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Sibai, Munira. "Optimization of an Unfurlable Space Structure." Thesis, Virginia Tech, 2020. http://hdl.handle.net/10919/99908.
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Deployable structures serve a large number of space missions. They are vital since spacecraft are launched by placing them inside launch vehicle payload fairings of limited volume. Traditional spacecraft design often involves large components. These components could have power, communication, or optics applications and include booms, masts, antennas, and solar arrays. Different stowing methods are used in order to reduce the overall size of a spacecraft. Some examples of stowing methods include simple articulating, more complex origami inspired folding, telescoping, and rolling or wrapping. Wrapping of a flexible component could reduce the weight by eliminating joints and other components needed to enable some of the other mechanisms. It also is one of the most effective methods at reducing the compaction volume of the stowed deployable. In this study, a generic unfurlable structure is optimized for maximum natural frequency at its fully deployed configuration and minimal strain energy in its stowed configuration. The optimized stowed structure is then deployed in simulation. The structure consists of a rectangular panel that tightly wraps around a central cylindrical hub for release in space. It is desired to minimize elastic energy in the fully wrapped panel and hinge to ensure minimum reaction load into the spacecraft as it deploys in space, since that elastic energy stored at the stowed position transforms into kinetic energy when the panel is released and induces a moment in the connected spacecraft. It is also desired to maximize the fundamental frequency of the released panel as a surrogate for the panel having sufficient stiffness. Deployment dynamic analysis of the finite element model was run to ensure satisfactory optimization formulation and results.Master of Science
Spacecraft, or artificial satellites, do not fly from earth to space on their own. They are launched into their orbits by placing them inside launch vehicles, also known as carrier rockets. Some parts or components of spacecraft are large and cannot fit in their designated space inside launch vehicles without being stowed into smaller volumes first. Examples of large components on spacecraft include solar arrays, which provide power to the spacecraft, and antennas, which are used on satellite for communication purposes. Many methods have been developed to stow such large components. Many of these methods involve folding about joints or hinges, whether it is done in a simple manner or by more complex designs. Moreover, components that are flexible enough could be rolled or wrapped before they are placed in launch vehicles. This method reduces the mass which the launch vehicle needs to carry, since added mass of joints is eliminated. Low mass is always desirable in space applications. Furthermore, wrapping is very effective at minimizing the volume of a component. These structures store energy inside them as they are wrapped due to the stiffness of their materials. This behavior is identical to that observed in a deformed spring. When the structures are released in space, that energy is released, and thus, they deploy and try to return to their original form. This is due to inertia, where the stored strain energy turns into kinetic energy as the structure deploys. The physical analysis of these structures, which enables their design, is complex and requires computational solutions and numerical modeling. The best design for a given problem can be found through numerical optimization. Numerical optimization uses mathematical approximations and computer programming to give the values of design parameters that would result in the best design based on specified criterion and goals. In this thesis, numerical optimization was conducted for a simple unfurlable structure. The structure consists of a thin rectangular panel that wraps tightly around a central cylinder. The cylinder and panel are connected with a hinge that is a rotational spring with some stiffness. The optimization was solved to obtain the best values for the stiffness of the hinge, the thickness of the panel, which is allowed to vary along its length, and the stiffness or elasticity of the panel's material. The goals or objective of the optimization was to ensure that the deployed panel meets stiffness requirement specified for similar space components. Those requirements are set to make certain that the spacecraft can be controlled from earth even with its large component deployed. Additionally, the second goal of the optimization was to guarantee that the unfurling panel does not have very high energy stored while it's wrapped, so that it would not cause large motion the connected spacecraft in the zero gravity environments of space. A computer simulation was run with the resulting hinge stiffness and panel elasticity and thickness values with the cylinder and four panels connected to a structure representing a spacecraft. The simulation results and deployment animation were assessed to confirm that desired results were achieved.
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Tulloss, Jr Robert Stuart. "Optimization of Geometric Parameters for a Deployable Space Structure." Thesis, Virginia Tech, 2021. http://hdl.handle.net/10919/104873.
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Deployable structures are used for many different spacecraft applications like solar arrays, antennas, and booms. They allow spacecraft with large structural components to comply with the volume restrictions of launch platforms. This research optimizes the shape and size of these structural components with both the stowed and deployed configurations in mind. HEEDS, a commercial optimization software, and ABAQUS, a commercial finite element analysis software, are used to evaluate and alter the structure using a single simulation. This makes the design process more efficient than running many different simulations individually. The optimization objectives, design variables, and constraints are chosen to fit the mission requirements of the structure. The structure analyzed in this research is a composite tube with a compressible cross-section wrapped around a cylinder. The change in cross-section reduces the bending stiffness of the tube and allows it to be wrapped without damaging the material. The dimensions controlling cross-section shape and the thickness of the composite layers are the design variables for the optimization. The maximum strain energy stored in the wrapped tube, the minimum volume of the structure, and the minimum weight of the tube are the objectives for the optimization. The strain energy is maximized to get the stiffest possible structure and satisfy the minimum natural frequency constraint. The weight and volume of the tube are minimized because reducing weight and volume is important for any spacecraft structure. Constraints are placed on the design variables and objectives and the Hashin damage criteria are used to ensure wrapping does not cause material failure. Three optimization runs from different initial designs are completed using SHERPA and genetic algorithm optimization methods. The results are compared to determine which optimization method performs best and how the different starting points affect the final results. After the optimized design is found, the full wrapping and deployment simulation is completed to analyze the behavior of the optimized design.Master of Science
Spacecraft are launched into space using launch vehicles. There is limited room inside the launch vehicle for the spacecraft, but the spacecraft often needs large components like solar panels, antennas, and booms to complete the mission. These components must be designed in a way that allows them to be stowed in a smaller space. This can be accomplished by designing a system that can change the configuration of the component once the spacecraft is in orbit. This is referred to as a deployable structure, and the objective of this research is to create an optimization method for designing this type of structure. This is challenging because both the stowed and deployed configurations must be considered during the optimization. HEEDS, a commercial optimization software, and ABAQUS, a commercial structural analysis software, are used to evaluate and optimize the structure in a single simulation. The optimization objectives, design variables, and constraints are chosen to fit the mission requirements of the structure. The structure examined in this research is a composite tube with a compressible cross-section wrapped around a cylinder. As the tube is wrapped, it flattens, reducing the bending stiffness so the tube can be wrapped without damaging the material. The variables controlling cross-section shape and the thickness of the composite material layers will be altered during the optimization. The maximum strain energy stored in the wrapped tube, the volume of the tube, and the minimum weight of the tube are the objectives for the optimization. The strain energy is maximized to get the stiffest possible tube when it is unwrapped to ensure there is enough stored energy to facilitate the full deployment and to satisfy the minimum natural frequency constraint. The weight and volume of the tube are minimized because reducing weight and volume is important for any spacecraft structure. Constraints are placed on the design variables and objectives and the Hashin damage criteria are used to ensure wrapping does not cause material failure. The Hashin damage criteria use the strength of the material and the stresses on the material to determine if it is likely to fail. Three optimization runs with different starting points are completed for both the SHERPA and genetic algorithm optimization methods. The results are compared to determine which optimization method performs best and how the different starting points affect the final results. After the optimized design is found, the full wrapping and deployment simulation is completed to analyze the behavior of the optimized design.
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Gan, Wei Woei. "Analysis and design of closed-loop deployable frame structure." Thesis, University of Cambridge, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.599290.
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With the advancement of membrane/blanket technology as an alternative choice to the conventional solid panels deployment for assemblies such as solar arrays, solar sails and radar antennas, the need for new ultra-lightweight to deployable frame design is rapidly growing. The demand requires the structure to be more robust, more reliable, have a higher payload-to-area ratio and easier to control. Answering the call is a frame structure consisting of rigid bars and mechanical joints, which should ideally have only one uniquely defined mechanism and a relatively high packaging ratio. Presented herewith is a systematic study of the kinematics of the family of structures in numerical way. We are able to reveal considerable insights of the structural mechanism which can be obtained through careful study of singular values and rank deficit of the kinematic matrix of a structure, from which issues important for design, such as sensitivity can be analysed. The study also enables the simulation of deployment of structure with certain degrees of manufacture imperfection where under rigid body hypothesis, has no mechanism. Presented also is a novel deployable structure which belongs to a spatial over-constrained mechanical linkages family. Consisting of six bars, this structure can form an expanded quadrilateral rectangular frame and folded up to a compact bundle. Our analysis and experimental results both confirm that the structure has only one mechanism along its deployment path. The mechanism appears to be a favourable potential for deploying and supporting flexible active surface of solar/radar structures, as its two outer and opposite bars always remain parallel throughout the whole deployment process. With the development of this analytical approach, considerable insights into the kinematic behaviour of spatial over-constrained linkages can be revised and analysed. It has also become possible to design assemblies with special properties, e.g. frame with some particular dimension or non-symmetry.
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Jian, Bingcong. "Origami-based design for 4D printing of deployable structures." Thesis, Bourgogne Franche-Comté, 2020. http://www.theses.fr/2020UBFCA029.
