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    Design and Fabrication of a Ferrofluidic Miniature Pump

    , Ph.D. Dissertation Sharif University of Technology Ashouri, Majid (Author) ; Shafii, Mohammad Behshad (Supervisor) ; Moosavi, Ali (Supervisor)
    Abstract
    This thesis presents the prototype design and fabrication of magnetically actuated miniature pumps which utilize self-sealing capability of ferrofluid-covered permanent magnets in both pumping and valving mechanisms. The contactless external actuation feature of the design enables integration of the pump with other PMMA-based microfluidic systems with low cost and disposability. The body of the 1st fabricated prototype pump consists of three nozzle/diffuser elements and two pumping chambers connected to the ends of a flat-wall pumping cylinder. A cylindrical permanent magnet placed inside the pumping cylinder acts as a piston which reciprocates by using an external magnetic actuator driven... 

    Design and Fabrication of a Control Setup for a Miniature Mobile Robot Excited by Magnetic Field

    , M.Sc. Thesis Sharif University of Technology Salehi, Mobin (Author) ; Zohoor, Hassan (Supervisor) ; Nejat Pishkenari, Hossein (Co-Supervisor)
    Abstract
    Humans can take lots of advantages from influencing on small particles. Since manipulation of micro sizes by humans or macro robots, due to their precession and size, is not possible, a new field of study, called Microrobotics, has been introduced. To better understand the working principles in small dimensions, we first need to know the governing physics laws. This step helps us to identify the dominant forces in the small dimensions, which, in turn, leads to better actuation of miniature robots. Because of the size of the miniature robots, one of the best actuation methods is the interaction of the magnetic field on magnetic dipoles. To use the magnetic field as an actuation force, the... 

    Theoretical and experimental studies of a magnetically actuated valveless micropump

    , Article Journal of Micromechanics and Microengineering ; Volume 27, Issue 1 , 2017 ; 09601317 (ISSN) Ashouri, M ; Shafii, M. B ; Moosavi, A ; Sharif University of Technology
    Institute of Physics Publishing  2017
    Abstract
    This paper presents the prototype design, fabrication, and characterization of a magnetically actuated micropump. The pump body consists of three nozzle/diffuser elements and two pumping chambers connected to the ends of a flat-wall pumping cylinder. A cylindrical permanent magnet placed inside the pumping cylinder acts as a piston which reciprocates by using an external magnetic actuator driven by a motor. The magnetic piston is covered by a ferrofluid to provide self-sealing capability. A prototype composed of three bonded layers of polymethyl-methacrylate (PMMA) has been fabricated. Water has been successfully pumped at pressures of up to 750 Pa and flow rates of up to 700 μl min-1 while... 

    Numerical Simulation and Characterization of a Micro-mixer with Moving Walls

    , M.Sc. Thesis Sharif University of Technology Omidvar, Ahmad Reza (Author) ; Saeedi , Mohammad Saeed (Supervisor) ; Sani, Mahdi (Supervisor)
    Abstract
    Recent advances in micro-technology are finding important applications especially in chemical and biological processes. In these applications, mixing has a profound importance. Due to the inherent low Reynold’s number flow in micro systems, diffusion mixing is the dominant mixing mechanism at these scales. This is in contrary to the high Reynold’s number ordinary applications where turbulent mixing plays the major role. There are two major classes of micro-mixers: passive and active. Passive micro-mixers rely on geometric features to enhance mixing. Active micro-mixers on the other hand, use external excitation to promote and control the rate of mixing. In this work, using numerical tools,... 

    A novel revolving piston minipump

    , Article Sensors and Actuators, B: Chemical ; Volume 218 , October , 2015 , Pages 237-244 ; 09254005 (ISSN) Ashouri, M ; Shafii, M. B ; Moosavi, A ; Amiri Hezave, H ; Sharif University of Technology
    Elsevier  2015
    Abstract
    In this study, a novel prototype high-efficiency miniature pump that uses magnetic properties of a ferrofluid in both pumping and valving mechanisms is presented. The minichannel consisting of a cylindrical pumping chamber, a check valve, an inlet and an outlet, comprises six bonded layers of PMMA. A cylindrical permanent magnet that is placed inside the chamber and is externally actuated by a motorized off-center permanent magnet, functions as a revolving piston which sweeps the perimeter of the cylinder. Ferrofluid is used to cover the gaps between the magnetic piston and the channel walls, also serves as a separating plug between the inlet and the outlet of the chamber preventing... 

