Sharif Digital Repository

Minimally Invasive Surgery (MIS) is a modern surgical technique in which the operation is performed through small incisions in the body. Therefore, the surgeon looses his/her sense of touch which is of high importance in any medical operation. In the present work, a novel smart grasper is presented in which the surgeon can virtually acquire a feeling of force/momentum experienced by the organ/tissue. The smart grasper uses piezoelectric sensors bonded at desired locations to detect the applied force/momentum applied by surgeon and to measure the transmitted force/momentum to the tissue/organ. First, an accurate electro-mechanical model of the smart grasper is developed and the relations... 

Microemulsion is one of the major processing techniques to synthesize a nano, homogeneous, and almost agglomerate-free powders. Any kind of oxide ceramics such as piezoelectric ceramics can be synthesis via this method in nano scale without the formation of any intermediate phase. In this study, Lead zirconate titanate (PZT) powders with composition near the morphotropic phase boundary (MPB) have been synthesized via a microemulsion processing route. This emulsion system is a thermodynamically stable mixture of oil (cyclohexane), nonionic surfactant (Triton X100), and an aqueous solution containing specific amount of Pb2+, Zr4+ and Ti4+. The ratio of these ions was adjusted with using ICP.... 

In this paper, a novel control approach for one-dimensional bilateral teleoperated nanomanipulation system is proposed. While manipulating objects with a nanomanipulator, real time visual feedback is not available. So, force feedback is used to compensate for the lack of visual information. Since nanometer scale forces are dominated by surface forces instead of inertial forces as in macro world, scaling of nanoforces is one of the major issues of teleoperation system. The Hertz elastic contact model is used to model the interactions between the slave robot and the environment. The proposed framework uses the simple proportional derivative control, i.e., the master and slave robots are... 

The actuation mechanism of the tip of the laparoscopic instrument is the main problem in designing the process of miniature scale motorized instruments especially when high level of functionality and multi degrees of freedom (DOF) are concerned. Previous studies suggest local actuation as the best design for this kind of end effectors. In the present study, different actuation methods of needle holders were reviewed, related capabilities and drawbacks were evaluated and a hybrid local actuated design was appointed. The hybrid design included a micro DC motor and a PZT actuator. The main idea behind it was to combine the advantages of DC motors and piezoelectric (PZT) actuators in providing... 

Nanopositioning systems are devices with the ability of moving objects within nanometer resolution. In the recent years according to the advancements in the nanotechnology fields, there is an urgent and growing need for these systems as precision motion drivers. In the most of the nanopositiong devices some active materials such as piezoelectric elements are widely used as actuators. Piezoelectric materials can generate a mechanical deformation proportional to the applied electrical field. Therefore, theoretically these devices have the ability to set the desired position with the infinite precision.Design, optimization and fabrication of an ultrasonic piezoelectric motor are performed in... 

Microrobots design and manufacturing has been one of interesting fields in robotics in recent decades. They have been designed in various types so far. In this paper a two-leg microrobot is simulated and controlled by using LuGre friction model.
The proposed microrobot is driven by a piezoelectric actuator mounted between centers of two legs. The piezoelectric is actuated by a frequency near the natural frequency of the robot. The nonlinear dynamical equations of the system are obtained considering LuGre friction model. To control the system, the equations of motion are linearized using feedback linearization method. Then a stabilizing control law is designed and the robot model is... 

This thesis presents an analytical solution for determination of the
electro-elastic media subjected to an anti plane shear harmonic wave containing a multi-phase cylindrical fiber whose electro-elastic properties differ from those of the matrix. Both the matrix and the coated-fiber system are transversely isotropic piezoelectric materials with symmetry and poling axes parallel to the fiber axis. The coating can have variable thickness. The dynamic electro-mechanical equivalent inclusion method (DEMEIM) is presented and employed as an extension of dynamic equivalent inclusion method (DEIM) in order to take into account the electro-mechanical coupling. Accordingly, the coating-fiber... 

Structural vibrations can be reduced using an opposite force generated from an active controller. Nowadays implementation of smart materials for active controlling of vibration is growing increasingly specially in aircrafts, spacecrafts and other state of art manmade machines. In aerospace structures as the weight is extremely a limiting factor, the lightweight structural control strategies are more demanded. Considering these motivations, in recent decades, engineers have done many researches to implement active structural damping methods in industrials applications. Among all active vibration approaches, using piezoelectric materials is one of the most attractive ways because of their... 

With respect to the introduction of bio-material into cells (transfection) , microinjection is a highly efficient technique amongst existing methodologies. In cell injection, a manipulator injects the needle into a cellwhich is hold by a pipet mechanism. The moving range for the needle in this operation is of centimeter order and the resolution for the needle tip should be less than the cell’s diameter. In this thesis a Stewart system is used as for the manipulator. Stewart systems are used in flight simulators systems for decades, as mechanisms which are capable of providing multi-axis movements. In high accuracy positioning and multi-axis applications Stewart systems are highly reliable.... 

Studying the interactions between gas molecules and surface is one of the important issues in the field of sensing. In nanometer scales, it can play a key role in fabricating novel nanosensors. Tunneling spectroscopy, on the other hand, is a powerful method for studying the local electrical properties of surface. Our purpose in this project is to design and construct a local tunneling spectroscope, which is able to probe the effects of adsorption of gas molecules on local density of state (LDOS) in sub-nanometer scales. The designed and constructed local tunneling spectroscope system includes a small chamber, which is isolated from any vibrations by means of a set of dampers. In the main... 

