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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
21

Výzkum v oblasti anhydritových pojiv / Research in the Field of Anhydrite Binders

Břicháčková, Jana January 2014 (has links)
The presented work deals with research in the field of sulfate binders on the anhydrite base. Conceptually, it is divided into a general theory of sulfate binders and anhydrite mortar compounds, which is describing in detail the using of anhydrite mortar compounds on the poured floor screeds, and then the experimental part, where is made the mineralogical analysis of seven different gypsum resources and subsequent is monitored the effect of two sulfate exciters on the achieved technological properties and hydration process.
22

Interakce mobilních pracovních strojů a pojížděného podloží / Interaction between Mobile Working Machines and Rolled Surfaces

Pokorný, Jan January 2010 (has links)
This dissertation thesis is concerning with an interaction between mobile working machines and rolled surfaces. Machines and their constructions parts behavior were observed. There are some machines that can change state of surface. And due to these change of surface the machine is in different conditions for drive and also for works. The interaction of working machines and rolled surfaces was categorized in this work and for each category here is a methodic work flow for solution of various cases. Three examples are described in this work. Some simulating programs were used for all cases and therefore there is a methodic work flow for creating and simulating of models. Three described examples include a complex solution of hydraulic drive for vibration exciter of vibration roller, small cleaner of canalizations with aim on load case to frame of this cart. The third example describes solution of undercarriage frames of agricultural semi-trailers. This example is the most extensive chapter from this work due to including of marketing research at the beginning of development and also verification of simulated results with results from real prototype tests at the end of development of these undercarriage frames.
23

End-Shield Bridges for High-Speed Railway : Full scale dynamic testing and numerical simulations

Elgazzar, Hesham January 2017 (has links)
The increasing need for High-Speed Railway (HSR) to reduce the travelling time requires increasing research within this field. Bridges are main components of any railway network, including HSR networks, and the optimization of their design for this purpose would contribute to a faster and more cost effective development of the HSR network. The initial investment, the running and maintenance costs of the bridges can be decreased through better understanding of the their dynamic behaviour. This thesis studies the dynamic behaviour of end-shield railway bridges under HSR operation. 2D beam analysis is used to study the effect of the distribution of the train’s axle load. Relatively accurate 3D FE-models are developed to study the effect of Soil-Structure Interaction (SSI) and the dynamic response of the bridges. Modelling alternatives are studied to develop an accurate model. A full scale test of a simply supported Bridge with end-shields using load-controlled forced excitation was performed and the results were used to verify the theoretical models. A manual model updating process of the material properties of the 3D FE-model is performed using FRFs from the field measurements. A Simple 2D model is also developed, where a spring/dashpot system is implemented to simplify SSI, and updated to reproduce the field measured responses. The conclusions of the project emphasize the importance of SSI effects in the dynamic analysis of end-shield bridges for predicting their dynamic behaviour. The conclusions also show that the modelling of the surrounding soil and the assumption of the soil material parameters have significant effect on the dynamic response. Even the boundary conditions, bedrock level and the ballast on the railway track affects the response. The results also show that the bridge’s concrete section behaves as uncracked section under the studied dynamic loading. / <p>QC 20170403</p>
24

Třísítný vibrační třídič / Three-sided vibrating screen

Švrček, Jakub January 2020 (has links)
This diploma thesis deals with the design of an inclined three-sided vibrating screen, which is designed for sorting bulk aggregates. The aim of the diploma thesis is primarily to make a construction design with a specific comparison of various design solutions, considering the calculated operating parameters. In the construction design, is used not only the experience of the manufacturer of this type of machine, but also recommendations based on the manu-facturers of screens component. The design also includes a comparison of two types of flex-ible mounting, which is one of the basic structural units of the entire vibrating screen. The thesis is conceived from the basics, with emphasis on the simplicity and functionality of the device.
25

