Dissertations / Theses on the topic 'Magnetická levitace'

The thesis deals with the design of a hybrid magnetic bearing. This is an extension of the issue of common bearings in high-speed motors. The work is divided into three parts. A general theory of magnetic bearings is described in the first part. The second part deals with the mathematical description of the bearing. A proposal of specific hybrid magnetic bearing is described in the third part. The bearing for the motor was already designed. It is a 45000rpm motor with a power output of 12 kW. This thesis aims to create a design of hybrid magnetic bearing with magnets to create a permanent magnetic field and coils to regulate forces to stabilize the rotor and limit vibrations. The practical design includes mathematical calculation in Matlab and computer simulation based on the finite element method in ANSYS Maxwell.

Diploma thesis is summarizing common theoretical knowledge about permanent magnets and electromagnetism. Represent DC electromagnet as basic part for levitated high-speed train. Work is analyzing basics under cart and principles used for magnetic levitation in high-speed transportation. Second practice part including projecting construction levitated cart and analyzing acquired mathematical model of electromagnet. Work is analyzing process for projecting control for side electromagnets and realization real model, including tuning computer communication with states of sensors and comparison real model with model simulated in program Simulink.

I discuss the design and operation of a system for levitating a charged, μm-scale, multilayer graphene nanoplatelet in a quadrupole electric field trap in high vacuum. Levitation decouples the platelet from its environment and enables sensitive mechanical and magnetic measurements.

First, I describe a method of generating and trapping the nanoplatelets. The platelets are generated via liquid exfoliation of graphite pellets and charged via electrospray ionization. Individual platelets are trapped at a pressure of several hundred mTorr and transferred to a trap in a second chamber, which is pumped to UHV pressures for further study. All measurements of the trapped platelet's motion are performed via optical scattering.

Second, I present a method of gyroscopically stabilizing the levitated platelet. The rotation frequency of the platelet is locked to an applied radio frequency (rf) electric field E_rf. Over time, frequency-locking stabilizes the platelet so that its axis of rotation is normal to the platelet and perpendicular to E _rf.

Finally, I present optical data on the interaction of a multilayer graphene platelet with an applied magnetic field. The stabilized nanoplatelet is extremely sensitive to external torques, and its low-frequency dynamics are determined by an applied magnetic field. Two mechanisms of interaction are observed: a diamagnetic polarizability and a magnetic moment proportional to the frequency of rotation. A model is constructed to describe this data, and experimental values are compared to theory.

Magnetically levitated microrobotic systems have shown a great deal of promise for micromanipulation tasks. A new large-gap magnetic suspension system has recently been developed at the University of Waterloo in order to develop microrobotic systems for various applications. In order to achieve motion with the system, a model is needed in order to facilitate the design of various aspects of the system, such as the microrobot and the controller. In order to derive equations of motion for the system attempts were made to characterize the force produced by the magnetic drive unit in terms of a simple analytical equation. The force produced by the magnetic drive unit was estimated with the aid of a finite element model. The derived equations were able to predict the general trend of the force curves, and with sufficient parameter tweaking the error between the force estimated by the finite element model and the force estimated by the analytical equation could be minimized. System models describing the motion of the system in the horizontal and vertical directions are identified and compared to the actual system response. The vertical position response is identified through a least squares parameter estimate of the closed loop response combined with a partial reconstruction of the root locus diagram, with the model structure based on the known dynamics of a simplified form of magnetic levitation. This model was able to provide a reasonable prediction of the system response for a variety of PID controllers under a variety of input conditions. The horizontal models are identified using a least-squares parameter estimate of the open loop characteristics of the system. The horizontal models are able to provide a reasonable prediction of the system response under PD and PID control. Full spatial motion of a microrobot prototype is demonstrated over a working range of 20x22x30 mm³, with PID controller parameters and reference trajectories adjusted to minimize disturbances. The RMS error at steady state is on the order of 0. 020 mm for vertical positioning and 0. 008 mm for horizontal positioning. A linear quadratic regulator implemented for vertical position control was able to reduce the vertical position RMS error to 0. 014 mm.

