Dissertations / Theses on the topic 'Actuators'
To see the other types of publications on this topic, follow the link: Actuators.
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Actuators.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Potami, Raffaele. "Optimal sensor/actuator placement and switching schemes for control of flexible structures." Worcester, Mass. : Worcester Polytechnic Institute, 2008. http://www.wpi.edu/Pubs/ETD/Available/etd-042808-124333/.
Full textAbstract:
Dissertation (Ph.D.)--Worcester Polytechnic Institute.Keywords: hybrid system, PZT actuators, performance enchancement, actuator placement, actuator switching. Includes bibliographical references (leaves 102-108).
2
Orekhov, Viktor Leonidovich. "Series Elasticity in Linearly Actuated Humanoids." Diss., Virginia Tech, 2015. http://hdl.handle.net/10919/71788.
Full textAbstract:
Recent advancements in actuator technologies, computation, and control have led to major leaps in capability and have brought humanoids ever closer to being feasible solutions for real-world applications. As the capabilities of humanoids increase, they will be called on to operate in unstructured real world environments. This realization has driven researchers to develop more dynamic, robust, and adaptable robots.
Compared to state-of-the-art robots, biological systems demonstrate remarkably better efficiency, agility, adaptability, and robustness. Many recent studies suggest that a core principle behind these advantages is compliance, yet there are very few compliant humanoids that have demonstrated successful walking.
The work presented in this dissertation is based on several years of developing novel actuators for two full-scale linearly actuated compliant humanoid robots, SAFFiR and THOR. Both are state-of-the-art robots intended to operate in the extremely challenging real world scenarios of shipboard firefighting and disaster response.
The design, modeling, and control of actuators in robotics application is critical because the rest of the robot is often designed around the actuators. This dissertation seeks to address two goals: 1) advancing the design of compliant linear actuators that are well suited for humanoid applications, and 2) developing a better understanding of how to design and model compliant linear actuators for use in humanoids.
Beyond just applications for compliant humanoids, this research tackles many of the same design and application challenges as biomechanics research so it has many potential applications in prosthetics, exoskeletons, and rehabilitation devices.Ph. D.
3
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.
Full textAbstract:
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.
4
Cao, J. "Magnetic MEMS actuators." Thesis, University of Cambridge, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.597277.
Full textAbstract:
Magnetic MEMS actuators are presently still relatively under-researched as compared to their electrostatic, piezoelectric and electro-thermal counterparts. Most existing magnetic MEMS actuators are limited to simply delivering a rotational output. The research presented in this thesis aims to develop novel magnetic MEMS actuators with complex structures that are capable of delivering more sophisticated and useful mechanical outputs than the existing devices. The study begins with an attempt to solve the problem of bending a freestanding ferromagnetic cantilever beam with an applied magnetic field. Analytical and numerical models have been constructed and the modelling results are compared to experimental results obtained from a microscopic and a laser measurement system. NiFe alloy has been used as both the magnetic and mechanical element. The magnetic and mechanical properties of electroplated NiFe have been experimentally characterized. Fabrication processes for creating freestanding NiFe structures have been designed and optimized via a parametric experimental study. Finally, novel ferromagnetic microstructures have been designed by combining the motions of more than one ferromagnetic beam. Preliminary magnetic actuation tests have been carried out in order to verify the design ideas.
5
Williamson, Matthew M. (Matthew Murray). "Series elastic actuators." Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/36966.
Full textAbstract:
Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1995.Includes bibliographical references (p. 77-80).
by Matthew M. Williamson.
M.S.
6
Madden, John David Wyndham 1968. "Conducting polymer actuators." Thesis, Massachusetts Institute of Technology, 2000. http://hdl.handle.net/1721.1/8820.
Full textAbstract:
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.
7
Montazami, Reza. "Smart Polymer Electromechanical Actuators for Soft Microrobotic Applications." Diss., Virginia Tech, 2011. http://hdl.handle.net/10919/28084.
Full textAbstract:
Ionic electroactive polymer (IEAP) actuators are a class of electroactive polymer devices that exhibit electromechanical coupling through ion transport in the device. They consist of an ionomeric membrane coated with conductive network composites (CNCs) and conductive electrodes on both sides. A series of experiments on IEAP actuators with various types of CNCs has demonstrated the existence of a direct correlation between the performance of actuators and physical and structural properties of the CNCs. Nanostructure of CNC is especially important in hosting electrolyte and boosting ion mobility.
This dissertation presents a series of systematic experiments and studies on IEAP actuators with two primary focuses: 1) CNC nanostructure, and 2) ionic interactions.
A novel approach for fabrication of CNC thin-films enabled us to control physical and structural properties of the CNC thin-films. We, for the first time, facilitated use of layer-by-layer ionic self-assembly technique in fabrication of porous and conductive CNCs based on polymer and metal nanoparticles. Results were porous-conductive CNCs. We have studied the performance dependence of IEAP actuators on nano-composition and structure of CNCs by systematically varying the thickness, nanoparticle size and nanoparticle concentration of CNCs. We have also studied influence of the waveform frequency, free-ions and counterions of the ionomeric membrane on the performance and behavior of IEAP actuators.
Using the LbL technique, we systematically changed the thickness of CNC layers consisting of gold nanoparticles (AuNPs) and poly(allylamine hydrochloride). It was observed that actuators consisting of thicker CNCs exhibit larger actuation curvature, which is evidently due to uptake of larger volume of electrolyte. Actuation response-time exhibited a direct correlation to the sheet-resistance of CNC, which was controlled by varying the AuNP concentration. It was observed that size and type of free-ions and counterion of ionomeric membrane are also influential on the actuation behavior or IEAP actuators and that the counterion of ionomeric membrane participates in the actuation process.Ph. D.
8
Wissler, Michael Tobias. "Modeling dielectric elastomer actuators /." Zürich : ETH, 2007. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=17142.
Full text
9
Klintberg, Lena. "Miniature Phase-Transistion Actuators." Doctoral thesis, Uppsala University, Department of Materials Science, 2002. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-2138.
Full textAbstract:
Clearly, there is a need for simple, strong actuators capable of large strokes in miniaturized systems such as valves and optical shutters.
