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Total 31 records

    Nonlinear tracking control of a microbeam displacement by electrostatic actuation

    , Article World Academy of Science, Engineering and Technology ; Volume 79 , July , 2011 , Pages 232-236 ; ISSN: 2010376X Karami, F ; Layeghi, H ; Salarieh, H ; Alasti, A ; Sharif University of Technology
    Abstract
    In this study tracking problem of tip of a micro cantilever, actuated by electrostatic, is investigated. Dynamic model of the system is a PDE. Using electrostatic actuation.introduced significant nonlinearity in dynamic model of the system. Control goals are achieved by means of backstepping for SI and feedback linearization for MI system. Performance of control system is inspected for some assumptions and simplifications. The results are in according to numerical simulations  

    Closed form solutions for the motion of electrically excited micro-cantilever beams

    , Article 2006 ASME International Mechanical Engineering Congress and Exposition, IMECE2006, Chicago, IL, 5 November 2006 through 10 November 2006 ; 2006 ; 1096665X (ISSN); 0791837904 (ISBN); 9780791837900 (ISBN) Ghaemi Oskouei, S. B ; Ahmadian, M. T ; Sharif University of Technology
    American Society of Mechanical Engineers (ASME)  2006
    Abstract
    The differential equation governing the motion of an electrically excited capacitive microcantilever beam is a nonlinear PDE [1]. Accurate analysis about its motion is of great importance in MEMS' dynamical response. In this paper first the nonlinear 4th order 2 point boundary value problem (ODE) governing the static deflection of the system is solved using three methods. 1. The nonlinear part is linearized and its exact solution is obtained. 2. For low applied DC voltages (not near pull-in) the solutin is found using the direct straight forward perturbation analysis. 3. Numerical computer solutions which are used for the previous solution's verifications. The next parts are devoted to the... 

    Effects of the electric field configuration's variation due to micro-cantilever beam's curvature on pull-in phenomenon

    , Article 2006 ASME International Mechanical Engineering Congress and Exposition, IMECE2006, Chicago, IL, 5 November 2006 through 10 November 2006 ; 2006 ; 1096665X (ISSN); 0791837904 (ISBN); 9780791837900 (ISBN) Ghaemi Oskouei, S. B ; Ahmadian, M. T ; Sharif University of Technology
    American Society of Mechanical Engineers (ASME)  2006
    Abstract
    Micro-electromechanical systems (MEMS) have wide application in the development of sensors for the detection of magnitudes in almost any domain [1]. Resonant mode operation of micro and nano-scale oscillators have gained wide interest for applications including filters, amplifiers, non-linear mixers, atomic scale imaging, biological and chemical sensors. The device that we propose is an electrically actuated microcantilever beam. More precisely, in our design the microcantilever constitutes the movable plate of a micro-capacitor and its displacement is controlled by the voltage applied across the plates. Review of literature shows that the electric field pattern between the beam and the... 

    Static deflection and pull-in instability analysis of an electrostatically actuated mirocantilever gyroscope considering geometric nonlinearities

    , Article Journal of Mechanical Science and Technology ; Volume 27, Issue 8 , 2013 , Pages 2425-2434 ; 1738494X (ISSN) Mojahedi, M ; Ahmadian, M. T ; Firoozbakhsh, K ; Sharif University of Technology
    2013
    Abstract
    In this paper, a mathematical modeling of a microcantilever gyroscope is presented considering the nonlinearities of the system due to electrostatic forces, fringing field, geometry and the inertial terms. The microgyroscope is actuated and detected by electrostatic methods and subjected to coupled bending oscillations. First a system of two nonlinear integro-differential equations is derived which describes flexural-flexural motion of electrostatically actuated and detected microbeam gyroscopes. Afterward, static deflection and pull-in instability of the microgyroscopes acted upon by DC voltages in both (driving and sensing) directions are studied for different parameters. The model's... 

    Static pull-in analysis of micro-cantilevers in wet etching fabrication process

    , Article ASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE), 9 November 2012 through 15 November 2012 ; Volume 9, Issue PARTS A AND B , November , 2012 , Pages 347-350 ; 9780791845257 (ISBN) Darvishian, A ; Moeenfard, H ; Ahmadian, M. T ; Sharif University of Technology
    2012
    Abstract
    Parallel micro actuators are mostly fabricated using the wet etching process within which the presence of capillary force and the resulting pull-in instabilities can severely affect the success of the fabrication process. In the case the capillary force is large enough then the beam like structure of the micro actuators is collapsed. The current paper investigates; static behavior of microcantilevers under effect of capillary force. It is observed that with increasing the instability number defined in the paper, the deflection of the micro-cantilevers is increased. This study shows in the wet etching fabrication process, if the distance between the beam and substrate is small enough, the... 