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Les structures déployables peuvent être déformées entre les différentes configurations par des mécanismes prédéterminés, ce qui montre le grand potentiel de nombreuses applications d'ingénierie. Cependant, leurs mécanismes complexes rendent également très difficile la conception de leur structure. Avec les développements croissants en impression 4D, ses caractéristiques d'auto-transformation sous des stimuli externes offrent de nouvelles possibilités pour le déploiement de structures actives, complexes et difficiles. En outre, l'ingénierie basée sur les origamis a fourni un soutien technique considérable pour la transformation des structures, en particulier en passant par les états 2D à 3D, ce qui a conduit à de nombreuses études de conception basées sur des structures déployables inspirées de l'origami. Toutefois, la relation complexe entre la géométrie de la structure déployable et les matériaux et paramètres techniques connexes de l'impression 4D n'a pas été étudiée en profondeur. Actuellement, le manque de méthodologie de conception basée sur les origamis pour l'impression 4D fait toujours défaut. Dans ce travail de recherche, nous nous concentrons sur l'exploration des connexions internes entre les multiples niveaux d'abstraction allant de la structure globale du produit et l'affectation spécifique des matériaux et la conception géométrique afin d'aligner la bonne stratégie de conception sur une technique d'impression 4D spécifique. En bref, ce travail se veut être une ligne directrice pour la conception de structures actives déployables. Pour démontrer cet objectif, nous avons d'abord introduit les informations de base de l'impression 4D, de la conception basée sur les origamis et des structures déployables. Ensuite, nous avons analysé et résumé l'état d'avancement de leurs recherches et les difficultés existantes. Ensuite, nous proposons un cadre de conception systématique pour la conception de structures actives par impression 4D. Chaque étape de l'ensemble du processus de conception est présentée en détail, en particulier la conception de modèles d'origami basée sur la stratégie "3D-2D-3D" et la planification et le contrôle de la séquence de pliage. Enfin, sur la base des connaissances existantes, nous appliquons ce processus de conception à la structure active déployable et fournissons quelques études de cas illustrativesDeployable structures can be deformed between the different configurations through predetermined mechanisms, showing the great potential in many engineering applications. However, their exquisite and intricate mechanisms also bring a great difficulty to the design of its structure. With the growing 4D printing efforts, its self-transforming characteristics under external stimuli provide new possibilities for deploying complex and challenging driving structures. Furthermore, origami-based engineering has provided tremendous technical support for structural conversion, especially from 2D to 3D states, leading to many design studies based on origami-inspired deployable structures. However, the complicated relationship between the deployable structure's geometry and the related materials and engineering parameters of 4D printing has not been thoroughly explored. Currently, the origami-based design methodology for 4D printing is still missing. In this research work, we focus on exploring the internal connections between the multiple abstraction levels over the overall product structure to the specific material allocation and geometric design to make the right design strategy aligned to a specific 4D printing technique. In short, this work intends to be a guideline for designing active deployable structures. To demonstrate this objective, we first introduced the basic information of 4D printing, origami-based design, and deployable structures. Then we analyzed and summarized their research status and existing difficulties. Secondly, we propose a systematic design framework for active structure design by 4D printing. Each step in the entire design process is then introduced in detail, especially the origami pattern design based on the "3D-2D-3D" strategy and the folding sequence planning and control. Finally, based on the existing knowledge, we apply this design process to the active deployable structure and provide some illustrative case studies
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Huang, Weimin. "Shape memory alloys and their application to actuators for deployable structures." Thesis, University of Cambridge, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.299009.
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Dahl, Marcus. "Design and Construction of a Self-Deployable Structure for the Moon House Project." Thesis, KTH, Lättkonstruktioner, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-185024.
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This master thesis describes the design and construction of a prototype for the Moon House project. The goal was to develop a structural concept which ultimately will allow a 2 × 2.5 × 3 m3 house to be deployed on the surface of the Moon as an art installation. A 1 to 5 scale model was built and tested. Provided is background information on lightweight and inflatable technology for space applications. This is then reviewed together with earlier work related to the Moon House project in order to come up with a feasible design. The structure consists of a frame made out of plain-weave glass fiber tape springs. These are joined with plastic connectors and the frame is covered in a thin rip-stop polyester film. Elastic folds and pin-jointed hinges allow the structure to be folded, thus reducing its stowed volume. Deployment of the house is achieved with a combination of pressurization and elastically stored strain energy in the tape springs from folding of the structure. The tape springs have been tailored using specific lay-up and geometry to achieve an efficient folding scheme. The final structure was designed in Solid Edge and connectors were 3D-printed in plastic material. Deployment tests have been performed with partial success. Points of improvement have been identified and recommendations are made for future work.Detta examensarbete behandlar design och konstruktion av en prototyp för Månhusprojektet. Målet var att ta fram ett strukturellt koncept för en stuga med dimensionerna 2 × 2, 5 × 3 m3 som skall kunna veckla ut sig själv på månens yta. En modell i skala 1 till 5 byggdes och testades. Rapporten innehåller bakgrundsinformation om olika konstruktioner, uppblåsbara och utfällningsbara, för rymdapplikationer. Detta utvärderas sedan, tillsammans med tidigare arbete relaterat till projektet, mot kravspecifikationer, f¨or att ta fram en ny design. Resultatet ¨ar en struktur bestående av s.k. “Tape springs” tillverkade i vävd glasfiber. De olika elementen kopplas samman med skarvar av plast. Detta utgör en ram, som sedan kläds med tunn rip-stop polyester. Elastiska veck kombinerat med mekaniska gångjärn gör att strukturen kan packas ihop till en mindre volym. Utfällning av strukturen möjliggörs med en kombination av trycksättning och elastiskt lagrad energi från den påtvingade vikningen. Genom att variera laminatens egenskaper och geometri fås strukturella element som ger ett effektivt vikningsschema. Strukturen togs fram med hjälp av Solid Edge ST6 och plastskarvarna 3D-printades. Test av utfällningen har gjorts med delvis lyckade resultat. Problem och potentiella förbättringar har identifierats och rekommendationer ges för fortsatt utveckling av konceptet.
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Nelson, Todd G. "Art to Engineering: Curved Folding and Developable Surfaces in Mechanism and Deployable Structure Design." BYU ScholarsArchive, 2018. https://scholarsarchive.byu.edu/etd/6865.
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This work investigates how curved-crease origami and the developable surfaces which compose it can be transitioned to engineering design. Methods for creating flexible, tailorable-property surfaces that function as thick panels in place of paper are presented. Concepts from curved-crease origami and developable surfaces that can describe and extend engineering applications are discussed and demonstrated. These concepts are particularly beneficial to applications where curved surfaces are integral to the function, deployability is desired, and planar manufacturing could be beneficial.The first part of this work uses arrays of compliant elements to create flexible-tailorable property surfaces. The key feature to these arrays is the alignment of the most flexible bending axis of the individual elements to the ruling line arrangement of a developable surface. This alignment can enable bending of thick panels while maintaining lower stresses, a quality necessary for the transitioning of curved-crease origami into thick materials. The stiffness and stress of these arrays is modeled and physical prototypes are demonstrated. Additionally, shape factors are developed for these compliant arrays (CAs) to facilitate material selection for the panels and understand how the geometry of the array changes the effective properties of the panel. The second part of this work describes and demonstrates several concepts of curved-crease origami and developable surfaces that can benefit mechanism and structure design, particularly in the context of rolling-contact mechanisms. The design of a rolling-contact joint connected by flexible bands similar to a Jacob's Ladder toy is extended through incorporating curved creases into the design. The resulting design is deployable from a compact state to a functional state and can be manufactured from a single plane and folded into shape. Mathematical formulations are presented to describe the classes of developable surfaces in terms of properties which are frequently important in mechanism design. These natural equations for a single class of developable surface are conducive to modeling the folding motion of rigid-ruling developables, developables whose ruling lines do change location in a surface during folding. These formulations are used to generalize the design of rolling-contact joints to a family of joints capable of single degree of freedom spatial motions, being manufactured from a plane, and exhibiting a tailorable force response. Finally practical design suggestions for the implementation of rolling-contact joints is given. These include methodology to create sunken flexures which serve to increase the normal force between rolling bodies to prevent slip.
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Smith, Samuel Porter. "Development of an Origami Inspired Composite Deployable Structure Utilizing Compliant Joints as Surrogate Folds." BYU ScholarsArchive, 2021. https://scholarsarchive.byu.edu/etd/9270.
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This work presents the design and construction of a self-deployable, self-stiffening,and retractable (SDSR) space array from carbon fiber reinforced polymers (CFRP’s) and a working prototype is demonstrated. The effort required developing principles for the design of high-strain composite flexural joints and their integration into angled composite panels. Designing LET arrays in angled panels is explored. Analysis of simple composite LET joints is presented for two degrees of freedom. Validation of the composite LET modeling is sought through numerical methods and empirical testing. Testing of several composite LET joint specimens is conducted and the results are reported. Results indicate that (while not as compact as their isotropic material counterparts) composite laminates can successfully use LET joints as surrogate folds.
