• 제목/요약/키워드: Self-sustained Oscillation

검색결과 13건 처리시간 0.03초

Stochastic Analysis of Self-sustained Oscillation Loop for a Resonant Accelerometer

  • Hyun, Chul;Lee, Jang-Gyu;Kang, Tae-Sam;Sung, Sang-Kyung
    • 제어로봇시스템학회:학술대회논문집
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    • 제어로봇시스템학회 2004년도 ICCAS
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    • pp.574-578
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    • 2004
  • In this paper, a nonlinear feedback system is analyzed for a surface micromachined resonant accelerometer. For this, a brief illustration of the plant dynamics is given. In the analysis, the periodic signal in the nonlinear feedback loop is obtained by the limit cycle point, which is best approximated via the describing function method. Considering the characteristic feature of plant dynamics, a simple phase shifted relay with finite slope is designed for the nonlinearity implementation. With a describing function for random plus sinusoidal input, we analyzed the effect of a white Gaussian noise on oscillation frequency. Finally, simulation and experimental result is given.

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날개 명음소음에 관한 이론 및 실험 연구 (Theoretical and Experimental Study on Airfoil Singing)

  • 안병권;김종현;최종수
    • 한국소음진동공학회:학술대회논문집
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    • 한국소음진동공학회 2009년도 춘계학술대회 논문집
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    • pp.476-476
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    • 2009
  • Periodic vortex separations generate periodic vertical forces acting on a trailing edge of an airfoil. When a natural frequency of the trailing edge of the airfoil is close to a vortex shedding frequency, an amplitude of the edge oscillation becomes maximal; it makes intensive noise called singing. Motion of the trailing edge may also feedback to the vortex shedding so that self-sustained oscillation appear, and a resonant frequency is locked in some interval of the speed of the incident flow. In this study, a theoretical model is proposed and applied for modeling an airfoil singing. Results are compared with experimental measurements which are carried out in an anechoic wind tunnel.

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날개 명음소음에 관한 이론 및 실험 연구 (Theoretical and Experimental Study on Airfoil Singing)

  • 안병권;이종현;이욱;최종수
    • 한국소음진동공학회논문집
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    • 제20권2호
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    • pp.115-121
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    • 2010
  • Periodic vortex separations generate periodic vertical forces acting on a trailing edge of an airfoil. When a natural frequency of the trailing edge of the airfoil is close to a vortex shedding frequency, an amplitude of the edge oscillation becomes maximal; it makes intensive noise called singing. Motion of the trailing edge may also feedback to the vortex shedding so that self-sustained oscillation appears, and a resonant frequency is locked in some interval of the speed of the incident flow. In this study, a theoretical model is proposed and applied for modeling an airfoil singing. Results are compared with experimental measurements which are carried out in an anechoic wind tunnel.

2차원 날개의 유체-구조 연성해석 (Fluid-Structure Interaction Analysis of Two-Dimensional Wings)

  • 안병권;이숙정;김지혜;김기섭
    • 대한조선학회논문집
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    • 제50권5호
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    • pp.343-348
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    • 2013
  • When a natural frequency of the trailing edge of a wing is close to a vortex shedding frequency, an amplitude of the edge oscillation becomes maximal; it makes intensive noise called singing. Motion of the trailing edge may also feedback to the vortex shedding so that self-sustained oscillation appears, and a resonant frequency is locked in some interval of the speed of the incident flow. In this study, we first evaluate main features of oscillating characteristics of the wing. Second we simulate fluid-structure interaction of the wing with a flap using a commercial code, ANSYS-CFX, and investigate lift characteristics in a frequency domain.

가우스 잡음을 고려한 비선형 펄스 변조 시스템의 안정도 분석 (Stability Analysis of Nonlinear Pulse-Modulated System Subject to Gaussian Noise)

  • 강영채
    • 대한전자공학회논문지
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    • 제19권6호
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    • pp.67-79
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    • 1982
  • 가우스 잡음의 출현시 PWM 시스템의 안정도가 연구되었다. 일반 시스템은 종래의 서술 함수 방법을 이용할 때 비선형 소자와 선형 소자로 나누어진다. 등가 어드미턴스 개념이 이 시스템의 비선형 소자의 전달 특성을 구하는데 사용되었다. 이 논문에서는 가우스 잡음만이 존재하는 경우 자기 발진 조건이 유도되었고 그 결과를 컴퓨터 시뮬레이션으로 분석하였다. The stability of general pulse-width modulation system with Gaussian random disturbance was discussed . General system is divided into nonlinear and linear elements using the conventional describing function method. The concept of the equivalent admittance was used to find the transfer characteristic of the nonlinear element of the system. In this paper the self-sustained oscillation condition in the autonomous system was derived and the results was analyzed with computer simulation.

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3차원 교차 주름판 내 유동의 불안정성 및 자활 진동 (Instability and Self-Sustained Oscillation of the Flow between Three-Dimensionally Cross-corrugated Plates)

  • 이승엽;최영돈
    • 대한기계학회:학술대회논문집
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    • 대한기계학회 2002년도 학술대회지
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    • pp.679-682
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    • 2002
  • Energy dissipations in a general PHE flow are the compounded effects of the piled corrugate geometries and its wall pressure and temperature distributions. In addition, although the exchangers are substantial pieces of engineering equipment, they are composed of a very large number of nominally identical and small geometrical elements. In the present numerical study, the three-dimensionally complicated energy dissipation fields and those wall-shape-induced flow destabilization are investigated in the cross-corrugated passages, which result in high energy transports with comparatively low pressure drop. We revealed the critical conditions as $Re=157.3 for the wall-shape-induced flow destabilization in a general PHE element by initial value method, or shooting method, and compare its value to that of analytical solution of plane Poiseille flow, two-dimensional grooved flow and so on. We also observed the detailed variation of flow field and energy transportation with changes in time and flow variables such as Reynolds number. Lastly, we considered the flow natural frequency, or Strouhal number, with variation of hydrodynamic conditions for the best use of active control, such as forced mass flow rate pulsative flow, to enhance energy transportation.

