Дисертації: "Mechanical actuators"

1

Madden, John David Wyndham 1968. "Conducting polymer actuators." Thesis, Massachusetts Institute of Technology, 2000. http://hdl.handle.net/1721.1/8820.

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Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2000.
Includes bibliographical references.
Conducting polymers are unusual organic materials featuring high electronic conductivity. Recently it has been observed that some of these polymers change in dimension when their oxidation state is altered. Dimensional changes induced by electrochemical activation in the conducting polymer polypyrrole are investigated. Swept sine and step voltage and current inputs are employed to investigate the nature of this electro-mechanical coupling. Strains of up to 6 %, strain rates of 4 %/s, power to mass ratios of 40 W/kg and forces of up to 34 MN/m2 are achieved. Polypyrrole nearly equals mammalian skeletal muscle in power to mass and exceeds it in force by two orders of magnitude. A model is developed which predicts the electrochemical impedance, and relates electrical input to mechanical output. Observations and modeling indicate that diffusion and capacitive charging limit strain rate. The use of thinner films is predicted to increase strain rate and power to mass ratios by at least two orders of magnitude. Initial applications are likely to be in microelectromechanical systems.
by John David Wyndham Madden.
Ph.D.

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2

Broström, Carl. "Development of Tactile Actuators : Actuators for arm mounted hearing device." Thesis, Karlstads universitet, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-79063.

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This report is a thesis work for a Master of Science in Mechanical Engineering at Karlstad University. More than 8.5 million people in the world are deaf but unable to get cochlear implants. It has been shown that by the use of actuators that stimulate the skin nerves in different patterns, people can learn to feel the sound on their skin. Invencon AB has developed a actuator concept that uses an electromagnetic actuator with a moving permanent magnet. The problem with this concept is that it locks itself in its upper position due to the permanent magnets around it. The aim of this project was to develop a new actuator concept without the problem of locking-up by starting from the beginning through a systematic product development process. Through research of actuator technology, dividing the project into phases and tasks used in the industry and methods presented in literature such as systematic and creative concept generation, a product development project was made on a product with the main function of imprinting the skin in recognizable patterns. It resulted in an actuator concept similar but different to the existing concept. The resulting concept solved the problem presented by utilizing a moving coil instead of a moving permanent magnet. A 3D model was made and a prototype was 3D printed and tested. Future work includes designing a suitable spring, a research on how wire management should be done, how to minimize the environmental impact from transport, if there are any hazardous substances during elimination and if the income from recycled material can be greater than the elimination cost.
Denna rapport är ett examensarbete för civilingenjörsexamen i maskinteknik vid Karlstads universitet. Mer än 8,5 miljoner människor i världen är döva men är olämpliga för cochleaimplantat. Det har visats att användningen av aktuatorer som stimulerar hudnerverna i olika mönster kan lära människor att känna och lära sig ljudet på huden. Invencon AB har utvecklat ett aktuator koncept som använder sig utav en elektromagnetiskt aktuator med en rörlig permanent magnet. Problemet med detta koncept är att det låser sig i sitt övre läge på grund av de omringande permanenta magneternas påverkan. Syftet med detta projekt var att utveckla ett nytt aktuatorkoncept som inte fastnar i sitt övre läge genom att tillämpa systematisk produktutvecklings-process. Genom undersökandet av nuvarande aktuator teknologi, uppdelning av projektet i faser och uppgifter som används i branschen och metoder som presenteras i litteratur, såsom systematisk och kreativ konceptgenerering, gjordes ett produktutvecklingsprojekt på en produkt med huvudfunktionen att trycka på huden i igenkännbara mönster. Det resulterade i ett aktuatorkoncept som liknar men skiljer sig från det befintliga konceptet. Det resulterande konceptet löste problemet som presenterades genom att använda en rörlig spole i stället för en rörlig permanent magnet. En 3D-modell och sedan en prototyp framställdes och testades. Framtida arbete inkluderar utformningen av en lämplig fjäder, en undersökning om hur koppartråden bör hanteras, hur man minimerar miljöpåverkan från transport på produkten, undersöka om det finns några farliga ämnen under elimineringen av produkten och om intäkterna från återvunnet material kan vara större än elimineringskostnaden.

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3

Ismail, Ziad M. A. "Microprocessor control of electro-mechanical actuators." Thesis, Loughborough University, 1986. https://dspace.lboro.ac.uk/2134/11785.

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This thesis is concerned with the use of all-electric systems for the closed loop position control of mechanical (valve) actuators. It embraces a wide range of topics including * the use of 3-phase induction motors and their speed/torque control using Pulse Width Modulation techniques * implementation of both analogue and digital (PID) controllers * Using computer simulation methods for the development of digital control algorithms and tuning techniques * the use of Computer Assisted Tuning methods for tuning up the position control loop. The major hardware activities described here are concerned with the design, development and construction of a 3-phase 115 volt inverter unit, an analogue controller, and interfaces to a single board microcomputer (SBC). The construction and test of the SBC is also described in the text. Details of the use of an analog controller to study and determine the transfer function of the inverter/actuator system is presented. Digital implementation of PID control (for actuator's position) by microcomputer is also described, together with the theoretical development of the control algorithm. Software activities consist of two major parts, plant simulation and software development for the microprocessor (embedded) controller. The derivation of a plant model from the results of on-line testing is given; from this a computer simulation is developed to study the effects of controller tuning parameters on the loop performance. Software development for the embedded controller covers Man-Machine Interfacing, tuning, and control functions. A new approach to the tuning of control systems is developed here, that of computer assisted tuning. Test results are given showing the effectiveness of CAT techniques for the tuning of the actuator position control loop; these tests also demonstrate the performance achieved using a digital PID controller. It is concluded that, provided plant parameters can be established, Computer Aided Tuning enables plant tuning to be carried out to meet specific performance targets (e.g. rise time, overshoot) set by the plant operator. Furthermore this can be carried out by a relatively unskilled operator.

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4

Torras, Andrés Núria. "Smart Opto-mechanical actuators for tactile applications." Doctoral thesis, Universitat Autònoma de Barcelona, 2014. http://hdl.handle.net/10803/363930.

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La discapacitat visual és una greu amenaça que limita la capacitat de les persones per comunicar-se. Amb els anys, s’han explorat diverses propostes tecnològiques basades tan en estímuls auditius com tàctils per aportar solucions reals a la gent que pateix aquest tipus de discapacitat. Entre les més rellevants destaquen les tècniques d’audiodescripció i els dispositius Braille basats en actuació piezoelèctrica, que són els que actualment es troben al mercat. A dia d’avui, al vell mig de la cursa tecnològica, hi ha una demanda creixent de comunicació rica i fluida mitjançant el tacte. Tan és així que la majoria interruptors, botons i tecles de gran part dels dispositius electrònics del nostre entorn estan essent substituïts per pantalles tàctils, afegint barreres físiques i augmentant les dificultats de comunicació de les persones cegues. Noves generacions de materials, principalment els polímers, han despertat un gran interès en els darrers anys gràcies a les seves atractives propietats, que poden adaptar-se a la carta en funció de les necessitats. De tots ells, els elastòmers de cristalls líquids, LCE, en són un clar exemple. Els LCE tenen la capacitat intrínseca d’auto-organitzar-se a nivell molecular, desencadenant canvis controlats i totalment reversibles en les seves dimensions a escala macroscòpica, en resposta a diversos tipus d’estímuls externs; canvis que poden adaptar-se per desenvolupar actuadors capaços de produir tan esforços mecànics de tracció com d’empenta. La recerca presentada en aquesta tesi descriu les principals característiques dels LCE des del punt de vista de l’enginyeria i discuteix les seves possibles aplicacions com a actuadors, amb el principal objectiu d’aportar solucions innovadores als actuals sistemes tàctils, a partir del disseny, fabricació i caracterització de diferents actuadors basats en aquests materials i la seva foto-actuació a partir de llum visible. Propostes que combinen tècniques de processament de materials i tecnologia de microsistemes per aportar solucions tecnològiques innovadores cap a una nova generació d’actuadors intel·ligents.
La discapacidad visual es una grave amenaza que limita la capacidad de las personas para comunicarse. Con los años. Se han explorado diversas propuestas tecnológicas basadas tanto en estímulos auditivas como en estímulos táctiles para aportar soluciones reales al colectivo que sufre este tipo de discapacidad. Entre las más relevantes destacan las técnicas de audio descripción y los dispositivos Braille basados en actuación piezoeléctrica, que son los que actualmente se encuentran en el mercado. A día de hoy, en medio de la carrera tecnológica, hay una demanda creciente de comunicación rica y fluida a través del tacto. Tanto es así que la mayoría de los interruptores, botones y teclas de gran parte de los dispositivos electrónicos a nuestro alcance están siendo reemplazados por pantallas táctiles, añadiendo barreras físicas y aumentando las dificultades de comunicación de las personas ciegas. Nuevas generaciones de materiales, principalmente los polímeros, han despertado un gran interés en los últimos años gracias a sus atractivas propiedades, que pueden adaptarse a la carta en función de las necesidades. De todos ellos, los elastómeros de cristales líquidos, LCE, son un claro ejemplo. Los LCE tienen la capacidad intrínseca de auto-organizarse a nivel molecular, produciendo cambios controlados y totalmente reversibles de sus dimensiones a escala macroscópica, en respuesta a varios tipos de estímulos externos; cambios que pueden adaptarse a demanda para desarrollar actuadores capaces de producir distintos tipos de esfuerzos mecánicos de tracción. La investigación recogida y presentada en este documento de tesis describe las principales características de los LCE desde el punto de vista de la ingeniería y discute sus posibles aplicaciones cómo actuadores, con el principal objetivo de aportar soluciones innovadoras a los actuales sistemas táctiles, a partir del diseño, fabricación y caracterización de distintos actuadores basados en estos materiales y su foto-actuación a partir de luz visible. Propuestas que combinan técnicas de procesado de materiales y tecnología de microsistemas para aportar soluciones tecnológicas innovadoras hacia una nueva generación de actuadores inteligentes.
Visual disability is a serious threat that limits the persons’ ability to communicate. Over the years several attempts for the development of technologies based on audio and tactile stimuli have been explored to provide real solutions to individuals with this disability. Among them, audio description techniques and Braille devices based on piezoelectric actuation are the most relevant solutions on the market. Nowadays, with all the technological improvements, there is a growing demand for rich communication through touch. Thus switches, buttons and keyboards of most commonly used electrical devices are being replaced by tactile displays, adding new physical barriers and increasing communications difficulties of blind people. New generation of materials, especially soft polymer composites, have been of increased interest in the last few years due to their many attractive properties, which can be tailored on demand to achieve a broad range of requirements. Liquid-crystalline elastomers, LCE, are a clear example. Such materials possess the intrinsic ability to self-organize at molecular level resulting in a controllable and fully reversible change on their dimensions at macroscale in response to applied external stimuli, which can be easily adapted to make actuators producing pulling or pushing forces. The research presented in this thesis describes the main characteristics of LCE materials from engineering point of view and discusses their potential applications as actuators with the main objective to provide innovative solutions towards current tactile available systems, through the design, fabrication and characterization of different actuator approaches based on these interesting elastomeric materials and their photo-induced actuation using visible light. Novel approaches combining material processing techniques and microsystems technology to provide original solutions towards a new generation of smart actuators.