Nabíječka autobaterií se spínaným zdrojem / The inverter based battery charger

Kadlec, Josef January 2010 (has links)
The aim of this master’s thesis is provide detailed information about car battery’s charger with a switching power supply. The kind of this power supply is one-pulsed conducting inverter with transformer. The charger’s rates of nominal voltage are 6 and 12 V. The method of charging is charging by constantly voltage with a current limitation. The values of a current limitations are 0.5A, 5A and 20A. The charger’s maximal current is 50A. This current can help to the accumulator with starting of a vehicle. This device is equipped by indicators which indicate the end of charging.
26

Řídicí systém pro elektrodynamický budič vibrací / Control system for electrodynamic vibration exciter

Čala, Martin January 2014 (has links)
Master's thesis deals with implementation of a control system for an electrodynamic exciter. Patent and literature research with focus on applicable control methods is performed. Then, description of the methods applicable in the system identification, as well as types of the signals used in the vibration testing are discussed. The practical section is dedicated to the analysis of available hardware resources, design, assembly and verification of a control system for an electrodynamic exciter equipped with piezoelectric accelerometer and components of National Instruments.
27

Pilot Testing of a Hydraulic Bridge Exciter / Pilottest av en hydraulisk broexciterare

Borg, Richard, Dymén, Olivier January 2015 (has links)
In the design of a railway bridge that is meant for train speeds larger than 200 km/h, the Swedish Traffic Administration requires a dynamic analysis in addition to the conventional static design. The models used for static design may not always be suitable for dynamic analysis, which could lead to inaccurate estimations of the dynamic response. The reason for this is a limited knowledge of the actual structural dynamic behaviour of bridges, which is why a hydraulic bridge exciter has been developed. With this device, smaller bridges can be excited in a load- or displacement-controlled manner under variable frequency and load. By having known inputs, the bridges’ dynamic properties can be evaluated using experimental modal analysis. A finite element model of the double tracked railway bridge Pershagen was created in order to plan a pilot test of the bridge exciter. The influence of the load amplitude and sweep rate was evaluated. A theoretically optimal excitation position was also investigated in order to excite as many eigenmodes as possible from one position during the pilot test. Based on these results, a pilot test was performed on the Pershagen Bridge. The dynamic properties of the bridge were evaluated based on the results from the test. From the pilot test it could be concluded that the load amplitude had a direct influence on the dynamic properties of the bridge, hence the dynamic behaviour is non-linear. The 1st vertical bending mode and its dynamic properties could also be identified. / Då en järnvägsbro som är avsedd för tåghastigheter över 200 km/h ska dimensioneras ställs det krav av Trafikverket att en dynamisk analys av bron skall utföras, utöver konventionell statisk dimensionering. De bromodeller som används för statisk analys är dock inte alltid lämpliga för dynamisk analys, vilket kan leda till felaktiga skattningar gällande den dynamiska inverkan. Anledningen till detta är att kunskapen om broars dynamiska egenskaper är begränsade, och av denna anledning har en lastexciterare utvecklats. Med hjälp av denna anordning kan mindre broar exciteras med kontrollerad last eller förskjutning under variabel frekvens och last. Då dessa input-parametrar är kända kan broars dynamiska egenskaper utvärderas genom experimentell modal analys. En finit element-modell av den tvåspåriga järnvägsbron vid Pershagen har skapats för att kunna planera ett pilottest av lastexciteraren. Svephastigheten och lastamplituden har analyserats. En teoretiskt optimal exciteringsposition har utvärderats för att excitera största möjliga antal moder från en och samma position under pilottestet. Utifrån dessa resultat utfördes ett pilottest på bron vid Pershagen, där brons dynamiska egenskaper utvärderades utifrån resultaten. Från pilottestet kunde en slutsats dras om att lastamplituden hade en direkt inverkan på de dynamiska egenskaperna, vilket betyder att det dynamiska beteendet är olinjärt. Den första vertikala böjmoden och dess dynamiska egenskaper kunde också fastställas.
28

