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1
Stamp, A. R. D. "Extending the performance and bandwidth of electromechanical devices." Thesis, University College London (University of London), 2012. http://discovery.ucl.ac.uk/1362646/.
Повний текст джерелаАнотація:
Electromechanical devices are used in a wide range of dynamic applications, from hard disk drives to levitating trains; therefore any improvements in the dynamic performance of such devices would be of significant academic and commercial benefit. This thesis presents theoretical and experimental analyses of shorted turns (conductive loops inductively coupled to a coil). The effect of shorted turn design parameters was investigated using electromagnetic actuator models, measuring force and electrical impedance, with the aims of increasing dynamic range and stability. It was found that a shorted turn reduces the motor constant at high frequencies; it does however significantly improve the transient response of the total coil current. This would suggest that although a shorted turn is likely to reduce the peak force, with the correct shorted turn configuration an increase in acceleration may be apparent; this would be particularly beneficial for positioning actuators with fast response time, such as those found within hard disk drives. A shorted turn was also found to provide damping, attributed to eddy-currents, which reduced resonance in tests. Utilising an inductively-coupled secondary coil it was possible to control the shorted turn effect, switching it on and off as desired. This could be applied in practice: the shorted turn could be passive in the acceleration phase and active in the deceleration phase, potentially leading to improvements in the dynamic performance.
2
Abu-El-Haija, Wejdan Saleh Jaber. "Transient performance of small salient pole alternators." Thesis, Queen's University Belfast, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.301750.
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3
Tamjis, Mohamad Rom Bin. "Computation of switched reluctance motor design and performance." Thesis, University of Newcastle Upon Tyne, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.386710.
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4
Klügl, Volker Bernd. "Performance prediction model for positive displacement helical screw flowmeters." Thesis, University of South Wales, 1998. https://pure.southwales.ac.uk/en/studentthesis/performance-prediction-model-for-positive-displacement-helical-screw-flowmeters(c20f2f40-d33c-4424-b27f-b9e44bfab287).html.
Повний текст джерелаАнотація:
A general model is developed describing the performance of positive displacement flowmeters. This model allows to predict the performance of any positive displacement meter if 8 coefficients describing the meter design are known. The logic is that a flowmeter performs at a defined pressure loss for a given speed. This pressure loss times flowrate is then energy balanced against all internal loses. Pressure loss and speed are the reasons for leakage. Rotational speed times the theoretical swept volume is the theoretical flowrate and this flowrate, when combined with leakage flow can be used to calculate the effective or true flowrate. The 8 coefficients describe the influence of the design of a meter on laminar leakage flow, turbulent leakage flow, speed related leakage flow, viscous friction, mechanical friction, constant friction, impulse energy losses and ball bearing friction, respectively. This model was applied to a twin-screw type displacement flowmeter which uses two helical rotors which form separate pockets and allow the flow-rate of the fluid to be measured. Based on the general prediction model it was found that for this type of flowmeter mainly two coefficients are the reasons for deviation from linearity. These are the constant friction power losses KC produced by mechanical sliding and the turbulent leakage flow losses Kt ur . When the values of KC and Ktur are zero then the error against flowrate is constant. A complete model of an actual twin-screw type displacement flowmeter was realised, determining all 8 loss coefficients. In order to do so, tests with a twin-screw type displacement flowmeter have been carried out on the overall meter performance, leakage flow losses and bearing friction. The theoretical work includes the determination of all 8 coefficients based on a study of the rotor geometry of the meter and a calculation of the fluid forces and torques acting on the rotors. The theoretical results of the final performance prediction model were compared with experimental results and show a good accordance. It was found that one optimal circumference clearance value can be determined for every different fluid property and flowrate. The flowmeter performance may be increased by minimising mechanical sliding and turbulent leakage flow losses.
5
Monkhouse, Peter. "Design and analysis of a high performance brushless DC drive." Thesis, University of Sheffield, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.389485.
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6
Müller, Markus Anton. "Improved calculation methods for particular aspects of induction motor performance." Thesis, University of Cambridge, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.239100.
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7
Ertugrul, Nesimi. "Position estimation and performance prediction for permanent-magnet motor drives." Thesis, Online version, 1993. http://ethos.bl.uk/OrderDetails.do?did=1&uin=uk.bl.ethos.357041.
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8
Wong, J. N. H. "Novel techniques for improving the performance of MESFET power amplifiers." Thesis, University of Surrey, 2003. http://epubs.surrey.ac.uk/843448/.
Повний текст джерелаАнотація:
This thesis describes the research activities that have been investigated for improving the 3rd order intermodulation distortion products (IM3) and power added efficiency (PAE) and bandwidth performance of microwave GaAs MESFET power amplifiers. Two novel circuit techniques, one for improving the 3dB bandwidth performance and the other for improving the IM3 and PAE performance, were proposed and verified through simulation and practical measurements. The technique of including lumped elements matching networks within the package encapsulation (Close-to-Chip lumped element matching) of a 2GHz MESFET device is described for the first time. Simulation results showed that the amplifier using this technique had a 3dB bandwidth 3 times wider than the amplifier with Off-Chip distributed element matching. The linearity and efficiency performance of a 2GHz MESFET was improved significantly by presenting a difference frequency shunt short-circuit termination across the drain terminal. A 16dB reduction in IM3 and an improvement of 4% in PAE performance was measured on the bench. Success with this technique was further demonstrated with digitally modulated signals.