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모따기된 전향계단에 부딪치는 와류에 의한 비정상 벽면압력 변동 (Unsteady Wall Pressure Fluctuation Generated from the Impinging Vortex on the Chamfered Forward Step)

  • 유기완;이준신
    • 대한기계학회:학술대회논문집
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    • 대한기계학회 2001년도 추계학술대회논문집B
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    • pp.312-317
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    • 2001
  • Modifying effects of the rectangular forward step for suppressing the unsteady pressure fluctuation during interaction between the upstream vortical flow with the edge are studied numerically. The vortical flow is modeled by a point vortex, and the unsteady pressure coefficient is obtained from the velocity and the potential field. To investigate the effects of the edge shape the rectangular forward step is chamfered with various angles. Calculation show that the pressure peaks become decreased by increasing the vortex height as well as the chamfering angle. The pressure amplitudes are very sensitive to the change of the initial vortex height. From this study we can find out that the chamfered edge has two effects; the one is that it suppresses the pressure amplitude generated from the edge, and the other is that it decreases the time variation of unsteady pressure fluctuation. These modifying concepts can be applied to attenuate the self-sustained oscillation mechanism at the open cavity flow.

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와류와 전향계단의 상호작용에 의한 비정상 벽면압력 변동의 수치해석 (Numerical Analysis of the Unsteady Pressure fluctuation Generated from the Interaction between a Vortex Flow with a Forward Step)

  • 유기완;이준신
    • 한국소음진동공학회논문집
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    • 제12권3호
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    • pp.213-220
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    • 2002
  • Modifying effects of the rectangular forward step for suppressing the unsteady pressure fluctuation during interaction between the upstream vortical flow and the edge are studied numerically. The vertical flow is modeled by a point vortex, and the unsteady pressure coefficient is obtained from the velocity and the potential fields. To investigate the effects of the edge shape the rectangular forward step is chamfered wish various angles. Calculation shows that the pressure peaks become decreased by increasing the vortex height as well as the chamfering angle. The pressure amplitudes are very sensitive to the change of the initial vertex height and its strength. From this study we can find out that the chamfered edge has two effects; the one is that it suppresses the pressure amplitude generated from the edge, and the other is that it decreases the time variation of unsteady pressure fluctuation. These modifying concepts can be applied to attenuate the self-sustained oscillation mechanism at the open cavity flow.

자동이득 제어루프를 이용한 진폭제어방식의 공진형 가속도계 설계 (Oscillation Amplitude-controlled Resonant Accelerometer Design using Aautomatic Gain Control Loop)

  • 윤석창;성상경;이영재;강태삼
    • 한국항공우주학회지
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    • 제36권7호
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    • pp.674-679
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    • 2008
  • 본 논문에서는 안정된 진동을 얻기 위한 자동 이득 제어(AGC) 루프를 이용하여 자가 유지 특성을 갖는 공진형 가속도계를 설계하였다. 제안된 가속도계의 기본 원리는 가속도 입력시, 가변 진동의 진폭을 일정하게 유지시키는 방법을 이용한다. 시스템 모델링과 진동의 포락선을 고려한 루프 설계 및 변환를 통하여 다양한 가속도 입력 하에서 진동 신호의 진폭을 일정하게 유지하도록 제어기를 설계하였고, 시뮬레이션 결과를 통해 실현가능성을 확인하였다. 따라서 고안된 공진 가속도계는 산업과 민간 응용 분야에 있어서 제어용 등급의 관성 측정 시스템에 적용될 수 있을 것으로 기대한다.

Development of a Micromachined Differential Type Resonant Accelerometer and Its Performance

  • Hyun, Chul;Lee, Jang-Gyu;Kang, Tae-Sam;Sung, Sang-Kyung;Seok, Seon-Ho;Chun, Kuk-Jin
    • 제어로봇시스템학회:학술대회논문집
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    • 제어로봇시스템학회 2003년도 ICCAS
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    • pp.2182-2186
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    • 2003
  • This paper presents the differential type resonant accelerometer (DRXL) and its performance test results. The DRXL is the INS grade, surface micro-machined sensor. The proposed DRXL device produces a differential digital output upon an applied acceleration, and the principle is a gap-dependent electrical stiffness variation of the electrostatic resonator with torsion beam structures. Using this new operating concept, we designed, fabricated and tested the proposed device. The final device was fabricated by using the wafer level vacuum packaging process. To test the performance of the DRXL, a nonlinear self-oscillation loop is designed using describing function technique. The oscillation loop is implemented using discrete electronic elements. The performance test of the DRXL shows that the sensitivity of the accelerometer is 12 Hz/g and its long term bias stability is about $2mg(1{\sigma})$. The turn on repeatability, bandwidth, and dynamic range are 4.38 mg, 100 Hz, and ${\pm}\;70g$, respectively.

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