The basis for this work is the microstructure technology with processing techniques adopted from the integrated circuit industry. In many cases alternative techniques have been developed to obtain features not achievable with conventional silicon technology. Techniques to fabricate thermally activated phase transition actuators capable of large strokes, as well as strong, piezoceramic actuators, have been investigated
Multilayered piezoceramic actuators have been fabricated and used in a miniature linear motor. A technique to build freestanding, three-dimensional structures drop by drop using a micromachined ink jet head and a slurry of piezoceramic particles has been developed. Ion track technology was used to create narrow pores in polyimide. To make bimorph-like structures capable of large strokes, these pores were impregnated with paraffin- a material with a large volume expansion associated with its solid-to-liquid phase transition. Paraffin was used in a silicon thermal switch intended for a passive thermal control system, and in a device to be used as a valve in a gas regulation system. Finally, paraffin actuators for integration in thermoplastic microfluidic systems have been developed.
During the course of this work not only the importance of identifying the best materials for a given application has been addressed and acknowledged, but also that of finding a processing route on occasion far from the conventional one, and perhaps most important, that of anticipating the often surprising effects following from miniaturization.
10
Snis, Niklas. "Actuators for autonomous microrobots." Doctoral thesis, Uppsala universitet, Institutionen för teknikvetenskaper, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-8720.
Full textAbstract:
This thesis presents actuators used in autonomous microsystems. Characteristic for all actuators presented is the low drive voltage and the low power consumption. Different motion mechanisms have been studied and applied in various locomotion modules for microrobots. High resolution movement of a monolithic piezoceramic PZT rotational arm module, using a quasi-static motion mechanism, was demonstrated in a 10x10x20 mm3 autonomous robot. The rotational arm comprises multilayer PZT bimorphs and is fabricated by a wet-building technology. The multilayer approach enables operation of the modules at the low drive voltages provided by the robot electronics. In addition a locomotion module has been designed and fabricated based on the above principles. A three-legged locomotion module with piezoceramic unimorphs, moving by tapping the legs against the floor, has been investigated. Characteristics such as low power consumption, high velocities, low drive voltages and a high weight carrying capability were demonstrated using a resonant motion mechanism. Highly miniaturized three-legged locomotion modules were developed for a 3x3x3 mm3 autonomous microrobot. The modules comprise a multilayer structure of the electroactive copolymer P(VDF-TrFE) on a flexible printed circuit board (FPC) substrate. A novel multilayer fabrication process suitable for mass production was used. It is based on sequential deposition of spun cast copolymer with evaporated aluminum electrodes. Reactive ion etching is used to microstructure the copolymer and the FPC. The mechanical deformability of the FPC is exploited when folding the 2D FPC-multilayer assembly into 3D locomotion modules. Locomotion was demonstrated by moving a glass slider corresponding to the robot weight. A modular building technology for microsystems is presented. It uses surface mounting technology and conductive adhesives to assemble modules on a double-sided FPC. Complex geometries were achieved by subsequent folding the FPC. The feasibility of the technology was demonstrated by assembly of the 3x3x3 mm3 autonomous microrobots.
11
Klintberg, Lena. "Miniature phase-transition actuators/." Uppsala : Acta Universitatis Upsaliensis : Univ.-bibl. [distributör], 2002. http://publications.uu.se/theses/91-554-5345-7/.
Full text
12
Mirfakhrai, Tissaphern. "Carbon nanotube yarn actuators." Thesis, University of British Columbia, 2009. http://hdl.handle.net/2429/17441.
Full textAbstract:
The first demonstration of electromechanical actuation in carbon nanotubes (CNTs), aligned in the form of a twisted yarn, is presented in this thesis. Sheets of CNTs have been known to actuate when charged electrochemically. When an electric potential is applied between a sheet of CNTs and another electrode, both submersed in an electrolyte, the sheet expands. Actuation loads and stresses are low (< 33 MPa); this is partly due to the random orientation of CNTs in those sheets. When actuated under similar conditions, the yarns show significantly higher stress (2.0±0.4 x 10⁸ Pa) with similar strain (0.6 %). However, unlike the sheets, the yarns contract when the electric potential is applied; this is quite unexpected. The mechanism of this contraction is studied and is related to the insertion of ions in the yarn and the structural changes that take place in the yarn due to its helical twisted structure. A model is presented, relating the actuation strain with yarn geometry (diameter, twist rate, internal packing), electrolyte properties such as ion size, and applied potential. The actuation and mechanical properties of the yarn are studied in various electrolytes. Characterization techniques such as cyclic voltammetry and electrochemical impedance spectroscopy are employed to study the charge storage behaviour of the yarn, showing gravimetric capacitances between 10-60 F/g. It is also shown that the yarns can convert mechanical energy into electrical energy, and are thus capable of measuring mechanical forces. Their behaviour as mechanical force sensors is characterized, showing sensitivities about 2.0±0.6 x 10−⁵ V/MPa. The yarns are superior in work density to piezoelectric actuators when normalized by active material. Creep, can still be an issue, while a tensile modulus of about 16±5 GPa and a tensile strength of about 900 MPa mean that creep is much less than other types of artificial muscles at similar loads. Torsional actuation is also shown to take place if one end of the yarn is free to rotate. Thus, the CNT yarn actuators show the highest achieved stress among polymer artificial muscles and are the first to actuate torsionally, opening a wide range possibilities for applications.
13
Hack, Thorsten. "Stick-slip piezoelectric actuators." Thesis, University of Cambridge, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.624403.
Full text
14
Vasquez, Daniel James. "Flexure-based nanomagnetic actuators." Diss., Restricted to subscribing institutions, 2007. http://proquest.umi.com/pqdweb?did=1383481101&sid=1&Fmt=2&clientId=1564&RQT=309&VName=PQD.
Full text
15
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.
Full textAbstract:
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.
16
Haigh, Richard. "Novel piezoelectric thick film actuators." Thesis, Cranfield University, 2005. http://dspace.lib.cranfield.ac.uk/handle/1826/3814.