High speed applications demands with a need for lower energy consumption lead to designing new types of bearings. In the last decades magnetic bearing, which would be able to obtain passive stable levitation using regular materials at room temperature, has been searched. This has lead to development of electrodynamic bearing based on eddy currents principle. Currently the electrodynamic bearings are still not fully explored and further research is needed. The aim of the work is to describe the theory about modern magnetic bearing, analysis and design of electrodynamic bearing according to given parameters. The finite element method is used for further analysis and evaluate behaviour of its properties.

This dissertation presents two novel 6-axis magnetic-levitation (maglev) stages that are capable of nanoscale positioning. These stages have very simple and compact structure that is advantageous to meet requirements in the next-generation nanomanufacturing. The 6-axis motion generation is accomplished by the minimum number of actuators and sensors. The first-generation maglev stage is capable of generating translation of 300 ??m in x, y and z, and rotation of 3 mrad about the three orthogonal axes. The stage demonstrates position resolution better than 5 nm rms and position noise less than 2 nm rms. It has a light moving-part mass of 0.2126 kg. The total power consumption by all the actuators is only around a watt. Experimental results show that the stage can carry, orient, and precisely position an additional payload as heavy as 0.3 kg. The second-generation maglev stage is capable of positioning at the resolution of a few nanometers over a planar travel range of several millimeters. A novel actuation scheme was developed for the compact design of this stage that enables 6-axis force generation with just 3permanent-magnet pieces. Electromagnetic forces were calculated and experimentally verified. The complete design and construction of the second-generation maglev stage was performed. All the mechanical part and assembly fixtures were designed and fabricated at the mechanical engineering machine shop. The single moving part is modeled as a pure mass due to the negligible effect of the magnetic spring and damping. Classical as well as advanced controllers were designed and implemented for closed-loop feedback control. A nonlinear model of the force was developed and applied to cancel the nonlinearity of the actuators over the large travel range. Various experiments were conducted to test positioning, loading, and vibration-isolation capabilities. This maglev stage has a moving-part mass of 0.267 kg. Its position resolution is 4 nm over a travel range of 5 ?? 5 mm in the x-y plane. Its actuators are designed to carry and precisely position an additional payload of 2 kg. Its potential applications include semiconductor manufacturing, micro-fabrication and assembly, nanoscale profiling, and nano-indentation.

Existing thrust measurement systems (TMSs) at NASA Stennis Space Center use strain gauges and flux plates to measure forces produced by a test article. Alignment and calibration can take two weeks or more every time a piece of hardware or test article is changed. Cross axis loading is also problematic because it is impossible to perfectly align the flex plates and strain gauges in the thrust direction. In response to these problems, a magnetically levitated thrust measurement system has been proposed and a 300lb capacity demonstrator has been designed and built. In this design, the magnetic bearings work concurrently as support bearings and force measurement devices. The demonstrator consists of a floating frame that is completely levitated within a fixed frame by four support bearings carrying loads in the x- and y-direction and seven thrust bearings carrying loads in the z- or thrust direction. Joe Imlach of Imlach Consulting Engineering designed the demonstrator and magnetic bearing components, while Virginia Tech's role has been the application of the multipoint calibration technique including code development, the implementation of a 128-channel data acquisition system, and the overall test verification of the TMS demonstrator.A turnbuckle assembly and magnetostrictive actuator are used in series with a conventional load cell for static and dynamic testing, respectively. Both current based and flux based force equations were used to measure the reaction forces at the bearings. The static results using the current based equations including the current based fringing equations resulted in accuracies of 93% of full load, while the static results using the flux based equations including the flux based fringing equations resulted in accuracies of 99.5% of full load. These accuracies can be compared to accuracies of 83-90% seen in previous work using magnetic bearings to measure forces by monitoring currents and to accuracies of about 99% in previous work using magnetic bearings to measure forces by monitoring fluxes. All of the improved accuracies were made possible through the implementation of a calibration technique known as the multipoint method and the implementation of a gap dependent fringing correction factor developed by Joe Imlach. The demonstrator was not outfitted with accelerometers so the inertia of the floating frame could not be accounted for, limiting the scope of dynamic testing. However, the tests confirmed the ability of the demonstrator to measure dynamic loads in general.
Master of Science