    Resonant frequency and sensitivity of an AFM microcantilever modeled by the non-local theory

    , Article ASME 2011 International Mechanical Engineering Congress and Exposition, IMECE 2011, 11 November 2011 through 17 November 2011 ; Volume 11 , November , 2011 , Pages 239-245 ; 9780791854976 (ISBN) Khosravani, E ; Kahrobaiyan, M. H ; Ahmadian, M. T ; Sharif University of Technology
    Abstract
    In this paper, utilizing the non-local theory, the resonant frequency and sensitivity of an AFM microcantilever are investigated. To that end, the governing equation of motion and corresponding boundary conditions are obtained using the variational approach. Afterwards, the resonant frequency and sensitivity of the AFM microcantilever are derived analytically and depicted in some figures versus the contact stiffness of the sampling surface. The results of the current model are compared to those of the classical theory. The comparison shows that the difference between the results of the non-local theory and those of the classical theory is significant when the non-local parameter is high but... 

    A size-dependent beam element based on the modified couple stress theory

    , Article ASME 2011 International Mechanical Engineering Congress and Exposition, IMECE 2011, 11 November 2011 through 17 November 2011, Denver, CO ; Volume 8 , 2011 , Pages 591-597 ; 9780791854945 (ISBN) Kahrobaiyan, M. H ; Khajehpour, M ; Ahmadian, M. T ; ASME ; Sharif University of Technology
    Abstract
    In this paper, the modified couple stress theory is employed to develop a size-dependent beam element able to predict the size-dependency observed in microbeams. The stiffness matrix is obtained for the aforementioned beam element. As an example, the deflection of a microcantilever is evaluated using the proposed beam elements and the results of the finite element method are compared to the analytical results obtained by the classical beam theory. The maximum deflection of the beam is depicted versus the ratio of the beam thickness to the material length scale parameter, the parameter appearing in non-classical continuum theories. The results show that when the characteristic size of the... 

    Nonlinear vibration analysis of a micro beam exposed to an external flow

    , Article ASME 2011 International Mechanical Engineering Congress and Exposition, IMECE 2011 ; Volume 7, Issue PARTS A AND B , 2011 , Pages 643-646 ; 9780791854938 (ISBN) Mazaheri, H ; Hosseinzadeh, A ; Ahmadian, M. T ; Barari, A ; Sharif University of Technology
    2011
    Abstract
    In this paper, nonlinear vibration of a micro cantilever exposed to a constant velocity flow is studied. In order to obtain vibration frequency and time response of the micro beam the variational iteration method is used as a novel tool for solving nonlinear differential equations. Results of the analytical solution are compared with those obtained by Runge-Kutta method which shows very good agreement between them. Results confirm that frequency of vibration depends on the flow velocity. Also, the high sensitivity of the vibration frequency to the flow velocity means that it can be an effective indicator of velocity  

    Static pull-in analysis of microcantilevers based on the modified couple stress theory

    , Article Sensors and Actuators, A: Physical ; Volume 171, Issue 2 , 2011 , Pages 370-374 ; 09244247 (ISSN) Rahaeifard, M ; Kahrobaiyan, M. H ; Asghari, M ; Ahmadian, M. T ; Sharif University of Technology
    2011
    Abstract
    This paper investigates the deflection and static pull-in voltage of microcantilevers based on the modified couple stress theory, a non-classic continuum theory capable to predict the size effects for structures in micron and sub-micron scales. It is shown that the couple stress theory can remove the gap between the experimental observations and the classical theory based simulations for the static pull-in voltage  

    Nonlinear tracking control of a microbeam displacement by electrostatic actuation

    , Article World Academy of Science, Engineering and Technology ; Volume 79 , 2011 , Pages 232-236 ; 2010376X (ISSN) Karami, F ; Layeghi, H ; Salarieh, H ; Alasti, A ; Sharif University of Technology
    2011
    Abstract
    In this study tracking problem of tip of a micro cantilever, actuated by electrostatic, is investigated. Dynamic model of the system is a PDE. Using electrostatic actuation introduced significant nonlinearity in dynamic model of the system. Control goals are achieved by means of backstepping for SI and feedback linearization for MI system. Performance of control system is inspected for some assumptions and simplifications. The results are in according to numerical simulations  

    Simulation of imaging in tapping-mode atomic-force microscopy: A comparison amongst a variety of approaches

