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1
Kelly, Brian L. "Beam shape control using shape memory alloys." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1998. http://handle.dtic.mil/100.2/ADA358806.
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Thesis (M.S. in Astronautical Engineering) Naval Postgraduate School, December 1998.<br>"December 1998." Thesis advisor(s): Brij N. Agrawal, Gangbing Song. Includes bibliographical references (p. 55). Also available online.
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Norfleet, Walton A. (Walton Arthur) 1973. "Algorithms for closed loop shape control." Thesis, Massachusetts Institute of Technology, 2001. http://hdl.handle.net/1721.1/8559.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2001.<br>Includes bibliographical references (p. 147-149).<br>The stretch forming process is used to make structural sheet metal parts in the aerospace industry. The development of stretch forming tools has long been plagued by significant challenges. First, the low production volumes within the aerospace industry and the large numbers of stretch formed parts make the process capital intensive. Second, the development of stretch forming tooling has long been more of an art than a science. This results in poorly designed tools, poor quality parts, and lengthy tooling development cycles. A stretch forming tool capable of rapid reconfiguration was previously designed to address these issues. This tool is used in conjunction with a self-tuning shape control algorithm, which guides the die to the correct shape. There have been many simulations, and lab scale successes with these algorithms, but production scale implementations have experienced difficulties. These problems are related to the method of system identification and process variation. To better understand these issues, analysis and simulation are performed on the various forms of the algorithm. These investigations led to a greater understanding of the algorithms and the synthesis of an improved algorithm. In conclusion, a greater understanding of previously developed algorithms is presented. The system identification is mapped as a Point Spread Function applied through a cyclic convolution. This view provides insight into how the system identification is applied and allows system coupling to be quantified. Furthermore, through improved understanding a new algorithm is synthesized. This new algorithm offers an implementable solution that is optimized for performance, robustness to variation, and ease of use.<br>by Walton A. Norfleet.<br>S.M.
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Ruscelli, Francesco. "Shape-based compliance control for snake robots." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2016. http://amslaurea.unibo.it/11985/.
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I serpenti robot sono una classe di meccanismi iper-ridondanti che appartiene alla robotica modulare. Grazie alla loro forma snella ed allungata e all'alto grado di ridondanza possono muoversi in ambienti complessi con elevata agilità. L'abilità di spostarsi, manipolare e adattarsi efficientemente ad una grande varietà di terreni li rende ideali per diverse applicazioni, come ad esempio attività di ricerca e soccorso, ispezione o ricognizione.
I robot serpenti si muovono nello spazio modificando la propria forma, senza necessità di ulteriori dispositivi quali ruote od arti. Tali deformazioni, che consistono in movimenti ondulatori ciclici che generano uno spostamento dell'intero meccanismo, vengono definiti andature. La maggior parte di esse sono ispirate al mondo naturale, come lo strisciamento, il movimento laterale o il movimento a concertina, mentre altre sono create per applicazioni specifiche, come il rotolamento o l'arrampicamento.
Un serpente robot con molti gradi di libertà deve essere capace di coordinare i propri giunti e reagire ad ostacoli in tempo reale per riuscire a muoversi efficacemente in ambienti complessi o non strutturati. Inoltre, aumentare la semplicità e ridurre il numero di controllori necessari alla locomozione alleggerise una struttura di controllo che potrebbe richiedere complessità per ulteriori attività specifiche. L'obiettivo di questa tesi è ottenere un comportamento autonomo cedevole che si adatti alla conformazione dell'ambiente in cui il robot si sta spostando, accrescendo le capacità di locomozione del serpente robot. Sfruttando la cedevolezza intrinseca del serpente robot utilizzato in questo lavoro, il SEA Snake, e utilizzando un controllo che combina cedevolezza attiva ad una struttura di coordinazione che ammette una decentralizzazione variabile del robot, si dimostra come tre andature possano essere modificate per ottenere una locomozione efficiente in ambienti complessi non noti a priori o non modellabili.
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Ma, Chaoyang. "Particle shape distribution control in crystallisation processes." Thesis, University of Leeds, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.531612.
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Zhang, Jun. "Shape control in synthesis of functional nanocrystals." Diss., Online access via UMI:, 2009.
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Elshafei, Mostafa Adnan. "Smart composite plate shape control using piezoelectric materials." Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1996. http://handle.dtic.mil/100.2/ADA320548.
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Dissertation (Ph.D. in Aeronautical and Astronautical Engineering) Naval Postgraduate School, September 1996.<br>Dissertation supervisor(s): B.N. Agrawal. "September 1996." Includes bibliographical references (p. 111-118). Also available online.
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Selden, Brian A. 1980. "Segmented binary control of shape memory actuator systems." Thesis, Massachusetts Institute of Technology, 2005. http://hdl.handle.net/1721.1/30307.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2005.<br>Includes bibliographical references (p. 51).<br>A new approach to the design and control of shape memory alloy (SMA) actuators is presented. SMA wires are divided into many segments and their thermal states are controlled individually as a group of finite state machines. Instead of driving a current to the entire SMA wire and controlling the wire length based on the analogue strain-temperature characteristics, the new method controls the binary state (hot or cold) of individual segments and thereby the total displacement is proportional to the length of the heated segments, i.e. austenite phase. Although the thermo-mechanical properties of SMA are highly nonlinear and uncertain with a prominent hysteresis, Segmented Binary Control is robust and stable, providing characteristics similar to a stepping motor. However, the heating and cooling of each segment to its bi-stable states entail longer time and larger energy for transition. An efficient method for improving speed of response and power consumption is developed by exploiting the inherent hysteresis of SMA. Instead of keeping the extreme temperatures continuously, the temperatures return to intermediate "hold" temperatures closer to room temperature but sufficient to keep constant phase. Coordination of the multitude of segments having independent thermal states allows for faster response with little latency time even for thick SMA wires. Based on stress dependent thermo-mechanical characteristics, the hold temperature satisfying a given Stress Margin is obtained. The new control method is implemented using the Peltier effect thermoelectric devices for selective segment-by-segment heating and cooling. Experiments demonstrate effectiveness of the proposed method.<br>by Brian A. Selden.<br>S.M.
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Punhani, Amitesh. "Shape and Vibration Control of Smart Laminated Plates." The Ohio State University, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=osu1205990432.
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Ehlers, Righardt Frederick. "Feedback control of a shape memory alloy actuator for control surface deflection." Thesis, Stellenbosch : Stellenbosch University, 2012. http://hdl.handle.net/10019.1/19977.
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Thesis (MScEng)--Stellenbosch University, 2012.<br>ENGLISH ABSTRACT: The successful design, implementation and testing of a feedback control system for
tab-deflection control of a shape memory alloy (SMA) based control surface actuator
is presented. The research is performed as part of the Control Surfaces in Confined
Spaces (CoSICS) research project conducted at Stellenbosch University. The research
group investigates ways to provide control surface actuation in size-restricted spaces
in commercial aircraft such as the Airbus A320 and A330. This is achieved by investigating
the concept of trailing edge tabs to reduce the required torque load, resulting
in reduced actuator requirements enabling the use of smaller actuators. This thesis
contributes to the project by investigating the possibility of using SMA-based actuators
in reduced hinge moment requirement applications.
An SMA-based tab actuator demonstrator design is presented. Mathematical models
are derived for the SMA material, thermodynamics and actuator geometry. The models
are combined to formulate an SMA-based control surface actuator model. The model is
utilised in four tracking feedback controller designs; two based on linear and two based
on non-linear control techniques.
The manufactured prototype is presented along with the incorporated hardware for
controller implementation. System identification follows and validates the three mathematical
models.
