Dissertations / Theses on the topic 'Smart structures'
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Sinn, Thomas. "Smart deployable space structures." Thesis, University of Strathclyde, 2016. http://digitool.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=28327.
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Nowadays, space structures are often designed to serve only a single objective during their mission life, examples range from solar sail for propulsion over shields for protection to antennas and reflectors for communication and observation. By enabling a structure to deploy and change its shape to adapt to different mission stages, the flexibility of the spacecraft can be greatly increased while significantly decreasing the mass and the volume of the system. Inspiration was taken from nature. Various plants have the ability to follow the sun with their flowers or leaves during the course of a day via a mechanism known as heliotropism. This mechanism is characterized by the introduction of pressure gradients between neighboring motor cells in the plant’s stem,enabling the stem to bend. By adapting this bio-inspired mechanism to mechanical systems, a new class of smart deployable structures can be created. The shape change of the full structure can be significant by adding up these local changes induced by the reoccurring cell elements. The structure developed as part of this thesis consists of an array of interconnected cells which are each able to alter their volume due to internal pressure change. By coordinated cell actuation in a specific pattern, the global structure can be deformed to obtain a desired shape. A multibody code was developed which constantly solves the equation of motion with inputs from internal actuation and external perturbation forces. During the inflation and actuation of the structure, the entities of the mass matrix and the stiffness matrix are changed due to changing properties of the cells within the array based on their state and displacement. This thesis will also give an overview of the system architecture for different missions and shows the feasibility and shape changing capabilities of the proposed design with multibody dynamic simulations. Furthermore, technology demonstrator experiments on stratospheric balloons and sounding rockets have been carried out to show the applicability and functionality of the developed concepts.
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McHenry, John T. "Multicomputer networks for smart structures." Diss., Virginia Tech, 1993. http://hdl.handle.net/10919/40053.
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Gharibnezhad, Fahit. "Robust damage detection in smart structures." Doctoral thesis, Universitat Politècnica de Catalunya, 2014. http://hdl.handle.net/10803/277544.
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This thesis is devoted to present some novel techniques in Structural Health Monitoring (SHM). SHM is a developing field that tries to monitor structures to make sure that they remain in their desired condition to avoid any catastrophe. SHM includes different levels from damage detection area to prognosis field. This work is dedicated to the first level, which might be considered the main and most important level. New techniques presented in this work are based on different statistical and signal processing methods such as Principal Component Analysis and its robust counterpart, Wavelet Transform, Fuzzy similarity, Andrew plots, etc. These techniques are applied on the propagated waves that are activated and captured in the structure using appropriate transducers. Piezoceramic (PZT) devices are chosen in this work to capture the signals due to their special characteristics such as high performance, low energy consumption and reasonable price. To guarantee the efficiency of the suggested techniques, they are tested on different laboratory and real scale test benchmarks, such as aluminum and composite plates, fuselage, wing skeleton, tube, etc. Because of the variety of tested benchmarks, this thesis is called damage detection in smart structures. This variety may promise the ability and capability of the proposed methods on different fields such as aerospace and gas/oil industry. In addition to the normal laboratory conditions, it is shown in this work that environmental changes can affect the performance of the damage detection and wave propagation significantly. As such, there is a vital need to consider their effect. In this work, temperature change is chosen as it is one of the main environmental fluctuation factors. To scrutinize its effect on damage detection, first, the effect of temperature is considered on wave propagation and then all the proposed methods are tested to check whether they are sensitive to temperature change or not. Finally, a temperature compensation method is applied to ensure that the proposed methods are stable and robust even when structures are subjected to variant environmental conditions.La presente tesis doctoral se dedica a la exploración y presentación de técnicas novedosas para la Monitorización y detección de defectos en estructuras (Structural Health Monitoring -SHM-) SHM es un campo actualmente en desarrollo que pretende asegurarse que las estructuras permanecen en su condición deseada para evitar cualquier catástrofe. En SHM se presentan diferentes niveles de diagnóstico, Este trabajo se concentra en el primer nivel, que se considera el más importante, la detección de los defectos. Las nuevas técnicas presentadas en esta tesis se basan en diferentes métodos estadísticos y de procesamiento de señales tales como el Análisis de Componentes Princpales (PCA) y sus variaciones robustas, Transformada wavelets, lógica difusa, gráficas de Andrew, etc. Estas técnicas de aplican sobre las ondas de vibración que se generan y se miden en la estructura utilizando trasductores apropiados. Dispositivos piezocerámicos (PZT's) se han escogido para este trabajo ya que presentan características especiales tales como: alto rendimiento, bajo consumo de energia y bajo costo. Para garantizar la eficacia de la metodología propuesta,se ha validado en diferentes laboratorios y estructuras a escala real: placas de aluminio y de material compuesto, fuselage de un avión, revestimiento del ala de un avóin, tubería, etc. Debido a la gran variedad de estructuras utilizadas, su aplicación en la industria aeroespacial y/o petrolera es prometedora. Por otra parte, los cambios ambientales pueden afectar al rendimiento de la detección de daños y propagación de la onda significativamente . En este trabajo , se estudia el efecto de las variaciones de temperatura ya que es uno de los principales factores de fluctuación del medio ambiente . Para examinar su efecto en la detección de daños, en primer lugar, todos los métodos propuestos se prueban para comprobar si son sensibles a los cambios de temperatura o no. Finalmente , se aplica un método de compensación de temperatura para garantizar que los métodos propuestos son estables y robustos incluso cuando las estructuras se someten a condiciones ambientales variantes
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Ulker, Fatma Demet. "Active Vibration Control Of Smart Structures." Master's thesis, METU, 2003. http://etd.lib.metu.edu.tr/upload/4/1098409/index.pdf.
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The purpose of this thesis was to design controllers by using H1 and ¹control strategies in order to suppress the free and forced vibrations of smart structures. The smart structures analyzed in this study were the smart beam and the smart ¯
n. They were aluminum passive structures with surface bonded PZT (Lead-Zirconate-Titanate) patches. The structures were considered in clamped-free con¯
guration. The ¯
rst part of this study focused on the identi¯
cation of nominal system models of the smart structures from the experimental data. For the experimentally identi¯
ed models the robust controllers were designed by using H1 and ¹
-synthesis strategies. In the second part, the controller implementation was carried out for the suppression of free and forced vibrations of the smart structures. Within the framework of this study, a Smart Structures Laboratory was established in the Aerospace Engineering Department of METU. The controller implementations were carried out by considering two di®
erent experimental set-ups. In the ¯
rst set-up the controller designs were based on the strain measurements. In the second approach, the displacement measurements, which were acquired through laser displacement sensor, were considered in the controller design. The ¯
rst two °
exural modes of the smart beam were successfully controlled by using H1 method. The vibrations of the ¯
rst two °
exural and ¯
rst torsional modes of the smart ¯
n were suppressed through the ¹
-synthesis. Satisfactory attenuation levels were achieved for both strain measurement and displacement measurement applications.
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Hadjiprocopiou, Marios. "Fibre optic sensors for smart structures." Thesis, University of Surrey, 1997. http://epubs.surrey.ac.uk/842922/.
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"Smart Structures" or "Smart Skins" will require structurally integrated sensing systems that can operate in practical situations. Optical sensing techniques are receiving considerable attention for the monitoring of such systems. Single ended polarimetric sensors were utilized with a large dynamic range for strain measurements as surface mounted and embedded strain sensors in composite materials (glass fibre and carbon fibre reinforced polymers). They were also used to monitor the strain and the formation of microcracks in the glue line of carbon fibre reinforced polymer (CFRP) concrete beams. The intrinsic Fabry-Perot was also used as a surface mounted sensor to monitor axial strain of GFRP coupons. Finite Element (FE) modelling was used in order to investigate the stress/strain distributions within the composite material and the embedded optical fibre. The modelling results show excellent agreement with the experimental results and suggest that the soft acrylate coating is debonding, thus reducing the sensor's dynamic range. Actuators and/or Sensors embedded into a host material will disrupt the physical properties of the host. Finite element analysis was used to determine and to minimise the stress concentrations which arise in a "Smart" material system due to the embedded optical fibre sensor. A parametric study was undertaken to determine the theoretical mechanical and thermal properties of the interface coating that minimises the disruption of the polymer composite host material properties due to the optical fibre inclusion. The effects of transverse tensile and thermal loading were studied, and also the residual thermal stress concentrations due to the manufacturing process were taken into consideration. The stress concentrations in the composite host are affected by the dimensions, mechanical and thermal properties of the interface coating. The results show that with careful selection of the interface coating properties die stress concentrations in the host material caused by the optical fibre inclusion can be reduced and be similar to those of the pure host material.
