• 한국정밀공학회지
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• 제31권5호
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• pp.403-409
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• 2014

For ground-based telescope application, the performance assessment of tip-tilt actuator is important because the optical quality of telescope depends upon the windshake compensation ability of the fast steering secondary mirror. But it is difficult to measure the performance characteristics of the actuators due to the large size mirror and test facilities including the vacuum support and structural frame. In this paper, the full-scale tip-tilt test bed for the large size secondary mirror with diameter of 1m is built and the several tests are performed including the range, resolution and frequency response function. From the measurement results, it is shown that the tip-tilt actuator can successfully compensate the windshake with frequency of maximum 12 Hz and be a candidate for the Giant Magellan Telescope.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2012년도 춘계학술대회 논문집
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• pp.25-26
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• 2012

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2013년도 춘계학술대회 논문집
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• pp.1345-1346
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• 2013

• 한국정밀공학회지
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• 제31권9호
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• pp.813-820
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• 2014

This paper presents design and performance validation of a method for motion compensation using fast steering mirror. First of all, the schematics of the Electro Optical/Infra-Red (EO/IR) and step-stare image gathering system for an aerial reconnaissance are introduced. Because of the steering mirror with low inertia so called Back scan mechanism (BSM), the fast step-stare image gathering technique that is required for taking a high-definition still image will be realized. After then, the BSM hardware includes motors and feedback sensors are introduced. Also, the motion profile for BSM will be designed to compensate roll scan motion of the gimbals. At the end of this paper, designed profile and tracking performance of the EO/IR system with BSM will be validated through experiments.

• Journal of Magnetics
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• 제19권3호
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• pp.300-308
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• 2014

This paper develops a moving-magnet electromagnetic actuator for fast steering mirror (FSM). The actuator achieves a reasonable compromise between voice coil actuator and piezoelectric actuator. The stroke of the actuator is between the strokes of a piezoelectric actuator and a voice coil actuator, and its force output is a linear function of air gap and excitation current within our FSM travel range. Additionally, the actuator is more reliable than voice coil actuator as the electrical connection in the actuator is static. Analytically modeling the actuator is difficult and time-consuming. Alternatively, numerous finite element simulations are carried out for the actuator analysis and design. According to the design results, a real prototype of the actuator is fabricated. An experimental test system is then built. Using the test system, the force output of the fabricated actuator is evaluated. The test results validate the actuator analysis and design.

• Journal of Magnetics
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• 제19권2호
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• pp.130-139
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• 2014

This paper focuses on the modeling and analysis a novel two-axis rotary normal-stress electromagnetic actuator with compact structure for fast steering mirror (FSM). The actuator has high force density similar to a solenoid, but its torque output is nearly a linear function of both its driving current and rotation angle, showing that the actuator is ideal for FSM. In addition, the actuator is designed with a new cross topology armature and no additional axial force is generated when the actuator works. With flux leakage being involved in the actuator modeling properly, an accurate analytical model of the actuator, which shows the actuator's linear characteristics, is obtained via the commonly used equivalent magnetic circuit method. Finally, numerical simulation is presented to validate the analytical actuator model. It is shown that the analytical results are in a good agreement with the simulation results.

• Journal of Magnetics
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• 제20권1호
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• pp.69-78
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• 2015

This paper focuses on the design of a flux-biased rotary electromagnetic actuator with compact structure for fast steering mirror (FSM). The actuator has high force density and its torque output shows linear dependence on both excitation current and rotation angle. Benefiting from a new electromagnetic topology, no additional axial force is generated and an armature with small moment of inertia is achieved. To improve modeling accuracy, the actuator is modeled with flux leakage taken into account. In order to achieve an FSM with good performance, a design methodology is presented. The methodology aims to achieve a balance between torque output, torque density and required coil magnetomotive force. By using the design methodology, the actuator which will be used to drive our FSM is achieved. The finite element simulation results validate the design results, along with the concept design, magnetic analysis and torque output model.

• 한국우주과학회:학술대회논문집(한국우주과학회보)
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• 한국우주과학회 2011년도 한국우주과학회보 제20권1호
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• pp.30.3-30.3
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• 2011

한국천문연구원은 Giant Magellan Telescope Fast Steering Mirror prototype을 개발 중이고, 반사경 제작과 tip-tilt 시스템 제작을 목표로 하고 있다. 반사경은 직경이 1.06m, 두께가 약 140mm, 질량이 약 100kg인 meniscus 타입인 비축 비구면 반사경이다. Tip-tilt 시스템은 바람에 의한 반사경의 진동과 망원경의 tracking jitter를 보정하기 위한 장치로써 tip-tilt 각도가 ${\pm}20"$ 범위 내에서 약 30Hz로 작동하는 시스템이다. 반사경 cell은 반사경 뒷면에 조립되어 반사경 cell 내부에 주입되는 진공과 함께 반사경의 무게를 지지하고, tip-tilt 시스템을 작동시키는 액츄에이터가 장착되는 base structure 역할을 한다. 이 논문에서는 반사경 cell의 초기설계와 반사경 cell에 발생할 수 있는 하중 조건에 따른 응력과 변위, 반사경 cell의 두께에 따른 고유진동수를 해석한 결과들에 대해 논한다.

• 한국광학회지
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• 제19권2호
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• pp.144-149
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• 2008

대구경 레이저 광집속장치의 쿠데(Coude) 광경로를 구성하는 레이저 반사경들의 레이저 빔조사에 의한 열변형과 이에 따른 광파면 왜곡에 대한 연구를 수행하였다. 쿠데 광경로는 연결거울 3개와 고속조종거울 1개로 구성된다. 반사경은 레이저 빔 파장에 대하여 99.5%의 반사율을 갖으며, 반사경 거울면에 조사된 레이저 에너지는 초당 500 W 정도가 흡수된다. 레이저 빔을 5초 동안 조사하면서 유발된 열하중에 의한 거울의 열 변형과 이에 따른 광파면 왜곡을 분석하였다. 광파면 왜곡은 연결거울의 경우 334 nm_PV, 98 nm rms로 나타났으며 고속조종거울은 $11.5\;{\mu}m$_PV, $3\;{\mu}m$ rms로 나타났다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2013년도 춘계학술대회 논문집
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• pp.1083-1084
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• 2013