Practical verification of the model and two of the controllers is conducted. The unimplemented
controllers are implemented through a validated model simulation. Controller
evaluation, based on the dynamic controller performance, is conducted. The results
validate the concept of using an SMA actuator for tab-deflection control and indicate
important limitations for the intended application.<br>AFRIKAANSE OPSOMMING: Die tesis behels die ontwerp, implementering en toetsing van ’n terugvoer beheerstelsel
vir hulpvlak defleksie beheer van ’n vorm-geheue allooi (SMA) gebaseerde aktueerder.
Die navorsing vorm deel van die Beheervlakke in Begrensde Ruimtes (CoSICS) navorsingsprojek
by Stellenbosch Universiteit. Die CoSICS navorsing behels ’n ondersoek na
beheervlak aktueering in beknopte spasies in kommersiële vliegtuie soos die Airbus
A320 en A330. Die probleem word aangespreek deur ’n ondersoek na aerodinamiese
hulpvlakke wat ’n vermindering in skarnier moment tot gevolg het en sodoende die
aktueerder vereistes verminder.
Hierdie tesis dra by tot die projek deur die moontlikheid van die gebruik van SMAgebaseerde
aktueerders in verminderde skarnier moment vereiste toepassings te ondersoek.
‘n SMA gebaseerde hulpvlak demonstrasie aktueerder ontwerp word voorgelê. Wiskundige
modelle vir die SMA materiaal, termodinamika en prototipe geometrie is geformuleer
en gekombineer om ‘n SMA gebaseerde beheervlak aktueerder model te ontwikkel.
Die model word in vier beheerder ontwerpe toegepas. Twee ontwerpe is op
liniëre en twee op nie-liniëre beheer tegnieke gebaseer.
Die prototipe en nodige hardeware vir beheerder implementasie is voorgedra. Stelsel
identifikasie is toegepas en verifieer die drie wiskundige modelle.
Praktiese verifikasie van die model en twee beheerders is gedoen. Die ongeïmplementeerde
beheerders is deur die geverifieerde aktueerder model gesimuleer. ‘n Beheerder
evaluasie gebaseer op die dinamiese beheerder gedrag word toegepas. Die
evaluasie beklemtoon kritiese aspekte en beperkinge in verband met SMA aktueering.
Die resultate regverdig die gebruik van ‘n SMA aktueerder vir hulpvlak defleksie beheer
en beklemtoon belangrike beperkinge ten opsigte van die voorgestelde toepassing.
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Nader, Manfred. "Compensation of vibrations in smart structures : shape control, experimental realization and feedback control /." Linz : Trauner, 2008. http://opac.nebis.ch/cgi-bin/showAbstract.pl?u20=9783854993865.
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Jenne, Theresa Clara. "Closed-loop control of roll bending/twisting : a shape control system for beams." Thesis, Massachusetts Institute of Technology, 1986. http://hdl.handle.net/1721.1/35334.
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Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1986.<br>MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING<br>Bibliography: leaves 150-152.<br>by Theresa Clara Jenne.<br>M.S.
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Xing, Zhe. "A novel approach to control the shape change of a reconfigurable wing using shape memory alloy." Thesis, Cape Peninsula University of Technology, 2007. http://hdl.handle.net/20.500.11838/1266.
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Thesis (MTech (Mechanical Engineering))--Cape Peninsula University of Technology, 2007.<br>Engineers and Technologists have found several approaches to control the
shape of an aerofoil and improve the performance of a wing at different flow
regimes; this research has been done at 2D level. In this work, a novel
approach has been developed. The inspiration for this work comes from
biological research. A 3D wing body has been modeled and flow conditions
around it were simulated by advanced computer technology. The fabrication of
the wing, based on the design optimization model, has been conducted using
rapid prototyping technology. The unique thermal and mechanical properties
that are exhibited by shape memory alloys (SMAs) have presented an exciting
design possibility in the field of aerospace engineering. This kind of smart
material was incorporated in the wing structure and when activated can alter
the shape of the wing, thus effectively increasing the efficiency of a wing in
flight, at several different flow regimes.
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Wasylyszyn, Jonathan Allen. "Active control of underwater propulsor using shape memory alloys." Thesis, Texas A&M University, 2005. http://hdl.handle.net/1969.1/4926.
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The development of a leading edge propeller blade reconfiguration system using Shape Memory Allow (SMA) muscles is presented. This work describes the design and testing of a leading edge flap, which is used to alter the local camber of a propeller blade. The leading edge flap is deflected by SMA wires housed in the blade and maintained in a fixed position with a shaft locking and releasing mechanism. A locking and releasing mechanism is utilized so that constant actuation of the SMAs is not required to maintain leading edge deflection. The profile at 70% span of the propeller blade was used to create a two-dimensional blade for leading edge flap design implementation and load testing. Deflection of up to five degrees was obtained with the final design of the leading edge flap and locking and releasing mechanism. The SMA muscles used to deflect the leading edge were actuated electronically through resistive heating and were controlled by a proportional/integral gain control algorithm with closed-loop feedback from a linear displacement sensor within the blade. With the final design of the leading edge flap and locking and releasing mechanism, a preliminary design for a three-dimensional propeller was created.
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Grant, Danny. "Accurate and rapid control of shape memory alloy actuators." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0020/NQ55336.pdf.
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Picone, R. "Extrinsic and intrinsic control of cell shape and polarity." Thesis, University College London (University of London), 2010. http://discovery.ucl.ac.uk/134320/.
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Since physical form and function are intimately linked, mechanisms that maintain cell shape and size within strict limits are likely to be important for a wide variety of biological processes. However, while intrinsic controls have been found to contribute to the relatively well-defined shape of bacteria and yeast cells, the extent to which individual cells from a multicellular animal control their plastic form remains unclear and is the subject of much scientific interest. In this work I studied the regulation of the cell length using micro-patterned lines to limit cell extension to one dimension. In particular, I described a mechanism by which animal cells maintain a characteristic steady-state length independent of their size, pattern-width and cortical actin, but dependant on microtubule dynamics and organization. Population of dynamic microtubules aligned along the long cell axis, as the result of interactions of microtubule plus ends with the lateral cell cortex, drives elongation of cells on micropatterned lines. Furthermore, I described a mathematical model of micropatterned cells based on microtubules dynamics. Notably, the model recapitulates the cell length control mechanism that I observed experimentally. Moreover, I discuss model predictions and related experimental tests validating these predictions and confirming the cell length control hypothesis. In conclusion, my work suggests that microtubules impose unexpected limits on cell geometry that enable cells to regulate their length. Since cells are the building blocks and architects of tissue morphogenesis, such intrinsically-defined limits may be important for development and homeostasis in multicellular eukaryotes. Finally, preliminary in-vivo experiments confirmed the biological relevance of the homeostasis cell length control in zebra fish.
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Ramezani-Dakhel, Hadi. "Bioengineered Metal Nanoparticles: Shape Control, Structure, and Catalytic Functionality." University of Akron / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=akron1426184509.
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Li, Wenhua. "Shape Control and Functional Properties of Copper Chalcogenide Colloidal Nanocrystals." Doctoral thesis, Universitat de Barcelona, 2013. http://hdl.handle.net/10803/131051.