Thesis (S.M. and S.B.)--Massachusetts Institute of Technology, Dept. of Nuclear Science and Engineering, 2009.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 95-96).
A vertically adjustable electrostatic probe array was made to observe the previously seen low-frequency angular oscillations in LDX and identify if they are related to computationally expected convective cells. The array rests one meter from the centerline and measures edge fluctuations at field lines near the separatrix. It spans ninety degrees and has 24 probes mounted on it for total probe tip separation of 6.8cm. Bispectral analysis of the fluctuations show that that an inverse cascade of energy is present at times in LDX. The cascade transfers energy from small spatial scale structures to large scale structures. The wavenumber spectrum is xc k-1.4 to cx k-25 at high wavenumbers, which encompasses the inverse energy cascade regime of c k-5/3. The plasma also has a linear dispersion relation which gives a phase velocity of 2-16 k. This phase velocity is inversely correlated with neutral gas pressure in the vessel. The velocity also has a local maximum at 5 pTorr which is the pressure that produces maximum plasma density. The radial E x B drift velocities are observed to have a mean near zero, which indicates a closed structure like a convective cell. The instantaneous radial drift velocities are on the order of the ion sound speed, which is 35 km/s.
by Ryan M. Bergmann.
S.M.and S.B.

An induction setup for levitation studies of molten metals was built. The setup was used to levitate and heat stainless steel samples of 2.00 g to 1600 °C and subject them to different atmospheres. Changes in shape and temperature were recorded by video and infrared thermocouple. Oxide films forming on the droplets during levitation were observed. It was possible to notice an immediate surface reaction when the reaction gas was introduced. This reaction is concluded to influence the surface and bulk composition, and therefore have an effect on the shape evolution of the droplet. A more oxidizing atmosphere resulted in a more conical droplet shape; this is thought to be an effect of lowered surface tension and the conically shaped volumetric force caused by the magnetic field. Changes in temperature after the sample is molten are thought to be an effect of changes in emissivity, caused by surface oxidization. Post mortem analysis show a difference in surface morphology for samples subjected to different gases, as well as a difference in amount of oxidization.

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Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior
This work presents a model of bearingless induction machine with divided winding. The main goal is to obtain a machine model to use a simpler control system as used in conventional induction machine and to know its behavior. The same strategies used in conventional machines were used to reach the bearingless induction machine model, which has made possible an easier treatment of the involved parameters. The studied machine is adapted from the conventional induction machine, the stator windings were divided and all terminals had been available. This method does not need an auxiliary stator winding for the radial position control which results in a more compact machine. Another issue about this machine is the variation of inductances array also present in result of the rotor displacement. The changeable air-gap produces variation in magnetic flux and in inductances consequently. The conventional machine model can be used for the bearingless machine when the rotor is centered, but in rotor displacement condition this model is not applicable. The bearingless machine has two sets of motor-bearing, both sets with four poles. It was constructed in horizontal position and this increases difficulty in implementation. The used rotor has peculiar characteristics; it is projected according to the stator to yield the greatest torque and force possible. It is important to observe that the current unbalance generated by the position control does not modify the machine characteristics, this only occurs due the radial rotor displacement. The obtained results validate the work; the data reached by a supervisory system corresponds the foreseen results of simulation which verify the model veracity
Este trabalho apresenta um modelo para a m?quina de indu??o sem mancais com bobinado dividido. O principal objetivo consiste na obten??o do modelo da m?quina para que possam ser implementados controladores mais eficientes. Para se alcan?ar tal modelo, fez-se uso dos mesmos artif?cios utilizados para as m?quinas convencionais adotados na literatura, o que possibilitou um manuseio simplificado das vari?veis envolvidas. A m?quina estudada ? uma adapta??o de uma m?quina de indu??o convencional, o que foi poss?vel dividindo-se os enrolamentos do estator e tornando acess?veis todos os seus terminais. Essa t?cnica dispensa o acr?scimo de um outro enrolamento ao estator para a realiza??o do controle de posi??o radial, o que resulta em uma m?quina mais compacta. Uma outra caracter?stica dessa m?quina ? a varia??o da matriz de indut?ncias em fun??o do deslocamento radial do rotor, a varia??o do entreferro produz varia??es no fluxo e conseq?entemente nos valores de indut?ncias tanto pr?prias quanto m?tuas. O modelo da m?quina convencional pode ser utilizado para a m?quina sem mancais quando o rotor estiver fixo no centro, por?m em situa??es de deslocamento radial esse modelo falha e n?o pode ser? plicado. A m?quina em quest?o possui dois conjuntos motor+mancal, ambos de quatro p?los, e foi projetada com seu rotor na posi??o horizontal, o que incluiu algumas dificuldades ? implementa??o. O rotor utilizado possui caracter?sticas peculiares, o qual ? projetado de acordo com as exig?ncias da m?quina, a fim de render o maior torque e for?a poss?veis. ? importante observar que o desbalanceamento de correntes, gerado pelo controle de posi??o radial, n?o modifica os par?metros da m?quina, isso apenas ocorre devido ao deslocamento radial do rotor. Os resultados apresentados viabilizaram a valida??o do trabalho, os dados obtidos atrav?s de um sistema supervis?rio condizem com os previstos em simula??o, o que atesta a veracidade do modelo

