PREDICTION ALGORITHM FOR TORQUE RIPPLE REDUCTION IN DTC-BASED DRIVES
SH.
KABOLI
Electrical Engineering Department, Sharif University of Technology, Tehran, I. R. of Iran
author
M. R.
ZOLGHADRI
Electrical Engineering Department, Sharif University of Technology, Tehran, I. R. of Iran
author
P.
ESKANDARI
Electrical Engineering Department, Sharif University of Technology, Tehran, I. R. of Iran
author
D.
ROYE
Polytechnic Institute of Grenoble, France
author
text
article
2008
eng
In direct torque control, the selection of an applied voltage vector is based on the measuredparameters at the beginning of the sampling period. The delay between the measurement and the application of the voltage vector is the origin of an extra torque ripple. In this paper, a new predictive controller is proposed for compensating this delay and reducing the torque ripple. The stator current is measured twice in each sampling period and its expected value at the end of the period is predicted according to a linear extrapolation algorithm. Therefore, none of the machine parameters are used in the prediction, and consequently, the algorithm is quite robust against machine parameter variations. The calculation of the electromagnetic torque is performed using the predicted value of the stator current. Therefore, the selection of the voltage vector is more realistic and prevents extra torque ripple. This controller is quite suitable for high power drives where the sampling frequency is low, and there is enough time for the extra measurements. Simulation and experimental results which confirm the ability of this method to considerably reduce the torque ripple are presented.
Iranian Journal of Science and Technology (Sciences)
Springer
1028-6276
32
v.
4
no.
2008
343
355
http://ijsts.shirazu.ac.ir/article_2293_6c5b2a8ddd45315cdaa43ae301dfacd6.pdf
dx.doi.org/10.22099/ijsts.2008.2293
(Aσ )Δ -DOUBLE SEQUENCE SPACES VIA ORLICZ FUNCTIONS AND DOUBLE STATISTICAL CONVERGENCE
E.
SAVAS
Istanbul Ticaret University, Department of Mathematics, Uskudar, Istanbul, Turkey
author
R. F.
PATTERSON
Department of Mathematics and Statistics, University of North Florida, Jacksonville, Florida 32224, USA
author
text
article
2008
eng
The aim of this paper is to introduce and study a new concept of strong double Δ ( A ) σ -convergence sequences with respect to an Orlicz function, and some properties of the resulting sequencespaces were also examined. In addition, we define the Δ ( A ) σ -statistical convergence and establish someconnections between the spaces of strong double Δ ( A ) σ -convergence sequences and the space of doubleΔ ( A ) σ -statistical convergence.
Iranian Journal of Science and Technology (Sciences)
Springer
1028-6276
32
v.
4
no.
2008
357
367
http://ijsts.shirazu.ac.ir/article_2294_7b3faf5ebb8fb2aa2b49a4f784cc4981.pdf
dx.doi.org/10.22099/ijsts.2008.2294
LINEAR PROGRAMMING PROBLEM WITH INTERVAL COEFFICIENTS AND AN INTERPRETATION FOR ITS CONSTRAINTS
A.
ABBASI MOLAI
Faculty of Mathematics and Computer Science, Amirkabir University of
Technology, Hafez Avenue, Tehran, I. R. of Iran
author
E.
KHORRAM
Faculty of Mathematics and Computer Science, Amirkabir University of
Technology, Hafez Avenue, Tehran, I. R. of Iran
author
text
article
2008
eng
In this paper, we introduce a Satisfaction Function (SF) to compare interval values on the basis ofTseng and Klein’s idea. The SF estimates the degree to which arithmetic comparisons between two intervalvalues are satisfied. Then, we define two other functions called Lower and Upper SF based on the SF. Weapply these functions in order to present a new interpretation of inequality constraints with intervalcoefficients in an interval linear programming problem. This problem is as an extension of the classical linear programming problem to an inexact environment. On the basis of definitions of the SF, the lower and upper SF and their properties, we reduce the inequality constraints with interval coefficients in their satisfactory crisp equivalent forms and define a satisfactory solution to the problem. Finally, a numerical example is given and its results are compared with other approaches
Iranian Journal of Science and Technology (Sciences)
Springer
1028-6276
32
v.
4
no.
2008
369
390
http://ijsts.shirazu.ac.ir/article_2295_468f16722b798e7ccc781d7fd54c9b49.pdf
dx.doi.org/10.22099/ijsts.2008.2295
AUTOCORRELATION FOR A CLASS OF POLYNOMIALS WITH COEFFICIENTS DEFINED ON T
M.