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The high quality CuxS nanocrystals were synthesized (Chapter 3) and the profound understanding and skills to prepare colloidal nanocrystals has been obtained and improved. It revealed a very simple synthetic route not only for the systematic investigation on the size control of the copper sulfide nanodisks but also for studying the influence of different stoichiometric ratios on the shape of copper sulfide nanocrystals. An increase of the precursor concentration in the growth solution resulted in the formation of tetradecahedral and dodecahedral nanocrystals. XRD results showed these nanodisks had a similar composition close to Cu1.78S as spherical nanocrystals, however, the tetradecahedral and dodecahedral nanocrystals were characterized with a composition close to Cu1.96S as deduced from their djurleite crystal phase. An oriented attachment was proposed as growth mechanism for polyhedrons growth and the slow nucleation rate allows an accurate control of the size and morphology of CuxS nanocrystals, from spheres and disks to tetradecahedrons and dodecahedrons by tuning the precursor concentration from 0.05 M to 1.0 M and reaction conditions. Dodecahedrons with different size can be easily prepared by elongating the reaction time. These nanocrystals can be used as cathodes in all-vanadium redox flow batteries and showed a significant improvement of the cathodic reaction reversibility, especially the dodecahedrons.
The CuxSe nanocubes with mean edge length of 17 nm±0.9 nm were synthesized (Chapter 4). The role of various metal ions playing on shape of CuxSe nanocrystals was discussed during the synthesis. The underlying mechanism was illustrated by preparing copper selenide nanocubes in the presence of Al ions whereas there was no any Al detected on the surface or within the final cubes. The morphology control is proved to be thermodynamically directed during the ripening regime and it exemplified the shape-direction of semiconductor nanocrystals by metal ions for the first time. It is a platform to produce cubic nanoparticles with different composition by cation exchange such as Ag2Te nanocubes. The plasmonic properties of the obtained nanocubes were further characterized and it demonstrated the strong plasmonic absorption peak at 950 nm.
A reproducible procedure to prepare highly monodisperse copper telluride nanocubes, nanoplates and nanorods was presented in Chapter 5. The procedure is based on the reaction of a copper salt with trioctylphosphine telluride (TOP-Te) in the presence of Lithium bis(trimethylsilyl) amide (LiN(SiMe3)2), trioctylphosphine (TOP), trioctylphosphine oxide (TOPO) and oleylamine (OLA). The high reaction temperature as 220 °C was found to be necessary to obtain cube-shaped NPs with narrow size distributions. By tuning the precursor ratio of Cu:Te, the size of these nanocubes could be controlled in the range between 10 and 20 nm. When decreasing the reaction temperature to 190 °C and the growth time to 15 min, highly homogeneous copper telluride nanoplates were produced. An increase of the TOP concentration from 0.125 ml to 0.75 ml resulted in the formation of nanorods. It was proposed the LiN(SiMe3)2 to activate the formation of a Cu-oleylamido complex and it is the actual species reacting with TOP-Te. The Cu-oleyamido complexes and/or lithium oleylamine may play a key role stabilizing the NP surface during growth. Copper telluride nanocubes and nanoplates display a strong near-infrared optical absorption at 900nm associated to localized surface plasmon resonances. This plasmon resonance can be exploited for the design of surface-enhanced Raman scattering (SERS) sensors for unconventional optical probes such as nile red containing oxygen based functional groups. This is the first time using Cu-chalcogenide as probes for SERS application and demonstrates its potential interest in future. Preliminary analysis of the use of copper telluride nanocubes as cytotoxic and photothermal agents is also discussed herein.<br>Inicialment vam establir les condicions per preparar Cu(x)S. Com a mecanisme de creixement es va proposar el que es coneix amb el nom d’oriented attachment, en el qual els nanocristalls s’uneixen en una determinada orientació per formar altres formes més complexes. Establint les condicions en les quals es donava aquest mecanisme podíem produir nanocristalls de Cu2-xS amb un acurat control sobre la seva composició i/o forma, des de partícules esfèriques fins a nanopartícules en forma de disc o bé acanat amb partícules amb forma tetradecaèdríca o dodecaèdríca. Aquest control es va aconseguir simplement variant la concentració del precursor i les condicions de reacció.
El segon sistema que es va estudiar va ser la producció de nanocristalls de Cu(x)Se. En el nostre treball preteniem descobrir nous procediments per sintetitzar nanocristalls de Cu(x)Se controlant la seva morfologia. Es va descubrir que es podia controlar la forma final dels nanocristalls de Cu(x)Se simplement introduint ions metàl•lics a la solució. En particular, en presència d’ions d’alumini es van produir nanocubs amb una longitud lateral de 17 nm ± 0.9 nm. Addicionalment es van estudiar les propietats plasmòniques d’aquests nanocubs. També es van utilizar aquests cubs de seleniur de coure com a base per produir cubs d’altres semiconductors a travès de l’intercanvi catiònic. Com a exemple es van produir cubs de Ag(2)Te.
Finalment, es va estudiar el calcogenur binari, Cu(x)Te. Es va desenvolupar un mètode de síntesi per produïr nanocubs, nanoplaques i nanorods altament monodispersos. Es va observar que els paràmetres clau per controlar la forma eren la temperatura i la quantitat de surfactants. En canvi, per controlar el tamany es va observar que el paràmetre més important era la proporció entre Cu i Te present a la solució. Aquests nanocristalls posseïen propietats plasmòniques amb un pic d’absorpció al voltant dels 900 nm.
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Frey, Michael [Verfasser]. "Shape Calculus Applied to Elliptic Optimal Control Problems / Michael Frey." Bayreuth : Universität Bayreuth, 2012. http://d-nb.info/1059412780/34.
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Allwood, Julian Mark. "Online modelling and control and shape phenomena in metal rolling." Thesis, Imperial College London, 1993. http://hdl.handle.net/10044/1/7503.
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Sekouri, El Mostafa. "Modeling and shape estimation of smart structures for active control." Mémoire, Montréal : École de technologie supérieure, 2004. http://wwwlib.umi.com/cr/etsmtl/fullcit?pNQ90331.
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Thèse (Ph.D.)--École de technologie supérieure, Montréal, 2004.<br>"Thesis presented to the École de technologie supérieure in partial fulfillment of the thesis requirement for the degree of philosophy doctor in engineering". Bibliogr.: f. [158]-164. Également disponible en version électronique.
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Kristensson, Per Ola. "Discrete and Continuous Shape Writing for Text Entry and Control." Doctoral thesis, Linköping : Department of Computer and Information Science, Linköping University, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-8877.
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Cox, S. D. "Control of residual stress and shape in hot rolled coil." Thesis, Swansea University, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.636311.
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Unwanted distortion in the final strip product manufactured at Port Talbot is referred to as strip shape. The occurrence of shape defects in hot rolled coil is a recurring problem that is far from understood. The primary objective of this research programme was to develop a mathematical model to simulate the run-out table process in order to understand the formation of residual stress and shape in hot rolled coil resulting from the operation. The software tool developed to predict the final characteristics of the strip steel condition is comprised of several mathematical and finite element model components. Data from the plant measurement systems has been incorporated within the run-out table model to more accurately represent both the initial condition of the strip and the set-up of the manufacturing process. Experimental testing has been used to acquire data to describe the material behaviour for predictive calculations within the software tool. Furthermore, test data was obtained from the hot mill for validation of model components. Finally, plant trials were designed and performed in order to benchmark the performance of the model. The design eliminated any imposition of distortion in the samples from downstream processes and measurements of residual stress and shape defect levels in the samples were carried out using laboratory equipment. The results have proven a good level of accuracy in several components of the software tool. Consequently, a greater understanding of the run-out table operation has been achieved and is demonstrated by the recommendations for both future improvements to the process and related areas of research.
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Loboda, Gregory G. (Gregory George). "Performance enhancement of segmented infrared reflectors via quasistatic shape control." Thesis, Massachusetts Institute of Technology, 1992. http://hdl.handle.net/1721.1/17308.
