Documents disponibles écrits par cet auteur

Analytical approach for detection of multiple cracks in a beam / Xiaoqing, Zhang in Journal of engineering mechanics, Vol. 136 N° 3 (Mars 2010) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 136 N° 3 (Mars 2010) . - pp. 345-357 Titre : Analytical approach for detection of multiple cracks in a beam Type de document : texte imprimé Auteurs : Xiaoqing, Zhang, Auteur ; Qiang, Han, Auteur ; Feng, Li, Auteur Article en page(s) : pp. 345-357 Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : Cracking  Vibration  Beams  Analytical  techniques. Résumé : An analytical approach for the detection of a beam with multiple cracks is presented in this article. The method is based on the bending vibration theory of Euler-Bernoulli beam and the cracks are treated as massless rotational springs, by which the cracked beam is separated into a number of segments of perfect beams. By using the nontrivial solution condition of the vibration mode of the beam elements, specially using the transfer matrix method for the multiple cracks detection, the crack identification equation of the cracked beam is obtained explicitly, which is a function of natural frequencies, the locations, and depths of the cracks. Since the natural frequencies of a cracked beam can be measured through many of the structural testing methods, then the relations of the locations and the depths of the cracks can be determined explicitly from the identification equation of a cracked beam which geometrical and physical parameters as well as the boundary conditions are given. The results of some examples are shown and the present method is validated with the existing and measured experimental data. The detection for other types of beams with different number of cracks and various boundary conditions can also be obtained by a similar procedure. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.aip.org/vsearch/servlet/VerityServlet?KEY=JENMDT&ON [article] Analytical approach for detection of multiple cracks in a beam [texte imprimé] / Xiaoqing, Zhang, Auteur ; Qiang, Han, Auteur ; Feng, Li, Auteur . - pp. 345-357. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 136 N° 3 (Mars 2010) . - pp. 345-357 Mots-clés : Cracking  Vibration  Beams  Analytical  techniques. Résumé : An analytical approach for the detection of a beam with multiple cracks is presented in this article. The method is based on the bending vibration theory of Euler-Bernoulli beam and the cracks are treated as massless rotational springs, by which the cracked beam is separated into a number of segments of perfect beams. By using the nontrivial solution condition of the vibration mode of the beam elements, specially using the transfer matrix method for the multiple cracks detection, the crack identification equation of the cracked beam is obtained explicitly, which is a function of natural frequencies, the locations, and depths of the cracks. Since the natural frequencies of a cracked beam can be measured through many of the structural testing methods, then the relations of the locations and the depths of the cracks can be determined explicitly from the identification equation of a cracked beam which geometrical and physical parameters as well as the boundary conditions are given. The results of some examples are shown and the present method is validated with the existing and measured experimental data. The detection for other types of beams with different number of cracks and various boundary conditions can also be obtained by a similar procedure. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.aip.org/vsearch/servlet/VerityServlet?KEY=JENMDT&ON

Average-value modeling of brushless DC motors with 120° voltage source inverter / Qiang, Han in IEEE transactions on energy conversion, Vol. 23 n°2 (Juin 2008) 

Public ISBD [article]  in IEEE transactions on energy conversion > Vol. 23 n°2 (Juin 2008) . - pp. 423 - 432 Titre : Average-value modeling of brushless DC motors with 120° voltage source inverter Type de document : texte imprimé Auteurs : Qiang, Han, Auteur ; Samoylenko, N., Auteur ; Jatskevich, J., Auteur Année de publication : 2008 Article en page(s) : pp. 423 - 432 Note générale : Energy conversion Langues : Anglais (eng) Mots-clés : Brushless  DC  motors;  commutation;  invertors;  nonlinear  equations;  permanent  magnet  machines;  stators;  switching  convertors;  synchronous  machines Résumé : This paper describes average-value modeling of brushless dc (BLDC) motor-inverter systems, which is challenging due to the complicated switching patterns of the stator currents. A new average-value model (AVM) that appropriately includes commutation and conduction subintervals of the BLDC motor with a 120deg inverter is presented. The proposed model is explicit and uses a proper qd model of the permanent magnet synchronous machine. The required commutation angle is represented as a nonlinear algebraic function, which is readily obtained from the detailed simulation. The studies conducted are based on two typical industrial motors with different electrical time constants, and include hardware measurements, detailed simulation, and comparison with a previously published AVM. The proposed model is shown to be more accurate in terms of both large and small-signal analysis and is applicable to both types of motors. En ligne : http://ieeexplore.ieee.org/xpl/articleDetails.jsp?arnumber=4505390&sortType%3Das [...] [article] Average-value modeling of brushless DC motors with 120° voltage source inverter [texte imprimé] / Qiang, Han, Auteur ; Samoylenko, N., Auteur ; Jatskevich, J., Auteur . - 2008 . - pp. 423 - 432. Energy conversion Langues : Anglais (eng) in IEEE transactions on energy conversion > Vol. 23 n°2 (Juin 2008) . - pp. 423 - 432 Mots-clés : Brushless  DC  motors;  commutation;  invertors;  nonlinear  equations;  permanent  magnet  machines;  stators;  switching  convertors;  synchronous  machines Résumé : This paper describes average-value modeling of brushless dc (BLDC) motor-inverter systems, which is challenging due to the complicated switching patterns of the stator currents. A new average-value model (AVM) that appropriately includes commutation and conduction subintervals of the BLDC motor with a 120deg inverter is presented. The proposed model is explicit and uses a proper qd model of the permanent magnet synchronous machine. The required commutation angle is represented as a nonlinear algebraic function, which is readily obtained from the detailed simulation. The studies conducted are based on two typical industrial motors with different electrical time constants, and include hardware measurements, detailed simulation, and comparison with a previously published AVM. The proposed model is shown to be more accurate in terms of both large and small-signal analysis and is applicable to both types of motors. En ligne : http://ieeexplore.ieee.org/xpl/articleDetails.jsp?arnumber=4505390&sortType%3Das [...]

