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Total 410 records

    Conceptual design of a micro gripper with electrostatic micro stepper-motor actuation

    , Article Life Science Journal ; Volume 10, Issue SUPPL 8 , 2013 , Pages 290-293 ; 10978135 (ISSN) Shadbakhsh, F ; Shahriari, M ; Zabihollah, A ; Sharif University of Technology
    2013
    Abstract
    Micro grippers are essential tools for manipulation of objects in micron size. An electrostatic micro stepper-motor is used for actuating a proposed gripper mechanism and performance of this gripper is compared with the previous ones. The characteristic of the proposed mechanism is analyzed by simulation and it is shown that the designed gripper has the capability of doing manipulation in micron dimension with an acceptable performance  

    Size-dependent instability of carbon nanotubes under electrostatic actuation using nonlocal elasticity

    , Article International Journal of Mechanical Sciences ; Vol. 80 , 2014 , pp. 144-152 ; ISSN: 00207403 Seyyed Fakhrabadi, M. M ; Rastgoo, A ; Taghi Ahmadian, M ; Sharif University of Technology
    Abstract
    In this paper, the classical and nonlocal elasticity are applied to investigate the deflection and instability of electrostatically actuated carbon nanotubes. The results are presented for different geometries and boundary conditions. They reveal that increasing radius and gap and decreasing length confine to increasing pull-in voltages of the carbon nanotubes. The results prove that application of the nonlocal elasticity theorem leads to stiffer structures with higher pull-in voltages. Thus, in order to obtain more accurate results about the mechanical and electromechanical behaviors of the carbon nanotubes, one should apply the nonclassical elasticity theories such as that applied in this... 

    Non-linear behaviors of carbon nanotubes under electrostatic actuation based on strain gradient theory

    , Article International Journal of Non-Linear Mechanics ; Vol. 67, issue , 2014 , p. 236-244 Fakhrabadi, M. M. S ; Rastgoo, A ; Ahmadian, M. T ; Sharif University of Technology
    Abstract
    The paper deals with studying the deflection and pull-in voltages of the carbon nanotubes under electrostatic actuation with various dimensions and boundary conditions. The size-dependent behaviors of the carbon nanotubes (CNTs) are considered via application of the strain gradient theory. The results obtained from the strain gradient theory are compared to those estimated using the classical elasticity. The outcomes reveal that the classical elasticity theory underestimates the pull-in voltages of the carbon nanotubes and strain gradient theorem results in stiffer nano-structures with higher pull-in voltages. Increasing of the deflection due to the higher voltages increases the differences... 

    Development, modeling and deflection analysis of hybrid micro actuator with integrated thermal and piezoelectric actuation

    , Article Meccanica ; Volume 48, Issue 5 , 2013 , Pages 1081-1091 ; 00256455 (ISSN) Pourrostami, H ; Zohoor, H ; Kargarnovin, M. H ; Sharif University of Technology
    2013
    Abstract
    Micro actuators are irreplaceable part of motion control in minimized systems. The current study presents an analytical model for a new Hybrid Thermo Piezoelectric micro actuator based on the combination of piezoelectric and thermal actuation mechanisms. The micro actuator structure is a double PZT cantilever beam consisting of two arms with different lengths. The presented micro actuator uses the structure of electrothermal micro actuator in which polysilicon material is replaced by PZT. Also the voltage and poling directions are considered in the lengthwise of PZT beams. As a result, the piezoelectric actuation mechanism is based on d33 strain coefficient. The tip deflection of micro... 

    Analytical modeling of the effects of electrostatic actuation and casimir force on the pull-in instability and static behavior of torsional nano/micro actuators

    , Article International Journal of Modern Physics B ; Volume 27, Issue 6 , 2013 ; 02179792 (ISSN) Moeenfard, H ; Darvishian, A ; Ahmadian, M. T ; Sharif University of Technology
    2013
    Abstract
    This paper studies the effect of Casimir force on the pull-in instability of electrostatically actuated torsional nano/micro actuators. Dependence of the actuator's pull-in angle and pull-in voltage on several design parameters are investigated and it is found that Casimir force can considerably reduce the stability limits of the torsional actuators. Nonlinear equilibrium equation is solved numerically and analytically using straight forward perturbation expansion method. It is observed that a fourth-order perturbation approximation can precisely model the behavior of a torsional actuator. The results of this paper can be used for safe and stable design of torsional nano/micro actuators  