碩士
國立成功大學
航空太空工程學系
86
The tendency of accurately industrial technique has been developedfrom contact kinematic mechanism to noncontact kinematic mechanism.Generally, it can meliorate efficiency of machine and be energy-saving.In 1980''s, the magnetic material developed quickly, and permanentmagnet can raise magnetic flux density greatly. Thus it can change thetraditional conditions. Magnetic technique has many advantages. It is not only noncontact but also suits to use in special surrounding especially in aerospace.Otherwise magnetic technique can reduce friction and maintains systemperformance easily. In this thesis, we want to construct a magnetic levitation system that is used in semiconductor manufacturing process. This magnetic levitationsystem uses permanent magnet embedded inside the traditional electromagnet. Permanent magnet provides major lift force when the system is stable. The energy loss of magnetic levitation system is lowerthan the traditional electromagnetic system. Thus magnetic levitation system in this thesis can reach a high efficiency. In this thesis, a preliminary study and system design is discussedwith theoretical formulations and physical parameter identifications.

碩士
國立臺灣大學
電機工程學研究所
90
This thesis is one of the sub-projects of the main project “Intelligent Hybrid Control for Two-Dimensional Magnetic-Levitated Platform”. The surge of high-tech industry, especially the continuous progress in the area of IC manufacturing, has posed a serious demand on the positioning precision for process equipment. In react to the demand from industries, this project focuses its research on the intelligent hybrid control for two-dimensional magnetic-levitated platform. The emphases of the proposed system are on the embedded/mechatronic system structure and the intelligent/hybrid design with high positioning precision. Due to the horizontal unstability of magnetic-levitated system, it is hard to break through the problem of the stability of the carrier. This thesis will set up a precise dynamic simulation system. The thesis can be summarized as: 1. Set up dynamic simulation system; 2. Verify the practicability of the carrier 3. Design new carrier.

碩士
南台科技大學
電機工程系
90
High performance of clean room is necessary in order to produce high density of integrated circuit. Microscopic dust motes are mainly produced by personal entrance and semiconductor equipment. The bigger and bigger wafers are too weak to being manually moved. It is necessary to develop an automatic material transportation system among the manufacturing process in order to overcome the difficulty. The paper concerns with the research of the automatic material transportation system for semiconductor manufacturing application using magnetic suspension technology and focuses on the levitation control for magnetic levitated transport system. Developing a control algorithm to stabilize the system such that the transport system can be moved non-frictionally.

碩士
國立臺灣大學
電機工程學研究所
92
High technology develops continuously. So the precision of semiconductor must promote continuously especially. This makes the requirement for ducting off from semiconductor foundry increases constantly. The thesis to this industrial trend has developed the intelligent hybrid control of the level magnetism float system. The goal is that using the intelligent hybrid control method to reach the task of orientation in the Magnetic-levitated system. Because in the Magnetic-levitated system, any magnetic object is all unable to get a steady state in the static magnetic field, unless add proper control and could reach the achievement required , the Magnetic-levitated system must be according to tickling the principle of controlling that the magnetism floats, produce the magnetic field to control its unstable natural instincts with the electric current. This thesis is making use of the simulation system of the attitude of setting up accurate magnetism to float, try the designs of different carrier and the controller , is in the hope of reaching the goal with suspending and movement of carrier by control. The thesis can be summarized as: 1. Analyzes characteristic of the the Magnetic-levitated system and the dynamic behavior by the dynamic simulation system. 2. Try the designs of different carrier and controller.