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5

Güler, Kenan, and Milan Andelkovic. "Shock Load Absorption of Electro-mechanical Actuators." Thesis, KTH, Skolan för industriell teknik och management (ITM), 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-300158.

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När ett ställdon får som krav att kunna överföra höga krafter i relativt höga hastigheter med en dessutom väldigt hög precision är elektromekaniska ställdon oftast att föredra. En traditionell pinjong-kuggstång-uppställning uppfyller vissa av de kraven, men om kraften ska ökas behövs det fler än ett pinjongpar. Begränsningar på tillverkningsprecisionen för dessa kugghjul gör att deras ansättning på kuggstången blir omöjlig för uppsättningar med fyra eller åtta pinjongpar eftersom ett sådant ställdon blir statiskt överbestämt och på grund av tillverkningstoleranser kan det bli svårt att erhålla jämn lastfördelning mellan pinjongerna. Därför utvecklade företaget Cascade Drives innovativa kugghjul (cdGear) med s.k. Flex Units som har en självinställningsfunktion i själva kugghjulen vilken tillgodogör för tillverkningstoleranser och spelet som ska undvikas. Flex Units består av bl.a. av gummielement som förutom att tillåta enstaka pinjongers rotation för inställning även har en mycket bra dämpningsförmåga, särskilt vad det gäller plötsliga stötlaster. Stötbelastningar förekommer ofta vid drift av arbetsmaskiner där Cascade Drives-ställdonet har hittat sin största användning. Plötsliga och höga stötbelastningar, som t.ex. när en grävmaskin kör in i ett gupp eller en snöröjare kör på en kantsten kan påverka maskinkomponenternas livslängd betydligt. Ett eventuellt maskinhaveri riskerar skador på både fordonet, föraren och omgivningen. Rapporten redogör för hur en teoretisk modell byggdes upp för att matematiskt beskriva dessa stötbelastningar och metoder som användes i datorprogrammet MATLAB för att beskriva det dynamiska förloppet i ställdonet under stötbelastningens inverkan. Ytterligare redogörs avgränsningar som görs på modellen och tills slut ges förslag på möjliga förbättringar för vidare arbete med modellen. Projektets syfte är inte att utvärdera hela Cascade Drives-ställdonet utan endast skapa en modell som kan tillämpas på alla möjliga scenarion av stötmoment. Rapporten innehåller några exempel på stötbelastningar och redogör för hur de påverkar olika kugghjul som ingår i ställdonet och hur det påverkar maskinen i sin helhet. För de scenarion som MATLAB-koden testades för noteras en mycket god dämpningsförmåga även vid förhållandevis höga laster (flera ton av last). Detta tack vore de patenterade flexenheterna och gummikutsarna, som kan dimensioneras och väljas för material beroende på tillämpningsområde och det tillåtna monteringsutrymmet i ställdonet. Denna modell baseras på dimensioner och materialdata tillförda av uppdragsgivaren för det aktuella ställdonet. Mer noggranna värden och en bättre kännedom om tillämpningsområdet skulle ge möjligheter för omdimensionering av flexenheterna och en mer optimal dämpnings- och momentöverföringsfunktion i ställdonet.
When requirements for an actuator include big momentum, fast transfer of the forces with a very high positioning precision, electro-mechanical actuators are often the constructor's first choice. A traditional rack-pinion setup answers to some of the requirements, but if the goal is to increase the forces which the rack undergoes, more than one pair of pinions is necessary. Production limitations, inevitable tolerances and gaps as a result make it almost impossible to have setups of four or eight pinion-pairs on one single rack because a such actuator would be statically overdetermined and out of manufacturing costs it can be difficult to procure equal load distribution between the pinions. Overcoming this challenge helped the company called Cascade Drives based in Stockholm, Sweden, to patent a new type of gear they call cdGear. CdGear give pinion the ability to position itself to the rack automatically, due to the rubber parts inside the gear that also work as shock load-absorbers for the whole actuator. Shock loads are very frequent in the type of work where these actuators found their biggest application. Heavy-duty machines are often exposed to sudden and high loads on their moving parts, i.e. when an excavator drives over a bump or a snow-plowing machine drives into a curbstone. The sudden impact on the working parts will cause a greater stress on the equipment, shorten its lifespan and a machine part's failure can even cause serious damage on workers, machine, and the environment. This thesis describes a theoretical model created for the purpose of calculating the effects of shock loads on the actuator based on the mathematical description of gear behaviour during the impact. It also includes the methods used to create a model in MATLAB that simulates the dynamical forces, model's limitations, and suggestions on how to improve its accuracy. This project does not aim to improve the overall performance of the Cascade Drives-actuator, but rather deliver a sufficient virtual model that works for the most shock load scenarios, that in the end will give the commissioner useful data and clues on how to improve their product. The thesis does include a few different shock load scenarios that prove the code's functionality and give answers to how some shock loads affect gears inside the actuator and performance of the machine itself. For the virtual tests done Cascade Drives-actuator performs very good in damping the shock loads, even when the loads reach a corresponding force of a few tons. CdGear and elasticity inside its rubber parts are the main reason why the actuator performs so well, and the rubber parts inside the gear can be changed in respect to the application and the mounting space allowed. The model described in the report includes dimensions and material's data provided by the commissioner for the actuator in question. More exact and relevant results can be acquired if the input values are more precise, and the area of usage is described in more detail. More optimal rubber parts inside the CdGear would result in a better performing actuator that besides being able to transfer huge torque also could absorb the inevitable shock loads in a very satisfactory manner.

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6

Morrell, John Bryant. "Parallel Coupled Micro-Macro Actuators." Thesis, Massachusetts Institute of Technology, 1996. http://hdl.handle.net/1721.1/7066.

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This thesis presents a new actuator system consisting of a micro-actuator and a macro-actuator coupled in parallel via a compliant transmission. The system is called the Parallel Coupled Micro-Macro Actuator, or PaCMMA. In this system, the micro-actuator is capable of high bandwidth force control due to its low mass and direct-drive connection to the output shaft. The compliant transmission of the macro-actuator reduces the impedance (stiffness) at the output shaft and increases the dynamic range of force. Performance improvement over single actuator systems was expected in force control, impedance control, force distortion and reduction of transient impact forces. A set of quantitative measures is proposed and the actuator system is evaluated against them: Force Control Bandwidth, Position Bandwidth, Dynamic Range, Impact Force, Impedance ("Backdriveability'"), Force Distortion and Force Performance Space. Several theoretical performance limits are derived from the saturation limits of the system. A control law is proposed and control system performance is compared to the theoretical limits. A prototype testbed was built using permanenent magnet motors and an experimental comparison was performed between this actuator concept and two single actuator systems. The following performance was observed: Force bandwidth of 56Hz, Torque Dynamic Range of 800:1, Peak Torque of 1040mNm, Minimum Torque of 1.3mNm. Peak Impact Force was reduced by an order of magnitude. Distortion at small amplitudes was reduced substantially. Backdriven impedance was reduced by 2-3 orders of magnitude. This actuator system shows promise for manipulator design as well as psychophysical tests of human performance.

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7

Del, Zio Michael R. (Michael Robert) 1982. "Conducting polymer actuators : temperature effects." Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/35656.

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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2006.
Includes bibliographical references.
In order to utilize conducting polymer actuators as a viable engineering solution, it is necessary to produce usable levels of force with a reasonable bandwidth. Polypyrrole actuated at temperatures as high as 100 °C increases stress magnitudes by as much as 4x and stress rates by 5x. The effect is caused by a combination of decreased solution resistance and increased ion diffusion within the polymer. However, these temperatures cause accelerated degradation due to the time-temperature correlation common to viscoelastic polymers. Actuation at these temperatures can decrease cycle life by as much as 20x. Excessive heating without actuation can also result in poor actuator performance. Impedance spectroscopy coupled with electro-mechanical analysis highlighted previous results and also showed an improved frequency response from actuation at high temperatures.
by Michael R. Del Zio.
S.M.

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8

Chen, Angela Y. (Angela Ying-Ju) 1982. "Large displacement fast conducting polymer actuators." Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/35659.

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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2006.
Includes bibliographical references (leaves 93-96).
Conducting polymers are a promising class of electroactive materials that undergo volumetric changes under applied potentials, which make them particularly useful for many actuation applications. Polypyrrole , is one of the most common conducting polymers of choice for the development of actuator technologies and has been well characterized in its mechanical, electrical, and electrochemical response. Although capable of producing almost 10 times more active stress for a given cross-sectional area than skeletal muscle, strains are relatively low on the order of 1 to 2 %, as are strain rates, which are on the order of a couple percent per second. Small strains can be amplified to produce large bending displacements by configuring the conducting polymer film in a trilayer configuration with two conducting polymer films sandwiching an electrolyte gel layer. This thesis focuses on the development of conducting polymer bending actuators in air. There is a strong correlation found between applied voltage, temperature, and the speed of actuation. Several experiments were carried out to determine the effect of temperature on the mechanical, electrical, and electrochemical properties of the components of the trilayer.
(cont.) This data coupled with thermal profiles of trilayers during actuation, electrochemical profiles, and force generation plots of the trilayers shed light on how these bending actuators can be optimized and integrated into different applications such as propulsion mechanisms for autonomous underwater vehicles.
by Angela Ying Ju Chen.
S.M.

