Development of An In Vivo Robotic Camera for Dexterous Manipulation and Clear Imaging

Minimally invasive surgeriy (MIS) techniques are becoming more popular as replacements for traditional open surgeries. These methods benefit patients with lowering blood loss and post-operative pain, reducing recovery period and hospital stay time, decreasing surgical area scarring and cosmetic issues, and lessening the treatment costs, hence greater patient satisfaction would be earned. Manipulating surgical instruments from outside of abdomen and performing surgery needs precise hand-eye coordination which is provided by insertable cameras. The traditional MIS insertable cameras suffer from port complexity and reduced manipulation dexterity, which leads to defection in Hand-eye coordination and surgical flow. Fully insertable robotic camera systems emerged as a promising solution in MIS. Implementing robotic camera systems faces multiple challenges in fixation, manipulation, orientation control, tool-tissue interaction, in vivo illumination and clear imaging.In this dissertation a novel actuation and control mechanism is developed and validated for an insertable laparoscopic camera. This design uses permanent magnets and coils as force/torque generators in an external control unit to manipulate an in vivo camera capsule. The motorless design of this capsule reduces the, wight, size and power consumption of the driven unit. In order to guarantee the smooth motion of the camera inside the abdominal cavity, an interaction force control method was proposed and validated.Optimizing the system\u27s design, through minimizing the control unit size and power consumption and extending maneuverability of insertable camera, was achieved by a novel transformable design, which uses a single permanent magnet in the control unit. The camera robot uses a permanent magnet as fixation and translation unit, and two embedded motor for tilt motion actuation, as well as illumination actuation. Transformable design provides superior imaging quality through an optimized illumination unit and a cleaning module. The illumination module uses freeform optical lenses to control light beams from the LEDs to achieve optimized illumination over surgical zone. The cleaning module prevents lens contamination through a pump actuated debris prevention system, while mechanically wipes the lens in case of contamination. The performance of transformable design and its modules have been assessed experimentally

Numerical Analysis of a Roadway Piezoelectric Harvesting System

Highways, streets, bridges, and sidewalks with heavy traffic dissipate a considerable amount of waste mechanical energy every day. Piezoelectric energy harvesting devices are a very promising technology that can convert the waste mechanical energy to clean and renewable energy to enhance the sustainability of infrastructures. Research efforts in large-scale energy harvesting have led to the advancement of piezoelectric devices to the point that large-scale implementation is starting to become more feasible. The energy harvested by these devices can be used in many ways such as providing heating or cooling, melting ice, monitoring structural conditions in bridges and tunnels, and powering wireless sensors. Additionally, these devices contain an off-grid power system meaning that it has a standalone battery connected to it. This is highly beneficial in areas where city power sources are not readily available. The objective of this thesis is to study the energy harvesting potential of a dual-mode piezoelectric generator to develop a roadway piezoelectric harvesting system with ultra-high-power density and efficiency. The dual-mode harvester is made up of APC 855 with two different modes, 33-mode and 15-mode. In order to structurally optimize the design, finite element analysis was performed using ANSYS Mechanical and APDL. Static and transient simulations for each model with detailed input conditions were evaluated to determine the optimal configuration. Two different vehicle sizes were evaluated to assess the load effect on the harvested power. In addition, open circuit and closed-circuit models with different resistance values were compared to determine the resistance that produces the highest energy. Furthermore, a comparison between the different polarization directions for the 15-mode harvester was investigated to determine the optimal polarization direction

Plate Vibration Dispalcement Curve Measurement Using PVDF

Beam and plate dynamics are often measured using accelerometers and in some cases laserbased systems. Natural frequencies, mode shapes, and deflections are then derived from these measurements. The work presented here describes a method to directly measure the deflection curve of a vibrating beam and plate using piezoelectric films. The sensor consists of constant shape segment of PolyVinyliDene Fluoride (PVDF) films bonded to the surface of the structure. We show in here that each segment of the sensor measures the deflection slope at its particular location. The overall lateral displacement curve of the structure (beam/plate) is calculated from these slopes using central difference formulas. In this work, the equations of the sensor are presented along with the results of the numerical verifications. Numerical simulations are executed through MATLAB, whereas Multiphysics simulation is accomplished through ANSYS, and the results of these simulations are compared to the experimental results. The results indicate that the proposed sensors can be used to efficiently and respectively measure the lateral vibration displacements curves of beams and plates with various boundary conditions