    , Article Journal of Physics D: Applied Physics ; Volume 44, Issue 7 , February , 2011 ; 00223727 (ISSN) Pishkenari, H. N ; Mahboobi, S. H ; Meghdari, A ; Sharif University of Technology
    2011
    Abstract
    Models capable of accurate simulation of microcantilever dynamics coupled with complex tip-sample interactions are essential for interpretation and prediction of the imaging results in amplitude modulation or tapping-mode atomic-force microscopy (AM-AFM or TM-AFM). In this paper, four approaches based on combinations of lumped and finite element methods for modelling of cantilever dynamics, and van derWaals and molecular dynamics for modelling of tip-sample interactions, are used to simulate the precise imaging by AM-AFM. Based on the simulated imaging and force determination, the efficiency of different modelling schemes is evaluated. This comparison is performed considering their... 

    Investigation of the size-dependent dynamic characteristics of atomic force microscope microcantilevers based on the modified couple stress theory

    , Article International Journal of Engineering Science ; Volume 48, Issue 12 , 2010 , Pages 1985-1994 ; 00207225 (ISSN) Kahrobaiyan, M. H ; Asghari, M ; Rahaeifard, M ; Ahmadian, M. T ; Sharif University of Technology
    Abstract
    In this paper, the resonant frequency and sensitivity of atomic force microscope (AFM) microcantilevers are studied using the modified couple stress theory. The classical continuum mechanics is incapable of interpreting micro-structure-dependent size effects when the size of structures is in micron- and sub-micron scales. However, this dependency can be well treated by using non-classical continuum theories. The modified couple stress theory is a non-classic continuum theory which employs additional material parameters besides those appearing in classical continuum theory to treat the size-dependent behavior. In this work, writing differential equations of motion of AFM cantilevers together... 

    Analytical and experimental frequency response analysis of microcantilevers subject to tip-sample interaction

    , Article Proceedings of the ASME International Design Engineering Technical Conferences and Computers and Information in Engineering Conference 2009, DETC2009, 30 August 2009 through 2 September 2009 ; Volume 6 , September , 2010 , Pages 575-581 ; 9780791849033 (ISBN) Delnavaz, A ; Mahmoodi, S. N ; Jalili, N ; Zohoor, H ; Sharif University of Technology
    Abstract
    Improvement of microcantilever-based sensors and actuators chiefly depends on how comprehensively they are modeled and precisely formulated. Atomic Force Microscopy (AFM) is the most widespread application of microcantilever beam as a sensor, which is usually influenced by the tip-sample interaction force. For this, vibration of AFM microcantilever probe is analyzed in this paper, along with analytical, numerical and experimental investigation of the influence of the sample interaction force on the microcantilever vibration. Nonlinear integro-partial equation of microcantilever vibration subject to the tip-sample interaction is then derived and numerically simulated. Moreover, multiple time... 

    Designing nonlinear observer for topography estimation in trolling mode atomic force microscopy

    , Article JVC/Journal of Vibration and Control ; 2021 ; 10775463 (ISSN) Sajjadi, M ; Chahari, M ; Pishkenari, H. N ; Vossoughi, G ; Sharif University of Technology
    SAGE Publications Inc  2021
    Abstract
    In this study, a nonlinear observer for high-speed estimation of the sample surface topography in a small duration of the probe transient motion utilizing a 2DOF model of TR-AFM is proposed. Since the time duration to reach the steady-state periodic motion of the oscillating probe in conventional imaging methods is relatively high, the proposed nonlinear observer in this research is able to address this limitation and estimate the surface topography throughout transient oscillation of the microcantilever. With this aim, topography estimation process utilizing a Thau observer without any linearization of the system dynamics is designed and coupled with the system dynamics to achieve sample... 

    Real-time topography and hamaker constant estimation in atomic force microscopy based on adaptive fading extended kalman filter

    , Article International Journal of Control, Automation and Systems ; Volume 19, Issue 7 , 2021 , Pages 2455-2467 ; 15986446 (ISSN) Haghighi, M.S ; Nejat Pishkenari, H ; Sharif University of Technology
    Institute of Control, Robotics and Systems  2021
    Abstract
    In this study, a novel technique based on adaptive fading extended Kalman filter for atomic force microscopy is proposed to directly estimate the topography of a sample surface without needing any control system. While in conventional imaging techniques, the scanning speed or the bandwidth is limited due to a relatively large settling time, the method proposed in this research is able to address this issue and estimate the topography throughout transient oscillation of the microcantilever. With this aim, an estimation process using an adaptive fading extended Kalman filter (augmented with forgetting factor) as the system observer is designed and coupled with the system dynamics to obtain... 