Full textAbstract:
Planar-spiral piezoelectric-unimorph-actuators, that deflect out-of-their-plane, were modelled, designed and fabricated. A range of other planar piezoelectric-device designs has also been made. These include spokes, multi-arms, plates and swastikas. All these devices consisted of a mechanical support in the plane with a piezoelectric layer deposited on top. Impedance spectra demonstrated that a fabricated device was piezoelectrically active. Finite-element (FE) models of straight and spiral piezoelectric- unimorph-actuators were constructed. The mechanical stiffness of the spiral-beam was increased with the curvature of the beam; consequently, the inner coils exhibited virtually no deflection and appeared to be redundant. The advantage of the spiral-actuators is that they allow large actuator lengths to be contained compactly without the loss of mechanical stiffness. Fabrication of the above devices necessitated the development of new fabrication technologies. The active-piezoelectric and mechanical-support were a lead zirconate titanate (Pb(Tii_XZrx)O3 - PZT) thick-film and a-platinised-silicon-wafer respectively. Vias were opened in the PZT with wet etching, and this was completed without damaging the back electrode. Powder blasting allowed any 2-dimensional-shape to be cut into the device wafer. Devices were released from the Si support with deep-reactive-ion-etching (DRIE). The PZT thick films were fired with a Cu20-PbO eutectic additive. Pb and Cu were considered to dope on A and B lattice sites (of PZT) respectively, when the PZT was sintered at high oxygen-partial-pressure (p02). The electrical conductivity of PZT thick films was increased when they were sintered at low P02, and this was moderated by the presence of Cu' as an acceptor ion. A lead-platinum intermetallic and lead silicate glass phase simultaneously formed under sintering conditions of low pot, and this simultaneous formation, was accounted for by a six-stage mechanism. Step 1, residual C in the thick film reduces PbO to Pb followed by step 2 where Pb diffuses into the Pt back electrode. In step 3, Pt3Pb formation occurs in the intermetallic layer followed by step 4 in which PtPb forms. Step 5 occurs with saturation of the intermetallic layer as Pb continues to diffuse from the thick film. There is additional diffusion of Pb into the underlying Si substrate. Finally step 6 occurs at some later point, when P02 has risen, Pb is oxidised to PbO, and Si is oxidised to Si02. PbO and Si02 can flux to form PbSiO3 The glass was found to undermine film/substrate adhesion.
17
Lafontaine, Serge R. "Fast shape memory alloy actuators." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape11/PQDD_0004/NQ44482.pdf.
Full text
18
Morrell, John Bryant. "Parallel Coupled Micro-Macro Actuators." Thesis, Massachusetts Institute of Technology, 1996. http://hdl.handle.net/1721.1/7066.
Full textAbstract:
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.
19
Lehto, Marcus. "Paraffin Actuators in Microfluidic Systems." Doctoral thesis, Uppsala : Acta Universitatis Upsaliensis Acta Universitatis Upsaliensis, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-8165.
Full text
20
Masoumi, Tochahi Seyed Amirhosein. "Self-locking in electrical actuators." Thesis, Karlstads universitet, Avdelningen för maskin- och materialteknik, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-16427.
Full textAbstract:
Nowadays all different kind of actuators is used in a widespread range. Their job is to transmit force, bear load, produce linear force, adjust height etc. Hydraulic fluid pressure, pneumatic pressure and electrical current usually change in to some sort of motion in actuators. This report is related to electrical actuators and self-locking problem, which is really common in them. The thesis report has been performed at Reac AB in Åmål, Sweden, a major supplier of wheel chair actuators. Electrical actuators have vast usage and they are versatile but in some cases they face with different working situation like dynamic forces. Recent generation of electrical actuators which used in wheelchairs (imagine moving wheelchair in bumpy road) have self-locking problem, which it means that they will lose their position after while under compression load. This fact will lead to de-calibration of the control system. Approximately 90% of AB production is related to the electrical wheelchairs. Challenging point here is dynamic force which can lead to de-calibration of potentiometer and failure of device. Load capacity of certain actuator (RE25) is 2000 N. In this project different method has been used to simulate and calculate different aspects. Design of new part, material selection and improvement of some parts are most important. During the period lots of static and dynamic tests, CAD design and FEM analysis have been executed. Shock absorber, lock pin and new material have been run parallel and more or less all those three had a positive effect. Finally with design and selection of lock pin solution included cogwheel and pin, we overcome to the problem with great results.
21
Lafontaine, Serge R. "Fast shape memory alloy actuators." Thesis, McGill University, 1997. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=34990.
Full textAbstract:
In this thesis techniques for fabricating fast contracting and relaxing shape memory alloy (SMA) fibers are presented. Shape memory alloy fibers have demonstrated the largest stress and highest power to mass ratio of any known actuator technology. However their practical application has been plagued by three major drawbacks, namely: (1) relatively slow expansion of the material despite rapid contraction; (2) problems of mechanically and electrically connecting to the material due to the violent nature of their contractions; and (3) low efficiency in the conversion of electrical energy or heat into mechanical energy. The work associated with this thesis has led to solutions to the first two problems allowing even sub-millisecond contraction-expansion cycle times, and fibers to be attached via light weight but high strength and high conductivity joints. The properties of these fibers are extensively studied. Both linear and rotary actuators are built using these fibers.A new technique is presented to mount nickel-titanium (NiTi) SMA fibers. NiTi alloys are not readily bonded, soldered, brazed or welded to other materials. The new method employs metal deposited on the fiber or between two fibers or between fibers and other parts, creating metallic attachments that are mechanically sound and electrically conductive. Furthermore a new process for the three-dimensional microfabrication by localized electrodeposition and etching has also been developed. This latter process, combined with the first process, can be used to integrate NiTi alloys in micro-mechanisms. The good electrical contacts as well as mechanical contact provided by the new attachment mechanisms are important, since they allow the rapid methods to be employed.
Several apparatus were built to study the response of NiTi fibers, in particular to very fast current pulses. Experimental results were obtained to describe the response of the fibers, such as their speed, hysteresis, stiffness and resistivity, and show how these variables change dynamically as a function of time, temperature and stress. Other measurements important for the design of new actuators were done, such as those of efficiency when fast actuation with large current pulses is used.
In the third part of the thesis a novel application for fast fiber actuators is presented in the form of a fast rotary motor for in-the-wheel car rotary motors.
22
Futrzynski, Romain. "Drag reduction using plasma actuators." Licentiate thesis, KTH, Farkost och flyg, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-161409.
