• Title/Summary/Keyword: Magnetic suspension

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Rheological Characteristics of Magnetic $\gamma$-$Fe_{2}O_{3}$ and $CrO_2$ Particle Suspension (자성 $\gamma$-$Fe_{2}O_{3}$$CrO_2$ 입자 분산액의 유변특성 연구)

  • 김철암;이준석;최형진
    • The Korean Journal of Rheology
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    • v.11 no.2
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    • pp.128-134
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    • 1999
  • Rheological characterization was examined for two different types of magenetic particle (rod-like $\gamma$-$Fe_{2}O_{3}$, $CrO_2$ )suspension in this study. The measured suspension viscosity (viscosity vs. concentration or shear rate) is used to obtain the dependence of viscous energy dissipation on the microstructural states of magnetic particle dispersions as well as the microstructural shape effects which are related to magnetic particle orientation. The empirical formulas from mean field theory and the Mooney equation are used to relate suspension viscosity to particle concentration. Intrinsic viscosities of these two different types of rod-like magnetic particle suspensions are found to exceed the prediction of hydrodynamic theory for dilute suspensions and support the existence of flocs containing significant amounts of immobilized suspending medium due to native attraction forces among particles in the microstructures.

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Reduced-order Mapping and Design-oriented Instability for Constant On-time Current-mode Controlled Buck Converters with a PI Compensator

  • Zhang, Xi;Xu, Jianping;Wu, Jiahui;Bao, Bocheng;Zhou, Guohua;Zhang, Kaitun
    • Journal of Power Electronics
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    • v.17 no.5
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    • pp.1298-1307
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    • 2017
  • The constant on-time current-mode controlled (COT-CMC) switching dc-dc converter is stable, with no subharmonic oscillation in its current loop when a voltage ripple in its outer voltage loop is ignored. However, when its output capacitance is small or its feedback gain is high, subharmonic oscillation may occur in a COT-CMC buck converter with a proportional-integral (PI) compensator. To investigate the subharmonic instability of COT-CMC buck converters with a PI compensator, an accurate reduced-order asynchronous-switching map model of a COT-CMC buck converter with a PI compensator is established. Based on this, the instability behaviors caused by output capacitance and feedback gain are investigated. Furthermore, an approximate instability condition is obtained and design-oriented stability boundaries in different circuit parameter spaces are yielded. The analysis results show that the instability of COT-CMC buck converters with a PI compensator is mainly affected by the output capacitance, output capacitor equivalent series resistance (ESR), feedback gain, current-sensing gain and constant on-time. The study results of this paper are helpful for the circuit parameter design of COT-CMC switching dc-dc converters. Experimental results are provided to verify the analysis results.

Modeling and Analysis of Electromagnets for Magnetic Suspension System (흡인식 자기 부상 시스템을 위한 전자석의 모델링 및 해석)

  • 이상헌;백윤수
    • Journal of the Korean Society for Precision Engineering
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    • v.20 no.5
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    • pp.180-188
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    • 2003
  • In the precision motion device, the frictional problem by mechanical friction causes serious effects on the system performance. Various researches have been executed to solve this problem, but classical fluid lubrication method has some disadvantages in precision motion under clean environment. Therefore, the magnetic bearing and contact-free systems have been focused on with its pollution-free characteristics. In this paper, we treat modeling and analysis of electromagnets not only for magnetic bearing but also fer contact-free electromagnetic actuators. Three types of electromagnet for various applications are modeled and analyzed by magnetic circuit theory and the validity is verified by experiments.

Modeling and Aalyzing Electromagnets for Magnetic Suspension Systems

  • Lee, Sang-Heon;Baek, Yoon-Su;Jung, Kwang-Suk
    • International Journal of Precision Engineering and Manufacturing
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    • v.7 no.4
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    • pp.28-33
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    • 2006
  • Various precision engineering studies have attempted to remove mechanical friction, which causes the performance of a system to deteriorate, from precision positioning devices. Since the classical fluid lubrication method has some disadvantages in clean environments, attention has been focused on magnetic bearings and contact-free systems with their pollution-free characteristics. In this paper, f electromagnets are modeled and analyzed, not only for magnetic bearings but also for contact-free electromagnetic actuators. Three types of electromagnets that are appropriate for various applications were considered using magnetic circuitry theory. The results were experimentally validated.

A Study on the Design of Robust Controller of Magnetic Levitation System(II) (자기부상 시스템에 강인한 제어기 설계에 관한 연구 (II) - 실험을 중심으로 -)

  • 김창화;양주호;김영복
    • Journal of Advanced Marine Engineering and Technology
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    • v.20 no.3
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    • pp.144-153
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    • 1996
  • The magnetic levitation system has many advantages, such as little friction, no lubrication, no noise and so on. For this reason, the magnetic levitation system is utilized in the magnetic bearing of high-speed rotor. The method to obtain magnetic force is both the repulsive suspension method and the attraction suspension method need a stabilizing controller because it is a unstable system in natural. This paper presents the design of robust stabilizing servo controller in spite of being the model uncertainties in the magnetic levitation system by $\textit{H}_{\infty}$ control theory using the free parameter. And we investigated the validity of a designed controller through results of the simulation and the actual experiment.