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9

Anquetil, Patrick A. T. (Patrick Armand T. ). 1973. "Large contraction conducting polymer molecular actuators." Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/30349.

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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, February 2005.
Vita. Leaf 239 blank.
Includes bibliographical references.
The development of powerful and efficient artificial muscles that mimic Nature will profoundly affect engineering sciences including robotics and prosthetics, propulsion systems, and microelectromechanical systems (MEMS). Biological systems driven by muscle out-perform human-engineered systems in many key aspects. For example, muscle endows animals with a level of dexterity and speed that has yet to be emulated by even the most complex robotic system to date. Conducting polymers were chosen for research as actuators, based on a review of the relevant properties of all known actuators and active materials. Key features of conducting polymer actuators include low drive voltages (1 - 2 V) and high active strength (10 - 40 MPa) but moderate active strains (2 %). Active strains of 20 %, which human skeletal muscle is capable of, are desirable for applications in life-like robotics, artificial prostheses or medical devices. This thesis focuses on two approaches to create large contraction in conducting polymer actuators. The first strategy utilizes polypyrrole (PPy), a conducting polymer actuator material that contracts and expands based on a bulk ion swelling mechanism. Optimization of the polymer activation environment via room temperature ionic liquids enables PPy actuators to generate large contractions (16.3 % recoverable strain at 2.5 MPa, 21 % max) at slow speeds (0.4 %/s). In addition, cycle life can reach 10⁵ cycles without significant polymer degradation. This thesis presents an in-depth characterization of the behavior of polypyrrole actuators in room temperature 1-butyl-3-methyl imidazolium tetrafluoroborate liquid salt electrolyte.
(cont.) The characterization includes the assessment of passive and electroactive mechanical properties as well as electrical and morphological properties. Using Nature's actin-myosin molecular engine as a source of inspiration, the second approach uses molecular mechanisms to create motion. In this bottom-up approach molecules are rationally designed from the molecular level for specific actuation properties. Such active molecular building blocks include shape changing, load bearing, passively deformable or hinge-like molecular elements. Several novel materials based on contractile molecular design were synthesized and their active properties characterized.
by Patrick A.T. Anquetil.
Ph.D.

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10

Yang, Dian. "Soft Pneumatic Actuators Using Negative Pressure." Thesis, Harvard University, 2016. http://nrs.harvard.edu/urn-3:HUL.InstRepos:33493304.

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Soft robotics is a growing field where scientists and engineers collaborate to design machines that collaborate safely with humans (namely “collaborative robot”), and manipulate soft or delicate objects safely. Soft pneumatic actuators are excellent tools in building soft robots, since both the elastomer used in building the actuators and the air used to power them are naturally compliant. This compliance distributes the contact force over the area of contact, and limits the contact pressure. Soft pneumatic actuators changes shape with pressure, and use strain-limiting components imbedded in an elastomeric enclosure to generate various motions. This dissertation explores design and fabrication of soft pneumatic actuators by combining vacuum with reversible buckling of elastomeric beams. Buckling is a classical mechanical instability often seen as a failure mode in hard materials. The reversible buckling of elastomeric beams, however, allows buckling to be harnessed as a method to generate a range of motion, and allows the fabrication of actuators that mimic the performance of actuators (i.e. muscles) found in nature. Chapter 1 provides a short overview of the history of soft pneumatic actuators, and of the use of vacuum instead of pressure as a source of power. Chapter 2 and Appendix I describe rotary soft pneumatic actuators—the buckling actuator—based on vacuum and buckling of elastomeric beams. Chapter 3 and Appendix II describe the design of linear soft pneumatic actuators—vacuum-actuated muscle-inspired pneumatic structures (VAMPs)—based on the same technology, which mimics the mechanical performance and many useful features of human muscle. Chapter 4 and Appendix III describe a design of vacuum-actuated soft linear actuators (VASAs) that overcome the usual limit of one atmosphere in the output pressure by generating a mechanical advantage. Appendix IV demonstrates that the buckling of arrays of elastomeric beams can also be used in building soft metamaterials with useful functions, such as shape memory metamaterials. Beyond soft pneumatics actuators, novel methods of non-damaging manipulations, such as magnetic levitation, can prove useful in orientation and examination of objects (Appendix V, VI).
Engineering and Applied Sciences - Engineering Sciences

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11

Pillai, Priam Vasudevan. "Development and characterization of conducting polymer actuators." Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/67594.

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Анотація:

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2011.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 115-127).
Conducting polymers such as polypyrrole, polythiophene and polyaniline are currently studied as novel biologically inspired actuators. The actuation mechanism of these materials depends upon the motion of ions in and out of the polymer film during electrochemical cycling. The diffusion of ions into the bulk of the film causes the dynamic mechanical and electrical properties of the material to change during oxidation and reduction. The mechanism of this change is not fully understood, as it can depend on many different factors such as oxidation state, solvation of the film and the level of counter ion swelling. In-situ measurement of the dynamic mechanical compliance and electrical impedance of polypyrrole as a function of charge is difficult, since the compliance depends upon the excitation frequency as well as the electrochemical stimulus. Here, we have developed novel experimental techniques that use stochastic input waveforms to dynamically measure the compliance and impedance response of conducting polymers as a function of frequency and an electrochemical stimulus. A stochastic stress input signal with a bandwidth of 30 Hz is used, which allows us to compute the mechanical compliance transfer function of polypyrrole as function of the electrochemistry. The low frequency compliance changes between 50-80%, as charge is injected into polypyrrole in neat 1-butyl-3-methylimidazolium hexafluorophosphate. The compliance changes reversibly as ions diffuse in and out of the film, which indicates that the compliance depends upon the level of counter ion swelling. The effect of cationic and anionic charging on the polypyrrole compliance is demonstrated in multiple ionic/solvent combinations. The stochastic signals are also used to the characterize the isometric and isotonic responses of conducting polymer actuators. This technique is used to demonstrate the effect of temperature and solution conductivity on actuation and to develop methods that can be used to improve polymer actuator performance. Efficient techniques to incorporate functionalized carbon nanotubes into conducting polymers using layer by layer deposition and drop casting methods have been explored. These new composite materials and techniques significantly reduce creep, improve conductivity and increase stiffness of the polymer actuators.
by Priam Vasudevan Pillai.
Ph.D.

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12

Heyer, John Henry 1973. "Design of silent, miniature, high torque actuators." Thesis, Massachusetts Institute of Technology, 1999. http://hdl.handle.net/1721.1/80629.

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13

Liu, Wenda. "EFFICIENT THERMAL ACTUATORS FOR MICROMECHANICAL DEVICES." Case Western Reserve University School of Graduate Studies / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=case1570545554943714.

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14

Bissal, Ara. "On the Design of Ultra-fast Electro-Mechanical Actuators." Licentiate thesis, KTH, Elektroteknisk teori och konstruktion, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-121181.

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The continuously increasing demand for connecting electric grids with remote renewable energy sources such as wind power and photovoltaic cells has rekindled interest in high voltage direct current (HVDC) multi-terminal networks. Although HVDC networks have numerous benefits, their adoption relies entirely on the availability of HVDC circuit breakers which, compared to traditional alternating current circuit breakers, have to operate in a time frame of milliseconds. This thesis deals with the design of ultra-fast electro-mechanical actuators based on the so-called Thomson coil (TC) actuator. The simulation of a (TC) actuator constitutes a multi-physical problem where electromagnetic, thermal, and mechanical aspects must be considered. Moreover, it is complex since all those variables are co-dependent and have to be solved for simultaneously. As a result, a multi-physics simulation model that can predict the behavior and performance of such actuators with a high degree of accuracy was developed. Furthermore, other actuator concepts were also investigated and modeled in light of searching for a drive with a superior efficiency. The theory behind the force generation principles of two different types of ultra-fast electromechanical actuators, the TC and the double sided coil (DSC), were compared by the use of static, frequency, and comprehensive transient multi-physics finite element simulation models. Although, simulation models serve as a powerful tool for modeling and designing such state of the art actuators, without validation, they are weak and prone to errors since they rely on approximations and simplifications that might not always hold. Therefore, a prototype was built in the laboratory and the model was validated experimentally. Finally, it is important to note that the drives in this thesis are intended to actuate metallic contacts. As such, their behavior and performance upon mechanical loading was studied. Furthermore, some scaling techniques were applied to boost their performance and efficiency.

QC 20130422

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15

Ghaeadi, Sirous K. "Control of vibrations of shells using piezoelectric actuators." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0018/NQ55333.pdf.

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16

Zhong, Jinghua. "Modeling and Control of Piezoceramic Actuators for Nanopositioning." NCSU, 2003. http://www.lib.ncsu.edu/theses/available/etd-08182003-201924/.

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Actuators from piezoceramic materials have established themselves in a large number of applications, especially nano-scale positioning tasks because of their high-frequency response behavior and their essentially infinite resolution. However, the potential of these actuators has been impaired by the lack of adequate hysteresis models and control methods to compensate the undesirable non-linear, hysteretic and rate-dependent behavior of piezoceramic materials. In this thesis, representative actuation experiments are conducted on a typical commercially available piezoceramic stack actuator to characterize the rate-dependence of its hysteretic behavior over a large stroke under different loading rates. A strongly physics oriented energy model is implemented to verify its ability in modeling dynamic hysteretic behaviors. By extending this model, a computationally efficient implementation is developed with a drastic improvement in speed. Finally, a preliminary version of the energy model for the piezoceramic material is implemented in an optimal control program to illustrate the features and potential of the method. The implementations constitute the basis for future development of advanced realtime control algorithms for piezoceramic actuators.

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17

Plante, Jean-Sébastien Ph D. Massachusetts Institute of Technology. "Dielectric elastomer actuators for binary robotics and mechatronics." Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/35305.

