• Proceedings of the Korean Society of Precision Engineering Conference
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• 1995.10a
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• pp.769-772
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• 1995

Most turbo machines, which operate at high speeds, such as gas turbines, jet engines, pumps, and compressors are prone to perrturbing vibrations. The best vibration control method for rotors is to eliminate destabilizing factors. Careful balancing application of "more stable" oil-lubricated bearing, such as tilting pad bearings or use of anti-swirl devices in seals, are examplse of passive vibration control methods. the use of magnetic bearing is an active control method. An obvious advantage of active control is that it provides damping (or modifies system stiffness or other parameters) only when there is a need for that, i.e., in emergency states, while not affecting the rotor normal operational conditions. Moreover, active control methods provide exact position control through on-line control. In this study, a magnetic actuator, digital contrliier using DSP, and bipolar operational power supply/amplifiers were developed to show the effectiveness of reducing robot vibration. Also the curve fitting procedure to obtain the transfer function of frequency dependent component was developed. Results presented in this dissertation will provide a well-defined technical parameters in designing magnetic damper system.er system.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2008.04a
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• pp.230-235
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• 2008

With the advent of the telecommunication era, a mobile phone becomes a necessary communication device in modern society. For silent tactile signal, vibration motors have become one of the generic components in most mobile phones. Conventional vibration motors employ three-phase windings with mechanical brushes for commutation. However, mechanical commutation in these prior arts greatly deteriorates its life span, reliability, and productivity due to structural intricacy. This paper introduces a novel design of solenoid-type vibrators using electromagnetic and mechanical analysis. The proposed vibrators have a simpler structure and longer life span by eliminating wear-prone commutation parts in vibration motors.

• Proceedings of the KIEE Conference
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• 2004.07d
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• pp.2389-2391
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• 2004

This paper is concerned with the active vibration control of plate system using electromagnetic force actuator. The transfer function from the force input to the bending displacement was obtained via modal analysis results. Control algorithm are proposed and implemented on the experimental setups to show their efficacy. In this paper, the genetic algorithm is used to design a $H_2$ controller. Effectiveness and performance of the designed controller were verified by simulation and experiment results.

• 제어로봇시스템학회:학술대회논문집
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• 2002.10a
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• pp.59.6-59
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• 2002

$\textbullet$ An experiment for the active vibration control of a cantilever beam is performed. $\textbullet$ An active damping system consisting of a laser sensor and an electromagnetic actuator. $\textbullet$ The design procedure and the performance analysis of an H2 controller for non-collocated systems. $\textbullet$ Simulations and experiments are performed to verify the performances of the controller. $\textbullet$ The optimal H2 controller is designed based on a reduced order model. $\textbullet$The Sensitivity function is introduced to analyze the Spillover phenomenon. $\textbullet$ Active vibration control, Cantilever beam, H2 controller, spillover, Non-collocated system.

• Journal of Mechanical Science and Technology
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• v.16 no.5
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• pp.633-638
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• 2002

An approach to enhance dimensional accuracy of the grinding process has been presented, and grinding of a glass material with a metal-bonded diamond wheel has been studied. In this study, a grinding tool is suspended flexibly and controlled by an electromagnetic actuator. During grinding, profile error of a ground surface is indirectly measured and fed back to a control system. A model of grinding error has been suggested on which the indirect measurement has been based. An optimal PID control is adopted and effectiveness of the in-process feedback control has been verified experimentally.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1995.04a
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• pp.252-257
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• 1995