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Borggrèafe, Andreas J. "Attitude dynamics and shape control of reflectivity modulated gossamer spacecraft." Thesis, University of Strathclyde, 2015. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=25809.
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The utilisation of space provides many opportunities to deliver pioneering innovations during the 21st century. One of these opportunities is the gossamer spacecraft, an emerging technology to achieve very low mass, large area and low stowage volume. Examples include large ultra-lightweight membrane reflectors and distributed tethered formations. Gossamer spacecraft offer the potential to deliver innovative new science and applications missions to aid our growing globalised societies: high-performing communications antennae, scientific telescopes and space-based solar power collectors. However, the ability to control such large structures in space is essential for their successful operation. To this aim, this thesis investigates a novel means to control large gossamer spacecraft by exploiting modulated solar radiation pressure (SRP), thus by modifying the nominal light pressure acting on the structure in space. Various concepts have been proposed in the past to control the attitude of a gossamer spacecraft, employing complex mechanical systems or thrusters. Furthermore, methods to control the surface shape of a large membrane reflector using, for example, piezoelectric actuators, are being developed. Since on-board control systems need to be high-performance, reliable and importantly lightweight, this thesis investigates the use of thin-film reflectivity control devices across the spacecraft surface. Controlling the reflectivity modulates the Sun's light pressure acting on a thin membrane thus controlling its shape. In addition, body forces and torques become available to control the attitude of such a large structure 'optically', without using traditional mechanical systems. The concept is demonstrated first by controlling a two-mass tethered formation in a Sun-centred orbit, showing that the spacecraft attitude can be stabilised around new equilibria created by controlling the surface reflectivity of the masses. Subsequently, the concept is applied to control the attitude of a large membrane reflector, which confirms the viability of reflectivity modulation by generating variable optical torques in the membrane plane. In particular, the nominal SRP forces are modified by introducing different surface reflectivity distributions across the membrane. It is shown that through these optical torques, the reflector can be steered, for example, to a Sunpointing attitude from an arbitrary initial displacement. The analysis also considers the variation of the SRP force magnitude with changing light incidence angle towards the Sun during the manoeuvre, thereby presenting solutions to a challenging attitude control problem. Furthermore, by adopting a highly-integrated multi-functional design approach, the concept of reflectivity modulation is also employed to control the surface shape of a large membrane reflector. First, the nominal (non-parabolic) deflection shapes due to uniform SRP across the surface are presented. Subsequently, a closed-form solut ion for the reflectivity function across the membrane required to create a true parabolic deflection shape is derived. In order to improve the quite large focal lengths of the deflected shapes that can be generated for a tensioned membrane, shape control of a slack suspended surface is also considered. The achievable (shorter) focal lengths support the feasibility of exploiting modulated SRP for controlled surface deflection. In summary, this thesis demonstrates the potential of using surface reflectivity modulation to control the attitude and morphology of large gossamer spacecraft without using complex mechanical systems or thrusters. Therefore, the concept of optical control represents a major step towards highly-integrated adaptive gossamer structures and supports the development of this promising key-technology to deliver advanced space applications.
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Santos, Filipe Pimentel Amarante dos. "Vibration control with shape-memory alloys in civil engineering structures." Doctoral thesis, Faculdade de Ciências e Tecnologia, 2011. http://hdl.handle.net/10362/5610.
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Dissertação apresentada à Faculdade de Ciências e Tecnologia da Universidade Nova de Lisboa para obtenção do grau de Doutor em Engenharia Civil<br>The superelastic behavior exhibited by shape-memory alloys shows a vast potential
for technological applications in the field of seismic hazard mitigation, for civil engineering structures. Due to this property, the material is able to totally recover from large cyclic deformations, while developing a hysteretic loop. This is translated into a high inherent damping, combined with repeatable re-centering capabilities, two fundamental features of vibration control devices.
An extensive experimental program provides a valuable insight into the identification
of the main variables influencing superelastic damping in Nitinol while exploring the feasibility and optimal behavior of SMAs when used in seismic vibration control.
The knowledge yielded from the experimental program, together with an extensive
bibliographic research, allows for the development of an efficient numerical framework for the mathematical modeling of the complex thermo-mechanical behavior of
SMAs. These models couple the mechanical and kinetic transformation constitutive laws with a heat balance equation describing the convective heat problem. The seismic
behavior of a superelastic restraining bridge system is successfully simulated,
being one of the most promising applications regarding the use of SMAs in civil
engineering structures.
A small-scale physical prototype of a novel superelastic restraining device is built.
The device is able to dissipate a considerable amount of energy, while minimizing a set of adverse effects, related with cyclic loading and aging effects, that hinder the dynamic performances of vibration control devices based on passive superelastic
wires.<br>Fundação Calouste Gulbenkian (bolsa de curta duração) and of Fundação para a Ciência e Tecnologia (FCT/MCTES grant SFRH/BD/37653/2007)
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Kandel, Shreedhar R. "Control of Shape Change of PbSe Nano Structure by Chloroalkane." Bowling Green State University / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1435056285.
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Jau-Iovec, Ana-Vanessa. "Using Shape to control the magnetization reversal in Ferromagnetic Nanostructures." Thesis, Imperial College London, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.499123.
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Martins, Daniel. "Vibration control on a tensegrity structure using shape memory alloys /." Bauru, 2019. http://hdl.handle.net/11449/183354.
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Orientador: Paulo José Paupitz Gonçalves<br>Banca: Marcos Silveira<br>Banca: Carlos de Marqui Junior<br>Resumo: Um sistema de tensegrity é composto por dois tipos de elementos, elementos de tração e compressão, os quais promovem a estabilidade estrutural do sistema, neste trabalho as partes de tração são cabos (cabos de aço), e as partes compressivas são barras de aço. Uma característica atrativa de uma estrutura de tensegridade é a capacidade de ser retrátil, por esta razão, é interessante para aplicações espaciais devido ao pequeno volume que ocupa um possível transporte para uma estação espacial. Em geral, essas estruturas podem ser grandes com muitas células repetitivas. Neste trabalho, estuda-se uma estrutura de tensegrity composta por dez células periódicas de barras e cabos. O modelo matemático, obtido pelo método dos elementos finitos, é validado experimentalmente considerando o caso de uma célula estrutural. Para tornar o sistema adaptável à excitação externa, um dos cabos de aço na célula elementar é substituído por um fio de liga de memória de forma (SMA) que permite que as características dinâmicas do sistema sejam alteradas de acordo com uma corrente elétrica aplicada no SMA, para que através do efeito Joule a liga seja aquecida. Diferentes configurações para a colocação do cabo SMA são estudadas com o objetivo de reduzir as amplitudes de vibração para uma excitação de força harmônica.<br>Abstract: A tensegrity system is composed by two types of elements, tensile and compressive parts, which promotes the structural stability of the system, in this case the tensile parts are cables (steel cables), and the compressive parts are bars, in this work made of steel. An attractive characteristic of a tensegrity structure is the capability to be deployable, for this reason, is interesting for space applications due to the small volume that it occupies in a possible transport to a station outside the Earth. In general, these structures can be large with many repetitive cells. In this work, a tensegrity boom structure consisting of ten periodic cells made of bars and cables is studied. The mathematical model, obtained by finite element method is validated experimentally considering the case of one structural cell. In order to make the system adaptable to external excitation, one of the steel cables in the elementary cell is replaced by a SMA (shape memory alloy) wire (Nitinol) allowing the dynamics characteristics of the system to be changed according to an electrical current applied to the SMA, to heat the alloy through Joule effect. Different configurations for placing the SMA cable are studied with the objective of reducing the vibration amplitudes for harmonic force excitation.<br>Mestre
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Tonomura, Osamu. "Shape Design and Operation of Microreactors." 京都大学 (Kyoto University), 2015. http://hdl.handle.net/2433/200473.
