Documents disponibles écrits par cet auteur

Development of direct integration algorithms for structural dynamics using discrete control theory / Cheng Chen in Journal of engineering mechanics, Vol. 134 n°8 (Août 2008) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 134 n°8 (Août 2008) . - pp. 676–683. Titre : Development of direct integration algorithms for structural dynamics using discrete control theory Type de document : texte imprimé Auteurs : Cheng Chen, Auteur ; Ricles, James M., Auteur Année de publication : 2008 Article en page(s) : pp. 676–683. Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : Algorithms  Structural  dynamics  Transfer  functions  Stability  Discrete  elements Résumé : In structural dynamics, integration algorithms are often used to obtain the solution of temporally discretized equations of motion at selected time steps. Various time integration algorithms have been developed in the time domain using different methods. In order for an integration algorithm to be reliable it must be stable and accurate. A discrete transfer function is used to study the properties of integration algorithms. A pole mapping rule from control theory in conjunction with a discrete transfer function is used to develop new integration algorithms for obtaining solutions to structural dynamics problems. A new explicit integration algorithm, called the CR (Chen and Ricles) algorithm, is subsequently developed based on the proposed method. The properties of the algorithm are investigated and compared with other well established algorithms such as the Newmark family of integration algorithms. By assigning proper stable poles to the discrete transfer function the newly developed CR explicit algorithm is unconditionally stable and has the same accuracy as the Newmark method with constant acceleration. In addition, the CR algorithm is based on expressions for displacement and velocity that are both explicit in form, making it an appealing integration algorithm for solving structural dynamics problems. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282008%29134%3A8%2867 [...] [article] Development of direct integration algorithms for structural dynamics using discrete control theory [texte imprimé] / Cheng Chen, Auteur ; Ricles, James M., Auteur . - 2008 . - pp. 676–683. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 134 n°8 (Août 2008) . - pp. 676–683. Mots-clés : Algorithms  Structural  dynamics  Transfer  functions  Stability  Discrete  elements Résumé : In structural dynamics, integration algorithms are often used to obtain the solution of temporally discretized equations of motion at selected time steps. Various time integration algorithms have been developed in the time domain using different methods. In order for an integration algorithm to be reliable it must be stable and accurate. A discrete transfer function is used to study the properties of integration algorithms. A pole mapping rule from control theory in conjunction with a discrete transfer function is used to develop new integration algorithms for obtaining solutions to structural dynamics problems. A new explicit integration algorithm, called the CR (Chen and Ricles) algorithm, is subsequently developed based on the proposed method. The properties of the algorithm are investigated and compared with other well established algorithms such as the Newmark family of integration algorithms. By assigning proper stable poles to the discrete transfer function the newly developed CR explicit algorithm is unconditionally stable and has the same accuracy as the Newmark method with constant acceleration. In addition, the CR algorithm is based on expressions for displacement and velocity that are both explicit in form, making it an appealing integration algorithm for solving structural dynamics problems. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282008%29134%3A8%2867 [...]