Full textAbstract:
This thesis is motivated by the application of active flow control on the cabin of trucks, thereby providing a new means of drag reduction. Particularly, the work presented strives to identify how plasma actuators can be used to reduce the drag caused by the detachment of the flow around the A-pillars. This is achieved by conducting numerical simulations, and is part of a larger project that also includes experimental. The effect of plasma actuators is modeled through a body force, which adds very little computational cost and is suitable for implementation in most CFD solvers. The spatial distribution of this force is described by coefficients which have been optimized against experimental data, and the model was shown to be able to accurately reproduce the wall jet created by a single plasma actuator in a no-flow condition. A half cylinder geometry - a simplified geometry for the A-pillar of a truck - was used in a preliminary Large Eddy Simulation (LES) study that showed that the actuator alone, operated continuously, was not sufficient to achieve a significant reduction of the drag. Nevertheless, a significant drag reduction was obtained by simply increasing the strength of the body force to a higher value, showing that this type of actuation remains relevant for the reduction of drag. In the course of finding ways to improve the efficiency of the actuator, dynamic mode decomposition was investigated as a post-processing tool to extract structures in the flow. Such structures are identified by their spatial location and frequency, and might help to understand how the actuator should be used to maximize drag reduction. Thus a parallel code for dynamic mode decomposition was developed in order to facilitate the treatment of the large amounts of data obtained by LES. This code and LES itself were thereafter evaluated in the case of a pulsating channel flow. By using the dynamic mode decomposition it was possible to accurately extract oscillating profiles at the forcing frequency, although harmonics with lower amplitude compared to the turbulence intensity could not be obtained.Denna avhandling behandlar tillämpningen av aktiv strömningskontroll för lastbilshytter, vilket är en ny metod för minskning av luftmotståndet. Mer i detalj är det övergripande målet att visa på hur plasmaaktuatorer kan användas för att minska luftmotståndet orsakat av avlösningen runt A-stolparna. In denna avhandling studeras detta genom numeriska simuleringar. Arbetet är en del av ett projekt där även experimentella försök görs. Effekten av plasmaaktuatorer modelleras genom en masskraft, vilket inte ger nämnvärd ökning av beräkningstiden och är lämplig för implementering i de flesta CFD-lösare. Den rumsliga fördelningen av kraften bestäms av koefficienter vilka i detta arbete beräknades utifrån experimentella data. Modellen har visat sig kunna återskapa en stråle nära väggen med god noggrannhet av en enskild plasmaaktuator för en halvcylinder utan strömning. Samma geometri - en halvcylinder som här används som förenklad geometri av A-stolpen på en lastbil - användes i en preliminär LES studie som visade att enbart aktuatorn vid kontinuerlig drift inte var tillräckligt för att uppnå en signifikant minskning av luftmotståndet. En signifikant minskning av luftmotståndet erhölls genom att helt enkelt öka styrkan på kraften, vilket visats att denna typ av strömningskontroll är relevant för minskning av luftmotståndet. I syfte att förbättra effektiviteten hos aktuatorn, studerades dynamic mode decomposition, som ett verktyg för efterbehandling för att få fram flödesstrukturer. Dessa strukturer identifieras genom deras rumsupplösning och frekvens och kan hjälpa till att förstå hur aktuatorerna bör användas för att minska luftmotståndet. En parallelliserad kod för dynamic mode decomposition utvecklades för att underlätta efterbehandlingen av de stora datamängder som fås från LES-beräkningarna. Slutligen, utvärderades denna kod och LES-beräkningar på ett strömningsfall med pulserande kanalflöde. Metoden, dynamic mode decomposition, visade sig kunna extrahera de oscillerande flödesprofilerna med hög noggrannhet för den påtvingade frekvensen. Övertoner med lägre amplitud jämfört med turbulensintensiteten kunde dock inte erhållas.
QC 20150312
23
Mitwalli, Ahmed Hamdi. "Polymer gel actuators and sensors." Thesis, Massachusetts Institute of Technology, 1998. http://hdl.handle.net/1721.1/9969.
Full textAbstract:
Thesis (Sc. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1998.Includes bibliographical references (p. [351]-361).
by Ahmed Hamdi Mitwalli.
Sc.D.
24
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.
Full textAbstract:
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.
25
Srinivasan, Prasanna. "Materials selection for microsystems actuators." Thesis, University of Southampton, 2008. https://eprints.soton.ac.uk/64892/.
Full textAbstract:
The recent developments of novel thin film materials and their associated processes have marked the onset of change in the design philosophy of Micro-Electro- Mechanical Systems (MEMS) from process centric to performance centric. This presents an opportunity to improve the performance of MEMS devices by materials selection beyond the commonly preferred candidates compatible with the Complimentary-Metal-Oxide-Semiconductor (CMOS) processes which forms the principal motivation of the present research. This thesis focuses on the selection of suitable materials choices for realising high performance MEMS actuators. The thermomechanical design for a generic cantilever bi-layered structure was evolved using a temperature dependent quasi-static analysis. The closed form solutions for mechanical performances (displacement/tip slope, blocked force/moment, work per unit volume) were obtained applying Timoshenko bimetallic theory for an Euler- Bernoulli beam subjected to electrothermal, piezoelectric and shape memory actuations. The thermal performance (actuation frequency) was evaluated using lumped heat capacity models. Contours of equal performance were plotted in the domain of governing material properties on Ashby’s selection maps to identify and rank promising candidates for further analysis. A few novel material combinations such as Zn and Ni on Si and Diamond-like-carbon (DLC) substrates perform better than conventional material combination (Al on Si) for high work per volume bimaterial electrothermal actuators. Actuation frequencies of the order of ~10 kHz can be achieved electrothermally at scales less than 100 μm using engineering alloys. Although engineering polymers on Si are promising for high displacement electrothermal actuators, their low elastic moduli have to be compensated by a large thickness for an optimal performance. Pb based piezoceramics on Si/DLC substrates are promising for high force piezoelectric MEMS actuators. Piezoelectric actuators operate at mechanical resonance (> 100 kHz) and hence the achievable frequencies are greater than that of the electrothermal actuators. However, the work per unit volume delivered is lower than that of the electrothermal actuators. Nitinol (NiTi shape memory alloy) on Si/DLC are promising material combination for high work per volume actuation at a few hundred Hz. Actuation achieved by electrothermal buckling of a fixed-fixed structure was found to be superior to the bimaterial flexural ii actuators in delivering a large work per volume. A detailed comparison of the maximum achievable performance for different actuation schemes was made to facilitate the selection of actuators and the associated material choices for any application. The suitability of Al-Si bimaterial electrothermal actuators for low speed distributed flow control applications was assessed by comparing their performance with the more obviously suitable Si-PZT bimaterial piezoelectric actuators. A detailed processing route for microfabricating Al-Si3N4 bimaterial electrothermal actuators was developed and the associated micromachining issues were discussed. The experimental evaluation of the mechanical and thermal performance metrics of the microfabricated structures is expected to be accomplished in the future, for comparison with the analytical estimates and for subsequent validation by finite element analysis. The general framework of the materials selection strategy and the ranking of the potential candidates presented here will form a basis for the rational design of the MEMS actuators with an improved performance. The outcomes of this thesis also have set up an agenda for long term research goals which include exploration of novel actuator shapes/schemes, understanding of the process-property relations to tailor thin film properties and a comprehensive assessment of other novel substrate materials and their processes for MEMS actuator structures.