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Andres, George. "Shape Measurement System for Roller Levelers." Youngstown State University / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=ysu1432818521.
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Elahinia, Mohammad. "Effect of System Dynamics on Shape Memory Alloy Behavior and Control." Diss., Virginia Tech, 2004. http://hdl.handle.net/10919/11221.
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While the existing thermomechanical constitutive models can predict the behavior of SMA-actuated systems in most cases, in this study, we have shown that there are certain situations in which these models are not able to predict the behavior of SMAs. To this end, a rotary SMA-actuated robotic arm is modeled using the existing constitutive models. The model is verified against the experimental results to document that under certain conditions, the model is not able to predict the behavior of the SMA-actuated manipulator. Such cases most often occur when the temperature and stress of the SMA wire change simultaneously. The constitutive model discrepancy is also studied experimentally using a dead-weight that is actuated by an SMA wire. Subsequently, an enhanced phenomenological model is developed. The enhanced model is able to predict the behavior of SMAs under complex thermomechanical loadings. For the SMA-actuated robotic arm, several control methods are designed through simulations. A position-based PID controller is designed first, and it is found that this controller cannot perform well for all the desired angular positions(set-points). A Variable Structure Control (VSC) based on the angular position and velocity is presented that has a relatively better erformance for all the set-points. To improve the erformance of the VSC, in terms of the steady state error, an Extended Kalman Filter is designed and used to modify the VSC design. The modified VSC is based on the angular position and angular velocity of the actuator and the estimated temperature of the SMA wire. Furthermore, a Sliding Mode Controller is designed based on the stress of the SMA wire. Finally, a model-based Backstepping Controller is designed for the SMA-actuated arm. This model-bsed controller allows designing the controller parameters based on the parameters of the system. Additionally, the stability of the controller is studied. Using the Lyapunov stability analysis, it is shown that the model-based Backstepping Controller is able to asymptotically stabilize the system.<br>Ph. D.
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Schubert, Oliver John. "Distributed control of a segmented and shape memory alloy actuated biologically inspired robot." Thesis, Montana State University, 2005. http://etd.lib.montana.edu/etd/2005/schubert/SchubertO0805.pdf.
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Pi, Alexander 1978. "Effects of uncertainty on closed loop shape control in stretch forming." Thesis, Massachusetts Institute of Technology, 2002. http://hdl.handle.net/1721.1/89895.
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Salerno, Robert James. "Shape control of high degree-of-freedom Variable Geometry Truss manipulators." Thesis, Virginia Polytechnic Institute and State University, 1989. http://hdl.handle.net/10919/50089.
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Variable Geometry Trusses (VGT’s) can be used as the fundamental building blocks in constructing long-chain, high degree-of-freedom manipulators. This thesis focuses on the kinematics of two such manipulators. It also illustrates how the concept of shape control can be applied to simplify the computational aspects of controlling these devices. To serve as examples, algorithms are developed for the control of both a thirty degree of freedom planar manipulator and a sixty degree-of-freedom spatial manipulator. Based on a review of the literature, this work appears to be the first attempt to develop real-time, position control strategies for such highly-dexterous manipulators.<br>Master of Science<br>incomplete_metadata
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Lehmann, Alejandro. "Does Family Control Shape Diversification Decisions? : the Case of Chilean Firms." Tesis, Universidad de Chile, 2018. http://repositorio.uchile.cl/handle/2250/168311.
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TESIS/AFE PARA OPTAR AL GRADO DE MAGÍSTER EN FINANZAS<br>This paper analyses how family control affects diversification decision on Chilean firms, its
characteristics and limitations. Specifically, we introduce the potential agency frameworks such
as pyramidal ownership, family, or business groups, as determinants of corporate prevention
to diversify. From a dataset composed by 140 Chilean nonfinancial firms listed in the period 2008-
2015, we use an OLS method withed year-industry fixed effects. Results show that families tend
to diversify less than non-family companies. Nonetheless, they show higher compromise with
the segments already owned, showing a manifestation of the socioemotional wealth and the
resource-based approach. Interestingly, family firms under business groups or pyramidal
structures show positive tendencies to diversify, consistent with the wealth expropriation
theories.
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Laranjeira, Moreira Matheus. "Visual servoing on deformable objects : an application to tether shape control." Electronic Thesis or Diss., Toulon, 2019. http://www.theses.fr/2019TOUL0007.
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Cette thèse porte sur le problème du contrôle de la forme d'ombilicaux pour des robots sous-marins légers téléopérés (mini-ROVs), qui conviennent, grâce à leur petite taille et grande manoeuvrabilité, à l'exploration des eaux peu profondes et des espaces encombrés. La régulation de la forme de l'ombilical est cependant un tâche difficile, car ces robots n'ont pas une puissance de propulsion suffisante pour contrebalancer les forces de traînée du câble. Pour faire face à ce problème, nous avons introduit le concept de Cordée de mini-ROVs, dans lequel plusieurs robots sont reliés à l'ombilical et peuvent, ensemble, contrebalancer les perturbations extérieures et contrôler la forme du câble. Nous avons étudié l'utilisation des caméras embarquées pour réguler la forme d'une portion de l'ombilical reliant deux robots successifs, un leader et un suiveur. Seul le robot suiveur se chargera de la tâche de régulation de la forme du câble. Le leader est libéré pour explorer ses alentours. L'ombilical est supposé être légèrement pesant et donc modélisé par une chaînette. Les paramètres de forme du câble sont estimés en temps réel par une procédure d'optimisation non-linéaire qui adapte le modèle de chaînette aux points détectés dans les images des caméras. La régulation des paramètres de forme est obtenue grâce à une commande reliant le mouvement du robot à la variation de la forme de l'ombilical. L'asservissement visuel proposé s'est avéré capable de contrôler correctement la forme du câble en simulations et expériences réalisées en basin<br>This thesis addresses the problem of tether shape contrai for small remotely operated underwater vehicles (mini-ROVs), which are suitable, thanks to their small size and high maneuverability, for the exploration of shallow waters and cluttered spaces. The management of the tether is, however, a hard task, since these robots do not have enough propulsion power to counterbalance the drag forces acting on the tether cable. ln order to cape with this problem, we introduced the concept of a Chain of miniROVs, where several robots are linked to the tether cable and can, together, manage the external perturbations and contrai the shape of the cable. We investigated the use of the embedded cameras to regulate the shape of a portion of tether linking two successive robots, a leader and a follower. Only the follower robot deals with the tether shape regulation task. The leader is released to explore its surroundings. The tether linking bath robots is assumed to be negatively buoyant and is modeled by a catenary. The tether shape parameters are estimated in real-time by a nonlinear optimization procedure that fits the catenary model to the tether detected points in the image. The shape parameter regulation is thus achieved through a catenary-based contrai scheme relating the robot motion with the tether shape variation. The proposed visual servoing contrai scheme has proved to properly manage the tether shape in simulations and real experiments in pool
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Janzen, Frederic Conrad. "Positioning and vibration control of a flexible structure in slewing motion by applying Shape Memory Alloys /." Bauru, 2016. http://hdl.handle.net/11449/144649.
