• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 하계학술대회 논문집 D
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• pp.2123-2125
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• 2002

This paper presents the use of piezoelectric ceramics for sensing and actuation purposes for vibration control. The PZT sensors and actuators are designed and fabricated. The transfer function of the beam is obtained via the Lagrangian method.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2002년도 봄 학술발표회 논문집
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• pp.453-460
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• 2002

Piezoelectric solids such as PZT and PLZT have been widely used as sensors or actuators for various smart structural systems. The main problem occurring in the applications is that a larger and larger actuation force is required to maximize the function of the system. This naturally leads to local concentrations of electric or stress fields near crack tips or geometric irregularities and thereby results in a nonlinear behavior of the system Hence, it becomes more important to Predict the nonlinear behavior of piezoelectric solids In this Paper we investigate the micro-mechanism of nonlinear behavior in piezoelectric materials and propose constitutive equations. The calculation results obtained from an associated finite element Program are shown to be qualitatively consistent with experiments.

• 대한기계학회논문집A
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• 제30권9호
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• pp.1102-1109
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• 2006

In this paper, the polarization of piezoelectric materials is considered to improve actuation since the piezoelectric polarization has influences on the performance of the actuator. The topology design of compliant mechanism can be formulated as an optimization problem of material distribution in a fixed design domain and continuous approximation of material distribution (CAMD) method has demonstrated its effectiveness to prevent the numerical instabilities in topology optimization. The optimization problem is formulated to maximize the mean transduction ratio subject to the total volume constraints and solved using a sequential linear programming algorithm. The effect of CAMD and the performance improvement of actuator are confirmed through Moonie actuator and PZT suspension design.

• 대한기계학회논문집A
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• 제25권10호
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• pp.1514-1519
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• 2001

This paper is concerned with design, manufacturing and performance test of LIPCA ( Lightweight Piezo- composite Curved Actuator) using a top carbon fiber composite layer with near -zero CTE(coefficient of thermal expansion), a middle PZT ceramic wafer and a bottom glass/epoxy layer with high CTE. The main point of this design is to replace the heavy metal layers of THUNDER by thigh tweight fiber reinforced plastic layers without losing capabilities to generate high force and large displacement. It is possible to save weight up to about 30% if we replace the metallic backing material by the light fiber composite layer. We can also have design flexibility by selecting the fiber direction and the size of prepreg layers. In addition to the lightweight advantage and design flexibility, the proposed device can be manufactured without adhesive layers when we use epoxy resin prepreg system. Glass/epoxy prepregs, a ceramic wafer with electrode surfaces, and a graphite/epoxy prepreg were simply stacked and cured at an elevated temperature (177 $^{circ}C$ after following an autoclave bagging process. It was found that the manufactured composite laminate device had a sufficient curvature after detached from a flat mold. The analysis method of the cure curvature of LIPCA using the classical lamination theory is presented. The predicted curvatures are fairly in agreement with the experimental ones. In order to investigate the merits of LIPCA, a performance test of both LIPCA and THUNDE$^{TM}$ were conducted under the same boundary conditions. From the experimental actuation tests, it was observed that the developed actuator could generate larger actuation displacement than THUNDERT$^{TM}$.

• 한국정밀공학회지
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• 제22권9호
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• pp.130-136
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• 2005

This paper presents an optimal design and the performance evaluation of two-axis nano positioning stage with round notched flexure hinges. A flexure hinge mechanism with round notched flexure hinges is to guide the linear motions of a moving plate in the nano positioning stage. A Min-Max algorithm is applied to the design of the flexure hinge mechanism for nano positioning stage. In the design process, the structure of the flexure hinge mechanism is fixed, then the radius of a round hole and the width of two round holes are chosen as design variables, and finally the do sign variables are calculated by the Min-Max algorithm. The machined flexure hinge mechanism, stack type PZTs for actuation and capacitance type displacement sensors for position measurement are assembled into the nano positioning stage. The experimental results of the manufactured nano positioning stage show the first modal resonance frequency of 197 Hz, the operating range of 40 um, and the resolution of 3 nm.

• 한국정밀공학회지
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• 제23권6호
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• pp.166-173
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• 2006

In this study, a probe array has been developed for use in a data storage device that is based on scanning probe microscope (SPM) and MEMS technology. When recording data bits by poling the PZT thin layer and reading them by sensing its piezoresponse, commercial probes of which the tip heights are typically shorter than $3{\mu}m$ raise a problem due to the electrostatic forces occurring between the probe body and the bottom electrode of a medium. In order to reduce this undesirable effect, a poly-silicon probe with a high aspect-ratio tip was fabricated using a molding technique. Poly-silicon probes fabricated by the molding technique have several features. The tip can be protected during the subsequent fabrication processes and have a high aspect ratio. The tip radius can be as small as 15 nm because sharpening oxidation process is allowed. To drive the probe, electrostatic actuation mechanism was employed since the fabrication process and driving/sensing circuit is very simple. The natural frequency and DC sensitivity of a fabricated probe were measured to be 18.75 kHz and 16.7 nm/V, respectively. The step response characteristic was investigated as well. Overshoot behavior in the probe movement was hardly observed because of large squeeze film air damping forces. Therefore, the probe fabricated in this study is considered to be very useful in probe-based data storages since it can stably approach toward the medium and be more robust against external shock.