The propagation of the surface waves in the piezoelectric (PE) and piezomagnetic (PM) layered media are studied. The surface BG waves in the PE half-spaces overlaid by a layer are considered and the closed-form dispersion relations for the open and short electromechanical surface boundary conditions are obtained. The numerical results for the phase velocities and the electromechanical coupling factor for PZT-2 and PZT-8 media are presented. Furthermore, the propagation of the Rayleigh waves in the PE-PM layered media is considered. The effects of the imperfect bonding between the half-space and the layer are discussed. Later, we study the propagation of the Rayleigh waves in 4 different... 

For many low-powered portable and wireless electronic applications the finite energy density of chemical batteries places limits on their functional lifetime. Through the use of energy harvesting techniques, ambient vibration energy can be captured and converted into usable electricity in order to create self-powering systems which are not limited by finite battery energy. Typical energy harvesting systems are composed of two components, a transducer that converts the mechanical vibrations into electrical energy and a power converter that efficiently delivers the harvested energy to the electronic load. The practical design of energy harvesting systems must include both components and... 

Nowadays, in many of industrial processes, it’s necessary to measure acceleration of a moving object. Among the different type of accelerometers, the piezoelectric type are most useful and the most widely used. These sensors come in various configurations.
In the past, analytical and semi-empirical models have been used to design piezoelectric accelerometers. In these methods, based on some assumptions, the accelerometer nonlinear model is replaced with a linear model and the equivalent circuit model has been used to model accelerometer behavior. In these methods, the behavior of accelerometer become different from the expected one.
Recently, with the invention of efficient computing... 

Piezoelectric Energy Harvesters (PEH)’s are devices that by means of Piezoelectric effect, convert ambient vibrations directly into electricity.
PEHs are often modeled as a cantilever beam with two piezoelectric layer attached to its sides. Due to their high energy density, small dimensions and adaptability to harsh environment, PEHs are referred to be a suitable substitute for batteries in the near future.
In this study, a new design of PEH is introduced in which a piezoelectric actuator is placed within web of a PEH so that by applying appropriate voltage to it, the distance between the two flanges of the beam, and accordingly the moment of inertia of the beam, is adjusted such... 

In this research a microrobot constructed from three series connected microcantilever has been introduced and its behavior has been evaluated. Length of each microcantilever is about several hundred microns. Due to actuation of microrobot, piezoelectric has been employed. Considering one DOF of each microcantilever, this microrobot has three DOF. Manipulation and microscopy in nano and micron scale can be mentioned as main duties for this microrobot. In devices which are used for these purposes commonly parallel mechanisms are employed. Also in some devices such as AFM, samples are needed to be placed on platform. However in this study a serial mechanism has been employed which make this... 

One can use the vibrational energy available in environment to harvest energy via piezoelectric materials, for various applications and this research field has received growing attention by researchers over the last years. This research motivation is, harvesting electrical energy from a fluttering plate in 2D axial flow via piezoelectric materials. For this purpose, a nonlinear Euler-Bernoulli beam model is used to model structure, an incompressible 2D vortex lattice method is used to model the aerodynamics, and coupled linear piezoelectric electro-mechanical equations is used to model piezoelectric materials. The structure is considered into axial flow, and flow speed gradually increases,... 

With regard to daily developments in micro and nanotechnology , the use of micro robots, In a different of applications increased extensively. The aim of this research was to introduce a mobile micro robot and analysis its behavior. this micro robot has several microlegs which are formed from microbeam mechanism and piezoelectric actuators. The degrees of freedom by taking any micro beam, any of these microlegs are able to move in a three-dimensional space. The mechanism used in this research for each of the microrobot legs, as was the consecutive series and its increase, in manor motor .In this research, unlike the previous tasks, piezoelectric actuators are considered as end effectors and... 

Polyvinylidene fluoride (PVDF) is remarkable since its mechanical properties, chemical stability and significant ferroelectricity. This Polymer has a simple chemical structure and can be found in five different crystal phases (α,β ,ɣ,δ and ε). Between these phases, beta shows a substantial pyro and piezoelectric activity since its great dipole moment. In this study PVDF/Poly(vinyl acetate)/Nanodiamond (ND) nanocomposite films were synthetized by solving in dimethylformamide adding ND particles to PVDF/PVAc blend in order to improve mechanical and piezoelectric properties. Scanning electron microscopy results showed that PVDF/PVAc are miscible and lead to a single crystal phase and dispersion... 

One of the unusual features of some ceramic materials is the piezoelectric effect. The piezoelectric effect results from the linear electromechanical interaction between the mechanical and electrical states in crystalline materials with no inversion symmetry. The piezoelectric effect is a reversible process: materials exhibiting the piezoelectric effect (the internal generation of electrical charge resulting from an applied mechanical force) also exhibit the reverse piezoelectric effect, the internal generation of a mechanical strain resulting from an applied electrical field. In the last decades, many research has been done on the use of these materials for the self-charging low-power... 

Tapering the beam along its length may lead to an increase in the voltage density of piezoelectric energy harvester. In this study, the energy harvester voltage with linear variable cross section is studied by developing an analytical method in both linear and nonlinear states. In linear mode, the results are compared with the experimental results. For the development of linear and nonlinear analytic relations, the Euler–Bernoulli beam and linear voltage variations in the thickness direction are used, and for the separation of variables, the mass normalized mode shapes has been used. The results of the linear analytical method are compared with the results of past research and experimental...