• Title/Summary/Keyword: 유연 회전체

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Rotordynamics of a Centrifuge Rotor-Bearing System for 100,000RPM Operation (10만 RPM용 원심분리기의 로터베어링계 설계)

  • 이안성;김영철;박종권
    • 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.

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A study on the Active Control for Flexible Rotors Using Phase Control Method (위상 조절방법에 의한 유연 회전체의 능동제어에 관한 연구)

  • Lee W.C.;Kim S.W.;Kim J.S.;Park H.O.
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 2005.06a
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    • pp.280-283
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    • 2005
  • This study performed by a previous research for the applying expert system to active vibration control algorithm. In order to increase productivity and efficiency, high-speed rotating machines become popular these days. They are likely to vibrate and cause machine failure even though they have small unbalance. Therefore, a high-speed rotating machine needs a balancing technique. ISO 11342 classifies flexible rotors in accordance with their balancing requirements and establishes methods of assessment of residual unbalance. But, even if they finished balancing work, they have harmful effect vibration under the high-speed rotating environment. This vibration effect is very small, but it must be removed for the improvement of the rotor's spin accuracy. This paper introduces a new active control method that remove the exciting force by a phase control. For this method, the high-speed rotating rotor was reconstructed by a flexible rotor model. The forces which excite the rotating system suppose cyclic forces, we obtain the responses by numerical method. And then through the pattern analysis about the vibraton responses, the controler generate the control force with the reverse phase and similar magnitude. This paper suggest an phase control method and shows how to improve the rotating vibration accuracy of the flexible rotor dynamics system using phase control method.

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Finite Element Analysis of Unbalance Response of a High Speed Flexible Polygon Mirror Scanner Motor Considering the Flexibility of Supporting Structure (지지구조의 유연성을 고려한 고속 유연 폴리곤 미러 스캐너 모터의 유한 요소 불평형 응답 해석)

  • Jung, Kyung-Moon;Seo, Chan-Hee;Kim, Myung-Gyu;Jang, Gun-Hee
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2007.05a
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    • pp.859-865
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    • 2007
  • This paper presents a method to analyze the unbalance response of a high speed polygon mirror scanner motor supported by sintered bearing and flexible supporting structures by using the finite element method and the mode superposition method. The appropriate finite element equations for polygon mirror are described by rotating annular sector element using Kirchhoff plate theory and von Karman non-linear strain, and its rigid body motion is also considered. The rotating components except for the polygon mirror are modeled by Timoshenko beam element including the gyroscopic effect. The flexible supporting structures are modeled by using a 4-node tetrahedron element and 4-node shell element with rotational degrees of freedom. Finite element equations of each component of the polygon mirror scanner motor and the flexible supporting structures are consistently derived by satisfying the geometric compatibility in the internal boundary between each component. The rigid link constraints are also imposed at the interface area between sleeve and sintered bearing to describe the physical motion at this interface. A global matrix equation obtained by assembling the finite element equations of each substructure is transformed to a state-space matrix-vector equation, and both damped natural frequencies and modal damping ratios are calculated by solving the associated eigenvalue problem by using the restarted Arnoldi iteration method. Unbalance responses in time and frequency domain are performed by superposing the eigenvalues and eigenvectors from the free vibration analysis. The validity of the proposed method is verified by comparing the simulated unbalance response with the experimental results. This research also shows that the flexibility of supporting structures plays an important role in determining the unbalance response of the polygon mirror scanner motor.

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Vibration Analysis of Flexible Rotor Having a Breathing Crack (개폐균열이 존재하는 유연 회전체의 진동해석)

  • Jun, Oh-Sung
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.15 no.10 s.103
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    • pp.1137-1147
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    • 2005
  • The dynamic response due to the unbalance and crack and the quasi-static response due to gravity are analytically derived based on the complex transfer matrix. The additional slope is expressed as function of the bending moment at crack position based on the fracture mechanics concept, and inversely the bending moment is expressed as function of the additional slope at the crack Position. At each angle step during the shaft revolution, the additional slope and bending moment are calculated by an iterativemethod. The transient behavior is considered by introducing Fourier series expansion concept for the additional slope. Simulation is carried out for a simple rotor similar to those available in the literature and comparison of the basic crack behavior is shown. Using the additional slope, the cracked rotor behavior is explained with the crack depth increased: the magnitude of the additional slope increases and the closed crack duration during a revolution decreases as the crack depth increases. The direction of unbalance is also shown as a factor to affect the crack breathing. Whirl orbits are shown near the sub-critical speed ranges of the rotor.

Rotordynamics of a Centrifuge Rotor-Bearing System for 100,000 rpm Operation (100,000 rpm 운전용 원심분리기 로터-베어링 시스템의 회전체동역학 해석)

  • 이안성;김영철;박종권
    • Journal of KSNVE
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    • v.8 no.3
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    • pp.450-456
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    • 1998
  • A rotordynamic analysis is performed with a centrifuge rotor-bearing system for the raing speed of 100,000 rpm. The system is composed of a centrifuge rotor(or simply the rotor), flexible shaft, motor rotor and shaft, and two support rolling element bearings of the motor shaft. Design goals are to achieve wide separation margins of critical speeds and favorable unbalance responses of the rotor at the associated critical speeds. The latter requirements are especially important as the system crosses multiple numbers of critical speeds and as the system may not have enough separaton margins around the rating speed. As the system adopts an extra-flexible shaft, it is shown that the rotor has satisfactory small unbalance responses over higher criticals while having an unsatisfactory large one at the first critical. To supress this a bumper ring or guide bearing needs to be installed at a suitable location of the flexible shaft. It is also shown that even with the flexible shaft the dynamics of the motor must be incoporated into the full system model to accurately identify the fourth critical speed, which is close to the rating speed, and higher ones. The analysis is based on the finite element method.