전자기력을 이용한 능동 진동제어는 1979년 Ellis 및 Mote가 원형 톱의 횡 진동의 감쇠에 관한 연구를 수행하였고, 1990년 Hong Su 및 T.S.Sankar등은 시스템의 절대 위치, 절대 속도 및 상대 위치 등의 제어 변수에 대하여 전자기 액튜에이터의 동적 특성이 진동 절연 성능에 미치는 영향에 관한 연구를 하였다. 본 연구는 상부질량과 하부질량이 스프링으로 연결된 2자유도 모델의 능동 진동제어에 대하여 이론해석과 실험해석을 수행하고 각각의 결과를 비교하였다. 실험모델은 직선운동 가이드에 설치된 2개의 질량과 하나의 전자기 액튜에이터를 이용하였다. 진동제어 방법으로서는 모우드 해석에 의한 제어, 스카이 훅 감쇠 제어, Viscous damping 제어 방법을 적용하였다. 본 연구의 목적은 이론해석 결과와 실험 결과를 비교하고 비슷한 제어효과에 대해서 에너지 소비가 작은 효율적인 제어방법을 찾는데 있다.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.06a
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• pp.1338-1343
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• 2000

This paper deals with an application of Magneto-Rheological (MR) fluid to a small size mount for precision equipment of automobiles. MR fluid is known as a class of functional fluids with controllable apparent viscosity of fluid by the applied magnetic field strength. A typical MR fluid is a suspension where pure iron particles of $1{\sim}20mm$ in diameter are dispersed in a liquid such as mineral oil or silicone oil, at the concentration of $20{\sim}40$ vol%. Electro magnetic coil is installed at the bottom of a variable-damping mount filled with MR fluid, and its performance was investigated experimentally. Furthermore, the properties of the MR Mount on experimental Study were explained analytically by mechanical model of the MR mount.

• Proceedings of the KIEE Conference
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• 2008.10c
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• pp.80-82
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• 2008

고전압 가스차단기용 조작기로 개발된 전자석 조작기(EMFA)는 크기에 비해 큰 힘을 낼 수 있고 긴 스트로크를 갖는 장점으로 다양한 차단기에 적용이 시도되고 있다. 특히 기증차단기(ACB)와 배선용 차단기(MCCB) 등 저압 차단기를 구동하기 위한 연구가 진행중이다. 그러나 적용할 차단기의 전압 등급이 낮아짐에 따라 조작기의 크기 또한 작아져야 하며, 설계 및 해석시 고려해야 할 요소 또한 달라진다. 특히 조작기의 두께가 얇아지면서 코일의 엔드와인딩(end-winding)에 의한 영향이 상대적으로 커지게 되는데, 본 논문에서는 전자석 조작기의 동작 특성 해석시 엔드와인딩 인덕턴스를 고려한 2차원 해석을 시도하였다. 엔드와인딩 형상은 원형으로 가정하였고, 동작 특성 해석에는 유한요소법과 시간차분법을 적용하였다.

• Journal of KSNVE
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• v.5 no.1
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• pp.59-65
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• 1995

In this study, we investigated the operational limit of magnetic bearing-rotor system due to the maximum force limit and slew rjate limit of the electromagnetic actuator as a function of the time dependent control characteristics. The feedback gain of the controller varies the current of the electromagnet coil with the motion of the rotor. The distorsion of magnetic force due to the slew rate limit is not occurred jup to 30, 000 rpm in the magnetic bearing that we have a close relation with the rotational speed and vibration level of the rotor and the proportional gain of the controller. Therefore the maximum force limit determines the maximum allowable orbit radius of the magnetic bearing-rotor system. The maximum allowable vibration levels are exponentially decreased according to the increment of rotational speed and proportional gain of the controller.

• Wind and Structures
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• v.17 no.1
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• pp.107-121
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• 2013

This paper presents an experimental investigation concerning the peak amplitudes of oscillation of a square prism due to Vortex-Induced-Vibrations (VIV) as a function of the mass damping parameter $m^*{\zeta}$(the so called Griffin--plot); $m^*$ and ${\zeta}$ being, respectively, the non-dimensional mass and the mechanical (structural) damping ratio. With this purpose in mind, an electromagnetic actuator has been employed to provide controlled damping. During the experiments the mass--damping parameter was in the range 0.15 < $m^*{\zeta}$ < 2.4. Experiments show that there is a value of $m^*{\zeta}$ below which VIV appears combined with galloping and the prism oscillation increases monotonically with the incoming flow velocity. For $m^*{\zeta}$ >0.3 the present experiments show a well-defined VIV phenomenon and, consequently, a Griffin-plot can be defined.