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위상평면을 이용한 유압식 이족 휴머노이드 로봇의 보행제어
최동일(Dongil Choi),김정훈(Jung-Hoon Kim),김정엽(Jung-Yup Kim) 제어로봇시스템학회 2011 제어·로봇·시스템학회 논문지 Vol.17 No.3
This paper proposes a novel control method using phase plane for a hycraulic biped humanoid robot. In biped walking control, it is much more difficult to control the posture of a biped robot in the coronal plane because the supporting area formed by the both feet in the coronal plane is much narrower than that of the sagittal plane. When the biped robot walks stably, the phase portrait of the pelvis in the coronal plane makes an elliptical shape. From this point of view, we develop an ankle torque controller and a foot placement controller for tracking the desired phase portrait during walking. We design these controllers by using simulations of a simplified compass gait biped model to regulate the desired portrait of pelvis. The effectiveness of the proposed control method is proved through full-body dynamic walking simulations and real experiments of the SARCOS hydraulic biped humanoid.
블루레이 광 조형 장치를 이용한 골 조직 재생용 스캐폴드 제작
김재훈(JaeHun Kim),최동일(DongIl Choi),전민호(MinHo Jeon),임동혁(DongHyuck Lim),박지환(JiHwan Park),이진우(JinWoo Lee),윤원수(WonSoo Yun) 대한기계학회 2013 대한기계학회 춘추학술대회 Vol.2013 No.12
One of the most important element in tissue engineering is a scaffold which have porous structure, proper mechanical strength, biocompatibility and biodegradability. In this study, we fabricated a scaffold using a blu-ray based micro-stereo lithography(MSTL) apparatus. The material used in scaffold fabrication was PPF-DEF, which is well-known for biodegradable photopolymer. Through post-curing process, the comprehensive strength of the fabricated scaffold was enhanced. To demonstrate the biocompatibility of PPF-DEF scaffold, MC3T3-E1 pre-osteoblast cell was seeded onto PPF-DEF scaffold and cultured for 3 days. The result shows that the PPF-DEF scaffold fabricated by a blu-ray based micro-stereo lithography apparatus is applicable to bone tissue regeneration.
김태수(Tae Soo Kim),최동일(Dongil Choi) 대한기계학회 2023 대한기계학회 춘추학술대회 Vol.2023 No.11
Unlike wheeled robot platforms, legged robots experience motor load even when standing still. To address this issue, this paper proposes a novel gravity compensation mechanism by enhancing the existing variable gravity compensation device, specifically focusing on improving the slow torque variation for legged robots. The proposed mechanism introduces several additional components into the conventional gravity compensation system. The study examines the reduction in current consumption achieved by implementing this new gravity compensation mechanism on the robot, addressing the challenge of motor loading during stationary postures in legged robots.
멀티비전을 이용한 실시간 테니스 공 궤적 및 낙하지점 예측방법
양요셉(Yo Seph Yang),최동일(Dongil Choi) 대한기계학회 2021 대한기계학회 춘추학술대회 Vol.2021 No.11
Recently, the development of robots that can exercise and play sports with humans is actively progressing. In sports such as tennis and table tennis, it is important to predict the trajectory of a moving ball to receive the ball. The problem of predicting the trajectory of a ball using robot camera images is a topic that is being actively studied in the field of computer vision. In this paper, we introduce a tennis ball trajectory prediction method using a multi-vision system. In order to predict the trajectory of the ball, the identification of the position and speed of the tennis ball must be prioritized. Our multi vision system sets up two cameras and estimates ball position and landing point in real-time through object detection. The performance of the proposed method was evaluated through Gazebo simulation. As a result of predicting landing points for 500 samples with a tennis ball speed of 65 to 90 km/h, the x-axis error MAE is 0.3 m, the RMSE is 0.406 m, the y-axis error MAE is 0.065 m, and the RMSE is 0.119 m.
비전 센서를 이용한 실내 자율주행 이동 로봇의 자기위치추정
이채현(Chae-Hyun Lee),최동일(Dongil Choi) 대한기계학회 2021 대한기계학회 춘추학술대회 Vol.2021 No.11
Self-localization of a robot is important to performing autonomous driving. Using this algorithm, it is used to plan routes, avoid obstacles, and map the surrounding environment. In this paper, in order to achieve more accurate self-localization performance by fusing wheel odometry and visual-inertial odometry information, we introduce self-localization performance and error ratio for each odometry. A total of two experiments were conducted to evaluate its performance. First, a specific route repetitive driving experiment based on speed control. Second, an arbitrary route long-distance driving experiment using a speed control-based joystick was conducted. As a result, wheel odometry appears to form a similar trajectory compared to the reference path by speed command, but the actual robots arrival point occurs error due to slipping between the wheel and the ground. In particular, as the distance increases, the error accumulates. Visual-Inertial odometry shows that it has a relatively small error compared to wheel odometry.
초거대 다당류 사크란과 키토산을 이용한 하이드로겔의 합성 및 팽윤특성 분석
신호준 ( Hojoon Shin ),권순영 ( Soon-young Kwon ),최동일 ( Dongil Choi ) 한국키틴키토산학회 2021 한국키틴키토산학회지 Vol.26 No.2
본 연구에서는 사크란-키토산 하이드로겔을 성공적으로 합성하였으며 팽윤 특성을 분석하여 다음과 같은 결론을 얻었다. (1) 사크란을 고분자인 키토산으로 가교함으로써 기존의 사크란 겔 이상의 높은 함수율을 획득할 수 있었다(98~99%). (2) FT-IR, TGA, DSC, XRD 분석을 통해 사크란과 키토산 사이의 아마이드 결합에 의해 사크란-키토산 겔이 합성되었음을 확인하였다. (3) 재팽윤시 블록 타입 하이드로겔은 필름 타입 하이드로겔 보다 빠른 팽윤과 더 높은 함수율 보였다. 염을 첨가하면 겔의 함수율이 감소하는 경향을 보였는데 염의 농도가 높을 수록 함수율 감소가 컸으며 필름 타입 하이드로겔에서 감소폭이 더 컸다. 이는 염에 의해 사크란의 나노 루프(nanoloop)가 해체되어 물분자의 포집능력이 감소하였으며, 2가 양이온이 복수의 COO<sup>-</sup>와 반응하여 가교효과를 발휘하여 재팽윤을 억제하였기 때문으로 사료된다. Sacran is a heteroanionic polyelectrolyte, forms liquid crystal (LC) gels at low concentration (c > 0.5 wt%) and has high water contents (97.5 ~ 98.3 wt%). Although various researchers reported chemically crosslinked sacran gels with a more stable structure, water content of these sacran gels was lower than that of conventional sacran gel. In this present study, we newly prepared and characterized chemically crosslinked-hydrogel composed of a mega molecular polysaccharide sacran and chitosan with high water content. We successfully synthesized a chemically crosslinked sacran-chitosan hydrogel by a condensation reaction with DMT-MM. Crosslinking between carboxyl group of scran and amine group of chitosan was observed by FT-IR, TGA, DSC and XRD analysis. Saran-chitosan hydrogels showed high water content (98 ~ 99 %), which is superior to that of conventional sacran gels. Water content of hydrogels was highest in the order of DW > NaCl > CaCl<sub>2</sub> solution and tended to decrease as the concentration of NaCl and CaCl<sub>2</sub> increased. This result can be explained that salt addition broke the nanoloops of sacran network, which retained water molecules, and caused decrease of retention capacity of hydrogels.