• 한국항공우주학회지
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• 제30권5호
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• pp.94-100
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• 2002

본 논문은 곡면형 압전 복합재료 작동기 LIPCA의 개발 및 성능 실험에 관한 것이다. LIPCA는 압전 세라믹을 중심으로 상층부는 탄성계수가 크면서 열팽창계수가 낮은 섬유강화 복합재료층이 위치하며, 하층부는 탄성계수가 작으면서 열팽창계수가 큰 섬유강화 복합재료층이 위치한다. 작동기의 성능 검증을 위해 작동지그 및 전압 공급 장치 그리고 비접촉 레이저 센서로 이루어진 실험 시스템을 구성하였다. 성능 실험은 양단 단순지지상태에서 압전 재료의 전극에 $100\sim400V_{pp}$의 교류 전압을 1Hz로 가하였을 경우 작동기 중앙부에서 발생하는 수직방향의 변위를 측정하는 것으로 수행하였다. LIPCA와 THUNDER의 성능 검증 결과 LIPCA-C2는 THUNDER에 비해 34% 경량화 되었으며, 작동변위는 13% 향상되었다.

• Journal of Electrical Engineering and Technology
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• 제5권2호
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• pp.337-341
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• 2010

In this paper, an extremely low voltage operated micro corner cube retroreflector (CCR) was fabricated for free-space optical communication applications by using bulk silicon micromachining technologies. The CCR was comprised of an orthogonal vertical mirror and a horizontal actuated mirror. For low voltage operation, the horizontal actuated mirror was designed with two PZT cantilever actuators, torsional bars, hinges, and a mirror plate with a size of $400{\mu}m{\times}400{\mu}m$. In particular, the torsional bars and hinges were carefully simulated and designed to secure the flatness of the mirror plate by using a finite element method (FEM) simulator. The measured tilting angle was approximately $2^{\circ}$ at the applied voltage of 5 V. An orthogonal vertical mirror with an extremely smooth surface texture was fabricated using KOH wet etching and a double-SOI (silicon-on-insulator) wafer with a (110) silicon wafer. The fabricated orthogonal vertical mirror was comprised of four pairs of two mutually orthogonal flat mirrors with $400{\mu}m4 (length) $\times400{\mu}m$ (height) $\times30{\mu}m$ (thickness). The cross angles and surface roughness of the orthogonal vertical mirror were orthogonal, almost $90^{\circ}$ and 3.523 nm rms, respectively. The proposed CCR was completed by combining the orthogonal vertical and horizontal actuated mirrors. Data transmission and modulation at a frequency of 10 Hz was successfully demonstrated using the fabricated CCR at a distance of approximately 50 cm.

• 한국구조물진단유지관리공학회 논문집
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• 제18권1호
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• pp.166-173
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• 2014

본 연구에서는 레이저 가진을 이용한 초음파 전파 영상 기반 배관 비파괴 검사에 관해 다룬다. 손상의 영상화를 위해 갈바노미터 기반 레이저 미러 스캐너와 Q-Switch Nd: YAG 레이저 시스템을 사용하였다. 레이저 시스템을 가진원으로 사용하면 빠른 속도로 비접촉 초음파 가진이 가능하며, 온도의 변화가 급격한 환경이나 유해 물질이 포함된 환경에서도 대상 구조물의 원거리 가진이 가능하다. 또한 공간 해상도가 높으며, 입사각이 넓어 표면 형상이 복잡한 대상 구조물도 가진이 가능하다. 본 연구에서는 이러한 레이저 시스템으로부터 생성된 유도 초음파를 단일 PZT 센서를 사용하여 계측하고, 계측된 신호는 레이저 가진점에 해당하는 좌표점에 나열함으로써 2차원 공간좌표 및 시간축을 더한 초음파 전파 영상 생성을 위한 3차원 데이터를 구성한다. 이 데이터를 시간 축에 따라 연속적으로 반복 재생하면 초음파 전파 영상을 구할 수 있다. 이 때 웨이블릿 변환을 이용하여 계측 신호의 특정 주파수 성분을 추출해냄으로써 관찰하고자 하는 특정 유도 초음파 모드를 추출할 수 있다. 이러한 일련의 과정으로부터 획득한 초음파 전파 영상 데이터를 시간-공간 영역에서 주파수-wavenumber 영역으로 변환시켜줌으로써 손상 특성을 추출할 수 있다. 본 연구에서는 손상의 진단 및 위치 추정을 위해 wavenumber 필터링 기술을 적용하였으며, 시스템 검증을 위해 다양한 배관구조물 Testbed를 대상으로 실험을 수행하였다.