• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집B
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• pp.497-501
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• 2000

Flow over a sphere is controlled experimentally at $Re=10^5$ using electro-magnetic actuators. The electro-magnetic actuator developed in this study is composed of the permanent magnet electro-magnet membrane and slot. Eight actuators are placed inside the sphere at equally spaced intervals on a latitudinal plane and the position of the control slot is 76 from the stagnation point. Each actuator generates a periodic blowing and suction through the slot at variable frequencies of $10{\sim}140Hz$ and variable amplitudes by controlling electric signals applied to the electro-magnet. Drag on the sphere measured using a load cell is significantly reduced with control at the forcing frequencies larger than the natural shedding frequency $({\approx}14Hz\;at\;Re=10^5)$, whereas drag is slightly increased at the forcing frequency of 10Hz. It is shown from pressure measurement that the static pressure in the rear surface of the sphere is significantly increased with control, indicating that the separation is delayed due to control. Flow visualizations also show that the detaching shear layer is more attracted to the sphere center with control, the separation bubble size is significantly reduced, and motion inside the bubble is very weak, as compared to the case of uncontrolled flow.

• 한국자기학회지
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• 제19권6호
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• pp.222-226
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• 2009

기존의 평판형 전자기 엑츄에이터에 쇼티드 턴을 적용한 새로운 형태의 평판형 전자기 엑츄에이터를 제안하였다. 기존의 평판형 전자기 엑츄에이터에서 발생하는 인덕턴스에 의한 초기응답 지연현상을 줄이기 위해 본 논문에서는 기존의 엑츄에이터의 요크와 요크 사이에 중간요크(center yoke)를 추가하고, 쇼티드 턴을 적용한 새로운 형태의 평판형 전자기 엑츄에이터를 제안 하고, 상용 자기장 해석 프로그램인 MAXWELL을 이용한 시뮬레이션을 통해 동적 성능 향상을 검증 하였다.

• 대한기계학회논문집B
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• 제36권5호
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• pp.539-543
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• 2012

셀룰로오스 EAPap 작동기는 생체 모방형 작동기의 하나로 생체적합하고 가볍고 비교적 낮은 전압에서도 큰 변위를 발생시킨다는 장점을 가지고 있다. 셀룰로오스를 재생하면서 셀룰로오스 파이버를 배열함으로써 압전 종이를 만들었다. 한편 셀룰로오스에 탄소나노튜브, 산화금속 나노분말, 전도성 고분자, 이온성 유체등을 물리적, 화학적으로 결합시켜 다양한 하이브리드 나노복합재를 만들었다. 본 논문에서는 셀룰로오스 EAPap 의 제조공정 및 이를 응용한 바이오센서, 화학센서, 유연트랜지스터, 그리고 작동기의 응용 디바이스에 대해 소개한다. 또한 셀룰로오스 EAPap 을 무선으로 구동하는 기술에 대해 소개한다. 이는 생체모방로봇, 정찰 등에 활용될 수 있다.

• 드라이브 ㆍ 컨트롤
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• 제15권4호
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• pp.55-60
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• 2018

Force-controlled electro-hydrostatic actuators have to exhibit high backdrivability, to quickly compensate for force control errors caused by externally disturbed rod movement. To obtain high backdrivability, the servomotor for driving the hydraulic pump, should rotate exactly to such a revolution to compensate for force control errors, compressing or decompressing cylinder chambers. In this study, we proposed a modified velocity control structure, including a robust internal-loop compensator (RIC)-based velocity controller, for the servomotor to improve backdrivability of a force-controlled EHA. Performance improvement was confirmed experimentally, wherein sinusoidal velocity disturbance was applied to the force-controlled EHA, with constant reference input. Its dynamic force control errors reduced effectively, with the proposed control scheme, compared to test results with a conventional motordriver, for motor velocity control.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 1999년도 추계종합학술대회 논문집
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• pp.905-908
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• 1999

In this paper, we present a polysilicon actuator on silicon wafer using surface micromachining technology which employs an electrostatic stepwise driven Scratch Drive Actuator to generate a force that can move an external object. For optical applications, we propose wavelength selector using distributed feedback structures and this micro actuator.

