• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.665-666
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• 2006

In precision laser microfabrication, focusing is essential to acquire good machining precision and uniform machining quality. If it does not perform, laser machining cannot be realized. So, confocal scanning method with high depth resolution is used for focus detection technique. This paper is concerned with a procedure for design, analysis and performance test of an autofocus fine actuating stage, which is composed of flexure-hinge type lever mechanism and piezoelectric actuator. Through series of analytical design, the stage is simplified as a rigid bodies(lever and main body) and springs(flexure hinges). The simplified model was applied to determine the dimension of flexure hinges and lever. After structural analysis confirmed design requirement, an actual stage was made and verified through an experiment on the static and dynamic characteristics(maximum stroke and 1st natural frequency). The fabricated stage was satisfied with the design requirement.

• Proceedings of the KIEE Conference
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• 2003.07c
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• pp.1929-1931
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• 2003

본 연구에서 제안하는 마이크로 밸브는 열공압 방식으로 구동되고 제작비용이 저렴한 indium tin oxide (ITO) 및 polydimethylsiloxane (PDMS)로 제작되었다. 제안된 마이크로 밸브의 구조는 ITO 히터, SU-8 층, PDMS membrane, 그리고 PDMS 채널로 구성되어 있다. 제작된 열공압 구동기의 PDMS membrane의 변위는 현미경의 초점 거리의 변화로 측정하였으며 히터에 160mW 전력 인가 시 변위는 대략 $132{\mu}m$이다. 마이크로 밸브의 히터에 인가 전력에 따른 유량측정은 DI water를 사용하여 측정하였고 inlet 압력은 1.2kpa를 인가하여 측정하였다. 히터 인가 전력이 영일 경우 채널 폭이 $200{\mu}m$와 $400{\mu}m$인 마이크로 밸브의 유량은 각각 대략 $36{\mu}{\el}$/min과 $110{\mu}{\el}$/min 이었다. 채널 폭이 $200{\mu}m$와 $400{\mu}m$인 마이크로 밸브의 유량은 히터 인가 전력이 각각 70mW와 160mW에서 영이 되었다.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.18 no.1
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• pp.11-19
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• 2008

This paper proposes small VCM(voice coil motor) type, auto-focusing and zoom actuators for mobile information devices. In order to meet the large output displacement within small height restriction, the proposed auto-focusing actuator adopts curved suspensions, which are similar to a leaf-spring type suspension of optical disk drives. The sensitivity of design parameters on output displacement and dynamic performance is implemented using ANSYS (3D FEM tool) to determine the optimal geometry and stiffness of the curved suspensions. This paper also investigates a new zoom actuator without a suspension supporting a bobbin. The zoom actuator uses a moving rail and a stoper mechanism by generating rotational force at lens holder. Magnetic flux density of the zoom actuator are calculated by both the FEM and permeance method. Experiments using prototypes of the proposed focusing and zoom models show that both actuators meet the required displacement and performance.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.43 no.8
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• pp.757-764
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• 2015

Mathematical modeling of focal plane compensation device in the small earth-observation satellite camera has been conducted experimently for compensation of micro-vibration disturbance. The PZT actuators are used as control actuators for compensation device. It is quite difficult to build up mathematical model because of hysteresis characteristic of PZT actuators. Therefore, the compensation device system is assumed as a $2^{nd}$ order linear system and modeled by using MATLAB System Identification Toolbox. It has been found that four linear models of compensation device are needed to meet 10% error in the input frequency range of 0~50Hz. These models describe accurately the dynamics of compensation device in the 4 divided domains of the input frequency range of 0~50Hz, respectively. Micro-vibration disturbance can be compensated by feedback control strategy of switching four models appropriately according to the input frequency.