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Orientador: José Manoel Balthazar<br>Banca: Angelo Marcelo Tusset<br>Banca: Vinicius Piccirillo<br>Banca: Airton Nabarrete<br>Banca: Atila Madureira Bueno<br>Abstract: Flexible structures with slewing motion has been found with increasing frequency in various types of applications, because they are more efficient than their rigid competitors. The study of these systems is important because of the vibrations coming from the mass reduction of structures. Many works have been published presenting control techniques applied in reducing the effects of these vibrations. Several studies demonstrate the application of intelligent materials as actuators for this application. This paper presents a proposal for controlling the angular positioning and vibration of a flexible structure in slewing motion. For such compounds an intelligent actuator materials known as Shape Memory Alloy is employed to control the vibration of the flexible structure. To control the system, the control technique known as State Dependent Ricatti Equation (SDRE), is applied to the control. In order to analyse the dynamics of the system with the proposed control the mathematical modelling of the system is considered and its validation by developed an experimental prototype. Numerical simulations are carried out to analyse the viability of the control and experimental tests are performed in order to validate the theoretical model and the proposed control<br>Resumo: Estruturas flexíveis com movimento de rastreamento tem sido encontradas com frequências cada vez maior em diversos tipos de aplicações, por serem mais eficientes do que suas concorrentes rígidas. O estudo desses sistemas é importante por conta das vibrações advindas da redução de massa das estruturas. Muitos trabalhos têm sido publicados apresentando técnicas de controle aplicadas na redução dos efeitos dessas vibrações. Vários trabalhos demonstram a aplicação de materiais inteligentes como atuadores para esse tipo de aplicação. Sendo assim, o presente trabalho apresenta uma proposta para o controle do posicionamento angualar e da vibração de uma estrutura flexível em movimento de rastreamento. Para tal, atuadores compostos de um material inteligente conhecido como Liga com Memória de Forma são empregados para o controle da vibração da estrutura flexível. Com relação ao controle, a técnica de controle conhecida como Equações de Ricatti Dpenedentes dos Estados (SDRE) é aplicada para o controle. Com o objetivo de analisar a dinâmica do sistema como controle proposto considera-se a modelagem matemática do sistema e sua validação através do desenvolvido de um protótipo experimental. Simulações numéricas são realizadas para analisar a viabilidade do controle proposto e testes experimentais são realizados com a finalidade de validar o modelo teórico e a proposta de controle<br>Doutor
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Schenck, David Robert. "Some Formation Problems for Linear Elastic Materials." Diss., Virginia Tech, 1999. http://hdl.handle.net/10919/28608.
Full textAbstract:
Some equations of linear elasticity are developed, including those
specific to certain actuator structures considered in formation
theory. The invariance of the strain-energy under the transformation
from rectangular to spherical coordinates is then established for use
in two specific formation problems. The first problem, involving an
elastic structure with a cylindrical equilibrium configuration, is
formulated in two dimensions using polar coordinates. It is shown
that $L^2$ controls suffice to obtain boundary displacements in
$H^{1/2}$. The second problem has a spherical equilibrium
configuration and utilizes the elastic equations in spherical
coordinates. Results similar to those obtained in the two dimensional
case are indicated for the three dimensional problem.<br>Ph. D.
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Ponce, Cristobal. "Port-Hamiltonian modeling, discretization and shape control of multidimensional flexible mechanical systems." Electronic Thesis or Diss., Bourgogne Franche-Comté, 2024. http://www.theses.fr/2024UBFCD061.
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Cette thèse traite de la modélisation, de la discrétisation et du contrôle de forme des systèmes mécaniques flexibles dans le cadre des systèmes Port-Hamiltoniens (PHS). Les contributions sont triples. Tout d'abord, nous proposons des méthodologies généralisées pour la modélisation des systèmes mécaniques multidimensionnels, linéaires et non linéaires, en utilisant le principe de Hamilton généralisé et étendu, fournissant des représentations explicites et implicites des PHS. Ensuite, nous développons des techniques de discrétisation préservant la structure à travers des méthodes d'éléments finis mixtes (FEM), incluant des approches à deux, trois et quatre champs adaptées aux systèmes PHS et PH-DAE linéaires et non linéaires. Enfin, nous introduisons un contrôleur en dimension finie basé sur des approximations d'ordre faible de systèmes PHS linéaires discrétisés à grande échelle. Ce contrôleur garantit la convergence vers les formes optimales, offrant la meilleure approximation des configurations désirées, tout en assurant la stabilité asymptotique du système discrétisé à grande échelle<br>This thesis addresses the modeling, discretization, and shape control of flexible mechanical systems within the Port-Hamiltonian Systems (PHS) framework. The contributions are threefold. First, we propose generalized methodologies for modeling both linear and nonlinear multidimensional mechanical systems using the generalized extended Hamilton's principle, providing explicit and implicit PHS representations. Second, we develop structure-preserving discretization techniques via mixed Finite Element Methods (FEM), including two, three, and four-field approaches tailored to linear and nonlinear PHS and PH-DAE systems. Finally, we introduce a finite-dimensional controller based on low-order approximations of large-scale discretized linear PHS. This controller ensures convergence to the optimal shapes, offering the best approximation to the desired configurations, while guaranteeing asymptotic stability of the large-scale discretized system
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Veljović, Slobodan. "Shape optimization and optimal boundary control for high intensity focused ultrasound (HIFU)." Aachen Shaker, 2010. http://d-nb.info/1002144639/04.
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Chee, Clinton Yat Kuan. "STATIC SHAPE CONTROL OF LAMINATED COMPOSITE PLATE SMART STRUCTURE USING PIEZOELECTRIC ACTUATORS �." University of Sydney. Aeronautical Engineering, 2000. http://hdl.handle.net/2123/709.
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The application of static shape control was investigated in this thesis particularly for a composite plate configuration using piezoelectric actuators. A new electro-mechanically coupled mathematical model was developed for the analysis and is based on a third order displacement field coupled with a layerwise electric potential concept. This formulation, TODL, is then implemented into a finite element program. The mathematical model represents an improvement over existing formulations used to model intelligent structures using piezoelectric materials as actuators and sensors. The reason is TODL does not only account for the electro-mechanical coupling within the adaptive material, it also accounts for the full structural coupling in the entire structure due to the piezoelectric material being attached to the host structure. The other significant improvement of TODL is that it is applicable to structures which are relatively thick whereas existing models are based on thin beam / plate theories. Consequently, transverse shearing effects are automatically accounted for in TODL and unlike first order shear deformation theories, shear correction factors are not required. The second major section of this thesis uses the TODL formulation in static shape control. Shape control is defined here as the determination of shape control parameters, including actuation voltage and actuator orientation configuration, such that the structure that is activated using these parameters will conform as close as possible to the desired shape. Several shape control strategies and consequently algorithms were developed here. Initial investigations in shape control has revealed many interesting issues which have been used in later investigations to improve shape controllability and also led to the development of improved algorithms. For instance, the use of discrete actuator patches has led to greater shape controllability and the use of slopes and curvatures as additional control criteria have resulted in significant reduction in internal stresses. The significance of optimizing actuator orientation and its relation to piezoelectric anisotropy in improving shape controllability has also been presented. Thus the major facets of shape control has been brought together and the algorithms developed here represent a comprehensive strategy to perform static shape control.
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Dorfs, Dirk [Verfasser]. "Advanced shape, composition, and property control in colloidal nanocrystal synthesis / Dirk Dorfs." Hannover : Gottfried Wilhelm Leibniz Universität, 2018. http://d-nb.info/1172414203/34.