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Zhang, Jiaying. "Reconfiguring smart structures using approximate heteroclinic connections." Thesis, University of Strathclyde, 2017. http://digitool.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=29529.
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The term smart structures is commonly used to describe structures which have the ability to actively change their geometry or mechanical properties. Potential applications can be found in the aerospace, energy and marine sectors, e.g. use of MEMS-type devices which require frequent switching of compliant components and morphing of advanced aerofoils to generate additional lift. Traditional reconfigurable smart structures are designed with multi-stable characteristics. In particular, such structures can use stored strain energy to enable motion from one stable position to another stable position. However, the means of reconfiguring smart structures between stable con-figurations requires the input of, and then dissipation of energy to cross the potential barrier separating the stable configurations. Therefore, the accumulated work done for frequently actuated devices in reconfiguring between stable states can be significant. Considering reconfigurable smart structures for power and energy constrained applications, this thesis investigates a novel concept of reconfiguring smart structures between unstable states. The vision is to take advantage of modern dynamical system theory to develop entirely new devices that use the instability of mechanical systems to deliver energy-efficient shape-changing structures. This thesis indicates that theoretically in a simple model, transitioning between unstable states (so-called heteroclinic connections) can be more energy-efficient than traditional structures which transition between stable states and so need to cross a potential barrier. However, further experimental work will be required to verify this initial finding for real engineering systems. Clearly, energy is required to stabilize the unstable configurations, but if the energy required for active control of the instability is sufficiently small, or devices need to be frequently switched between different states, this concept is likely to be of benefit. The concept of using instability for reconfiguration is demonstrated first by controlling a mass-spring chain model through a simple cubic nonlinearity, which is sufficient to provide the required qualitative behaviour of the system. A sufficiently smooth set of functions is then used to generate a path to approximate the heteroclinic connection, which is then used as reference trajectory for reconfiguring between different unstable configurations. Moreover, the model is extended to a smart surface as a two-dimensional spring-mass array without dissipation. It is shown that the activere configuration scheme can be used to connect equal-energy unstable (but actively controlled) configurations for the purpose of energy-efficient morphing of the smart surface. However, in consideration of the difference between the cubic and real spring model, a spring-mass model with fully geometric non-linearity is also developed to verify the possibility of using heteroclinic connections to reconfigure future real smart structures. Furthermore, by considering a compliant mechanism, the concept of reconfiguration of a four-bar mechanism using heteroclinic connections is also investigated. Different models varying from fully rigid to purely elastic are employed to be controlled for reconfiguring between different unstable configurations. In addition, a continuous buckled beam model has been investigated with its characteristics based on the Euler-Bernoulli beam theory. An experimental beam was fabricated with shape memory alloy actuators for active control. Although the shape memory alloy was a slow response to time, it illustrates the possibility of reconfiguration of smart structures by using heteroclinic connections. In summary, this thesis demonstrates the potential of using heteroclinic connection to reconfigure smart structures with both numerical investigation and experimental validation. This entirely new approach to smart structures offers potentially significant benefits for power and energy constrained applications which require frequent reconfiguration.
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Vigilante, Domenico. "Numerical study of two-dimensional smart structures." Thesis, Virginia Tech, 2002. http://hdl.handle.net/10919/42706.
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In this thesis we use a new numerical code, based upon a mixed FEM-Runge-Kutta method, for the analysis and the design of plane 2-dimensional smart structures. We applied the developed code to the study of arbitrarily shaped piezo-electromechanical (PEM) plates. This code is based on a weak formulation of their governing equations as found in [18]. The optimal parameters needed to synthesize the appropriate electric networks are computed, and the overall performances of such plates are investigated. In particular, two examples are studied: firstly, a simple case is used to test the main features of the code; secondly, a more complex PEM plate is designed and analyzed by means of the proposed numerical approach.Master of Science
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Blanc, Arthur. "Control of Sound Radiation From Structures with Periodic Smart Skins." Thesis, Virginia Tech, 2001. http://hdl.handle.net/10919/35080.
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An innovative implementation of the skin concept for the reduction of the radiated sound power from a vibrating structure is proposed. The skin has a periodic structure and continuously covers a vibrating beam. Thus, this skin decouples the vibrating structure from the acoustic field by modifying the wavenumber spectrum of the radiating surface. First, structural acoustics and periodic structure theories are reviewed in order to predict how bending waves propagate along a periodic beam and how this beam radiates sound. These theories are then extended to the case of multi-layered structures in order to understand the behavior of a beam loaded with a periodic skin. In order to design the beam and skin structural periods, two different methods are used: Galois sequences and an optimization process using a real-valued genetic algorithm. Simulations are run for the case of periodic beams and beams coupled with periodic smart skins in both finite and infinite configurations. Results show that periodic beam can radiate less sound than equivalent uniform structures. Results also show the potential of periodic skin for application to the structural radiation problem for frequencies higher than approximately 100Hz with an approximately 10dB of radiated sound power attenuation.Master of Science
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Riddle, Brian K. "General purpose, data driven, extensible, computer interface for smart sensors." Thesis, Georgia Institute of Technology, 1994. http://hdl.handle.net/1853/18920.
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Eastep, Jonathan M. (Jonathan Michael). "Smart data structures : an online machine learning approach to multicore data structures." Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/65967.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2011.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student submitted PDF version of thesis.
Includes bibliographical references (p. 175-180).
As multicores become prevalent, the complexity of programming is skyrocketing. One major difficulty is eciently orchestrating collaboration among threads through shared data structures. Unfortunately, choosing and hand-tuning data structure algorithms to get good performance across a variety of machines and inputs is a herculean task to add to the fundamental difficulty of getting a parallel program correct. To help mitigate these complexities, this work develops a new class of parallel data structures called Smart Data Structures that leverage online machine learning to adapt themselves automatically. We prototype and evaluate an open source library of Smart Data Structures for common parallel programming needs and demonstrate signicant improvements over the best existing algorithms under a variety of conditions. Our results indicate that learning is a promising technique for balancing and adapting to complex, time-varying tradeoffs and achieving the best performance available.
by Jonathan M. Eastep.
Ph.D.
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Maillard, Julien. "Advanced Time Domain Sensing For Active Structural Acoustic Control." Diss., Virginia Tech, 1997. http://hdl.handle.net/10919/30335.
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Active control of sound radiation from vibrating structures has been an area of much research in the past decade. In Active Structural Acoustic Control (ASAC), the minimization of sound radiation is achieved by modifying the response of the structure through structural inputs rather than by exciting the acoustic medium (Active Noise Control, ANC). The ASAC technique often produces global far-field sound attenuation with relatively few actuators as compared to ANC. The structural control inputs of ASAC systems are usually constructed adaptively in the time domain based on a number of error signals to be minimized. One of the primary concerns in active control of sound is then to provide the controller with appropriate ``error'' information. Early investigations have implemented far-field microphones, thereby providing the controller with actual radiated pressure information. Most structure-borne sound control approaches now tend to eliminate the use of microphones by developing sensors that are integrated in the structure. This study presents a new sensing technique implementing such an approach. A structural acoustic sensor is developed for estimating radiation information from vibrating structures. This technique referred to as Discrete Structural Acoustic Sensing (DSAS) provides time domain estimates of the radiated sound pressure at prescribed locations in the far field over a broad frequency range. The structural acoustic sensor consists of a set of accelerometers mounted on the radiating structure and arrays of digital filters that process the measured acceleration signals in real time. The impulse response of each filter is constructed from the appropriate radiation Green's function for the source area associated with each accelerometer.
Validation of the sensing technique is performed on two different systems: a baffled rectangular plate and a baffled finite cylinder. For both systems, the sensor is first analyzed in terms of prediction accuracy by comparing estimated and actual sound pressure radiated in the far field. The analysis is carried out on a numerical model of the plate and cylinder as well as on the real structures through experimental testing. The sensor is then implemented in a broadband radiation control system. The plate and cylinder are excited by broadband disturbance inputs over a frequency range encompassing several of the first flexural resonances of the structure. Single-sided piezo-electric actuators provide the structural control inputs while the sensor estimates are used as error signals. The controller is based on the filtered-x version of the adaptive LMS algorithm. Results from both analytical and experimental investigations are again presented for the two systems. Additional control results based on error microphones allow a comparison of the two sensing approaches in terms of control performance.
