• Tribology and Lubricants
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• 제5권2호
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• pp.101-106
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• 1989

Various squeeze film dampers have been theoretically and experimentally studied for flexible rotors. A cylindrical bush damper among them was selected and applied in a test rotor supported with ball bearings. A quiet running of the rotor over a critical speed was observed.

• 한국시뮬레이션학회논문지
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• 제8권3호
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• pp.39-48
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• 1999

A finite element model of geared rotor system with flexible bearings were used to simulate the critical speeds and to investigate the effects of bearing coefficients on the dynamic behaviors of the systems. The finite element model includes the effects of tooth mesh stiffness, gyroscopic moment, rotary inertia, shear, and torque of the shaft. The gear mesh was modelled as a pair of rigid disks connected by a spring of time varying stiffness. The time varying mesh stiffness results in the abrupt change of the critical speeds of spur geared systems. As the bearing stiffness increases, critical speeds increase rapidly in case of stiff shafts, compared with flexible shafts.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 1997년도 춘계학술대회논문집; 경주코오롱호텔; 22-23 May 1997
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• pp.260-265
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• 1997

Large dynamic loads act on the rotor in rotary compressors. There are unbalance forces due to eccentric rotation parts and gas forces induced by the difference in pressure between compression and suction gases6 Rotor-journal bearing system is nonlinear since the stiffness and damping coefficients of the lubricating oil film are not constant in the bearings. In this paper, the program for predicting the behaviors of rotor-journal bearing system of rotary compressor is developed. Finite element modeling is used to analyze the flexible rotor. The numerical results are compared with experimental results. The location of balancer weight are suggested for reducing rotor whiring displacement.

• 한국진공학회지
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• 제19권4호
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• pp.256-264
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• 2010

본 논문에서는 고진공용 터보분자펌프의 비접촉 고속회전을 위한 자기베어링 시스템의 디지털 제어시스템의 설계에 대하여 소개하였으며, 실례로 800 l/s급의 고진공 펌프에 대하여 축 유연모드의 후방향 위험속도를 넘는 최대 40,000 rpm까지의 회전실험 결과를 나타내었다. 제안된 제어시스템은 기본적으로 PID 기반의 직접궤환 제어기와 자이로스코픽 모멘트 효과를 제어하기 위한 교차궤환기, 유연모우드 감쇄를 위한 리드필터와 동기진동 저감을 위한 노치필터 등으로 구성되어 있으며, 이러한 제어기는 자기부상형 터보분자펌프 외에 고속 플라이휠과 같은 자기베어링에 적용될 수 있다.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1990년도 한국자동제어학술회의논문집(국제학술편); KOEX, Seoul; 26-27 Oct. 1990
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• pp.1178-1183
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• 1990

A digital signal processor(DSP) is applied to realizing a compensator of control system of active magnetic bearings, to restrict a resonance caused by the first-order bending vibration of a flexible rotor, and to run the rotor beyond the critical speed. A full-order observer is applied to the translatory rotor-motion with the first-order vibration mode. A PID control is used for the conical motion. The rotor used in the experiments is symmetric, and an electromagnet and a displacement sensor are set in collocation.

• 소음진동
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• 제3권3호
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• pp.279-283
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• 1993

A diagnostic method of anisotropy and asymmetry in rotor systems utilizing the two-sided directional spectra of the operating responses has been presented and tested with a laboratory flexible rotor-bearing system. The experimental results show that the directional spectra can be effectively used for the diagnosis of anisotropy and/or asymmetry in rotor systmes by the investigation of -1X and +2X components in the directional spectrum of unbalance and gravity responses.

• 한국유체기계학회 논문집
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• 제5권1호
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• pp.55-61
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• 2002

The feasibility of an oil-free, motor-driven, two-stage centrifugal compressor supported by air bump bearings is investigated. This centrifugal compressor is driven by a 75 kW motor at an operating speed of 39,000 RPM, and a pressure ratio of the compressor is set up to 4. The analysis is performed by using bearing equilibrium position, heaving stillness, Campbell diagram, unbalance response, and stability. It is demonstrated in this paper that air bump bearings can be adopted well to an oil-free, motor-driven, centrifugal compressor. Specially, Cu-coated bump bearings have enough damping force to reduce a synchronous unbalance for rigid modes of the two-stage compressor. Futhermore, this concept may be applied to the flexible rotor system such as high speed turbomachinery with a super critical speed.

• 동력기계공학회지
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• 제5권4호
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• pp.53-60
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• 2001

This paper considers a modeling for the MIMO magnetic bearing system. The rotor is flexible and has a complex shape. To obtain the nominal plant transfer functions, we perform a numerical analysis by using the finite element method(F.E.M.) for the rotor's dynamics, and make a nominal model by reducing the modes from the results. And, we have experimented on the frequency response by a closed-loop identification method, and compared it with the simulation's result on the closed-loop control system.

• 대한기계학회논문집
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• 제19권3호
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• pp.639-646
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• 1995

The objective of this study is to minimize the weight of a damped anisotropic roto-bearing system considering whirl natural frequency and stability. The system is modeled as an assemblage of rigid disks, flexible shafts and discrete bearings. The system design variables are the crosssectional areas of shaft elements and the properties of bearings. To analyze the system, the polynomial method which is derived by rearranging the calculations performed by a transfer matrix method is adopted. For the optimization, the optimization software IDOL (Integrated Design Optimization Library) which is based on the Augmented Lagrange Multiplier (ALM) method is employed. Also, an analytical design sensitivity analysis of the system is used for high accuracy and efficiency. To demonstrate the usefulness of the proposed optimal design program incorporating analysis, design sensitivity analysis, and optimization modules, a damped anisotropic rotor-bearing system is optimized to obtain 34$ weight reduction.

• Tribology and Lubricants
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• 제10권2호
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• pp.43-50
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• 1994

The hydrodynamic bearing is accepted in many rotating systems because it has a large load carrying capacity. But the anisotropic pressure distribution of the bearing can arise the unstable vibration phenomenon over a certain speed. The magnetic bearing is an active element so that the unstable phenomenon of the hydrodynamic bearing, which is induced by the anisotropic support pressure of the oil film, can be controlled if the control algorithm and the controller gains are chosen appropriately. In this study, we investigate the stabilization method of the hydrodynamic bearing system composing the hybrid bearing which is the single unit of hydrodynamic bearing and magnetic bearing. The load carrying conditions of the hybrid bearing is modelled by the sum of the stiffness and damping coefficients of the hydrodynamic and the magnetic bearings in each direction. The dynamics of the rotor is analyzed by the Finite Element Method and the stability limit is determined by the eigenvalues of the hybrid bearings and shaft system. The eigenvalue study of the system shows that the stability limit of the hybrid bearing is increased compared to that of the hydrodynamic bearing. A Small increment of the stiffness and damping coefficient of the hybrid bearings by the magnetic actuators can increase the stability limit of the system. In this paper we tried to show the design references of the hybrid bearings by using the nondimensional bearing parameters. The analysis results show the possibilities of the stability limit increment of the hydrodynamic bearing system by combining the magnetic bearing.