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Jordan, Elizabeth (Elizabeth O. ). "Design and shape control of lightweight mirrors for dynamic performance and athermalization." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/39705.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2007.<br>Includes bibliographical references (p. 121-124).<br>The next generation of space telescopes will need to meet increasingly challenging science goals. For these new systems to meet resolution goals, the collecting area of the primary mirror will need to be increased. However, current space telescope designs are reaching their limits in terms of size and mass. Therefore, new systems will need to include technologies such as lightweight mirrors, segmented or sparse apertures and active optical control. Many of these technologies have no flight heritage, so determining what combinations of technologies will create favorable designs requires detailed modeling and analysis. This thesis examines the design of a lightweight mirror for an advanced space telescope for both dynamic performance and shape control. A parametric model of a rib-stiffened mirror is created in order to quickly analyze many different mirror geometries. This model is used to examine the homogeneous dynamics of the mirror to determine what geometry will maximize the ratio of stiffness to areal density. The mirror model is then used in a full dynamic disturbance-to-performance analysis so that system performance can be examined as a function of changes in the mirror geometry.<br>(cont.) Next, a quasi-static shape control algorithm is developed to control the mirror using in the presence of thermal disturbances. The traditional method of mirror shape control relies on feedback from 'a wavefront sensor in the optical path. A wavefront sensor reduces the amount of light available for image formation, which causes problems when viewing very dim objects. Therefore, this control algorithm uses feedback from sensors embedded in the primary mirror. Control algorithms using both strain gages and temperature sensors are developed and compared to determine which sensor type results in better performance. The shape control algorithm with temperature sensors is analyzed using the parametric rib-stiffened mirror model to determine what geometries are best for shape control. The dynamic analysis is combined with the thermal control analysis in order to determine what mirror geometries will be favorable for both of these problems.<br>by Elizabeth Jordan.<br>S.M.
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Lovegrove, Bridget Sarah. "Genetic control of cell shape changes and cell rearrangements during Drosophila morphogenesis." Thesis, University of Cambridge, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.614789.
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Lord, David Allan. "Power applied to purpose : environmental control and the shape of modern architecture." Thesis, University College London (University of London), 1987. http://discovery.ucl.ac.uk/10062867/.
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The idea is developed that environmental control systems - lighting, heating, ventilation and acoustics - are elements of architectural meaning with strong links to the shape of buildings. The resulting architecture of the well-tempered environment is aesthetic and semantic as well as functional and technologicaL Lyrical and technical elements of well-tempered architecture are examined and the origin of environmental tempering in Western culture is traced. The study begins with classical Greek and Roman examples, continuing with folk traditions and the development of the science of architecture. In each instance, building types are described which illustrate the impact of environmental tempering techniques and functions on the shape of architecture. Classical examples include the Roman villa, bath and theatre. Later building types are prisons, hospitals, factories, theatres and galleries. Thus, a repertoire of climatically responsive forms is examined. The idiom is illustrated during the Modern era by the designs of four architects -- Frank Lloyd Wright, Le Corbusier, Alvar Aalto and Louis I. Kahn. Their works mark a zenith in the integration of architectural form with environmental tempering. The final chapter surveys the architecture of environmental tempering since the Modern Movement, including Regionalist, LateModernist, High-Tech and Post-Modernist examples. The conclusion proposes a definition of an architecture based on the art and science of environmental tempering.
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Liu, Suqi. "Droplet-jet shape in electrospinning: real-time feedback control of nanofiber diameter." University of Akron / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=akron1573221625942164.
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Calchand, Nandish Rajpravin. "Modeling and control of magnetic shape memory alloys using port hamiltonian framework." Thesis, Besançon, 2014. http://www.theses.fr/2014BESA2074/document.
Full textAbstract:
Les matériaux actifs sont des matériaux qui réagissent quand on leur applique un champ extérieur comme la température, la lumière, un champ magnétique ou un champ électrique. Ces champs changent les propriétés du matériau comme la longueur, la susceptibilité magnétique ou la permittivité électrique. Ces changements peuvent être utilisé pour faire du travail. Quelques exemples sont les matériaux piézoélectriques, qui changent de longueur quand on applique un champ électrique, les alliages à mémoire de forme qui changent leur longueur sous l’action de la température. Un matériau plus récent qu’on appelle les alliages mémoire de forme magnétique se de forme sous l’action d’un champ magnétique. Dans cette thèse, on utilise ce matériau pour Confectionner un actionneur. Pour ce faire, on utilise la thermodynamique des procédés irréversibles pour modéliser le matériau. La thermodynamique s’avère très versatile pour ce type de matériau car il permet de quantifier l’ échange et la transformation d’ énergie dans le matériau. Aussi, étant donné que le matériau se comporte d’une façon non-linéaire et hystérique, le cadre énergétique nous permets justement de prendre en compte ces non- linearités. Cette thèse utilise l’approche énergétique notamment les Hamiltonien à ports pour modéliser un actionneur à base d’alliage à mémoire de forme. Cette méthode nous permets aussi de concevoir des lois de commande pour contrôler le matériau<br>Active materials are a class of material which react to an external stimulus such as temperature,photons, magnetic field or electric field. These stimuli cause some properties of the material tochange usually their length. Some examples are piezoelectric material which change their lengthunder the action of an electric field, Shape Memory alloys which alter their shape on applicationof heat, and more recently Magnetic Shape Memory Alloys (MSMA) which undergo a deformationon application of a magnetic field. Harnessing this property of MSMAs, we hereby present anactuator using this novel material. We extensively make use of an energy framework, namely thethermodynamics of irreversible processes to model the material. This framework has been provento be very versatile in modelling energy exchange and transformation as it occurs in the materialand also to incorporate hysteresis which arises naturally in such materials. Another advantage of thismethod is its ability to give us constitutive laws based on simple assumptions. Furthermore, usingan energy framework allows us to apply some energy based control. Port Hamiltonian Control is onesuch method and it is not limited only to linear models. This latter characteristic has proven veryuseful since MSMAs are very non-linear in nature
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Nguyen, Van Ky Quan. "PIEZOELECTRIC ACTUATOR DESIGN OPTIMISATION FOR SHAPE CONTROL OF SMART COMPOSITE PLATE STRUCTURES." Thesis, The University of Sydney, 2005. http://hdl.handle.net/2123/652.
Full textAbstract:
Shape control of a structure with distributed piezoelectric actuators can be achieved through optimally selecting the loci, shapes and sizes of the piezoelectric actuators and choosing the electric fields applied to the actuators. Shape control can be categorised as either static or dynamic shape control. Whether it is a transient or gradual change, static or dynamic shape control, both aim to determine the loci, sizes, and shapes of piezoelectric actuators, and the applied voltages such that a desired structural shape is achieved effectively. This thesis is primarily concerned with establishing a finite element formulation for the general smart laminated composite plate structure, which is capable to analyse static and dynamic deformation using non-rectangular elements. The mechanical deformation of the smart composite plate is modelled using a third order plate theory, while the electric field is simulated based on a layer-wise theory. The finite element formulation for static and dynamics analysis is verified by comparing with available numerical results. Selected experiments have also been conducted to measure structural deformation and the experimental results are used to correlate with those of the finite element formulation for static analysis. In addition, the Linear Least Square (LLS) method is employed to study the effect of different piezoelectric actuator patch pattern on the results of error function, which is the least square error between the calculated and desired structural shapes in static structural shape control. The second issue of this thesis deals with piezoelectric actuator design optimisation (PADO) for quasi-static shape control by finding the applied voltage and the configuration of piezoelectric actuator patch to minimise error function, whereas the piezoelectric actuator configuration is defined based on the optimisation technique of altering nodal coordinates (size/shape optimisation) or eliminating inefficient elements in a structural mesh (topology optimisation). Several shape control algorithms are developed to improve the structural shape control by reducing the error function. Further development of the GA-based voltage and piezoelectric actuator design optimisation method includes the constraint handling, where the error function can be optimised subjected to energy consumption or other way around. The numerical examples are presented in order to verify that the proposed algorithms are applicable to quasi-static shape control based on voltage and piezoelectric actuator design optimisation (PADO) in terms of minimising the error function. The third issue is to use the present finite element formulation for a modal shape control and for controlling resonant vibration of smart composite plate structures. The controlled resonant vibration formulation is developed. Modal analysis and LLS methods are also employed to optimise the applied voltage to piezoelectric actuators for achieving the modal shapes. The Newmark direct time integration method is used to study harmonic excitation of smart structures. Numerical results are presented to induce harmonic vibration of structure with controlled magnitude via adjusting the damping and to verify the controlled resonant vibration formulation.
