39 research outputs found

    Design Of A Piezoelectric Tactile Sensor

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    Tez (Yüksek Lisans) -- İstanbul Teknik Üniversitesi, Fen Bilimleri Enstitüsü, 2012Thesis (M.Sc.) -- İstanbul Technical University, Institute of Science and Technology, 2012İnsanlardaki dokunma duyusu, dokunsal algılayıcıların ana ilham kaynağı olmuştur. Bu çalışmadaki amaç ise dokunma duyusuna yakınsayacak yeni nesil sentetik polimer fiber dizisinin tasarımı ve üretimidir. Bu fiber dizisinin üzerindeki basınç dağılımını algılaması amaçlanmaktadır. Tasarlanan fiber dizisinin hem yüzey pürüzlülüğüne adapte olabilen biyolojiden esinlenilmiş fiber yapısının bulunması, hem de oluşan temas ile ortaya çıkan basıncı elektriksek potansiyel farka çevirebilecek piezoelektrik ince tabakaya sahip olması gerekmektedir. Yapılan çalışmada basıncı algılama kabiliyetine sahip PVDF piezoelektrik tabakaya ilave edilmiş PDMS polimer düşey fiber dizisini sonlu eleman metodu kullanılarak analizi yapılmıştır. Piezoelektrik polimer uygulanan kuvvet sonucunda elektriksek potansiyel farkı yaratmaktadır. Bu potansiyel fark mikro/nano polimer fiberler sayesinde ayrıştırılabilir ve bu ayrıştırma polimer tabaka üzerindeki basıncın haritalandırılmasına yarar. Tasarlanan algılayıcıda PDMS polimerden üretilmiş fiberlerin çıkış voltajına ve insan elinin uzamsal çözünürlüğe yakınsamasındaki boyutsal değişkenlere etkisi araştırılmıştır. Tüm bu tasarım ölçütlerinin sağlanabilmesi statik ve dinamik çalışma koşullarının incelenmesi ve dokunma algısının altında yatan nörofizyolojinin özümsenmesini içermektedir. Piezoelektrik polimerin elektrotlanması sayesinde gecko ayaklarının yapışma ve yüzeyi tanıma özelliği taklit edilmeye çalışılmıştır. Fiberlerin geometrileri sayesinde basıncın belli bir alana yoğunlaştırılması sağlanmış bu sayede birim kuvvete elde edilecek potansiyel farkın artırılması ve algılayıcının hassasiyetinin artırımı sağlanmıştır. Fakat piezoelektrik PVDF polimerin yüzey enerjisinin diğer polimerlere oranla daha düşük kalmasından dolayı yapışma özelliği yetersiz kalmaktadır. Bu ise üzerine yerleştirilmiş PDMS ya da PMMA gidi sık kullanılan polimerler sayesinde telafi edilmiştir.The human sense of touch is the main inspiration to tactile sensing. The aim of this thesis is to design and manufacture a novel synthetic polymer fiber array with sensing capability of the pressure distribution. The polymer fiber array has both bio-inspired fibrillar structures that can adapt to the surface roughness and polymer piezoelectric film that can generate potential difference proportional to the pressure generated by the contact with the surrounding. In this work, the sensing capability of polyvinylidene fluoride (PVDF) piezoelectric film integrated with PDMS (Polydimethylsiloxane) polymer vertical fiber array has been analyzed using finite element method (FEM). Piezoelectric polymer generates electric potential difference with the applied force, which can be decoupled by the micro/nano polymer pillars, results in the mapping of the pressure distribution among the polymer film. The contribution of the pillars, made out of PDMS (Polydimethylsiloxane), to the output voltage and the dimensional parameters are examined for a satisfactory design that can meet the spatial resolution of the human hand. In order to meet all design requirements, the sensor design should include the static and dynamic analysis and understanding of neurophysiology of touch. By electroding the polymer film, it is aimed to mimic the adhesion and surface adaptation characteristics of the foot of gecko. The geometry of the fiber increases the pressure concentration and the sensitivity of the sensor. However, since the surface energy of PVDF polymer is low, polymers like PDMS or PMMA have been used to compensate the drawback.Yüksek LisansM.Sc

    The Fifth NASA/DOD Controls-Structures Interaction Technology Conference, part 1

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    This publication is a compilation of the papers presented at the Fifth NASA/DoD Controls-Structures Interaction (CSI) Technology Conference held in Lake Tahoe, Nevada, March 3-5, 1992. The conference, which was jointly sponsored by the NASA Office of Aeronautics and Space Technology and the Department of Defense, was organized by the NASA Langley Research Center. The purpose of this conference was to report to industry, academia, and government agencies on the current status of controls-structures interaction technology. The agenda covered ground testing, integrated design, analysis, flight experiments and concepts

