• 한국생산제조학회지
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• 제19권3호
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• pp.419-425
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• 2010

To machine the micro hole, laser machining system is widely used, however, the system cannot fabricate the micro hole with high aspect ratio and good surface finish. To break the obstacles, the high frequency vibration mechanism with PZT (Piezoelectric Transducers) is proposed in this paper. The mechanism will vibrate the laser beam in vertical direction so that the aspect ratio and surface finish may be higher than the conventional. The mechanism vibrates the eyepiece of laser optics. In addition to the benefits, the mechanism enables us to have high precision and flexibility. It decreases burr and debris during machining. And it is able to machine various materials of workpiece. This research include high frequency and large travel range of the proposed mechanism. The PZT motion of mechanism and analysis on the sensitivity of design parameters are extracted from a finite element method (FEM) simulation. In the analysis, the target vibration mode without parasitic motion is designated to have the target frequency and high amplitude.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제54권10호
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• pp.433-437
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• 2005

This paper studied Rotary type ultrasonic motor which has cross type stator. The stator consists of hollowed cross type metal which has four piezoelectric ceramics on the ends of cross bars. When two harmonic voltages which have 90$^{\circ}$ phase difference given to ceramics, the elliptical motion was generated in the inside tips. Inside tips are contact with rotor and these elliptical motions are rotate the rotor The finite element analysis was used to optimize the dimension and displacement of the stator. And the analyzed results were compared with the experimental results of the motor. As results, the speed and the torque of motor was increased by increasing width of the cross bar. And the speed and torque o( motor was not influenced to length of cross bar. The speed and torque was linearly increased by increasing voltage. The maximum torque was generated when the motor fabricated length of cross bar and width of ceramics in the ratio of 1:2.

• 한국정밀공학회지
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• 제15권11호
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• pp.172-179
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• 1998

This paper proposes an identification method for modes of a thin plate where multiple actuators and sensors are bonded. When a natural frequency of a mode is decoupled from all other natural frequencies, the mode can be identified separatedly with a bandpass filter. Since a thin plate has resonant peaks at natural frequencies, the bandpass filter can be designed to extract the signal of the mode to be identified. Parameters of the second order linear differential equation of the mode can be obtained to apply the Least square method to the extract the modal signal. The proposed identification method is applied to an all-clamped plate with two pairs of piezoelectric actuators and sensors. The outputs of the identified model match with the experimental data well.

• 한국소음진동공학회논문집
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• 제26권3호
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• pp.270-280
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• 2016

노치가 있는 보에 부착된 압전소자의 전기역학적 어드미턴스 전이과정을 파전달 관점에서 규명한다. 유한요소 해석을 통해 노치가 있는 보에서 잔향하는 램파에 대한 수치해를 구한다. 보에 병치된 압전소자의 분극을 이용하여 노치에 의해 발생하는 모드변환된 램파 신호를 추출한다. 전기역학적 어드미턴스의 전이과정을 보여줄 수 있는 일련의 템포럴 스펙트럼은 모드변환된 램파 신호들을 시간영역에서 순차적으로 절단한 후, 고속 푸리에 변환을 적용하여 계산한다. 절단 시간이 상대적으로 작을 때 이에 대응되는 템포럴 스펙트럼은 입력 주파수 대역의 특성이 지배적이다. 그러나, 절단 시간이 증가함에 따라 입력 주파수 대역 내에 존재하는 보의 모달 특성이 템포럴 스펙트럼에 중대한 영향을 준다. 이는 보에서 잔향하는 모드변환램파가 보의 공진에 기여함을 의미한다. 각 공진주파수 부근에서 템포럴 스펙트럼에 대한 제곱평균제곱근을 계산한다. 모든 공진주파수 부근에서 절단시간에 따라 제곱평균제곱근은 증가한다. 마지막으로, 보의 손상 진단 측면에서 수치해석 결과의 시사점에 대해 논의한다.