Improved adaptive inverse compensation technique for real-time hybrid simulation / Cheng Chen in Journal of engineering mechanics, Vol. 138 N° 12 (Décembre 2012) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 138 N° 12 (Décembre 2012) . - pp. 1432–1446. Titre : Improved adaptive inverse compensation technique for real-time hybrid simulation Type de document : texte imprimé Auteurs : Cheng Chen, Auteur ; James M. Ricles, Auteur ; Tong Guo, Auteur Année de publication : 2013 Article en page(s) : pp. 1432–1446. Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : Experimentation  Hybrid  methods  Substructures  Adaptive  systems Résumé : Real-time hybrid simulation provides an economical and efficient experimental technique for performance evaluation of structures under earthquakes. A successful real-time hybrid simulation requires accurate actuator control in order to achieve reliable experimental results. The time delay as a result of servohydraulic dynamics, if not compensated for properly, would lead to inaccurate or even unstable simulation results. However, the nonlinearities in servohydraulic systems and experimental substructures make the actuator delay difficult to accurately estimate in practice. Therefore, actuator control presents a challenge for the application of the real-time hybrid simulation technique to earthquake engineering research. This paper presents an improved adaptive inverse compensation technique for real-time hybrid simulation. Two adaptive control laws based on a synchronization subspace plot are introduced to adjust the compensation parameters in order to minimize both phase and amplitude errors in the servohydraulic actuator response. The improved adaptive inverse compensation method is experimentally evaluated through real-time tests involving a large-scale magneto-rheological damper subjected to band-limited white noise–generated random displacements and variable current inputs. The experimental results are compared with the command displacements, with the error assessed using various evaluation criteria. The improved adaptive inverse compensation is compared with an existing adaptive inverse compensation method to demonstrate the improvement that the newly developed compensation method offers in minimizing actuator delay. The proposed improved adaptive inverse compensation method is demonstrated to further improve actuator control by reducing not only actuator tracking errors but also associated energy errors. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29EM.1943-7889.0000450 [article] Improved adaptive inverse compensation technique for real-time hybrid simulation [texte imprimé] / Cheng Chen, Auteur ; James M. Ricles, Auteur ; Tong Guo, Auteur . - 2013 . - pp. 1432–1446. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 138 N° 12 (Décembre 2012) . - pp. 1432–1446. Mots-clés : Experimentation  Hybrid  methods  Substructures  Adaptive  systems Résumé : Real-time hybrid simulation provides an economical and efficient experimental technique for performance evaluation of structures under earthquakes. A successful real-time hybrid simulation requires accurate actuator control in order to achieve reliable experimental results. The time delay as a result of servohydraulic dynamics, if not compensated for properly, would lead to inaccurate or even unstable simulation results. However, the nonlinearities in servohydraulic systems and experimental substructures make the actuator delay difficult to accurately estimate in practice. Therefore, actuator control presents a challenge for the application of the real-time hybrid simulation technique to earthquake engineering research. This paper presents an improved adaptive inverse compensation technique for real-time hybrid simulation. Two adaptive control laws based on a synchronization subspace plot are introduced to adjust the compensation parameters in order to minimize both phase and amplitude errors in the servohydraulic actuator response. The improved adaptive inverse compensation method is experimentally evaluated through real-time tests involving a large-scale magneto-rheological damper subjected to band-limited white noise–generated random displacements and variable current inputs. The experimental results are compared with the command displacements, with the error assessed using various evaluation criteria. The improved adaptive inverse compensation is compared with an existing adaptive inverse compensation method to demonstrate the improvement that the newly developed compensation method offers in minimizing actuator delay. The proposed improved adaptive inverse compensation method is demonstrated to further improve actuator control by reducing not only actuator tracking errors but also associated energy errors. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29EM.1943-7889.0000450

Improving the inverse compensation method for real-time hybrid simulation through a dual compensation scheme / Cheng Chen in Earthquake engineering structural dynamics, Vol. 38 N° 10 (Août 2009) 