9
Stevenson, Deja Lee. "Whole-Body Vibration and Its Effects on Electromechanical Delay and Vertical Jump Performance." Diss., CLICK HERE for online access, 2005. http://contentdm.lib.byu.edu/ETD/image/etd867.pdf.
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10
Ng, Ka Ian. "Optimization of automotive engine power performance under numerical and nominal data." Thesis, University of Macau, 2008. http://umaclib3.umac.mo/record=b1942992.
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11
Fathi, S. Hamid. "The performance of brushless DC drives with alternative torque control methods." Thesis, University of Newcastle Upon Tyne, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.315569.
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12
Amin, I. A. M. "Some of the effects of the permeability distribution on induction motor performance." Thesis, University of Leeds, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.371839.
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13
Akmese, Recep. "Design, operation and dynamic performance of a brushless DC tubular drive system." Thesis, University of Bath, 1989. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.328876.
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14
Shi, Zhe. "A Comparative Study of Performance Assessment and Fault Diagnosis Approaches for Reciprocating Electromechanical Mechanism." University of Cincinnati / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1468512813.
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15
Halimic, Mirsad Kjazim. "Performance improvement of dynamic weighing systems using optimal control and advanced signal processing methods." Thesis, Brunel University, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.249791.
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16
Safi, Sabah Kati. "Analysis and simulation of the high-speed torque performance of brushless D.C. motor drives." Thesis, University of Newcastle Upon Tyne, 1994. http://hdl.handle.net/10443/367.
Повний текст джерелаАнотація:
The work presented in this thesis is concerned with the analysis, modelling, simulation and control of a surface mounted permanent magnet motor supply by a voltage controlled Pulse-Width Modulation (PWM) inverter. In Chapter 1 an overall description of the design and construction of individual components of the brushless dc drive system is presented along with a review of the general concept of the drive system. This type of machine is compared with other types of machine and the potential advantages of this new concept, both technical and economic, outlined. In Chapter 2 the operation and the control aspects of the brushless dc motor are described, with particular emphasis placed on the basic requirements for the operation, torque production, performance characteristic and control. The high-speed torque control methods are also described and their merits are reviewed. In addition the effects of different parameters of machine design on the torque-speed characteristics are discussed. Chapter 3 elaborates on the analysis and simulation work by presenting a comprehensive analysis which aims to show that direct three-phase representation can be used as an effective tool for performance assessement of brushless dc drive systems operating over a wide speed range. In Chapter 4 the performance of the brushless dc motor supplied by a PWM inverter with a view to improving the high-speed torque performance is investigated. Simulation and analysis of the brushless dc motor is presented in which the actual parameters of the experimental machine are used. The aim of the analysis is to simulate a brushless d. c. drive system operating in closed-loop control modes, which use high speed torque control techniques in conjunction with a PWM control technique. A detailed analytical model which makes possible the use of machine theory for representing the performance of the brushless dc motor is presented in Chapter 5. The method utilizes the phasor diagram, where machine performance in terms of the main control variables such as voltage and phase advance angle is demonstrated. Chapter 5 also presents an analytical expression for the phase-advance angle which yields maximum torque at a given motor speed. An analytical study concerning the optimum phase advance is developed in Chapter 6. In this work two analytical approaches to the problem of obtaining an optimum phase advance angle are presented. Chapter 6 presents a detailed analysis of the shape of the current and back-emf waveforms in a trapezoidal brushless dc motor drive and their effects on the torque/speed performance. Chapter 7 presents the implementation of a microprocessor based system, which can set the phase advance angle to its optimum value at any motor speed. This implementation is done in real time on the protortype drive using a TMS320C30 digital signal processor. Features of the method proposed in this thesis include the estimation algorithms for predicting the time advance. Experimental results on a drive system demonstrate the satisfactory performance of both the hardware and software of the control scheme.
17
Zhu, Zi-Qiang. "The electromagnetic performance of brushless permanent magnet DC motors : with particular reference to noise and vibration." Thesis, University of Sheffield, 1991. http://etheses.whiterose.ac.uk/2968/.
Повний текст джерелаАнотація:
A comprehensive analytical technique is developed for predicting the instantaneous magnetic field distribution in radial-field, surface-mounted permanent magnet brushless DC motors under any load condition and commutation strategy. It is based on a 2-dimensional analysis in polar coordinates and accounts implicitly for the corresponding stator winding current waveforms and the effect of stator slot openings. In addition, a 2-dimensional analytical method for calculating the back-emf waveform is presented, whilst the analytical technique is applied to the prediction of the cogging torque waveform and the calculation of the self- and mutual-winding inductances. Also developed and validated is an analytical model for predicting the steady-state dynamic performance of a 3-phase brushless DC drive, by exploiting the periodicity in the stator winding voltage and current waveforms, with due account of the influence of commutation events in the inverter bridge, the back-emf waveform, current limiting, and commutation timing etc. The model is developed further to couple with the motion equation of the rotor to enable the transient and steady-state dynamic performance of brushless DC drives to be predicted. The effect of end-shields on the vibrational behaviour of stators is investigated by the modem modal analysis technique, and new formulae for the calculation of the acoustic power radiated by a cylindrical stator of finite length, using an analytical method, are presented. A technique which combines the finite element method and Fourier analysis to account for the effects of end-shields on the acoustic radiation is developed, and the spherical acoustic radiation model of motors has been improved by the application of finite elements. Finally, a systematic analytical approach to the estimation and analysis of the acoustic noise from a radial-field, internal rotor, brushless DC motor is presented.