26
Jilani, Adel Benhaj. "Deformations of Piezoceramic-Composite Actuators." Diss., Virginia Tech, 1999. http://hdl.handle.net/10919/29540.
Full textAbstract:
In the past few years a new class of layered piezoceramic and piezoceramic-composite actuators, known as RAINBOW and GRAPHBOW, respectively, that are capable of achieving 100 times greater out-of-plane displacements than previously available has been developed. Prior to the development of RAINBOW and GRAPHBOW, large stacks of piezoelectric actuators, requiring complicated electronic drive circuits, were necessary to achieve the displacement now possible through the use of a single RAINBOW actuator. The major issues with both RAINBOW and GRAPHBOW are the prediction of their room-temperature shapes after processing, and their deformation response under application of electric field.
In this research, a methodology for predicting the manufactured shapes of rectangular and disk-style RAINBOW and GRAPHBOW is developed. All of the predictive analyses developed are based on finding approximate displacement responses that minimize the total potential energy of the devices through the use of variational methods and the Rayleigh-Ritz technique. These analyses are based on classical layered plate theory and assumed the various layers exhibited linear elastic, temperature-independent behavior. Geometric nonlinearities are important and are included in the strain-displacement relations. Stability of the predicted shapes is determined by examining the second variation of the total potential energy. These models are easily modified to account for the deformations induced by actuation of the piezoceramic.
The results indicate that for a given set of material properties, rectangular RAINBOW can have critical values of sidelength-to-thickness ratio (Lx/H or Ly/H) below which RAINBOW exhibits unique, or single-valued, spherical or domed shapes when cooled from the processing temperature to room temperature. For values of sidelength-to-thickness ratio greater than the critical value, RAINBOW exhibits multiple room-temperature shapes. Two of the shapes are stable and are, in general, near-cylindrical. The third shape is spherical and is unstable. Similarly, disk-style RAINBOW can have critical values of radius-to-thickness ratios (R/H) below which RAINBOW exhibits axisymmetric room-temperature shapes. For values of R/H greater than the critical value, disk-style RAINBOW exhibits two stable near-cylindrical shapes and one unstable axisymmetric shape. Moreover, it is found that for the set of material properties used in this study, the optimal reduced layer thickness would be at 55%, since the maximum change in curvature is achieved under the application of an electric field, while the relationship between the change in curvatures and the electric field is kept very close to being linear. In general, good agreement is found for comparisons between the predicted and manufactured shapes of RAINBOW. A multi-step thermoelastic analysis is developed to model the addition of the fiber-reinforced composite layer to RAINBOW to make GRAPHBOW. Results obtained for rectangular RAINBOW indicate that if the bifurcation temperature in the temperature-curvature relation is lower than the composite cure temperature, then a unique stable GRAPHBOW shape can be obtained. If the RAINBOW bifurcation temperature is above the composite cure temperature, multiple room-temperature GRAPHBOW shapes are obtained and saddle-node bifurcations can be encountered during the cooling to room temperature of [0°/RAINBOW], [RAINBOW/0o], and [0o2/RAINBOW]. Rectangular [RAINBOW/0o/90o] seems to be less likely to encounter saddle-node bifurcations. Furthermore, the unstable spherical RAINBOW configuration is converted to a stable near-cylindrical configuration. For the case considered of disk-style GRAPHBOW, three stable room-temperature shapes are obtained and the unstable axisymmetric RAINBOW configuration is also converted to a stable near-cylindrical configuration. For both rectangular and disk-style GRAPHBOW, the relationship between the major curvature and the electric field is shown to be very close to being linear. This characteristic would aid any dynamic analysis of RAINBOW or GRAPHBOW.Ph. D.
27
Asveld, Jip. "Actuators as a Design Material." Thesis, Malmö universitet, Fakulteten för kultur och samhälle (KS), 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:mau:diva-22860.
Full textAbstract:
This thesis is an explorative, design-based research study towards the expressive potential of using actuators as design materials. Over three distinct phases of experimentation –all with their own particular aim– various sketches are developed that showcase different expressive qualities. These sketches consist of a variety of kitchen devices that are expanded with actuators. These actuators do not necessarily add to the functionality of the device, but rather to its expressiveness. The development of and reasoning for the sketches is clarified in an extensive way to clearly present all the insights that are gained throughout the design process. In the end, the sketches are discussed and reflected upon on the basis of the process-insights and relevant design theories.
28
Bocchieri, Guido <1993>. "Optimal design of compliant actuators." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2021. http://amsdottorato.unibo.it/9790/1/Bocchieri_Guido_tesi.pdf.
Full textAbstract:
Compliant actuators are mechanical devices that extend the traditional architecture of robotic joints (motor – transmission – load) by introducing in the power transmission chain some degree of compliance, in the form of off-the-shelf springs or elastic and deformable components. Depending on where and how these compliant elements are inserted in the transmission, many different architectures of compliant actuators arise. The objective of this work is to analyze these different architectures from a theoretical point of view, derive new optimal design techniques and methodologies and, finally, apply these techniques to design new prototypes of robotic actuators devoted to specific applications.
29
Colonnelli, Stefania. "Instability of Dielectric Elastomer Actuators." Doctoral thesis, Università degli studi di Trento, 2012. https://hdl.handle.net/11572/368067.
Full textAbstract:
Dielectric elastomers (DEs) are an important class of materials, currently employed in the design and realization of electrically-driven, highly deformable actuators and devices, which find application in several fields of technology and engineering, including aerospace, biomedical and mechanical engineering. Subject to a voltage, a membrane of a soft dielectric elastomer coated by compliant electrodes reduces its thickness and expands its area, possibly deforming in-plane well beyond 100%: this principle is exploited to conceive transducers for a broad range of applications, including soft robots, adaptive optics, Braille displays and energy harvesters. Soft dielectrics undergo finite strains, and their modelling requires a formulation based on the Mechanics of Solids at large deformations. A major problem that limits the widespread diffusion of such devices in everyday technology is the high voltage required to activate large strains, because of the low dielectric permittivity of typical materials (acrylic elastomers or silicones), in the order of few unities, which governs the electromechanical coupling.
Composite materials (reinforcing a soft matrix with stiff and high-permittivity particles) provide a way to overcome these limitations, as suggested by some experiments. In addition, composites can display failure modes and instabilities not displayed by homogeneous specimens that must be thoroughly investigated. Commonly, instability phenomena are seen as a serious drawback, that should be predicted and avoided. However, in some cases they can be used to activate snap-through actuation, as in the case of buckling-like or highly-deformable balloon-like actuators.