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Finite Element Modal Analysis of a Spinning Flexible Disk-Spindle System Considering the Flexibility of Supporting Structures and an Head-Suspension-Actuator in a HDD (지지구조와 헤드-서스펜션-액츄에이터의 유연성을 고려한 HDD 유연 회전 디스크-스핀들 시스템의 유한 요소 고유 진동 해석)

  • Seo, Chan-Hee;Lee, Ho-Sung;Sang, Gun-Hee
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2006.11a
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    • pp.128-135
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    • 2006
  • This paper presents a finite element method to analyze the free vibration of a flexible HDD composed of the spinning disk-spindle system with fluid dynamic bearings(FDBs), the head-suspension-actuator with pivot bearings, and the base plate with complicated geometry. Experimental modal testing shows that the proposed method well predicts tue vibration characteristics of a HDD. This research also shows that even the vibration motion of the spinning disk corresponding to half-speed whirl and the pure disk mode are transferred to a head-suspension-actuator and base plate through the air bearing and the pivot bearing consecutively. The proposed method can be effectively extended to investigate the forced vibration of a HDD and to design a robust HDD against shock.

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Finite Element Modal Analysis of a Spinning Flexible Disk-spindle System Considering the Flexibility of Supporting Structures and an Head-suspension-actuator in a HDD (지지구조와 헤드-서스펜션-액추에이터의 유연성을 고려한 HDD 유연 회전 디스크-스핀들 시스템의 유한 요소 고유 진동 해석)

  • Seo, Chan-Hee;Lee, Ho-Sung;Jang, Gun-Hee
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.17 no.1 s.118
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    • pp.24-32
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    • 2007
  • This paper presents a finite element method to analyze the free vibration of a flexible HDD composed of the spinning disk-spindle system with fluid dynamic bearings(FDBs), the head-suspension-actuator with pivot bearings, and the base plate with complicated geometry. Experimental modal testing shows that the proposed method well predicts the vibration characteristics of a HDD. This research also shows that even the vibration motion of the spinning disk corresponding to half-speed whirl and the pure disk mode are transferred to a head-suspension-actuator and base plate through the air bearing and the pivot bearing consecutively. The proposed method can be effectively extended to investigate the forced vibration of a HDD and to design a robust HDD against shock.

Finite Element Modal Analysis of a Spinning Flexible Disk-Spindle System Considering the Flexiblity of Supporting Structures and an Actuator in a HDD (지지구조와 액츄에이터의 유연성을 고려한 HDD 유연 회전 디스크-스핀들 시스템의 유한 요소 고유 진동 해석)

  • Seo, Chan-Hee;Lee, Chang-Suk;Jang, Gun-Hee;Lee, Ho-Sung
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2005.11a
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    • pp.330-336
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    • 2005
  • This paper presents a method to analyze the vibration of a flexible spinning disk-spindle system with FDBs, flexible base structure and an actuator in a HDD by using the FEM. Finite element equations of each component of a HDD spindle system from the spinning flexible disk to the flexible base plate are consistently derived by satisfying the geometric compatibility in the internal boundary between each component. A global matrix equation obtained by assembling the finite element equations of each substructure is transformed to a state-space matrix-vector equation, and both damped natural frequencies and modal damping ratios are calculated by using the restarted Arnoldi iteration method. The validity of the proposed method is verified by comparing the simulated natural frequencies, mode shapes with the experimental results.

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Characteristics of Directional Squeeze Film Damper Using ER Fluid (ER유체를 이용한 이방성 스퀴즈필름 댐퍼의 특성)

  • 안영공;양보석;삼하신
    • Journal of KSNVE
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    • v.11 no.2
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    • pp.301-306
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    • 2001
  • Electro-Rheological (ER) fluid is applied to a controllable squeeze film damper (SFD) for stabilizing a flexibly supported rotor system. ER fluid is a class of functional fluid whose yield stress varies according to the applied electric field strength, which is observed as viscosity variation of the fluid. In applying ER fluid to a SFD, a pair of rings of the damper can be used as electrodes. When the electrodes are divided into a horizontal pair and a vertical one, the SFD can produce damping force in each direction independently. A prototype of the directionally controllable SFD was constructed and its performance was experimentally and numerically investigated in the present work.

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Controller Design and Validation of Radial Active Magnetic Bearing Systems Considering Dynamical Changes Due To Rotational Speeds (회전속도에 따른 동역학적 변화를 고려한 반경방향 능동 자기베어링 시스템의 제어기 설계 및 검증)

  • Jeong, Jin Hong;Yoo, Seong Yeol;Noh, Myounggyu
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.38 no.9
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    • pp.925-932
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    • 2014
  • If a rotor possesses a high gyroscopic coupling or the running speed is high, the dynamical changes in the rotor become prominent. When active magnetic bearings are used to support such rotors, it is necessary for the bearing controller to take these dynamical changes into consideration. Independent-axis controllers, which are the most commonly used, modulate the bearing force solely based on the sensor output of the same axis. However, this type of controller has difficulties in overcoming the dynamical changes. On the other hand, mixed-axis controllers transform the sensor output into components corresponding to the vibrational modes. A separate controller can then be designed for each vibrational mode. In this way, the controller can be designed based on the dynamics of the rotor. In this paper, we describe a design process for a mixed-axis controller that uses a detailed mathematical model of the system. The performance of the controller is evaluated based on the ISO sensitivity requirements and unbalance response, while considering the change in the system dynamics due to the running speed.