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Donley, Stephen John. "Initial identification and investigation of parameters for choosing the most appropriate rapidly assembled or deployable structure." Thesis, Springfield, Va. : Available from National Technical Information Service, 2001. http://handle.dtic.mil/100.2/ADA393183.
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ACCETTURA, ANTONIO GABRIELE. "Self-deployable structures for advanced space applications: analysis, design and small scale testing." Doctoral thesis, Università degli Studi di Roma "Tor Vergata", 2014. http://hdl.handle.net/2108/203118.
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The aim of this PhD project is to evaluate, design, manufacture and test Self-
Deployable structures using a Shape Memory Composite (SMC) technology to be
used on advanced space applications, including both small and large space
structures such as solar sails, antennas, solar panels and de-orbiting systems. This
technology can also enable innovative missions from debris capture to solar system
exploration and more. In particular SMPs based mechanisms are here proposed,
and feasibility is demonstrated by means of experimental tests targeted to show
their suitability to space applications.
After a review on space mechanisms and SMC applications, selected designs have
been proposed and test campaigns have been performed, including material
characterization and the deployment of small scale prototypes. Even if this is only a
starting point, achieved results are in accordance with literature and provide an
original contribution to the self-deployable structures for space applications.
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King, Jonathan Lee. "Artifacts of Questions Asked." Thesis, Virginia Tech, 2009. http://hdl.handle.net/10919/76901.
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The cyclic trajectory described here exemplifies a loosely defined, continuously evolving set of questions, results, and methodologies that have emerged during the process of design by making. Through a series of prototypical building components and assemblies this collection presents a design process that began with a top-down program-specific design process that informed the development of a unique building system and enabled a bottom up formal exploration. As the design thesis for the first professional Master of Architecture degree, this exploration surrounds the design, fabrication, and deployment of a series of component-based building assemblies. One example, the SEEDS Pavilion At Hawks Ridge, serves as a remote base of operations for a local youth organization that supports field-based environmental education. The pavilion continues an investigation of user assembled construction and is based on a component group that can be assembled on-site by camp children. Each building component was manufactured using on campus fabrication laboratories and was assembled on-site by a group of supervised SEEDS camp student-volunteers during a two-day design-build workshop at the Hawk's Ridge Preserve in Floyd, Virginia. The form of the structure is derived by the limitation of component number, size, and assembly sequence and represents the conflict between a parametrically derived prescriptive shape and the forms that result from the bottom up exploration of the physical system itself. The component-based construction is made possible by a series of nodal linkage assemblies designed to accommodate variations in on-site conditions using a strategic 'sloppy detail' that enables a high degree of assembly and deployment tolerance. The following collection of sequential images outlines construction of several prototypical components and assemblies and is intended to represent a continuance, not an end, to a long-term effort.Master of Architecture
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Estrada, Diana M. Eng Massachusetts Institute of Technology. "Conceptual design of a deployable vehicular bridge structure using shape and geometric optimization for post disaster relief applications." Thesis, Massachusetts Institute of Technology, 2018. http://hdl.handle.net/1721.1/119316.
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Thesis: M. Eng., Massachusetts Institute of Technology, Department of Civil and Environmental Engineering, 2018.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 61-64).
In the aftermath of a natural disaster, all efforts are dedicated to a common goal: repairing and bringing the affected communities back to their fully functioning condition. However, it is frequently encountered that infrastructure and roads providing access to these communities are also damaged. As this can slow down the community response time significantly, there exists a need for light, easy to install, and effective temporary infrastructure for immediate restoration of communication. This thesis presents a new design concept for a deployable bridge structure composed of scissor-like translational units. The proposed structure satisfies the deployment constraints and the stress limits determined by AASHTO LRFD Bridge Design Specifications. The used design approach uses multiple existing deployable geometries and performs a comparative analysis between the different systems. Given the particularity of SLE units, a standard finite element analysis method was enriched to match our conditions and enhance the accuracy of the modeling and analysis. This includes the implementation of master/slave node constraints and zero length rotational springs at the element nodes. The design problem is formulated as a formal optimization problem with a nested equilibrium condition. Our objective function minimizes the total weight of the structure for a deployable bridge subjected to H15 design loads and stress limits delineated by AASHTO. A design A design exploration is performed to compare the best designs for different bridge geometries, angles of element inclination and member cross sectional areas. The optimization problem is solved using a genetic algorithm which, at each iteration, uses our beam finite element analysis to check that structural equilibrium is satisfied. Given the potential lack of resources after a natural disaster, providing a light weight extendible structure which would therefore require less force and resources for installation, can have a positive impact in the recovery process.
by Diana Estrada.
M. Eng.
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Mao, Huina. "Numerical and Experimental Studies of Deployment Dynamics of Space Webs and CubeSat Booms." Doctoral thesis, KTH, Farkost och flyg, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-206594.
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In this thesis, experiments and simulations are performed to study the deployment dynamics of space webs and space booms, focusing on the deployment and stabilization phases of the space web and the behavior of the bi-stable tape spring booms after long-term stowage. The space web, Suaineadh, was launched onboard the sounding rocket REXUS-12 from the Swedish launch base Esrange in Kiruna on 19 March 2012. It served as a technology demonstrator for a space web. A reaction wheel was used to actively control the deployment and stabilization states of the 2×2 m2 space web. After ejection from the rocket, the web was deployed but entanglements occurred since the web did not start to deploy at the specified angular velocity. The deployment dynamics was reconstructed by simulations from the information recorded by inertial measurement units and cameras. Simulations show that if the web would have started to deploy at the specified angular velocity, the web would most likely have been deployed and stabilized in space by the motor, reaction wheel and controller used in the experiment. A modified control method was developed to stabilize the out-of-plane motions before or during deployment. New web arms with tape springs were proposed to avoid entanglements. A deployable booms assembly composed of four 1-m long bi-stable glass fiber tape springs was designed for the electromagnetically clean 3U CubeSat Small Explorer for Advanced Missions (SEAM). The deployment dynamics and reliability of the SEAM boom design after long-term stowage were tested by on-ground experiments. A simple analytical model was developed to predict the deployment dynamics and to assess the effects of the GOLS and the combined effects of friction, viscoelastic strain energy relaxation, and other factors that act to decrease the deployment force. In order to mitigate the viscoelastic effects and thus ensure self-deployment, different tape springs were designed, manufactured and tested. A numerical model was used to assess the long-term stowage effects on the deployment capability of bi-stable tape springs including the friction, nonlinear-elastic and viscoelastic effects. A finite element method was used to model a meter-class fully coiled bi-stable tape spring boom and verified by analytical models.QC 20170508
SEAM
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Jensen, Frank Vadstrup. "Concepts for retractable roof structures." Thesis, University of Cambridge, 2005. https://www.repository.cam.ac.uk/handle/1810/251952.
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Over the last decade there has been a worldwide increase in the use of retractable roofs for stadia. This increase has been based on the flexibility and better economic performance offered by venues featuring retractable roofs compared to those with traditional fixed roofs. With this increased interest an evolution in retractable roof systems has followed. This dissertation is concerned with the development of concepts for retractable roof systems. A review is carried out to establish the current state-of-the-art of retractable roof design. A second review of deployable structures is used to identify a suitable retractable structure for further development. The structure chosen is formed by a two-dimensional ring of pantographic bar elements interconnected through simple revolute hinges. A concept for retractable roofs is then proposed by covering the bar elements with rigid cover plates. To prevent the cover plates from inhibiting the motion of the structure a theorem governing the shape of these plate elements is developed through a geometrical study of the retractable mechanism. Applying the theorem it is found that retractable structures of any plan shape can be formed from plate elements only. To prove the concept a 1.3 meter diameter model is designed and built. To increase the structural efficiency of the proposed retractable roof concept it is investigated if the original plan shape can be adapted to a spherical surface. The investigation reveals that it is not possible to adapt the mechanism but the shape of the rigid cover plates can be adapted to a spherical surface. Three novel retractable mechanisms are then developed to allow opening and closing of a structure formed by such spherical plate elements. Two mechanisms are based on a spherical motion for the plate elements. It is shown that the spherical structure can be opened and closed by simply rotating the individual plates about fixed points. Hence a simple structure is proposed where each plate is rotated individually in a synchronous motion. To eliminate the need for mechanical synchronisation of the motion, a mechanism based on a reciprocal arrangement of the plates is developed. The plate elements are interconnected through sliding connections allowing them mutually to support each other, hence forming a self-supporting structure in which the motion of all plates is synchronised. To simplify the structure further, an investigation into whether the plate elements can be interconnected solely through simple revolute joints is carried out. This is not found to be possible for a spherical motion. However, a spatial mechanism is developed in which the plate elements are interconnected through bars and spherical joints. Geometrical optimisation of the motion path and connection points is used to eliminate the internal strains that occur in the initial design of this structure so a single degree-of-freedom mechanism is obtained. The research presented in this dissertation has hence led to the development of a series of novel concepts for retractable roof systems.
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Maetz, Xavier. "Développement et caractérisation expérimentale en microgravité de structures auto-déployables de réflecteurs paraboliques pour applications spatiales." Electronic Thesis or Diss., Université de Montpellier (2022-....), 2022. http://www.theses.fr/2022UMONS084.