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Nguyen, Van Ky Quan. "PIEZOELECTRIC ACTUATOR DESIGN OPTIMISATION FOR SHAPE CONTROL OF SMART COMPOSITE PLATE STRUCTURES." University of Sydney. Aerospace, Mechanical and Mechatronic, 2005. http://hdl.handle.net/2123/652.
Full textAbstract:
Shape control of a structure with distributed piezoelectric actuators can be achieved through optimally selecting the loci, shapes and sizes of the piezoelectric actuators and choosing the electric fields applied to the actuators. Shape control can be categorised as either static or dynamic shape control. Whether it is a transient or gradual change, static or dynamic shape control, both aim to determine the loci, sizes, and shapes of piezoelectric actuators, and the applied voltages such that a desired structural shape is achieved effectively. This thesis is primarily concerned with establishing a finite element formulation for the general smart laminated composite plate structure, which is capable to analyse static and dynamic deformation using non-rectangular elements. The mechanical deformation of the smart composite plate is modelled using a third order plate theory, while the electric field is simulated based on a layer-wise theory. The finite element formulation for static and dynamics analysis is verified by comparing with available numerical results. Selected experiments have also been conducted to measure structural deformation and the experimental results are used to correlate with those of the finite element formulation for static analysis. In addition, the Linear Least Square (LLS) method is employed to study the effect of different piezoelectric actuator patch pattern on the results of error function, which is the least square error between the calculated and desired structural shapes in static structural shape control. The second issue of this thesis deals with piezoelectric actuator design optimisation (PADO) for quasi-static shape control by finding the applied voltage and the configuration of piezoelectric actuator patch to minimise error function, whereas the piezoelectric actuator configuration is defined based on the optimisation technique of altering nodal coordinates (size/shape optimisation) or eliminating inefficient elements in a structural mesh (topology optimisation). Several shape control algorithms are developed to improve the structural shape control by reducing the error function. Further development of the GA-based voltage and piezoelectric actuator design optimisation method includes the constraint handling, where the error function can be optimised subjected to energy consumption or other way around. The numerical examples are presented in order to verify that the proposed algorithms are applicable to quasi-static shape control based on voltage and piezoelectric actuator design optimisation (PADO) in terms of minimising the error function. The third issue is to use the present finite element formulation for a modal shape control and for controlling resonant vibration of smart composite plate structures. The controlled resonant vibration formulation is developed. Modal analysis and LLS methods are also employed to optimise the applied voltage to piezoelectric actuators for achieving the modal shapes. The Newmark direct time integration method is used to study harmonic excitation of smart structures. Numerical results are presented to induce harmonic vibration of structure with controlled magnitude via adjusting the damping and to verify the controlled resonant vibration formulation.
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Borsos, Akos. "Modelling and control of crystal purity, size and shape distributions in crystallization processes." Thesis, Loughborough University, 2017. https://dspace.lboro.ac.uk/2134/25478.
Full textAbstract:
Crystallization is a key unit operation used for obtaining purified products by many process industries. The key properties of the crystalline products, such as size and shape distribution, purity and polymorphic form are controlled by the crystallization process. All these properties impact significantly the downstream operations such as drying or filtration. Therefore, monitoring and controlling this process is fundamental to ensure the quality of the final product. Process analytical technology (PAT) brings numerous new methods and opportunities in the process analytics and real time process monitoring systems, which can be integrated into the control algorithm and provide high level optimal control strategies as well as deeper understanding of the process. Process monitoring helps develop mathematical models which can, in one hand, help in better understanding the processes and consecvently the development and application of advanced control methods in order to achieve better product quality. In this work, image processing and image analysis based direct nucleation control (IA-DNC) is developed in order to investigate the evolution of the crystal properties, such as crystal size, and crystal shape distribution. The IA-DNC approach is also compared to alternative DNC techniques, in which particle number were measured by Focused Beam Reflectance Measurement (FBRM) in order to control crystal size. A control approach is introduced that control the nucleation and disappearance of crystals during cooling and heating segments related to the changes of the number of counts (measured by Particle Vision Measurment, so called PVM or combination of FBRM and PVM). The approach was applied to investigate crystallization of compounds with different behavior: potassium dihydrogen phosphate (KDP) water, contaminated KDP -water and Ascorbic acid water systems. The results demonstrate the application of imaging technique for model-free feedback control for tailoring crystal product properties. The second main aim of the thesis is to investigate and control crystallization processes in impure media in the presence of multiple impurities, with an impact on the crystal shape via growth kinetics. The broad impact of the crystal growth modifiers (impurities) on the growth kinetics is observed in real time by using in situ video imaging probe and real-time image analysis. A morphological population balance model is developed, which incorporates a multi-site, competitive adsorption mechanism of the impurities on the crystal faces. The kinetic parameters of primary nucleation, growth and impurity adsorption for a model system of potassium dihydrogen phosphate crystallization in water in the presence of two impurities, were estimated and validated with experimental results. It was demonstrated that the model can be used to describe the dynamic evolution of crystal properties, such as size and aspect ratio during crystallization for different impurity profiles in the system. Manual, feedback and hybrid feedback-feedforward control techniques are developed and investigated numerically for continuous processes, while model-based and model-free control approach for crystal shape are developed for batch processes. The developed morphological population balance model is implemented and applied in the model-based control approaches, which are suitable to describe multicomponent adsorption processes and their influence on the crystal shape. Case studies show the effectiveness of crystal growth modifiers based shape control techniques. Comparison of different control approaches shows the effectiveness of the techniques. The third part of the thesis deals with purification of crystals when adsorption of impurities on crystal surfaces and its incorporation into crystals are considered. A purification method, called competitive purity control (CPC) is proposed and investigated. A morphological population balance model, including nucleation, growth and competitive impurity adsorption kinetics is developed to describe the case when multiple impurities can adsorb competitively on the crystal surface. The model is also combined with liquid phase chemical reaction model, in order to investigate the purity control case when an additive is introduced in the system that reacts with the impurity forming a non-adsorbing reaction product. Both competitive purity control approaches proposed: the adsorption based competitive purity control (A-CPC) and the reaction based competitive purity control (R-CPC); are investigated using detailed numerical simulations then compared with the alternative widely used purification method, called recrystallization. In the last contribution chapter, an integrated process optimization of a continuous chemical reactor and crystallizer is performed and studied numerically. The purpose of this study is to show the way in which the byproduct produced in the chemical reactor may affect the crystallization process and how its negative effect can be reduced by applying integrated process optimization. Sensitivity analysis of the system was performed by considering the flow rate and the concentration of substances in the input stream of the chemical reactor as manipulated process variables. Model based integrated process optimization and the sensitivity analysis in order to obtain improved quality product in terms of crystal size, shape and purity.