Sensorless control of brushless synchronous starter generator including sandstill and low speed region for aircraft application / Commande sans capteurs mécaniques de la machine synchrone à trois étages à faible vitesse pour une application aéronautique

Maalouf Haddad, Amira 03 March 2011 (has links)
In More Electric Aircraft, different power system activities are attributed to electrical means such as the start-up of the main engine. In this context, the study of the sensorless control of the Brushless Synchronous Starter Generator (BSSG) that is used to electrically start the main engine is revealed to be a very interesting issue. For long time, the elimination of the mechanical sensor was highly recommended for reliability, cost, weight, integration issues.Hence, this work aims to transpose the results obtained in the research area to an avionic testbench. It presents an adaptive sensorless technique to use when electrically starting the main engine of the aircraft. This is achieved by elaborating three different methods selected depending on the speed of the machine and based on the :- injection of a high frequency signal- use of the back-emf of the Permanent Magnet Generator (PMG)- use of the extended Kalman Filter EKFIn this work, it is shown that the …first method gives good position estimation results from standstill up to 8% of the rated speed. Then, the back-emfs of the PMG are used to detect the position of the BSSG when the speed exceeds the 8% of the rated speed. Good results are observed with this method at medium and high speed.For redundancy reasons, the EKF was also used in this work. Thus, the estimated position can be delivered via two different estimation algorithms in medium and high speed region.The implementation of the algorithm was achieved on an FPGA board since the latter can ensure a very tiny execution time. The fastness of the treatment ensures quasi-instantaneous position estimation and does not practically introduce any phase lag in the position estimation. / Aujourd'hui, l'aviation est en train de vivre des évolutions technologiques concernant surtout l'attribution de différentes fonctionnalités aux équipements électriques et ceci au détriment d'équipements hydrauliques et mécaniques assurant les mêmes fonctionnalités.Dans le cadre de l'avion plus électrique, le démarrage électrique sans capteurs mécaniques de la turbine de l'avion préoccupe les avionneurs de nos jours. Les problèmes introduits par ce capteur ont été identifiés : problèmes de coût et de poids, problèmes de fiabilité et d'intégration.Ce travail présente alors une commande sans capteurs pour la machine synchrone à trois étages à utiliser durant le démarrage électrique de l'avion. Ceci est réalisé avec trois méthodes de détection de la position selon la vitesse de rotation, basées sur :- l'injection d'un signal à haute fréquence- l'utilisation d'un filtre de Kalman étendu FKE- les fém. du PMG (Permanent Magnet Generator) La première méthode donne de bons résultats d'estimation depuis l'arrêt jusqu'à 8% de la vitesse nominale de la machine. Au-delà de cette vitesse, es valeurs des fém. du PMG deviennent assez élevées pour être utilisées dans l'estimation de la position. De bons résultats sont obtenus à moyenne et haute vitesse.Pour des questions de redondance, le FKE est aussi utilisé. Ainsi, la position estimée peut être fournie par l'un des deux algorithmes à moyenne et haute vitesse.L'implémentation de ces algorithmes est réalisée via une carte FPGA étant donné que celui-ci garantit un temps d'exécution. La rapidité de traitement garantit une estimation de la position quasi-instantanée et donc n'introduit pratiquement pas des retards dans l'estimation.
29

Modelling, Analysis, and Control Aspects of a Rotating Power Electronic Brushless Doubly-Fed Induction Generator