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La miniaturisation des satellites représente un défi technologique important pour l'accès à l'espace en réduisant les coûts et les délais de développement. L'augmentation considérable des lancements de nanosatellites est une preuve de leur intérêt dans de multiples applications. Les antennes paraboliques réflectrices sont largement utilisées pour des applications de télécommunication, d'observation de la terre, de navigation et de science (exploration de l'espace lointain). C'est la solution la plus utilisée pour des antennes satellitaires qui ont besoin d'un gain élevé, car elles possèdent un bon rendement et peuvent supporter n'importe quelle polarisation. En général, le diamètre d'une antenne à géométrie fixe va dépendre de la taille et de la capacité d'aménagement de la plateforme du satellite. Mais quand une antenne à géométrie fixe n'est pas envisageable, alors une architecture déployable est considérée. Avec les petits satellites comme les MicroSats et les CubeSats, une antenne parabolique doit obligatoirement être une structure déployable. Cette thèse réalisée au Laboratoire de Mécanique et Génie Civil (LMGC) de Montpellier, cofinancée par le Centre National d'Etudes Spatiales (CNES) et la région Occitanie, s'inscrit dans la continuité d'une collaboration entre le service mécanisme du CNES et la partie structure innovante de l'équipe SIGECO du LMGC. L'objectif est de proposer un concept de structure porteuse de réflecteurs auto-déployables à l'échelle des CubeSats. Ce sont des structures qui sont pliées pour obtenir une configuration gerbée compacte lors du lancement, et qui présentent une bonne tenue mécanique en configuration déployée. Le passage entre les deux configurations s'effectue uniquement par libération d'énergie élastique stockée dans des joints, sans apport d'énergie extérieure. Afin d'assurer le déploiement fiable et précis des mécanismes envisagés, il faut être capable de comprendre et de modéliser le comportement des structures. L'approche proposée associe donc modélisation, conception, prototypage et caractérisation expérimentale. Les travaux de cette thèse ont menés à la fabrication et l'intégration de deux prototypes de type EM (Engineering Model). Afin de valider le modèle de ces réflecteurs, les prototypes ont été déployés et testés dans en environnement de microgravité, pendant une campagne de 3 vols paraboliquesThe miniaturization of satellites represents a significant technological challenge for access to space by reducing costs and development times. The considerable increase in nanosatellite launches is a proof of their interest in multiple applications. Reflective parabolic antennas are widely used for telecommunication, earth observation, navigation and science (deep space exploration) applications. It is the most used solution for satellite antennas that need high gain, because they have good performance and can support any polarization. In general, the diameter of a fixed geometry antenna will depend on the size and layout capability of the satellite platform. But when a fixed geometry antenna is not possible, then a deployable architecture is considered. With small satellites like MicroSats and CubeSats, a satellite parabolic antenna must be a deployable structure. This thesis carried out at the Laboratory of Mechanics and Civil Engineering (LMGC) in Montpellier, co-financed by the National Center for Space Studies (CNES) and the Occitanie region, is part of the collaboration between the mechanism department of CNES and the innovative structure part of the SIGECO team of the LMGC. The objective is to propose a concept of structure for self-deployable reflectors on the scale of CubeSats. These structures are folded to obtain a compact stacked configuration during launch, and have good mechanical strength in the deployed configuration. The passage between the two configurations is carried out only by the release of elastic energy stored in the joints, without any external energy input. In order to ensure the reliable and precise deployment of the mechanisms, it is necessary to be able to understand and model the behavior of the structures. The proposed approach combines modeling, design, prototyping and experimental characterization. The work of this thesis led to the fabrication and integration of two EM (Engineering Model) prototypes. In order to validate the model of these reflectors, the prototypes were deployed and tested in a microgravity environment, during a campaign of 3 parabolic flights
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Hernández, Merchan Carlos Henrique. "Deployable structures." Thesis, Massachusetts Institute of Technology, 1987. http://hdl.handle.net/1721.1/14970.
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Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Architecture, 1987.MICROFICHE COPY AVAILABLE IN ARCHIVES AND ROTCH.
Bibliography: leaves 20-21.
This thesis has the purpose of describing the meaning and applications of deployable structures (making emphasis in the scissor-hinged and sliding mechanisms.) and the development of new geometries, details, and mechanisms that make these systems buildable and useful for architectural applications. A deployable structure is one that can be transformed, with the addition of an energy input, from a closed stage or compact configuration to a predetermined, stable expanded form. Deployable structures are suitable in response to the following needs: a- A situation in which there is a need to create enclosed or protected space for a short period of time and then move that space to another location for erection or storage. b- Difficult access places, and/or lack of labor. c- Special applications equipment and shelters for special equipment which can not be transported in full open size and needs to be erected in a very quick way. d- Need to enclose space due to variable weather conditions. e- Situations of high risk with elevated labor costs, hostile environments, costly transportation. f- Construction aid. g- As a construction method There are many mechanisms which fall into the category of deployable structures, but we can group them into two general categories: A) Struts Structures : scissor-hinged, tensile, and sliding mechanisms, etc. B) Surface Structures : folded, inflatable, telescopic, etc. The general characteristic of group A is that these structures are made out of struts which commonly work as compression, tension or bending components connected by joints or hinges. In Group B stresses are carried by surfaces. In some, cases a continuous surface carries only tension forces like, in pressurized or inflatable construction; other structures are made out of small surfaces or planes joined together by some usually flexible means of forming a continuous structure. Deployability implies an extra cost over an assembly structure due to more sophisticated, expensive, movable connections, locking mechanisms, and deployment mechanisms. This extra cost has to be balanced by the structure's greater potential for adaptability, mobility, and labor saving construction.
by Carlos Henrique Hernández Merchan.
M.S.
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Fenci, G. E. "Biomimetic deployable structures." Thesis, University of Salford, 2018. http://usir.salford.ac.uk/47185/.
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Modern architectural designs aim at creating dynamic and flexible spaces, able to adapt to the ever-changing environment by virtue of temporary and convertible structures. Biomimetics is the applied science that, through the imitation of nature, finds the solution to human problems. By observing motions that occur in nature, for example, the blooming of a flower or the unfolding of wings, inspiration can be drawn for the design of deployable structures with applications ranging from aerospace engineering through to disaster relief shelters. Analysis of deployable structures has proven to be challenging due to the non-linear behaviour and continuously changing geometry. This research project aims to propose a design process, which will enable the analysis of deployable structures with multiple degrees of freedom and their deployment sequences, along with allowing for optimisation of design parameters, such as material use or deployment energy required. The optimisation methodology involves the synthesis of a deployable system into a parametric geometry the configuration of which is determined by a series of variable parameters representing the degrees of freedom. Through the application of engineering judgement to set up the optimisation criteria it is possible to optimise the way in which the degrees of freedom vary relatively to one another in the process of reaching the full deployed configuration by generating the least amount of stress, force or displacement in the structural elements. At the same time, a classification of existing deployable structures will bring clarity and order to the variety and diversity existing within this research area. By critically appraising previously published reviews and classifications of deployable structures, the lack of an organic and comprehensive study became evident. This review brought to the proposal of a new classification table based on overcoming the shortcomings observed during the reviewing process with the purpose of aiding a better understanding of such a vast and complex subject and offering a common classifying order for future work to be based on.
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Chen, Yan. "Design of structural mechanisms." Thesis, University of Oxford, 2003. http://ora.ox.ac.uk/objects/uuid:6423e5a6-5438-496a-835d-242fe1d5cd97.
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In this dissertation, we explore the possibilities of systematically constructing large structural mechanisms using existing spatial overconstrained linkages with only revolute joints as basic elements. The first part of the dissertation is devoted to structural mechanisms (networks) based on the Bennett linkage, a well-known spatial 4R linkage. This special linkage has been used as the basic element. A particular layout of the structures has been identified allowing unlimited extension of the network by repeating elements. As a result, a family of structural mechanisms has been found which form single-layer structural mechanisms. In general, these structures deploy into profiles of cylindrical surface. Meanwhile, two special cases of the single-layer structures have been extended to form multi-layer structures. In addition, according to the mathematical derivation, the problem of connecting two similar Bennett linkages into a mobile structure, which other researchers were unable to solve, has also been solved. A study into the existence of alternative forms of the Bennett linkage has also been done. The condition for the alternative forms to achieve the compact folding and maximum expansion has been derived. This work has resulted in the creation of the most effective deployable element based on the Bennett linkage. A simple method to build the Bennett linkage in its alternative form has been introduced and verified. The corresponding networks have been obtained following the similar layout of the original Bennett linkage. The second effort has been made to construct large overconstrained structural mechanisms using hybrid Bricard linkages as basic elements. The hybrid Bricard linkage is a special case of the Bricard linkage, which is overconstrained and with a single degree of mobility. Starting with the derivation of the compatibility condition and the study of its deployment behaviour, it has been found that for some particular twists, the hybrid Bricard linkage can be folded completely into a bundle and deployed to a flat triangular profile. Based on this linkage, a network of hybrid Bricard linkages has been produced. Furthermore, in-depth research into the deployment characteristics, including kinematic bifurcation and the alternative forms of the hybrid Bricard linkage, has also been conducted. The final part of the dissertation is a study into tiling techniques in order to develop a systematic approach for determining the layout of mobile assemblies. A general approach to constructing large structural mechanisms has been proposed, which can be divided into three steps: selection of suitable tilings, construction of overconstrained units and validation of compatibility. This approach has been successfully applied to the construction of the structural mechanisms based on Bennett linkages and hybrid Bricard linkages. Several possible configurations are discussed including those described previously. All of the novel structural mechanisms presented in this dissertation contain only revolute joints, have a single degree of mobility and are geometrically overconstrained. Research work reported in this dissertation could lead to substantial advancement in building large spatial deployable 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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Guest, Simon David. "Deployable structures : concepts and analysis." Thesis, University of Cambridge, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.336615.
