무인항공기의 실내 항법을 위한 3차원 공간지도작성 및 몬테카를로 위치추정기법

허성식,조성욱,심현철 한국항공우주학회 2012 한국항공우주학회 학술발표회 논문집 Vol.2012 No.4

GPS 신호를 이용할 수 없는 실내환경에서 무인항공기가 자율적으로 비행하도록 운용하기 위해서는 내장된 센서를 사용하는 위치추정기술이 반드시 필요하다. 이를 위해 본 논문에서는 레이저스캐너가 장착된 무인항공기가 3 차원 실내공간지도 내에서 실시간으로 자기위치를 추정할 수 있는 기법을 제시한다. 먼저 효율적인 실내 지도작성 및 위치추정을 위해 Octree 기반의 3 차원 격자지도를 작성하고, 작성된 지도에서 몬테카를로 위치추정기법(Monte Carlo Localization)을 적용해 무인항공기의 3 차원 위치 및 자세를 실시간으로 추정하는 실험을 수행하였다. The indoor navigation technology in GPS-denied environment is necessary to extend the area of UAV operations. In this paper, we propose a real-time three-dimensional indoor navigation method of an UAV equipped with a laser scanner. At first, the octree-based 3-D grid mapping technique is used for efficient map building and indoor localization. To estimate the pose of the UAV, Monte Carlo Localization(MCL) is applied to the 3-D map in real-time and the experiment is conducted.

정지궤도복합위성 기상탑재체 영상의 기하보정을 위한 별 선택 기법 연구

허성식,용기력,최재동,이상률 한국항공우주학회 2015 한국항공우주학회 학술발표회 논문집 Vol.2015 No.11

정지궤도복합위성의 기상탑재체로 촬영하는 영상의 기하보정을 위한 Image Navigation and Registration (INR)은 Kalman filter 로 상태변수를 추정하며 지구 주변의 별을 촬영하여 계산한 별 벡터를 측정벡터입력으로 사용한다. 별을 선택할 때에는 위성이 회전함에 따라 촬영 가능한 별과 그 위치가 계속 변하며 별을 촬영하는 시간도 제한되어 있는 등의 여러 가지 요소를 고려한 최적의 별을 선택하는 기법이 필요하다. 본 논문에서는 별 선택을 위한 조건들을 제시하고 이를 정량화할 수 있는 목적함수를 정의하였으며, 제한된 계산량 이내에서 최적의 별을 선택할 수 있는 방법을 제안하였다. 마지막으로 제안한 방법으로 선택한 별을 사용한 결과와 몬테카를로 시뮬레이션 결과를 비교하였다. The Image Navigation and Registration (INR) system for the Advanced Meteorological Imager (AMI) in GEOKOMPSAT-2A estimates the state vectors using Kalman filter and star vectors as measurements for correction. To select star measurements, an optimal selection algorithm is necessary because the available star list and their locations seen from the satellite varies as the rotation of the satellite. In addition, the time interval to acquire stars is constrained, so a careful choice is required. In this paper, we set up criteria for the star selection, derived an objective function to quantify the criteria, and proposed a suitable star selection algorithm under the several constraints including computational time. The results of the proposed algorithm and Monte Carlo simulation are presented for comparison.

저가형 LIDAR를 장착한 소형 무인항공기의 3차원 실내 항법 및 자동비행

허성식,조성욱,심현철 한국로봇학회 2014 로봇학회 논문지 Vol.9 No.3

The Global Positioning System (GPS) is widely used to aid the navigation of aerial vehicles. However, the GPS cannot be used indoors, so alternative navigation methods are needed to be developed for micro aerial vehicles (MAVs) flying in GPS-denied environments. In this paper, a real-time three-dimensional (3-D) indoor navigation system and closed-loop control of a quad-rotor aerial vehicle equipped with an inertial measurement unit (IMU) and a low-cost light detection and ranging (LIDAR) is presented. In order to estimate the pose of the vehicle equipped with the two-dimensional LIDAR, an octree-based grid map and Monte-Carlo Localization (MCL) are adopted. The navigation results using the MCL are then evaluated by making a comparison with a motion capture system. Finally, the results are used for closed-loop control in order to validate its positioning accuracy during procedures for stable hovering and waypoint-following.

삼차원 입체 인쇄 성형물의 변형모사에 관한 연구

허성식,이정현,Heo, Seong-Sik,Lee, Jeong-Hyeon 한국섬유공학회 1997 한국섬유공학회지 Vol.34 No.6

Deformation of some specimens produced by a stereolithography system was studied experimentally and numerically. Three steps in the rapid prototyping process, part building, part removal, and postcure, imposed significant effects on dimensional accuracy. Dimensions of the specimens were measured after each step. Distortion during part building was much smaller than that caused by the part removal step. The internal residual stress developed during building process was partially released by the removal of the part from the platform. Considerable distortion was also observed after postcure. A finite element computer code was developed to predict the deformation after each step. Shrinkage of each layer cured by the laser beam was simulated by considering thermal shrinkage of a solid layer. In order to simulate shrinkage during postcure process, it was assumed that the postcure occurred from the exterior surface to the interior surface. Heat sink was also assumed on the boundary of the part for the thermal stress analysis. Numerical results were consistent with experimental results for the simple geometry employed in this study.

