• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1990.10a
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• pp.193-198
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• 1990

전자기 베어링은 기계적 접촉이 없고 전기적 제어가 가능하여 최근 고속 정 밀 회전기에 사용되고 있다. 본 논문에서는 능동 자기베어링을 모형화하고 제어 이득에 따른 계의 안정성 판별 및 응답특성의 변화를 고찰하였다. 이를 토대로 두개의 반경방향 베어링과 회전체를 제작하고 아날로그 제어회로를 구성하여 안정되게 회전체를 부상시킬수 있었으며 이로부터 계의 응답특성 을 구하였다.

• Transactions of the Korean Society of Mechanical Engineers
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• v.12 no.5
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• pp.976-983
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• 1988

An efficient unbalance response analysis method for rotor-bearing systems with spin speed dependent parameters is developed by utilizing a generalized modal analysis scheme. The spin speed dependent eigenvalue problem of the original system is transformed into the spin speed independent eigenvalue problem by introducing a lambda matrix, assuming the bearing dynamic coefficients are well approximated by polynomial functions of spin speed. This method features that it requires far less computational effort in unbalance response calculations and that the influence coefficients are readily available. In addition, the critical speeds and the corresponding logarithmic decrements can be readily identified from the resulting eigenvalues.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1996.04a
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• pp.60-66
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• 1996

축어긋남이 존재하는 회전체-볼베어링계의 진동을 묘사할 수 있는 모델을 개발하였다. 축어긋남은 운동 방정식에서 축과 베어링에서의 변위벡터 변화로 묘사되고, 이로 인해 커플링과 베어링에 작용하는 힘과 모멘트는 축어긋남의 효과로서 고려되었다. 축의 유연성을 고려하기 위해 축방향의 동력학을 포함한 축과 원판에 대한 유한 요소 모델을 이용하였으며, 원판과 베어링에서의 불균형 응답으로부터 축어긋남과 관련된 진동특성을 조사하였다.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1991.04a
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• pp.91-93
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• 1991

DARBS는 저널베어링 및 구름베어링에 지지되어 있는 회전체-베어링계에 대한 동력학적 해석을 수행하는 프로그램이다. 해석에는 유한요소법(finite element method)을 이용하며 선회속도(whirl speed), 모우드 형성(mode shape), 임계속도(ciritical speed) 그리고 비동기 가진응답(asynchronous response)등에 대한 해석결과를 제공한다. 본 프로그램의 주된 특징은 람다 행렬(lambda matrices)의 개념을 도입하여 비동기 가진응답의 해석에 적용하 고, 베어링 상수와 자이로 효과와 같은 회전속도 의존성에 대하여 체계적인 접근방법을 사용했다는 점이다. 본 프로그램은 IBM PC 및 호환 기종에 적 합하도록 개발되었으며 기본적인 출력장치를 지원하는 S/W가 포함되어 있 다. 또한 대화식 데이타 입력과 메뉴처리방식을 채택하여 사용하기 편리하게 하였으며, 오류발생시 메세지가 나타나 오류수정을 용이하게 하였다.

• Journal of the Korean Society for Precision Engineering
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• v.12 no.9
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• pp.137-147
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• 1995

The unbalance response analysis is one of the essential area in the forced vibration analysis of rotor-bearing systems. Local bearing parameters in rotor-bearing systems are the major sources which give rise to a difficulty in unbalance response computation due to the complicated dynamic properties such as rotational speed dependency and anisotropy. In the present paper, an efficient method for unbalance responses is proposed so as to easily take into account bearing parameters in computation. An exact matrix condensation procedure is proposed which enables the present method to compute unbalance responses by dealing with condensed, small matrices. The proposed method causes no errors even though the computation procedure is based on the small matrices condensed from the full matrices. The present method is illustrated through a numerical example and compared with the conventional method.