Public ISBD [article]  in Earthquake engineering structural dynamics > Vol. 38 N° 10 (Août 2009) . - pp. 1237-1255 Titre : Improving the inverse compensation method for real-time hybrid simulation through a dual compensation scheme Type de document : texte imprimé Auteurs : Cheng Chen, Auteur ; Ricles, James M., Auteur Article en page(s) : pp. 1237-1255 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Real-time;  Hybrid  simulation;  Actuator  delay;  Actuator  delay  compensation;  Frequency  response Index. décimale : 624.1 Infrastructures.Ouvrages en terre. Fondations. Tunnels Résumé : Real-time hybrid simulation combines experimental testing of physical substructure(s) and numerical simulation of analytical substructure(s), and thus enables the complete structural system to be considered during an experiment. Servo-hydraulic actuators are typically used to apply the command displacements to the physical substructure(s). Inaccuracy and instability can occur during a real-time hybrid simulation if the actuator delay due to servo-hydraulic dynamics is not properly compensated. Inverse compensation is a means to negate actuator delay due to inherent servo-hydraulic actuator dynamics during a real-time hybrid simulation. The success of inverse compensation requires the use of a known accurate value for the actuator delay. The actual actuator delay however may not be known before the simulation. An estimation based on previous experience has to be used, possibly leading to inaccurate experimental results. This paper presents a dual compensation scheme to improve the performance of the inverse compensation method when an inaccurately estimated actuator delay is used in the method. The dual compensation scheme modifies the predicted displacement from the inverse compensation procedure using the actuator tracking error. Frequency response analysis shows that the dual compensation scheme enables the inverse compensation method to compensate for actuator delay over a range of frequencies when an inaccurately estimated actuator delay is utilized. Real-time hybrid simulations of a single-degree-of-freedom system with an elastomeric damper are conducted to experimentally demonstrate the effectiveness of the dual compensation scheme. Exceptional experimental results are shown to be achieved using the dual compensation scheme without the knowledge of the actual actuator delay a priori. ISSN : 0098-8847 En ligne : www.interscience.wiley.com/journal/eqe [article] Improving the inverse compensation method for real-time hybrid simulation through a dual compensation scheme [texte imprimé] / Cheng Chen, Auteur ; Ricles, James M., Auteur . - pp. 1237-1255. Génie Civil Langues : Anglais (eng) in Earthquake engineering structural dynamics > Vol. 38 N° 10 (Août 2009) . - pp. 1237-1255 Mots-clés : Real-time;  Hybrid  simulation;  Actuator  delay;  Actuator  delay  compensation;  Frequency  response Index. décimale : 624.1 Infrastructures.Ouvrages en terre. Fondations. Tunnels Résumé : Real-time hybrid simulation combines experimental testing of physical substructure(s) and numerical simulation of analytical substructure(s), and thus enables the complete structural system to be considered during an experiment. Servo-hydraulic actuators are typically used to apply the command displacements to the physical substructure(s). Inaccuracy and instability can occur during a real-time hybrid simulation if the actuator delay due to servo-hydraulic dynamics is not properly compensated. Inverse compensation is a means to negate actuator delay due to inherent servo-hydraulic actuator dynamics during a real-time hybrid simulation. The success of inverse compensation requires the use of a known accurate value for the actuator delay. The actual actuator delay however may not be known before the simulation. An estimation based on previous experience has to be used, possibly leading to inaccurate experimental results. This paper presents a dual compensation scheme to improve the performance of the inverse compensation method when an inaccurately estimated actuator delay is used in the method. The dual compensation scheme modifies the predicted displacement from the inverse compensation procedure using the actuator tracking error. Frequency response analysis shows that the dual compensation scheme enables the inverse compensation method to compensate for actuator delay over a range of frequencies when an inaccurately estimated actuator delay is utilized. Real-time hybrid simulations of a single-degree-of-freedom system with an elastomeric damper are conducted to experimentally demonstrate the effectiveness of the dual compensation scheme. Exceptional experimental results are shown to be achieved using the dual compensation scheme without the knowledge of the actual actuator delay a priori. ISSN : 0098-8847 En ligne : www.interscience.wiley.com/journal/eqe

Real-time hybrid testing using the unconditionally stable explicit CR integration algorithm / Cheng Chen in Earthquake engineering structural dynamics, Vol. 38 N°1 (Janvier 2009) 

Public ISBD [article]  in Earthquake engineering structural dynamics > Vol. 38 N°1 (Janvier 2009) . - pp. 23-44 Titre : Real-time hybrid testing using the unconditionally stable explicit CR integration algorithm Type de document : texte imprimé Auteurs : Cheng Chen, Auteur Article en page(s) : pp. 23-44 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Integration  algorithm;  Real-time  hybrid  testing;  Stability  ;  Explicit;  Discrete  transfer  function Index. décimale : 624.1 Infrastructures.Ouvrages en terre. Fondations. Tunnels Résumé : Real-time hybrid testing combines experimental testing and numerical simulation, and provides a viable alternative for the dynamic testing of structural systems. An integration algorithm is used in real-time hybrid testing to compute the structural response based on feedback restoring forces from experimental and analytical substructures. Explicit integration algorithms are usually preferred over implicit algorithms as they do not require iteration and are therefore computationally efficient. The time step size for explicit integration algorithms, which are typically conditionally stable, can be extremely small in order to avoid numerical stability when the number of degree-of-freedom of the structure becomes large. This paper presents the implementation and application of a newly developed unconditionally stable explicit integration algorithm for real-time hybrid testing. The development of the integration algorithm is briefly reviewed. An extrapolation procedure is introduced in the implementation of the algorithm for real-time testing to ensure the continuous movement of the servo-hydraulic actuator. The stability of the implemented integration algorithm is investigated using control theory. Real-time hybrid test results of single-degree-of-freedom and multi-degree-of-freedom structures with a passive elastomeric damper subjected to earthquake ground motion are presented. The explicit integration algorithm is shown to enable the exceptional real-time hybrid test results to be achieved. ISSN : 0098-8847 En ligne : http://www3.interscience.wiley.com/journal/120853924/abstract [article] Real-time hybrid testing using the unconditionally stable explicit CR integration algorithm [texte imprimé] / Cheng Chen, Auteur . - pp. 23-44. Génie Civil Langues : Anglais (eng) in Earthquake engineering structural dynamics > Vol. 38 N°1 (Janvier 2009) . - pp. 23-44 Mots-clés : Integration  algorithm;  Real-time  hybrid  testing;  Stability  ;  Explicit;  Discrete  transfer  function Index. décimale : 624.1 Infrastructures.Ouvrages en terre. Fondations. Tunnels Résumé : Real-time hybrid testing combines experimental testing and numerical simulation, and provides a viable alternative for the dynamic testing of structural systems. An integration algorithm is used in real-time hybrid testing to compute the structural response based on feedback restoring forces from experimental and analytical substructures. Explicit integration algorithms are usually preferred over implicit algorithms as they do not require iteration and are therefore computationally efficient. The time step size for explicit integration algorithms, which are typically conditionally stable, can be extremely small in order to avoid numerical stability when the number of degree-of-freedom of the structure becomes large. This paper presents the implementation and application of a newly developed unconditionally stable explicit integration algorithm for real-time hybrid testing. The development of the integration algorithm is briefly reviewed. An extrapolation procedure is introduced in the implementation of the algorithm for real-time testing to ensure the continuous movement of the servo-hydraulic actuator. The stability of the implemented integration algorithm is investigated using control theory. Real-time hybrid test results of single-degree-of-freedom and multi-degree-of-freedom structures with a passive elastomeric damper subjected to earthquake ground motion are presented. The explicit integration algorithm is shown to enable the exceptional real-time hybrid test results to be achieved. ISSN : 0098-8847 En ligne : http://www3.interscience.wiley.com/journal/120853924/abstract