에어백을 이용한 고정익 무인항공기의 영상기반 자동착륙 실험

허성식,심현철 한국항공우주학회 2008 한국항공우주학회 학술발표회 논문집 Vol.- No.-

Lesslie Newbigin’s Debate with Post-Christendom

허성식 장로회신학대학교 세계선교연구원 2015 선교와 신학 Vol.35 No.-

본 논문은 기독교 신앙과 교회는 기독교공동체 내에서만 아니라, 교회너머의 모든 일반사회 영역에서도 공적이어야 한다는 레슬리 뉴비긴의 주장에 대해 연구하고 있다. 그의 많은 저술 가운데 발견되는 이런 교회의 공적인 부르심과 선교적 책무에 대한 글들을 검토해보는 가운데, 본고는 뉴비긴이 왜 이런 교회의 공공성에 관한 주장을 펴게 되었는지 그 역사적인 맥락을 짚어보면서, 더불어 그의 이런 주장 안에 들어있는 구체적인 내용을 논의해보려 한다. 뉴비긴은 기독교 신앙과 교회의 진정성을 회복하기 위해서는 무엇보다 교회란 일반세상과 격리된 채 있는 ‘게토화된’(ghettoized) 사회나 개개인의 종교적인 만족을 위해 존재하는 ‘사유화된’(privatized) 사회가 아니라, 마치 소금과 빛처럼 세상 가운데 벌거벗은 채로 드러나 있어야 하는 공동체, 즉 ‘공적인’(public) 사회로 하나님이 세상 가운데서 부르시고 보내신 공동체임을 거듭 강조한다. 교회가 본질적으로 공적인 기관임을 뉴비긴은 평생 자기자신의 삶과 자신이 섬겼던 교회와 기관들을 통해서 체득했기에, 뉴비긴에게 있어서 이런 주장은 전혀 생소한 것이 아니다. 그럼에도 불구하고 그의 주장이 새롭게 다가오는 것은 그가 활동했던 서구기독교사회, 특히 영국 기독교가 ‘후기기독교사회’(post-Christendom)로 본격적으로 진입하면서 자연스럽게 나타난 교회의 세속화와 사유화, 게토화 현상 때문이었다. 이런 점에서 본고는 뉴비긴이 이렇게 변질되어가는 후기기독교사회와 논쟁을 벌이고 있는 상황을 주목하고 연구하였다. 뉴비긴의 공적인 신앙과 공적인 교회론의 중심주제들은 “개인적이지만 공적인 복음”, “특수적이지만 공적인 역사적 사건”, “타당하지만 공적인 기독교 신앙의 구조”와 같은 내용을 담고 있고 이런 주장들은 “공적인 신학의 출발점은 지역교회이다”라는 그의 결론으로 귀결된다. 비록 뉴비긴의 공적인 신앙과 교회에 관한 논의가 몇몇 비판적인 의견에서 볼 수 있듯이, 그러면 어떻게 교회가 사회 각 영역에서 공적일 수 있는가에 대해서는 자세한 논의가 부족하기 때문에 구체성이 결여된 면이 있긴 하다. 그럼에도 불구하고 그런 결점을 보완하는 것은 후학들의 몫이라 생각하며, 그가 왜 이런 주장을 하게 되었는지, 이런 주장들이 교회가 본질상 그리고 사역의 현장에서 보다 선교적인 교회가 되는 데 어떤 의미를 던지는가 하는 점은 꼭 생각해보아야 할 가치가 있다고 사료된다. This paper explores Lesslie Newbigin’s argument that the Christian faith and the Church ought to be “public” not only within Christian communities, but also in all spheres of society beyond the boundary of the Christian fellowships. In his continuous dialogue with the post-Christendom in which the Christian faith can be easily privatized, Newbigin explores why and how we should exhort Christians and Christian communities not to live their lives in a ghettoized, privatized, and individualized ecclesiastical sphere, but in all the public spheres of the world. In the second chapter, it discusses the historical background of Newbigin’s discourse on public faith. In the third chapter, the main themes of Newbigin’s discourse on public faith are explored: personal but public gospel, particular but public historical events, plausible but public structure of the Christian faith, local congregations as the crux of public theology, increasing influence of the Christian faith on the public spheres. And finally, in discussing how we can put the Christian faith to practice in all sectors of life in public, both corporately and individually, I will critically evaluate Newbigin’s idea of public faith in the broader sense of its practicality. This research demonstrates that while Newbigin decisively refuted the bad practices of Western Christendom, especially violent evangelism and its complicity with imperialism and colonialism, he re-emphasized the necessity of building up a new type of Christian society in which the gospel could be proclaimed and practiced as public truth within and beyond the local congregations as public truth in all public spheres. As shown in chapter four, it is right to critically point out the lack of specificity of how to put his idea of public faith in the real public life. But I would like to say that he did his job as a guide to where we should go as a Christian community in this post-Christendom era.

