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1
MacNair, David Luke. "Modeling cellular actuator arrays." Diss., Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/50259.
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This work explores the representations and mathematical modeling of biologically-inspired robotic muscles called Cellular Actuator Arrays. These actuator arrays are made of many small interconnected actuation units which work together to provide force, displacement, robustness and other properties beyond the original actuator's capability. The arrays can also exhibit properties generally associated with biological muscle and can thus provide test bed for research into the interrelated nature of the nervous system and muscles, kinematics/dynamics experiments to understand balance and synergies, and building full-strength, safe muscles for prosthesis, rehabilitation, human force amplification, and humanoid robotics.
This thesis focuses on the mathematical tools needed bridge the gap between the conceptual idea of the cellular actuator array and the engineering design processes needed to build physical robotic muscles. The work explores the representation and notation needed to express complex actuator array typologies, the mathematical modeling needed to represent the complex dynamics of the arrays, and properties to guide the selection of arrays for engineering purposes. The approach is designed to aid automation and simulation of actuator arrays and provide an intuitive base for future controls and physiology work. The work is validated through numerical results using MatLab's SimMechanics dynamic modeling system and with three physical actuator arrays built using solenoids and shape memory alloy actuators.
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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/.
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Dissertation (Ph.D.)--Worcester Polytechnic Institute.Keywords: hybrid system, PZT actuators, performance enchancement, actuator placement, actuator switching. Includes bibliographical references (leaves 102-108).
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Bahrami, Sanaz. "Low-Profile Polymer Actuator Fabrication for Spastic Hand Exoskeletons." Thesis, Université d'Ottawa / University of Ottawa, 2018. http://hdl.handle.net/10393/37953.
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Spasticity is a neurological impairment that presents itself in the form of a continuous muscle contraction, with the key motor deficit being impaired hand function. Hand exoskeleton technologies play a vital role in the therapeutic rehabilitation of this condition. The optimal design of these devices is currently a challenge due to the limited availability of actuation devices that are light weight, portable, and aesthetically pleasing. Natural muscles have many favourable characteristics, such as their high power-to-weight ratio, efficient energy conversion, and fast actuation times. Unfortunately, traditional systems such as pneumatics muscles and electromagnetic motors have yet to attain similar properties. These traditional actuators exhibit hysteretic performance, high manufacturing cost, low stroke, and limited cycle life. In recent years a new category of actuators has been developed from highly twisted and coiled low-cost nylon fibres such as fishing line and conductive sewing thread. These muscles produce a high specific work per cycle with a reversible contraction. This thesis develops and tests these twisted and coiled polymer (TCP) actuators using various nylon and polyethylene polymers in order to establish a foundation for their implementation as a novel actuation device in a spastic hand exoskeleton. An initial comprehensive experimental evaluation of several nylon fibres is completed by attempting to reproduce the work of previous researchers. Subsequently, the information obtained is taken and adapted to the development of UHMWPE TCPs and other types of nylon monofilament. This thesis characterizes the contractility and force output of these novel actuation devices.
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Du, Xinli. "High redundancy actuator." Thesis, Loughborough University, 2008. https://dspace.lboro.ac.uk/2134/12232.
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High Redundancy Actuation (HRA) is a novel type of fault tolerant actuator. By comprising a relatively large number of actuation elements, faults in the elements can be inherently accommodated without resulting in a failure of the complete actuation system. By removing the possibility of faults detection and reconfiguration, HRA can provide high reliability and availability. The idea is motivated by the composition of human musculature. Our musculature can sustain damage and still function, sometimes with reduced performance, and even complete loss of a muscle group can be accommodated through kinematics redundancy, e.g. the use of just one leg. Electro-mechanical actuation is used as single element inside HRA. This thesis is started with modelling and simulation of individual actuation element and two basic structures to connect elements, in series and in parallel. A relatively simple HRA is then modelled which engages a two-by-two series-in-parallel configuration. Based on this HRA, position feedback controllers are designed using both classical and optimal algorithms under two control structures. All controllers are tested under both healthy and faults injected situations. Finally, a hardware demonstrator is set up based simulation studies. The demonstrator is controlled in real time using an xPC Target system. Experimental results show that the HRA can continuously work when one element fails, although performance degradation can be expected.
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Vandehey, N. T., and J. P. O\'Neil. "Automated stopcock actuator." Helmholtz-Zentrum Dresden - Rossendorf, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:d120-qucosa-166258.
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Introduction
We have developed a low-cost stopcock valve actuator for radiochemistry automation built using a stepper motor and an Arduino, an open-source single-board microcontroller. The con-troller hardware can be programmed to run by serial communication or via two 5–24 V digital lines for simple integration into any automation control system. This valve actuator allows for automated use of a single, disposable stopcock, providing a number of advantages over stopcock manifold systems available on many commercial radiochemistry rigs or over using solenoid valves. This actuator allows for the use a wide variety of stopcocks, ranging in size, shape and material, giving flexibility to be used in a large variety of applications.
Material and Methods
The actuated valve consists of two main parts, the actuator and the control electronics. The actuator consists of a stepper motor, an infrared ‘home position’ sensor, a stopcock backplate, and a coupler from the driveshaft to stopcock handle. The stepper motor is a NEMA-17 size that runs 200 steps/rotation with a 5mm drive shaft. The coupler is an interchangeable part, custom to each stopcock model, with each part drilled out to fit the motor drive shaft and milled out for a tight fit to the stopcock handle. The backplane consists of a plate offset from the motor body with 5 screws positioned to keep the stopcock body from rotating relative to the motor. A reflective optical sensor (Vishay TCRT1000) is used as a limit switch to determine a ‘home’ position for the stopcock. With a slight modification to most any stopcock in cutting off a tab that limits rotation, the handle can rotate 360°. This allows for opening all three ports to each other, which has been done to all stopcocks used with this actuator.