The major outcome of this study is the ability of the structural acoustic sensor to effectively replace error microphones in broadband radiation control systems. In particular, both analytical and experimental results show the level of sound attenuation achieved when implementing Discrete Structural Acoustic Sensing rivaled that achieved with far-field error microphones. Finally, the approach presents a significant alternative over other existing structural sensing techniques as it requires very little system modeling.Ph. D.
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Yousefi-Koma, Aghil. "Active vibration control of smart structures using piezoelements." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq26875.pdf.
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Bravo, Rafael. "Vibration control of flexible structures using smart materials." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape4/PQDD_0034/NQ66256.pdf.
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Gummadi, Lakshmana Nagesh Babu. "Active control of delaminations in smart composite structures." Diss., Georgia Institute of Technology, 1992. http://hdl.handle.net/1853/13022.
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Tridech, Charnwit. "Smart fibre coatings stiffness control in composite structures." Thesis, Imperial College London, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.529352.
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Miller, Scott E. (Scott Edward). "Distributed parameter active vibration control of smart structures." Thesis, Massachusetts Institute of Technology, 1988. http://hdl.handle.net/1721.1/33473.
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Ahrens, Christian P. "A real time embedded controller for smart structures." Thesis, Virginia Tech, 1989. http://hdl.handle.net/10919/44102.
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This thesis presents a simple Real Time Embedded Control System (RTECS) in an application of Intelligent Structure Monitoring. Research in smart structures, especially the area of vibration suppression, has warranted the investigation of advanced computing environments. Real time PC computing power has limited development of high order control algorithms. The system discussed allows for implementation of l/O intensive algorithms and provides capability for advanced system development.
In an application of Modal Domain Sensing for Vibration Control, RTECS is compared to a PC AT based system for overall functionality and speed. Using a model development procedure, the system is optimized for efficient operation and speed. This includes minimizing the computational overhead associated with I/O. A comparison shows an order of magnitude I increase in system speed with larger speed increases discussed. The results provide an avenue for high order control system design. This leads to more accurate device modeling and a higher level of system control.
RTECS employs a novel RISC microcontroller capable of 15 MIPs continuous performance and burst rates of 40 MIPs. Advanced CMOS circuits are integrated on a single printed circuit board measuring 100 mm by 160 mm and require only 1 Watt of power. An operating system written in Forth provides the flexibility for high speed operation in short development cycles.
Master of Science
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Yousefi-Koma, Aghil Carleton University Dissertation Engineering Mechanical and Aerospace. "Active vibration control of smart structures using piezoelements." Ottawa, 1997.
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Dennerlein, Jürgen. "Broadband vibration control of spatially distributed smart structures." Düsseldorf VDI-Verl, 2008. http://d-nb.info/993722431/04.
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Giammarruto, Alessio. "Smart structures: sperimentazione mediante attuatori e sensori innovativi." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2008. http://amslaurea.unibo.it/93/.
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L’idea di base della seguente tesi, finora mai applicata o descritta in letteratura scientifica in base alle ricerche effettuate, è stata quella di creare un sistema di monitoraggio strutturale intelligente (Structural Health Monitoring, SHM) mediante dei sensori di deformazione a reticolo di Bragg (Fiber Bragg Grating, FBG), incollati su fili a memoria di forma inseriti a loro volta, bloccati con opportuni ancoraggi esterni, in sei travi di betoncino cementizio armato.
L’obbiettivo della sperimentazione è stato quindi quello di creare delle travi intelligenti che, in condizioni di carico eccezionali e critiche (monitorate dal sensore a fibra ottica), sapessero “autoripararsi” mediante gli attuatori a memoria di forma con un processo di riscaldamento appositamente progettato.
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Moss, Scott. "Modelling and experimental validation of the acoustic electric feedthrough technique." Fishermans Bend, Victoria : Defence Science and Technology Organisation, 2008. http://hdl.handle.net/1947/9738.
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Singla, Geetika. "Activity recognition in complex smart environment settings." Pullman, Wash. : Washington State University, 2009. http://www.dissertations.wsu.edu/Thesis/Spring2009/g_singla_041409.pdf.
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Thesis (M.S. in computer science)--Washington State University, May 2009.Title from PDF title page (viewed on April 5, 2010). "Department of Electrical Engineering and Computer Science." Includes bibliographical references (p. 105-110).
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Lee, Seung Joon. "Nonlinear analysis of smart composite plate and shell structures." Diss., Texas A&M University, 2003. http://hdl.handle.net/1969.1/2218.
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Theoretical formulations, analytical solutions, and finite element solutions for laminated composite plate and shell structures with smart material laminae are presented in the study. A unified third-order shear deformation theory is formulated and used to study vibration/deflection suppression characteristics of plate and shell structures. The von K??rm??n type geometric nonlinearity is included in the formulation. Third-order shear deformation theory based on Donnell and Sanders nonlinear shell theories is chosen for the shell formulation. The smart material used in this study to achieve damping of transverse deflection is the Terfenol-D magnetostrictive material. A negative velocity feedback control is used to control the structural system with the constant control gain. The Navier solutions of laminated composite plates and shells of rectangular planeform are obtained for the simply supported boundary conditions using the linear theories. Displacement finite element models that account for the geometric nonlinearity and dynamic response are developed. The conforming element which has eight degrees of freedom per node is used to develop the finite element model. Newmark's time integration scheme is used to reduce the ordinary differential equations in time to algebraic equations. Newton-Raphson iteration scheme is used to solve the resulting nonlinear finite element equations. A number of parametric studies are carried out to understand the damping characteristics of laminated composites with embedded smart material layers.
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Wang, Qishan. "Active vibration and buckling control of piezoelectric smart structures." Thesis, McGill University, 2013. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=114328.