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Анотація:

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2006.
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
"February 2006."
Includes bibliographical references (p. 145-153).
Future robotics and mechatronics applications will require systems that are simple, robust, lightweight and inexpensive. A suggested solution for future systems is binary actuation. Binary actuation is the mechanical analogy to digital electronics, where actuators "flip" between two discrete states. Systems can be simple since low-level feedback control, sensors, wiring and electronics are virtually eliminated. However, conventional actuators, such as DC motors and gearbox are not appropriate for binary robotics because they are complex, heavy, and expensive. This thesis proposes a new actuation technology for binary robotics and mechatronics based on dielectric elastomer (DE) technology. DE actuators are a novel class of polymer actuators that have shown promising low-cost performance. These actuators were not well understood and, as a result, faced major reliability problems. Fundamental studies conducted in this thesis reveal that reliable, high performance DE actuation based on highly viscoelastic polymers can be obtained at high deformation rates, when used under fast, intermittent motion.
(cont.) Also, analytical models revealed that viscoelasticity and current leakage through the film govern performance. These results are verified by an in-depth experimental characterizion of DE actuation. A new DE actuator concept using multi-layered diamond-shaped films is proposed. Essential design tools such as reliability/performance trade-offs maps, scaling laws, and design optimization metrics are proposed. A unit binary module is created by combining DE actuators with bistable structures to provide intermittent motion in applications requiring long-duration stateholding. An application example of binary robots for medical interventions inside Magnetic Resonance Imaging (MRI) systems illustrates the technology's potential.
by Jean-Sébastien Plante.
Ph.D.

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18

Ho, Wei Hsuan (Wei Hsuan Jessie). "Design, fabrication and characterization of polypyrrole trilayer actuators." Thesis, Massachusetts Institute of Technology, 2008. http://hdl.handle.net/1721.1/45850.

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Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2008.
Includes bibliographical references (leaf 48).
Conducting polymers are currently studied as artificial muscle materials. They are used instead of traditional actuators because they mimic the movements of animal muscles. They can generate larger active stresses than real muscles as well as generate small strains which can be amplified to cause larger motions. Traditionally, conductive polymers are immersed in liquid electrolytes. Utilizing a trilayer configuration by sandwiching the ions between two strips of polypyrrole films can be actuated in air. This thesis compares two methods of constructing polypyrrole trilayers: an electrolyte gel method and a gold coated PVDF membrane method. It will discuss the construction processes as well as properties of resulting trilayers by looking at force production, strain rate, etc.
by Wei Hsuan (Jessie) Ho.
S.B.

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19

Katz, Benjamin G. "Low cost, high performance actuators for dynamic robots." Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/105580.

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Анотація:

Thesis: S.B., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2016.
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (page 47).
The recent growth of the remote control airplane and drone market has created great availability of extremely cheap, yet very power and torque dense electric motors. However, these motors have for the most part been neglected by the robotics community. This thesis documents the development of a hardware, firmware, and controls platform for using these motors in robotics applications - specifically for running robots. A sampling of these motors were characterized, and appropriate position sensing, power electronics and field-oriented motor control systems for torque, position, and impedance control of the motors was developed. Additionally, a module which combines motor, electronics, and single-stage planetary gearset was designed and fabricated. For demonstration, a pair of these motor-controller- gearbox modules were incorporated in a 2-degree- of-freedom leg capable of jumping and controlling its joint impedances.
by Benjamin G. Katz.
S.B.

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20

Li, Jian Ph D. Massachusetts Institute of Technology. "Electrostatic zipping actuators and their applications to MEMS." Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/33678.

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Анотація:

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2004.
Includes bibliographical references (p. 161-168).
Electrostatic actuation is the most common and well-developed method of generating motion on the micro scale. To overcome the challenge of providing both high force and large displacement, electrostatic zipping actuators have been developed and applied to various devices. As device thicknesses increase, however, conventional laterally- moving zipping actuators become less practical due to their high pull-in voltages caused by their minimum achievable electrode gaps. This thesis presents a fundamental improvement of the laterally-moving electrostatic zipping actuator. Its major contributions are: 1) a compliant starting zone is introduced into the fixed electrode to significantly reduce the pull-in voltage of the zipping electrode; 2) numerical and analytical methods are developed to solve general zipping actuator problems; 3) optimization is performed to minimize the effort required to actuate the zipping electrode and its load; and 4) the improved zipping actuators are designed into a relay to illustrate their use and performance. To design a cross-bar micro relay, two zipping actuators are combined with a curved bistable switch beam and two contacts.
(cont.) The micro relay is monolithically fabricated in silicon using deep reactive ion etching to move laterally in the wafer plane. Both actuators provided up to 10 mN of actuation force over their 80 [mu]m of stroke at 140 V, and toggle the bistable relay at a maximum rate of 160 Hz. Pullin voltage, actuation voltage and force-displacement measurements of the actuators and switch beam confirm theoretical expectations based on numerical, analytical and finite element analyses, after accounting for fabrication variations. The shortest pulse required to switch the relay is 400 [mu]s, and the time taken for the actuator to close the relay was approximately 3 ms. The relay was operated at 100 Hz for over 120 hours through more than 40 million cycles without any observed stiction or fracture fatigue. To achieve low contact resistance for a laterally-moving micro relay, wet anisotropically etched silicon [111] planes are developed to form relay contact surfaces that offer flat wiping surfaces and ease of thick metalization. Experimental contacts are fabricated and their average contact resistance is measured to be [approx.] 50 m[omega].
(cont.) A process plan is also proposed to combine the [111] plane contacts with the prior zipping actuators and the switch beam to build a micro relay with low contact resistance for power protection applications. The compliant starting zone concept can also be applied to vertically-moving MEMS devices. A MEMS valve is also designed using a zipping actuator having com- pliant starting zones. As another application of the zipping mechanism, a nonlinear spring is also presented and analyzed.
by Jian Li.
Ph.D.

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21

Vogan, John D. (John DeWayne) 1979. "Development of dielectric elastomer actuators for MRI devices." Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/27133.

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Анотація:

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2004.
Includes bibliographical references (leaves 100-104).
Dielectric elastomer (DE) actuators are an emerging class of polymer actuation devices. They exhibit large strains and have high force and energy densities. They can be designed in a variety of geometries and are inexpensive to manufacture. Currently, the use of DE Actuation is limited because quantitative design information is incomplete and the complex phenomena governing their performance have not been fully characterized. In this study, several such issues are investigated both experimentally and analytically. The actuators designed for this research function as binary actuators, that is, they operate between two set states, OFF and ON. Performance of the actuators is predicted based on theoretical analysis and the results are compared to experimental results. Improvement of fabrication methods and determination of optimum design parameters have been experimentally determined. Since DE actuators can be constructed out of polymers and without any ferromagnetic materials, they can potentially be used in a Magnetic Resonance Imaging (MRI) machine, which has strict compatibility requirements that limit the use of certain materials. MRI is a powerful and effective medical diagnostic tool, but treatment is limited because of the confined space and compatibility issues. It has been well recognized that its value would be increased if it were possible to physically manipulate objects within the MRI machine during imaging, but conventional manipulation systems cannot operate within an MRI due to the incompatibility of ferromagnetic materials. Binary DE actuators eliminate the need for conventional electromagnetic actuators and their associated controlling electronics. This inherent compatibility suggests that a new class of MRI treatment devices
(cont.) is possible. Potential applications for use in the MRI environment are introduced, and prototypes for illustrating these applications are fabricated. One such application, a reconfigurable RF coil for flexible imaging capabilities, proves that not only are DE actuators and MRI compatible, but that they can significantly enhance imaging capabilities.
by John D. Vogan.
S.M.

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22

Garcia, James Christopher. "Active helicopter rotor control using blade-mounted actuators." Thesis, Massachusetts Institute of Technology, 1994. http://hdl.handle.net/1721.1/36436.

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23

Sun, Xu S. M. Massachusetts Institute of Technology. "Pouch motors : printable pneumatic actuators for foldable robotics." Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/100351.

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Анотація:

Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2015.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 91-94).
We envision future electro-mechanical devices can be printed on planer structures and folded autonomously for robotic applications. This thesis project is devoted for the development of self-folding and actuation of such robots, with a novel actuator called pouch motors. Pouch motors is a family of printable pneumatic actuators in the pouch form that drives motion with inflations and deflations. It is customizable in design, inexpensive to fabricate and planer in nature, making it ideal for origami inspired robots. In the first half of this thesis, Pouch motor's actuation mechanisms with theoretical and experimental assessments are introduced. Design and fabrication work flows are described. In the second half of the thesis, different configurations of pouch motors are presented not only for robot self-folding, but also for applications in human computer interaction. The thesis highlights the robotic garden project as a representative example, bringing a discussion of future development.
by Xu Sun.
S.M.

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24

Neal, Devin Michael. "Large-strain piezoelectric actuators using controlled structural buckling." Thesis, Massachusetts Institute of Technology, 2009. http://hdl.handle.net/1721.1/55282.

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Анотація:

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2009.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 59-60).
Buckling is a highly nonlinear and singular phenomenon in thin beams, and is usually an undesired characteristic that must be prevented from occurring in engineered systems. Buckling, however, can be a useful mechanism for gaining extremely large displacement amplification, since a infinitesimal displacement in the axial direction of the beam may lead to a large deflection in the middle of the beam. This thesis presents a novel large-strain piezoelectric actuator exploiting the buckling of a structure with imbedded piezoelectric stack actuators. The realization of this buckling actuator began by rethinking the paradigm of where PZT stacks are placed in traditional flexure-based displacement amplification mechanisms. Although the free displacement of a PZT stack is only 0.1% of the stack length, the buckling mechanism can produce a large bipolar displacement that is approximately 150 times larger than the original PZT displacement. Furthermore, the structural buckling produces a pronounced nonlinearity in output impedance; the effective stiffness viewed from the output port varies as a function of output displacement, which can be a useful property for those applications where actuator stiffness needs to vary. Buckling is controlled with phased activation of the input units and either 1) a strategically placed redirecting stiffness or 2) multiple buckling units working in parallel.
by Devin Michael Neal.
S.M.

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25

Fofonoff, Timothy Andrew 1977. "Fabrication and use of conducting polymer linear actuators." Thesis, Massachusetts Institute of Technology, 2008. http://hdl.handle.net/1721.1/46482.

