• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.49 no.10
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• pp.821-828
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• 2021

Quadrotors relatively smaller and lighter than other aircraft have a disadvantage of being sensitive to the external disturbances. In order to solve this disadvantage, many studies have been conducted by various control techniques robust to disturbances. In this paper, CMGs (Control Moment Gyros) introducing relatively large control torque with an identical amount of electric powers are applied to cancel the external disturbances. Two CMGs are considered to control the attitude of quadrotors so that a multi-copter installed with two CMGs and four rotors are introduced for this work. Finally, to verify the control performance of the proposed system by the CMGs, a numerical simulation conducted in the given harsh environment.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2016.10a
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• pp.775-778
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• 2016

In this paper, we propose a new method to automatically recognize PRI modulation type of radar signal at ES(Electronic Support) in electronic singal environment. The propose method stores pattern of PRI(Pulse Repetition Interval) of radar signal and uses statistic data, which firstly classifies into 2 classes. Then the proposed method recognizes each PRI signal using statistic characteristic of PRI. We apply various 5 kinds of PRI signal such as constant PRI, jitter PRI, D&S(dwell & switch) PRI, stagger PRI, sliding PRI, etc. The result shows the proposed method correctly identifies various PRI signals.

• Journal of Korea Multimedia Society
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• v.22 no.1
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• pp.35-43
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• 2019

Template tracking refers to the procedure of finding the most similar image patch corresponding to the given template through an image sequence. In order to obtain more accurate trajectory of the template, the template requires to be updated to reflect various appearance changes as it traverses through an image sequence. To do that, appearance images are used to model appearance variations and these are obtained by the computation of the principal components of the augmented image matrix at every iteration. Unfortunately, it is prohibitively expensive to compute the principal components at every iteration. Thus in this paper, we suggest a new Sliding Window based truncated URV Decomposition (TURVD) algorithm which enables updating their structure by recycling their previous decomposition instead of decomposing the image matrix from the beginning. Specifically, we show an efficient algorithm for updating and downdating the TURVD simultaneously, followed by the rank-one update to the TURVD while tracking the decomposition error accurately and adjusting the truncation level adaptively. Experiments show that the proposed algorithm produces no-meaningful differences but much faster execution speed compared to the typical algorithms in template tracking applications, thereby maintaining a good approximation for the principal components.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.49 no.3
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• pp.213-219
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• 2021

In this paper, an incremental twisting compensator is proposed for improving the performance of helicopter control and tested on an in-house full-scale helicopter simulator. The proposed compensator has a merit in that an incremental control input (a second-order sliding mode control input or so-called twisting control input) is simply added to improve the performance of helicopter control, while the original flight control structure remains untouched. The proposed control technique has been shown to improve the transient and steady-state response of the in-house helicopter simulator.

• Journal of the Korean Society of Mechanical Technology
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• v.20 no.6
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• pp.901-905
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• 2018

The objective of this study is to investigate the effect of torque variation on stress distributions in A-IMS module with both side tubular shaft yoke by numerically. In order to achieve this, the torque value was increased from 10Nm to 40Nm, and the results of this work were confirmed in terms of Von-mises Stress and the displacement characteristics. As the torque in module assembly was increased, the stress in tubular shaft york and splined shaft york was increased linearly. The indentation due to the steel ball was occurred in over $40N{\cdot}m$ torque which is over the yield strength condition. The largest displacement occurred in the tubular shaft yoke 1, however, it does not exceed the yield strength and is supposed to be restored due to the elasticity. Therefore, it was concluded that there is no problem for the manufacturing of A-IMS with both side tubular shaft yoke.

• IEMEK Journal of Embedded Systems and Applications
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• v.16 no.4
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• pp.137-143
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• 2021

We propose an adaptive non-singular terminal sliding-mode control for the fast finite-time convergence (FANTSMC) in robot manipulator. The proposed FANTSMC approach is developed to be applied without singularity in robot manipulator, which has a new pole-placement control with the non-singular terminal sliding variable while generating the desirable control torque. Moreover, the switching gain is designed to suppress the time-delayed estimation error appropriately, which aims at providing the high robust tracking performance. Also, the proposed one employs one-sample delayed information to cancel out the system uncertainties and disturbances. For these reasons, it offers strong attraction within the finite time. It is shown that the tracking performance of the proposed FANTSMC approach is guaranteed to be uniformly ultimately bounded through the Lyapunov stability. The effectiveness of the proposed FANTSMC approach is illustrated in simulations, which is compared with that of the up-to-date control approach.

• Journal of the Korean Society for Precision Engineering
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• v.14 no.1
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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.

• Proceedings of the Korea Information Processing Society Conference
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• 2021.05a
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• pp.263-266
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• 2021

근래의 드론 산업은 다양한 분야에서 사용이 확대되고 있으나 규제 등 여러 가지 사회적 진입장벽으로 시장 진입에 애로사항이 도출되고 있다. 본 논문에서는 드론 산업의 여러 제약 중 배터리의 제한적인 용량으로 장시간 비행이 어려운 문제를 개선하고자 승강식 드론스테이션을 개발하였다. 승강식 드론스테이션은 드론의 비행 중 배터리가 방전될 시 충전 및 정비를 할 수 있고, 드론 간의 통신 중계기 역할을 수행한다. 본 논문에서는 스테이션에 드론이 접근 시 슬라이딩 도어를 개폐하기 위하여 초광대역 통신을 이용한 거리 측정과 위치 인식 시스템에 대한 내용을 기술하였다.

• The Bulletin of The Korean Astronomical Society
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• v.45 no.1
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• pp.68.1-68.1
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• 2020

외계행성 대기 연구를 위한 투과스펙트럼 관측에 적합한 측분광기를 개발하고 있다. 이 측분광기의 광학적 특성은 380~685nm의 파장범위, FOV 10', R>~400이며, 슬릿부, collimator, VPH grism, imaging lens와 CCD로 구성되어 있는데, 보현산천문대 1.8m 망원경의 CIM(Cassegrain Interface Module)에 카트리지 방식으로 장착되어 사용한다. 그 중 doublet 렌즈 2개를 대칭으로 배치하여 초점거리 280mm가 되도록 만든 collimator는 슬릿을 통과한 f/8 입사광에서 지름 35 mm의 pupil을 만드는데, 이곳에 VPH grism을 설치하였다. collimator 렌즈는 axial spring과 radial spring으로 알루미늄 barrel에 고정하였다. 이 collimator barrel은 CIM에 쉽게 장탈착 할 수 있도록 모듈화 하였다. Collimator Barrel에 대한 구조 해석 결과, 망원경 이동에 따른 중력에 의한 변형은 충분히 작았다. Grism은 슬라이딩 형태로 장착되어 영상 확인도 가능하도록 설계하였다.

• Transactions of Materials Processing
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• v.32 no.1
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• pp.5-11
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• 2023

The aim of this study is to manufacture an aluminum pipe yoke of automotive steering system for lightweight. In a multistage cold forging process for aluminum pipe yoke, the surface defects frequently occur due to excessive deformation or friction during extrusion process for forming hollow pipe part. It is import to reduce the friction between the material and the forging die. This study investigated a multistage forging process with sliding die to reduce friction for aluminum pipe yoke. After evaluating by FE analysis, the forging experiment with the sliding die was carried out. As a result, it was possible to manufacture a sound aluminum pipe yoke.