    Space station systems: A bibliography with indexes (supplement 6)

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    This bibliography lists 1,133 reports, articles, and other documents introduced into the NASA scientific and technical information system between July 1, 1987 and December 31, 1987. Its purpose is to provide helpful information to the researcher, manager, and designer in technology development and mission design according to system, interactive analysis and design, structural and thermal analysis and design, structural concepts and control systems, electronics, advanced materials, assembly concepts, propulsion, and solar power satellite systems. The coverage includes documents that define major systems and subsystems, servicing and support requirements, procedures and operations, and missions for the current and future Space Station

    Pneumatic Artificial Muscle Driven Trailing Edge Flaps For Active Rotors

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    This research focuses on the development of an active rotor system capable of primary control and vibration reduction for rotorcraft. The objective is to investigate the feasibility of a novel Trailing Edge Flap (TEF) actuation system driven by Pneumatic Artificial Muscles (PAMs). A significant design effort led to a series of experimental apparatuses which tested various aspects of the performance of the actuators themselves and of TEF systems driven by them. Analytical models were developed in parallel to predict the quasistatic and dynamic behavior of these systems. Initial testing of a prototype blade section with an integrated PAM driven TEF proved the viability of the concept through successful benchtop testing under simulated M = 0.3 loading and open jet wind tunnel tests under airspeeds up to M = 0.13. This prototype showed the ability of PAM actuators to generate significant flap deflections over the bandwidth of interest for primary control and vibration reduction on a rotorcraft. It also identified the importance of high pneumatic system mass flow rate for maintaining performance at higher operating frequencies. Research into the development and improvement of PAM actuators centered around a new manufacturing technique which was invented to directly address the weaknesses of previous designs. Detailed finite element model (FEM) analysis of the design allowed for the mitigation of stress concentrations, leading to increased strength. Tensile testing of the swaged actuators showed a factor of safety over 5, and burst pressure testing showed a factor of safety of 3. Over 120,000,000 load cycles were applied to the actuators without failure. Characterization testing before, during, and after the fatigue tests showed no reduction in PAM performance. Wind tunnel testing of a full scale Bell 407 blade retrofitted with a PAM TEF system showed excellent control authority. At the maximum wind tunnel test speed of M = 0.3 and a derated PAM operating pressure of 28 psi, 18.8° half-peak-to-peak flap deflections were achieved at 1/rev (7 Hz), and 17.1° of half-peak-to-peak flap deflection was still available at 5/rev (35 Hz). A quasistatic system model was developed which combined PAM forces, kinematics and flap aerodynamics to predict flap deflection amplitudes. This model agreed well with experimental data. Whirl testing of a sub-span whirl rig under full scale loading conditions showed the ability of PAM TEF systems to operate under full scale levels of centrifugal (CF), aerodynamic, and inertia loading. A commercial pneumatic rotary union was used to provide air in the rotating frame. Extrapolation of the results to 100% of CF acceleration predicts 15.4° of half-peak-to-peak flap deflection at 1/rev (7 Hz), and 7.7° of half-peak-to-peak flap deflection at 5/rev (35 Hz). A dynamic model was developed which successfully predicted the time domain behavior of the PAM actuators and PAM TEF system. This model includes control valve dynamics, frictional tubing losses, pressure dynamics, PAM forces, mechanism kinematics, aerodynamic hinge moments, system stiffness, damping, and inertia to solve for the rotational dynamics of the flap. Control system development led to a closed loop control system for PAM TEF systems capable of tracking complex, multi-sinusoid flap deflections representative of a combined primary control and vibration reduction flap actuation scheme. This research shows the promise that PAM actuators have as drivers for trailing edge flaps on active helicopter rotors. The robustness, ease of integration, control authority and tracking accuracy of these actuators have been established, thereby motivating further research

    Technology for large space systems: A bibliography with indexes (supplement 16)

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    This bibliography lists 673 reports, articles and other documents introduced into the NASA scientific and technical information system between July 1, 1986 and December 31, 1986. Its purpose is to provide helpful information to the researcher, manager, and designer in technology development and mission design according to system interactive analysis and design, structural and thermal analysis and design, structural concepts and control systems, electronics, advanced materials, assembly concepts, propulsion, and solar power satellite systems

    Large space structures and systems in the space station era: A bibliography with indexes (supplement 05)

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    Bibliographies and abstracts are listed for 1363 reports, articles, and other documents introduced into the NASA scientific and technical information system between January 1, 1991 and July 31, 1992. Topics covered include technology development and mission design according to system, interactive analysis and design, structural and thermal analysis and design, structural concepts and control systems, electronics, advanced materials, assembly concepts, propulsion and solar power satellite systems

    Large space structures and systems in the space station era: A bibliography with indexes