The control electronics consist of an Arduino Uno board and a motor shield (add-on board), connecting to the actuator by an Ethernet cable. The motor shield functions to interface the low-power Arduino circuitry with a high power H-bridge motor driver circuit. The Arduino runs two sets of code, initialization and its loop. The initialization routine runs when power is first powered up, and then continues to run the loop. The initialization routine rotates the valve until the IR limit switch is activated, and rotates an-other 45° from position home, sealing off all ports on the stopcock. Following initialization, the Arduino enters its loop, which repeatedly compares its current position to its target posi-tion. When the target position and current posi-tion do not match, the stepper motor turns in the shortest direction towards its target position. The hardware can be interfaced by either serial communication or by two 5–24V digital signals defining positions 1–4. The wide range of allowed input signal voltages is realized by using an optocoupler that accepts 5–24 V inputs but outputs TTL signals compatible with the Arduino’s hardware.
Results and Conclusion
A photo of the implementation of the actuator is shown in FIGURE 1. It has overall dimensions of 3.5×1.75×2.5”, excluding a mounting bracket. Control electronics are housed in a compact box built for an Arduino, giving the control electron-ics a clean, professional look. Challenges in de-sign included determining a maximum motor speed where the motor would provide enough torque but yet move fast enough to be useful, finding that rotational speed of 6 seconds/full rotation is best.
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Braff, Rebecca A. (Rebecca Alice). "Microbubble cell actuator." Thesis, Massachusetts Institute of Technology, 1999. http://hdl.handle.net/1721.1/38276.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1999.Includes bibliographical references (p. 91-92).
The field of microsystems technology is rapidly growing, and expanding its horizons to applications in bioengineering. Currently, there are no cell analysis systems that facilitate the collection of dynamic responses for a large number of cells, and sorting based on those results. A cell chip has been fabricated in pursuit of this goal, which can capture particles in an array, hold them against a flow, and selectively release them. The release mechanism uses a vapor microbubble as a means of volume expansion to create a jet of fluid that ejects a particle. The theory, design, and testing are described, and successful operation of the device is demonstrated. Applications and suggestions for future work are discussed.
by Rebecca A. Braff.
S.M.
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Larsson, Felix, and Christian Johansson. "Digital hydraulic actuator for flight control." Thesis, Linköpings universitet, Fluida och mekatroniska system, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-165262.
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In aviation industry, one of the most important aspects is weight savings. This since with a lowered weight, the performance of the aircraft can be increased together with increased fuel savings and thus lowered running costs. One way of saving weight is to reduce energy consumption, since with lowered energy consumption, lowered mass of fuel is required etc. Most aircraft are today maneuvered with hydraulic systems due to its robustness and power density. It is the primary source of power for primary and secondary flight controls. The control of a conventional system which is using proportional valves is done by altering flow by restricting it to the extent where the desired output is achieved, which implies heat losses since the full performance of its supply is wasted through the valve. In previous research, more energy efficient hydraulic systems called digital hydraulics has been investigated. In difference with conventional hydraulics, digital hydraulics uses low cost, high frequency on/off valves, which either are fully opened, or fully closed, instead of proportional valves to achieve the desired output. With this comes the benefit of no energy losses due to leakage and restriction control. The downsides with digital hydraulics is the controlabillity. One way of controlling it is by using several pressure sources which outputs different pressure levels. By using the on/off valves in different combinations, different outputs can be achieved in a discrete manner. In this thesis, the aim was to remove the impact of the discrete force steps which are present in digital hydraulics by creating concepts with hybrid solutions containing both digital hydraulics and restrictive control. Three concepts were developed and investigated using simulation. The energy consumption and performance was analysed and compared with a reference model, the concepts redundancy compared to conventional systems was discussed and finally the concepts were tested with an aircraft simulation model. The concepts were found to reduce the energy consumption with different magnitude depending on the load cycle. The performance was found to be almost as good as the reference model. The redundancy compared with conventional systems should be possible to maintain with slight modifications, but further investigation is needed. It was found that one of the most important aspects regarding energy consumption is which combination of supply pressures is used to supply the system since it influences leakage and flow due to compression.
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Isik, Sinem. "Flight Control System Design For An Over Actuated Uav Against Actuator Failures." Master's thesis, METU, 2010. http://etd.lib.metu.edu.tr/upload/3/12611652/index.pdf.
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This thesis describes the automatic flight control systems designed for a conventional and an over actuated unmanned air vehicle (UAV). A nonlinear simulation model including the flight mechanics equations together with the interpolated nonlinear aerodynamics, environmental effects, mass-inertia properties, thrust calculations and actuator dynamics is createdtrim and linearization codes are developed. Automatic flight control system of the conventional UAV is designed by using both classical and robust control methods. Performances of the designs for full autonomous flight are tested through nonlinear simulations for different maneuvers in the presence of uncertainties and disturbances in the aircraft model. The fault tolerant control of an over actuated UAV is the main concern of the thesis. The flight control system is designed using classical control techniques. Two static control allocation methods are examined: Moore-Penrose pseudo inverse and blended inverse. For this purpose, an aircraft with three sets of ailerons is employed. It is shown that with redundant control surfaces, fault tolerant control is possible. Although both of the static control allocation methods are found to be quite successful to realize the maneuvers, the new blended inverse algorithm is shown to be more effective in controlling the aircraft when some of the control surfaces are lost. It is also demonstrated that, with redundant control surfaces it is possible to recover the aircraft during a maneuver even some of the control surfaces are damaged or got stuck at a particular deflection.
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Barragán, Patrick R. "An efficient drive, sensing, and actuation system using PZT stack actuator cells." Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/70462.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering; and, (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2012.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 81-82).
