Documents disponibles écrits par cet auteur

Characterization of the dynamical response of a micromachined G-sensor to mechanical shock loading / Daniel Jordy 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) . - 9 p. Titre : Characterization of the dynamical response of a micromachined G-sensor to mechanical shock loading Type de document : texte imprimé Auteurs : Daniel Jordy, Auteur ; Younis, Mohammad I., Auteur Année de publication : 2008 Article en page(s) : 9 p. Note générale : dynamic systems Langues : Anglais (eng) Mots-clés : sensors;  shock  (mechanics);  damping;  microelectromechanical  systems;  stiction;  motion Résumé : Squeeze film damping has a significant effect on the dynamic response of microelectromechanical system (MEMS) devices that employ perforated microstructures with large planar areas and small gap widths separating them from the substrate. Perforations can alter the effect of squeeze film damping by allowing the gas underneath the device to easily escape, thereby lowering damping. By decreasing the size of the holes, damping increases and the squeeze film damping effect increases. This can be used to minimize the out-of-plane motion of the microstructures toward the substrate, thereby minimizing the possibility of contact and stiction. This paper aims to explore the use of the squeeze film damping phenomenon as a way to mitigate shock and minimize the possibility of stiction and failure in this class of MEMS devices. As a case study, the performance of a G-sensor (threshold accelerometer) employed in an arming and fusing chip is investigated. The effect of changing the size of the perforation holes and the gap width separating the microstructure from the substrate are studied. A multiphysics finite-element model built using the software ANSYS is utilized for the fluidic and transient structural analysis. A squeeze film damping model, for both the air underneath the structure and the flow of the air through the perforations, is developed. Results are shown for various models of squeeze film damping assuming no holes, large holes, and assuming a finite pressure drop across the holes, which is the most accurate way of modeling. It is found that the threshold of shock that causes the G-sensor to contact the substrate has increased significantly when decreasing the holes size or the gap width, which is very promising to help mitigate stiction in this class of devices, thereby improving their reliability. En ligne : http://dynamicsystems.asmedigitalcollection.asme.org/issue.aspx?journalid=117&is [...] [article] Characterization of the dynamical response of a micromachined G-sensor to mechanical shock loading [texte imprimé] / Daniel Jordy, Auteur ; Younis, Mohammad I., Auteur . - 2008 . - 9 p. dynamic systems Langues : Anglais (eng) in Transactions of the ASME . Journal of dynamic systems, measurement, and control > Vol. 130 n°4 (Juillet 2008) . - 9 p. Mots-clés : sensors;  shock  (mechanics);  damping;  microelectromechanical  systems;  stiction;  motion Résumé : Squeeze film damping has a significant effect on the dynamic response of microelectromechanical system (MEMS) devices that employ perforated microstructures with large planar areas and small gap widths separating them from the substrate. Perforations can alter the effect of squeeze film damping by allowing the gas underneath the device to easily escape, thereby lowering damping. By decreasing the size of the holes, damping increases and the squeeze film damping effect increases. This can be used to minimize the out-of-plane motion of the microstructures toward the substrate, thereby minimizing the possibility of contact and stiction. This paper aims to explore the use of the squeeze film damping phenomenon as a way to mitigate shock and minimize the possibility of stiction and failure in this class of MEMS devices. As a case study, the performance of a G-sensor (threshold accelerometer) employed in an arming and fusing chip is investigated. The effect of changing the size of the perforation holes and the gap width separating the microstructure from the substrate are studied. A multiphysics finite-element model built using the software ANSYS is utilized for the fluidic and transient structural analysis. A squeeze film damping model, for both the air underneath the structure and the flow of the air through the perforations, is developed. Results are shown for various models of squeeze film damping assuming no holes, large holes, and assuming a finite pressure drop across the holes, which is the most accurate way of modeling. It is found that the threshold of shock that causes the G-sensor to contact the substrate has increased significantly when decreasing the holes size or the gap width, which is very promising to help mitigate stiction in this class of devices, thereby improving their reliability. En ligne : http://dynamicsystems.asmedigitalcollection.asme.org/issue.aspx?journalid=117&is [...]

Integrity analysis of electrically actuated resonators with delayed feedback controller / Alsaleem, Fadi in Transactions of the ASME . Journal of dynamic systems, measurement, and control, Vol. 133 N° 3 (Mai 2011) 