Simultaneous removal of SO2 and NO from flue gas using multicomposite active absorbent / Yi Zhao in Industrial & engineering chemistry research, Vol. 51 N° 1 (Janvier 2012) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 51 N° 1 (Janvier 2012) . - pp.480–486 Titre : Simultaneous removal of SO2 and NO from flue gas using multicomposite active absorbent Type de document : texte imprimé Auteurs : Yi Zhao, Auteur ; Yinghui Han, Auteur ; Cheng Chen, Auteur Année de publication : 2012 Article en page(s) : pp.480–486 Note générale : Chimie industrielle Langues : Anglais (eng) Mots-clés : Gas  Multicomposite Résumé : A multicomposite active absorbent was prepared using the liquid-phase complex of NaClO2 and NaClO as well as solid-phase slake lime to simultaneous desulfurization and denitrification at a flue gas circulating fluidized bed (CFB). The effects of influencing factors on the removal efficiencies of SO2 and NO were investigated. Removal efficiencies of 96.5% for SO2 and 73.5% for NO were obtained, respectively, under the optimal experimental conditions. The characterization of the spent absorbent was carried out by using energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), and chemical analysis methods, from which the simultaneous removal mechanism of SO2 and NO based on this absorbent was proposed. DEWEY : 660 ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie202617h [article] Simultaneous removal of SO2 and NO from flue gas using multicomposite active absorbent [texte imprimé] / Yi Zhao, Auteur ; Yinghui Han, Auteur ; Cheng Chen, Auteur . - 2012 . - pp.480–486. Chimie industrielle Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 51 N° 1 (Janvier 2012) . - pp.480–486 Mots-clés : Gas  Multicomposite Résumé : A multicomposite active absorbent was prepared using the liquid-phase complex of NaClO2 and NaClO as well as solid-phase slake lime to simultaneous desulfurization and denitrification at a flue gas circulating fluidized bed (CFB). The effects of influencing factors on the removal efficiencies of SO2 and NO were investigated. Removal efficiencies of 96.5% for SO2 and 73.5% for NO were obtained, respectively, under the optimal experimental conditions. The characterization of the spent absorbent was carried out by using energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), and chemical analysis methods, from which the simultaneous removal mechanism of SO2 and NO based on this absorbent was proposed. DEWEY : 660 ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie202617h

Stability analysis of direct integration algorithms applied to MDOF nonlinear structural dynamics / Cheng Chen in Journal of engineering mechanics, Vol. 136 N° 4 (Avril 2010) 

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Stability analysis of direct integration algorithms applied to MDOF nonlinear structural dynamics / Cheng Chen in Journal of engineering mechanics, Vol. 134 n°9 (Septembre 2008) 

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Tracking error-based servohydraulic actuator adaptive compensation for real-time hybrid simulation / Cheng Chen in Journal of structural engineering, Vol. 136 N° 4 (Avril 2010) 

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