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Анотація:

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2008.
Includes bibliographical references (leaves 128-135).
The development of biomimetic devices will benefit from the incorporation of actuators with combinations of properties common to biological systems, for example low density, controllable mechanical flexibility, and compact size. Conducting polymers, such as polypyrrole, exhibit muscle-like properties and the potential to provide the above capabilities while delivering significant forces over useful displacements. Current conducting polymer linear actuators, however, are generally limited to displacements of less than 0.5 mm, forces of less than 1 N, and cycle frequencies of less than 0.1 Hz. These materials are rarely tested on a length scale of more than a few millimeters, and their incorporation into real applications has to date been limited. This work focuses on improving and scaling conducting polymer linear actuators for application in macroscale systems. A new fabrication method is described that delivers polypyrrole ribbons with uniform thicknesses of 10 to 30 [mu]m, widths of 20 [mu]m to 20 mm, and lengths exceeding 5 m. A second method is described where a conductive gold layer is incorporated into the ribbons and is shown to enhance performance and mitigate limiting effects common to longer conducting polymer actuators. Additionally, parallel actuation is explored as a method to achieve greater forces without compromising actuation speed. The integration of these actuators into stand alone systems that include joints and flexures has yielded novel techniques in amplifying motion while minimizing friction, improving electrical connection, and increasing actuator lifetime. The challenges of incorporating these actuators into an example biomimetic system are discussed and an approach is introduced. These methods and systems are shown to have increased conducting polymer linear actuator displacement output, force output, and actuation speed each by a full order of magnitude, thus bringing this technology closer to practical incorporation and use in biomimetic systems.
by Timothy Andrew Fofonoff.
Ph.D.

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26

Yun, Yeoheung. "Nanotube Sensors and Actuators in Mechanics and Medicine." University of Cincinnati / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1150836513.

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27

Zhong, Jinghua. "Modeling and adaptive robust motion control of piezoelectric actuators." Thesis, Purdue University, 2014. http://pqdtopen.proquest.com/#viewpdf?dispub=3636707.

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Анотація:

High performance motion trajectory tracking can be achieved on a piezoelectric stack actuator stage by the combination of a new hysteresis model, judicious modeling of the dominant dynamics, and adaptive robust control design.

A new hysteresis model for piezoelectric actuators is proposed. Inspired by the similarity between pre-sliding friction and piezoelectric hysteresis, the Dahl friction model is extended with non-local memory to model piezoelectric hysteresis. Asymmetry in hysteresis loops is accommodated with a shaping function, which eliminates the need for having different parameters for different branches of the hysteresis loops. All parameters of the hysteresis model can be identified from the outer-loop alone, and the identified model reduces hysteresis nonlinearity from 14 percent of the actuator range to less than 1 percent.

A low-order dynamic model is developed by recognizing the domain switching dynamics of the actuator as the dominant dynamics when the resonant frequency of the stage is far beyond the application bandwidth. The piezoelectric dynamics is well approximated by a feed-through gain and a first-order nonlinear dynamics driven by the input with hysteretic disturbances.

Based on the parameterized model, an adaptive robust controller is designed to achieve (a) guaranteed transient error under the assumption of bounded uncertainties and disturbances; and (b) asymptotic tracking in the presence of parametric uncertainties only. Good tracking performance is achieved for large amplitude trajectories up to 100 Hz even when the hysteresis is entirely attenuated as an unknown disturbance. With additional model compensation from the hysteresis model, the final tracking errors are more than two orders of magnitude smaller than previously reported in literature on an identical actuator.

For single-loop periodic trajectories, performance can be improved without using an explicit hysteresis model. By approximating the unknown but periodic uncertainty with harmonic basis functions and adapting their amplitudes online, non-parametric uncertainty from unknown hysteresis is significantly reduced. Experimental results demonstrate tracking error down to the sensor noise level for sinusoidal trajectories up to 100 Hz with moderate amplitudes and less than one percent for large amplitudes.

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28

Bosworth, William R. Ph D. Massachusetts Institute of Technology. "Design and parametric simulation of radially oriented electromagnetic actuators." Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/67792.

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Анотація:

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2011.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 91-92).
This thesis presents the design and simulation of an electromagnetic actuator system capable of delivering large pulses of radial force onto a cylindrical surface. Due to its robust design, simple control scheme, and large output force capability, the actuator design is developed to be considered for wellbore manipulation and other downhole oil exploration and production activities. The complete simulation - including capacitor bank power supply, solid state switching circuit, transducer, and target formation - is a thirteen value lumped parameter model. The simulation was used heavily in the design and refining of two experimental prototype systems. These prototypes showed excellent model-experiment matching. The experimental prototypes are 2.5" radius, 12" length cylindrical transducers that exert nearly 10 psi onto a simulated rock formation with 2 MN/m radial stiffness, increasing the formation radius 3.5 mm during 5 ms pulse events. It is with this experimentally validated simulation that we project forward a manufacturable system capable of exerting pulses of hundreds of psi in magnitude over durations of 1 - 10 ms onto wellbore sized cylindrical surfaces.
by Will Bosworth.
S.M.

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29

Geykhman, Roman. "Optimal placement of binary actuators in deformable optical systems." Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/67794.

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Анотація:

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2011.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 111-113).
Recently, exploration has been conducted into the applicability of binary mechatronics to active figure correction in large optical systems such as space telescopes and ground-based solar-thermal concentrators. This Thesis will continue this exploration. The information-theoretic requirements of the corrective commands required in active optics will be explored to understand the dimensionality of the continuous workspace sampled by binary actuation. In both the minimal expected error and the minimal computation time sense, the optimal discrete workspace is the uniform discrete distribution. A rigorous analogy between binary mechatronics and discrete random variables will be used to show that this optimal workspace is achievable by a linear superposition of actuators with exponentially decreasing influences on the optical surface. It will be proven that elasticity can be exploited to construct mechanisms where constant magnitude actuators exhibit exponentially decaying influences on certain parts of the mechanism, allowing for designs where individual binary actuators correspond to binary bits of the required deformation. A planar truss mechanism designed with this philosophy will be presented and shown to have independent kinematic control of multiple adjacent displacements on its top side. Finally, this design will be shown extend to three dimensions in a manner applicable to optical figure correction. Due to the complexity of mechanisms that meet the optimality criteria, only theoretical analysis will be presented.
by Roman Geykhman.
S.M.

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30

Cromie, Melinda Joy. "Multifunctional systems with polymer actuators : mechanochromism and peristalic pumping." Thesis, Massachusetts Institute of Technology, 2005. http://hdl.handle.net/1721.1/33902.

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Анотація:

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2005.
Includes bibliographical references (leaves 105-109).
The mission of the ISN is to explore the long-range vision of the role of nanotechnology in the future of soldier protection. Unprecedented survivability will arise from the cohesive and comprehensive coordination of the functions and interactions of each technology. The present work approaches these objectives with basic research to support the development of two multifunctional soldier survivability systems, pumping microfibers and mechanochromic pixels. Progress was made along the two major paths of investigation towards the realization of a pumping microfiber. Polypyrrole was chemically deposited onto copolyetherester. Tubular polypyrrole actuators at the millimeter scale were electrochemically fabricated and actuated. Mechanochromic polymers can be combined with actuating polymers to create a color changing pixel. Reflectance spectrum changes with strain in mechanochromic materials were characterized. Several pixel designs were analyzed and tested in which the polymer actuator polypyrrole induces deformation of the mechanochromic block copolymer. Integrative studies inform the overall systems architecture of the far future battlesuit. Scoping calculations to investigate battlesuit functionality requirements were performed.
(cont.) The multiscale, multifunctional design solutions employed in the human body and the US Army and were studied, and the Dynamic Systems Integration Map was developed to apply the lessons learned to coordinate and leverage the many emerging survivability technologies.
by Melinda Joy Cromie.
S.M.

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31

Tubilla, Kuri Fernando. "Development of a morphing helicopter blade with electrochemical actuators." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/38933.

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Анотація:

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2007.
Includes bibliographical references (p. 167-170).
The use of the expansion of electrochemical cells, upon ion intercalation, for the development of a morphing helicopter blade is explored. Using commercially available lithium-ion batteries as demostrators of the technology, two actuator prototypes suitable for the application are developed. The first prototype consists of a weave of fibers enclosing an array of cells in such a way that the thru-thickness expansion of the cells is transformed into an in-plane contraction. A mathematical model of the actuator is developed and used for the prototype design, which is then implemented using three cells and steel wires. Tests performed on the prototype show that, after accounting for viscoelastic phenomena, the prototype free strain agrees well with the model predictions. A Blade Element Momentum Theory model of the helicopter rotor, used for the design of the second actuator prototype, is described. The model is used for evaluating a morphing scheme in which the blade deforms its trailing edge by different amounts along the span. Under this scheme, a suitable blade twist in terms of forward flight performance can be selected, and the trailing edge deflection is then used to improve the performance in hover.
(cont.) Applying the model to a Bell 427 helicopter, it is found that, starting with a blade with 40 less twist than the baseline blade and an expanding cell with an energy per mass of 78 J/kg, it is possible to generate enough flap deflection to improve hovering performance by about 1%, with an actuator that increases the blade mass by less than 10%. The design of a blade actuator based on this trailing edge deflection scheme is then described. It consists of a pair of stacks enclosed inside the blade spar, transferring their motion to the flap via two pushrods and a set of steel flexures. A lumped-parameter model is used for the design and optimization of the actuator, and it is later validated using a finite element software package. Results from the tests on a short scaled section of the morphing blade are presented and compared with the theoretical model.
by Fernando Tubilla Kuri.
S.M.

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32

Green, Stephen Marcus 1957. "Manipulation of a rectangular air jet using piezoelectric actuators." Thesis, The University of Arizona, 1992. http://hdl.handle.net/10150/278089.