    Wideband tunable photonic crystal cavity with electrostatic actuation

    , Article 2012 IEEE Photonics Conference, IPC 2012, 23 September 2012 through 27 September 2012 ; September , 2012 , Pages 266-267 ; 9781457707315 (ISBN) Miri, M ; Sodagar, M ; Eftekhar, A. A ; Mehrany, K ; Rashidian, B ; Adibi, A ; Sharif University of Technology
    2012
    Abstract
    We present a wideband tunable optical cavity based on electrostatic actuation. Over 60nm shift in wavelength is achieved by applying less than 1 Volt corresponds to a mechanical displacement of 30nm  

    Control of planar motion of a magnetic microrobot using a novel electromagnetic actuation system

    , Article 4th International Conference on Manipulation, Automation, and Robotics at Small Scales, MARSS 2019, 1 July 2019 through 5 July 2019 ; 2019 ; 9781728109473 (ISBN) Yousefi, M ; Moradi, A ; Nejat Pishkenari, H ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2019
    Abstract
    A magnetic actuation system is a promising tool for untethered manipulation at the microscale that medical treatment can benefit from. This paper proposes a new magnetic actuation system that comprises of two coaxial coils on a rotary table. A fixed workspace is placed between coils. The proposed system is able to generate magnetic force with desired direction and magnitude in a plane. The conducted simulation and experiment confirm the capability of the proposed system to control the position of the microrobot. © 2019 IEEE  

    Nonlinear analysis of carbon nanotube-based nanoelectronics devices

    , Article Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science ; Vol. 228, issue. 13 , 2014 , p. 2426-2439 Fakhrabadi, M. M. S ; Rastgoo, A ; Ahmadian, M. T ; Sharif University of Technology
    Abstract
    The paper deals with the investigation of nonlinear static and dynamic behaviors of electrostatically actuated carbon nanotubes with different geometries and boundary conditions. The deflection and pull-in properties are studied in detail in the presence of DC and combined DC+AC electrostatic voltages accompanying the interatomic interactions. The considered nano system can be applied in a wide range of nanoelectronics devices such as nano switches, nano resonators, nano transistors, nano capacitors and random access memories. Moreover, a useful mathematical model of the nano sensor application of the studied nano system to sense the stiffness of the nano particles is presented  

    Efficient design of a torque actuator for lower extremity exoskeleton based on muscle function analysis

    , Article 2011 International Conference on Mechatronics and Materials Processing, ICMMP 2011, Guangzhou, 18 November 2011 through 20 November 2011 ; Volume 328-330 , 2011 , Pages 1041-1044 ; 10226680 (ISSN) ; 9783037852385 (ISBN) Safavi, S ; Selk Ghafari, A ; Meghdari, A ; Guangzhou University ; Sharif University of Technology
    2011
    Abstract
    Several lower extremity exoskeletal systems have been developed for augmentation purpose. Common actuators, have important drawbacks such as complexity, and poor torque capacities. The main scope of this research is to propose a series elastic actuator for lower extremity exoskeletal system which was designed based on muscle functional analysis. For this purpose, a biomechanical framework consisting of a musculoskeletal model with ten degrees-of-freedom actuated by eighteen Hill-type musculotendon actuators per leg is utilized to perform the muscle functional analysis for common daily human activities. The simulation study illustrated functional differences between flexor and extensor... 

    Design and analysis of an actuated endoscopic grasper for manipulation of large body organs

    , Article 2010 Annual International Conference of the IEEE Engineering in Medicine and Biology Society, EMBC'10, 31 August 2010 through 4 September 2010, Buenos Aires ; 2010 , Pages 1230-1233 ; 9781424441235 (ISBN) Mirbagheri, A ; Farahmand, F ; Sharif University of Technology
    2010
    Abstract
    During laparoscopic surgery, grasping of large body organs such as spleen, kidney, and liver, is a difficult task using conventional instruments. This paper describes the design and analysis of a novel actuated endoscopic grasper for manipulation of large internal organs. The designed instrument resembles a miniaturized three fingered hand with each finger consisting of two links. It could pass through a 10 mm trocar and then be opened inside the abdomen to grasp body organs up to 80 mm diameter. A detailed force analysis of the mechanism revealed that high actuating forces are required to grasp large organs. In order to facilitate the actuation of the grasper, its dimensions were optimized... 