18
Miller, Justin (Justin Lee). "Simulation of a novel electromechanical engine valve drive to quantify performance gains in fuel consumption." Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/67767.
Повний текст джерелаАнотація:
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2011.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 67-68).
This thesis describes the modeling and simulation of a novel electromechanical valve drive known as the MIT EMV. This valve drive allows an engine to achieve variable valve timing which has been shown to produce improvements in engine fuel efficiency. To test this improvement, a reference engine model with fixed valve timing was obtained from the engine simulation software package WAVE® by Ricardo. A model of the MIT EMV was generated based on the details of the physical actuator, and it was incorporated into the WAVE® engine model. An interface between MATLAB® and WAVE® was developed for simulating the actuator at desired engine speeds and loads. Specific test points were chosen based on corporate operating points and operating points that were used to test the BMW Valvetronic actuator. Through simulation, it was determined that the MIT EMV can provide a reduction of approximately 10% in fuel consumption at the corporate operating points when compared to the reference engine model. The drive was also able to achieve performance gains similar to the BMW Valvetronic actuator, showing that it is able to compete with other actuators on the market even without variable lift capabilities.
by Justin Miller.
S.M.
19
Kwangwaropas, Mongkol. "An electromechanical aid for improving the performance of tractor drivers in post establishment row-crop operations." Thesis, Cranfield University, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.241240.
Повний текст джерела
20
Gago, Paulo. "Post activation potentiation : Modulating factors and mechanisms for muscle performance." Doctoral thesis, Gymnastik- och idrottshögskolan, GIH, Laboratoriet för biomekanik och motorisk kontroll (BMC), 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:gih:diva-4280.
Повний текст джерелаАнотація:
Introduction: Acute enhancements of muscle contractile properties and performance subsequent to a maximal or near maximal conditioning contraction are often termed post activation potentiation (PAP). Although still controversial, PAP is commonly linked to enhancements in the myosin regulatory light chain phosphorylation, leading to improvements in the excitation–contraction coupling. The PAP seen after a conditioning task often coexists with fatigue and is known to depend on strength level, muscle fiber type and age. Less is known about how factors such as static and dynamic changes in muscle length affect PAP, and on the relative contribution of contractile and tensile components to PAP. Aim: To enhance our understanding of how, and under what conditions, a single maximal isometric contraction affects plantar flexor muscle contractile performance, and other muscle tendon properties, in power athletes. Methods: Supramaximal twitches were evoked via electrical stimulation of the tibial nerve of athletes before and on several occasions after a 6-second maximal voluntary isometric contraction (6-s MVIC) in both static muscle, and during passive muscle lengthening and shorting at different angular velocities. Several contractile variables were measured from the twitches. The effects of a 6-s MVIC on Achilles tendon stiffness was calculated from torque and ultrasonography based measurements of tendon length at two submaximal contraction intensities. Overall stiffness index was calculated by analyzing the passive lengthening torque/angle curve.Results: A single MVIC enhanced muscle contractile properties and electromechanical delay for up to 5 minutes. Plantar flexor twitch variables such as peak twitch, rate of torque development and rate of torque relaxation were enhanced during shortening compared to lengthening muscle actions, and in an extended as compared to a flexed knee position. Achilles tendon stiffness and overall stiffness index were not significantly modulated by a single 6-s MVIC. Conclusion: The results of this thesis imply that functional enhancements from a 6-s conditioning MVIC would mainly come from improvements in contractile rather than tensile components. Stiffness changes should be monitored in future PAP-related studies since they may still occur after more extensive conditioning protocols than the current one. Improvements in contractile components subserving muscle strength after a conditioning MVIC suggests that enhancements in muscle power after a conditioning task should be greatest in fast concentric muscle actions, though still present in muscle lengthening. Conditioning should be performed in a position where full activation is easy to achieve and tailored to mach an athlete or group of athlete’s current status and characteristics, maximizing performance in a specific sport event.The project recived financial support from the Swedish National Centre for Research in Sports (CIF). Paulo Gago also wishes to thank the Fundação para a Ciência e Tecnologia (FCT), Portugal for the Ph.D. Grant (SFRH/BD/103572/2014).
New version 2015-01-25 updates the previous one by correcting the errors described in the correction list file (errata).
Doctoral project: Post activation potentiation - Modulating factors and mechanisms for muscle performance.
21
Bindl, Jared C. "Multi-pole permanent magnet motor design and control for high performance electromechanical actuation in all electric aircraft." Honors in the Major Thesis, University of Central Florida, 2010. http://digital.library.ucf.edu/cdm/ref/collection/ETH/id/1359.
Повний текст джерелаАнотація:
This item is only available in print in the UCF Libraries. If this is your Honors Thesis, you can help us make it available online for use by researchers around the world by following the instructions on the distribution consent form at http://library.ucf.edu/Systems/DigitalInitiatives/DigitalCollections/InternetDistributionConsentAgreementForm.pdf You may also contact the project coordinator, Kerri Bottorff, at kerri.bottorff@ucf.edu for more information.Bachelors
Engineering and Computer Science
Electrical Engineering
22
Buckthorpe, Matthew. "Neural contributions to maximal muscle performance." Thesis, Loughborough University, 2014. https://dspace.lboro.ac.uk/2134/14772.