TAGHAVI
Department of Mathematics, College of Sciences, Shiraz University, Shiraz, I. R. of Iran
author
text
article
2008
eng
In this work we deal with the coefficients of A (e it ) 2 , where A is in a class of polynomialshaving Unimodular coefficients. We first present a technique that calculates lower bounds for particularautocorrelations and then in a more general case we present an upper bound for their maximal order.
Iranian Journal of Science and Technology (Sciences)
Springer
1028-6276
32
v.
4
no.
2008
391
396
http://ijsts.shirazu.ac.ir/article_2296_56872c197938e0e404d49c7f95efc4cb.pdf
dx.doi.org/10.22099/ijsts.2008.2296
DOSIMETRIC EVALUATION OF A NEWLY DEVELOPED RADIOCHROMIC FILM FOR RADIATION PROCESSING
A.
AKHAVAN
Radiation Applications Research School, Nuclear Science and Technology Research Institute,
P.O. Box 11365-3486 Tehran, I. R. of Iran
author
M.
SOHRABPOUR
Department of Energy Engineering, Sharif University of Technology, Tehran, I. R. of Iran
author
M.
SHARIFZADEH
Radiation Applications Research School, Nuclear Science and Technology Research Institute,
P.O. Box 11365-3486 Tehran, I. R. of Iran
author
text
article
2008
eng
In order to improve the performance of a newly developed radiochromic film, GIC-79, somedosimetric characteristics of this film have been studied based on relevant standard practice. The presentstudy describes some parameters that may affect the dosimeter response before, during, and after irradiation. The effect of absorbed dose rate on dosimeter response was determined by irradiating dosimeters at low absorbed dose rates with gamma rays. Calibration irradiations of dosimeters were performed with both gamma rays and also electrons to determine the effect of large difference absorbed dose rates on dosimeter response. In addition, post irradiation stability was obtained and also the temperature and humidity effects on the dosimeter response during the storage time prior to irradiation and post irradiation have been investigated
Iranian Journal of Science and Technology (Sciences)
Springer
1028-6276
32
v.
4
no.
2008
397
401
http://ijsts.shirazu.ac.ir/article_2297_7234ac0ffa0fca0d2f7bd6bc72de1224.pdf
dx.doi.org/10.22099/ijsts.2008.2297
ON EINSTEIN (α,β )-METRICS
B.
REZAEI
Department of Mathematics and Computer Science of Amir-Kabir University, Tehran, I. R. of Iran
author
A.
RAZAVI
Department of Mathematics and Computer Science of Amir-Kabir University, Tehran, I. R. of Iran
author
N.
SADEGHZADEH
Department of Mathematics and Computer Science of Amir-Kabir University, Tehran, I. R. of Iran
author
text
article
2008
eng
– In this paper we consider some (α ,β ) -metrics such as generalized Kropina, Matsumoto and F (α β )2α = + metrics, and obtain necessary and sufficient conditions for them to be Einstein metrics when βis a constant Killing form. Then we prove with this assumption that the mentioned Einstein metrics must beRiemannian or Ricci flat.
Iranian Journal of Science and Technology (Sciences)
Springer
1028-6276
32
v.
4
no.
2008
403
412
http://ijsts.shirazu.ac.ir/article_2298_e9e30572a219839fc8b166c53a696227.pdf
dx.doi.org/10.22099/ijsts.2008.2298
IONOSPHERIC ABSORPTION OF HF RADIO WAVE IN VERTICAL PROPAGATION
I.
UNAL
Department of Science Teaching, Faculty of Education, Inonu Univ., 44280 Malatya, Turkey
author
O.
OZCAN
Department of Physics, Faculty of Science and Arts, Firat Univ., 23169 Elazig, Turkey
author
M.
CANYILMAZ
Department of Physics, Faculty of Science and Arts, Firat Univ., 23169 Elazig, Turkey
author
text
article
2008
eng
In this study, absorption of high frequency radio waves in the ionospheric plasma have beeninvestigated. The wave equation was obtained in terms of ionospheric parameters. The numerical values ofthe absorption have been calculated for 4 MHz, 4.5 MHz and 5 MHz waves. The necessary parameters forcalculation have been obtained using an International Reference Ionosphere (IRI) Model. The altitudinal,diurnal, seasonal and the variations of absorption with frequency have been examined. The calculations showthat the highest absorption occurs in the D-region. The absorption is higher in summer than in other seasonsand is maximum at daylight. In addition, absorption decreases with the increase of frequency.