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Yee, Jeffrey Cheze Hui. "Thin CFRP composite deployable structures." Thesis, University of Cambridge, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.614308.
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Tibert, Gunnar. "Deployable Tensegrity Structures for Space Applications." Doctoral thesis, KTH, Mekanik, 2002. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3317.
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Fischer, Annette. "Gravity compensation of deployable space structures." Thesis, University of Cambridge, 2001. https://www.repository.cam.ac.uk/handle/1810/251764.
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Gravity compensation suspension systems are essential to support space structures during tests on Earth, but also impose constraints on the structures that have the effect of changing their behaviour. These constraints, except for those exactly offloading the self-weight, have to be minimised in order to replicate as closely as possible the zero-g conditions of space. The deployable structure that is used for the research carried out is a model of a rigid panel type solar array which is able to deploy and retract automatically. A computational and experimental study of the interaction of this structure with a manually adjustable suspension system, during quasistatic deployment tests, is presented. A methodology is established for modelling this interaction, for predicting the effects of suspension system adjustments, and for optimisation of the suspension system through these adjustments. It was found that some improvements can be achieved by manual adjustment, but further optimisation requires an active system. The two significant substructures of the active system that has been built are: a horizontally deploying support mechanism that mirrors the test structure, and seven suspension devices that contain strain gauges and displacement transducers and adjust the length of vertical suspension cables by a screw and nut actuator. A computational representation of the active suspension system is established, partly from theoretical methods and partly from measurements through which the structural properties have been identified, and the interaction between the active suspension and the solar array is investigated. Two different gravity compensation strategies, displacement control and force control, are implemented. Experiments carried out with the active suspension system are presented for these two schemes and their gravity compensation capability is evaluated and compared. It was found that gravity can be compensated by controlling the forces in the suspension elements to between 10% and 20% of g, however by controlling the displacements, the compensation is more than twice as bad. The latter strategy was, in practice, only marginally better than the passive system. Better results would have been possible with actuators having a higher positioning accuracy. This research has shown that a system with a self-deploying overhead structure, and active vertical suspension elements is a good concept for multi-point gravity compensation and should be further developed.
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Gantes, Charalambos. "A design methodology for deployable structures." Thesis, Massachusetts Institute of Technology, 1991. http://hdl.handle.net/1721.1/13901.
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Wolfe, Maxwell H. (Maxwell Henry). "Analysis of deployable strut roof structures." Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/82827.
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Thesis (M. Eng.)--Massachusetts Institute of Technology, Department of Civil and Environmental Engineering, 2013.Cataloged from PDF version of thesis. "June 2013."
Includes bibliographical references (pages 55-56).
Deployable structures are structures that can change shape from a compact to an expanded form. Thus, their advantage over conventional structures is adaptability, whether in the sense of adapting to changing environmental conditions or being adapted for repeated transportation and deployment. These features make deployable structure highly desirable for a wide range of applications in the aerospace, military, and architectural fields. However, these structures are often only designed as small scale "products", rather than structures requiring full analysis and design procedures. Much work has focused on the various geometries of the deployment mechanisms without considering practical engineering aspects. If deployable structures are to be designed on the scale of large civil structures, a proper understanding of the flow of forces through the structure is required. This thesis begins with a brief discussion of deployable structures in general before moving on to geometric constraints of strut-type deployable structures. Then, it details a preliminary analysis of one class of deployable structures, known as angulated element structures. These structures are designed to be operable roofs spanning over sports facilities. During deployment, the center of the structure opens or closes to accommodate changes in weather conditions. Building on the geometry established in other work, the relationships between the basic geometric parameters of angulated element rings and their structural characteristics are determined. SAP2000 analysis results are used to make specific design recommendations. The feasibility of using this type of structure for an operable long span roof is confirmed.
by Maxwell H. Wolfe.
M.Eng.
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Watt, Alan Morrison. "Deployable structures with self-locking hinges." Thesis, University of Cambridge, 2003. https://www.repository.cam.ac.uk/handle/1810/272077.
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You, Zhong. "Deployable structures for masts and reflector antennas." Thesis, University of Cambridge, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.240014.
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Munro, Logan. "Investigation of deployable structures and their actuation." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/40447.
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Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2007.Includes bibliographical references (p. 27).
Deployable Structures had not been designed for use in the oil field industry, and additionally have not been designed as devices to perform mechanical work. By analyzing deployable structures a detailed understanding of the mechanism kinematics has been developed. Further, we have analyzed new design concepts of deployable structures that include void filling alterations and snap fit strengthening. The actuation and mechanical loading of the structures and the input to output force ratio were investigated. This understanding was applied to several actuation methods.
by Logan Munro.
S.B.
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Giesecke, Ken 1976. "Deployable structures inspired by the origami art." Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/30075.
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Thesis (M.Arch.)--Massachusetts Institute of Technology, Dept. of Architecture, 2004.Includes bibliographical references (p. 60-63).
My thesis is an exploration of design methods and tools using origami as a vehicle to test their usefulness and coming to terms with their limitations. I have taken my fascination with a particular development in origami and put my belief in its potential for architectural application to the test by way of various investigations: materials and structural analysis, mathematical reasoning, manipulating space and form, parametric modeling, fabrication, and finite element testing. Parting from conventional, figural forms, mathematicians developed open-surface forms together with theorems that governed the ability of these folded forms to fold flat. I selected a particular form, the Kao-fold, for its simplicity, beauty, and structural properties and imagined many exciting possibilities, specifically for its application in designing a deployable structure. I analyzed its crease pattern, exploring variations and their corresponding folded forms. Simultaneously, different material ideas for larger-scale structures were tested and a particular configuration was assessed for internal stresses and its structural stability. Its transformation from a flat sheet to a folded state was scrutinized under the lens of mathematical reasoning, namely trigonometry, by linking the acute angle of its crease pattern and the dihedral angle in its folded state to its final folded configuration. The rigidity of this investigation was offset by the freedom afforded in manipulating paper models. As such, different spatial qualities and forms were explored while addressing the issue of scale and potential applications.
(cont.) The transformational characteristics discovered were digitally simulated via the construction of parametric models, which was a more controlled manipulation of the form in a virtual space. In order to go beyond the realm of representation and address real-life building issues, a temporary open-air shelter was designed and constructed in detail. The goal was to tackle the complexity of assigning materials, designing components and fabricated them. As a final endeavor, the model's construction was tested for its structural stability using a finite element software.
by Ken Giesecke.
M.Arch.
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Kiper, Gokhan. "Design Methods For Planar And Spatial Deployable Structures." Phd thesis, METU, 2011. http://etd.lib.metu.edu.tr/upload/12613519/index.pdf.
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This thesis study addresses the problem of overconstraint via introduction of conformal polyhedral linkages comprising revolute joints only and investigation of special geometric properties for the mobility of such overconstrained linkages. These linkages are of particular interest as deployable structures. First, planar case is issued and conditions for assembling irregular conformal polygonal linkages composed of regular and angulated scissor elements are derived. These planar assemblies are implemented into faces of polyhedral shapes and radially intersecting planes to obtain two different kind of polyhedral linkages. Rest of the thesis work relates to spatial linkages. Identical isosceles Bennett loops are assembled to obtain regular polygonal linkages and many such linkages are assembled to form polyhedral linkages. Then, Fulleroid-like linkages are presented. After these seemingly independent linkage types, Jitterbug-like linkages are introduced. Based on some observations on present linkages in the literature a definition for Jitterbug-like linkages is given first, and then a set of critical properties of these linkages are revealed. This special type of polyhedral linkages is further classified as being homothetic and non-homothetic, and geometric conditions to obtain mobile homothetic Jitterbug-like polyhedral linkages are investigated. Homohedral linkages, linkages with polyhedral supports with 3- and 4-valent vertices only, tangential polyhedral linkages are detailed as special cases and the degenerate case where all faces are coplanar is discussed. Two types of modifications on Jitterbug-like linkages are presented by addition of links on the faces and radial planes of Jitterbug-like linkages. Finally, a special class of Jitterbug-like linkages - modified Wren platforms are introduced as potential deployable structures.
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Viquerat, Andrew David. "Polynomial continuation in the design of deployable structures." Thesis, University of Cambridge, 2012. https://www.repository.cam.ac.uk/handle/1810/241496.