    Actuator/sensor modeling for vibration of FGM solid circular plate using Reissner-Mindlin plate theory

    , Article ZAMM Zeitschrift fur Angewandte Mathematik und Mechanik ; Volume 90, Issue 4 , 2010 , Pages 287-308 ; 00442267 (ISSN) Jafari Mehrabadi, S ; Kargarnovin, M. H ; Najafizadeh, M. M ; Sharif University of Technology
    2010
    Abstract
    In this paper, the vibration of a constant thickness circular plate made of functionally graded material (FGM) is controlled by implementing two piezoelectric layers as a sensor and an actuator. Assuming that the material properties of FGM plate vary only in the thickness direction according to the power law manner, the governing differential equations are derived based on the Reissner-Mindlin plate theory (RMPT). Moreover, in a parallel work another set of differential equations are also derived using classical plate theory (CPT). Then for two different kinds of plate boundary conditions these coupled differential equations are solved using separation of variable technique and obtained... 

    Robust adaptive fault-tolerant control for leader-follower flocking of uncertain multi-agent systems with actuator failure

    , Article ISA Transactions ; Volume 71 , 2017 , Pages 227-234 ; 00190578 (ISSN) Yazdani, S ; Haeri, M ; Sharif University of Technology
    Abstract
    In this work, we study the flocking problem of multi-agent systems with uncertain dynamics subject to actuator failure and external disturbances. By considering some standard assumptions, we propose a robust adaptive fault tolerant protocol for compensating of the actuator bias fault, the partial loss of actuator effectiveness fault, the model uncertainties, and external disturbances. Under the designed protocol, velocity convergence of agents to that of virtual leader is guaranteed while the connectivity preservation of network and collision avoidance among agents are ensured as well. © 2017 ISA  

    Optimal vibration control of rotors with an open edge crack using an electromagnetic actuator

    , Article JVC/Journal of Vibration and Control ; Volume 24, Issue 1 , 2018 , Pages 37-59 ; 10775463 (ISSN) Ebrahimi, A ; Heydari, M ; Behzad, M ; Sharif University of Technology
    SAGE Publications Inc  2018
    Abstract
    Vibration control, especially in cracked rotors, is an important factor that can prevent the occurrence of disastrous failures. In this paper, vibrational control of a cracked rotor with an electromagnetic actuator has been studied with a continuous model of flexural vibration of cracked rotors. The governing equation of motion for the rotor under the external excitation of the electromagnetic actuator, gravity, and unbalanced forces is presented. A control law for the optimal control method to minimize the vibration of the rotor or stress at the crack section was obtained. To this aim, two cost functions have been introduced, based on the overall vibration of the rotor and the maximum... 

    Modeling and control of ionic polymer-metal composite structures

    , Article 13th International Congress on Sound and Vibration 2006, ICSV 2006, Vienna, 2 July 2006 through 6 July 2006 ; Volume 1 , 2006 , Pages 677-681 ; 9781627481502 (ISBN) Yousefi Koma, A ; Fazeli, R ; Sharif University of Technology
    2006
    Abstract
    Robotic devices are traditionally actuated by hydraulic systems or electric motors. However, in compact robotic systems, new actuator technologies are required. Ionic Polymer-Metal Composites (IPMCs) are attractive electroactivc polymer actuators because of their characteristics of large electrically induced bending, mechanical flexibility, low excitation voltage, low density, and ease of fabrication. A dynamic analytical model of IPMC is developed in this study. An RC model is employed based on time response results of a typical silver deposited IPMC. Results show that the electrical model is a suitable presentation of IPMC actuators. The model is tested with two experimental data of IPMC... 

    Analysis of separation control authority of DBD plasma actuator using hot-film sensor array

    , Article Journal of Applied Fluid Mechanics ; Volume 14, Issue 5 , 2021 , Pages 1421-1435 ; 17353572 (ISSN) Daliri, A ; Maghrebi, M. J ; Soltani, M. R ; Sharif University of Technology
    Isfahan University of Technology  2021
    Abstract
    The boundary-layer control authority of a DBD plasma actuator using surface mounted hot-film sensors is evaluated. Wind tunnel experiments on a wind-turbine blade section were established at a Reynolds number of 0.27 x 106. Aerodynamic performance of the wind-turbine blade section for both plasma-ON and plasma-OFF modes are evaluated using measurements made by both surface pressure and wake survey behind the model. Two distinct boundary-layer states are recognized. A state which occurs at the onset and in proximity of the deep stall, which is affected by the low-frequency instabilities of the separated flow. In this case, the steady actuation of plasma imparts local momentum on the nearby... 

