No description available.

Acoustic levitation is a method which uses sound radiation to suspend matter in a medium. The main use of this phenomenon is for the contactless processing of matter, allowing to manipulate small objects without any solid contact. Contactless processing of matter presents many advantages in, for example, the fabrication of MEMS (microelectromechanical systems) where handling the components is challenging because of their fragile and surface-sensitive characteristics or in the chemical/biological industry when handling high-purity or hazardous materials. Thus, a new device for noncontact linear transportation of small solid objects is presented here. In this device, ultrasonic flexural vibrations are generated along the ring shaped vibrator using two Langevin transducers and by using a reflector parallel to the vibrator, small particles are trapped at the nodal points of the resulting acoustic standing wave. The particles are then moved by generating a traveling wave along the vibrator, which can be done by modulating the vibration amplitude of the transducers. The working principle of the traveling wave along the vibrator has been modeled by the superposition of two orthogonal standing waves, and the position of the particles can be predicted by using finite element analysis of the vibrator and the resulting acoustic field. A prototype consisting of a 3 mm thick, 220 mm long, 50 mm wide and 52 mm radius aluminum ring-type vibrator and a reflector of the same length and width was built and small polystyrene spheres have been successfully transported along the straight parts of the vibrator. / Levitação acústica é um método para suspender matéria em um meio através de pressão de radiação acústica gerada por intensas ondas de som. O principal uso desse fenômeno é na manipulação de partículas sem contato solido. Esse fenômeno tem várias aplicações para pesquisas onde deve ser evitado todo o contato como, por exemplo, na área de biologia, química, e na fabricação de MEMS. Assim, um novo sistema de transporte linear de partículas por levitação acústica está apresentado aqui. Nesse sistema, vibrações flexurais estão geradas em uma placa tipo anel com dois transdutores tipo Langevin, e colocando um refletor paralelo ao oscilador, partículas estão presas no pontos nodais da onda acústica gerada. As partículas estão deslocadas modulando a amplitude dos transdutores. Assim, este trabalho tem como objetivos a modelagem do fenômeno de levitação acústica, o dimensionamento de um protótipo de sistema de transporte linear de partículas por levitação acústica, bem como a fabricação e o controle desse protótipo. Um protótipo consistindo de uma estrutura tipo anel de alumínio de 3 mm de espessura, 220 mm de comprimento e um raio de 52 mm foi fabricado e o transporte de pequenas esferas de isopor foi realizado com êxito nas parte retas do vibrador.

Magnetic levitation technology has shown a great deal of promise for micromanipulation tasks. Due to the lack of mechanical contact, magnetic levitation systems are free of problems caused by friction, wear, sealing and lubrication. These advantages have made magnetic levitation systems a great candidate for clean room applications. In this thesis, a new large gap magnetic levitation system is designed, developed and successfully tested. The system is capable of levitating a 6.5(gr) permanent magnet in 3D space with an air gap of approximately 50(cm) with the traveling range of 20x20x30 cubic millimeters. The overall positioning accuracy of the system is 60 micro meters. With the aid of finite elements method, an optimal geometry for the magnetic stator is proposed. Also, an energy optimization approach is utilized in the design of the electromagnets. In order to facilitate the design of various controllers for the system, a mathematical model of the magnetic force experienced by the levitated object is obtained. The dynamic magnetic force model is determined experimentally using frequency response system identification. The response of the system components including the power amplifiers, and position measurement system are also considered in the development of the force model. The force model is then employed in the controller design for the magnetic levitation device. Through a modular approach, the controller design for the 3D positioning system is started with the controller design for the vertical direction, i.e. z, and then followed by the controller design in the horizontal directions, i.e. x and y. For the vertical direction, several controllers such as PID, feed forward and feedback linearization are designed and their performances are compared. Also a control command conditioning method is introduced as a solution to increase the control performance and the results of the proposed controller are compared with the other designs. Experimental results showed that for the magnetic levitation system, the feedback linearization controller has the shortest settling time and is capable of reducing the positioning error to RMS value of 11.56μm. The force model was also utilized in the design of a model reference adaptive feedback linearization (MRAFL) controller for the z direction. For this case, the levitated object is a small microrobot equipped with a remote controlled gripper weighting approximately 28(gr). Experimental results showed that the MRAFL controller enables the micro-robot to pick up and transport a payload as heavy as 30% of its own weight without a considerable effect on its positioning accuracy. In the presence of the payload, the MRAFL controller resulted in a RMS positioning error of 8μm compared with 27.9μm of the regular feedback linearization controller. For the horizontal position control of the system, a mathematical formula for distributing the electric currents to the multiple electromagnets of the system was proposed and a PID control approach was implemented to control the position of the levitated object in the xy-plane. The control system was experimentally tested in tracking circular and spiral trajectories with overall positioning accuracy of 60μm. Also, a new mathematical approach is presented for the prediction of magnetic field distribution in the horizontal direction. The proposed approach is named the pivot point method and is capable of predicting the two dimensional position of the levitated object in a given vertical plane for an arbitrary current distribution in the electromagnets of the levitation system. Experimental results showed that the proposed method is capable of predicting the location of the levitated object with less than 10% error.