Soft dielectric elastomers display electrostrictive properties (permittivity depending on the deformation) and we show how to take into account such a phenomenon within the theory of electroelasticity. Original results regard the investigation of diffuse modes (buckling like instabilities etc.), surface mode instabilities and localized modes. New (analytical) solutions for band-localization instability are provided and then it has been investigated how such instabilities are related to electrostriction. Regarding DE composites, the goal is to evaluate in detail the behaviour of two-phase rank-1 laminates in terms of different types of actuation, geometric and mechanical properties of phases, applied boundary conditions, and instabilities phenomena, in order to establish precise ranges in which the performance enhancement is effective with respect to the homogeneous counterpart.
30
Colonnelli, Stefania. "Instability of Dielectric Elastomer Actuators." Doctoral thesis, University of Trento, 2012. http://eprints-phd.biblio.unitn.it/710/1/PhD_thesis_Stefania_Colonnelli.pdf.
Full textAbstract:
Dielectric elastomers (DEs) are an important class of materials, currently employed in the design and realization of electrically-driven, highly deformable actuators and devices, which find application in several fields of technology and engineering, including aerospace, biomedical and mechanical engineering. Subject to a voltage, a membrane of a soft dielectric elastomer coated by compliant electrodes reduces its thickness and expands its area, possibly deforming in-plane well beyond 100%: this principle is exploited to conceive transducers for a broad range of applications, including soft robots, adaptive optics, Braille displays and energy harvesters. Soft dielectrics undergo finite strains, and their modelling requires a formulation based on the Mechanics of Solids at large deformations. A major problem that limits the widespread diffusion of such devices in everyday technology is the high voltage required to activate large strains, because of the low dielectric permittivity of typical materials (acrylic elastomers or silicones), in the order of few unities, which governs the electromechanical coupling.
Composite materials (reinforcing a soft matrix with stiff and high-permittivity particles) provide a way to overcome these limitations, as suggested by some experiments. In addition, composites can display failure modes and instabilities not displayed by homogeneous specimens that must be thoroughly investigated. Commonly, instability phenomena are seen as a serious drawback, that should be predicted and avoided. However, in some cases they can be used to activate snap-through actuation, as in the case of buckling-like or highly-deformable balloon-like actuators.
Soft dielectric elastomers display electrostrictive properties (permittivity depending on the deformation) and we show how to take into account such a phenomenon within the theory of electroelasticity. Original results regard the investigation of diffuse modes (buckling like instabilities etc.), surface mode instabilities and localized modes. New (analytical) solutions for band-localization instability are provided and then it has been investigated how such instabilities are related to electrostriction. Regarding DE composites, the goal is to evaluate in detail the behaviour of two-phase rank-1 laminates in terms of different types of actuation, geometric and mechanical properties of phases, applied boundary conditions, and instabilities phenomena, in order to establish precise ranges in which the performance enhancement is effective with respect to the homogeneous counterpart.
31
Son, Hungsun. "Effects of magnetic field models on control of electromagnetic actuators." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/26616.
Full textAbstract:
Thesis (Ph.D)--Mechanical Engineering, Georgia Institute of Technology, 2008.Committee Chair: Lee, Kok-Meng; Committee Member: Bill Singhose; Committee Member: David G. Taylor; Committee Member: Eric Johnson; Committee Member: Nader Sadegh. Part of the SMARTech Electronic Thesis and Dissertation Collection.
32
Davis, Steven T. "Braided pneumatic muscle actuators : enhanced modelling and performance in integrated, redundant and self healing actuators." Thesis, University of Salford, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.419130.
Full text
33
Warta, Brett James. "Characterization of High Momentum Flux Combustion Powered Fluidic Actuators for High Speed Flow Control." Thesis, Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/19873.
Full textAbstract:
The performance of a high-power small-scale combustion-based fluidic actuator for high-speed flow control applications is characterized with specific focus on comparisons between premixed and nonpremixed operating modes for the device. Momentary (pulsed) actuation jets are produced by the ignition of a mixture of gaseous fuel and oxidizer within a small (cubic centimeter scale) combustion chamber. The combustion process yields a high pressure burst (1 to 3 ms in duration in the typical configurations) and the ejection of a high-speed exhaust jet. The actuation frequency can be continuously varied by independently controlling the flow rate of the fuel/oxidizer and the spark ignition frequency up to a maximum determined by the operating characteristics of the actuator. The actuator performance is characterized by both its peak thrust and net total impulse, with increases in peak jet momentum often two to three orders of magnitude above the baseline steady jet. Results for operation of the device in both premixed and nonpremixed modes are presented and analyzed, with nonpremixed operation typically yielding higher pressures and greater frequency ranges in the present configurations.
34
Höijertz, Erik. "Supercoiled Actuators with Liquid Metal Joule Heating : novel miniaturized actuators for pneumatic control of reconfigurable wearables." Thesis, Uppsala universitet, Mikrosystemteknik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-426008.
Full textAbstract:
Garments serve a number of purposes, from protection and physiological comfort to social and cultural expressions. With the recent developments of active textiles, sensors and actuators with shapes and sizes similar to textiles, the real multifunctional garments have been realized. The functions of such garments can be regulating heat by changing the spacing between the strands of yarn, giving massage or assisting lifting movement by expanding and contracting one or more actuators. This project is a part of a main project targeting on reconfigurable hybrid wearables. The main started from studying possible actuators that could have textile-like properties, where pneumatic actuators were chosen. A model of different forces, strains and braiding angles of a pneumatic actuator sometimes called a McKibben muscle was made. It should be noted that such garments with pneumatic actuators to be functional and applicable each segment needed an external pump. For local actuation, miniaturized servo valves were needed. Hence, study on super coiled actuators (SCAs) was initiated to investigate their potential of controlling the valves for constricting the flow when needed. In this project different SCAs were developed and their performances were recorded. To assist with heating of the SCAs Galinstan and Gallium were used as electric resistors to provide for Joule heating. A contraction of over 19% and an efficiency of 0.29% were achieved but could most likely be improved by optimizing the fabrication and testing process.
35
Paoletta, Giovanni. "Electroactive soft actuators: Modelling and control." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2020. http://amslaurea.unibo.it/20189/.