The PZT cellular actuator developed in the MIT d'Arbeloff Laboratory utilizes small-strain, high-force PZT stack actuators in a mechanical flexure system to produce a larger-strain, lower-force actuator useful in robotic systems. Many functionalities for these cellular actuators are developed which can have great impact on robotic systems and actuation itself. After initial exploration into other possible circuitry, a circuit is designed to recovery unused energy for the PZT cells. The circuit design is formed around a proposed method of distributed actuation using PZT cells which imposes that different PZT cells will be activated during different periods such that the charge from some cells can be transferred to others. If the application allows actuation which can conform to this criteria, the developed circuit can be used which, without optimization, can save ~41% of the energy used to drive the actuators with a theoretical upper limit on energy efficiency of 100%. A dynamic system consisting of multiple PZT actuators driving a linear gear is analyzed and simulated which can achieve a no load speed 2.4 m/s with minimal actuators. Then, the two-way transforming properties of PZT stack actuators are utilized to allow dual sensing and actuation. This method uses an inactive PZT cell as a sensor. With no additional sensors, a pendulum system driven by antagonistic groups of PZT cells is shown to find its own resonance with no system model. These functionalities of charge recovery, distributed actuation, and dual sensing and actuation set the PZT cellular actuator as an important contribution to robotic actuation and begin to illuminate the possible impacts of the concept. The design and analysis described reveals many possibilities for future applications and developments using the PZT cellular actuator in the fields of actuation and robotics.
by Patrick R. Barragán
S.M.
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Wroble, Daniel G. "Force Fight Study in a Dual Electromechanical Actuator Configuration." University of Dayton / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1512641850024148.
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Sivakumar, Kousik. "Nanowire sensor and actuator." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file 5.53 Mb., 108 p, 2006. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pqdiss&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&rft_dat=xri:pqdiss:1435931.
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Kim, Doyeon. "Electrochemically controllable biomimetic actuator." abstract and full text PDF (free order & download UNR users only), 2006. http://0-gateway.proquest.com.innopac.library.unr.edu/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3239874.
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Janko, Balazs. "Dual drive series actuator." Thesis, University of Reading, 2015. http://centaur.reading.ac.uk/41865/.
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Industrial robotic manipulators can be found in most factories today. Their tasks are accomplished through actively moving, placing and assembling parts. This movement is facilitated by actuators that apply a torque in response to a command signal. The presence of friction and possibly backlash have instigated the development of sophisticated compensation and control methods in order to achieve the desired performance may that be accurate motion tracking, fast movement or in fact contact with the environment. This thesis presents a dual drive actuator design that is capable of physically linearising friction and hence eliminating the need for complex compensation algorithms. A number of mathematical models are derived that allow for the simulation of the actuator dynamics. The actuator may be constructed using geared dc motors, in which case the benefits of torque magnification is retained whilst the increased non-linear friction effects are also linearised. An additional benefit of the actuator is the high quality, low latency output position signal provided by the differencing of the two drive positions. Due to this and the linearised nature of friction, the actuator is well suited for low velocity, stop-start applications, micro-manipulation and even in hard-contact tasks. There are, however, disadvantages to its design. When idle, the device uses power whilst many other, single drive actuators do not. Also the complexity of the models mean that parameterisation is difficult. Management of start-up conditions still pose a challenge.
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Malère, João Pedro Pinheiro. "Hydraulic actuator failure prognostics." Instituto Tecnológico de Aeronáutica, 2007. http://www.bd.bibl.ita.br/tde_busca/arquivo.php?codArquivo=970.
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This work presents an application of failure prognosis in the system command actuator of a commercial aircraft. An efficient failure prognostic algorithm provides a reduction in the number of unscheduled events and consequently generates a significant reduction in the maintenance costs. Although this is a simulation-based work, it presents a pre validation with bench tests data. The method starts by computational mathematical modeling of the system and this further validation by laboratory results. The sensitivity study of the variables is necessary in order to understand which parameters affect the system. The estimation of a confidence interval to determine the nominal behavior failure allows detection and isolation. Parity state techniques will be used for the residue signals design which will be the of the degradation measurement. A simulation of the failure behavior over the time to forecast when the system will reach a determined threshold is also presented.
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Scott, Eric Landon. "Criteria based actuator control /." Digital version accessible at:, 1999. http://wwwlib.umi.com/cr/utexas/main.
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Lin, Mark Wen-Yih. "Theoretical modeling of the actuation mechanism in integrated induced strain actuator/substructure systems." Diss., Virginia Tech, 1993. http://hdl.handle.net/10919/38544.
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Induced strain actuators have been integrated with conventional structural materials to serve as energy input devices or actuating elements in many engineering applications implementing intelligent material systems and structures concepts. In order to use the actuation mechanism produced by the integrated induced strain actuators efficiently, the mechanics of the mechanical interaction between the actuator and the host substructure must be understood and modeled accurately. A refined analytical model has been developed based on the plane stress formulation of the theory of elasticity for a surfacebonded induced strain actuator/beam substructure system. Closed-form solutions of the induced stress field were obtained in an approximate manner using the principle of stationary complementary energy. The model has also been extended to include the presence of adhesive bonding layers and applied external loads. The results of the current model were compared with those obtained by finite element analysis and the pin-force and Euler-Bernoulli models.
It was shown that the current model is capable of describing the edge effects of the actuator on actuation force/moment transfer and interfacial shear and peeling stress distributions that the existing analytical models fail to describe. Good agreement was obtained between the current model and the finite element analysis in terms of predicting actuation force/moment transfer. The interfacial shear stress distribution obtained by the current model satisfies stress-free boundary conditions at the ends of the actuator, which the finite element model is not able to satisfy. The current model correctly describes the transfer of the actuation mechanism and the resulting interfacial stress distributions; thus, it can be used in designing integrated induced strain actuator/substructure systems.