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The objective of this dissertation is the vibration and buckling control of piezo-laminated composite structures with surface bonded or embedded piezoelectric sensors and actuators by using the finite element analysis and LQR/LQG feedback control techniques. The focus is mainly on two aspects: the finite element part and the active control part. (1) The finite element part:Two finite element formulations for the piezo-laminated beams based on the classical Bernoulli-Euler and the Timoshenko beam theories are developed using the coupled linear piezoelectric constitutive equations, and the Hamilton variation principle. A C0 continuous, shear flexible, eight-node serendipity doubly curved shell element for the piezo-laminated composite plates and shells is also developed based on the layer-wise shear deformation theory, linear piezoelectric coupled constitutive relations, and Hamilton variation principle. The developed elements can handle the transverse shear strains, composite materials, and piezoelectric-mechanical coupling. Higher modes of vibration can then be predicted more precisely for thin to medium-thick multi-layered composite structures. They are evaluated both for the vibration and buckling of beam, plate, and shell structures. (2) The active control part: The suppression of vibration of a cantilever piezo-laminated beam and the control of the first two buckling modes of a simply supported piezo-laminated beam are studied first. Then, the vibration and buckling control of a cantileverpiezo-laminated composite plate are studied. Furthermore, the vibration control of a piezolaminated semicircular cylindrical shell is also studied. The results of the finite element analysis are used to design a linear quadratic regulator (LQR) controller and a linear quadratic Gaussian (LQG) compensator with a dynamic state observer to achieve all the controls. The control design begins with an approximate reduced modal model which can represent the system dynamics with the least system modes. A state space modal model of the smart structure which integrates the host structure with bonded piezoelectric sensors and actuators, is then used to design the control system. The designed LQR/LQG feedback controls are shown to be successful in suppressing the vibration and stabilizing the buckling modes of structures. Both the finite element analysis and the active control simulation results are consistent with the existing theoretical analysis results and the experimental data in the literature. Some important conclusions and interesting observations are obtained.L'objectif de cette thése est le contrôle de la vibration et de flambage à l'aide de l'analyse par éléments finis et LQR/LQG technologies de contrôle de rétroaction pour les structures composites stratifiées piézo-électriques qui sont liés ou incorporés de surface de capteurs et d'actionneurs piézoélectriques. Il ya principalement deux parties ciblées. La partie des éléments finis : Deux formulations éléments finis pour les poutres laminées piézo-basé sur le classique d'Euler-Bernoulli et la théorie des poutres de Timoshenko, respectivement, linéaires couplées piézoélectriques équations constitutives, et le principe de variation de Hamilton sont développés. Un C0 continue, cisaillement flexible, à huit nuds élément de coque à double courbure sérendipité pour les plaques piézocomposites stratifiés et de coquillages est également dérivée basée sur la théorie de la couche-sage déformation de cisaillement, linéaires piézo-électriques couplés relations constitutives mécaniques, et le principe de variation de Hamilton. Toute la poutre, plaque, et des éléments de coque développés ont considéré la rigidité, de masse et les effets de couplage électromécanique du capteur piézo-électrique et les couches de l'actionneur. Les éléments de structure développéssont capables de traiter les effets non linéaires de déformation en cisaillementtransversal et la non-linéarité des matériaux composites, piézoélectrique-mécanique d'accouplement, et peut prévoir plus précisément les modes supérieurs de vibration, et peut être appliquée à partir de minces d'épaisseur moyenne structures composites multicouches. Ils sont évalués à la fois les vibrations et analyse de flambage de la poutre, plaque, et structures en coque. La partie de commande actif : La vibration de supprimer d'un porte à faux piézo-collé poutre, les deux premiers modes de flambement contrôle d'un appui simple piézo-collé poutre, et la vibration et le flambage contrôle de la charge d'un cantilever piézoélectrique stratifié plaque composite sont étudiés. Les résultats de l'analyse par éléments finis sont utilisés pour concevoir un régulateur linéaire quadratique (LQR) contrôleur et un linéaire quadratique gaussienne (LQG) compensateur avec un observateur d'état dynamique pour atteindre toutes les commandes. Les conceptions de commandes commencent par une méthode modale modle pour déterminer un modle modal réduit approximative qui peut représenter la dynamique du systme avec les modes les moins systme inclus. Un modle modal espace d'état de la structure intelligente qui a intégré la structure d'accueil d'colléscapteurs et d'actionneurs piézoélectriques, est ensuite utilisé pour concevoir le systme de contrôle. Les contrôles visant commentaires LQR/LQG sont avérés succs dans la suppression de la vibration et de stabiliser les modes de flambement des structures. Tant l'analyse par éléments finis et les résultats de simulation de contrôle actives sont compatibles avec les résultats existants d'analyse théoriques et les données expérimentales de la littérature. Quelques conclusions importantes et des observations intéressantes sont obtenues.
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Apichayakul, Phisut. "Spatio-temporal State Space Model Estimation for Smart structures." Thesis, University of Sheffield, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.522539.
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Lee, Young-Sup. "Active control of smart structures using distributed piezoelectric transducers." Thesis, University of Southampton, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.324821.
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Sousa, Margarida Bucho Nunes de. "Smart macroporous structures for the purification of viral particles." Master's thesis, Faculdade de Ciências e Tecnologia, 2014. http://hdl.handle.net/10362/12179.
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Dissertação para obtenção do Grau de Mestre em
Engenharia Química e BioquímicaThe increasing application of viral particles in vaccination and gene-based therapies, has led to the development of alternative and improved purification processes. Traditional purification methods include chromatographic techniques, however the chromatographic matrices used present limitations specially when aimed at the purification of large molecules. This work presents the preparation of chitosan-based monoliths using clean processes and easy functionalization techniques intending to improve Adenovirus serotype 5 (Ad5) purification. Monoliths were prepared by blending chitosan (CHT) with glycidylmethacrylate (GMA) or poly(vinyl alcohol) (PVA), using two preparation techniques, freeze-drying and a scCO2 – assisted drying process, and were subsequently functionalized with Q ligands by three different methods. In addition, monoliths blended with magnetic nanoparticles were also prepared using the same strategies to confer them a controlled magnetic response. The monoliths produced were characterized in terms of ligand immobilization yield, and evaluated for Ad5 purification. Two types of monoliths showed potential: the CHT/PVA(50:50) prepared by freeze drying and functionalized by the alternative plasma technique (M2) and the CHT/PVA(50:50) 7% monolith prepared by scCO2 – assisted drying process and functionalized by the epoxyactivation technique (M1). The amount of ligand Q immobilized on the supports was monitored by titration assays, among which the CHT/PVA(50:50) 7% M2 prepared by scCO2 – assisted drying process exhibited the highest immobilization yield (91%). Among the results for Ad5 purification, the CHT/PVA(50:50)M2 and the CHT/PVA(50:50)7% M1 resulted in a 40% and 14% of the viral particles, respectively. Protein-binding assays were conducted using bovine serum albumin (BSA) and lysozyme, to evaluate the anionic-exchange capacity of the supports. The results make us believe in the potential of the produced monoliths to be applied in chromatographic techniques. However further improvements are necessary to enhance virus binding and recovery, to obtain an improved purification process.
project PTDC/EBB-BIO/118317/2010
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Hardy, Verity-Gay. "Design and construction of smart structures for technical textiles." Thesis, University of Leeds, 2008. http://etheses.whiterose.ac.uk/661/.
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The smart textiles sector is becoming increasingly significant within the technical textiles industry, contributing an increasing number of products and applications using a number of different technologies. This research is concerned primarily with electrically conductive smart textiles and, for the purposes of this project, smart structures are considered to be electrically conductive components which can be used in conjunction with technical textiles in order to enhance their performance and properties. The term `smart textiles' defines materials with advanced responsive properties enabling them to sense, actuate and/or control and the primary aim of this research was to characterise commercially available conductive yarns in terms of their structure, composition and physical behaviour in relation to their electrical behaviour. The secondary aim was to manufacture an electrically conductive textile material that could act as a strain sensor with the aim of integrating them into or onto existing technical textile fabrics. A range of static, dynamic and cyclic mechanical-electrical tests were carried out on a number of commercially available conductive yarns, work which informed the decision to base further experimental work on the integration of Carbon Black particles and Carbon Nanotubes into Nylon 6.10 and extrude a monofilament using a standard melt spinning technique. Although the resultant yarns manufactured did not display the properties required, analysis of the CB and CNT properties, the conductive particle dispersion within the polymer matrix, the yarn structure and the manufacturing method all informed the development of the design paradigm. The resultant design paradigm developed highlights the most significant variables and parameters to take into consideration when designing a textile sensor, and suggests solutions that would result in successful sample production. The paradigm covers design solutions for the conductive particles, the polymer, the compounding method, yarn manufacturing parameters and the resultant yarn structure. Whilst the information contained therein is not exhaustive, this being due to the inherent multilevel complexity of designing a textile system, it acts as a guide for sensor development and may help circumvent costly and timely sample manufacturing errors.
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Matsouka, Dimitroula. "Efficiency and durability of wearable smart materials and structures." Thesis, University of Bolton, 2018. http://ubir.bolton.ac.uk/1767/.