Development of Non-Destructive Testing by Eddy Currents for Highly Demanding Engineering Applications

Defect detection with Non-Destructive Testing (NDT) is essential in accidents prevention, requiring R&TD to generate new scientific and procedural knowledge for new products with high safety requirements. A current challenge lies in the detection of surface and sub-surface micro defects with NDT by Eddy Currents (EC). The main objective of this work was the development of applied research, technological innovation and experimental validation of EC customized systems for three highly demanding inspection scenarios: micro defects in tubular geometries; brazed joints for the automotive industry; and high-speed moving composite materials. This objective implied starting from the scientific fundamentals of NDT by EC to design and simulate EC probes and the prototypes developed were tested in industrial environment, reaching a TRL ≈ 5. Another objective, of a more scientific and disruptive nature, was to test a new technique for the creation of EC in the materials to be inspect, named Magnetic Permeability Pattern Substrate (MPPS). This technique consists on the development of substrates/films with patterns of different magnetic permeabilities rather than the use of excitation bobbin coils or filaments of complex geometry. The experimental results demonstrated that the prototypes developed for the three industrial applications studied outperformed the state of the art, allowing the detection of target defects with a very good signal-to-noise ratio: in tubular geometries defects with depth of 0.5 mm and thickness of 0.2 mm in any scanning position; in the laser brazed weld beads pores with 0.13 mm diameter and internal artificial defects 1 mm from the weld surface; in composite materials defects under 1 mm at speeds up to 4 m/s and 3 mm lift-off. The numerical simulations assisted the probe design, allowing to describe and characterize electrical and magnetic phenomena. The new MPPS concept for the introduction of EC was validated numerically and experimentally

Improved micro-contact resistance model that considers material deformation, electron transport and thin film characteristics

This paper reports on an improved analytic model forpredicting micro-contact resistance needed for designing microelectro-mechanical systems (MEMS) switches. The originalmodel had two primary considerations: 1) contact materialdeformation (i.e. elastic, plastic, or elastic-plastic) and 2) effectivecontact area radius. The model also assumed that individual aspotswere close together and that their interactions weredependent on each other which led to using the single effective aspotcontact area model. This single effective area model wasused to determine specific electron transport regions (i.e. ballistic,quasi-ballistic, or diffusive) by comparing the effective radius andthe mean free path of an electron. Using this model required thatmicro-switch contact materials be deposited, during devicefabrication, with processes ensuring low surface roughness values(i.e. sputtered films). Sputtered thin film electric contacts,however, do not behave like bulk materials and the effects of thinfilm contacts and spreading resistance must be considered. Theimproved micro-contact resistance model accounts for the twoprimary considerations above, as well as, using thin film,sputtered, electric contact

Mechanical and electromagnetic transverse load effects on superconducting niobium-tin performance