Повний текст джерелаАнотація:
Neural activation is thought to be essential for the expression of maximal muscle performance, but the exact contribution of neural mechanisms such as the level of agonist, antagonist and stabiliser muscle activation to muscle strength is not fully understood. Explosive neuromuscular performance, including the ability to initiate (the electromechanical delay, EMD) and develop force rapidly (termed, rate of force development, RFD) are considered essential for the performance of explosive sporting tasks and joint stabilisation and thus injury avoidance. The thesis aimed to improve our understanding of the contribution of neural factors to muscle performance, with a specific focus on explosive neuromuscular performance. The work in this thesis utilised a range of approaches to achieve this aim. Initially, the association between muscle activation and rate of force development and EMD was established. Comparison of unilateral and bilateral actions was then undertaken. Finally interventions with the aim to both negatively affect and improve muscle strength, which included fatigue and resistance training (RT), respectively was undertaken and the neural contributions to changes in performance established. Agonist activation during the early phase of voluntary force production was shown to be an important determinant of voluntary EMD, explaining 41% of its inter-individual variability. Agonist activation was an important determinant of early, but not late phase RFD. Use of bilateral actions resulted in a reduction in explosive strength, which was thought to be due to differences in postural stability between unilateral and bilateral strength tasks. The level of stabiliser activation was strongly related to the level of agonist activation during the early phase of explosive force development and had a high association with explosive force production. Task-specific adaptations following isoinertial RT, specifically, the greater increase in isoinertial lifting strength than maximal isometric strength were due to training-specific changes in the level of agonist activation. High-intensity fatigue achieved a more substantial decline in explosive than maximal isometric strength, and this was postulated to be due to neural mechanisms, specifically decreased agonist activation. This work provides an in depth analysis of the neural contributions to maximal muscle performance.
23
Schwartz, Robert Lee. "Vestibular and Electromagnetic Stimulation: Their Effects on Intellectual Performance and Mood State." Thesis, University of North Texas, 1991. https://digital.library.unt.edu/ark:/67531/metadc332751/.
Повний текст джерелаАнотація:
In the present study, the Electromechanical Therapeutic Apparatus was examined to determine the extent to which its repeated use can influence intellectual performance and mood state. The Electromechanical Therapeutic Apparatus is a device designed to mildly stimulate the body and brain, while facilitating relaxation. Its three components include a rotating platform-bed; a weak, extremely-low-frequency, external-electric field; and music. In the present study, three groups were contrasted, a music-only group which served as a placebo; a group which combined motion-vestibular stimulation and music; and a group which combined motion-vestibular stimulation and music with an externalelectric field. The sample included 33 randomly selected men and women whose average age was 34.6 years.
24
Sastrosubroto, Ashwin S. "A study of the effect of harmonics in the system on the performance of residual current-operated circuit-breakers and electromechanical overcurrent relays." Thesis, Aston University, 1989. http://publications.aston.ac.uk/8069/.
Повний текст джерелаАнотація:
Residual current-operated circuit-breakers (RCCBs) have proved useful devices for the protection of both human beings against ventricular fibrillation and installations against fire. Although they work well with sinusoidal waveforms, there is little published information on their characteristics. Due to shunt connected non-linear devices, not the least of which is the use of power electronic equipment, the supply is distorted. Consequently, RCCBs as well as other protection relays are subject to non-sinusoidal current waveforms. Recent studies showed that RCCBs are greatly affected by harmonics, however the reasons for this are not clear. A literature search has also shown that there are inconsistencies in the analysis of the effect of harmonics on protection relays. In this work, the way RCCBs operate is examined, then a model is built with the aim of assessing the effect of non-sinusoidal current on RCCBs. Tests are then carried out on a number of RCCBs and these, when compared with the results from the model showed good correlation. In addition, the model also enables us to explain the RCCBs characteristics for pure sinusoidal current. In the model developed, various parameters are evaluated but special attention is paid to the instantaneous value of the current and the tripping mechanism movement. A similar assessment method is then used to assess the effect of harmonics on two types of protection relay, the electromechanical instantaneous relay and time overcurrent relay. A model is built for each of them which is then simulated on the computer. Tests results compare well with the simulation results, and thus the model developed can be used to explain the relays behaviour in a harmonics environment. The author's models, analysis and tests show that RCCBs and protection relays are affected by harmonics in a way determined by the waveform and the relay constants. The method developed provides a useful tool and the basic methodology to analyse the behaviour of RCCBs and protection relays in a harmonics environment. These results have many implications, especially the way RCCBs and relays should be tested if harmonics are taken into account.
25
Zhang, Yi. "High performance DSP-based servo drive control for a limited-angle torque motor." Thesis, Loughborough University, 1997. https://dspace.lboro.ac.uk/2134/6768.