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Polynomial continuation, a branch of numerical continuation, has been applied to several primary problems in kinematic geometry. The objective of the research presented in this document was to explore the possible extensions of the application of polynomial continuation, especially in the field of deployable structure design. The power of polynomial continuation as a design tool lies in its ability to find all solutions of a system of polynomial equations (even positive dimensional solution sets). A linkage design problem posed in polynomial form can be made to yield every possible feasible outcome, many of which may never otherwise have been found. Methods of polynomial continuation based design are illustrated here by way of various examples. In particular, the types of deployable structures which form planar rings, or frames, in their deployed configurations are used as design cases. Polynomial continuation is shown to be a powerful component of an equation-based design process. A polyhedral homotopy method, particularly suited to solving problems in kinematics, was synthesised from several researchers' published continuation techniques, and augmented with modern, freely available mathematical computing algorithms. Special adaptations were made in the areas of level-k subface identification, lifting value balancing, and path-following. Techniques of forming closure/compatibility equations by direct use of symmetry, or by use of transfer matrices to enforce loop closure, were developed as appropriate for each example. The geometry of a plane symmetric (rectangular) 6R foldable frame was examined and classified in terms of Denavit-Hartenberg Parameters. Its design parameters were then grouped into feasible and non-feasible regions, before continuation was used as a design tool; generating the design parameters required to build a foldable frame which meets certain configurational specifications. Two further deployable ring/frame classes were then used as design cases: (a) rings which form (planar) regular polygons when deployed, and (b) rings which are doubly plane symmetric and planar when deployed. The governing equations used in the continuation design process are based on symmetry compatibility and transfer matrices respectively. Finally, the 6, 7 and 8-link versions of N-loops were subjected to a witness set analysis, illustrating the way in which continuation can reveal the nature of the mobility of an unknown linkage. Key features of the results are that polynomial continuation was able to provide complete sets of feasible options to a number of practical design problems, and also to reveal the nature of the mobility of a real overconstrained linkage.
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Ingham, Michel D. (Michel Donald) 1972. "Microdynamics and thermal snap response of deployable space structures." Thesis, Massachusetts Institute of Technology, 1998. http://hdl.handle.net/1721.1/50384.
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Chun, Katherine S. (Katherine Shisuka). "Shape memory alloy rotary actuator for CubeSat deployable structures." Thesis, Massachusetts Institute of Technology, 2020. https://hdl.handle.net/1721.1/127066.
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Thesis: S.M., Massachusetts Institute of Technology, Department of Aeronautics and Astronautics, May, 2020Cataloged from the official PDF of thesis.
Includes bibliographical references (pages 77-82).
Small satellites have lowered the barrier to entry for space-bound science and technology demonstrations. However, the small form factor requires extremely low size, weight, and power for any on-board hardware. Precision actuation of deployable structures has previously been achievable only through low SWaP single-use actuators or motor-driven, high SWaP multiple-use actuators. The Folded Lightweight Actuated Positioning System has the potential to provide an ultra-lightweight multiple-use actuator by using a Joule-heated shape memory alloy-based hinge. The hinge uses two shape memory alloy strips which are trained in opposite directions and mounted into a rotary actuator. Two different shape memory alloy geometries are explored: a rectangular cross-section and a circular cross-section. The rectangular hinge actuates over a range of ±20° with an average power of 0.14 W. The circular hinge actuates over a range of ±23° with an average power of 0.073 W. A closed-loop controller uses pulse width modulation and encoder measurements to actuate the rectangular hinge to within 2' of the desired angle.
by Katherine S. Chun.
S.M.
S.M. Massachusetts Institute of Technology, Department of Aeronautics and Astronautics
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Kuribayashi, Kaori. "A novel foldable stent graft." Thesis, University of Oxford, 2004. http://ora.ox.ac.uk/objects/uuid:a2a7d876-a1b5-4509-9ca5-0b8bd86da360.
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This dissertation concerns the structural design of medical stent grafts. A new type of an innovative stent graft has been developed. Unlike the conventional stent grafts which consist of a wire mesh and a covering membrane, the proposed stent graft can be made from a single folded sheet of material. Firstly, a detailed symmetric design of a foldable cylindrical tube for the new stent graft has been presented. Folding is achieved by dividing the structure into a series of identical elements with hill and valley folds as in origami (Japanese art of paper folding). The folding patterns allow the stent graft to be folded and expanded both radially and longitudinally. The relationships among the design of the elements, the number of elements in the circumferential and longitudinal directions and the folded dimensions of the stent graft have been derived. It has been found that compact folding in the radial direction can be achieved by increasing the number of circumferential elements. A geometric mismatch during deployment has also been identified. The elements have to deform when the structure is expanded. Optimum designs which minimise the deformation have been found. Secondly, a new stent graft with helical folds has also been designed to improve radial strength and ease the deployment process. Helical folds are introduced by adjusting the joining position of the two edges of a sheet that had been symmetrically jointed in the symmetric design. The relationships among the number of elements in one complete circumference of a helix, the helical angle and the radius of the helical type stent graft have been established. The locations for the helical folds are optimised for easy folding by considering both geometric aspects of folding and the buckling patterns of a thin-walled tube under torsion, which are found analytically. Thirdly, using numerical analysis of the finite element method (FEM) the strain level and overall deformation of the stent graft during deployment has been calculated. Finally, the stent graft has been manufactured to verify the concept. A number of prototypes of the stent graft, which are the same size as standard oesophageal and aortal stent grafts, have been produced successfully using the same materials as current stent grafts of stainless steel and shape memory alloy (SMA) sheets. The patterns of folds on the materials are produced by photochemical etching. It has also been demonstrated that the SMA stent grafts self-expand smoothly and gradually by a near body temperature.
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Lengyel, András. "Analogy between equilibrium of structures and compatibility of mechanisms." Thesis, University of Oxford, 2002. http://ora.ox.ac.uk/objects/uuid:457c87b2-5adb-45fc-9799-c2540950996f.
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Planar bar-and-joint mechanisms with one degree-of-freedom are widely used in deployable structures and machines. Such mechanisms are designed to undergo a specific motion, which can be described mathematically by plotting out the compatibility conditions, resulting in a curve called compatibility path. It has been observed that compatibility paths can develop singularities similar to that of equilibrium paths of elastic structures. This dissertation studies singularities occurring in compatibility paths with the aid of knowledge in the theory of structural stability. An analogy is set up between the equilibrium path of elastic structures and the compatibility path of mechanisms with a single degree-of-freedom incorporating the different types of bifurcation, effects of imperfections and detection of singularities. It is shown that the fundamentally distinct critical points such as limit points and bifurcation points can also appear in compatibility path. Methods used to singularities for compatibility conditions of mechanisms and equilibrium of structures are unified so that they can be used for both cases. A formulation of potential energy for mechanisms is also proposed in analogy with the potential energy function used in structural analysis. Further analysis of the mechanisms is carried out to demonstrate that singularities of compatibility paths can also be dealt with by the elementary catastrophe theory similar to the stability theory. A relationship is established between the mathematical formulation of different compatibility bifurcations and the canonical forms of catastrophe types. Examples of mechanisms demonstrating the existence of cuspoids of the compatibility conditions are given. An overall classification of the compatibility paths is also proposed.
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Fimbel, Amaury. "Origami à base de matériaux électroactifs pour des applications spatiales." Electronic Thesis or Diss., Lyon, INSA, 2023. http://www.theses.fr/2023ISAL0071.
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Ce projet de thèse s’inscrit dans le cadre d’une collaboration Cifre entre le LGEF et l’entreprise ArianeGroup. La fluctuation de forme de structures complexes à l'aide de polymères électroactifs est le sujet principal de cette étude. Les matériaux électroactifs, qui, de par leurs structures peuvent réaliser une conversion électromécanique de l’énergie, prouvent progressivement leur potentiel de percée technologique dans de nombreux domaines. En plus de l'hypothèse qu'ils pourraient éventuellement remplacer les capteurs et actionneurs actuellement utilisés, les nouvelles capacités de ces matériaux tant au niveau des performances que des capacités de couplage multiphysique sont une sérieuse source d’espoir pour aborder et résoudre des problèmes issus de secteurs émergents. Ces innovations technologiques potentielles peuvent affecter particulièrement le domaine de l'aérospatial. La combinaison d'une faible masse volumique et d'une densité d'énergie mécanique considérable pour un polymère semble apporter une réponse attrayante à la mise au point de dispositifs innovants, compacts et modulables. Mais certains points restent à explorer pour démontrer tout le potentiel applicatif de cette technologie et aboutir au développement de systèmes intelligents. Une grande partie de ce travail de recherche va donc se concentrer sur cette problématique. Ce projet se focalise ainsi sur l'élaboration et la caractérisation d'un composite à haute performance pour l'actionnement électrostatique et sa tenue en vieillissement en milieu spatial. Les objectifs de l'étude mécanique des structures origami sont de trouver des solutions concernant la compréhension et le développement de systèmes complexes et modulables. L’association de ces deux axes ouvre la voie à la création de structures mécaniques très légères pilotables par un champ électrique. Cette thèse concerne les applications spatiales mais peut tout à fait s’ancrer dans un enjeu sociétal plus large comme par exemple le médical, la robotique ou encore le domaine des transportsThis thesis project is part of a Cifre collaboration between the Electrical Engineering and Ferro Electricity Laboratory and ArianeGroup. The main subject of this study is the shape shifting of complex structures by using electroactive polymers. Electroactive materials, whose internal conformations are capable of electromechanical energy conversion, are gradually proving their potential for technological breakthroughs in many fields. In addition to the hypothesis that they could eventually replace actual sensors and actuators, the new capabilities of these materials in terms of both performance and multiphysics coupling capacities are a serious source of hope for tackling and solving problems in emerging fields. These potential technological innovations may be of particular interest for aerospace industry. Combination of low density and high mechanical energy density in a polymer seems to offer an attractive answer to the development of innovative, compact and modular devices. However, some parts remain to be explored in order to demonstrate the full application potential of this technology and lead to the development of smart systems. A large part of this research work will focus on this issue. This project will deal with the development and characterization of a high-performance composite for electrostatic actuation and its resistance to ageing in a space environment. The objectives of the mechanical study of origami structures are to find solutions for understanding and developing complex, modular systems. The combination of these two lines opens the way to the creation of very light mechanical structures that can be controlled by an electric field. This thesis concerns space applications, but can also be applied to a wider societal issue, such as medical, robotics or transport sectors
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Khatsenko, Maxim O. "A rotary shape memory alloy actuator for CubeSat deployable structures." Thesis, Massachusetts Institute of Technology, 2017. http://hdl.handle.net/1721.1/111751.