Moreover, a new induced strain actuator configuration, which includes inactive edges on the ends of the actuators, has been proposed to alleviate the intensity of the interfacial stresses. The effectiveness of the actuator on the interfacial stress alleviation was verified by the current analytical model and finite element analysis. It was shown that the proposed actuator configuration can significantly alleviate intensive interfacial shear and peeling stresses without sacrificing the effectiveness of the actuation mechanism. The chances of interfacial failure of the integrated structural system, fatigue failure in particular, can thus be reduced.Ph. D.
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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.
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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.
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Day, Graham Allen. "Synthesis and Design of a Bimodal Rotary Series Elastic Actuator." Thesis, Virginia Tech, 2016. http://hdl.handle.net/10919/71665.
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A novel rotary series elastic actuator (RSEA) with a two-mode, or bimodal, elastic element was designed and tested. This device was developed to eliminate the compromise between human safety and robot performance. Rigid actuators can be dangerous to humans within a robot's workspace due to impacts or pinning scenarios. To increase safety, elastic elements can soften impacts and allow for escape should pinning occur. However, adding elasticity increases the complexity of the system, lowers the bandwidth, and can make control of the actuator more difficult. To get the best of both types of actuators, a bimodal clutch was designed to switch between rigid actuation for performance and elastic actuation for human safety.
The actuator consisted of two main parts, a rigid rotary actuator using a harmonic gearhead and a drum brake designed to act as a clutch. The 200 W rotary actuator provides 54.7 Nm of torque with a maximum speed of 41.4 rpm. The measured efficiency was 0.797 due to a timing belt speed reduction that was then speed reduced with a harmonic gearhead. The clutch was a drum brake actuated with a pantograph linkage and ACME lead screw. This configuration produced 11 Nm of holding torque experimentally but was theoretically shown to produce up to 51.4 Nm with larger motors. The elastic element was designed using finite element analysis (FEA) and tested experimentally to find a measured stiffness of 290 Nm/rad.Master of Science
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Ermert, Markus. "Electromechanical actuator concept for the controlled and direct actuation of a hydraulic main stage." Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-200729.
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Hydraulic main stages for off highway machines have usually electromagnetic driven pilot valves. You rarely find stepper motor driven pilot systems that are directly positioning the main spool in the sectional control valve. The presented concept shows the development of an actuator in a unique setup to fulfill the requirements of most off- highway applications. Precise positioning, strength, speed and fail safe requirements were the main goals of the concept. The concept has a two phase BLDC transversal flux motor with a single gear stage transmission. The software and control unit are specially designed for this electric motor setup. On a test bench some results of the first samples reveal the technical potential of this concept. The development of the actuator was done in-house of Thomas Magnete GmbH (mechanical, electronical, and software development).
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English, Brian Alan. "Laminated Gas Generator Actuator Arrays." Diss., Georgia Institute of Technology, 2006. http://hdl.handle.net/1853/14074.
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Existing microactuator limitations prevent control of small-scale, spin-stabilized vehicles. These applications require actuators insensitive to shock that have forces on the order of Newtons and millisecond control periods. This research presents batch-fabrication lamination approaches for the realization of large arrays of high-impulse, short-duration gas generator actuators (GGAs), and system implementation approaches to integrate these GGAs into a small-scale, spin-stabilized projectile for the purpose of generating steering forces on the projectile. Electronic packaging and MEMS processing are combined to batch-fabricate millimeter-scale GGAs insensitive to large shocks. Robust, prefabricated thermoplastic and metal films are patterned by laser machining or photolithography, and multilayer devices are assembled by adhesive lamination. The GGAs remained operational after 10,000 g shocks. Optimized design and propellant selection enables control of the force profile and actuation timing. Rapid force rise times are achieved using appropriately selected solid propellants and specially designed hot-wire igniters that create a larger combustion fronts. By reshaping the combustion profile of the solid propellant, tens of Newtons are generated within milliseconds. In addition to force control, the timing of the force application was controllable to within 1 ms for optimized GGAs. Performance results demonstrate that GGA actuator arrays actuate within appropriate timescales and with enough authority to control a 40 mm projectile with a spin rate of 60 Hz. After actuator characterization, GGAs, control electronics, and power supply are mounted into a 40 mm diameter projectile, and a full flight system was flown to demonstrate divert authority of the GGAs.
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Giurgea, Constantin. "Precise motion with piezoelectric actuator." Thesis, University of Ottawa (Canada), 2002. http://hdl.handle.net/10393/6184.
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The purpose of this study is to determine the displacement performance of a high accuracy-positioning device equipped with three piezo ceramic actuators. The displacement performance of each individual actuator is investigated in order to perform controlled motion over a very small range. A nanometric precision three-degrees of freedom positioner was designed and fabricated. In order to design a proper closed-loop controller, the open loop characteristics of the nanopositioner were experimentally investigated.
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Alsop, Peter. "The self-validating process actuator." Thesis, University of Oxford, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.308676.
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Garcia, Angelo. "Control of nitinol wire actuator." Thesis, University of Canterbury. Mechanical Engineering, 2003. http://hdl.handle.net/10092/6610.
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The Stewart Platform is well known parallel robotic mechanism often used for flight simulators. Less well known applications involve robotics and machine tools. This research deals with Stewart Platforms that use Nitinol wire, a shape memory alloy, as binary actuators that are switched on and off to control the position of the platform. Binary control of the six actuators on a platform yields sixty four possible platform positions, and four stacked platforms yield 256E12 possible positions. The design of a simple basic four stages model is described in this research.