    Design of an effective piezoelectric microcantilever biosensor for rapid detection of COVID-19

    , Article Journal of Medical Engineering and Technology ; Volume 45, Issue 6 , 2021 , Pages 423-433 ; 03091902 (ISSN) Kabir, H ; Merati, M ; Abdekhodaie, M. J ; Sharif University of Technology
    Taylor and Francis Ltd  2021
    Abstract
    Acute respiratory syndrome coronavirus 2 (SARS-CoV-2), also called COVID-19, is one of the most contagious viruses resulting in a progressive pandemic. Since specific antiviral treatments have not been developed yet and its fatal rate is almost high, early and fast detection is critical for controlling the outbreak. In this study, a piezoelectric microcantilever biosensor has been designed for detecting COVID-19 samples directly without requiring preparation steps. The biosensor acts as a transducer and is coated with the related antibody. When the SARS-CoV-2 antigens adsorbed on the microcantilever top surface through their spike proteins, a surface stress due to the mass change would be... 

    Size-dependent dynamic behavior of microcantilevers under suddenly applied DC voltage

    , Article Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science ; Vol. 228, Issue. 5 , May , 2014 , pp. 896-906 ; ISSN: 09544062 Rahaeifard, M ; Ahmadian, M. T ; Firoozbakhsh, K ; Sharif University of Technology
    Abstract
    This paper investigates the dynamic behavior of microcantilevers under suddenly applied DC voltage based on the modified couple stress theory. The cantilever is modeled based on the Euler-Bernoulli beam theory and equation of motion is derived using Hamilton's principle. Both analytical and numerical methods are utilized to predict the dynamic behavior of the microbeam. Multiple scales method is used for analytical analysis and the numerical approach is based on a hybrid finite element/finite difference method. The results of the modified couple stress theory are compared with those from the literature as well as the results predicted by the classical theory. It is shown that the modified... 

    Analytical study on size-dependent static pull-in voltage of microcantilevers using the modified couple stress theory

    , Article International Journal of Engineering Science ; Volume 54 , May , 2012 , Pages 99-105 ; 00207225 (ISSN) Baghani, M ; Sharif University of Technology
    2012
    Abstract
    In this paper an analytical solution for size-dependent response of cantilever micro-beams is presented. Using the modified couple stress theory, the small scale effects are accounted for. Employing the Modified Variational Iteration Method, efficient and accurate analytical expressions for the deflection of the micro-beam are presented. Very good agreement is observed between the present work results and available experimental data. This study may be helpful to characterize the size-dependent mechanical properties of MEMS. Consequently, the proposed analytical solution can be used as an efficient tool for studying the effects of the material or geometrical parameters on small scale devices... 

    Hybrid finite-element method-molecular dynamics approach for modelling of non-contact atomic force microscopy imaging

    , Article Micro and Nano Letters ; Volume 6, Issue 6 , June , 2011 , Pages 412-416 ; 17500443 (ISSN) Pishkenari, H. N ; Mahboobi, S. H ; Meghdari, A ; Sharif University of Technology
    2011
    Abstract
    Models capable of accurate simulation of the microcantilever dynamics coupled with complex tip-sample interactions are essential for interpretation of the imaging results in non-contact atomic force microscopy (AFM). In the present research, a combination of finite element and molecular dynamics methods are used for modelling the AFM system to overcome the drawbacks of conventional approaches that use a lumped system with van der Waals interaction. To illustrate the ability of the proposed scheme in providing images with atomic resolution, some simulations have been performed. In the conducted simulations, a diamond tip is interacting with nickel samples having different surface plane... 

    Flexural sensitivity of a V-shaped AFM cantilever made of functionally graded materials

    , Article ASME 2010 10th Biennial Conference on Engineering Systems Design and Analysis, ESDA2010, 12 July 2010 through 14 July 2010 ; Volume 1 , 2010 , Pages 495-501 ; 9780791849156 (ISBN) Rahaeifard, M ; Kahrobaiyan, M. H ; Moeini, S. A ; Ahmadian, M. T ; Hoviattalab, M ; Sharif University of Technology
    Abstract
    In this paper, two lowest resonant frequencies and sensitivities of an AFM V-Shaped microcantilever made of functionally graded materials are studied. The beam is modeled by Euler-Bernoulli beam theory in which rotary inertia and shear deformation is neglected. It is assumed that the beam is made of a mixture of metal and ceramic with properties varying through the thickness of the beam. This variation is function of volume fraction of beam material constituents. The interaction between AFM tip and surface is modeled by two linear springs which expresses the normal and lateral contact stiffness. A relationship is developed to evaluate the sensitivity of FGM micro cantilever beam. Effect of...