    Diffuser miniature pump with an extra ferrofluidic valve

    , Article Microfluidics and Nanofluidics ; Volume 19, Issue 5 , November , 2015 , Pages 1235-1244 ; 16134982 (ISSN) Ashouri, M ; Shafii, M. B ; Moosavi, A ; Sharif University of Technology
    Springer Verlag  2015
    Abstract
    This paper presents the prototype design and fabrication of a magnetically actuated miniature pump that utilizes self-sealing capability of ferrofluid-covered permanent magnets in both pumping and valving mechanisms. The valving action is performed by employing one active valve along with two nozzle/diffuser elements. Two cylindrical permanent magnets are placed inside the flat-wall channels: One magnet acts as the active valve and the other one serves as a reciprocating piston actuating the working fluid. In order to seal the gaps between the channel walls and the permanent magnet of the valve/piston, ferrofluid is used to cover the surfaces of both magnets. The valve and the piston are... 

    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  

    Localization and Control of a Continuum Robot

    , Ph.D. Dissertation Sharif University of Technology Yousefi, Masoud (Author) ; Nejat Pishkenari, Hossein (Supervisor) ; Alasty, Aria (Supervisor)
    Abstract
    Magnetic steering of continuum robots is a promising technology that uses a magnetic field to control the robot without contact and can improve the accessibility, safety, and accuracy of the robot. On the other hand, magnetic localization can also be used as a positioning method without direct line of sight in various applications. Common magnetic localization methods face the challenge of dependence on initial guess, divergence, and high computational cost. In this research, by eliminating the unknowns related to the orientation and rewriting the equations, a new method for magnetic localization has been presented. The advantage of the new method in convergence and increasing the speed of... 

    Optimal controller design for 3D manipulation of buoyant magnetic microrobots via constrained linear quadratic regulation approach

    , Article Journal of Micro-Bio Robotics ; Volume 15, Issue 2 , 2019 , Pages 105-117 ; 21946418 (ISSN) Pedram, A ; Nejat Pishkenari, H ; Sitti, M ; Sharif University of Technology
    Springer  2019
    Abstract
    We consider magnetic actuation and control of a spherical neutrally buoyant magnetic microrobot via magnetic coil setups and seek to design an optimal controller to reduce the required energy and coils’ currents. We showed that in currently employed setups, where the actuation frequency is few tens of Hertz, the nonlinear dynamics of the system can be well approximated by a set of linear constrained ones. The approximated model is obtained by consciously overlooking the rotational dynamics and the inertia terms in translational dynamics. We acquired the linear quadratic regulation (LQR) controller for the approximated model which is a constrained time-varying system. Finally, 3D manipulation... 

    Fault-tolerant control of flexible satellite with magnetic actuation and reaction wheel

    , Article Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering ; 2021 ; 09544100 (ISSN) Hajkarim, M. H ; Assadian, N ; Sharif University of Technology
    SAGE Publications Ltd  2021
    Abstract
    The attitude fault-tolerant control of a flexible satellite actuated by reaction wheels and magnetic torquer bars is investigated in this article. A low earth orbit is considered for moment perturbations such as drag and gravity gradient. Furthermore, the flexible panels attached to a rigid central body are modeled through the assumed mode approach by a finite set of bending modal motion. The ordinary differential equations of their generalized coordinates are found using Lagrange’s equation, and the resulting dynamical model is validated by comparing its simulation results to the NX Siemens software results. Finally, a fault-tolerant controller based on sliding mode control is suggested and... 

    Fault-tolerant control of flexible satellite with magnetic actuation and reaction wheel

    , Article Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering ; Volume 236, Issue 6 , 2022 , Pages 1222-1238 ; 09544100 (ISSN) Hajkarim, M. H ; Assadian, N ; Sharif University of Technology
    SAGE Publications Ltd  2022
    Abstract
    The attitude fault-tolerant control of a flexible satellite actuated by reaction wheels and magnetic torquer bars is investigated in this article. A low earth orbit is considered for moment perturbations such as drag and gravity gradient. Furthermore, the flexible panels attached to a rigid central body are modeled through the assumed mode approach by a finite set of bending modal motion. The ordinary differential equations of their generalized coordinates are found using Lagrange’s equation, and the resulting dynamical model is validated by comparing its simulation results to the NX Siemens software results. Finally, a fault-tolerant controller based on sliding mode control is suggested and...