• Korean Journal of Optics and Photonics
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• v.19 no.2
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• pp.132-139
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• 2008

In scanning laser optical tweezers, high speed scanning stages are used to manipulate a laser beam spot. Due to the inertia of the stage, the output scanning signal decreases with increased frequency of the input signal. This discrepancy in the signals is difficult to observe since most of the energy from the laser beam is blocked out to avoid CCD damage. In this paper, we propose two methods to alleviate these problems. Firstly, frequency responses of piezo stages are measured to analyze the signal drops and the input signal is compensated accordingly. Secondly, an overlay of the scanning path is drawn on the live monitoring screen to enhance the visibility of the scanning path. The result is a drop-compensated scanning with clear path view.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.11a
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• pp.136-139
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• 2006

In this paper we propose a small form factor actuator using an inclined motion guide for auto-focusing and zoom motions for mobile information devices. The novel structure using the inclined motion guide and a lens-supporting beam converts the circular motion by an ultrasonic motor into the linear motion of the optical lens. The proposed actuator has a simple structure to minimizing the mechanical tolerance, and the stroke is easy to modify by controlling the inclined angle. Experiments using a prototype verify the validity of the model as small form factor optical actuator.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.11a
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• pp.750-755
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• 2005

This paper proposes a small VCM (Voice coil motor) type actuator using curved suspensions for auto-focusing and zoom motions for mobile information devices. 1'he proposed focusing actuator adopts a nontraditional type of suspension using curved beams in order to extend output displacement within small height restriction. The curved beam is similar to the leaf spring type which is usually used in optical disk drives. In addition, three different materials are considered for the curved suspension model, and Aluminum shows the best dynamic characteristics. The proposed zoom actuator does not use a suspension supporting bobbin but a moving rail and a sloper mechanism by generating rotational force at lens holder. The sensitivity of design parameters on output performance is studied using ANSYS (3D FEM tool). Experiments using a prototype of the proposed actuator model verified the analytical prediction and performance.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.11a
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• pp.744-749
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• 2005

In this paper, a lens actuator for mobile devices is proposed using stack type piezoelectric materials. In general, the deformation of PZT actuators is not enough for lens motion when the allowed voltage is applied. The small stroke problem can be solved by accumulating a lot of small displacements in high frequency. In this paper, a new inch-worm type model for focusing actuator is suggested based on the interaction of inertial and frictional forces. Theoretical analysis and simulation using ANSYS are performed to verify the feasibility of the inch-worm PZT actuator model. Various types of clamps are considered to determine the effect of frictional force on the motion, and appropriate clamp-actuator models are proposed. The proposed models are experimentally verified and the experimental results show high correspondence with theoretical and simulated values. The inch-worm type focusing actuator enable a large stroke with 7.79 mm/sec with 10kHz and 10V.

• Korean Journal of Optics and Photonics
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• v.1 no.2
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• pp.198-203
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• 1990

In this paper, a system has been proposed for the measurement of the spectral characteristic of semiconductor light sources driven by very short pulse currents. This system has been constituted a monochrometer of 600 groovedmm grating and of 275 mm focal length, X-Y recorder, scanning motor which enables the system to get the analog data, and amplifier coupled with peak detector. Especially, peak detector was used to convert the short pulse signal to continuous one. In order to verify the resolution with slit width, several slits were made by the hands. By using this system, the spectra of commercial LEDs, AlGaAdGaAs LD, and InGaAsPIInP BH-LD which were driven with pulse current (duty cy$e = 0.01) were measured. From these measurements, it has been shown that the proposed system has about 1 A1$\AA$ resolution and 10$\mu$W sensitivity.

• Proceedings of the KIPE Conference
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• 2011.07a
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• pp.206-207
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• 2011

지금까지 영구자석 동기 전동기의 구동에 있어서 약자속에 대한 연구는 대부분 정상상태에서의 전류제어성능에 초점이 맞춰져 왔다. 그러나 전류 지령이 급변하는 상황에서는 신속하게 정상상태에 이르는 것이 중요함에도 불구하고, 이에 대한 연구는 많지 않았다. 본 논문에서는 약자속(Flux Weakening) 운전시 전류제어의 과도상태를 개선하여 정상상태에 빠르게 도달하도록 하는 약자속기법을 제안하였다. 제안된 방법은 정상상태의 전류 지령을 결정하는 약자속제어기와, 과도상태에서 전압 여유분을 확보하여 빠르게 정상상태에 이르도록 하는 과도 지령 수정기로 구성된다. 컴퓨터를 이용한 모의 실험과 11kW 영구자석 전동기에 대한 실험을 통하여 제안된 약자속기법의 성능을 확인하였다.