• 드라이브 ㆍ 컨트롤
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• 제12권2호
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• pp.1-6
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• 2015

Recently, the Electro-Hydrostatic Actuator(EHA) has been developed as a result of research on energy saving. EHA is usually composed of a direct driven pump from an electric motor and is available to control cylinder displacement or velocity with high efficiency. In addition, it has the advantage of compactness, minimum leakage and availability of decentralized control. In this study, an EHA system was designed to decrease the path tracking error and manufactured for test. The linearization method provided in AMESim software was used to derive the model of EHA system. The derived model was applied to design the PI-D controller to effectively overcome the disturbance. The effectiveness of this controller was verified by further testing.

• 한국정밀공학회지
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• 제13권8호
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• pp.102-111
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• 1996

This paper presents a proof-of-concept investigation on an active tension control using an ER (electro-rheological) brake actuator. Firstly, an ERF (electro-rheological fluid) which has an inherent reversible feature from Newtonian fluid to Bingham fluid upon applying an electric field is composed, and its property is tested to obtain intrinsic parameters of the Bingham model. An appropriate size of the ER brake is manufactured on the basis of the Bingham model, and dynamic characteristics of the brake are experimentally identified. After formulating a governing equation of motion of the tension control system, a sliding mode controller is designed to achieve a certain desired level of tension. Both simulation and experimental works are undertaken in order to demonstrate the efficiency and feasibility of the proposed active tension control method.

• Composites Research
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• 제32권5호
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• pp.211-215
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• 2019

정적인 상태인 체외 환경(in vitro)에서의 세포배양 과정은 실제 생체 내 환경에서의 세포발달과정과는 많은 차이가 존재한다. 따라서, 체내 환경의 정밀한 모사를 위해서는, 기계적인 자극을 세포에 전달하여 줄 수 있는 동적 세포배양장치가 필수적이다. 하지만 기존의 동적 세포배양장치에는 튜브, 펌프, 모터 등의 비교적 복잡한 장치들을 필요로 하였으며, 전달되는 기계적 자극도 단순한 형태였다. 본 연구에서는 단순한 장치로 구동되는 동적 세포배양장치를 위하여 전기활성고분자(EAP) 구동기를 동력원으로 하는 소형 동적 세포배양장치를 설계하였다. 이 장치는 다양한 기계적 자극을 세포에 전달하는 것이 가능하다.

• Steel and Composite Structures
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• 제41권6호
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• pp.805-820
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• 2021

In this research, the buckling and free vibration of three-phase carbon nanotubes/ fiber/ polymer piezoelectric nanocomposite face sheet sandwich microbeam with microsensor and micro-actuator surrounded in elastic foundation based on modified couple stress theory (MCST) is investigated. Three types of porous materials are considered for sandwich core. Higher order (Reddy) and sinusoidal shear deformation beam theories are employed for the displacement fields. Sinusoidal surface stress effects are extracted for sinusoidal shear deformation beam theory. The equations of motion are derived by Hamilton's principle and then the natural frequency and critical buckling load are obtained by Navier's type solution. The determined results are in good agreement with other literatures. The detailed numerical investigation for various parameters is performed for this microsensor-microactuator. The results reveal that the microsensor-microactuator enhanced by increasing of Skempton coefficient, carbon nanotubes diameter length to thickness ratio, small scale factor, elastic foundation, surface stress constants and reduction in porous coefficient, micro-actuator voltage and CNT weight fraction. The valuable results can be expedient for micro-electro-mechanical (MEMS) and nano-electro-mechanical (NEMS) systems.

• 동력기계공학회지
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• 제17권4호
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• pp.120-130
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• 2013

An adaptive PID sliding mode controller is proposed for the position control of electro-hydrostatic actuator(EHA) systems with system uncertainties and saturation in the motor. An EHA prototype is developed and system modeling and parameter identification are executed. Then, adaptive PID sliding mode controller and optimal anti-windup PID controller are designed and the performance and robustness of the two control systems are compared by experiment. It was found that the adaptive PID sliding mode control system has better performance and is more robust to system uncertainties than the optimal anti-windup PID control system.