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Piezoelectric polymer materials have been under investigation since the 1970’s starting with the discovery of the piezoelectric effect in PVDF films by Kawai. Since then the piezoelectric effect has been detected among other polymers in polyureas, polyamides, and polypropylene and their copolymers. While the investigation of the piezoelectric effect was largely carried out on the film form of the polymers since 2010 interest has developed into the production methods, properties and applicability of melt spun piezoelectric textile fibres made of these polymers. The application of piezoelectric fibres could have a significant impact in wearable textiles as sensors, actuators, or energy harvesting modules. Current research is mostly centred onto production methods and fibre crystallinity characterization. The research carried out in this PhD by publication project is concerned with piezoelectric textile fibres as electrically active elements. As such the research focused on the electrical behaviour of the fibres. The work carried out was threefold. Specifically, wearable textile materials undergo cleaning/ care treatments that are intrinsic to their function as wearables. These treatments may include washing, dry cleaning or sponging. Washing (cleaning treatment in a solution mainly containing water and an appropriate detergent at an elevated temperature or room temperature) is a common cleaning method. The effects of washing cycles on melt spun piezoelectric fibres remain under-investigated. For the first part of the research, piezoelectric melt spun fibres (PVDF, PP and PA-11) with two different cross sections (circular and rectangular), were mechanically stimulated by a rotating fin that impacted the fibres periodically. The resulting Vp-p (peek to peek voltage), was measured on the original fibres and on the fibres following one wash cycle (adapted BS EN ISO 105-C06), using an oscilloscope. Based on the results of this part of the research it was shown that the washing cycle effected the voltage response of the fibres depending on the fibre cross section and the fibre composition. The results of the research were presented in a paper titled “Investigation of the durability and stability of piezoelectric textile fibres” published in the Journal of Intelligent Materials Systems and Structures. For the second part of the research, it was noted that according to the existing literature the research approach for the determination of the electrical response of the fibres utilized exclusively the measurement of the voltage produced by mechanical excitation of the fibres, in open circuit conditions. This approach is not sufficient to satisfactorily characterise the electrical behaviour of the fibres as power generating elements. By contrast, a sufficient measurement is the power production of the fibres as this also includes a measurement of the current produced. In order to supply these measurements a testing apparatus/ methodology was developed. The apparatus consists of a measuring station where the voltage and current produced are measured, and a means for periodic mechanical stimulation of the specimens. The equipment was used to determine the power generated by piezoelectric melt spun fibres (PVDF, PP and PA-11) with two different cross sections (circular and rectangular). The results of the research were presented in a paper titled “On the Measurement of the Electrical Power Produced by Melt Spun Piezoelectric Textile Fibres” published in the Journal of Electronic Materials. Finally, considering the underlying premise of integration of fully textile based electronic components into textile substrates (e.g. wearable applications), 3D knitted fabrics that incorporated piezoelectric melt spun fibres were investigated with regards to their capacitive behaviour. Four different fabric structures were examined (different composition of the outside layers and different thickness). The capacitive behaviour of the samples was modelled based on the specific structural characteristics of the fabrics and the actual properties were determined using an Impedance Analyzer. Based on the results it was found that the theoretical model for the calculation of the capacitance of the samples appeared to be an acceptable approximation for the behaviour of the fabrics. Also, the ability to customise the required capacitance to suit the applications by specifying the dimensions of the 3D fabric and/or the density, the thickness or even the material of the interlaced fibres has also been shown to be possible. Moreover, reviewing the results of a resonance test for a purely textile based parallel LC circuit, it was shown that it is possible to implement resonant circuits that are convenient for basic electronic applications (i.e. oscillators, filters, etc.). The results of the research were presented in a paper titled “Three-dimensional weft-knitted textile fabrics-based capacitors” published in the Journal of the Textile Institute. This research project touched on some of the less thoroughly investigated research areas connected to the efficiency and durability of piezoelectric melt spun fibres and structures, with innovative results such as the development/ construction of the equipment that can be used for the measurement of the power produced by piezoelectric textile fibres as well as the investigation of the capacitive behaviour of the 3D knitted fabrics incorporating piezoelectric textile fibres and the conclusion that resonance is possible to achieve in a purely textile LC parallel circuit.
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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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Ruggiero, Eric John. "Active Dynamic Analysis and Vibration Control of Gossamer Structures Using Smart Materials." Thesis, Virginia Tech, 2002. http://hdl.handle.net/10919/32299.
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Increasing costs for space shuttle missions translate to smaller, lighter, and more flexible satellites that maintain or improve current dynamic requirements. This is especially true for optical systems and surfaces. Lightweight, inflatable structures, otherwise known as gossamer structures, are smaller, lighter, and more flexible than current satellite technology. Unfortunately, little research has been performed investigating cost effective and feasible methods of dynamic analysis and control of these structures due to their inherent, non-linear dynamic properties. Gossamer spacecraft have the potential of introducing lenses and membrane arrays in orbit on the order of 25 m in diameter. With such huge structures in space, imaging resolution and communication transmissibility will correspondingly increase in orders of magnitude.
A daunting problem facing gossamer spacecraft is their highly flexible nature. Previous attempts at ground testing have produced only localized deformation of the structureâ s skin rather than excitation of the global (entire structureâ s) modes. Unfortunately, the global modes are necessary for model parameter verification. The motivation of this research is to find an effective and repeatable methodology for obtaining the dynamic response characteristics of a flexible, inflatable structure. By obtaining the dynamic response characteristics, a suitable control technique may be developed to effectively control the structureâ s vibration. Smart materials can be used for both active dynamic analysis as well as active control. In particular, piezoelectric materials, which demonstrate electro-mechanical coupling, are able to sense vibration and consequently can be integrated into a control scheme to reduce such vibration. Using smart materials to develop a vibration analysis and control algorithm for a gossamer space structure will fulfill the current requirements of space satellite systems. Smart materials will help spawn the next generation of space satellite technology.Master of Science
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Wang, Xiaodong. "The dynamic behaviour of interacting piezoelectric actuators in smart structures." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp02/NQ35363.pdf.
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Baillargeon, Brian P. "Active Vibration Suppression of Smart Structures Using Piezoelectric Shear Actuators." Fogler Library, University of Maine, 2003. http://www.library.umaine.edu/theses/pdf/BailargeonBP2003.pdf.
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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."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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Kim, JungMi. "System Identification of Smart Structures Using a Nonlinear WARMA Model." Digital WPI, 2013. https://digitalcommons.wpi.edu/etd-theses/7.
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System identification (SI) for constructed structural systems has received a lot of attention with the continuous development of modern technologies. This thesis proposes a new nonlinear time series model for use in system identification (SI) of smart structures. The proposed model is implemented by the integration of a wavelet transform (WT) and nonlinear autoregressive moving average (NARMA) time series model. The approach demonstrates the efficient and accurate nonlinear SI of smart structures subjected to both ambient excitation and high impact load. To demonstrate the effectiveness of the wavelet-based NARMA modeling (WNARMA), smart structures equipped with magnetorheological (MR) dampers are investigated. The simulation results show that the computation of the WNARMA model is faster than that of the NARMA model without sacrificing the modeling accuracy. In addition, the WNARMA model is robust against noise in the data since it inherently has a denoising capacity.
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Berglin, Lena. "Interactive Textile Structures : Creating Multifunctional Textiles based on Smart Materials." Doctoral thesis, Högskolan i Borås, Institutionen Textilhögskolan, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:hb:diva-3490.
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Textiles of today are materials with applications in almost all our activities. We wear clothes all the time and we are surrounded with textiles in almost all our environments. The integration of multifunctional values in such a common material has become a special area of interest in recent years. Smart Textile represents the next generation of textiles anticipated for use in several fashion, furnishing and technical textile applications. The term smart is used to refer to materials that sense and respond in a pre-defined manner to environmental stimuli. The degree of smartness varies and it is possible to enhance the intelligence further by combining these materials with a controlling unit, for example a microprocessor. As an interdisciplinary area Smart Textile includes design spaces from several areas; the textile design space, the information technology design space and the design space of material science. This thesis addresses how Smart Textiles affect the textile design space; how the introduction of smart materials and information technology affects the creation of future textile products. The aim is to explore the convergence between textiles, smart materials and information technology and to contribute to providing a basis for future research in this area. The research method is based on a series of interlinked experiments designed through the research questions and the research objects. The experiments are separated into two different sections: interactive textile structures and health monitoring. The result is a series of basic methods for how interactive textile structures are created and a general system for health monitoring. Furthermore the result consists of a new design space, advanced textile design. In advanced textile design the focus is set on the relation between the different natures of a textile object: its physical structure and its structure in the context of design and use.
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Janda, Oliver. "Modeling and Control of Sound and Vibration for Smart Structures." Phd thesis, Sierke-Verlag, 2014. https://tuprints.ulb.tu-darmstadt.de/4154/1/Diss_Janda_Final.pdf.
