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Three-dimensional Visual Mapping of Underwater Ship Hull Surface Using Piecewise-planar SLAM
Seonghun Hong,김진환 제어·로봇·시스템학회 2020 International Journal of Control, Automation, and Vol.18 No.3
In-water visual ship hull inspection using unmanned underwater vehicles needs to be performed at very close range to the target surface because of the visibility limitations in underwater environments mainly due to light attenuation, scattering, and water turbidity. These environmental challenges result in ineffective photometric and geometric information in hull surface images and, therefore, the performance of conventional three-dimensional (3D) reconstruction techniques is often unsatisfactory. This paper addresses a visual mapping method for 3D reconstruction of underwater ship hull surface using a monocular camera as a primary mapping sensor. The main idea of the proposed approach is to model the moderately curved hull surface as a combination of piecewise-planar panels, and to generate a global map by aligning the local images in a two-dimensional reference frame and correcting them appropriately to reflect the information of perspective projections of the 3D panels. The estimated 3D panels associated with the local images are used to extract the loop-closure relative measurements in the framework of simultaneous localization and mapping (SLAM) for precise camera trajectory estimation and 3D reconstruction results. The validity and practical feasibility of the proposed method are demonstrated using a dataset obtained in a field experiment with a full-scale ship in a real sea environment.
Development of a Safe Manipulator using Spring-Clutches
SeongHun Hong,Junho Choi,Woosub Lee,Sungchul Kang,Hyeongcheol Lee 제어로봇시스템학회 2013 제어로봇시스템학회 국제학술대회 논문집 Vol.2013 No.10
For physical safety of a service robot, various safe mechanisms have been studied and developed. Most researches on safety concentrated on safe joint component, and experimental results in situations that the safety component is well-functioned in 1 joint level. In cases of multi-axis, however, there exist many constraints when the safe component is mounted to the multi-axis manipulator, for example, the weight and/or volume of the component, the degradation of the safety performance due to the influence of the gravity as the pose of manipulator. So, it is realistically difficult to develop the manipulator with the safety component. This paper presents a safe manipulator with safety component at each joint to overcome practical limitations. Through experiments of unconstrained and constrained collision, it is shown that a new safe manipulator is mechanically safe.
홍성훈 ( Seonghun Hong ),장영운 ( Young Woon Chang ),변종규 ( Jong Kyu Byun ),김민제 ( Min Je Kim ),채정민 ( Jung Min Chae ),박선희 ( Sun Hee Park ),오치혁 ( Chi Hyuk Oh ),박용구 ( Yong Koo Park ) 대한소화기학회 2015 대한소화기학회지 Vol.66 No.4
Gastric cancer frequently disseminates to the liver, lung, and bone via hematogeneous, lymphatic, or peritoneal routes. However, gastric adenocarcinoma that metastasize to the colon and that shows typical linea platisca pattern on colonofiberscopy has rarely been reported. Recently, the authors experience a case of advanced gastric cancer with colonic metastases in a 55-year-old female patient. Multiple colonic lymphoid hyperplasias were detected on colonofiberscopy and biopsy revealed metastatic gastric cancer to the colonic wall. She was treated with mFOLFOX (5-FU, oxaliplatin, leucovorin) and has achieved stable disease status without disease progression. Herein, we report a rare case of signet ring-cell gastric cancer which metastasized to the colon in the form of multiple colonic lymphoid hyperplasias. (Korean J Gastroenterol 2015,66:221-226)
영상 모자이킹을 통한 수중 검사를 위한 호버링 타입 AUV 시스템 개발
홍성훈(Seonghun Hong),박정홍(Jeonghong Park),김태윤(Taeyun Kim),윤석민(Sukmin Yoon),김진환(Jinwhan Kim) 한국해양공학회 2016 韓國海洋工學會誌 Vol.30 No.3
Recently, UUVs (unmanned underwater vehicles) have increasingly been applied in various science and engineering applications. In-water inspection, which used to be performed by human divers, is a potential application for UUVs. In particular, the operational safety and performance of in-water inspection missions can be greatly improved by using an underwater robotic vehicle. The capabilities of hovering maneuvers and automatic image mosaicking are essential for autonomous underwater visual inspection. This paper presents the development of a hover-capable autonomous underwater vehicle system for autonomous in-water inspection, which includes both a hardware platform and operational software algorithms. Some results from an experiment in a model basin are presented to demonstrate the feasibility of the developed system and algorithms.
Safe manipulation을 위한 Spring-clutch 개발 및 안전 전략
홍성훈(Seonghun Hong),최동은(Dongeun Choi),양기훈(Gi-Hun Yang),최준호(Junho Choi),강성철(Sungchul Kang),이형철(Hyeongcheol Lee) 대한기계학회 2010 대한기계학회 춘추학술대회 Vol.2010 No.11
In this study, a novel safe joint mechanism and safety strategy to ensure inherent safety for safe manipulation are presented. The Spring-clutch(SC) is a simple passive mechanism that consists of a spring and cam. When a torque less than a threshold is applied, the SC functions as a rigid joint between the input and the output. However, when the applied torque exceeds the threshold, the SC is released to reduce the collision force. After the applied torque is removed, the SC returns to its original position without additional operations. In addition, a compact joint torque sensor is added to the SC to measure the joint torque, which is used for active compliance control. The SC, however, may not be released depending on the configuration of the manipulator, i.e. singular position. When the manipulator is ill-posed, the applied external torque due to the force becomes zero, which makes the SC fail to work. A safe strategy to ensure safety of the manipulator with the SC is presented.