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Nuclear Science and Engineering, 2009.Cataloged from PDF version of thesis.Includes bibliographical references (p. 233-238).Cable-in-Conduit Conductor is the typical geometry for the conductor employed in superconducting magnets for fusion applications. Once energized, the magnets produce an enormous electromagnetic force and very large transverse loads are applied against the strands. This large force results in a degradation of the performance of the superconducting magnets. In this thesis work transverse load experiments on sub-sized cables, have been designed to study the mechanical and electrical transverse load effects on superconducting cables. Two devices to apply external mechanical loads to a cable have been developed and several different size cables have been tested simulating the International Thermonuclear Experimental Reactor (ITER) Lorentz stress conditions. The first device was designed to use a circular turn sample of a 36-strand cable. Four samples were successfully tested with this device and significant degradations of the critical current due to the external transverse loads have been measured. However, all samples showed unexpectedly large initial degradations that made an analysis of transverse load effects of the samples difficult. The second device was developed for a hairpin configuration. Three different size cables of a single strand, a triplet and a 45-strand cable were systematically tested using this method. This hairpin sample device has successfully operated and provided very reliable experimental data. The experimental results were difficult to explain by existing theories.(cont.) A new model based on contact mechanics concepts has been developed to determine the number of contacts and the effective contact pressure among the strands in a cable. The model was used to analyze and accurately calculate the displacements of a cable under transverse mechanical load, and it has evaluated the effective contact pressures between strands for the first time. The new model can explain the Lorentz force and contact pressure distribution effect on the critical current degradation of the tested samples. The 3-strand data and their critical current behavior as a function of the effective contact pressure were used to predict the test behavior of a 45-strand cable. It was also used to simulate the critical current degradations of various cables including ITER full size cables. The model has predicted an initial degradation of 20% for an ITER TF cable of 1152 strands at 68 kA operational current caused by the transverse Lorentz load effect only. Parametric studies of the model have indicated that the initial degradation could be reduced by shortening the twist pitch length of the initial stages of a full size cable or by mechanically supporting the last stage bundles of the cable. This thesis work shows for the first time, that the transverse Lorentz load effect, which is inherent in the CICC design, contributes a significant fraction of the degradation of a large Nb3Sn superconducting cable. The model quantifies the degradation and this information could be used in better estimating the appropriate margin requirements in magnet design.by Luisa Chiesa.Ph.D

Vibration Analysis And Shape Control Of A Beam With Piezoelectric Patches

Tez (Yüksek Lisans) -- İstanbul Teknik Üniversitesi, Fen Bilimleri Enstitüsü, 2011Thesis (M.Sc.) -- İstanbul Technical University, Institute of Science and Technology, 2011Günümüzde kullanım alanları oldukça genişleyen piezoelektrik malzemeler, araştırma ve geliştirme için uygun konu olarak algılayıcı, kumanda elemanı ve akıllı yapıların kullanımında sıklıkla karşımıza çıkmaktadırlar. Piezoelektrik malzemeler elektriksel alana maruz kaldıklarında boyutlarında değişiklikler olmakta ve tersi durumda boyutsal şekil değişikliklere zorlandıklarında da elektrik sinyalleri üretmektedirler. Mekanik gerilmeye maruz kaldıklarında elektrik alan oluşturan piezoelektrik malzemeler, yüksek elastisite modülleri sayesinde ana yapının katılık ve kütle matrislerine ihmal edilebilir boyutta bir artış sağladığından ana yapıda çok sayıda kullanılıp titreşim ve şekil kontrolünün sağlanması işlevini görmektedirler. Yan sistemlerin desteğini almaksızın sağladıkları bu özellikleri ile piezoelektrik malzemeler havacılık ve uzay sanayinde aktif titreşim kontrolünde yaygın olarak tercih edilmektedirler. Bu çalışmada, piezoelektrik yamalı bir kirişin farklı sınır koşulları ve farklı yükler altında titreşim analizinin yapılması amaçlanmaktadır. Buna bağlı, piezoelektik yamalı bir kirişin Euler-Bernoulli Kiriş Teorisi ve Timoshenko Kiriş Teorisi göz önünde bulundurularak şekil fonksiyonu ve şekil kontrol analizleri yapılmıştır. Farklı sınır koşulları için kiriş davranışının inceleneceği teorik çalışmada, piezoelektrik yama yer değişimi etkisi ve farklı voltaj uygulamlarının sonuçları araştırılmıştır. Piezoelektrik yama içeren, farklı sınır koşullarına maruz kalmış bir kirişin hareket denklemleri çıkartılmış ve doğal frekans hesapları yapılmıştır. Teorinin literatür çalışmaları ile doğrulanmasının amaçlandığı bu çalışma ile ülkemizde piezoelektrik malzeme teknolojisinin geliştirilmesi; bu sayede bilim ve mühendislik alanlarında kullanımının daha da yaygın hale gelmesi sağlanacaktır.Piezoelectric materials have been affirmative subjects to be investigated and very popular in engineering applications in the latest researches. Piezoelectric structures are commonly less rigid, so they are more sensitive to enormous vibration problems and that is why they are increasingly needed for aerospace applications, likewise they provide new important capabilities in military and civilian aerospace applications. In particular, there are plenteous studies, which are aimed to estimate to control the vibration characteristics of structures with piezoelectrics. In this thesis, first of all, shape analysis and control of a beam with piezoelectric patches are examined with considering both Euler Bernoulli Beam Theory (EBT) and Timoshenko Beam Theory (TBT). In the determination of structural models, all solutions are performed analytically to a beam subjected to different boundary conditions. Moreover, the effects of not only different voltage but also piezoelectric patch position on frequency and on shape functions of beam are interrogated. With a view to control the shape of beam in a good manner and obtaining better results, the errors are minimized. Furthermore, how the piezoelectric patches can impose the shape of a beam is shown by the obtained solutions. In addition to all, equations of motion and natural frequencies of beams with piezoelectric patches are achieved by means of Euler Bernoulli Beam Theory (EBT).Yüksek LisansM.Sc