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Анотація:

An air jet emanating from a rectangular conduit with exit plane dimensions 7.62 cm x 1.27 cm (aspect ratio 6:1) is forced using four piezoelectric actuators mounted along the long sides of the jet opening. Excitation is effected via amplitude modulation of the resonant carrier waveform. Although the flow is not normally receptive to excitation at the actuator resonance frequency, if the excitation amplitude is high enough, spreading of the forced segments of the jet shear layer can lead to a significant deflection of the jet column. When the amplitude modulated excitation is high enough, the input waveform is effectively demodulated by a nonlinear process related to the formation and coalescence of nominally spanwise vortices. The resulting effect is the spatial amplification and attenuation of the modulation and resonant wavetrains, respectively. The choice of different spatial/temporal wavetrains can result in the excitation of spanwise and streamwise instabilities of the jet column.

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33

Hua, Sarah T. "The development and characterization of soft robotic contractile actuators." Thesis, Massachusetts Institute of Technology, 2019. https://hdl.handle.net/1721.1/123287.

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Анотація:

Thesis: S.B., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2019
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 51-52).
In this paper, I describe the development of a soft-robotic myocardium and pneumatic artificial muscles (PAMs) that replicate the physiological motion of the heart. We were able to generate physiological twisting motion in a confined geometry, but additional actuators would be required to generate physiological force for blood ejection. However, McKibben PAMs with thermoplastic polyurethane (TPU) bladders were too bulky and prevented the embedding of additional actuators. Therefore, multiple alternate PAM designs which occupy minimal unpressurized volume were explored. Of the various bladder and mesh pairings for traditional McKibben PAMs, latex bladders with nylon braided mesh proved the most promising. 2D PAMs with zero volume bladders were also developed: 2D McKibben, 2D Pleated, and 2D Cardiac Geometry PAMs. Candidate PAMs were characterized and compared to the physiological linear contraction (14.7%) and force generation (60N) of the heart. The 2D PAMs successfully reduced the volumetric footprint and were able to generate a maximum force of 0.46 N/cm3 (7mm-width five channel 2D McKibben PAM matrix), close to the amount generated by the baseline TPU PAMs (0.53 N/cm3), and up to 10.1% linear contraction (3mm-width nine channel 2D McKibben PAM matrix). However, none of the PAM matrices characterized were able to meet both linear contractile and force generation targets. With more characterization and iteration, the 2D PAMs seem promising for the biomimetic soft-robotic myocardium application.
by Sarah T. Hua.
S.B.
S.B. Massachusetts Institute of Technology, Department of Mechanical Engineering

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34

Maccarana, Yamuna. "Health Monitoring of Electro-Mechanical Actuators for primary flight surfaces." Doctoral thesis, Università degli studi di Bergamo, 2019. http://hdl.handle.net/10446/128462.

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This thesis has been developed under the funded project named REPRISE (Reliable Electromechanical actuator for PRImary SurfacE with health monitoring), which aims to design a novel Electro-Mechanical Actuator (EMA) to be used on primary flight surfaces of small aircrafts. The main feature of the enhanced system is a novel embedded Health Monitoring (HM) component, which aims at assessing the grade of deterioration of the specimen without resorting to additional sensing within the EMA, but by monitoring the indirect effects that the operating degradation of the mechanical transmission elements has on measurements not directly related to their status. The entire work has been validated experimentally by the employment of a dedicated test bench to perform endurance tests, gradually leading the mechanical components to final failure. The deterioration has been evaluated also by visual inspection and screw thread profile measurements. The effectiveness of the CD algorithm has been proven despite there was no evidence of loss of ability in pursuing the EMA main function of position tracking. This work delivers an important contribution to the More Electric Aircraft mission and lies the foundation for the development of an HM module able to estimate the Remaining Useful Life (RUL) of the specimen and thus allowing maintenance actions when the an upcoming failure is advised, in a Predictive Maintenance strategy.

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35

Piron, Marielle. "Dynamic analysis of fast-acting solenoid actuators." Thesis, University of Glasgow, 1999. http://theses.gla.ac.uk/1874/.

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There has been a recent revival of interest in the design of fast-acting solenoid actuators. This is due to the emergence of new control applications in the automotive industry constrained by tighter emission and noise regulations. In the context of developing a rapid computer-aided design tool for such applications, the thesis proposes several methods for computing the static and dynamic electromagnetic performance of solenoid actuators with a particular attention given to two actuator types : an axisymmetric and a rectangular solenoid actuator with a flat-faced armature. The magnetostatic performance of both actuator types is first evaluated by developing a detailed magnetic equivalent circuit in which the actuator geometry, saturation and end-effects are all taken into account. A comparison of the analytical model, based on the computation of the magnetisation characteristics and static forces for several airgap lengths, is given with finite-elements and measurements. In order to increase the computational speed of the static performance, the concept of magnetic gauge curve is presented. It is shown that this approach is in principle valid for any type of variable reluctance machine. Although the complexity of the gauge curve expression varies significantly from one device to another, it is shown that this method is an efficient way to store the magnetic data for a rapid computer aided-design or a real time application. When applied to the two previous types of solenoid actuator, it also leads to a very fast and accurate static force computation. The dynamic performance of the solid iron actuators requires the evaluation of the magnetic damping due to eddy currents. Based on a ID model of the flux and eddy current diffusion within an iron bar, an electromagnetic equivalent circuit of the axisymmetric is derived, in which the material nonlinearity, armature movement and eddy currents, a function of the previous parameters, actuator geometry and driving conditions, are modelled. A dynamic model of the partly solid iron rectangular actuator is also proposed and evaluated. In both cases a comparison of the transient current and force waveforms with 2D or 3D finite elements and measurements is given under various driving conditions.

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36

Zakariasson, Anton. "Control functions based on brake actuators in combination with other actuators in new vehicles." Thesis, Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-55313.

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Today’s automotive industry evolves very quickly and new technology is integrated into vehicles every day. This technology creates many new actuator-controlled functions and sub-functions having different names and use in every car maker’s program. The thesis has been performed at ÅF Industry chassis department in Trollhättan, Sweden. To get a clear overview and understanding, a benchmarking process have been made for a classic station wagon to sort out and categorize functions for five different car makers. The same process for another car model was also made parallel to this thesis by another student for wider results, while this thesis covers brake actuators and brake actuators in combination with other actuators that student covers other types of actuators. These benchmarking results were then put together and a screening was done to eliminate functions not relevant for my thesis. The remaining functions were analyzed more in depth and a datasheet was created for each function covering basics such as its functions, how it works, pros and cons, parameters and an estimated cost. This will be used for clarifying the functions for ÅF’s engineers when needed. Evaluation of the function Electronic Stability Programme (ESP) was also done through testing at NEVS test track in Trollhättan with advanced and accurate test equipment. The ESP evaluated by a standardized test method SS-ISO 3888-2, Severe lane-change maneuver – Part 2: Obstacle avoidance where the track was completed in various speeds with ESP activated and ESP deactivated. By having ESP activated, control of the vehicle was gained and skidding was repealed. The results did not show off a great difference but there were clear signs and data that the ESP affected the vehicle in a positive way.
Dagens fordonsindustri utvecklas i ett rasande tempo där det kommer ny integrerande teknik varje dag som baseras på aktuatorer (ställdon). Denna teknik skapar många nya aktuatorbaserade funktioner och sub-funktioner som alla har olika benämningar och användningsområde inom varje biltillverkares utbud. Arbetet har utförts hos ÅF Industry chassiavdelningen i Trollhättan, Sverige För att få en tydlig överblick och för att skapa förståelse, så har en benchmarking-process genomförts för en klassisk herrgårdsvagn för att sortera och kategorisera fem olika biltillverkares funktioner. Samma process har även genomförts parallellt av en annan student för bredare resultat. Detta arbete täcker funktioner som är baserade på bromsaktuatorer och bromsaktuatorer i kombination med andra aktuatorer medan den andra studentens arbete täcker andra sorters aktuatorer. Resultatet från bådas benchmarking lades ihop och en sållning gjordes för att avlägsna irrelevanta funktioner för denna rapport. De kvarvarande funktionerna analyserades mer på djupet och ett faktablad skapades där funktion, hur den fungerar, för- och nackdelar, parametrar och pris täcktes. Dessa kommer att användas när ÅFs ingenjörer är osäkra på vad det är för funktion och hur den fungerar. Utvärdering av Electronic Stability Programme (ESP)- funktionen har gjorts genom testning på NEVS testbana i Trollhättan med avancerad och noggrann testutrustning. En standardiserad testmetod, SS-ISO 3888-2:2011 – Provbana för kraftig undanmanöver – Del 2: Undvikande av hinder, användes genom att köra testbanan i olika hastigheter med ESP aktiverat och med ESP avaktiverat. Genom att låta ESP vara aktiverat så fås ökad kontroll och sladd upphävs effektivt. Det var ingen markant skillnad i resultatet men det var tydligt att ESP:n påverkade kontrollen över fordonet positivt.

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37

Abolfathi, Nobari Nona. "Attitude dynamics and control of satellites with fluid ring actuators." Thesis, McGill University, 2013. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=117121.