Full textAbstract:
The work done in this master thesis is part of the European project MAGNIFY (1) at the University of Groningen, the Netherlands."MAGNIFY aims to develop a new generation of artificial muscles for robotic systems. The artificial muscle will be realized by using artificial molecular machines, organized in polymer nanofibers and individually controlled by external stimuli''(2)
This thesis focuses on a similar polymer that will be used in the project MAGNIFY. The work presents the analysis and utilization of an electroactive soft actuator, made of polyurethane-based nanofibers. A mat of aligned nanofibers of polyurethane and salt has been fabricated through an electrospinning process and, subsequently, has been rolled up to form a bundle of aligned nanofibers.
Several electromechanical tests have been performed on the bundle, applying a certain voltage and evaluating the force and the displacement generated by the soft actuator. The sampled data of voltage, force, and displacement are then used to identify the nonlinear model of Voltage-Force and Voltage-Displacement link. The second part of this thesis aims to use the model estimated Voltage-Displacement to build a PID controller for position control. It has been shown a possible future application for the soft actuator as a robotic arm. To conclude, an energy analysis has been performed, to compare the energy consumption of the soft-actuator and of an electric linear motor, considering similar maximum output force.
(1)This project has received funding from the European Union’s Horizon 2020 Research and Innovation Programme under Grant Agreement no. 801378.
(2)https://www.magnifyproject.eu/project-overview
36
Gomis-Bellmunt, Oriol. "Identification and control of piezoelectric actuators." Saarbrücken VDM Verlag Dr. Müller, 2007. http://d-nb.info/988454696/04.
Full text
37
Edqvist, Erik. "Polymer Actuators for Micro Robotic Applications." Licentiate thesis, Uppsala University, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-88981.
Full textAbstract:
In this thesis a multilayer actuator structure is developed for the I-SWARM project. In order to build an energy efficient and low voltage actuator system for the 3x3x3 mm3 robot, the resonance drive mode in combination with a ten layer multilayer structure build upon the most suitable substrate material was used. Two different sizes of the locomotion module were built. The first one is five times larger than the small version. It has five active layers and is simpler to work with and to test. The small module has three 2x0.4 mm can-tilevers on a 3x3mm body and ten active layers.
The multilayer process involve easily defined flexible printed circuit (FPC) board as substrate material, spin coating piezoelectric poly(vinylidenefluoride- tetrafluoroethylene) P(VDF-TrFE) as active stack material, and evaporated aluminum electrodes on each active polymer layer. By using different shadow masks for each electrode layer, special inter con-tact areas can be contacted from above after the polymer has been removed by an Inductively Coupled Plasma (ICP) etch. The contours of the locomo-tion module was etched in a Reactive Ion Etch (RIE) equipment. Both the cupper layer in the FPC and the electrode layers of the active stack, were used as etch mask.
The deflections of the cantilevers were measured at low voltages to ensure as realistic drive voltage as possible for the I-SWARM robot. The large struc-ture showed a 250 µm deflection at 4 V and 170 Hz resulting in a Q-value of 19. The deflection of the small structure was 8 µm at 3.3 V and 5000 Hz and the measured Q-value was 31.
38
Parashar, Sandeep Kumar. "Shear induced vibrations in piezoceramic actuators." Herdecke GCA-Verl, 2005. http://deposit.ddb.de/cgi-bin/dokserv?id=2760960&prov=M&dok_var=1&dok_ext=htm.
Full text
39
Riddar, Frida. "Tribological Aspects of Pneumatic Clutch Actuators." Doctoral thesis, Uppsala universitet, Tillämpad materialvetenskap, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-195330.
Full textAbstract:
A clutch actuator is used in a vehicle to transmit movement and force from the clutch pedal to the release bearing of the clutch. A pneumatic clutch actuator consists of an anodised aluminium cylinder, inside of which a piston, with a rubber lip seal and a PTFE guiding ring, slides. The system is lubricated with silicone grease before assembly. A commercial clutch actuator of this type, has a service life of 3 million actuations and must function in a wide temperature range, from -40 ºC to 140 ºC. In this thesis, the complex tribological system of pneumatic clutch actuators has been studied. Field worn actuators have been disassembled and investigated. A laboratory test method has been developed to understand the tribomechanisms present in pneumatic clutch actuators. The test method's capability of simulating the real contact has been verified, by the comparison with studied actuators from the field. The influence of contact parameters: temperature, load, lubrication and particle contamination, has been investigated. In addition, different anodised aluminium surfaces have been studied. The manufacturing method of the aluminium cylinder influences surface topography and structure of the oxide, resulting in different mechanical and frictional properties. The wear during tests with only silicone grease is reminiscent, but on a lower scale, to the wear during tests with a mixture of silicone grease and standard dust. The initially applied amount of silicone grease is not important, the friction seems to depend on the amount of silicone grease that is dragged into or pushed out from the contact area during testing. Silicone grease lubrication reduces wear of the lip seal. However, during some tests, an adhesive layer, composed of grease residuals and some PTFE, was formed on the lip. A triple PTFE transfer, from guiding ring to aluminium surface, to lip seal, to aluminium surface, occurred. Such transfer of material from the PTFE guiding ring was detected from the unlubricated tests, and also from the silicone grease lubricated tests, i.e. silicone grease lubrication does not prevent PTFE material transfer.
40
Nishimoto, Michael Yoshiya. "Thermal processing of multilayer PLZT actuators." Thesis, Georgia Institute of Technology, 1999. http://hdl.handle.net/1853/19637.
Full text
41
Bennett, John William. "Fault tolerant electromechanical actuators for aircraft." Thesis, University of Newcastle Upon Tyne, 2010. http://hdl.handle.net/10443/990.
Full textAbstract:
This thesis reviews the developments in commercial aviation resulting from More Electric Aircraft initiatives. The present level of electromechanical actuation is considered with discussion of the factors affecting more widespread use. Two rather different electromechanical actuators are presented for commercial aircraft; DEAWS electrical flap actuation and ELGEAR nose wheel steering. Both projects are industrially driven with specifications based on existing medium-sized commercial aircraft. Methods comparing fault tolerant electric drive topologies for electrical actuators are presented, showing two different categories of electric drive and comparing each category in a variety of operating conditions to assess size and component count. The safety-driven design process for electromechanical actuators is discussed with reliability calculations presented for both proposed actuators, showing where fault tolerant design is required to meet safety requirements. The selection of an optimum fault tolerant electric drive for each actuator is discussed and fault tolerant control schemes are presented. The development of the electric flap and nose wheel steering systems is described, with the focus on the work performed by the author, primarily on the power electronic converters and control software. A comprehensive range of laboratory and industrial results are given for both actuators, showing demonstrations of fault tolerance at power converter and actuator levels. Following testing, further analysis is given on various issues arising prior and during testing of both converters, with design considerations for future electromechanical actuators. From design testing and analysis, the two projects can be compared to attempt to determine the optimal electromechanical actuator topology and to consider the challenges in evolving the two actuators to aerospace products.