Magnetic levitation technology has shown a great deal of promise for micromanipulation tasks. Due to the lack of mechanical contact, magnetic levitation systems are free of problems caused by friction, wear, sealing and lubrication. These advantages have made magnetic levitation systems a great candidate for clean room applications. In this thesis, a new large gap magnetic levitation system is designed, developed and successfully tested. The system is capable of levitating a 6.5(gr) permanent magnet in 3D space with an air gap of approximately 50(cm) with the traveling range of 20x20x30 cubic millimeters. The overall positioning accuracy of the system is 60 micro meters. With the aid of finite elements method, an optimal geometry for the magnetic stator is proposed. Also, an energy optimization approach is utilized in the design of the electromagnets. In order to facilitate the design of various controllers for the system, a mathematical model of the magnetic force experienced by the levitated object is obtained. The dynamic magnetic force model is determined experimentally using frequency response system identification. The response of the system components including the power amplifiers, and position measurement system are also considered in the development of the force model. The force model is then employed in the controller design for the magnetic levitation device. Through a modular approach, the controller design for the 3D positioning system is started with the controller design for the vertical direction, i.e. z, and then followed by the controller design in the horizontal directions, i.e. x and y. For the vertical direction, several controllers such as PID, feed forward and feedback linearization are designed and their performances are compared. Also a control command conditioning method is introduced as a solution to increase the control performance and the results of the proposed controller are compared with the other designs. Experimental results showed that for the magnetic levitation system, the feedback linearization controller has the shortest settling time and is capable of reducing the positioning error to RMS value of 11.56μm. The force model was also utilized in the design of a model reference adaptive feedback linearization (MRAFL) controller for the z direction. For this case, the levitated object is a small microrobot equipped with a remote controlled gripper weighting approximately 28(gr). Experimental results showed that the MRAFL controller enables the micro-robot to pick up and transport a payload as heavy as 30% of its own weight without a considerable effect on its positioning accuracy. In the presence of the payload, the MRAFL controller resulted in a RMS positioning error of 8μm compared with 27.9μm of the regular feedback linearization controller. For the horizontal position control of the system, a mathematical formula for distributing the electric currents to the multiple electromagnets of the system was proposed and a PID control approach was implemented to control the position of the levitated object in the xy-plane. The control system was experimentally tested in tracking circular and spiral trajectories with overall positioning accuracy of 60μm. Also, a new mathematical approach is presented for the prediction of magnetic field distribution in the horizontal direction. The proposed approach is named the pivot point method and is capable of predicting the two dimensional position of the levitated object in a given vertical plane for an arbitrary current distribution in the electromagnets of the levitation system. Experimental results showed that the proposed method is capable of predicting the location of the levitated object with less than 10% error.

Thesis (M.A.)--University of Hong Kong, 2001. / Includes bibliographical references.

Tiriamajame darbe nagrinėjamas ultragarso pritaikymas ultragarsinei levitacijai ore sukelti. Nagrinėjama ultragarsinės levitacijos taikymas medicinoje ir įvairių gabaritų įrenginiuose , taip pat didelių pramoninių agregatų veikime. Apžvelgiant tokių sistemų konstrukciją, galima rasti įvairių trūkumų, kuriuos ateityje galima tobulinti. Vienas iš didžiausių pastebėtų trūkumų - tai sistemos gabaritiniai matmenys. Todėl baigiamojo darbo metu buvo ieškota įvairių sprendimų kaip šį trūkumą išspręsti, ir buvo iškelti tikslai : 1. Optimizuoti Laboratorijoje turimą išilginių – lenkimo ultragarsinių virpesių T – tipo sistemą. 2. Sukurti ir ištirti naują radialinę lenkimo virpesių sistemą. Darbo uždaviniai : Išanalizuoti galingos ultragarsinių virpesių stovinčios bangos dideliame plote sukėlimo ypatybes. Susipažinti su Laboratorijoje esama T- tipo sistema, išanalizuoti jos darbą. Atlikti ultragarsinių sistemų kompiuterinį modeliavimą . Optimizuoti diskinio rezonatoriaus lenkimo virpesių rezonatoriaus skerspjūvį. Suprojektuoti, pagaminti ir suderinti optimizuotas sistemas. Iš elektrinės ir mechaninės pusės ištirti ultragarsines sistemas: nustatyti impedanso – dažninę ir fazinę bei amplitudines – dažnines charakteristikas prie įvairių elektrinių galių. Nustatyti levitacijos keliamos jėgos priklausomybę nuo paduodamos į pjezokeitiklį galios. Tiriamojo darbo metu nagrinėjamos jau sukurtos ir laboratorijoje... [toliau žr. visą tekstą] / The research is focused on the adaptation of ultrasound for creating airborne ultrasonic levitation. The study investigates the application of ultrasonic levitation for medical purposes and in the equipment of different dimensions, also in the operation of large industrial units. A closer look at the structure of such systems allows to detect multiple defects that could be eliminated in the future. One of the most evident defects is the size of the system. Thus, the purpose of this paper is the search of various solutions with the following objectives set forth: 1. Optimisation of longitudinal-bending ultrasonic vibration T type system used in the lab. 2. Creation and investigation of a new radial bending vibration system. Tasks of the study: To analyse the specifics of generating a powerful ultrasonic vibration standing wave in a big area. To get acquainted with T type system used in the lab, to analyse the operation of the system. To perform computer modeling of ultrasonic systems. Optimise the cross-section of disc type bending-mode resonator. To plan, build and fine-tune the optimised systems. To perform electrical and mechanical investigation of ultrasonic systems: to set frequency/phase and amplitude/frequency characteristics of impedance at different electrical voltages. To set the dependance of levitation power on the piezo converter input voltage. The study contains the analysis of the already created and used in the lab T type systems, their characteristics and... [to full text]