• Journal of KSNVE
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• v.9 no.3
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• pp.525-534
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• 1999

The present paper proposes a generalized modal analysis procedure for non-uniform, distributed-parameter rotor-bearing systems. An exact element matrix is derived for a Timoshenko shaft model which contains rotary inertia, shear deformation, gyroscopic effect and internal damping. Complex coordinates system is adopted for the convenience in formulation. A generalized orthogonality condition is provided to make the modal decomposition possible. The generalized modal analysis by using a modal decomposition delivers exact and closed form solutions both for frequency and time responses. Two numerical examples are presented for illustrating the proposed method. The numerical study proves that the proposed method is very efficient and useful for the analysis of distributed-parameter rotor-bearing systems.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.10a
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• pp.389-392
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• 1997

This paper presents the dynamic analysis and experiment for rotor systems supported by angular contact ball bearings subjected to axial displacement preload. A dynamic software, which has been developed by the authors for the analysis of rotor systems supported by angular contact ball bearings, is used to simulate a uniform shaft system supported by two angular contact ball bearings with the axial displacement preload varied. Experiments are also performed to validate the simulation. An experimental system is constructed which consists of a uniform shaft, two bearings and a device for adjusting the axial displacement preload. Through a series of simulation and experiment, the dynamic characteristics of rotor systems with angular contact ball bearings subject to axial displacement preload are investigated.

• Transactions of the Korean Society of Mechanical Engineers
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• v.12 no.3
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• pp.409-418
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• 1988

Steam turbines, gas turbines, multistage centrifugal compressors are operated over the range of the first critical speed. In these rotors flexible rotor balancing technique is necessary. In such balancing, influence coefficients are measured by rotating a rotor with trial weight. But for the large rotor, the measurement of influence coefficient takes much time and it reduces the cost efficiency. In this paper the new influence coefficient with rotation of rotor is proposed. First the theoretical background of the method is presented and it is applied to the simple flexible rotor model. Then the experiments are performed and the results of presented method are compared with those of analytical method. By using the obtained influence coefficient, balancing of the flexible rotor is performed.

• Journal of KSNVE
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• v.6 no.1
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• pp.71-82
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• 1996

The finite element analysis for rotor bearing systems has been an essential tool for design, identification, and diagnosis of rotating machinery. Among others, the unbalance response analysis is fundamental in the vibration analysis of rotor bearing systems because rotating unbalance is recognized as a common sourve of vibration in rotating machinery. However there still remains a problem in the aspect of computational efficiency for unbalance response analysis of large rotor bearing systems. Gyroscopic terms and local bearing parameters in rotor bearing systems often make matters worse in unbalance response computation due to the complicated dynamic properties such as rotational speed dependency and/or anisotropy. The present paper proposes an efficient method for unbalance responses of multi-span rotor bearing systems. An improved substructure synthesis scheme is introduced which makes it possible to compute unbalance responses of the system by coupling unbalance responses of substructures that are of self adjoint problem with small order matrices. The present paper also suggests a scheme to easily deal with gyroscopic tems and local, coupling or bearing parameters. The proposed method causes no errors even though the computational effort is reduced drastically. The present method is demonstrated through three test examples.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1997.10a
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• pp.64-69
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• 1997

정격속도 100,000RPM용 원심분리기(centrifuge) 로터베어링계에 대해 회전체동역학 해석이 수행된다. 시스템은 원심분리기 로터, 유연축, 모터 로터와 축, 그리고 모터축 지지용 두 개의 구름베어링으로 구성된다. 설계목표는 정격속도가 위험속도(critical speed)에 대해 충분한 분리여유를 갖고, 위험속도에서 로터의 양호한 불균형응답특성을 이루어 내는 것이다. 후자의 요구조건은, 시스템이 다수의 위험속도를 통과하며 정격속도 주위에서 충분한 분리 여유를 갖지 않을 수도 있기 때문에 특히 중요하다. 시스템에 초유연축(extra-flexible shaft)을 도입함으로써, 비록 1차 위험속도에서 만족스럽지 못한 큰 불균형응답을 가질지라도 고차 위험속도에서 만족스런 작은 불균형응답을 보인다. 1차 위험속도에서 로터의 큰 변위를 억제하기 위해서 범퍼링(bumper ring) 또는 안내베어링(guide bearing)을 유연축의 적절한 위치에 설치할 필요가 있다. 비록 유연축계라 할지라도 정격속도와 가까운 4차 이상의 고차 위험속도를 정확히 규명하기 위해서는 모터의 동역학을 전체시스템에 결합하여야 함을 볼 수 있다. 해석은 유한요소법(finite element method)에 의해 수행된다.