• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2003년도 추계학술대회논문집
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• pp.643-648
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• 2003

The problem considered in this paper is that the tip position of a flexible cantilever beam is controlled to follow a command signal, using a pair of piezoelectric actuators at the clamped end. The beam is lightly damped and so the natural transient response is rather long, and also since the sensor and actuator are not collocated, the plant response is non-minimum phase. Two control strategies were investigated. The first involved conventional PID control in which the feedback gains were adjusted to give the fastest closed-loop response to a step input. The second control strategy was based on an internal model control (IMC) architecture. The control filter in the IMC controller was a digital FIR device designed to minimize the expectation of the mean square tracking error. The IMC controller designed fur the beam was found to have very much reduced settling times to a step input compared with those of the PID controller.

• 한국산업융합학회 논문집
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• 제18권4호
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• pp.216-223
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• 2015

Recently Manipulation capability is important for a robot. Interaction between a robot hand and objects can be properly controlled only is suitable sensors are available. Recently the tendency is to create robot hands more compact and high integrated sensors system, in order to increase the grasping capability and in order to reduce cabling through the finger, the palm and the arm. As a matter of fact, miniaturization and cabling harness represents a significant limitation to the design of small sized embedded sensor. Ongoing work is focusing on a flexible manipulation system, which consists of a dual flexible multi-fingered hand-arm system, and a dual active vision system.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2011년도 제40회 동계학술대회 초록집
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• pp.500-500
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• 2011

With recent advances in flexible and stretchable electronics, the development of physically responsive field-effect transistors (physi-FETs) that are easily integrated with transformable substrates may enable the omnipresence of physical sensing devices in electronic gadgets. However, physical stimuli typically induce whole sensing physi-FET devices under global influences that also cause changes in the parameters of FET transducers, such as channel mobility and dielectric capacitance that prevent proper interpretations of response in sensing materials. Extended-gate structures with isolated stimuli have been used recently in physi-FETs to demonstrate performances of sensing materials only. However, such approaches are limited to prototype researches since isolated stimuli rarely occur in real-life applications. In this report, we theoretically and experimentally demonstrated that integrating piezoelectric nanocomposites directly into flexible organic FETs (OFETs) as gate dielectrics provides a general research direction to physi-FETs with a simple device structure and the capability of precisely investigating functional materials. Measurements with static stimulations, which cannot be performed in conventional systems, exhibited giant-positive d33 values of nanocomposites of barium titanate (BT) NPs and poly (vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)).

• Structural Engineering and Mechanics
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• 제55권1호
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• pp.229-244
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• 2015

H-infinity norm relates to the maximum in the frequency response function and H-infinity control method focuses on the case that the vibration is excited at the fundamental frequency, while 2-norm relates to the output energy of systems with the input of pulses or white noises and 2-norm control method weighs the overall vibration performance of systems. The trade-off between the performance in frequency-domain and that in time-domain may be achieved by integrating two indices in the mixed vibration control method. Based on the linear fractional state space representation in the modal space for a piezoelectric flexible structure with uncertain modal parameters and un-modeled residual high-frequency modes, a mixed dynamic output feedback control design method is proposed to suppress the structural vibration. Using the linear matrix inequality (LMI) technique, the initial populations are generated by the designing of robust control laws with different H-infinity performance indices before the robust 2-norm performance index of the closed-loop system is included in the fitness function of optimization. A flexible beam structure with a piezoelectric sensor and a piezoelectric actuator are used as the subject for numerical studies. Compared with the velocity feedback control method, the numerical simulation results show the effectiveness of the proposed method.

• 센서학회지
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• 제22권6호
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• pp.400-403
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• 2013

The piezoelectric composite film of ferroelectric PZT ceramic ($PbZr_xTi_{1-x}O_3$) and polymer (PDMS, Polydimethylsiloxane) was prepared to improve the flexibility of piezoelectric material. The bar coating method was applied to fabricate flexible nanocomposite film with large surface area by low cost process. In the case of using metal electrode on the composite film, although there is no problem by bending process, the electrode is usually broken away from the film by stretching process. However, the well-attached, flexible CNT electrode on PZT/PDMS film improved flexibility, especially stretchability. PZT particles was usually settled down into polymer matrix due to gravity of the weighty particle, so to improve the dispersion of PZT powder in polymer matrix, small amount of additives (CNT powder, Carbon nanotube powder) was physically mixed with the matrix. By stretching the film, an output voltage of PZT(70 wt%)/PDMS with CNT (0.5 wt%) was measured.

• 한국구조물진단유지관리공학회 논문집
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• 제16권2호
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• pp.1-9
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• 2012

철근콘크리트 구조물은 사용연한과 지진 등의 영향으로 균열손상이 주요부재에서 발생되며, 이러한 손상을 보수하기 위해 많은 시간과 노력이 낭비되고 있다. 따라서, 본 연구에서는 소형 리드스위치 센서를 휨시험체 내외부에 매입하거나 부착하여 외력에 의한 균열손상을 스스로 나타내는 스마트 부재에 대하여 연구하였다. 균열손상을 모니터링하기 위해 RF시스템을 리드 스위치센서와 이용하였다. 휨시험체 중앙에 하중이 재하되면 매입되거나 부착된 리드 스위치센서가 파괴되고, 이와 연결된 RF시스템은 손상정보를 전달한다. 본 연구는 무선주파수를 응용한 건축부재의 손상자현 시스템에 대한 기초적 연구이다.

