• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2013.04a
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• pp.676-677
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• 2013

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.2 s.173
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• pp.355-361
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• 2000

In this study, active control magnetic actuator for reducing vibration of rotor system is performed. Identification, modeling, simulation, control system design, and evaluation of active magnetic damper system have been researched. Power amplifier modeling, connected magnetic actuator and augmented by system identification, is included to establish a magnetic damper simulation which provides close performance correspondence to the physical plant. A magnetic actuator, digital controller using DSP(Digital Signal Processor), and bipolar operational power supply/amplifiers are developed to show the effectiveness of reducing rotor vibration. Also the curve fitting procedure to obtain the transfer function of frequency dependent components is developed. Two kinds of test are executed as sliding and oil bearing. Results presented in this paper will provide a well-defined technical parameters in designing magnetic damper system for the proposed rotor.

• 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 KIEE Conference
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• 1999.11d
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• pp.1164-1166
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• 1999

본 연구에서는 3차원 회전체 구조물을 제조하기 위해 회전노광장치를 설계하여 제작하고 마이크로렌즈 제작용 X-선 마스크와 PMMA 기판을 정밀하게 회전시켜 노광함으로써 3차원의 마이크로렌즈를 제작하였다. 제작된 마이크로렌즈의 크기는 직경이 $50{\sim}700{\mu}m$이었고, 또한 이러한 방법으로 원통형 렌즈, 계란형 렌즈 등을 제작함으로써 X-선 사진식각공정으로 정밀도가 높은 다양한 3차원의 회전체 구조물을 제조하는 방법을 제시하였다.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.18-19
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• 2015

본 논문에서는 회전체에 붙어있는 센서에 전원을 공급하기 위하여 전자기 공진형 무선전력전송을 사용하고 있다. 회전체는 철제 스핀들로 만들어 졌으며, 스핀들 표면에 수전기를 부착하여 무선전력을 수전하고 있다. 송전기에 무선전력을 송전하고 수전기에서 전력을 수전하고자 할 때, 철제 스핀들 때문에 전력 전달효율이 감소된다. 따라서 최적의 전력전달 조건을 찾아 송전기와 수전기의 위치 및 크기를 설계하여야 한다. 본 논문에서는 송전기의 위치를 변화시키고, 수전기의 각도를 변화시키면서 송 수전기 간의 전력전달 특성을 연구하였다.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.05a
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• pp.271-276
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• 2006

This paper shows the rotordynamic characteristics of a turbo-generator for a BOP of a fuel cell system. The rotor-bearing system consists of magnetic shaft and compressor-turbine shaft, and the two shafts are connected by spline coupling and supported by oil free air foil bearing. Preliminary design according to several parameter is considered in detail. Static and dynamic characteristics of the AFB are estimated by the soft elasto-hydrodynamic analysis technique and the perturbation method. The results of the natural frequencies, mode shape, and unbalance response analysis are presented.

• 유체기계공업학회:학술대회논문집
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• 2003.12a
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• pp.662-667
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• 2003

This paper presents a performance analysis of the 1st generation bump foil journal bearings for the micro gas turbine TG75. Static performances such as load capacity and attitude angle are estimated by using soft elasto-hydrodynamic analysis technique, and dynamic performances such as stiffness and damping coefficients are estimated by perturbation method. Rotordynamic analysis for TG75 is performed by using the bearing analysis results. TG75 rotor has 2 horizontal and vertical directional natural modes due to the bearing stiffness characteristics. TG75 rotor will be stably operated between the 1st bending mode at 33000cpm and the 2nd bending mode at 85500cpm. Unbalance response analysis results satisfy the API vibration criteria.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.12 no.5
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• pp.380-388
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• 2002

This paper describes the optimum design for low-pressure steam turbine rotor of 1,000 MW nuclear power plant by using a combined genetic algorithm, which uses both a genetic algorithm and a local concentrate search algorithm (e.g. simplex method). This algorithm is not only faster than the standard genetic algorithm but also supplies a more accurate solution. In addition, this algorithm can find the global and local optimum solutions. The objective is to minimize the resonance response (Q factor) and total weight of the shaft, and to separate the critical speeds as far from the operating speed as possible. These factors play very important roles in designing a rotor-bearing system under the dynamic behavior constraint. In the present work, the shaft diameter, the bearing length, and clearance are used as the design variables. The results show that the proposed algorithm can improve the Q factor and reduce the weight of the shaft and the 1st critical speed.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2014.10a
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• pp.311-313
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• 2014

전동기는 산업 전 분야에 걸쳐 다양하게 사용되는 회전기기로서, 소형화, 경량화, 고속화하는 추세에 있다. 이는 전동기 프레임의 구조강성을 약화시키고, 축계 위험속도를 낮춤으로써 진동에 취약한 구조를 가지게 된다. 회전체 진동 관련 규정 중 API 684 에서는 베어링 지지강성이 베어링 강성에 비해 3.5 배 이하인 경우 베어링 지지강성이 위험 속도 해석 모델에 포함되어야 함을 명시하고 있다. 산업 현장에서는 베어링 지지강성을 정확하게 산출하기 어려워 이를 고려하지 않고 회전체를 설계하는 경우가 많아 실제 조건에서 예측하지 못한 진동 문제가 발생할 가능성이 있다. 본 논문에서는 전동기 베어링 하우징 및 프레임에 대한 가진 시험을 통해 얻은 주파수 응답함수의 실수부를 분석하여 베어링 지지강성을 추출하는 방법을 제시하였다. 이를 바탕으로 유한요소 해석모델을 이용하여 베어링 지지강성을 해석적으로 예측하는 기법을 정립하였다. 추출된 베어링 지지강성을 축계 해석 모델에 포함하여 베어링 지지강성 포함 유무에 따른 축계 위험속도 및 안정성을 비교하였다. 그 결과 베어링 지지강성을 포함한 경우, 보다 정확한 위험속도 및 진동응답 수준을 예측할 수 있음을 확인하였다.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.20 no.8
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• pp.25-32
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• 2021

Washboarding is a crucial problem occurring on unpaved roads. This phenomenon involves the formation of ripples on the surface of the unpaved road and causes a critical problem to vehicles and riders. The phenomenon is affected by several parameters, but we focused on the velocity and the size of the rotating body. In the precedent research, we observed that a critical velocity existed for the occurrence of the phenomenon, and the phenomenon's grade was related to the velocity. Therefore, this study, using a discrete element method, aimed to analyze the relation between the velocity and the size of the rotating body for the occurrence of the phenomenon and perform a fast Fourier transform (FFT) analysis to determine the correlation between the phenomenon and the period. The study observed that the critical velocity could vary from the velocity and the size of the rotating body, and there was a certain range of frequency for the occurrence of the Washboarding phenomenon.