    Design method and feasibility study of fully actively controlled frames

    , Article Scientia Iranica ; Volume 11, Issue 1-2 , 2004 , Pages 50-59 ; 10263098 (ISSN) Joghataie, A ; Asbmarz, M. M ; Sharif University of Technology
    Sharif University of Technology  2004
    Abstract
    In this paper, results of a preliminary study on the feasibility of using an Active Tendon Control (ATC) mechanism for frame structures subject to earthquakes is presented. So far, the ATC mechanism has mainly been considered as a means for installation on structures to mitigate their response under severe loading. In this study, it is desired to evaluate the possibility of using the ATC mechanism to serve as the main means for the stability of frames against earthquakes. Hence, a methodology is presented for the integrated design of frames with ATC mechanisms, which is tested numerically. A number of five-, ten-, fifteen- and twenty-story steel frames are used for this purpose. To this end,... 

    Adaptive actuator failure compensation on the basis of contraction metrics

    , Article IEEE Control Systems Letters ; Volume 6 , 2022 , Pages 1376-1381 ; 24751456 (ISSN) Boveiri, M ; Tavazoei, M. S ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2022
    Abstract
    This letter develops an adaptive actuator failure compensation method for nonlinear systems with unmatched parametric uncertainty based on contraction metrics. The proposed method, which is constructed by benefiting from the recent achievements on contraction metrics based adaptive control techniques, ensures the closed-loop stability and asymptotic tracking of the desired trajectory in the presence of actuator failures. In particular, a sufficient convex condition is derived for constructing a valid metric, by which a quadratic program-based controller is obtained to determine the inputs of the actuators. The introduced method is more general than the common adaptive actuator failure... 

    Fabrication, Visualization and Calibration of a Novel TEM Microactuator

    , M.Sc. Thesis Sharif University of Technology Takht Abnousi, Marjan (Author) ; Alasti, Aria (Supervisor)
    Abstract
    Nowadays precise nano positioning plays an important role in micro systems. Precise positioning at nano scale plays a basic role in nano science such as micro -robotics, solid state physics and photonics. Manipulating matter in a molecular scale creates a dramatic change and restruturing in macro scale engineering. During this research a novel TEM micro actuator is designed and fabricated based on calibration criteria. This structure was fabricated with SOI wafer (silicon on insulator) in micro scale level for the first time in Iran. This compliant consists of 12 TEM actuators end in 3DOF (In-plane) motion. The new micro actuator operates based on the thermal expansion due to voltage. Each... 

    Dynamic control of beams acted by multiple moving masses in resonance state using piezo-ceramic actuators

    , Article Proceedings of SPIE - The International Society for Optical Engineering ; 2012 ; 0277786X (ISSN) ; 9780819489982 (ISBN) Mofid, M ; Eftekhar Azam, S ; Afghani Khorasghan, R ; Sharif University of Technology
    2012
    Abstract
    In this article the constitutive equation of an Euler-Bernoulli beam, excited by multiple moving masses is considered. A set of multiple piezo-ceramic actuators is used to harness the dynamic response of the beam. In this regard the beam response is suppressed by utilizing a linear control algorithm with a time varying gain matrix and displacement-velocity feedback. The efficiency of the results is investigated through the numerical analysis of an example problem  

    Conceptual design of a miniaturized hybrid local actuator for Minimally Invasive Robotic Surgery (MIRS) instruments

    , Article Proceedings of the Annual International Conference of the IEEE Engineering in Medicine and Biology Society, EMBS ; 2011 , Pages 2140-2143 ; 1557170X (ISSN); 9781424441211 (ISBN) Saedi, S ; Mirbagheri, A ; Farahmand, F ; Sharif University of Technology
    Abstract
    The actuation mechanism of the tip of an endoscopic instrument is a major problem in designing miniature scale motorized instruments, especially when a high level of functionality and multi degrees of freedom (DOF) are concerned. We evaluated the different possible actuation methods for an endoscopic needle holder and proposed a new design of hybrid local-actuation, including a micro DC motor and a piezoelectric (PZT) actuator. The DC motor provided the long movement course required for opening-closing function of the gripper while the PZT guaranteed the high gripping force required for holding the needle. A compact serial configuration was considered for the actuators, producing an overall...