Full textAbstract:
This thesis presents a contribution to the improvement of modeling and control methodologies for smart structures. It is focused on comfort-compromising, sound- and vibration-related problems, which can be successfully handled by the concepts developed within the interdisciplinary field of adaptronics. As far as modeling of smart structures is concerned, it is advocated in this thesis to employ theoretical modeling to gather an understanding of the fundamental system properties and of the characteristics that are relevant for control design. Theoretical modeling of a generic smart structure with electromechanical as well as mechanical-acoustical coupling is illustrated at the beginning of this thesis. However, pure theoretical modeling of complex systems generally lacks sufficient accuracy for subsequent control design. For that reason, data-driven modeling is one of the key aspects of this work. A modeling procedure is developed that is capable of identifying models for linear time-invariant systems with many resonances from measurement data along with their associated model uncertainty. A minimum of prior assumptions is needed. Based on these models and their uncertainty descriptions, a straightforward yet powerful design methodology for multi-input multi-output active vibration control is presented. The resulting control design employs the well-developed machinery of H2 optimal control, and the resulting control loops are robustly stable with respect to the a-priori identified model uncertainty. This robust optimal design methodology for multi-input multi-output controllers offers both better performance and more degrees of freedom compared to the dominating design of single-input single-output controllers for active vibration control. These additional degrees of freedom especially pay off when not only vibration amplitudes but also vibration mode shapes in closed-loop are relevant. This is for example the case when acoustic radiation shall be controlled. Active acoustic control with structural measurements and control inputs is known as active structural acoustic control, which is the second key aspect of this work. A powerful tool for describing structure-borne sound radiation is the so-called power transfer matrix. This frequency-dependent matrix allows for the computation of structure-borne sound power from knowledge of structural motion. Here, a novel experimental modeling procedure for power transfer matrices is introduced which does not impose any restrictions on the geometry of the radiating structure or the acoustic environment whatsoever. With the help of this matrix, the robust optimal control design scheme for active vibration control can be extended to the control of structure-borne sound power in a straightforward manner. It is also shown that sound radiation into enclosed spaces can be handled with minor modifications of the control scheme for free-field radiation. All modeling and control design methods presented in this thesis are validated by simulation as well as experimental results.
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Lentzen, Sven. "Nonlinearly coupled thermopiezoelectric modelling and FE simulation of smart structures." Düsseldorf VDI-Verl, 2009. http://d-nb.info/993098843/04.
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Zanotti, Nicola. "Strutture intelligenti (Smart Structures): sensori, attuatori e materiali self-healing." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2012. http://amslaurea.unibo.it/4193/.
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Wang, Peng. "Active vibration control in a specific zone of smart structures." Thesis, Lyon, 2019. http://www.theses.fr/2019LYSEC007/document.
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Cette recherche vise à résoudre un problème particulier du contrôle de vibration des structures intelligentes. Notre objectif est de réduire les vibrations dans une zone spécifique de la structure intelligente avec une perturbation qui couvre une large gamme de fréquences. De plus, dans cette zone spécifique, ni l'actionnement ni la détection ne sont possibles.Ici, nous faisons face à plusieurs défis principaux. Premièrement, nous devons contrôler les vibrations d’une zone spécifique de la structure, alors que nous n’avons accès aux mesures que dans d’autres zones. Deuxièmement, la large bande passante de la perturbation implique que nombreux modes doivent être contrôlés au même temps, ce qui nécessite l'utilisation de plusieurs actionneurs et capteurs. Cela conduit à un contrôleur MIMO difficile à obtenir avec les méthodes classiques de conception de contrôleur. Troisièmement, il faut éviter le problème de propagation, qui consiste à garantir la stabilité en boucle fermée lorsque le contrôleur basé sur un modèle est appliqué à la configuration réelle. Pour relever ces défis, nous étudions deux stratégies de contrôle: le contrôle centralisé et le contrôle distribué.Pour le contrôle centralisé, nous proposons une méthodologie qui nous permet d’obtenir un contrôleur MIMO simple permettant de relever ces défis. Tout d'abord, plusieurs techniques de modélisation et d’identification sont appliquées pour obtenir un modèle précis d'ordre faible de la structure intelligente. Ensuite, une méthode de synthèse basée sur le contrôle H_∞ avec un critère H_∞ particulièrement proposé est appliquée. Ce critère H_∞ intègre plusieurs objectifs de contrôle, y compris les défis principaux. En particulier, le problème de débordement se transforme en un problème de stabilité robuste et sera garanti en utilisant ce critère. Le contrôleur H_∞ obtenu est une solution standard du problème H_∞. Le contrôleur final est obtenu en simplifiant ce contrôleur H_∞ sans perdre la stabilité en boucle fermée ni dégrader les performances. Cette méthodologie est validée sur une structure de poutre avec des transducteurs piézoélectriques et la zone centrale est celle où les vibrations devraient être réduites. L'efficacité du contrôleur obtenu est validée par des simulations et des expériences.Pour le contrôle distribué, on considère la même structure de poutre et les mêmes objectifs de contrôle. Il existe des méthodes visant à concevoir des contrôleurs distribués pour les systèmes spatialement interconnectés. Cette recherche propose une méthode basée sur la FEM, associée à plusieurs techniques de réduction de modèle, permettant de discrétiser spatialement la structure de poutre et d'en déduire les modèles d’espace d'état des sous-systèmes interconnectés. La conception des contrôleurs distribués ne sera pas abordée dans cette rechercheThis research aims at solving a particular vibration control problem of smart structures. We aim at reducing the vibration in a specific zone of the smart structure under the disturbance that covers a wide frequency band. Moreover, at this specific zone, neither actuation nor sensing is possible.Here we face several main challenges. First, we need to control the vibration of a specific zone of the structure while we only have access to measurements at other zones. Second, the wide bandwidth of the disturbance implies that numerous modes should be controlled at the same time which requires the use of multiple actuators and sensors. This leads to a MIMO controller which is difficult to obtain using classical controller design methods. Third, the so-called spillover problem must be avoided which is to guarantee the closed-loop stability when the model-based controller is applied on the actual setup. To tackle these challenges, we investigate two control strategies: the centralized control and the distributed control.For centralized control, we propose a methodology that allows us to obtain a simple MIMO controller that accomplishes these challenges. First, several modeling and identification techniques are applied to obtain an accurate low-order model of the smart structure. Then, an H_∞ control based synthesis method with a particularly proposed H_∞ criterion is applied. This H_∞ criterion integrates multiple control objectives, including the main challenges. In particular, the spillover problem is transformed into a robust stability problem and will be guaranteed using this criterion. The obtained H_∞ controller is a standard solution of the H_∞ problem. The final controller is obtained by further simplifying this H_∞ controller without losing the closed-loop stability and degrading the performance. This methodology is validated on a beam structure with piezoelectric transducers and the central zone is where the vibration should be reduced. The effectiveness of the obtained controller is validated by simulations and experiments.For distributed control, we consider the same beam structure and the same control objectives. There exist methods aiming at designing distributed controllers of spatially interconnected system. This research proposes a FEM based method, combined with several model reduction techniques, that allows to spatially discretize the beam structure and deduce the state-space models of interconnected subsystems. The design of distributed controllers will not be tackled in this research
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Kakani, Naveen Kumar. "Algorithms for Efficient Utilization of Wireless Bandwidth and to Provide Quality-of-Service in Wireless Networks." Thesis, University of North Texas, 2000. https://digital.library.unt.edu/ark:/67531/metadc2635/.
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This thesis presents algorithms to utilize the wireless bandwidth efficiently and at the same time meet the quality of service (QoS) requirements of the users. In the proposed algorithms we present an adaptive frame structure based upon the airlink frame loss probability and control the admission of call requests into the system based upon the load on the system and the QoS requirements of the incoming call requests. The performance of the proposed algorithms is studied by developing analytical formulations and simulation experiments. Finally we present an admission control algorithm which uses an adaptive delay computation algorithm to compute the queuing delay for each class of traffic and adapts the service rate and the reliability in the estimates based upon the deviation in the expected and obtained performance. We study the performance of the call admission control algorithm by simulation experiments. Simulation results for the adaptive frame structure algorithm show an improvement in the number of users in the system but there is a drop in the system throughput. In spite of the lower throughput the adaptive frame structure algorithm has fewer QoS delay violations. The adaptive call admission control algorithm adapts the call dropping probability of different classes of traffic and optimizes the system performance w.r.t the number of calls dropped and the reliability in meeting the QoS promised when the call is admitted into the system.
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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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Nwankwo, Cosmas Chidozie. "Smart offshore structure for reliability prediction process." Thesis, Cranfield University, 2013. http://dspace.lib.cranfield.ac.uk/handle/1826/9335.
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A review of the developments within the field of structural reliability theory shows that
some gaps still exist in the reliability prediction process and hence there is an urgent
desire for improvements such that the estimated structural reliability will be capable of
expressing a physical property of the given structure. The current reliability prediction
process involves the continuous estimation and use of reliability index as a way of
estimating the safety of any given structure. The reliability index β depends on the
Probability Density Function (PDF) distribution for the wave force and the corresponding
PDF of resistance from respective structural members of the given structure. The PDF
for the applied wave force will depend on the PDF of water depth, wave angular velocity
and wave direction hence the reliability index as currently practiced is a statistical way
of managing uncertainties based on a general probabilistic model.