Повний текст джерелаАнотація:
This thesis describes the analysis, design and implementation of a high performance DSP-based servo drive for a limited-angle torque motor used in thermal imaging applications. A limited-angle torque motor is an electromagnetic actuator based on the Laws' relay principle, and in the present application the rotation required was from - 10° to + 10° in 16 ms, with a flyback period of 4 ms. To ensure good quality picture reproduction, an exceptionally high linearity of ±0.02 ° was necessary throughout the forward sweep. In addition, the drive voltage to the exciting winding of the motor should be less than the +35 V ceiling of the drive amplifier. A research survey shows that little literature was available, probably due to the commercial sensitivity of many of the applications for torque motors. A detailed mathematical model of the motor drive, including high-order linear dynamics and the significant nonlinear characteristics, was developed to provide an insight into the overall system behaviour. The proposed control scheme uses a multicompensator, multi-loop linear controller, to reshape substantially the motor response characteristic, with a non-linear adaptive gain-scheduled controller to compensate effectively for the nonlinear variations of the motor parameters. The scheme demonstrates that a demanding nonlinear control system may be conveniently analysed and synthesised using frequency-domain methods, and that the design techniques may be reliably applied to similar electro-mechanical systems required to track a repetitive waveform. A prototype drive system was designed, constructed and tested during the course of the research. The drive system comprises a DSP-based digital controller, a linear power amplifier and the feedback signal conditioning circuit necessary for the closed-loop control. A switch-mode amplifier was also built, evaluated and compared with the linear amplifier. It was shown that the overall performance of the linear amplifier was superior to that of the switch-mode amplifier for the present application. The control software was developed using the structured programming method, with the continuous controller converted to digital form using the bilinear transform. The 6- operator was used rather than the z-operator, since it is more advantageous for high speed sampling systems. The gain-scheduled control was implemented by developing a schedule table, which is controlled by the DSP program to update continuously the controller parameters in synchronism with the periodic scanning of the motor. The experimental results show excellent agreement with the simulated results, with linearity of ±0.05 ° achieved throughout the forward sweep. Although this did not quite meet the very demanding specifications due to the limitations of the experimental drive system, it clearly demonstrates the effectiveness of the proposed control scheme. The discrepancies between simulated and experimental results are analyzed and discussed, the control design method is reviewed, and detailed suggestions are presented for further work which may improve the drive performance.
26
Gonzalez, Minerva. "Impact of Li non-stoichiometry on the performance of acoustic devices on LiTaO3 and LiNbO3 single crystals." Thesis, Besançon, 2016. http://www.theses.fr/2016BESA2007/document.
Повний текст джерелаАнотація:
Les technologies de filtres, résonateurs, oscillateurs et capteurs sont des éléments essentiels dans lesindustries des télécommunications, automobile, militaire, médical, etc. Les monocristaux de LiTaO3 (LT) etLiNbO3 (LN) sont les matériaux les plus utilisés pour la fabrication de filtres de radiofréquence à ondesélastiques des téléphones portables, car ils possèdent un facteur de couplage électromécanique (K2) élevé.Cependant, ils présentent une problématique liée à la variation de la fréquence de fonctionnement avec latempérature (CTF), dont la valeur est environ de -40 à -95 ppm/°C. D’autre part, il a été démontré dans lalittérature que les propriétés de LT et LN changent avec la non-stoechiométrie du Li.L’objectif de cette thèse a été l’étude de l’effet de la concentration en Li2O sur la performance desdispositifs acoustiques à ondes élastiques de surface, utilisant comme substrat piézoélectrique desmonocristaux de LT coupe YXl/42 (42 RY-LT) et LN coupe YXl/128 (128 RY-LT). Cette étude vise àl’amélioration du CTF sans la dégradation d’autres propriétés (K2 et pertes d’insertion) dans le cas du 42 RYLTet la stabilité de dispositifs utilisés à haute densité de puissance dans le cas du 128 RY-LN. Tout d’abord,nous avons préparé des monocristaux de LT et LN avec différente concentration en Li2O :48.5-50 mol%, enutilisant la méthode d’équilibration par transport en phase vapeur (VTE). Ensuite, nous avons fabriqué etcaractérisé des dispositifs à ondes élastiques de volume et de surface à base de LT et LN, traités par VTE, afind’étudier l’effet de la non-stoechiométrie de Li et l’effet des domaines ferroélectriques sur leur performanceThe filter technologies, resonators, oscillators and sensors are essential elements fortelecommunications, automotive, military, medical industries. The most of radio frequency surface acousticwave (RF-SAW) filters, present in mobile phones, are based in LiNbO3 (LN) and LiTaO3 (LT) single crystalsbecause they have high electromechanical coupling factor (K2). However, these materials have a problemrelated to the variation of the operating frequency with temperature (TCF), whose value is about -40 to -95ppm / ° C. On the other hand, it has been previously shown in the literature that the physical and structuralproperties of LT and LN change with Li non-stoichiometry, including elastic properties.The aim of this work was the investigation of the impact of Li2O concentration on the performance ofSAW devices based on YXl/42 (42 RY-LT) and YXl/128 (128 RY-LN) single crystals. In the case of 42 RY-LT,we focused in the reduction of TCF without the degradation of other properties (K2 and insertion losses) andin the case of 128 RY-LN crystals we focused in the stability of devices at high power densities. First, singlecrystals of LT and LN with different Li2O concentration: 48.5-50 ml% were prepared, by using the VaporTransport Equilibration (VTE) method. Afterwards, SAW and bulk acoustic wave (BAW) devices based on LTand LN VTE treated crystals, were fabricated and characterized, in order to study the effect of Li nonstoichiometryand the effect of ferroelectric domains on the performance of devices
27
Scarisbrick, C. "Improving the thermal performances of domestic electric ovens." Thesis, Cranfield University, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.283267.