Experiments were conducted on the Nitinol wire to investigate the shape memory effects, hysteresis and the martensite/austenite phase transformations. These results were used in the design of a high power to weight ratio Stewart Platform, overcoming many of the drawbacks of previous models that are powered by heavy hydraulics or electric motors. Due to the complexity of some of the parts and small numbers required, rapid prototyping was used to manufacture over 90% of the structure. In this research, the control system proposed is expected to be useful for not only Shape Memory Alloy (SMA) actuators but also other actuators with hysteresis, for example, piezoceramic actuators, rubber actuators driven by air supply, bellows actuators, etc.
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Benson, Christopher Lee. "Linear actuator powered flapping wing." Thesis, Massachusetts Institute of Technology, 2010. http://hdl.handle.net/1721.1/59892.
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Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2010.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 58-59).
Small scale unmanned aerial vehicles (UAVs) have proven themselves to be useful, but often too noisy for certain operations due to their rotary motors. This project examined the feasibility of using an almost silent linear actuator to power a flapping wing UAV. In order to this, a wing was designed and installed into a test set-up to replicate normal flight conditions of flapping wing flight (FWF). The designs of the wing, the test set-up and the actual experiments were biomimetic, looking to approximate the flight of real birds. The main goal of this study was to characterize a novel new linear actuator being developed in the Bio-Instrumentation Lab at MIT based on important parameters for FWF including the mounting position, the frequency of oscillation and the amplitude of oscillation of the wing. Ultimately the linear actuator performed well under all of the tests and was only limited by the control software. When the frequency and amplitude of oscillation were raised, the force on the actuator increased. The mounting position ended up not having a correlation with the force on the actuator, leading one to believe that it is not a critical parameter for this actuator-wing system.
by Christopher L. Benson.
S.B.
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Rezgui, Abdelmounaam. "Service-Oriented Sensor-Actuator Networks." Diss., Virginia Tech, 2007. http://hdl.handle.net/10919/30098.
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In this dissertation, we propose service-oriented sensor-actuator networks (SOSANETs) as a new paradigm for building the next generation of customizable, open, interoperable sensor-actuator networks. In SOSANETs, nodes expose their capabilities to applications in the form of service profiles. A node's service profile consists of a set of services (i.e., sensing and actuation capabilities) that it provides and the quality of service (QoS) parameters associated with those services (delay, accuracy, freshness, etc.). SOSANETs provide the benefits of both application-specific SANETs and generic SANETs. We first define a query model and an architecture for SOSANETs. The proposed query model offers a simple, uniform query interface whereby applications specify sensing and actuation queries independently from any specific deployment of the underlying SOSANET. We then present uRACER (Reliable Adaptive serviCe-driven Efficient Routing), a routing protocol suite for SOSANETs. uRACER consists of three routing protocols,
namely, SARP (Service-Aware Routing Protocol), CARP (Context-Aware Routing Protocol), and TARP (Trust-Aware Routing Protocol). SARP uses an efficient service-aware routing approach that aggressively reduces downstream traffic by translating service profiles into efficient paths. CARP supports QoS by dynamically adapting each node's routing behavior and service profile according to the current context of that node, i.e. number of pending queries and number and type of messages to be routed. Finally, TARP achieves high end-to-end reliability through a scalable reputation-based approach in which each node is able to locally estimate the next hop of the most reliable path to the sink. We also propose query optimization techniques that contribute to the efficient execution of queries in SOSANETs. To evaluate the proposed service-oriented architecture, we implemented TinySOA, a prototype SOSANET built on top of TinyOS with uRACER as its routing mechansim. TinySOA is designed as a set of layers with a loose interaction model that enables several cross-layer optimization options. We conducted an evaluation of TinySOA that included a comparison with TinyDB. The obtained empirical results show that TinySOA achieves significant improvements on many aspects including energy consumption, scalability, reliability and response time.Ph. D.
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Wilson, Thomas Lawler. "A multi-coil magnetostrictive actuator." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/28243.
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Thesis (M. S.)--Mechanical Engineering, Georgia Institute of Technology, 2009.Committee Chair: Zinn, Ben T.; Committee Member: Book, Wayne; Committee Member: Glezer, Ari; Committee Member: Neumeier, Yedidia; Committee Member: Seitzman, Jerry.
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Orekhov, Viktor Leonidovich. "Series Elasticity in Linearly Actuated Humanoids." Diss., Virginia Tech, 2015. http://hdl.handle.net/10919/71788.
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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.
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Askari, Vahid. "Design and control of a novel actuator based on human muscle characteristics, the Muscle Actuator." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0023/NQ50031.pdf.
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KRUTZ, JILL E. "DESIGN OF A HYDRAULIC ACTUATOR TEST STAND FOR NON-LINEAR ANALYSIS OF HYDRAULIC ACTUATOR SYSTEM." University of Cincinnati / OhioLINK, 2001. http://rave.ohiolink.edu/etdc/view?acc_num=ucin990813095.
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Krutz, Jill E. "Design of a hydraulic actuator test stand for non-linear analysis of hydraulic actuator systems." Cincinnati, Ohio : University of Cincinnati, 2001. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=ucin990813095.
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Headings, Leon Mark. "Modeling, characterization, and design of smart material driven stick-slip actuation mechanisms." Connect to resource, 2005. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1141700440.
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Murillo, Jaime. "Design of a Pneumatic Artificial Muscle for Powered Lower Limb Prostheses." Thèse, Université d'Ottawa / University of Ottawa, 2013. http://hdl.handle.net/10393/24104.
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Ideal prostheses are defined as artificial limbs that would permit physically impaired individuals freedom of movement and independence rather than a life of disability and dependence. Current lower limb prostheses range from a single mechanical revolute joint to advanced microprocessor controlled mechanisms. Despite the advancement in technology and medicine, current lower limb prostheses are still lacking an actuation element, which prohibits patients from regaining their original mobility and improving their quality of life.