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Successful mission of a satellite depends on maintaining a fixed orientation with respect to the Earth. However, the attitude angles of a satellite can be perturbed because of various natural disturbance sources, such as the Earth's gravity gradient, solar radiation pressure, and the Earth's magnetic field. Modeling the attitude dynamics and developing a controller to stabilize the attitude motion are quite important steps in the design of satellites. Although several actuators exist to control the attitude motion, a novel type considered in the thesis, shows promise of producing a high torque to mass ratio. This potential justifies the in-depth study reported. The novel actuator in question consists of a ring containing fluid, whose flow is regulated by a pump. The control torque is produced due to the variation of the angular velocity of the fluid. In this thesis, first, a redundant actuator system composed of four fluid rings in a pyramidal configuration is studied. The dynamical model of the system is developed for a satellite travelling either in a circular or an elliptical orbit. The dynamical analysis of this system leads to an underdetermined system of nonlinear differential equations, whose solution without considering the control input (the torque produced by the pump pressure) shows that the fluid rings can damp out the attitude disturbances of a satellite in a circular orbit and the roll-yaw disturbances in an elliptical orbit. However, this passive damping effect is fairly slow; an active controller is hence designed in the next step. The effect of the failure of one fluid ring on the performance of the attitude control subsystem (ACS) of a satellite is also studied. It is observed that even in the case of failure of one fluid ring, the satellite can be stabilized by slight modification of the active controller. Later, a sliding mode controller is designed to cope with the uncertainties existing in the fluid model and in other parameters of the system. Although the results achieved are quite satisfactory, the chattering that exists in the steady response of the system is not desirable; hence a switching controller consisting of a sliding mode and a PID control law is designed to eliminate this chattering effect. Next, the theoretical results obtained are validated by conducting several experiments. Although the experimental results confirm the theory developed in this thesis, the large torque-to-mass ratio expected is revealed to be only possible at the cost of a quite high input voltage to the pumps regulating the flow. Therefore, two novel applications of fluid rings are proposed: as an actuator for spin stabilized satellites, or as an auxiliary actuator in satellites with magnetic torquers.Using fluid rings in spin stabilized satellites is proposed in the thesis, as an alternative to the commonly used micro-thrusters. Here, two fluid rings are mounted on the satellite while their axes of symmetry are aligned with the roll and yaw axes. To examine the feasibility and performance, a dynamical model of this spinning satellite with two fluid rings is developed. A controller is then designed to stabilize the attitude motion of this satellite.The second novel actuator system developed here consists in using fluid rings as complementary actuators in satellites with two magnetic torquers. The dynamical model is formulated, and a controller is designed to investigate the performance of this system. The simulation of the system without the fluid ring shows that the satellite attitude can be stabilized by using only two magnetic torquers, however, slowly. Upon adding the active fluid ring actuator to the system, the stabilization time is reduced by a factor of 10. The failure of the fluid ring and each magnetic torquer is also studied.
La réussite d'une mission d'un satellite dépend du maintien d'une orientation fixe par rapport à la Terre. Toutefois, les angles d'attitude d'un satellite changent en raison d'excitations diverses. Un modèle dynamique est utile pour prédire l'attitude du satellite le développement un contrôleur pour stabiliser l'attitude est également importantes. Un nouvel actionneur pour le contrôle de l'attitude est proposé dans cette thèse. L'actionneur fluidique produit un couple élevé par rapport à la masse. L'actionneur en question se compose d'un anneau rempli par un fluide. L'écoulement de ce fluide est régulé par une pompe. Le couple de commande est produit par la variation du moment cinétique du fluide.Un système d'actionnement redondant composé de quatre anneaux de fluide dans une configuration pyramidale est d'abord étudié. Le modèle dynamique du système est développé pour un satellite voyageant dans une orbite circulaire ou elliptique. L'analyse dynamique de ce système mène à un système sous-déterminé d'équations différentielles non-linéaires. La solution, sans tenir compte du couple produit par le contrôleur, montre que les anneaux de fluide peuvent agir comme régulateurs passifs, ce qui amortit les perturbations d'attitude d'un satellite sur une orbite circulaire et les perturbations en roulis-lacet selon une orbite elliptique. Cependant, cet effet d'amortissement passif est assez lent. Par conséquent, le contrôleur actif fut conçu. Les résultats obtenus montrent que les angles d'attitude du satellite sont stabilisés rapidement. De plus, l'effet de la défaillance d'un anneau liquide sur la performance du sous-système de contrôle d'attitude (SCA) du satellite est étudié. On constate que, même dans le cas de défaillance d'un anneau de fluide, le satellite peut être stabilisé par la modification du contrôleur actif. En raison des limites de ressources de calcul dans les applications spatiales, un modèle simple de l'écoulement du fluide est adopté ici. Un contrôleur au mode glissant est donc conçu pour être robuste aux incertitudes dans le modèle hydraulique et dans les paramètres du système.Les résultats théoriques sont validés expérimentalement. Bien que les résultats expérimentaux confirment la théorie développée dans cette thèse, le grand couple à rapport de masse nécessite un coût de tension d'entrée très élevé pour les pompes de régulation du débit. Par conséquent, deux nouvelles applications d'anneaux de fluide sont proposées dans cette thèse: comme actionneur pour les satellites stabilisés de spin, ou comme actionneur auxiliaire avec magnéto-coupleurs.L'utilisation des anneaux de liquide dans les satellites stabilisés par rotation est le premier champ d'application proposé comme une alternative aux courants micro-propulseurs. Dans ce système, deux anneaux de fluide sont montés sur le satellite alors que leurs axes de symétrie sont alignés avec les directions de roulis et de lacet. Pour vérifier la faisabilité et la performance, un modèle dynamique de ce satellite en rotation avec deux anneaux de fluide est développé. Ensuite un contrôleur modifié est conçu pour stabiliser l'attitude du satellite. Le deuxième système d'actionneur est développé en utilisant les anneaux de fluide comme actionneurs complémentaires dans les satellites avec magnéto-coupleurs. Un modèle dynamique est développé, et un contrôleur est également conçu pour étudier la performance de ce système. Le système est d'abord examiné sans l'utilisation de l'anneau de fluide. Les résultats montrent que le satellite est stabilisé par seulement deux magnéto-coupleurs, mais lentement. Après l'ajout de l'actionneur actif de l'anneau de fluide dans le système, le temps de stabilisation est réduit par un facteur de dix. L'échec de l'anneau de fluide et de chaque couple magnétique sont testés.

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38

MacKenzie, Ian (Ross Ian). "Design and control methods for high-accuracy variable reluctance actuators." Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/100138.

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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2015.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 421-427).
This thesis presents the design and control techniques of a variable reluctance actuator for driving a reticle motion stage in photolithography scanners. The primary thesis contributions include the design and experimental demonstration of a magnetic flux controller that uses a sense coil measurement, the design and experimental demonstration of a novel method to estimate actuator hysteresis in real-time, and the development of an actuator model that incorporates the effects of eddy currents. The reticle stage in a scanning lithography machine requires high accelerations combined with sub-nanometer position accuracy. Reluctance actuators are capable of providing high force densities (force per moving mass) and lower power values relative to the present state-of-the-art Lorentz actuators that are used to drive the reticle stage. However, reluctance actuators are highly nonlinear with both current and air gap. They also display other nonlinear behavior from hysteresis and eddy currents. Linearizing the reluctance actuator is required for the high force accuracy required in the scanning stage. In this thesis, we present a way to linearize the reluctance actuator with flux control using a sense coil as the feedback measurement. Because the sense coil is AC-coupled, we design a low-frequency estimate of the magnetic flux based upon the actuator current and air gap measurements. We combine the low-frequency estimate with the sense coil measurement using a complementary filter pair that provides an estimate of the flux from DC to frequencies of several kHz. For the low-frequency estimate, we develop a novel method for estimating the actuator hysteresis in realtime. For this flux estimator, we use an observer to model the actuator flux which treats the changing air gap as a disturbance to the plant model. The use of an observer allows the identification of a single-variable hysteresis model of actuator current rather than a two-variable hysteresis model of current and air gap. We also introduce a novel way for expressing the actuator hysteresis, whereby we incorporate the linearizing effect of the air gap directly into a Preisach hysteresis model via a change of variables. We demonstrate experimentally that this method is numerically stable in the presence of a dynamically changing gap, in contrast to some alternative methods. We designed and built a reluctance actuator prototype and 1-DoF motion testbed to demonstrate the accuracy of the actuator models and control techniques. We experimentally demonstrated that we can achieve a flux control bandwidth of 4 kHz that is capable of reducing the stiffness of the reluctance actuator to less than 0.012 N/[mu]m for frequencies up to 100 Hz. This results in a force error of less than 0.03% of the full-scale force for a 10 [mu]m air gap disturbance at this frequency. We also demonstrate that the actuator hysteresis model is capable of estimating the actuator flux accurately in the presence of dynamic gap disturbances of at least 35 1m peak-to-peak and with a static offset from the nominal air gap of at least 50 [mu]m.
by Ian MacKenzie.
Ph. D.

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39

Nakamura, Mealani 1978. "A torso haptic display based on shape memory alloy actuators." Thesis, Massachusetts Institute of Technology, 2003. http://hdl.handle.net/1721.1/89927.

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40

Chambers, Joshua Michael. "Design and characterization of acoustic pulse shape memory alloy actuators." Thesis, Massachusetts Institute of Technology, 2005. http://hdl.handle.net/1721.1/32378.

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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2005.
Includes bibliographical references (p. 175-177).
Single crystal Ni-Mn-Ga ferromagnetic shape memory alloys (FSMAs) are active materials which produce strain when a magnetic field is applied. The large saturation strain (6%) of Ni-Mn-Ga, and material energy density comparable to piezoelectric ceramics make Ni- Mn-Ga an interesting active material. However, their usefulness is limited by the bulky electromagnet required to produce a magnetic field. In this thesis, a novel actuation method is developed for shape memory alloys in their martensitic phase, whereby asymmetric acoustic pulses are used to drive twin boundary motion. Experimental actuators were developed using a combination of Ni-Mn-Ga FSMA single crystals and a piezoelectric stack actuator. In bi-directional actuation without load, strains of over 3% were achieved using repeated pulses (at 100 Hz) over a 30 s interval, while 1% strain was achieved in under 1 s. The maximum strains achieved are comparable to the strains achieved using bi-directional magnetic actuation, although the time required for actuation is longer. No-load actuation also showed a nearly linear relationship between the magnitude of the asymmetric stress pulse and the strain achieved during actuation, and a positive correlation between pulse repetition rate and output strain rate, up to at least 100 Hz. Acoustic actuation against a spring load showed a maximum output energy density for the actuator of about 1000 J/m³, with a peak-to-peak stress and strain of 100 kPa and 2%, respectively.
by Joshua Michael Chambers.
S.M.

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41

Levinson, Jacob A. "Design and control of a robotic thumb using piezoelectric actuators." Thesis, Massachusetts Institute of Technology, 2009. http://hdl.handle.net/1721.1/54514.

