Documents disponibles écrits par cet auteur

Catcher bearing life prediction using a rainflow counting approach / Jung Gu Lee in Transactions of the ASME . Journal of tribology, Vol. 134 N° 3 (Juillet 2012) 

Public ISBD [article]  in Transactions of the ASME . Journal of tribology > Vol. 134 N° 3 (Juillet 2012) . - 15 p. Titre : Catcher bearing life prediction using a rainflow counting approach Type de document : texte imprimé Auteurs : Jung Gu Lee, Auteur ; Palazzolo, Alan, Auteur Année de publication : 2012 Article en page(s) : 15 p. Note générale : tribology Langues : Anglais (eng) Mots-clés : rotating  machine;  Catcher  bearings;  fatigue  life;  rainflow  counting  algorithm Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : Catcher bearings (CB) are an essential component for rotating machine with active magnetic bearings (AMBs) suspensions. The CB's role is to protect the magnetic bearing and other close clearance component in the event of an AMB failure. The contact load, the Hertzian stress, and the sub/surface shear stress between rotor, races, and balls are calculated, using a nonlinear ball bearing model with thermal growth, during the rotor drop event. Fatigue life of the CB in terms of the number of drop occurrences prior to failure is calculated by applying the Rainflow Counting Algorithm to the sub/surface shear stress-time history. Numerical simulations including high fidelity bearing models and a Timoshenko beam finite element rotor model show that CB life is dramatically reduced when high-speed backward whirl occurs. The life of the CB is seen to be extended by reducing the CB clearances, by applying static side-loads to the rotor during the drop occurrence, by reducing the drop speed, by reducing the support stiffness and increasing the support damping and by reducing the rotor (journal)—bearing contact friction. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://www.asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013400 [...] [article] Catcher bearing life prediction using a rainflow counting approach [texte imprimé] / Jung Gu Lee, Auteur ; Palazzolo, Alan, Auteur . - 2012 . - 15 p. tribology Langues : Anglais (eng) in Transactions of the ASME . Journal of tribology > Vol. 134 N° 3 (Juillet 2012) . - 15 p. Mots-clés : rotating  machine;  Catcher  bearings;  fatigue  life;  rainflow  counting  algorithm Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : Catcher bearings (CB) are an essential component for rotating machine with active magnetic bearings (AMBs) suspensions. The CB's role is to protect the magnetic bearing and other close clearance component in the event of an AMB failure. The contact load, the Hertzian stress, and the sub/surface shear stress between rotor, races, and balls are calculated, using a nonlinear ball bearing model with thermal growth, during the rotor drop event. Fatigue life of the CB in terms of the number of drop occurrences prior to failure is calculated by applying the Rainflow Counting Algorithm to the sub/surface shear stress-time history. Numerical simulations including high fidelity bearing models and a Timoshenko beam finite element rotor model show that CB life is dramatically reduced when high-speed backward whirl occurs. The life of the CB is seen to be extended by reducing the CB clearances, by applying static side-loads to the rotor during the drop occurrence, by reducing the drop speed, by reducing the support stiffness and increasing the support damping and by reducing the rotor (journal)—bearing contact friction. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://www.asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013400 [...]

Magnetically suspended VSCMGs for simultaneous attitude control and power transfer IPAC service / Park, Junyoung in Transactions of the ASME . Journal of dynamic systems, measurement, and control, Vol. 132 N° 5 (Septembre 2010) 

Public ISBD [article]  in Transactions of the ASME . Journal of dynamic systems, measurement, and control > Vol. 132 N° 5 (Septembre 2010) . - 15 p. Titre : Magnetically suspended VSCMGs for simultaneous attitude control and power transfer IPAC service Type de document : texte imprimé Auteurs : Park, Junyoung, Auteur ; Palazzolo, Alan, Auteur Année de publication : 2010 Article en page(s) : 15 p. Note générale : Systèmes dynamiques Langues : Anglais (eng) Mots-clés : Artificial  satellites  Attitude  control  Gyroscopes  Velocity  control  Vibrations  Wheels Index. décimale : 629.8 Résumé : This paper presents the theory and numerical results of utilizing four gimbaled, magnetically suspended, variable speed flywheels for simultaneous satellite attitude control and power transfer (charge, storage, and delivery). Previous variable speed control moment gyro models and control algorithms assumed that the flywheel bearings were rigid. However, high speed flywheels on spacecraft will be supported by active magnetic bearings, which have flexibility and in general frequency dependent characteristics. The present work provides the theory for modeling the satellite and flywheel systems including controllers for stable magnetic bearing suspension for power transfer to and from the flywheels and for attitude control of the satellite. A major reason for utilizing flexible bearings is to isolate the imbalance disturbance forces from the flywheel to the satellite. This g-jitter vibration could interfere with the operation of sensitive onboard instrumentation. A special control approach is employed for the magnetic bearings to reject the imbalance disturbances. The stability, robustness, tracking, and disturbance rejection performances of the feedback control laws are demonstrated with a satellite simulation that includes initial attitude error, system modeling error, and flywheel imbalance disturbance. DEWEY : 629.8 ISSN : 0022-0434 En ligne : http://asmedl.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JDSMAA00013200 [...] [article] Magnetically suspended VSCMGs for simultaneous attitude control and power transfer IPAC service [texte imprimé] / Park, Junyoung, Auteur ; Palazzolo, Alan, Auteur . - 2010 . - 15 p. Systèmes dynamiques Langues : Anglais (eng) in Transactions of the ASME . Journal of dynamic systems, measurement, and control > Vol. 132 N° 5 (Septembre 2010) . - 15 p. Mots-clés : Artificial  satellites  Attitude  control  Gyroscopes  Velocity  control  Vibrations  Wheels Index. décimale : 629.8 Résumé : This paper presents the theory and numerical results of utilizing four gimbaled, magnetically suspended, variable speed flywheels for simultaneous satellite attitude control and power transfer (charge, storage, and delivery). Previous variable speed control moment gyro models and control algorithms assumed that the flywheel bearings were rigid. However, high speed flywheels on spacecraft will be supported by active magnetic bearings, which have flexibility and in general frequency dependent characteristics. The present work provides the theory for modeling the satellite and flywheel systems including controllers for stable magnetic bearing suspension for power transfer to and from the flywheels and for attitude control of the satellite. A major reason for utilizing flexible bearings is to isolate the imbalance disturbance forces from the flywheel to the satellite. This g-jitter vibration could interfere with the operation of sensitive onboard instrumentation. A special control approach is employed for the magnetic bearings to reject the imbalance disturbances. The stability, robustness, tracking, and disturbance rejection performances of the feedback control laws are demonstrated with a satellite simulation that includes initial attitude error, system modeling error, and flywheel imbalance disturbance. DEWEY : 629.8 ISSN : 0022-0434 En ligne : http://asmedl.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JDSMAA00013200 [...]