Current physical supports used in cryogenic storage vessels, in which liquid hydrogen is stored, conduct heat from the environment to the liquid hydrogen which causes the hydrogen temperature to rise and ultimately leads to hydrogen losses due to boil-off. The focus of this study is to investigate magnetic levitation as a possible suspension mechanism, eliminating the use of current physical supports and so doing reducing hydrogen losses due to boil-off. A conceptual design of a container which makes use of magnetic suspension is presented in this study. The concept is validated on the basis of the forces obtainable between a paramagnetic aluminium plate and an electromagnet, as well as the forces obtainable between a neodymium magnet and a bulk Yttrium-Barium-Copper-Oxide superconductor. The forces between the paramagnetic aluminium plate and electromagnet were determined mathematically and tested experimentally. The forces between the magnet and superconductor were determined mathematically and by finite element modelling and simulations using ANSYS Multiphysics. The results obtained in the mathematical- and finite element studies were then validated experimentally. It was found that the forces obtained experimentally between the aluminium plate and electromagnets are inadequate for magnetic suspension of the inner vessel given in the conceptual design. It was also found that the forces obtained experimentally and in the simulation studies for the magnet and superconductor of this study were inadequate due to shortcomings in the magnet and superconductor obtained for experimental tests. The conclusion of this study is that electromagnetic levitation should not be used as a magnetic suspension mechanism for storage of liquid hydrogen. It is also concluded that superconducting levitation can not be used as a suspension mechanism for the concept presented in this study, unless the methods suggested to increase the levitation forces between the neodymium magnet and superconductor are executed. / Thesis (MIng (Mechanical Engineering))--North-West University, Potchefstroom Campus, 2013

Current physical supports used in cryogenic storage vessels, in which liquid hydrogen is stored, conduct heat from the environment to the liquid hydrogen which causes the hydrogen temperature to rise and ultimately leads to hydrogen losses due to boil-off. The focus of this study is to investigate magnetic levitation as a possible suspension mechanism, eliminating the use of current physical supports and so doing reducing hydrogen losses due to boil-off. A conceptual design of a container which makes use of magnetic suspension is presented in this study. The concept is validated on the basis of the forces obtainable between a paramagnetic aluminium plate and an electromagnet, as well as the forces obtainable between a neodymium magnet and a bulk Yttrium-Barium-Copper-Oxide superconductor. The forces between the paramagnetic aluminium plate and electromagnet were determined mathematically and tested experimentally. The forces between the magnet and superconductor were determined mathematically and by finite element modelling and simulations using ANSYS Multiphysics. The results obtained in the mathematical- and finite element studies were then validated experimentally. It was found that the forces obtained experimentally between the aluminium plate and electromagnets are inadequate for magnetic suspension of the inner vessel given in the conceptual design. It was also found that the forces obtained experimentally and in the simulation studies for the magnet and superconductor of this study were inadequate due to shortcomings in the magnet and superconductor obtained for experimental tests. The conclusion of this study is that electromagnetic levitation should not be used as a magnetic suspension mechanism for storage of liquid hydrogen. It is also concluded that superconducting levitation can not be used as a suspension mechanism for the concept presented in this study, unless the methods suggested to increase the levitation forces between the neodymium magnet and superconductor are executed. / Thesis (MIng (Mechanical Engineering))--North-West University, Potchefstroom Campus, 2013

No description available.

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1991. / Vita. Abstract. Includes bibliographical references (leaves 70-73). Also available via the Internet.