Iranian Journal of Science and Technology (Sciences)
Springer
1028-6276
32
v.
4
no.
2008
413
419
http://ijsts.shirazu.ac.ir/article_2299_bf9f6139f8a03ab62b0f67f9b28d9c4d.pdf
dx.doi.org/10.22099/ijsts.2008.2299
PROJECTIVELY RELATED EINSTEIN FINSLER SPACES
N.
SADEGH-ZADEH
Department of Mathematics and Computer Science of Amir-Kabir University, Tehran, I. R. of Iran
author
A.
RAZAVI
Department of Mathematics and Computer Science of Amir-Kabir University, Tehran, I. R. of Iran
author
B.
REZAEI
Department of Mathematics and Computer Science of Amir-Kabir University, Tehran, I. R. of Iran
author
text
article
2008
eng
The main objective of this paper is to find the necessary and sufficient condition of a given Finslermetric to be Einstein in order to classify the Einstein Finsler metrics on a compact manifold. The consideredEinstein Finsler metric in the study describes all different kinds of Einstein metrics which are pointwiseprojective to the given one. This study has resulted in the following theorem that needs the proof of threeprepositions. Let F be a Finsler metric (n > 2) projectively related to an Einstein non-projectively flatFinsler metric F , then F is Einstein if and only if F = λ F whereλ is a constant. A Schur type lemma isalso proved.
Iranian Journal of Science and Technology (Sciences)
Springer
1028-6276
32
v.
4
no.
2008
421
429
http://ijsts.shirazu.ac.ir/article_2300_1d2fa8ed46454558cc9c742c54cbf50f.pdf
dx.doi.org/10.22099/ijsts.2008.2300
VELOCITIES OF DUAL HOMOTHETIC EXPONENTIAL MOTIONS IN D3*
V.
ASIL
Department of Mathematics Faculty of Art and Science Fırat University, 23119 Elazıg, Turkey
author
text
article
2008
eng
In this paper the concept of Homothetic Dual Exponential Motions in D3 is discussed and theirvelocities obtained. Due to the way in which the matter is presented, the paper gives some formula and factsabout dual exponential motions which are not generally known
Iranian Journal of Science and Technology (Sciences)
Springer
1028-6276
32
v.
4
no.
2008
431
434
http://ijsts.shirazu.ac.ir/article_2301_ddbd28d4f0af1df8d5fe9132a5dc9bd1.pdf
dx.doi.org/10.22099/ijsts.2008.2301
BOUND STATE ENERGY OF DELTA-FUNCTION POTENTIAL: A NEW REGULARIZATION SCHEME
A.
JAHAN
Department of Physics, Amirkabir University of Technology, P. O. Box 15875-4413, Tehran, I. R. of Iran
author
M.
JAFARI
Islamic Azad University, Urmia branch, Urmia, I. R. of Iran
author
text
article
2008
eng
In this letter we have proposed a new regularization scheme to deal with the divergent integralsoccurring in the quantum mechanical problem of calculating the bound state energy of the delta-functionpotential in two and three dimensions. Based on the Schwinger parameterization technique we argue thatthere are no infinities even in D dimensions. In this way we were able to compare our proposal with theSchwinger regularization approch.
Iranian Journal of Science and Technology (Sciences)
Springer
1028-6276
32
v.
4
no.
2008
435
438
http://ijsts.shirazu.ac.ir/article_2302_eb38ee6e1732a8150067147ff55416f4.pdf
dx.doi.org/10.22099/ijsts.2008.2302
ON R-QUADRATIC FINSLER METRICS
B.
NAJAFI
Department of Science, Shahed University, Tehran, I. R. of Iran
author
B.
BIDABAD
Department of Mathematics and Computer Science, Amir Kabir University, Tehran, I. R. of Iran
author
A.
TAYEBI
Department of Mathematics, Faculty of Science, The University of Qom, Qom, I. R. of Iran
author
text
article
2008
eng
We prove that every R-quadratic metric of scalar flag curvature with a dimension greater than twois of constant flag curvature. Then we show that generalized Douglas-Weyl metrics contain R-quadraticmetrics as a special case, but the class of R-quadratic metric is not closed under projective transformations
Iranian Journal of Science and Technology (Sciences)
Springer
1028-6276
32
v.
4
no.
2008
439
443
http://ijsts.shirazu.ac.ir/article_2303_b1d104fd19fc0b74b7c8c77b82ef8f94.pdf
dx.doi.org/10.22099/ijsts.2008.2303