Dynamic performance of brushless DC motors with unbalanced hall sensors / Samoylenko, N. in IEEE transactions on energy conversion, Vol. 23 n°3 (Septembre 2008) 

Public ISBD [article]  in IEEE transactions on energy conversion > Vol. 23 n°3 (Septembre 2008) . - pp. 752 - 763 Titre : Dynamic performance of brushless DC motors with unbalanced hall sensors Type de document : texte imprimé Auteurs : Samoylenko, N., Auteur ; Qiang, Han, Auteur ; Jatskevich, J., Auteur Année de publication : 2008 Article en page(s) : pp. 752 - 763 Note générale : Energy conversion Langues : Anglais (eng) Mots-clés : Hall  effect  transducers;  brushless  DC  motors;  torque Résumé : Brushless dc (BLDC) motors controlled by Hall-effect sensors are widely used in various applications and have been extensively researched in the literature, mainly under the assumption that the Hall sensors are ideally placed 120 electrical degrees apart. However, this assumption is not always valid; in fact, sensor placement may be significantly inaccurate, especially in medium- and low-precision BLDC machines. This paper shows that misplaced Hall sensors lead to unbalanced operation of the inverter and motor phases, which increases the low-frequency harmonics in torque ripple and degrades the overall drive performance. The paper also presents several average-filtering techniques that can be applied to the original Hall-sensor signals to mitigate the effect of unbalanced placement during steady-state and transient operations. The proposed methodology is demonstrated by modeling and hardware, and is shown to achieve dynamic performance similar to that of a BLDC motor with accurately positioned Hall sensors. En ligne : http://ieeexplore.ieee.org/xpl/articleDetails.jsp?arnumber=4537158&sortType%3Das [...] [article] Dynamic performance of brushless DC motors with unbalanced hall sensors [texte imprimé] / Samoylenko, N., Auteur ; Qiang, Han, Auteur ; Jatskevich, J., Auteur . - 2008 . - pp. 752 - 763. Energy conversion Langues : Anglais (eng) in IEEE transactions on energy conversion > Vol. 23 n°3 (Septembre 2008) . - pp. 752 - 763 Mots-clés : Hall  effect  transducers;  brushless  DC  motors;  torque Résumé : Brushless dc (BLDC) motors controlled by Hall-effect sensors are widely used in various applications and have been extensively researched in the literature, mainly under the assumption that the Hall sensors are ideally placed 120 electrical degrees apart. However, this assumption is not always valid; in fact, sensor placement may be significantly inaccurate, especially in medium- and low-precision BLDC machines. This paper shows that misplaced Hall sensors lead to unbalanced operation of the inverter and motor phases, which increases the low-frequency harmonics in torque ripple and degrades the overall drive performance. The paper also presents several average-filtering techniques that can be applied to the original Hall-sensor signals to mitigate the effect of unbalanced placement during steady-state and transient operations. The proposed methodology is demonstrated by modeling and hardware, and is shown to achieve dynamic performance similar to that of a BLDC motor with accurately positioned Hall sensors. En ligne : http://ieeexplore.ieee.org/xpl/articleDetails.jsp?arnumber=4537158&sortType%3Das [...]