This thesis aims to design and test a Pneumatic Artificial Muscle that would actuate lower limb prostheses. This would offer patients the ability to ascend and descend stairs as well as standing up from a sitting position. A comprehensive study of knee biomechanics is first accomplished to characterize the actuation requirement, and subsequently a Pneumatic Artificial Muscle design is proposed. A novel design of muscle end fixtures is presented which would allow the muscle to operate at a gage pressure surpassing 2.76 MPa (i.e. 400 psi) and yield a muscle force that is at least 3 times greater than that produced by any existing equivalent Pneumatic Artificial Muscle. Finally, the proposed Pneumatic Artificial Muscle is tested and validated to verify that it meets the size, weight, kinetic and kinematic requirements of human knee articulation.
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Tognetti, Lawrence Joseph. "Actuator design for a haptic display." Thesis, Georgia Institute of Technology, 1999. http://hdl.handle.net/1853/16926.
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Bischoff, Urs. "Engineering distrubuted senso-actuator network applications." Thesis, Lancaster University, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.525332.
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Pillai, Priam Vasudevan. "Conducting polymer actuator enhancement through microstructuring." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/39881.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2007.Includes bibliographical references (leaves 75-79).
Electroactive conducting polymers, such as polypyrrole, polyaniline, and polythiophenes are currently studied as novel biologically inspired actuators. The actuation mechanisms in these materials are based on the diffusion of ions in and out of the polymer film. Giving ions more access to the center of the films by inducing holes on its surface can improve strain rates. A unique surface templating technique using breath figures has been developed for poly (3-hexylthiophene). Spherical holes form on the surface of polymer films during the drop casting process if moist air was blown over the top of the film. This technique has been used to generate 0.8-5 /m holes on the surface of poly(3-hexylthiophene) films. It can also be used to create columns 3 to 10 /tm in height in polypyrrole. Free standing spongy films (10-35 iLm in thickness) of poly(3-hexylthiophene) were generated using this technique and the influence of the additional surface area on the actuation of poly(3-hexylthiophene) and polypyrrole films has been characterized.
(cont.) Actuation seen in poly(3-hexylthiophene) films was not characteristic of actuation seen in polypyrrole or in poly(3,4-ethylenedioxythiophene). Poly(3-hexylthiophene) shows a voltage dependant on-off mechanism as well as a non charge dependant actuation mechanism. This has been primarily attributed to the change in the polymer modulus during the actuation cycle. The subsequent part of this thesis begins the development of linear system identification techniques to track the effect of the changing modulus during actuation.
by Priam Vasudevan Pillai.
S.M.
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Meléndez, H. Roberto J. "A Reluctance Actuator Gap Disturbance Testbed." Thesis, Massachusetts Institute of Technology, 2014. http://hdl.handle.net/1721.1/93009.
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Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2014.Cataloged from PDF version of thesis.
Includes bibliographical references (page 69).
We have designed and built a Reluctance Actuator Gap Disturbance Testbed. The testbed emulates the short stroke and long stroke interaction of modern lithography stages. The testbed can be used to impart gap disturbance of the order of 10[mu]m to a target platten thereby providing a gap disturbance to the reluctance actuator. The testbed is equipped with three single-axis load cells that can measure a normal force, a roll torque and a pitch torque. We keep track of the orientation and position of the stage by using capacitance probes. The gap disturbance is imparted with three piezos capable of a stroke of 15[mu]m.We have also fabricated several reluctance actuators that fit into this testbed. These actuators use a two coil winding per core to prevent leakage and reduce stray torques. The cores of these actuators are made of Cobalt Iron, the soft magnetic material with the highest flux density saturation. Both a single actuator and a double actuator were fabricated. The double actuator can impart a roll torque as well as a normal force. Finite Element Method was utilized to design the actuators and to understand the nature of the rotational stiffness of the actuator. Experiments to do disturbance rejection were carried out and also different methods of force control (like Flux Feedback) are discussed and implemented
by Roberto J. Meléndez H.
S.M.
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Crawshaw, Stuart. "Control of systems with actuator nonlinearities." Thesis, University of Cambridge, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.621960.
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Qiu, Yan. "Distributed piezoelectric actuator with complex shape." Thesis, Peninsula Technikon, 2002. http://hdl.handle.net/20.500.11838/1263.
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Thesis (MTech (Mechanical Engineering))--Peninsula Technikon, Cape Town, 2002Distributed Piezoelectric Actuator (DPA) is one kind of actuator in the smart technology field. Firstly, DPA is one kind of solid-state actuator, and can be embedded in the structure. Secondly, it can be controlled by the electrical signal with high bandwidth and high precision. So it can be applied in the many different fields, such as high-resolution positioning, noise and vibration detection and shape control. Up to now, all of the DPA theory investigations and the product designs are based on applying the approximate electrical field. And only the rectangular shape DPA has been studied. The accurate distribution and intensity of electrical and mechanics field, and the numerical imitation for the DPA products with rectangular and other shapes have never been discussed and studied. Therefore, the development of DPA to be used in the micro application, such as in the Micro Electro-Mechanical System (MEMS), has been limited. This thesis has developed the analytical analysis models for two types of DPA elements and the part circular shape DPA element. The MathCAD and MATLAB program have been used to develop the analytical models. The ABAQUS program has also been used to compare the results between the analytical models and Finite Element Method (FEM). Finally, the accuracy and reliability of analytical models have been proved by results comparison between the analytical models, FEM and the product testing data from the industry. This thesis consists of five chapters. Chapter 1 is the introduction of smart structure. The characterizations of constituent materials, including the piezoelectric material and matrix epoxy material have been discussed in Chapter 2. In Chapter 3, the analytical models for two type of DPA element have been developed and the comparisons have also been completed. The analytical models for part circular shape DPA element have been developed in Chapter 4. The conclusions and recommendations are included in Chapter 5.
