퍼지제어를 이용한 용접선 추적용 아크센서에 관한 연구

조시훈,김재웅 대한용접접합학회 1995 대한용접·접합학회지 Vol.13 No.1

Experimental models which are able to determine the deviation between weld line and weaving center by measuring the weld current during welding were proposed for the gas metal arc welding process. The models were used for developing a weld seam tracking system which controls the weaving speed of a welding torch. However, it was revealed that the tracking result of the system is affected by the welding conditions. Thus an arc sensor system was developed by using fuzzy control approach for overcoming the difficulty of modelling the nonlinear process. The rule base and parameters of the fuzzy control system were determined on the basis of the results of experiments. This fuzzy control system has shown the successful tracking capability for the wide operating range of welding conditions.

The Asymptotic Behaviour of the Averaging Value of Some Dirichlet Series Using Poisson Distribution

조시훈 영남수학회 2019 East Asian mathematical journal Vol.35 No.1

We investigate the averaging value of a random sampling of a Dirichlet series with some condition using Poisson distribution. Our result is the following:Let $L(s)=\sum_{n=1}^{\infty}\frac{a_n}{n^s}$ be a Dirichlet series that converges absolutely for $\mathrm{Re}(s)>1$. If $X_t$ is an increasing random sampling with Poisson distribution and there exists a number $0<\alpha<\frac{1}{2}$ such that $\sum_{n\leq u}a_n\ll u^{\alpha}$, then we have $$\mathbb{E}L(1/2+iX_t) = O(t^{\alpha}\sqrt{\log t}),$$for all sufficiently large $t$ in $ \mathbb{R} $. As a result, we get the behaviour of $L(\frac{1}{2}+it)$ such that $L$ is a Dirichlet $L$-function or a modular $L$-function, when $t$ is sampled by the Poisson distribution.

다중개성 운영체계의 구현에 관한 연구 : 직접 프로시져 호출 방식의 통신기법

조시훈,방남석,이준원,Cho, Shi-Hoon,Bang, Nam-Seok,Lee, Joon-Won 한국정보처리학회 1998 정보처리논문지 Vol.5 No.9

다중개성을 지원하는 운영체계는 각 사용자의 필요성에 따라 수정과 확장이 용이하게 이루어져야만 한다. 마이크로커널 구조의 운영체계로서 적합한 반면, 프로세스간 통신(interprocess communication: IPC)에서 발생되는 마이크로커널구조의 부담 때문에 시스템 성능이 저하되는 문제점을 갖고 있다. 본 논문에서는 기존의 IPC 기법 성능을 개선하기 위하여 운영체계의 구성요소들간에 직접 프로시져 호출방식의 새로운 IPC 기법을 제안한다. 새로운 기법에 의한 통신 부담은 최상의 경우에는 로컬 프로시져 호출 수준이고, 최악의 경우에도 기존의 메시지전송 통신기법보다는 성능이 향상된다. An operating system should be easy to extend and to be customized to accomodate the diverse needs when it is to support multiple personalities. Though microkernel is the best as architecture for such customization, it raises performance issues due to its intrinsic overhead in interprocess communication. In this paper, we present a new !PC mechanism that overcomes the traditional IPC performance lag by providing a direct bridge between processes. The communication overhead is similar to the one of local procedure call, which is the known minimal overhead. Even in its worst case, our scheme is shown to pcrfonn better than the other alternative, the message passing scheme.

상변태를 고려한 탄소강 용접부의 잔류응력 해석에 관한 연구

조시훈,김재웅,Jo, Si-Hun,Kim, Jae-Ung 대한기계학회 2001 大韓機械學會論文集A Vol.25 No.3

Welding process generates distortion and residual stress in the weldment due to rapid heating and cooling. Welding distortion and residual stress in the welded structure result in many troubles such as dimensional inaccuracies in assembling and safety problem during service. The accurate prediction of welding residual stress is thus very important to improve the quality of weldment and find the way to reduce itself. This paper suggests new analysis method to predict welding residual stress by considering solid phase transformation during welding process. Using the method, analysis is performed for medium and low carbon steel. The analysis result for medium carbon steel reveals that case considering phase transformation has compressive residual stress in contrast with the case neglecting phase transformation because of martensite formation. However, for the case of low carbon steel, residual stress shows little difference between the case considering phase transformation and the other case, because it has small transformation strain and recovers rapidly stress after phase transformation.