Public ISBD [article]  in Transactions of the ASME . Journal of dynamic systems, measurement, and control > Vol. 133 N° 3 (Mai 2011) . - 08 p. Titre : Integrity analysis of electrically actuated resonators with delayed feedback controller Type de document : texte imprimé Auteurs : Alsaleem, Fadi, Auteur ; Younis, Mohammad I., Auteur Année de publication : 2011 Article en page(s) : 08 p. Note générale : Systèmes dynamiques Langues : Anglais (eng) Mots-clés : Delays  Feedback  Micromechanical  resonators Index. décimale : 629.8 Résumé : In this work, we investigate the stability and integrity of parallel-plate microelectromechanical systems resonators using a delayed feedback controller. Two case studies are investigated: a capacitive sensor made of cantilever beams with a proof mass at their tip and a clamped-clamped microbeam. Dover-cliff integrity curves and basin-of-attraction analysis are used for the stability assessment of the frequency response of the resonators for several scenarios of positive and negative gain in the controller. It is found that in the case of a positive gain, a velocity or a displacement feedback controller can be used to effectively enhance the stability of the resonators. This is confirmed by an increase in the area of the basin of attraction of the resonator and in shifting the Dover-cliff curve to higher values. On the other hand, it is shown that a negative gain can significantly weaken the stability and integrity of the resonators. This can be of useful use in MEMS for actuation applications, such as in the case of capacitive switches, to lower the activation voltage of these devices and to ensure their trigger under all initial conditions. DEWEY : 629.8 ISSN : 0022-0434 En ligne : http://asmedl.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JDSMAA00013300 [...] [article] Integrity analysis of electrically actuated resonators with delayed feedback controller [texte imprimé] / Alsaleem, Fadi, Auteur ; Younis, Mohammad I., Auteur . - 2011 . - 08 p. Systèmes dynamiques Langues : Anglais (eng) in Transactions of the ASME . Journal of dynamic systems, measurement, and control > Vol. 133 N° 3 (Mai 2011) . - 08 p. Mots-clés : Delays  Feedback  Micromechanical  resonators Index. décimale : 629.8 Résumé : In this work, we investigate the stability and integrity of parallel-plate microelectromechanical systems resonators using a delayed feedback controller. Two case studies are investigated: a capacitive sensor made of cantilever beams with a proof mass at their tip and a clamped-clamped microbeam. Dover-cliff integrity curves and basin-of-attraction analysis are used for the stability assessment of the frequency response of the resonators for several scenarios of positive and negative gain in the controller. It is found that in the case of a positive gain, a velocity or a displacement feedback controller can be used to effectively enhance the stability of the resonators. This is confirmed by an increase in the area of the basin of attraction of the resonator and in shifting the Dover-cliff curve to higher values. On the other hand, it is shown that a negative gain can significantly weaken the stability and integrity of the resonators. This can be of useful use in MEMS for actuation applications, such as in the case of capacitive switches, to lower the activation voltage of these devices and to ensure their trigger under all initial conditions. DEWEY : 629.8 ISSN : 0022-0434 En ligne : http://asmedl.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JDSMAA00013300 [...]

The effect of squeeze-film damping on the shock response of clamped-clamped microbeams / Hadi Yagubizade in Transactions of the ASME . Journal of dynamic systems, measurement, and control, Vol. 134 N° 1 (Janvier 2012) 

Public ISBD [article]  in Transactions of the ASME . Journal of dynamic systems, measurement, and control > Vol. 134 N° 1 (Janvier 2012) . - 07 p. Titre : The effect of squeeze-film damping on the shock response of clamped-clamped microbeams Type de document : texte imprimé Auteurs : Hadi Yagubizade, Auteur ; Younis, Mohammad I., Auteur Année de publication : 2012 Article en page(s) : 07 p. Note générale : Dynamic systems Langues : Anglais (eng) Mots-clés : Beams  (structures)  Clamps  Damping  Finite  difference  methods  Finite  element  analysis  Galerkin  method  Impact  (mechanical)  Micromechanical  devices Index. décimale : 553 Géologie économique. Minérographie. Minéraux. Formation et gisements de minerais Résumé : This paper presents an investigation into the nonlinear effect of squeeze-film damping on the response of a clamped–clamped microbeam to mechanical shock. In this work, we solve simultaneously the nonlinear Reynolds equation, to model squeeze-film damping, coupled with a nonlinear Euler–Bernoulli beam equation. A Galerkin-based reduced-order model and a finite-difference method are utilized for the solid domain and fluid domain, respectively. Several results demonstrating the effect of gas pressure on the response of the microbeams are shown. Comparison with the results of a fully coupled multiphysics nonlinear finite-element model is presented. The results indicate that, for devices operating in air, squeeze-film damping can be used effectively to minimize the displacements of released microstructures during shock and impact. The results also indicate that squeeze-film damping has more significant effect on the response of microstructures in the dynamic shock regime compared to the quasi-static shock regime. A computationally efficient approach is proposed to model the fluidic-structural problem more efficiently based on a nonlinear analytical expression of the squeeze-film damping. DEWEY : 553 ISSN : 0022-0434 En ligne : http://www.asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JDSMAA00013400 [...] [article] The effect of squeeze-film damping on the shock response of clamped-clamped microbeams [texte imprimé] / Hadi Yagubizade, Auteur ; Younis, Mohammad I., Auteur . - 2012 . - 07 p. Dynamic systems Langues : Anglais (eng) in Transactions of the ASME . Journal of dynamic systems, measurement, and control > Vol. 134 N° 1 (Janvier 2012) . - 07 p. Mots-clés : Beams  (structures)  Clamps  Damping  Finite  difference  methods  Finite  element  analysis  Galerkin  method  Impact  (mechanical)  Micromechanical  devices Index. décimale : 553 Géologie économique. Minérographie. Minéraux. Formation et gisements de minerais Résumé : This paper presents an investigation into the nonlinear effect of squeeze-film damping on the response of a clamped–clamped microbeam to mechanical shock. In this work, we solve simultaneously the nonlinear Reynolds equation, to model squeeze-film damping, coupled with a nonlinear Euler–Bernoulli beam equation. A Galerkin-based reduced-order model and a finite-difference method are utilized for the solid domain and fluid domain, respectively. Several results demonstrating the effect of gas pressure on the response of the microbeams are shown. Comparison with the results of a fully coupled multiphysics nonlinear finite-element model is presented. The results indicate that, for devices operating in air, squeeze-film damping can be used effectively to minimize the displacements of released microstructures during shock and impact. The results also indicate that squeeze-film damping has more significant effect on the response of microstructures in the dynamic shock regime compared to the quasi-static shock regime. A computationally efficient approach is proposed to model the fluidic-structural problem more efficiently based on a nonlinear analytical expression of the squeeze-film damping. DEWEY : 553 ISSN : 0022-0434 En ligne : http://www.asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JDSMAA00013400 [...]