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28
Gendrin, Martin. "Contribution au développement d'une mini-pelle tout-électrique : Approche prédictive pour la commande efficace et compliante des actionneurs électromécaniques." Thesis, Lyon, 2016. http://www.theses.fr/2016LYSEI050/document.
Повний текст джерелаАнотація:
Les actionneurs électromécaniques supplantent les solutions d’actionnement hydrauliques concurrentes dans un nombre croissant d’applications industrielles, particulièrement en aéronautique. Ils le doivent à leurs rendements élevés et à une relative simplicité de commande. Fort de ces avantages, cette technologie a été mise en place dans le cadre du projet ELEXC, en vue de remplacer les vérins hydrauliques sur une mini-excavatrice tout-électrique et s’attaquant pour la première fois au secteur du bâtiment et des travaux publics. Cependant, cette intégration s’accompagne de doutes sur la performance et la durabilité de ces actionneurs dans ce cas précis d’utilisation. Pour répondre à ces interrogations, ce manuscrit se focalisera dans un premier volet sur la caractérisation des performances d’une structure spécifique, permise par la mise en place d’un banc de test multi-énergies instrumenté. Cette étude aboutira à la mise en place d’un modèle par lois physiques dont les paramètres auront été identifiés expérimentalement.Deux solutions innovantes vont ensuite être proposées, visant respectivement à réduire les répercussions, notamment énergétiques, de la caractéristique discrète du convertisseur à découpage, et à parer au manque de compliance de l’actionneur tout en conservant ses capacités de creusage. Elles seront toutes deux associées au concept de commande prédictive, mais offriront chacune une spécificité par rapport à l’implémentation standard de ce type de commande tout en conservant ses avantages. La première prendra la forme d’un modulateur fondé sur le principe d’une modulation de largeur d’impulsion vectorielle, dont la séquence sera sélectionnée par un contrôleur prédictif en rapport avec une fonction de coût alliant les ondulations de courant, les pertes par commutation et la tension de mode commun spécifiques aux séquences. La seconde consistera en un contrôleur d’impédance à boucle de position interne, dont les paramètres d’impédance seront variables et définis par un contrôleur prédictif afin de permettre une bonne pénétration dans l’environnement tout en limitant la dynamique et la valeur maximale de l’effort de compression sur la transmissionNowadays, the electro-mechanical actuators (EMA) are seen as an alternative to the conventional hydraulic cylinders in a growing number of industrial applications, including the aeronautic sector, thanks to their high efficiency and relatively simple commandability. According to this features, this actuator technology was selected to replace the hydraulic cylinders of the actuation system of a full-electric compact excavator in the ELEXC project. However, some concerns arose from the lack of existing examples with EMA functioning in relatively severe working conditions implying collisions of the actuators with stiff environments. Therefore, this manuscript will first focus on the characterization of the electro-mechanical actuator and of its performances in this specific case of application, enabled by the development of a multi-energy test-rig. Beside the validation of the EMA capacities, a physic law model will be developed, and its parameters tuned according to the experimental results. In a second part of this manuscript, two novel control laws will be proposed, aiming respectively to reduce the negative repercussions of the discrete characteristic of the electrical converter, and to counterpart the lack of natural compliance of the mechanical actuator. They will be both based on the concept of predictive control, but will differ from the conventional implementation of this type of controller. The first proposed topology is a modulator based on a vector Pulse Width Modulation, in which the PWM sequence to be used is defined online by a predictive controller according to a cost function that takes into account the current ripples, the switching losses and the common mode voltages specific to the sequences. Next, a position-based impedance controller, whose impedance parameters are defined online by a predictive controller, is introduced, in order to enable the EMA to penetrate a stiff environment with a relatively low dynamic increase of compression force on the mechanical transmission
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Олексенко, Сергій Володимирович. "Оцінка показників лінійних електромеханічних перетворювачів ударної дії з високою магнітною сумісністю". Thesis, НТУ "ХПІ", 2016. http://repository.kpi.kharkov.ua/handle/KhPI-Press/21227.
Повний текст джерелаАнотація:
Дисертація на здобуття наукового ступеня кандидата технічних наук за спеціальністю 05.09.01 – електричні машини та апарати. – Національний технічний університет "Харківський політехнічний інститут", Харків, 2016.
Дисертацію присвячено розробці комплексу науково-технічних рішень, спрямованих на оцінку показників лінійних електромеханічних перетворювачів ударної дії з високою магнітною сумісністю. Запропонована імітаційна математична модель лінійного електромеханічного перетворювача ударної дії, що описує взаємопов'язані просторово-часові електричні, магнітні, механічні та теплові процеси із змінними параметрами. Визначено геометричні параметри електропровідного якоря, феромагнітних осердя та екрана, при яких перетворювач забезпечує найбільші показники. Отримала подальший розвиток методика синтезу параметрів високоефективного лінійного електромеханічного перетворювача ударної дії, заснована на використанні комплексного критерію ефективності, який враховує основні показники при різних варіантах стратегії вибору. Встановлено, що кріогенне охолодження до температури рідкого азоту обмотки індуктора дозволяє збільшити ККД лінійних електромеханічних перетворювачів ударної дії в 1,6 раз, при охолодженні якоря – в 5 разів, а при одночасному їх охолодженні – в 11 разів. Розроблено конструктивні схеми лінійних електромеханічних перетворювачів ударної дії індукційно-електромагнітного типу ударної і ударно-поворотної дії. Розроблено методику експериментальних досліджень лінійних електромеханічних перетворювачів ударної дії з одночасним вимірюванням електричних і механічних показників.The thesis for the degree of candidate of technical sciences, specialty 05.09.01 – electrical machinery and apparatus. – National technical university "Kharkiv polytechnic institute", Kharkіv, 2016. The thesis is devoted to development of complex scientific and technical solutions aimed at improving the efficiency linear electromechanical transducers with high magnetic compatibility. The proposed computer model linear electromechanical transducers with ferro-magnetic core, describing connected field-temporal electrical, magnetic, mechanical and thermal processes with variable parameters. The optimum form of section and parameters conductive anchor linear electromechanical transducers induction type. The influence of the configuration and geometrical parameters ferromagnetic core, ferromagnetic shield, electromagnetic shield and combined on screen indicators linear electromechanical transducers. Further developed methods of synthesis parameters highly linear electromechanical transducers, based on a comprehensive criteria. The effect of cryogenic cooling efficiency linear electromechanical transducers. Developed design schemes linear electromechanical transducers electromagnetic induction-type. The method of experimental studies linear electromechanical transducers simultaneous measurement of electrical and mechanical performance. Experimentally confirmed the basic theoretical training is shown linear electromechanical transducers efficiency.