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Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2017.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 155-158).
Over a decade of continuing CubeSat technology improvements are driving the wide adoption of CubeSats for research and commercial missions. Resource constraints onboard CubeSats still limit their ability to support multi-use actuators, but there is a need for a rotary CubeSat actuator that can be actively commanded to different angles. This type of actuator can be implemented in a CubeSat mechanism for differential drag management, increased power generation, and reconfigurable deployable structures. We propose using a shape memory alloy (SMA) actuator to meet this need. A SMA can be annealed at high temperatures to remember a trained shape. Upon cool down, the SMA element transforms to the martensite phase and is easily deformed. When the element is heated above the transformation temperature it transforms to the stiff austenite phase and assumes its remembered shape, driving the mechanism. Two SMA actuators are trained to different shapes and provide bidirectional rotary motion for use as a space mechanism. The actuators are designed by implementing kinematic, thermal, and bending models to size the SMA element. The models also predict the performance, size, weight, and power of the actuator and ensure it can operate in the CubeSat environment. Then, a prototype of the proposed actuator is manufactured, assembled, and ground tested. Testing is used to validate the models and verify the requirements necessary to operate onboard a CubeSat. The prototype meets all requirements and offers a reduced mass, volume, and complexity alternative to current CubeSat electromagnetic actuators. Future work is necessary to improve the mechanical performance and positional control of the SMA actuator.
by Maxim O. Khatsenko.
S.M.
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Puthurloganathan, Karthigeyan. "Design of closed loop deployable structures for tents and masts." [Gainesville, Fla.] : University of Florida, 2004. http://purl.fcla.edu/fcla/etd/UFE0003540.
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York, Darren M. "Structural analyses of a joint for deployable space systems." Thesis, University of Surrey, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.332335.
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Shepenkov, Valeriy. "Vibration Modal Analysis of a Deployable Boom Integrated to a CubeSat." Thesis, KTH, Strukturmekanik, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-122076.
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CubeSat or Cubic Satellite is an effective method to study the space aroundthe Earth thanks to its low cost, easy maintenance and short lead time. However, a great challenge of small satellites lies in achieving technicaland scientific requirements during the design stage. In the present workprimary focus is given to dynamic characterization of the deployable tapespringboom in order to verify and study the boom deployment dynamiceffects on the satellite. The deployed boom dynamic characteristics werestudied through simulations and experimental testing. The gravity offloadingsystem was used to simulate weightlessness environment in theexperimental testing and simulations showed that the deployment of thesystem influence the results in a different way depending on the vibrationmode shape.En CubeSat eller kubisk satellit är effektivt för att studera rymden runtjorden på grund av dess låga kostnad, enkla underhåll och korta ledtid. Enstor utmaningen i utformningen av små satelliter är att uppnå de tekniskaoch vetenskapliga kraven. Detta arbete har analyserat de dynamiska egenskapernahos en utfällbar band-fjäder bom i syfte att verifera och för attstudera bommens utfällningsdynamiska effekter på satellitens bana och attityd.Den utfällda bommens dynamiska egenskaper har studerats genomsimuleringar och experimentella tester. Ett tyngdkraftskompenserande systemhar använts för att simulera tyngdlöshet i de experimentella testernaoch simuleringar visar att utformningen av detta system påverkar resultatenolika beroende på svängingsmodens form.
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Bettini, William. "Solutions innovantes pour des structures spatiales déployables." Thesis, Montpellier, 2018. http://www.theses.fr/2018MONTS038/document.
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Les structures destinées aux applications aérospatiales se doivent d’être légères, rigides et compactes afin de pouvoir être stockées dans la coiffe d’un lanceur. Une solution permettant de déployer automatiquement une ossature rigide à l’aide d’énergie élastique stockée dans des liaisons souples est proposée. La solution retenue, constituant une structure annulaire polygonale, peut être utilisée dans différents types d’applications spatiales, que ce soit pour des voiles solaires, de désorbitation ou des antennes satellite. Elle a fait l’objet d’études géométriques afin d’en optimiser la compacité et la masse. La cinématique et la dynamique du déploiement ont aussi été étudiées et modélisées, à la fois analytiquement et numériquement. L’analyse de la rigidité de la structure en position gerbée (pliée dans la coiffe du lanceur) et en configuration opérationnelle est traitée et confrontée aux expérimentations vibratoires d’un prototype. L’adjonction d’un réseau tridimensionnel permettant de tendre une membrane réflectrice pour des applications de type « antenne »sera proposée, ainsi qu’un dispositif de verrouillage en phase opérationnelleThe structures intended for the aerospace applications have to be lightweight, stiff and compact to be able to be stored in the fairing of a launcher. A solution is allowing to deploy automatically a stiff skeleton by means of elastic energy stored in flexible connections. The reserved solution, establishing an annular polygonal structure, can be used in various types of space applications, whether it is for solar, deorbiting or satellite antennas. It made the object of geometrical studies to optimize the compactness and the mass. The kinematics and the dynamics of the deployment were also studied and modelled, at the same time analytically and numerically. The analysis of the rigidity of the structure in folded position (folded in the fairing) and in operational configuration is handled and confronted with the vibratory experiments of a prototype. The addition of a three-dimensional network allowing to tighten a reflector membrane for applications of type "antenna" will be proposed, as well as a locking device in operational phase
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King, Simon Alexander. "Nonlinear and chaotic dynamics of thin-walled open-section deployable structures." Thesis, University of Cambridge, 1998. https://www.repository.cam.ac.uk/handle/1810/272155.
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Friedman, Noémi. "Investigation of highly flexible, deployable structures : review, modelling, control, experiments and application." Phd thesis, École normale supérieure de Cachan - ENS Cachan, 2011. http://tel.archives-ouvertes.fr/tel-00675481.
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In this thesis, an extensive review on different transformable systems used in architecture and civil engineering is given. After the review, structures undergoing large displacements and instability phenomenon were highlighted. The main goal of the dissertation was to investigate the general behavior of a specific, immature self-deploying system, the antiprismatic structure proposed by Hegedus. The emphasis was mainly taken to the analysis of the packing behavior. First, a simplified planar model was identified sharing similar, highly nonlinear packing behavior. For both the 2D and the 3D structures numerical simulation of the packing was performed with different type of controls and the results were confirmed by analytical investigations. The research clarifies the mechanical behavior of the chosen system, provides tools to simulate the packing of the structure, options for control, and gives very simple approximations for main mechanical characteristics of the antiprismatic system in order to facilitate preliminary design and verification of the numerical results. The significance of snap-back behavior, occurring at the force-displacement diagram during packing was analyzed. Within the framework of the thesis a novel type of system, slightly deviating from the original one was also investigated. For the specific systems, small physical models were built and presented in this work, which led to the proposal of a novel type of expandable tube. An attempt was given to provide ideas for application of antiprismatic structures by combining the investigated system and different learnt existing systems from the architectural review.
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Mallikarachchi, H. M. Yasitha Chinthaka. "Thin-walled composite deployable booms with tape-spring hinges." Thesis, University of Cambridge, 2011. https://www.repository.cam.ac.uk/handle/1810/239395.