This research on Smart Offshore Structure for Reliability Prediction has proposed the
design of a measurement based reliability prediction process as a way of closing the
gap on structural reliability prediction process. Structural deflection and damping are
some of the measurable properties of an offshore structure and this study aims at
suggesting the use of these measurable properties for improvements in structural
reliability prediction process. A design case study has shown that a typical offshore
structure can deflect to a range of only a few fractions of a millimetre. This implies that if
we have a way of monitoring this level of deflection, we could use the results from such
measurement for the detection of a structural member failure. This advocated concept is
based on the hypothesis that if the original dynamic characteristics of a structure is
known, that measurement based modified dynamic properties can be used to determine
the onset of failure or failure propagation of the given structure.
This technology could reveal the location and magnitude of internal cracks or corrosion
effects on any given structure which currently is outside the current probability based
approach. A simple economic analysis shows that the recommended process shows a
positive net present value and that some $74mln is the Value of Information for any life
extension technology that could reveal the possibility of extending the life of a given
10,000bopd production platform from 2025 to 2028.
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Blockey, James Craig. "Feasibility in developing smart structures for use in wind turbine blades." Thesis, Montana State University, 2008. http://etd.lib.montana.edu/etd/2008/blockey/BlockeyJ0808.pdf.
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Recently the use of wind as an alternative energy source has developed quickly. The length of the blades is a leading factor in the power output of a wind turbine and as a result, blade length has grown at a similar pace to the growth of the industry. The rapid expansion in use and size of wind turbines is not without its problems, though. As the industry has changed and grown, the overall design of the blades has remained relatively stagnant. This is evident in two primary areas, power control and health monitoring. Power control mechanisms are generally unchanged, utilizing either pitch control or active stall designs. While effective, these systems are neither efficient nor fast acting and can contribute to higher maintenance requirements. Current wind turbine blades also have no sensors built into them. The nacelle and tower utilize many sensors, but the blades themselves have none, leading to blades which are incapable of any real time health monitoring. The application of smart structures will enable the in situ monitoring of the blade and allow the blade to adapt to changing wind loadings Smart structures are those which apply an array of sensors to continuously monitor the state of the structure and are capable of using those sensors to appropriately react to achieve a desired state. This paper will examine the application of smart structures to the wind energy industry. It will be shown that a fiber optic, Fiber Bragg Grating sensor is the best type of sensor for wind energy. One of the main contributing factors is the capability of the sensors to multiplex, which means many sensors can be located along a single optical fiber and different types of sensors can be run on the same optical fiber. The blades will \'react\' to changing conditions through the use of an actuated Gurney style flap. The flap will be used to shed the wind loads from the blade in high wind scenarios. These systems working together will provide an effective and efficient method of advancing the design of the wind turbine blade to a level appropriate for the systems expected today and in the future.
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Zheng, Xiang. "Active vibration control of flexible bodied railway vehicles via smart structures." Thesis, Loughborough University, 2011. https://dspace.lboro.ac.uk/2134/9110.
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Future railway vehicles are going to be designed lighter in order to achieve higher speed. Suppressing the flexible modes becomes a crucial issue for improving the ride quality of the light-weight high speed railway vehicles. The concept of smart structure brings structural damping to flexible structures by integrating smart actuators and sensors onto the structure. Smart structure eliminates the need for extensive heavy mechanical actuation systems and achieves higher performance levels through their functionality for suppressing the flexible modes. Active secondary suspension is the effective conventional approach for vibration control of the railway vehicle to improve the ride quality. But its ability in suppressing the flexible modes is limited. So it is motivated to combine active structural damping for suppressing the flexible modes and the vibration control through active secondary suspension which has an effect on both rigid and flexible modes. The side-view model of the flexible-bodied railway vehicle integrated with piezoelectric actuators and sensors is derived. The procedure for selection of placement configurations of the piezoelectric actuators and sensors using structural norms is presented. Initial control studies show that the flexibility of the vehicle body will cause a considerable degradation in ride quality if it is neglected in the design model. Centralized and decentralized control strategies with various control approaches (e.g. modal control with skyhook damping, LQG/H2 control, H_infinity control and model predictive control (MPC))are applied for the combined control of active structural damping and active suspension control. The active structural damping effectively suppresses the flexible modes as a complement to the work of the active suspension control.
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Hassan, Mohd Roshdi. "Design, manufacturing and testing of SMA-based smart and cellular structures." Thesis, University of Sheffield, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.434620.
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Arsava, Kemal Sarp. "Modeling, Control and Monitoring of Smart Structures under High Impact Loads." Digital WPI, 2014. https://digitalcommons.wpi.edu/etd-dissertations/105.
Full textAbstract:
In recent years, response analysis of complex structures under impact loads has attracted a great deal of attention. For example, a collision or an accident that produces impact loads that exceed the design load can cause severe damage on the structural components. Although the AASHTO specification is used for impact-resistant bridge design, it has many limitations. The AASHTO specification does not incorporate complex and uncertain factors. Thus, a well-designed structure that can survive a collision under specific conditions in one region may be severely damaged if it were impacted by a different vessel, or if it were located elsewhere with different in-situ conditions. With these limitations in mind, we propose different solutions that use smart control technology to mitigate impact hazard on structures. However, it is challenging to develop an accurate mathematical model of the integrated structure-smart control systems. The reason is due to the complicated nonlinear behavior of the integrated nonlinear systems and uncertainties of high impact forces. In this context, novel algorithms are developed for identification, control and monitoring of nonlinear responses of smart structures under high impact forces. To evaluate the proposed approaches, a smart aluminum and two smart reinforced concrete beam structures were designed, manufactured, and tested in the High Impact Engineering Laboratory of Civil and Environmental Engineering at WPI. High-speed impact force and structural responses such as strain, deflection and acceleration were measured in the experimental tests. It has been demonstrated from the analytical and experimental study that: 1) the proposed system identification model predicts nonlinear behavior of smart structures under a variety of high impact forces, 2) the developed structural health monitoring algorithm is effective in identifying damage in time-varying nonlinear dynamic systems under ambient excitations, and 3) the proposed controller is effective in mitigating high impact responses of the smart structures.
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Temtem, Márcio Milton Nunes. "Development of biocompatible and “smart” porous structures using CO2-assisted processes." Doctoral thesis, FCT - UNL, 2009. http://hdl.handle.net/10362/1978.