42
Ismail, Ziad M. A. "Microprocessor control of electro-mechanical actuators." Thesis, Loughborough University, 1986. https://dspace.lboro.ac.uk/2134/11785.
Full textAbstract:
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.
43
Zhang, Wei. "MODELING AND CONTROL OF MAGNETOSTRICTIVE ACTUATORS." UKnowledge, 2005. http://uknowledge.uky.edu/gradschool_theses/257.
Full textAbstract:
Most smart actuators exhibit rate-dependant hysteresis when the working frequency is higher than 5Hz. Although the Preisach model has been a very powerful tool to model the static hysteresis, it cannot be directly used to model the dynamic hysteresis. Some researchers have proposed various generalizations of the Preisach operator to model the rate-dependant hysteresis, however, most of them are application-dependant and only valid for low frequency range. In this thesis, a first-order dynamic relay operator is proposed. It is then used to build a novel dynamic Preisach model. It can be used to model general dynamic hysteresis and is valid for a large frequency range. Real experiment data of magnetostrictive actuator is used to test the proposed model. Experiments have shown that the proposed model can predict all the static major and minor loops very well and at the same time give an accurate prediction for the dynamic hysteresis loops. The controller design using the proposed model is also studied. An inversion algorithm is developed and a PID controller with inverse hysteresis compensation is proposed and tested through simulations. The results show that the PID controller with inverse compensation is good at regulating control; its tracking performance is really limited (average error is 10 micron), especially for high frequency signals. Hence, a simplified predictive control scheme is developed to improve the tracking performance. It is proved through experiments that the proposed predictive controller can reduce the average tracking error to 2 micron while preserve a good regulating performance.
44
Widdowson, G. P. "Design optimization of permanent magnet actuators." Thesis, University of Sheffield, 1992. http://etheses.whiterose.ac.uk/1849/.
Full textAbstract:
This study describes the design optimization of permanent actuators, of both rotary and linear topologies. Parameter scanning, constrained single and multi-criterion optimization techniques are developed, with due emphasis on the efficient determination of optimal designs. The modelling of devices by non-linear lumped reluctance networks is considered, with particular regard to the level of discretization required to produce accurate global quantities. The accuracy of the lumped reluctance technique is assessed by comparison with non-linear finite element analysis. Alternative methods of force/torque calculation are investigated, e.g. Lorentz equation, Virtual Work, and Maxwell Stress Integration techniques, in order to determine an appropriate technique for incorporation in a non-linear iterative optimization strategy. The application of constrained optimization in a design environment is demonstrated by design studies and experimental validation on selected prototype devices of both topologies.
45
Zhou, Hui M. S. Massachusetts Institute of Technology. "Micromechanical actuators for insect flight mechanics." Thesis, Massachusetts Institute of Technology, 2008. http://hdl.handle.net/1721.1/44319.
Full textAbstract:
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2008.Includes bibliographical references (p. 95-97).
This project aims to develop MEMS actuators to aid in the study of insect flight mechanics. Specifically, we are developing actuators that can stimulate the antennae of the crepuscular hawk moth Manduca Sexta. The possible mechanosensory function of antennae as airflow sensors has been suggested, and recent discoveries of our collaborators reveal that mechanosensory input from the antennae of flying moths serves a similar role to that of the hind wings of two-winged insects, detecting Coriolis forces and thereby mediating flight stability during maneuvers. Early evidence suggests that mechanical stimulus of the antennae may enable flight control. In addition, the crepuscular hawk moth Manduca Sexta has a wide wingspan (~110 mm) and is capable of carrying at least one quarter of its own weight. Thus, studying the flight of Manduca Sexta by attachment of microsystems seems plausible. The goal of our project is to design and fabricate micromechanical actuators, which will be mounted onto the moth antennae. Our collaborators will study the flight control mechanism by mechanical stimulation. Our first step was to fabricate "dummy" silicon rings for our biologist collaborators for implant experiment. A series of mounting kits were developed, and due to the nature of the moth antennae, ring-beam-ring construction was finally designed and fabricated, like a "shackle", to meet the mounting requirements. Next, we integrated actuators onto the mounting kit. Piezoelectric film/sheet, piezoelectricbender and piezoelectric-stack were considered as the actuators. Live testing was also taken while the moth was resting or flapping its wings. The moth apparently responds to the mechanical stimulus under both circumstances, by swinging its wings and abdomen. Actuation amplifier was also modeled and tested, which might be used for future mechanical stimulators.
by Hui Zhou.
S.M.
46
Spangler, Ronald L. 1964. "Piezoelectric actuators for helicopter rotor control." Thesis, Massachusetts Institute of Technology, 1989. http://hdl.handle.net/1721.1/14462.
Full text
47
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.
Full textAbstract:
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.
48
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.
Full textAbstract:
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.
49
Scheidl, Rudolf. "Actuators and Sensors for Smart Systems." Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-200616.
Full textAbstract:
Smartness of technical systems relies also on appropriate actuators and sensors. Different to the prevalent definition of smartness to be embedded machine intelligence, in this paper elegance and simplicity of solutions is postulated be a more uniform and useful characterization. This is discussed in view of the current trends towards cyber physical systems and the role of components and subsystems, as well as of models for their effective realization. Current research on actuators and sensing in the fluid power area has some emphasis on simplicity and elegance of solution concepts and sophisticated modeling. This is demonstrated by examples from sensorless positioning, valve actuation, and compact hydraulic power supply.
50
Ekman, Fredrik. "Development and Evaluation of Textile Actuators." Thesis, Linköpings universitet, Biosensorer och bioelektronik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-130532.
Full textAbstract:
Existing actuators in robotics are noisy, rigid and not very lifelike in their movements. There is a need for actuators in especially limb prosthetics and exoskeletons that are silent, softly moving and preferably operating on low currents. One such solution is the conducting polymers. Textiles are well researched and there is a wide variety of patterning. Even more important is their reproducibility and how easily they are mass-produced. This thesis work combines conducting polymers with textiles to achieve linear textile actuators. The textiles are coated with the conducting polymer Polypyrrole which has the property of volume change, when a voltage is applied and there is a reservoir of ions accessible. The volume change, expansion and contraction, results in a linear actuation. The force and strain are measured while changing different parameters and the results are evaluated in this thesis.