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Олексенко, Сергей Владимирович. "Оценка показателей линейных электромеханических преобразователей ударного действия с высокой магнитной совместимостью". Thesis, НТУ "ХПИ", 2016. http://repository.kpi.kharkov.ua/handle/KhPI-Press/21235.
Повний текст джерелаАнотація:
Диссертация на соискание ученой степени кандидата технических наук по специальности 05.09.01 – электрические машины и аппараты. – Национальный технический университет "Харьковский политехнический институт", Харьков, 2016.
Диссертация посвящена разработке комплекса научно-технических решений, направленных на оценку эффективности линейных электромеханических преобразователей ударного действия с высокой магнитной совместимости. На основе анализа научно-технических источников установлено, что линейные электромеханические преобразователи ударного действия широко при-меняются в ударно-силовых устройствах и для ускорения объектов до высоких скоростей. Однако КПД существующих линейных электромеханических преобразователей ударного действия находится на низком уровне. Кроме того, во время работы линейных электромеханических преобразователей ударного действия последние создают очень значительные импульсные магнитные поля рассеяния, которые резко негативно влияют на близко расположенное оборудование и экологическую чистоту для биологических объектов. Предложена имитационная математическая модель линейного электроме-ханического преобразователя ударного действия, описывающая взаимосвязанные пространственно-временные электрические, магнитные, механические и тепловые процессы с переменными параметрами. Определены геометрические параметры электропроводящего якоря, ферромагнитных сердечника и экрана, при которых преобразователь обеспечивает наибольшие показатели. Предложена конструкция комбинированного экрана, обеспечивающего снижение магнитных полей рассеяния до 4 раз по сравнению с ферромагнитным экраном.The thesis for the degree of candidate of technical sciences, specialty 05.09.01 – electrical machinery and apparatus. – National technical university "Kharkiv polytechnic institute", Kharkіv, 2016. The thesis is devoted to development of complex scientific and technical solutions aimed at improving the efficiency linear electromechanical transducers with high magnetic compatibility. The proposed computer model linear electromechanical transducers with ferro-magnetic core, describing connected field-temporal electrical, magnetic, mechanical and thermal processes with variable parameters. The optimum form of section and parameters conductive anchor linear electromechanical transducers induction type. The influence of the configuration and geometrical parameters ferromagnetic core, ferromagnetic shield, electromagnetic shield and combined on screen indicators linear electromechanical transducers. Further developed methods of synthesis parameters highly linear electromechanical transducers, based on a comprehensive criteria. The effect of cryogenic cooling efficiency linear electromechanical transducers. Developed design schemes linear electromechanical transducers electromagnetic induction-type. The method of experimental studies linear electromechanical transducers simultaneous measurement of electrical and mechanical performance. Experimentally confirmed the basic theoretical training is shown linear electromechanical transducers efficiency.
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Gibbs, John H. "Actuated Continuously Variable Transmission for Small Vehicles." University of Akron / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=akron1238819759.
Повний текст джерела
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McFarland, Kyle Alan. "A performance map framework for maximizing soldier performance." Thesis, 2011. http://hdl.handle.net/2152/ETD-UT-2011-05-3201.
Повний текст джерелаАнотація:
Soldiers in the Unites States Army operate under uniquely demanding conditions with increasingly high performance expectations. Modern missions, including counter-insurgency operations in Iraq and Afghanistan, are complex operations. The Army expects this complexity to continue to increase. These conditions affect Soldier performance in combat. Despite spending billions of dollars to provide Soldiers with better equipment to meet the demands of the modern battlefield, the U.S. Army has dedicated comparatively little resources to measuring and improving individual Soldier performance in real-time. As a result, the Army does not objectively measure a Soldier’s performance at any point in their active duty career.
The objective of this report is to demonstrate the utility and feasibility of monitoring Soldier performance in real-time by means of visual 3D performance maps supported by a Bayesian network model of Soldier performance. This work draws on techniques developed at the University of Texas’ Robotics Research Group for increasing performance in electro-mechanical systems. Humans and electro-mechanical systems are both complex and demonstrate non-linear performance trends which are often ignored by simplified analytical models. Therefore, application of empirical Bayesian models with visual presentation of data in 3D performance maps enables rapid understanding of important performance parameters for a specific Soldier. The performance maps can easily portray areas of non-linear performance that should be avoided or exploited, while presenting levels of uncertainty regarding the assessments, thus empowering the individual to make informed decisions regarding control and allocation of resources.