아크용접에서 전기적신호를 이용한 용접공정의 감시 및 제어

조시훈,김재웅 대한용접접합학회 1998 대한용접·접합학회지 Vol.16 No.6

시선안정화 제어시스템의 실시간 불균형 모멘트 보상기법

조시훈(Sihun Jo) 한국소음진동공학회 2016 한국소음진동공학회 논문집 Vol.26 No.3

카메라 기반 강화학습을 이용한 드론 장애물 회피 알고리즘

조시훈(Si-hun Jo),김태영(Tae-Young Kim) 한국컴퓨터그래픽스학회 2021 컴퓨터그래픽스학회논문지 Vol.27 No.5

드론 자율비행 기술 중 장애물 회피는 드론이나 주변 환경의 손상을 방지하고 위험을 예방할 수 있도록 하는 매우 중요한 기술이다. LiDAR 센서 기반 장애물 회피방식은 비교적 높은 정확도를 보여 최근 연구에서 많이 활용되고 있지만, 단가가 높고 시각 정보에 대한 처리 능력이 제한적인 단점이 있다. 따라서 본 논문은 단가가 상대적으로 저렴하고 시각 정보를 이용한 확장성이 높은 카메라 기반 PPO(Proximal Policy Optimization) 강화학습을 이용한 드론의 장애물 회피 알고리즘을 제안한다. 3차원 공간상의 학습환경에서 드론, 장애물, 목표지점 등을 무작위로 위치시키고, 가상 카메라를 이용하여 전면에 설치된 스테레오 카메라를 통해 스테레오 영상정보를 얻은 다음 YOLOv4Tiny 객체 검출을 수행한다. 그리고 난 후 스테레오 카메라의 삼각측량법을 통해 드론과 검출된 객체간의 거리를 측정한다. 이 거리를 기반으로 장애물 유무를 판단하고, 만약 장애물이면 패널티를 책정하고 목표지점이면 보상을 부여한다. 본 방법을 실험한 결과 카메라 기반 장애물 회피 알고리즘은 LiDAR 기반 장애물 회피 알고리즘과 비교하여 충분히 비슷한 수준의 높은 정확도와 평균 목표지점 도달시간을 보여 활용 가능성이 높음을 알 수 있었다. Among drone autonomous flight technologies, obstacle avoidance is a very important technology that can prevent damage to drones or surrounding environments and prevent danger. Although the LiDAR sensor-based obstacle avoidance method shows relatively high accuracy and is widely used in recent studies, it has disadvantages of high unit price and limited processing capacity for visual information. Therefore, this paper proposes an obstacle avoidance algorithm for drones using camera-based PPO(Proximal Policy Optimization) reinforcement learning, which is relatively inexpensive and highly scalable using visual information. Drone, obstacles, target points, etc. are randomly located in a learning environment in the three-dimensional space, stereo images are obtained using a Unity camera, and then YOLov4Tiny object detection is performed. Next, the distance between the drone and the detected object is measured through triangulation of the stereo camera. Based on this distance, the presence or absence of obstacles is determined Penalties are set if they are obstacles and rewards are given if they are target points. The experimennt of this method shows that a camera-based obstacle avoidance algorithm can be a sufficiently similar level of accuracy and average target point arrival time compared to a LiDAR-based obstacle avoidance algorithm, so it is highly likely to be used.

교합 붕괴 환자에서 수직 고경을 증가한 보철 수복

조시훈(Si-hoon Jo),정수양,남현석(Hyun-seok Nam),송광엽(Kwang-yeob Song),박주미(Ju-mi Park),안승근(Seung-geun Ahn) 대한턱관절교합학회 2010 구강회복응용과학지 Vol.26 No.4

다중개성 운영체계의 구현에 관한 연구 ; 직접 프로시져 호출 방식의 통신기법

조시훈(Cho Shi Hoon),방남석(Bang Nam Seok),이준원(Lee Joon Won) 한국정보처리학회 1998 정보처리학회논문지 Vol.5 No.9

An operating system should be easy to extend and to be customized to accomodate the diverse needs when it is to support multiple personalities. Though microkernel is the best OS architecture for such customization, it raises performance issues due to its intrinsic overhead in interprocess communication. In this paper, we present a new IPC mechanism that overcomes the traditional IPC performance lag by providing a direct bridge between processes. The communication overhead is similar to the one of local procedure call, which is the known minimal overhead. Even in its worst case, our scheme is shown to perform better than the other alternative, the message passing scheme.

아크센서를 위한 GMA 용접 공정의 모델링에 관한 연구

조시훈,김재웅 嶺南大學校 工業技術硏究所 1994 工業技術硏究所論文集 Vol.22 No.2

Experimental model which are able to determine the deviation between weld line and weaving center by measuring the weld current during welding were proposed for the gas metal arc welding process. The models were developed by using the filtered current signals and filtered-averaged ones for the various welding conditions. The models were used for developing a weld seam tracking system which controls the weaving speed of a welding torch. It could be shown that there is a successful capability of seam tracking in flat welding of V-grooved butt Joints. Comparing the weld current signal processing methods, the models of filtered signal showed better tracking ability than those of filtered-averaged signal.