碩士
國立臺灣大學
電機工程學研究所
92
So far general electronical stomach endoscope examination often make patients feel unwell and fearful, and wireless capsule endoscope can''t observe single region of stomach repeatedly to examinate stomach clearly like electronical endoscope. In order to solve the problems of those endoscopes discussed above, this paper presents a new beter endoscope examination system named Megnetic-Levitated Capsule Endoscope Control System and related experiments. The purpose of this paper to develop a confortable, convenient, and effective endoscope examination method. Megnetic-levitated capsule endoscope control system applies magnetic-levitated control theories and technologies. It performs capsule endoscope movement and position control by using magnetic force; moreover, it transmits the images captured by capsule''s inner image capturing device to the monitor. The system also utilizes man-machine interface control technologies. It make doctors not only be able to operate capsule endoscope easily and well with man-machine interface devices like joystick, monitor, and monitoring software fram, but also perform endoscope examination clearly and effectively. In this paper, to begin with, we will introduce megnetic-levitated control theories and methods concerned with the system and also discuss image capture and processing researches and technologies. Then, we will explan how to apply the theories and technologies of magnetic-levitated control and image to the system. The construction, design concept, and hardware scheme of system will be described. Finally, we will illustrate the experiment system and equipment, and also analyze the results of experiment to verify the theories presented in this paper. Further, the performance and usability of whole system will be estimated, and the future research direction about megnetic-levitated capsule endoscope will be discussed.

碩士
中原大學
機械工程研究所
95
In recent years, the active magnets suspended platforms are often seen in the mechanism that designed for high-speed, high position precision or low friction, such as micro/nano linear stages, especially. This research was aimed at the controller design for a five degree-of-freedom magnetic levitated platform. The magnetic levitated platform system basically is an unstable system, it is not only a highly nonlinear system, also is a dynamic coupled system. Furthermore, there are four actuators and only three controlled factors in the vertical position of the platform. Therefore, a decoupled structure was proposed to resolve the control question. Based on the decoupled model, we designed a global variable structure controller to decrease the influence of the load changes and reduce the system vibration, and promote the positioning precision. Moreover, a saturation function was added to controller to form a sliding layer and to eliminate the chatter phenomenon. The experimental results showed the suspension precision was about less 1 �慆 as the load changed from 10kg to 30kg. In the power amplifier, this research used the pulse width modulation technique to design a switched current driver design for the electric magnets of magnetic suspension system. Dye to the phenomenon of the MOSFET, the driver can operate in the great voltage and under the bigger electric currents than the traditional push-pull linear driver. Furthermore, the relationship of the force slew rate and the supply voltage are proposed. The driver is composed of the interior loop control circuit of the proposed driver made by the operational amplifier, the two-quadrant chopper, and the three-level PWM controller. The experimental results show the proposed driver better than the traditional push-pull linear driver in the response rate, the system bandwidth, the transition response as well as the low current distortion. The experimental results also shown the system bandwidth of the proposed driver may reach several kHz under the different loading condition.

An electro-dynamic Magnetic Levitation vehicular system has been modelled and studied. In practice, a MagLev vehicle will consist of a number of cars which are mechanically coupled to each other. It is reasonable to assume that each of these cars will be independently controlled with the help of a supervisory controller. This thesis deals with the control aspects of one such car. The car is equipped with two control magnets one at the front end and the other at the rear end. The currents in these magnets can be varied to provide levitation and pitch-axis control. The rotational aspects of the vehicle about the yaw and roll axes is neglected here. The car has also a horizontal thrust producing mechanism, the dynamics of which has been neglected. A controller has been devised using frequency domain analysis. It is shown that the vehicle Can be controlled effectively to meet nominal ride specifications. These specifications are derived both from the point of practical implementation of the vehicle and from the need to ensure good ride quality. The controller needs to be robust in its operation. This thesis shows that a simple controller configuration is enough to maintain satisfactory operation for a variety of operating conditions. It is also shown that in the event of a disrupted magnet circuit, normal operation can be restored with a backup set, without having to stop the vehicle or endanger its occupants. This study is entirely conceptual and no attempt has been made to practically implement the system. It should also be noted that a reasonable choice was made for the parameters of the model, that compares closely to data from existing MagLev systems.
Graduation date: 1991