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Oo, Htet Htet Nwe. "Actuator Disk Theory for Compressible Flow." DigitalCommons@CalPoly, 2017. https://digitalcommons.calpoly.edu/theses/1727.
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Because compressibility effects arise in real applications of propellers and turbines, the Actuator Disk Theory or Froude’s Momentum Theory was established for compressible, subsonic flow using the three laws of conservation and isentropic thermodynamics. The compressible Actuator Disk Theory was established for the unducted (bare) and ducted cases in which the disk was treated as the only assembly within the flow stream in the bare case and enclosed by a duct having a constant cross-sectional area equal to the disk area in the ducted case. The primary motivation of the current thesis was to predict the ideal performance of a small ram-air turbine (microRAT), operating at high subsonic Mach numbers, that would power an autonomous Boundary Layer Data System during test flights. The compressible-flow governing equations were applied to a propeller and a turbine for both the bare and ducted cases. The solutions to the resulting system of coupled, non-linear, algebraic equations were obtained using an iterative approach. The results showed that the power extraction efficiency and the total drag coefficient of the bare turbine are slightly higher for compressible flow than for incompressible flow. As the free-stream Mach increases, the Betz limit of the compressible bare turbine slightly increases from the incompressible value of 0.593 and occurs at a velocity ratio between the far downstream and the free-stream that is lower than the incompressible value of 0.333. From incompressible to a free-stream Mach number of 0.8, the Betz limit increases by 0.021 while its corresponding velocity ratio decreases by 0.036. The Betz limit and its corresponding velocity ratio for the ducted turbine are not affected by the free-stream Mach and are the same for both incompressible and compressible flow. The total drag coefficient of the ducted turbine is also the same regardless of the free-stream Mach number and the compressibility of the flow; but, the individual contributions of the turbine drag and the lip thrust to the total drag differs between compressible and incompressible flow and between varying free-stream Mach numbers. It was concluded that overall compressibility has little influence on the ideal performance of an actuator disk.
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Thorapalli, Muralidharan Seshagopalan, and Ruihao Zhu. "Continuum Actuator Based Soft Quadruped Robot." Thesis, KTH, Mekatronik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-286348.
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Quadruped robots can traverse a multitude of terrains with greater ease when compared to wheeled robots. Traditional rigid quadruped robots possess severe limitations as they lack structural compliance. Most of the existing soft quadruped robots are tethered and are actuated using pneumatics, which is a low grade energy source and lacks viability for long endurance robots. The work in this thesis proposes the development of a continuum actuator driven quadruped robot which can provide compliance while being un-tethered and electro-mechanically driven. In this work, continuum actuators are developed using mostly 3D printed parts. Additionally, the closed loop control of continuum actuators for walking is developed. Linear Quadratic Regulator (LQR) and pole placement based methods for controller synthesis were evaluated and LQR was determined to be better when minimizing the actuator effort and deviation from set-point. These continuum actuators are composed together to form a quadruped. Gait analyses on the quadruped were conducted and legs of the quadruped were able to trace the gaits for walking and galloping.Fyrfotarobotar kan lättare korsa en mängd olika terränger jämfört med hjulrobotar. Traditionella styva fyrfotarobotar har kraftiga begränsningar då de saknar strukturell följsamhet. De flesta befintliga mjuka fyrbenta robotar är kopplade till en eller flera kablar och drivs av pneumatik, vilket är en lågkvalitativ energikälla och lämpar sig inte för robotar med lång uthållighet. Arbetet i denna avhandling föreslår utvecklingen av en continuum ställdonsdriven fyrfotarobot, som ger följsamhet samtidigt som den ¨ar frånkopplad och elektromekaniskt driven. I detta arbete framställs continuum ställdon med mestadels 3D-printade delar. Dessutom utvecklas dessa ställdons slutna kontrolloop för gång. Linjärkvadratisk regulator (LQR) och metoder baserade på polplacering utvärderades för styrsyntes, och det fastställdes att LQR presterade bättre när man minimerar ställdonets ansträngning samt avvikelse från referensvärde. Continuum ställdon sammansattes för att bilda en fyrbent robot. Gånganalyser utfördes på roboten och dess ben kunde följa gång- och galopprörelser.
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Hofmann, Lorenz M. "The flow response to actuator motion /." The Ohio State University, 1996. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487941504296049.
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Le, Guilly Marie O. "Development of ionic polymer actuator arrays /." Thesis, Connect to this title online; UW restricted, 2004. http://hdl.handle.net/1773/7078.
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Snyder, Adam Thomas. "Cardiac catheter control using actuator wire." Thesis, University of Iowa, 2017. https://ir.uiowa.edu/etd/5855.
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The main goal of this research is to design a snake-like robot arm to provide control of a cardiac catheter for use in endovascular aortic repair that is small, cheap, and easy to use. This will help increase the number of aortic aneurysms eligible for endovascular repair and make the procedure simpler and safer for both the patient and the operator. The arm surrounds the catheter and is comprised of two joints that can independently move in any direction giving the operator the ability to easily navigate complicated paths and to control the arm remotely. The arm is controlled by Flexinol actuator wire which is comprised of a nickel titanium alloy that contracts when heated. This allows the arm to be controlled electrically by sending current through the actuator wire thereby heating it. The level of current can be controlled using a microcontroller to generate a pulse width modulated signal to vary the average current. The arm can then be controlled remotely by an operator.
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Rudder, Benjamin A. "Motor protein inspired "artificial muscle" actuator." Thesis, Queensland University of Technology, 2017. https://eprints.qut.edu.au/105648/1/Benjamin_Rudder_Thesis.pdf.