The present work demonstrates the utility of visual performance maps by structuring 19 relatively mature 3D performance maps based on published empirical research data and analytical models related to human performance. Based on a broad review of the literature, the present research evaluated 10 potential physiological indicators, termed biomarkers that correlate with human responses to a select set of stressors, referred to as impact parameters. The 10 evaluated impact parameters affect various components of Soldier performance. The present research evaluated the documentation of these relationships in the existing literature with regard to 9 general Soldier performance measures. Identifying the research supported relationships from biomarkers to impact parameters to Soldier performance measures resulted in a preliminary Bayesian Soldier Performance Model, from which it is possible to create 70 distinct 3D performance maps. Based on the quality of the relationships identified in the reviewed literature, and a contemporary evaluation of existing sensor technology for the related biomarkers, the present research assessed 26 of the potential 70 performance maps as being achievable in the near-term. Continuing development of the Soldier Performance Model (SPM) as proposed in this report has the potential to increase Soldier performance while simultaneously improving Soldier well-being, reducing risk of physical and mental injury, and reducing downstream treatment cost.text
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Chuang, Yung-Sung, and 莊永松. "Dynamic Performance Test of Static Excitation System and Improvement of Electromechanical Mode for Synchronous Generators." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/2k78xt.
Повний текст джерелаАнотація:
博士國立臺灣科技大學
電機工程系
94
In this dissertation, the dynamic performances of the synchronous generators with static excitation systems in the Tong-Shiao Generation Station, which suffers disturbances of voltage flicker, were examined and improved. The parameters of static excitation systems were tuned to enhance the damping of exciter and electromechanical modes. The disturbances to the 161kV bus of the station are caused by the fluctuating reactive power from nearby electric arc furnaces. This had even tripped the generators with static excitation systems because it did not have enough the damping. The measurement and analysis work was finished within four years. Firstly, field test methods have been used to assess the dynamic performance of generators with static excitation systems. A small unit step signal was injected into the reference input terminal of excitation systems to measure and analyze the dynamic responses of the generators under no-load and full-load condition. The dynamic performance conditions are derived from the terminal voltage waveforms of generators. Secondly, least-square-error method was used to identify parameters of the inner-loop regulators in the automatic voltage regulators of static excitation systems and the terminal voltage sensors. The hybrid differential evolution method is used to find the suitable parameters to improve the exciter modes and the electromechanical modes. This paper also serves to investigate the application of hybrid differential evolution method in the tuning of conventional lead-lag phase compensation and output feedback power system stabilizers to enhance damping of electromechanical modes. The results show that the method in this dissertation can improve the dynamic performance of static excitation system and enhance the damping of exciter and electromechanical modes. The conventional lead-lag phase compensation and the output feedback power system stabilizers also can increase the damping of electromechanical modes.
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Deb, Manan. "Systematic Synthesis And Analysis Of Multi-DOF Toggle Mechanisms For Electrical Switches." Thesis, 2012. http://etd.iisc.ernet.in/handle/2005/2494.
Повний текст джерелаАнотація:
Electrical switches are ubiquitous. Performance requirement for a switch is stringent. The operating mechanism mostly decides the performance of an electromechanical switch. However, design of such mechanisms, which involve discontinuous motions, is not much addressed in literature. The present work proposes a systematic procedure to design and analyze toggle based switching mechanisms.
The work defined the toggle phenomenon rigorously, and, based on the behaviour of the toggles, provided a classification scheme for the switch mechanisms. The existing switches fall in two major categories viz., single-toggle and double-toggle switches. The double toggle mechanism is more suitable for high power breaking as it can isolate the system’s behaviour from the operator’s behaviour. The kinematic and geometric attributes of the operating mechanism which affect the toggle sequence and timings have been identified. A systematic simulation based study has been performed to identify the influence of different kinematic and dynamic parameters on the functionality of a double toggle switching mechanism. The influence of the variable moment of inertia and mechanism singularities arising out of introduction of the four bar sub chain on the performance of the system have been studied in detail. It is observed that the performance of the double toggle systems is less susceptible, though not immune to the user behaviour; in extreme scenarios the switching performance could become erratic. The use of an additional spring in an existing system enhanced the system performance; but, connecting the main spring with the coupler link altered the system performance more dramatically. Thus it established that the influence of the kinematic configuration on the performance of a switching mechanism is more pronounced than the dynamic characteristics of a comparable system.
For the ab initio design of double toggle switching mechanisms, necessary structural criteria for a mechanism to exhibit double toggle phenomenon have been identified and verified with various 2 d.o.f. systems. It is also established that any double toggle mechanism cannot be used directly as a switching mechanism; the link dimensions, link arrangements and the stopper locations have to be chosen properly. Towards that end, three necessary kinematic criteria for a switching mechanism are identified. A few mechanisms which satisfy all structural and kinematic criteria are identified; the switching and toggle behaviour of these mechanisms are examined through simulations using Pro/Mechanism. Finally, considering all the conditions a
is constructed with consideration of mass and geometric shape of the links. Thus, it established that the proposed methodology can systematically generate novel, structurally distinct electrical switches.