Malik, Naveed ur Rehman January 2015 (has links)
This thesis deals with the modeling, analysis and control of a novel brushlessgenerator for wind power application. The generator is named as rotatingpower electronic brushless doubly-fed induction machine/generator (RPEBDFIM/G). A great advantage of the RPE-BDFIG is that the slip power recoveryis realized in a brushless manner. This is achieved by introducing an additionalmachine termed as exciter together with the rotating power electronicconverters, which are mounted on the shaft of a DFIG. It is shown that theexciter recovers the slip power in a mechanical manner, and delivers it backto the grid. As a result, slip rings and carbon brushes can be eliminated,increasing the robustness of the system, and reducing the maintenance costsand down-time of the turbine. To begin with, the dynamic model of the RPE-BDFIG is developed andanalyzed. Using the dynamic model, the working principle of the generatoris understood and its operation explained. The analysis is carried out atspeeds, ±20% around the synchronous speed of the generator. Moreover, thedynamics of the generator due to external load-torque disturbances are investigated.Additionally, the steady-state model is also derived and analyzed forthe machine, when operating in motor mode. As a next step, the closed-loop control of the generator is considered indetail. The power and speed control of the two machines of the generator andthe dc-link voltage control is designed using internal model control (IMC)principles. It is found that it is possible to maintain the stability of thegenerator against load-torque disturbances from the turbine and the exciter,at the same time maintain a constant dc-link voltage of the rotor converter.The closed-loop control is also implemented and the operation of the generatorwith the control theory is confirmed through experiments.In the third part of the thesis, the impact of grid faults on the behaviourof the generator is investigated. The operation of the generator and its responseis studied during symmetrical and unsymmetrical faults. An approachto successful ride through of the symmetrical faults is presented, using passiveresistive network (PRN). Moreover, in order to limit the electrical and mechanicaloscillations in the generator during unsymmetrical faults, the dualvector control (DVC) is implemented. It is found that DVC to a certain extentcan be used to safeguard the converter against large oscillations in rotorcurrents. Finally, for completeness of the thesis, a preliminary physical design ofthe rotating power electronic converter has been done in a finite elementsoftware called ANSYS. The thermal footprint and the cooling capability,with estimates of the heatsink and fan sizes, are presented. Besides, another variant of a rotating electronic induction machine whichis based on the Lindmark concept and operating in a single-fed mode is also investigated. It’s steady-state model is developed and verified through experiments. / <p>QC 20151006</p>
30

Analysis and Control Aspects of Brushless Induction Machines with Rotating Power Electronic Converters

Malik, Naveed ur Rehman January 2012 (has links)
This thesis deals with the steady-state, dynamic and control aspects of new type of brushless configuration of a doubly-fed induction machine in which the slip rings and carbon brushes are replaced by rotating power electronics and a rotating exciter. The aim is to study the stability of this novel configuration of the generator under mechanical and grid disturbances for wind power applications. The derivation, development and analysis of the steady-state model of the brushless doubly-fed induction machine with a rotating excitor and the power electronic converters mounted on the shaft and rotating with it, is studied. The study is performed at rated power of the generator between ±20% slip range. Moreover unity power factor operation between ±20% speed range is also discussed. Furthermore dynamic modeling and control aspects of the generator are also analyzed. The controllers were designed using Internal Model Control principles and vector control methods were used in order to control the generator in a closed-loop system. It is shown that through the use of proper feedback control, the generator behaves in a stable state both at super-synchronous and sub-synchronous speeds. Moreover Low Voltage Ride Through of the generator during symmetrical and unsymmetrical voltage dips is also investigated. Passive Resistive Network strategy is employed for Low Voltage Ride Through of the generator during symmetrical voltage dips. On the other hand, Extended Vector Control is used in order to control the negative sequence currents during unsymmetrical voltage dips. Suppression of negative sequence currents is important as they cause extra heating in the windings and affects the lifetime of the mechanical and electrical components of the generator and system due to oscillations in power and torque. In addition to the above studies a steady-state model of a single-fed induction machine is also developed and investigated where the rotating exciter is removed and the rotor windings are short-circuited through the two rotating power electronic converters. In this way the slip power circulates in the rotor and with the help of the two rotating electronic converters, rotor current is used to magnetize the induction machine thereby improving the power factor. The steady state model is verified through experimental results. / <p>20120914</p> / Brushless Wind Generator with Rotating Power Electronic Converters

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