NASA Tech Briefs, January 1995

Topics include: Sensors; Electronic Components and Circuits; Electronic Systems; Physical Sciences; Materials; Computer Programs; Mechanics; Machinery; Fabrication Technology; Mathematics and Information Sciences; Life Sciences; Books and Report

BULK-PIEZOELECTRIC TRANSDUCTION OF MICROSYSTEMS WITH APPLICATIONS TO BATCH-ASSEMBLY OF MICROMIRRORS, CAPACITIVE SENSING, AND SOLAR ENERGY CONCENTRATION

Electromechanical modeling, actuation, sensing and fabrication aspects of bulkpiezoelectric ceramic integration for microsystems are investigated in this thesis. A small-signal model that describes the energy exchange between surface micromachined beams and bulk-lead zirconium titanate (PZT) actuators attached to the silicon substrate is presented. The model includes detection of acoustic waves launched from electrostatically actuated structures on the surface of the die, as well as their actuation by bulk waves generated by piezoelectric ceramics. The interaction is modeled via an empirical equivalent circuit, which is substantiated by experiments designed to extract the model parameters. As a die level application of bulk-PZT, an Ultrasound Enhanced Electrostatic Batch Assembly (U2EBA) method for realization of 3-D microsystems is demonstrated. U2EBA involves placing the die in an external DC electric field perpendicular to the substrate and actuating the die with an off-chip, bulk-piezoelectric ceramic. Yield rates reaching up to 100% are reported from 8×8 arrays of hinged mirrors with dimensions of 180 × 100 micrometre-squared. U2EBA is later improved to provide temporary latching at intermediate angles between fully horizontal and vertical states, by using novel latching structures. It is shown that the micromirrors can be trapped and freed from different rotation angles such that zero static power is needed to maintain an angular position. The zero-idle-power positioning of large arrays of small mirrors is later investigated for energy redirection and focusing. All-angle LAtchable Reflector (ALAR) concept is introduced, and its application to Concentrated Solar Power (CSP) systems is discussed. The main premise of ALAR technology is to replace bulky and large arrays of mirrors conventionally used in CSP technologies with zeroidle- power, semi-permanently latched, low-profile, high-fill factor, micrometer to centimeter scale mirror arrays. A wirelessly controlled prototype that can move a 2-D array of mirrors, each having a side length of less than 5 cm, in two degrees of freedom to track the brightest spot in the ambient is demonstrated. Capacitive sensing using bulk-piezoelectric crystals is investigated, and a Time- Multiplexed Crystal based Capacitive Sensing (TM-XCS) method is proposed to provide nonlinearity compensation and self-temperature sensing for oscillator based capacitive sensors. The analytical derivation of the algorithm and experimental evidence regarding the validity of some of the relations used in the derivation are presented. This thesis also presents results on microfluidic particle transport as another application of bulk-PZT in microsystems. Experiments and work regarding actuation of micro-scale, fluorescent beads on silicon nitride membranes are described