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Анотація:

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2009.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 38).
Although much more complex and maneuverable than their predecessors, today's anthropomorphic robotic hands still cannot match the dexterity of human hands. While most of these limitations are caused by inadequate sensor and control systems, the use of large, heavy, and stiff actuators can also contribute to dexterity problems. If we expect robotic hands to interact with humans and human objects, joint actuators must allow a compromise of strength and compliance. Piezoelectric (PZT) actuators exhibit a high back driveability which could facilitate this compromise. Although they have low displacement and force output, they are useful in fine control applications. When combined with a DC motor, PZT actuators can produce precise, delicate movements in robotic hands. To develop the novel DC-PZT hybrid system, the force and displacement capabilities of PZT actuators were first characterized with a simple one degree of freedom system. The data from this characterization was analyzed and used to develop a one degree of freedom thumb using a hybrid DC motor/PZT actuator system. To study system performance, a simple position control scheme was implemented for the DC motor and PZT actuators. The experimental results suggest that current PZT actuators, even when combined with a DC motor, cannot produce enough thumb tip force to mirror the functionality of the human hand. That said, improvements to the actuator could make PZT-actuated hands a future possibility.
by Jacob A. Levinson.
S.B.

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42

Xie, Xiaoyue S. B. Massachusetts Institute of Technology. "Modified Maxwell Model for hysteresis compensation of piezoelectric stack actuators." Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/98747.

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Анотація:

Thesis: S.B., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2015.
Cataloged from PDF version of thesis.
Includes bibliographical references (page 29).
This thesis presents new observations of the hysteresis behavior of piezoelectric stack actuators and proposes an Input-Range Dependent Maxwell Model for more accurate hysteresis compensation. Experimental studies show that the assumptions of the classical Maxwell model do not fully hold: the actuator behaves differently in the initiation stage compared to the later cycles, and the parameters of the Maxwell model are dependent on the input history. Two most prominent factors are the input range of the most recent half loop and the local extremum input at the beginning of the current half loop. To accommodate for these variations, two types of modified Maxwell model are presented: the Input-Range Dependent Maxwell Model and the Local-Extremum Dependent Maxwell Model. We further propose parameter estimation schemes for each modified model. In both models, one set of parameters is obtained for the initiation stage and another set for later cycles, and the first Maxwell spring constant is related to the input history - input range or local extremum, respectively. Further studies suggested that the linear dependence of the first spring constant on the input range is much stronger than on the local extremum. Simulations with the identified Input-Range Dependent Maxwell Model gave a maximum percentage error of 2.71%, as compared with a percentage error of 8.29% using the classical Maxwell model. This suggests that the model can accurately predict the response of a piezoelectric stack actuator and is promising for hysteresis compensation in nano-positioning applications.
by Xiaoyue Xie.
S.B.

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43

Savran, Cagri Abdullah 1976. "Broadband active structural control using collocated piezoelectric sensors and actuators." Thesis, Massachusetts Institute of Technology, 2000. http://hdl.handle.net/1721.1/89278.

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44

Ruddy, Bryan P. (Bryan Paul) 1983. "High force density linear permanent magnet motors : "electromagnetic muscle actuators"." Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/78177.

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Анотація:

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2012.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 181-194).
Actuator performance represents a key constraint on the capability of many engineered devices. Performance of these devices is often exceeded by their muscle-powered natural counterparts, inspiring the development of new, "active material" actuators. This thesis reconsiders a traditional actuator, the linear permanent magnet motor, as a form of active material actuator, and presents new, unified scaling and magnetic field models for its performance. This active material motor model predicts that motors composed of large numbers of very small, actively-cooled repeat units, similar to the architecture of biological muscles, can provide greatly enhanced force density over extant designs. Our model is constructed by considering the motor winding as an active material, with its performance limited by the diffusion of waste heat. This allows a quantitative scaling model for the motor constant and force-to-mass ratio to be built for the case of a winding immersed in a homogeneous magnetic field. This model is then modified with a small set of dimensionless parameters to describe the performance penalties imposed by the use of practical sources of magnetic field, specifically periodic arrays of permanent magnets. We explain how to calculate these parameters for a variety of different types of magnet arrays using analytical magnetic field and heat transfer models, and present a new field model for tubular linear motors having improved numerical stability and accuracy. We illustrate the use of our modeling approach with two design case studies, a motor for flapping-wing flying and an actuator for high-performance controllable needle-free jet injection. We then validate our predictions by building and testing a novel water-cooled motor using a tubular double-sided Halbach array of magnets, with a mass of 185 g, a stroke of 16 mm, and a magnetic repeat length of 14.5 mm. This motor generates a continuous force density of 140 N/kg, and has a motor constant of nearly 6 N/[square root]W, both higher than any previously reported motor in this size class.
by Bryan Paul Ruddy.
Ph.D.

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45

Peñalver-Àguila, Lluís Enric. "Piezoelectric buckling actuators : form reduction, bidirectional control, and optimal switching." Thesis, Massachusetts Institute of Technology, 2014. http://hdl.handle.net/1721.1/92131.

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Анотація:

Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2014.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 101-102).
Piezoelectric stack actuators are generally described as having large force density, high bandwidth response, and limited yet precise displacement properties. As a result, these actuators have been widely applied to precision positioning devices, acoustical and optical instruments, and within vibration control mechanisms. Techniques to efficiently amplify this limited displacement have been central to recent piezo-actuator research. One such technique exploits structural buckling to achieve displacement amplification gains greater than 100 while limiting energy transmission loss into the amplifying mechanism. This thesis first surveys the recently developed piezoelectric buckling actuator and identifies critical design elements that may be further optimized to reduce the mechanism's form factor. Focus is directed towards simultaneously reducing structural compliance and mass in the actuator's frame and rotational joints. Use of carbon fiber and new geometry improves structural efficiency while increased joint stiffness is shown through design and material changes. Discussion then shifts to the nondeterministic output of a standalone buckling actuator and methods to address it. A design is presented which couples the buckling actuator to an energy storing mechanism that alternates output direction by enforcing hysteretic force-displacement behavior using a closed loop cam-follower path. Finally, a dual buckling actuator mechanism is discussed which exhibits both quasi-static and dynamic motion properties through asynchronous activation control. Through the use of phase-plane analysis, an optimal switching control law is described. Prototypes of single and dual buckling actuator mechanisms are shown, and experimental performance is presented.
by Lluís Enric Peñalver-Àguila.
S.M.

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46

Secord, Thomas W. (Thomas William). "Modeling, identification, and application of multilayer polypyrrole conducting polymer actuators." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/38702.

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Анотація:

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2007.
Includes bibliographical references.
Experiments were performed using commercially available, self-contained, multilayer polypyrrole (PPy) actuators to develop low-order lumped parameter models of actuator electrical, mechanical, and electromechanical behavior. Experimental data were processed using system identification techniques. Both grey box and black box models were identified. The grey box model consisted of a first order electrical network that was linearly and algebraically coupled to a second order viscoelastic model. The black box model incorporated a third order Box-Jenkins structure and achieved model to data residues comparable to the grey box model. When utilizing validation data, the grey box model showed very good performance for loads in the range of 0.5 to 3 N. Overall, the results of system identification experiments suggested that low order, lumped parameter models were adequate to describe the gross behavior of multilayer actuators. An online identification scheme was developed for monitoring polymer electrical impedance and thereby monitoring the degradation state of an actuator. This identification was performed successfully using recursive least squares and least squares for a discrete impedance model.
(cont.) Experimental validation data, spanning more than 5 hours of continuous operation, were collected and analyzed. A final contribution of this research was the application PPy linear actuators to a custom-designed humanoid foot. Four linear conducting polymer actuators were used to obtain multifunctional behavior of the overall foot. Jacobian analysis of stiffness and damping was performed for the design. Simulations illustrated that PPy actuators through the use of appropriate electrical excitation can modulate their stiffness characteristics as a function of time to match a desired force versus length relationship.
by Thomas W. Secord.
S.M.

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47

Zeng, Chuan. "Deformation and Stability of Dielectric Elastomer Films Used in Actuators." University of Akron / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=akron159662630284948.

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48

Pawar, Amita A. "Smart Material Actuators For Active Tactile Surfaces." The Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1338400866.

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49

Frautschi, Jason Paul. "Finite Element Simulations of Shape Memory Alloy Actuators in Adaptive Structures." NCSU, 2003. http://www.lib.ncsu.edu/theses/available/etd-03302003-174528/.

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Анотація:

Shape memory alloys possess an inherent actuation capability that makes them attractive as actuators in adaptive structures, especially in applications in which their large strains, high specific work output and potential for structural integration are beneficial. However, the requisite extensive physical testing has slowed development of potential applications and highlighted the need for a simulation tool for feasibility studies. In this study, such a tool has been developed by implementing the Müller-Achenbach-Seelecke shape memory alloy model into a commercial finite element code. The material model is described with particular emphasis on its ability to predict actuatoric performance and suitability for use in the context of a displacement-based finite element framework. The interaction between the material model and the solution algorithm for the global finite element equations is thoroughly investigated with respect to the effect of solution parameters on convergence, computational cost and accuracy. Finally, simulations of several flexible structures actuated by shape memory alloys are presented as examples of the potential of the implementation to analyze practical applications. The implementation represents a versatile and novel tool for the simulation of adaptive structural components using shape memory alloy actuators.

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50

Rosmarin, Josiah Benjamin. "Design of a humanoid hand using segmented shape memory alloy actuators." Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/36706.

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Анотація:

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2006.
Includes bibliographical references (leaf 48).
Despite amazing progress in the past two decades, the field of robotics has yet to produce a robotic hand with the same dexterity as the human hand. There has yet to even be a functioning robotic hand of the same size and weight as the human hand. These deficiencies can be attributed to the size, weight and complexity of the actuators used in these robotic hands. Thermal shape memory alloys (SMA's) have characteristics such as high power density which indicate that they would be ideal actuators for such applications. However, certain characteristics of SMA exist which, if left unaddressed, make usage as an actuator impractical. The implementation of SMA for the actuation of a 20 degree of freedom robotic hand and forearm is investigated. A segmented actuation design for the SMA is implemented to address issues of practicality; other issues with regards to the controllability, response time and limited strain of the SMA are addressed. A 20 degree of freedom robotic hand with 16 controlled axes is designed along with a 32 axis actuator box. The designs are realized and the result is a functioning robotic hand of similar size and weight to the human hand. It is concluded that thermal shape memory alloys are a viable solution for the purposes of compact lightweight actuation of vast degree of freedom systems.
by Josiah Benjamin Rosmarin.
S.B.

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