separate and stable control of active and reactive powers. To improve the drive system performance, a trapezoidal modulated current source inverter is used in the rotor circuit with a less varible power factor and lower harmonic pollution. This also helps to reduce the torque ripples and the torsional mode resonances especially for the generating modes of operation. A step by step computer program has been developed in order to simulate the drive system on PC. The simulation results are obtained for a high power capacity drive system in the motoring and generating modes of operation (below and above the synchronous speed).
Induction machine
vector control
CSI inverter
slip energy recovery
2013
02
17
737
750
Iranian Journal of Science and Technology Transactions of Electrical Engineering
2228-6179
2228-6179
2003
27
4
Transient analysis of switched reluctance motors
The prediction methods for steady-state performance of switched reluctance motors (SRMs) have been in place for some time; however, little attention has been paid to the transient analysis of the machine. This paper reports the effects of various faults, loading and unloading, as well as starting on the transient behavior of SRM. Results are presented to illustrate that faulty conditions will not produce serious problems in the operation of SRMs
Switched reluctance motor
transient operation
2013
02
17
751
762
Iranian Journal of Science and Technology Transactions of Electrical Engineering
2228-6179
2228-6179
2003
27
4
A novel approach to broken bar detection in induction motor via wavelet transformation
This paper presents a novel approach for the detection of broken rotor bars in induction motors based on the wavelet transformation. A multi-resolution signal decomposition based on wavelet transform or wavelet packet provides a set of decomposed signals in independent frequency bands which contain a large amount of independent dynamic information due to the orthogonality of wavelet functions. Wavelet transform and wavelet packet in tandem with some signal processing methods such as autoregressive spectrum, energy monitoring, fractal dimension, etc., can produce many desirable results for condition monitoring and the fault diagnosis of an induction motor. Broken bar detection is based on decomposing the stator currents, and then extracting the wavelet coefficients of these signals. Comparing these extracted coefficients can diagnose a healthy machine from a faulty machine. Experimental results are presented in healthy, two, three, four, and five broken bars. Deviation of wavelet coefficients in a healthy mode from a faulty mode shows the number of broken bars in the rotor cage. Simulation and experimental results show the effectiveness of the proposed method for broken rotor bar detection in squirrel cage induction motors
Wavelet
Induction motor
broken bars
fault diagnosis
2013
02
17
763
770
Iranian Journal of Science and Technology Transactions of Electrical Engineering
2228-6179
2228-6179
2003
27
4
IUSTA, a prioritized multicast ATM switch: design and performance evaluation
In this paper, a new approach has been introduced for the design of an ATM switching system. IUSTA (Iran University of Science & Technology ATM switch) is proposed as ATM switch architecture based on a knockout principle with output queuing. Intrinsic broadcast, multicast capabilities and priority functionality are important features of IUSTA. In this paper an architectural design is provided to construct arbitrary large switches based on simple basic building blocks. By use of these features, IUSTA reaches to 10-14 for cell loss probability with the modest size component
ATM switch
multicast
performance evaluation
knockout
priority
2013
02
17
771
782
Iranian Journal of Science and Technology Transactions of Electrical Engineering
2228-6179
2228-6179
2003
27
4
Time domain characterization of the microwave PIN diode driven by high speed digital data
An accurate model to characterise a PIN diode as a variable resistor driven by high speed digital data and RF pump signals is presented. The model extracts the electron density function resulting from these signal drives. This is used to obtain a closed form expression for the PIN diode resistance. The residue theorem and complex inversion formula are used to solve the PN junction equations. A high speed reflection pulse amplitude modulator, which is an essential block for implementing more complex digital modulators, is also examined using this model. The results may be applied to realize a high speed digital modulator using silicon monolithic microwave integrated circuits.
Microwave modulator
microwave PIN diode
high speed data
2013
02
17
783
798
Iranian Journal of Science and Technology Transactions of Electrical Engineering
2228-6179
2228-6179
2003
27
4
Optimal control of unified power flow controller (UPFC) to enhance power system transient stability
This paper investigates the feasibility of a unified power flow controller (UPFC) to improve power system transient stability. Based on the developed model, the impact of control strategy, parameters, and location of UPFC on power system transient stability are discussed. The direct method approach is used for this study, because its simplicity enhances understanding of the measures that have been taken to improve stability
UPFC
Transient stability analysis
FACTS
direct method approach
2013
02
17
799
806
Iranian Journal of Science and Technology Transactions of Electrical Engineering
2228-6179
2228-6179
2003
27
4
Using reconstructed induction currents for solving the inverse scattering problem
In this article, after reviewing of the inverse source and inverse scattering problems, two quantetive and qualitative (a new method) of solving the inverse scattering problem using reconstructed induction currents are studied.
Inverse scattering
induction currents
quantitative and qualitative solution
2013
02
17
807
810
Iranian Journal of Science and Technology Transactions of Electrical Engineering
2228-6179
2228-6179
2003
27
4
Two-level fuzzy control of large-scale systems and its application into PSS design
This paper proposes a two-level suboptimal control using fuzzy prediction to control large-scale systems. A class of large-scale linear systems composed of interconnected subsystems is investigated. The overall control problem that is posed as a minimization of overall objective function, which is considered to be of quadratic form, is reduced to some optimization problems of lower order (sub) systems. The control input of each subsystem is composed of two signals. The first represents the local control signal (first level) and the second is the prediction signal (second level). In fact, the second signal is the prediction of interaction of other subsystems. It applies to each subsystem at every specified sample time (coordination sample times). The fuzzy logic theory is used for interaction prediction, where the prediction signal is constructed by a set of fuzzy sets with respect to state variables in an appropriate inference engine manner. The number of fuzzy sets and their interval deviations vary with time. Finally, the proposed method is applied to a three-area power system for designing a power system stabilizer (PSS)
decentralized control
large-scale systems
fuzzy logic theory
Power system stabilizer
2013
02
17
811
818