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In this thesis, the foundation is laid for a new form of artificial muscle, which more closely mimics the structure of skeletal muscle down to its most basic units; motor proteins. An electro-mechanical drive method together with the geometrical properties of the sarcomere, aim to create an efficient, safe, and low temperature device which can be implanted or be in contact with skin. The feasibility of the principle is investigated, physical size limitations of each working element ascertained, and two (larger scale) prototypes produced. A numerical simulation is developed to enable optimization through refining the design with further conditions.
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Pan, Le. "Feedback linearization of antagonistically actuated variable stiffness joints with twisted string actuators." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2014. http://amslaurea.unibo.it/7813/.
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The work of this thesis is on the implementation of a variable stiffness joint antagonistically actuated by a couple of twisted-string actuator (TSA). This type of joint is possible to be applied in the field of robotics, like UB Hand IV (the anthropomorphic robotic hand developed by University of Bologna). The purposes of the activities are to build the joint dynamic model and simultaneously control the position and stiffness. Three different control approaches (Feedback linearization, PID, PID+Feedforward) are proposed and validated in simulation. To improve the properties of joint stiffness, a joint with elastic element is taken into account and discussed. To the end, the experimental setup that has been developed for the experimental validation of the proposed control approaches.
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Bhargava, Adesh. "Experimental/analytical determination of optimal piezoelectric actuator locations on complex structures based on the actuator power factor." Thesis, This resource online, 1995. http://scholar.lib.vt.edu/theses/available/etd-08222009-040530/.
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Lim, Jung Youl. "A distributed multi-level current modeling method for design analysis and optimization of permanent magnet electromechanical actuators." Diss., Georgia Institute of Technology, 2014. http://hdl.handle.net/1853/53990.
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This thesis has been motivated by the growing needs for multi-degree of freedom (M-DOF) electromagnetic actuators capable of smooth and accurate multi-dimensional driving motions. Because high coercive rare-earth permanent-magnets (PMs) are widely available at low cost, their uses for developing compact, energy-efficient M-DOF actuators have been widely researched. To facilitate design analysis and optimization, this thesis research seeks to develop a general method based on distributed source models to characterize M-DOF PM-based actuators and optimize their designs to achieve high torque-to-weight performance with compact structures
To achieve the above stated objective, a new method that is referred to here as distributed multi-level current (DMC) utilizes geometrically defined point sources has been developed to model electromagnetic components and phenomena, which include PMs, electromagnets (EMs), iron paths and induced eddy current. Unlike existing numerical methods (such as FEM, FDM, or MLM) which solve for the magnetic fields from Maxwell’s equations and boundary conditions, the DMC-based method develops closed-form solutions to the magnetic field and force problems on the basis of electromagnetic point currents in a multi-level structure while allowing trade-off between computational speed and accuracy. Since the multi-level currents can be directly defined at the geometrically decomposed volumes and surfaces of the components (such as electric conductors and magnetic materials) that make up of the electromagnetic system, the DMC model has been effectively incorporated in topology optimization to maximize the torque-to-weight ratio of an electromechanical actuator. To demonstrate the above advantages, the DMC optimization has been employed to optimize the several designs ranging from conventional single-axis actuators, 2-DOF linear-rotary motors to 3-DOF spherical motors.
The DMC modeling method has been experimentally validated and compared against published data. While the DMC model offers an efficient means for the design analysis and optimization of electromechanical systems with improved computational accuracy and speed, it can be extended to a broad spectrum of emerging and creative applications involving electromagnetic systems.
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Montazami, Reza. "Smart Polymer Electromechanical Actuators for Soft Microrobotic Applications." Diss., Virginia Tech, 2011. http://hdl.handle.net/10919/28084.
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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.
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Santiago, Anadón José R. "Large force shape memory alloy linear actuator." [Gainesville, Fla.] : University of Florida, 2002. http://purl.fcla.edu/fcla/etd/UFE1001179.
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Pachalla, Seshadri Rajagopal. "Analysis of oscillating flow cooled SMA actuator." Texas A&M University, 2004. http://hdl.handle.net/1969.1/2669.
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Shape Memory Alloys (SMA) are a group of metallic alloys that have the ability to return to some previously defined shape or size when subjected to an appropriate thermal cycling procedure. In recent years there has been a lot of research on the development of small, light and, yet, powerful actuators for use in areas like robotics, prosthetics, biomimetics, shape control and grippers. Many of the miniaturized conventional actuators do not have sufficient power output to be useful and SMAs can be used advantageously here.
The widespread use of SMAs in actuators is limited by their low bandwidth. Use of SMAs in two-way actuators requires that they undergo thermal cycling (heating and cooling). While SMAs can be heated quickly by resistive heating, conventional convection cooling mechanisms are much slower as the exothermic austenitic to martensitic phase transformation is accompanied by the release of significant amount of latent heat.
While a number of cooling mechanisms have been studied in SMA actuator literature, most of the cooling mechanisms involve unidirectional forced convection. This may not be the most effective method. Oscillating flow in a channel can sometimes enhance heat transfer over a unidirectional flow. One possible explanation for this heat transfer enhancement is that the oscillatory flow creates a very thin Stokes viscous boundary-layer and hence a large time-dependent transverse temperature gradient at the heated wall. Therefore heat transfer takes place at a large temperature difference, thereby enhancing the heat transfer.
In this work, the heat transfer from an SMA actuator under an oscillating channel is investigated and is compared to steady, unidirectional flow heat transfer.
Oscillating flow is simulated using a finite volume based method. The resulting velocity field is made use of in solving the heat transfer problem using a finite difference scheme. A parametric study is undertaken to identify the optimal flow conditions required to produce the maximum output for a given geometry of the SMA actuator. The latent heat of transformation of the SMA is accounted for by means of a temperature dependent specific heat.