• 한국정밀공학회지
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• 제14권1호
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• pp.174-184
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• 1997

This paper presents a robust force tracking control of a smart flexible gripper featured by a piezoceramic actuator characterizing its durability and quick response time. A mathematical governing equation for the proposed gripper structure is derived by employing Hamilton's principle and a state space control model is subsequently obtained through model analysis. Uncertain system parameters such as frequency variation are included in the control model. A sliding mode control theory which has inherent robustness to the sys- tem uncertainties is adopted to design a force tracking controller for the piezoceramic actuator. Using out- put information from the tip force sensor, a full-order observer is constructed to estimate state variables of the system. Force tracking performances for desired trajectories represented by sinusoidal and step func- tions are evaluated by undertaking both simulation and experimental works. In addition, in order to illustrate practical feasibility of the proposed method, a two-fingered gripper is constructed and its performance is demonstrated by showing a capability of holding an object.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
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• pp.413-413
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• 2014

In this paper, we present a fabrication method of functionalized gold nanostructures on flexible substrate that can be implemented for plasmonic sensing application. For biomolecular sensing, many researchers exploit unconventional lithography method like nanoimprint lithography (NIP), contact transfer lithography, soft lithography, colloidal transfer printing due to its usability and easy to functionalization. In particular, nanoimprint and contact transfer lithography need to have anti-adhesion layer for distinctive metallic properties on the flexible substrates. However, when metallic thin film was deposited on the anti-adhesion layer coated substrates, we discover much aggravation of the mold by repetitive use. Thus it would be impossible to get a high quality of metal nanostructure on the transferred substrate for developing flexible electronics based transfer printing. Here we demonstrate a method for nano-pillar mold and transfer the controllable nanoparticle array on the flexible substrates without an anti-adhesion layer. Also functionalization of gold was investigated by the different length of thiol applied for effectively localized surface plasmonic resonance sensing. First, a focused ion beam (FIB) and ICP-RIE are used to fabricate the nanoscale pillar array. Then gold metal layer is deposited onto the patterned nanostructure. The metallic 130 nm and 250 nm nanodisk pattern are transferred onto flexible polymer substrate by bi-layer functionalized contact imprinting which can be tunable surface energy interfaces. Different thiol reagents such as Thioglycolic acid (98%), 3-Mercaptopropionic acid (99%), 11-Mercaptoundecanoic acid (95%) and 16-Mercaptohexadecanoic acid (90%) are used. Overcoming the repeatedly usage of the anti-adhesion layer mold which has less uniformity and not washable interface, contact printing method using bi-layer gold array are not only expedient access to fabrication but also have distinctive properties including anti-adhesion layer free, functionalized bottom of the gold nano disk, repeatedly replicate the pattern on the flexible substrate. As a result we demonstrate the feasibility of flexible plasmonic sensing interface and anticipate that the method can be extended to variable application including the portable bio sensor via mass production of stable nanostructure array and other nanophotonic application.

• 한국정보처리학회논문지
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• 제7권12호
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• pp.3848-3854
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• 2000

제어 시스템에서 요구되는 특성과 제공되는 하드웨어들의 기능을 유지하는 것은 만족할만한 제어기를 설계하는데 있어서 중요하다. 제어시스템의 하드웨어들 중에서 센서는 내·외부 외란에 가장 취약하지만, 정확하고 신뢰성있는 센서값을 유지하는 것은 좋은 제어기 성능을 위해 꼭 필요하다. 센서에 오류가 발생했을 경우, 센서 출려과 제어기 출력 같은 값을 사용하여 이를 검출하고, 오류 증상을 분석하여 오류 요인을 판단한다. 오류 요인에 따라 원래 센서값 대신 Self-Validating 센서값을 사용한다. 본 논문에서는 유연 링크 시스템에서 광센서 모듈의 오류 문제들에 Self-Validating 센서를 응용하여 이의 유효성을 보이고, 센서 오류가 발생하였을 때 만족할만한 성능을 제공할 수 있는 디지털 제어기를 제안한다.

• 한국지반공학회논문집
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• 제34권9호
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• pp.19-32
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• 2018

본 연구에서는 무선센서네트워크기술(Wireless Sensor Network, WSN)의 산사태 모니터링 적용성을 연구하였다. WSN시스템은 IEEE 802.14e 표준규격을 사용하는 데이터의 수집과 전달을 위한 센서노드와 데이터를 수집 처리하고 최종 서버로 전송하는 게이트웨이로 구성하였다. 센서네트워크의 토폴로지는 유연성과 신뢰성이 높은 메쉬형을 채택하였으며, 서울시의 총 3개소에 테스트베드를 구축하였다. 산사태를 모니터링 하기 위하여 각 센서노드에는 함수비계, 모관흡수력계, 경사계, 강우량계를 설치하였다. 센서노드의 배치를 위해 산사태 위험도 해석, 임목밀도 및 지형분석을 통한 통신범위 분석을 수행하였다. 측정된 계측 데이터를 분석한 결과 네트워크의 연결은 양호하게 나타났으며, 강우에 의한 지반의 반응이 실내에서 측정한 함수비-모관흡수력과 유사한 결과를 나타났다. 따라서, 테스트베드 사례를 통해 산사태 모니터링에 적용이 가능함을 확인하였다.