MIMO active vibration control of magnetically suspended flywheels for satellite IPAC service / Park, Junyoung in Transactions of the ASME . Journal of dynamic systems, measurement, and control, Vol. 130 n°4 (Juillet 2008) 

Public ISBD [article]  in Transactions of the ASME . Journal of dynamic systems, measurement, and control > Vol. 130 n°4 (Juillet 2008) . - 22 p. Titre : MIMO active vibration control of magnetically suspended flywheels for satellite IPAC service Type de document : texte imprimé Auteurs : Park, Junyoung, Auteur ; Raymond Beach, Auteur ; Palazzolo, Alan, Auteur Année de publication : 2008 Article en page(s) : 22 p. Note générale : dynamic systems Langues : Anglais (eng) Mots-clés : force;  motion;  flywheels;  satellites Résumé : Theory and simulation results have demonstrated that four, variable speed flywheels could potentially provide the energy storage and attitude control functions of existing batteries and control moment gyros on a satellite. Past modeling and control algorithms were based on the assumption of rigidity in the flywheel’s bearings and the satellite structure. This paper provides simulation results and theory, which eliminates this assumption utilizing control algorithms for active vibration control (AVC), flywheel shaft levitation, and integrated power transfer and attitude control (IPAC), that are effective even with low stiffness active magnetic bearings (AMBs) and flexible satellite appendages. The flywheel AVC and levitation tasks are provided by a multiple input–multiple output control law that enhances stability by reducing the dependence of the forward and backward gyroscopic poles with changes in flywheel speed. The control law is shown to be effective even for (1) large polar to transverse inertia ratios, which increases the stored energy density while causing the poles to become more speed dependent, and for (2) low bandwidth controllers shaped to suppress high frequency noise. Passive vibration dampers are designed to reduce the vibrations of flexible appendages of the satellite. Notch, low-pass, and bandpass filters are implemented in the AMB system to reduce and cancel high frequency, dynamic bearing forces and motor torques due to flywheel mass imbalance. Successful IPAC simulation results are presented with a 12% initial attitude error, large polar to transverse inertia ratio (IP∕IT), structural flexibility, and unbalance mass disturbance. En ligne : http://dynamicsystems.asmedigitalcollection.asme.org/issue.aspx?journalid=117&is [...] [article] MIMO active vibration control of magnetically suspended flywheels for satellite IPAC service [texte imprimé] / Park, Junyoung, Auteur ; Raymond Beach, Auteur ; Palazzolo, Alan, Auteur . - 2008 . - 22 p. dynamic systems Langues : Anglais (eng) in Transactions of the ASME . Journal of dynamic systems, measurement, and control > Vol. 130 n°4 (Juillet 2008) . - 22 p. Mots-clés : force;  motion;  flywheels;  satellites Résumé : Theory and simulation results have demonstrated that four, variable speed flywheels could potentially provide the energy storage and attitude control functions of existing batteries and control moment gyros on a satellite. Past modeling and control algorithms were based on the assumption of rigidity in the flywheel’s bearings and the satellite structure. This paper provides simulation results and theory, which eliminates this assumption utilizing control algorithms for active vibration control (AVC), flywheel shaft levitation, and integrated power transfer and attitude control (IPAC), that are effective even with low stiffness active magnetic bearings (AMBs) and flexible satellite appendages. The flywheel AVC and levitation tasks are provided by a multiple input–multiple output control law that enhances stability by reducing the dependence of the forward and backward gyroscopic poles with changes in flywheel speed. The control law is shown to be effective even for (1) large polar to transverse inertia ratios, which increases the stored energy density while causing the poles to become more speed dependent, and for (2) low bandwidth controllers shaped to suppress high frequency noise. Passive vibration dampers are designed to reduce the vibrations of flexible appendages of the satellite. Notch, low-pass, and bandpass filters are implemented in the AMB system to reduce and cancel high frequency, dynamic bearing forces and motor torques due to flywheel mass imbalance. Successful IPAC simulation results are presented with a 12% initial attitude error, large polar to transverse inertia ratio (IP∕IT), structural flexibility, and unbalance mass disturbance. En ligne : http://dynamicsystems.asmedigitalcollection.asme.org/issue.aspx?journalid=117&is [...]