• 유변학
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• 제3권2호
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• pp.156-165
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• 1991

폴리비닐리덴플루오라이드 바이모프 외팔보(poly(vinylidene fluoride) bimorph cantilever beam)의 진동을 기술하는 수학적 모형을 세우고 실험으로 그모형의 타당성을 고 찰하였다. 여러 전압의 교류전류에 대해 여러 길이의 외팔보의 주파수응답을 측정하였고 여 러 전압의 직류전류에 대해 여러 길이의 외팔보의 처짐을 측정하였다. 실험으로부터 이 외 팔보의 진동은 점성감쇠보다는 구조감쇠로 기술하는 것이 더 타덩하고 외팔보가 전기장에 대해 damping factor가 일정해야 하나 각각의 normal mode에 대해 다른 damping factor로 수정하여 계산한이론치가 실험과 더 일치하였다. 공명주파수의 공명진폭을 예측할수 있고 넓은 입력주파수 영역에 대한 외팔보의 응답을 기술 할수 있으며 진동하는 외팔보는 모든위 치에서의 진폭을 기술할수 있다는 점에서 여기서의 모형은 Toda와 Smits의 모형들보다 우 수하다고 볼수 있다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2006년도 춘계학술대회논문집
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• pp.650-655
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• 2006

Dynamic modeling and active vibration control of smart hull structure using Macro Fiber Composite (MFC) actuator is conducted. Finite element modeling is used to obtain equations of motion and boundary effects of smart hull structure. Modal analysis is carried out to investigate the dynamic characteristics of the smart hull structure, and compared to the results of experimental investigation. Negative velocity feedback control algorithm is employed to investigate active damping of hull structure. It is observed that non-resonant vibration of hull structure is suppressed effectively by the MFC actuators.

• 한국소음진동공학회논문집
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• 제16권8호
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• pp.840-847
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• 2006

Dynamic modelingand active vibration control of smart hull structure using Macro Fiber Composite (MFC) actuators are conducted. Finite element modeling is used to obtain equations of motion and boundary effects of smart hull structure. Modal analysis is carried out to investigate the dynamic characteristics of the smart hull structure, and compared to the results of experimental investigation. Negative velocity feedback control algorithm is employed to investigate active damping of hull structure. It is observed that non-resonant vibration of hull structure is suppressed effectively by the MFC actuators.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2008년도 추계학술대회논문집
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• pp.237-242
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• 2008

This paper presents vibration control of an active hybrid engine mount featuring magneto-rheological (MR) fluid and a piezostack actuator. On the basis of the conventional passive rubber mount, MR fluid is adopted to improve isolation performance at resonant frequencies, whereas the piezostack actuator is adopted for performance improvement at non-resonant frequencies, especially at high frequencies. Based on some particular practical requirements of engine mounts, the proposed mount is designed and manufactured. The characteristics of rubber element, piezostack actuator and MR fluid are verified for system analysis and controller synthesis. The model of the proposed mount with a supported mass (engine) is established. In this work, a sliding mode controller is synthesized for the mount system to reduce vibrations transmitted from the engine in a wide frequency range. Computer simulations are performed to evaluate the performances of the proposed active engine mount in time and frequency domains.

• 한국소음진동공학회논문집
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• 제18권11호
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• pp.1150-1156
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• 2008

This paper presents vibration control of an active hybrid engine mount featuring a magneto-rheological(MR) fluid and a piezostack actuator. The MR fluid is adopted to improve isolation performance at resonant frequencies, while the piezostack actuator is adopted for performance improvement at non-resonant frequencies, especially at high frequencies. Based on some particular practical requirements of engine mounts, the proposed mount is designed and manufactured. The characteristics of rubber element, piezostack actuator and MR fluid are verified for system analysis and controller synthesis. The dynamic model of the proposed mount with a supported mass (engine) is established. In this work, a sliding mode controller is synthesized for the mount system to reduce vibrations transmitted from the engine in a wide frequency range. Computer simulations are performed to evaluate control performances of the proposed active engine mount in time and frequency domains.

• 센서학회지
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• 제11권3호
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• pp.132-137
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• 2002

본 연구에서는 온도에 따른 압전특성이 매우 안정적인 $LiTaO_3$ ($x-112^{\circ}$ y) 단결정을 이용하여 압전변압기를 제작하고 그 특성을 분석하였다. 제작시 $LiTaO_3$ 단결정의 변환효율이 낮은 단점을 보완하기 위해 Lame'-mode를 이용하여 길이와 폭의 비가 2:1인 압전변압기를 제작하고 PSpice를 이용하여 진동 모드 해석, 입력전압에 따른 출력전압특성 및 진동속도특성을 분석하였다. 제작한 압전변압기는 길이방향의 제 2차 고조파 주파수와 폭방향의 기본공진주파수가 결합된 290.83[kHz]에서 입력전압에 대한 최대출력전압이 나타났으며, 약 10배 정도의 승압비를 얻을 수 있었다.