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Development of a Simulator of a Magnetic Suspension and Balance System

  • Lee, Dong-Kyu;Lee, Jun-Seong;Han, Jae-Hung;Kawamura, Yoshiyuki;Chung, Sang-Joon
    • International Journal of Aeronautical and Space Sciences
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    • v.11 no.3
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    • pp.175-183
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    • 2010
  • The increased demand for a higher performing magnetic suspension and balance system (MSBS) resulted in an increase in costs for the efforts necessary for achieving an improved MSBS. Therefore, MSBS performance should be predicted during the design in order to reduce risk. This paper presents the modeling and simulation of an MSBS that controls 6-degree of freedom (DOF) of an aerodynamic body within the MSBS. Permanent magnets and electromagnets were modeled as coils, and this assumption was verified by experimental results. Finally, an MSBS simulator was developed, predicting that the MSBS is able to contain the model within a bounded region as well as measure external forces acting on the body during wind tunnel tests.

A Study on the Influence of Q-filter on Disturbance Observer Controller for Electro-Magnetic Suspension Systems (자기부상시스템의 외란관측기 제어기에 Q 필터가 미치는 영향에 관한 연구)

  • Jeon, Chanyoung;Jang, Sohyun;Jo, Nam-Hoon
    • Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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    • v.29 no.10
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    • pp.104-110
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    • 2015
  • The disturbance observer (DOB) controller has been widely used in various industrial applications since it is capable of achieving robust stability and disturbance rejection. In this paper, we study the effect of Q-filter on disturbance observer controller for Electro-Magnetic suspension (EMS) systems. We consider three Q-filters and analyze their effects on the robust stability against parameter uncertainties due to mass variation. Moreover, we investigate the influence of sensor noise for three Q-filters. According to our study, robust stability improves as the order of Q-filter decreases. On the other hand, the larger the order of Q-filter, the more the effect of sensor noise can be removed.

Fishing Effect of BiPbSrCaCuO Superconductor (BiPbSrCaCuO 초전도체의 Fishing 효과)

  • Lee, Sang-Heon
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2004.05b
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    • pp.177-179
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    • 2004
  • Suspension effect has been studied by using superconductor of BiPbSrCaCuO ceramics containing $Ag_2O$. It has been cleared that $Ag_2O$ acts as pinning center which plays an important role to the suspension effect. Magnetic repulsive force which affects a superconductor located in magnetic flux from toroidal magnet has been investigated. It has been concluded that the suspension effect arises from the interaction between the pinning effect and the diamagnetic effect.

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The Design and Performance Evaluation of a Parallelogram Type Magnetic Spring Suspension for Commercial Vehicle Seat (상용차 시트용 평행사변형구조 마그네틱 현가기구의 설계 및 성능평가)

  • Kwac, Lee Ku;Kim, Hong Gun;Shin, Hee Jae;Jung, Young Bae;Song, Jung Sang
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.39 no.4
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    • pp.353-360
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    • 2015
  • Commercial drivers feel tired more than the general public, because their driving times are long and they experience more idle vibration. In this study, we developed a nonlinear model of a magnetic, linear spring seat suspension to determine the optimal design to improve ride comfort. The resonant frequency for the optimal design of the suspension was found to be 3.5 Hz, and the stiffness was analyzed through displacement-load experiments. Additionally, the vibration transmissibility was analyzed by the suspension stiffness, and the existing coil spring type vibration transmissibility was found to be 0.99. A parallelogram type magnetic spring was determined to result in a better performance than the existing spring with a vibration transmissibility of 0.823.

Optimal Design and Performance Evaluation of X-type Magnetic Spring Suspension for Commercial Vehicle Seat (상용차 시트용 X-형 구조 마그네틱 현가기구의 최적 설계 및 성능평가)

  • Kwac, Lee Ku;Kim, Hong Gun;Song, Jung Sang;Shin, Hee Jae;Seo, Min Kang;Kim, Byung Ju;An, Kay Hyeok;Lee, Hye Min;Han, Woong
    • Journal of the Korean Society of Manufacturing Technology Engineers
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    • v.23 no.5
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    • pp.456-464
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    • 2014
  • Commercial vehicle drivers typically feel more fatigued compared to general-public drivers. because they spend longer periods of time driving and experience more rough road conditions. This study showed that the application of a magnet, a linear spring, and a seat suspension with nonlinear characteristics was the optimal design to increase comfort while driving. The resonant frequency for the optimal design suspension was 2.8 Hz, and the stiffness was analyzed through displacement-load experiments. Vibration transmissibility was analyzed by suspension stiffness and the existing dynamic compression. The magnetic spring type was at 0.875. As a result, the X-type magnetic spring performed better than the existing spring at 0.729.