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Deployable structures made from ultra-thin composite materials can be folded elastically and are able to self-deploy by releasing the stored strain energy. Their lightness, low cost due to smaller number of components, and friction insensitive behaviour are key attractions for space applications. This dissertation presents a design methodology for lightweight composite booms with multiple tape-spring hinges. The whole process of folding and deployment of the tape-spring hinges under both quasi-static and dynamic loading has been captured in detail through finite element simulations, starting from a micro-mechanical model of the laminate based on the measured geometry and elastic properties of the woven tows. A stress-resultant based six-dimensional failure criterion has been developed for checking if the structure would be damaged. A detailed study of the quasi-static folding and deployment of a tape-spring hinge made from a two-ply plain-weave laminate of carbon-fibre reinforced plastic has been carried out. A particular version of this hinge was constructed and its moment-rotation profile during quasi-static deployment was measured. Folding and deployment simulations of the tape-spring hinge were carried out with the commercial finite element package Abaqus/Explicit, starting from the as-built, unstrained structure. The folding simulation includes the effects of pinching the hinge in the middle to reduce the peak moment required to fold it. The deployment simulation fully captures both the steady-state moment part of the deployment and the final snap back to the deployed configuration. An alternative simulation without pinching the hinge provides an estimate of the maximum moment that could be carried by the hinge during operation. This moment is about double the snap-back moment for the particular hinge design that was considered. The dynamic deployment of a tape-spring hinge boom has been studied both experimentally and by means of detailed finite-element simulations. It has been shown that the deployment of the boom can be divided into three phases: deployment; latching, which may involve buckling of the tape springs and large rotations of the boom; and vibration of the boom in the latched configuration. The second phase is the most critical as the boom can fold backwards and hence interfere with other spacecraft components. A geometric optimisation study was carried out by parameterising the slot geometry in terms of slot length, width and end circle diameter. The stress-resultant based failure criterion was then used to analyse the safety of the structure. The optimisation study was focused on finding a hinge design that can be folded 180 degrees with the shortest possible slot length. Simulations have shown that the strains can be significantly reduced by allowing the end cross-sections to deform freely. Based on the simulations a failure-critical design and a failure-safe design were selected and experimentally verified. The failure-safe optimised design is six times stiffer in torsion, twice stiffer axially and stores two and a half times more strain energy than the previously considered design. Finally, an example of designing a 1 m long self-deployable boom that could be folded around a spacecraft has been presented. The safety of this two-hinge boom has been evaluated during both stowage and dynamic deployment. A safe design that latches without any overshoot was selected and validated by a dynamic deployment experiment.
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Pehrson, Nathan Alan. "Developing Origami-Based Approaches to Realize Novel Architectures and Behaviors for Deployable Space Arrays." BYU ScholarsArchive, 2019. https://scholarsarchive.byu.edu/etd/7762.
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Origami-based approaches for the folding of thick materials for specific application to large deployable space arrays is explored in this work. The folding approaches presented utilize strain energy, spatial kinematics, membranes, compliant mechanisms, and or in combination together to fold finite-thickness materials viewed through the lens of origami-based engineering. Novel architectures and behaviors of mechanisms are developed to achieve packaging efficiency, deployment, and self-stiffening. A method for the folding of monolithic thick-sheet materials is developed by incorporating compliant mechanisms into the material itself to strategically add degrees of freedom. The design and characterization of the compliant mechanisms with consideration to stress, material selection, and stiffness is given. Other folding approaches developed include a bistable vertex and a double-membrane method.The folding approaches derived are applied to larger tessellations and folding patterns. The fold patterns developed and used lend themselves well to large reconfiguration and the combination of the folding approaches with the patterns create opportunities to fabricate products out of thick, functional materials. Of specific interest is the application of these approaches and patterns to the field of deployable space arrays. Spatial kinematics, computational dynamics, physical tests, and systems engineering are used to develop an array architecture that is self-deployable, self-stiffening, and retractable. This architecture is shown to open the design space of large deployable arrays by increasing packaging efficiency and mass.The method, approaches, and architectures developed by this dissertation contribute to the fields origami-based engineering and deployable space arrays. While a focus of this work is the advancement of space technologies, the depth of the analyses provided are transferable to other origami-based and compliant-mechanism disciplines.
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Hopping, Jakob A. "Development of rapidly deployable structures for military applications : a system based approach to command post facilities." Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/36747.
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Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2006.Vita.
Includes bibliographical references (p. 91-94).
Today's battlespace is the most dynamic in recorded history. Accompanying other military improvements, Command and Control (C2) technology has also been modernized. In spite of advances in technology, it currently takes six times as long to deploy a Command Post (CP) as it did eight years ago. This decline in performance results in poor communication with forward units due to an increased distance between the units and the CP. This performance decline also increases the danger posed to command centers by enemy elements in the rear. Although each component of a modern CP functions well, CP structures are slow to deploy because many of the components of the command structure are developed separately to fulfill specific functions. Separately, these components are quick and innovative. Combined, they are cumbersome and labor intensive to assemble. The command structure must be viewed as a system that requires an encompassing solution. This thesis presents a rapidly deployable CP structure developed using a system based approach.
(cont.) The functional elements of a Command Post were analyzed and a comprehensive structure was designed to enhance the speed of CP establishment. Also, the appropriate background theory for structural and safety analysis was developed and applied to the resulting design. The proposed design, termed the Automated Command Post (ACP), is capable of establishing Command and Control in a mere fifteen minutes from start to finish; this is a 92% improvement over existing CP structures. In order to maximize the potential usefulness of the physical space within the ACP, the recommended ACP layout was constructed by modifying existing command post layouts using network theory. The ACP is an air-supported structure that requires a nominal pressure of only 0.036 psi to withstand up to 75 mph winds. Also, the ACP inflation system has an estimated fuel cost of only '/2 a gallon per day to maintain this pressure.
by Jakob A. Hopping.
S.B.
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Contreras, Mario Melendrez. "Design, analysis, and control of a nitinol shape memory alloy rotary actuator for spacecraft deployable structures." Thesis, Massachusetts Institute of Technology, 2019. https://hdl.handle.net/1721.1/123260.
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Thesis: S.B., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2019Cataloged from PDF version of thesis.
Includes bibliographical references (pages 34-35).
Small satellites known as CubeSats are becoming more and more popular in the aerospace industry and in academia. The new availability of rockets such as SpaceX's Falcon 9 or even dedicated CubeSat rockets such as Rocket Lab's Electron rocket have provided a new opportunity for many organizations to launch satellites. Depending on the goals of each satellite, they can be configured with many different payloads and mechanisms. Solar panels are one of the most common payloads on CubeSats but are mostly spring-actuated, meaning they cannot be deployed to precise angles. Shape memory alloys have been used to create rotary mechanisms in the past but closed loop control of shape memory alloys in a bending architecture is relatively novel. A rotary shape memory alloy actuator was designed with the use case of precisely pointing solar panels to maximize energy collection. Here we show identification of a system transfer function through multiple step responses and the use of a closed-loop PID control to achieve rise times of about 15 seconds with overshoot errors of 2 to 8 degrees. The experiments also showed the possibility of achieving rapid rise times of less than 2 seconds and accuracy within 2 degrees with some slight changes to the control system. This actuator prototype further develops the possibilities of precision angular actuation in a lightweight, robust, low volume, low power, and simple mechanical system.
by Mario Melendrez Contreras.
S.B.
S.B. Massachusetts Institute of Technology, Department of Mechanical Engineering
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Seereeram, Videsh Ramjas. "Compliant shell mechanisms." Thesis, University of Cambridge, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.610867.
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Morterolle, Sébastien. "Etude de structures légères déployables pour applications spatiales." Thesis, Montpellier 2, 2011. http://www.theses.fr/2011MON20155/document.
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Les besoins croissants en moyens de télécommunication nécessitent le développement de grands réflecteurs spatiaux paraboliques. Un nouveau concept d'architecture d'antenne déployable est ainsi proposé en partenariat avec le CNES. La conception de son ossature repose sur une revue de solutions pour faire appel à des mécanismes de ciseau associés à des articulations flexibles. Des modélisations numériques par éléments finis sont d'abord développées pour simuler le déploiement par restitution de l'énergie emmagasinée dans ces articulations lors du pliage. Un démonstrateur expérimental avec un système de compensation gravitaire est ensuite réalisé. Des essais et mesures sont effectués pour caractériser son comportement en statique et dynamique puis sont comparés avec les résultats issus des simulations. La mise en forme de la surface réflectrice par un réseau de câbles est étudiée par la suite. Une méthode innovante de recherche de forme permettant d'obtenir un réseau parabolique en tension uniforme est alors proposée. Elle est appliquée à différentes typologies de réseaux et l'erreur de surface résultant de sa facettisation est évaluée. Le procédé d'accrochage de ce réseau sur l'ossature de l'antenne est également traitéThe growing needs in telecommunications require the development of large parabolic reflectors. A new conceptual design for the architecture of a deployable antenna is therefore proposed in partnership with the CNES. The design of its framework is based on a review of solutions which leads to scissor mechanisms associated with flexible joints. Numerical modelings with finite elements are first developed to simulate the deployment by the release of the energy stored in the joints after the folding. An experimental prototype with a gravity compensation device is then realized. Tests and measurements are performed to characterize the static and dynamic behavior and compared with the results of simulations. Shaping of the reflective surface by a net of cables is then studied. A new form-finding method for obtaining a net with a uniform tension is then proposed. It is applied to different parabolic typologies of nets and the error due to surface faceting is evaluated. The process of net attachment on the antenna rim structure is also treated
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Mohammed, Tesfaye A. "Reinforced Concrete Structural Members Under Impact Loading." University of Toledo / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1321650443.
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