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    Bibliographies and abstracts are listed for 1372 reports, articles, and other documents introduced into the NASA scientific and technical information system between January 1, 1990 and June 30, 1990. Its purpose is to provide helpful information to the researcher, manager, and designer in technology development and mission design according to system, interactive analysis and design, structural and thermal analysis and design, structural concepts and control systems, electronics, advanced materials, assembly concepts, propulsion, and solar power satellite systems

    Large space structures and systems in the space station era: A bibliography with indexes (supplement 04)

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    Bibliographies and abstracts are listed for 1211 reports, articles, and other documents introduced into the NASA scientific and technical information system between 1 Jul. and 30 Dec. 1991. Its purpose is to provide helpful information to the researcher, manager, and designer in technology development and mission design according to system, interactive analysis and design, structural concepts and control systems, electronics, advanced materials, assembly concepts, propulsion, and solar power satellite systems

    Dynamical systems : mechatronics and life sciences

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    Proceedings of the 13th Conference „Dynamical Systems - Theory and Applications" summarize 164 and the Springer Proceedings summarize 60 best papers of university teachers and students, researchers and engineers from whole the world. The papers were chosen by the International Scientific Committee from 315 papers submitted to the conference. The reader thus obtains an overview of the recent developments of dynamical systems and can study the most progressive tendencies in this field of science

    Design of a composite morphing wing

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    Morphing aircraft components can increase the possibility of optimising the performance of an aircraft at various flight conditions. A morphing aircraft wing can change the wing shape to modify the lift and drag distribution on the wing surface, allowing the lift-to-drag ratio to be tailored to the desired performance. A camber morphing and a trailing edge morphing wing changes the aerodynamic lift by altering the camber and by deflecting the wing trailing edge, potentially reducing the aerodynamic drag by eliminating the gaps; which exist between the main wing and the control surfaces of a conventional wing. Among the technology used to achieve camber morphing and trailing edge morphing, were mechanical and smart actuations, such as piezoelectrics and shape memory alloys (SMAs). Compliant structures, cellular structures, shape memory polymers, and multi-stable structures were exploited to improve the flexibility of the aerofoil sections or wings. SMA wires were one of the smart actuators which had been extensively utilised to morph various aerofoils/wings, mainly due to the high actuation force and compatibility, which reduce the volume and weight of the actuators and the complexity of moving mechanical components. In this research, a user defined material model (UMAT) was developed within the explicit LS-DYNA FE code, for NiTi shape memory alloy (SMA) wires, and used for actuation of the composite morphing wing. The Tanaka SMA constitutive model was implemented in MATLAB and FORTRAN codes for the SMA-actuation of various structures. The UMAT was used to simulate actuations of various complex morphing structures, including several aluminium and composite aerofoils with corrugated sections, and a pre-curved corrugated plate. Actuations of the two aluminium aerofoils, with corrugated sections in the lower surface and the middle cantilever section, by a 0.5mm-diameter SMA wire with a maximum recoverable strain or a pre-strain of 1.6%, resulted in trailing edge (TE) deflections of 7.8 mm and 65.9 mm, respectively. Actuation of the carbon fibre (CF) composite aerofoil, with the corrugated section as a middle cantilever section, and with 8 layers of CF in ±45° directions, produced a TE deflection of 52.0 mm. To demonstrate the SMA-actuated morphing concept, a composite 3D-printing technology was explored to manufacture a carbon fibre (CF) composite structure, consisted of a flat vertical front plate, a corrugated section, and a rear trailing edge (TE) section. Due to the nature of 3D-printing, two layers of CF were 3D-printed along the circumference of the corrugation and the TE section, and the minimum thickness of the structure was 3 mm. Experimentally, actuation of the CF composite corrugated structure by a NiTi SMA wire with a diameter of 0.2 mm and a pre-strain of 4.77%, and with a diameter of 0.5 mm and a pre-strain of 1.68%, aligned in the chordwise direction, resulted in 1.1 mm and 6.0 mm TE deflections, respectively. Cyclic tests (10 and 30 cycles) of the actuation of the CF composite corrugated structure showed the TE deflection converged after few cycles. A 1.25m-span composite morphing wing was finally designed and manufactured, consisted of a CF composite D-nose spar which resisted the main aerodynamic loading, and rear sections which were made of rigid and flexible foams. CF composite spar flanges, spar web, front and rear ribs, were 3D-printed, and were assembled with a CF composite skin which was autoclave-manufactured, to form the CF composite D-nose spar. Sections of rigid and flexible foams were CNC-machined and were attached to the front CF composite D-nose spar, 3D-printed long rear ribs, trailing edge sections and the morphed corrugated structure, to form a complete composite morphing wing.Open Acces
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