The Missional Implications of Lesslie Newbigin’s Shift of Emphasis from Interreligious Dialogues to Religious Pluralism Debates

허성식 장로회신학대학교 기독교사상과문화연구원 2015 장신논단 Vol.47 No.3

As a missionary sent to India Newbigin made a concerted effort to have interreligious dialogue with Hindus. He engaged in intensive interreligious dialogues with them, but such arduous endeavors did not continue in Newbigin’s life. What happened to him? Basically as I agree with Bob Robinson who has examined Newbigin’s reluctance toward interreligious dialogue in his later life, I would like to argue in this paper that the emergence of religious pluralism is another reason that he could not go on his interreligious dialogues. Thus, this paper is to examine the shift of emphasis in Newbigin’s life from interreligious dialogue to religious pluralism debate, and its missional implications. In discussing this shift, firstly it will discuss the reason that Newbigin rejects the well-known typology of exclusivism, inclusivism and pluralism. And then, it will look into the main themes of Newbigin’s critical debates with religious pluralism in different forms: the theory of the Copernican revolution of John Hick and the soteriocentric religious pluralism of Paul Knitter and convergent pluralism of Keith Ward. Finally, it will discuss why Newbigin criticizes religious pluralism as destroying the church. My conclusion is that the emergence of religious pluralism as a new force to threaten the Christian faith in Western Christianity has gradually changed Newbigin’s main concern from interreligious dialogues to religious pluralism debates. Here, from the missional perspective it is certain that Newbigin was sent again as a missionary into the Western Post-Christendom.

무인항공기의 실내비행을 위한 레이저-영상센서 기반의 3차원 항법 연구

허성식,심현철 한국항공우주학회 2012 한국항공우주학회 학술발표회 논문집 Vol.2012 No.11

무인항공기가 GPS 신호를 이용할 수 없는 실내환경에서 자율비행하기 위해서는 내장된 센서에 의한 위치추정기술이 요구된다. 본 논문에서는 틸팅마운트에 장착되어 서보모터로 회전되는 LIDAR 와 카메라를 통합한 센서모듈과 이를 장착한 무인항공기가 3 차원 위치를 실시간으로 추정할 수 있는 기법을 제시한다. 먼저, 서보에 의해 틸팅하는 LIDAR 와 카메라 센서간의 초기장착위치를 보정한 후, 영상에서 추출한 특징점을 LIDAR 로 지향하여 측정한 거리정보를 사용해 EKF SLAM 을 구성하고, 이 기법으로 무인항공기의 3 차원 위치 및 자세를 실시간으로 추정하는 실험을 수행하였다. The indoor navigation technology in GPS-denied environment is necessary to extend the area of UAV operations. In this paper, we propose a real-time three-dimensional indoor navigation method of an UAV equipped with a laser scanner. At first, a new calibration method that estimates relative pose between a tilting-gimbaled laser scanner and a camera using a simple marker is proposed. An EKF SLAM algorithm that uses range data measured by the LIDAR and image features detected and tracked by the camera is tested to estimate three-dimensional pose of an UAV.

지하탐사 및 자원채굴용 무인로봇의 원격운용을 위한 힘반향기법 및 자율주행 연구

허성식,이웅희,심현철,노종호 제어로봇시스템학회 2010 제어로봇시스템학회 국내학술대회 논문집 Vol.2010 No.5

Since the world has been faced with the ell energy crisis, demand on coal is getting increased nowadays. However, workspaces of underground coal mine have an extremely harsh environment to human workers so that developing unmanned mining robot is pressingly required to increase the productivity of underground resources. In order to work in the harsh condition, the robot should have abilities to estimate its pose by fusing heterogeneous sensors such as laser scanner and inertial measurement unit so that the grid-based self-localization algorithm is implemented. In addition, the robot can drive to way point using the estimated pose data in order to reduce human"s workload. Measured data by the sensors on the vehicle is transmitted to a human worker at the remote place so that the worker controls the robot easily through force feedback joysticks to avoid obstacles. A robot testbed is developed to evaluate the algorithms, and the experimental result is presented.

Rice Flour - A Functional Ingredient for Premium Crabstick

허성식,조승목,금준석,Jae W. Park,김동수 한국식품과학회 2011 Food Science and Biotechnology Vol.20 No.6

This study was performed to evaluate rice flour as a functional ingredient for premium crabstick and develop a commercially viable recipe. Physicochemical properties of crabstick pastes with 42% surimi, with various rice flour concentrations (0, 1, 3, and 5%), and other ingredients were evaluated. The physical properties were measured during refrigeration and frozen storage. Rice flour measured at various concentrations (5 to 40% in water) using a DSC demonstrated similar patterns with an endothermic peak at around 63.5^oC. During refrigerated storage, the strength of gels increased gradually, while cohesiveness stayed mostly unchanged. During frozen storage, water retention ability (WRA) gradually decreased as freeze-thaw (F/T) cycles were extended, however the water reduction was minimized as rice flour concentration increased. The optimum level was 1% rice flour concentration for chilled and frozen crabstick. Two crabstick samples (control and 1% rice flour) demonstrated no difference in strength and cohesiveness.