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Dissertação apresentada para a obtenção do grau de Doutor em Engenharia Química,
especialidade Engenharia da Reacção Química, pela Universidade Nova de Lisboa, Faculdade
de Ciências e TecnologiaOver the past three decades the use of supercritical carbon dioxide (scCO2) has received much attention as a green alternative in the synthesis and processing of polymers. The scope of this thesis is the development of biocompatible and “smart” porous structures using CO2-assisted processes. This thesis is organized in four main chapters. The first one reviews and highlights some potentialities of supercritical fluid technology and the following ones compile the experimental work developed. The work is divided in three main parts: in the first part (2nd chapter) a CO2-assisted phase inversion method was developed in order to prepare porous structures, namely membranes. In the second part (3rd chapter) the focus was the synthesis of “smart” polymers,especially thermo and pH sensitive polymers. Finally, these two areas were combined (4th chapter) for the preparation of “smart” porous structures. The common guide line was the preparation or processing of biodegradable and/or biocompatible materials with special emphasis on the preparation of porous matrices, namely membranes and scaffolds, with controlled morphology. For membrane preparation a new high pressure apparatus and a new high pressure cell were developed. Polysulfone membranes (a biocompatible polymer with numerous applications in the medical field) were prepared and the effect of the solvent affinity and depressurization rate in the morphology and in the performance in terms of pure water flux of the membranes was investigated. The incorporation of a foaming agent was also analyzed and the high pressure CO2 capability to swell and melt polycaprolactone (PCL) was used to produce and control the porosity and the properties of the membranes. Finally, a natural and water soluble polymer (chitosan) was processed. The presence of water in the casting solution introduced extraordinary difficulties due to the low affinity between water and CO2. To induce the phase inversion a co-solvent (ethanol)was introduced in the CO2 stream. The obtained devices (membranes and beads) were fabricated using moderate temperatures and “green” solvents (ethanol, water and CO2). The morphology and the three dimensional (3D) structures were controlled by altering the co-solvent (ethanol) composition in the CO2 non-solvent stream during the demixing induced process. Microarchitectural analysis by scanning electron microscopy identified the formation of particulate agglomerates when 10% of ethanol in the scCO2 stream was used and detected the development of porous membranes with different morphologies and mechanical properties depending on the programmed gradient mode and the entrainer percentage (2.5-5%) added to the scCO2 stream. These chitosan matrices exhibited low solubility at neutral pH conditions, with no further modifications, demonstrating their applicability in bioreactors as static (membranes) or stirred (beads) culture devices. It was also demonstrated that the current method is able to prepare, in a single-step, an implantable antibiotic release system by co-dissolving gentamicin with chitosan and the solvent. In addition, the cytotoxicity as well as the ability of these structures to support the adhesion and proliferation of human mesenchymal stem cells (hMSC) in vitro were also addressed. After 2 weeks in culture, a 9-fold increase was obtained (versus 6 of the control). More importantly, cells maintained their clonogenic potential and immunophenotype (>95% CD 105+ Cells after 7 days of culture). In this chapter, a hypothetical schematic ternary diagram for the systems polymer–solvent–CO2 is used to discuss and explain the results. Another goal of this thesis was the synthesis of “smart” polymers. Chapter 3, addresses the precipitation polymerization of a thermoresponsive hydrogel, poly(N-isopropylacrylamide)(PNIPAAm), in scCO2. This hydrogel has a transition temperature, hereinafter called low critical solution temperature (LCST), around 32 ºC in an aqueous solution, close to body temperature. A strategy of solvent-free impregnation/coating of polymeric surfaces with PNIPAAm was suggested, in order to further extend the applications of membranes or porous bulky systems. The in situ synthesis of PNIPAAm within a chitosan scaffold was tested as a proof of concept, in order to produce smart partially-biodegradable scaffolds for tissue engineering applications. The LCST was tuned by copolymerization or graft polymerization of NIPAAm with other monomers. Copolymerization with hydroxyethyl methacrylate (HEMA) was used to decrease the LCST temperature from 32.2 ºC to approximately 27.7 ºC. Cloud point measurements of CO2 + HEMA system were used to optimize the polymerization temperature. Experimental data were obtained at 40 ºC, 50 ºC and 65 ºC and pressures up to 21.1 MPa. Soave-Redlich-Kwong equation of state with Mathias-Klotz-Prausnitz mixing rule was used to model experimental results and a good correlation was achieved. To increase the LCST, polyethylene oxide (an hydrophilic polymer) was grafted to PNIPPAAm. Dual stimulus (thermo and pH responsive) hydrogels were also prepared by copolymerizing methacrylic acid with PNIPAAm. As a proof of concept fluorouracil was incorporated in the hydrogels network and their release was controlled by temperature and pH stimulus. In chapter 4 the concepts of the previous chapters were put together envisaging the preparation of“smart” functional polymeric devices with targeted physical and chemical properties namely: (i) chitosan-based dual stimulus scaffolds (temperature and pH responsive); (ii) polysulfone-based thermoresponsive membranes and (iii) polymethylmethacrylate-based membranes. The chitosan scaffolds (pH sensitive) were coated/impregnated with a thermoresponsive polymer,poly(N-isopropylacrylamide) (PNIPAAm), using scCO2 as a carrier to homogeneously distribute the hydrogels monomer within the chitosan scaffolds and as a solvent to perform the polymerization reaction.
Fundação para a Ciência e Tecnologia através da bolsa de Doutoramento (SFRH/BD/16908/2004) e do projecto PTDC/CTM/70513/2006
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Lara, Prieto Vianney. "Smart structures : a study of an MR fluid-based machine element." Thesis, Loughborough University, 2009. https://dspace.lboro.ac.uk/2134/34455.
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With increasing market demands and new technology advances, manufacturing is aspiring to achieve automation with high productivity and improved precision and control. As a result, extensive research aiming to improve the performance of machining processes can be found. Undesired vibration within precision manufacturing processes is a major source of poor surface finish, increased tool wear, and poor dimensional accuracy. Chatter, i.e. self-excited vibration, is considered one of the critical sources of vibration that unfavourably affects the quality and productivity of high-speed manufacturing processes. This research investigates the controllability of the vibration characteristics of magnetorheological (MR) structures as a precursor to a future vibration control system.
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Ramadan, Mohamed Refat Mostafa <1991>. "Numerical and experimental analysis of 3D printed smart structures and systems." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2022. http://amsdottorato.unibo.it/10425/1/MRefat_Ramadan_main.pdf.
Full textAbstract:
Three dimensional (3D) printers of continuous fiber reinforced composites, such as MarkTwo (MT) by Markforged, can be used to manufacture such structures. To date, research works devoted to the study and application of flexible elements and CMs realized with MT printer are only a few and very recent. A good numerical and/or analytical tool for the mechanical behavior analysis of the new composites is still missing. In addition, there is still a gap in obtaining the material properties used (e.g. elastic modulus) as it is usually unknown and sensitive to printing parameters used (e.g. infill density), making the numerical simulation inaccurate.
Consequently, the aim of this thesis is to present several work developed. The first is a preliminary investigation on the tensile and flexural response of Straight Beam Flexures (SBF) realized with MT printer and featuring different interlayer fiber volume-fraction and orientation, as well as different laminate position within the sample. The second is to develop a numerical analysis within the Carrera' s Unified Formulation (CUF) framework, based on component-wise (CW) approach, including a novel preprocessing tool that has been developed to account all regions printed in an easy and time efficient way. Among its benefits, the CUF-CW approach enables building an accurate database for collecting first natural frequencies modes results, then predicting Young' s modulus based on an inverse problem formulation. To validate the tool, the numerical results are compared to the experimental natural frequencies evaluated using a digital image correlation method. Further, we take the CUF-CW model and use static condensation to analyze smart structures which can be decomposed into a large number of similar components. Third, the potentiality of MT in combination with topology optimization and compliant joints design (CJD) is investigated for the realization of automated machinery mechanisms subjected to inertial loads.I meccanismi con elementi flessibili, noti col termine inglese “Compliant Mechanisms” (CM), consentono la realizzazione di strutture intelligenti ad alte prestazioni. Tuttavia, produrre tali strutture con i materiali e le tecniche di lavorazione tradizionali è molto difficile. Grazie al recente sviluppo delle tecniche di produzione additiva, una possibilità per la realizzazione di queste strutture è la stampa tridimensionale (3D) di compositi a matrice polimerica rinforzati con fibre continue, ad esempio mediante la stampante MarkTwo (MT) di Markforged. In questo contesto, lo scopo di questa tesi è di gettare le basi per la risoluzione di questi problemi. Una prima attività svolta riguarda lo studio sperimentale del comportamento a trazione e a flessione di lamine rettilinee flessibili (Straight Beam Flexures, SBF) realizzate mediante 3D-MT e caratterizzate da diverse frazioni volumetriche e disposizioni delle fibre all’interno del medesimo strato e in strati differenti. La seconda attività riguarda lo sviluppo di uno strumento per l’analisi numerica di queste SBF, basato sulla formulazione unificata di Carrera (Carrera Unified Formulation, CUF) utilizzando l'approccio “component-wise” (CW), che include un nuovo elemento di pre-elaborazione che consente di considerare tutte le regioni stampate in modo semplice e con un ridotto tempo computazionale. Tra i suoi vantaggi, l'approccio CUF-CW consente di raccogliere le frequenze naturali dei primi modi di vibrare e di prevedere il modulo di Young del composito sulla base di una formulazione del problema inverso. Per convalidare lo strumento, i risultati numerici sono confrontati con le frequenze naturali valutate sperimentalmente mediante un approccio basato sulla correlazione di immagini digitali. Come terza ed ultima attività, le potenzialità della stampa mediante MT, in associazione con l’ottimizzazione topologica e la progettazione di meccanismi con membri/giunti flessibili (Compliant Joint Design, CJD), sono state investigate nel contesto della realizzazione di meccanismi per macchine automatiche soggetti a carichi inerziali.