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카메라, UWB, IMU, 엔코더의 데이터 융합을 이용한 야외 로봇을 위한 험지 SLAM
김철홍,김지성,조동일 제어로봇시스템학회 2021 제어로봇시스템학회 국내학술대회 논문집 Vol.2021 No.6
This paper develops a harsh-environment simultaneous localization and mapping (SLAM) method for field robots using the data fusion of various sensors, such as a camera, ultra-wideband (UWB), inertial measurement unit (IMU), and encoders. Localization errors in harsh environments are mostly caused by the translation error due to the wheel slip and the orientation error due to the uneven ground. These errors can be improved using single-sensor based localization methods such as visual SLAM or UWB. However, these methods have disadvantages in field robots for the following reasons. The performance of visual SLAM is dependent on the number of landmarks or the depth of landmarks. In UWB localization, many UWB transmitters are required to cover a large area. This paper develops multiple-sensors based SLAM for field robots to overcome these shortcomings. The sensors considered for data fusion are a camera, UWB, IMU, and encoders. The initial starting position of the field robots is set by the IMU and encoders, and stored as the reference. Translation errors of the initial position are reduced by the data fusion of a camera and UWB, and the orientation errors of the initial position are reduced by the data fusion of a camera and IMU. The performance of the proposed method is demonstrated using dataset-based experiments.
김철홍,김정구,박건호 한국생체재료학회 2005 생체재료학회지 Vol.9 No.2
To alleviate fixation-related problems that are associated with cemented total hip arthroplasty (THA), the ingrowth of bone into the mantle of porous bone cement was investigated as a means to promote attachment between the host bone and the implanted cement. We co-polymerized poly methyl methacrylate (PMMA) and poly(L-lactic acid) (PLLA) by introducing an unsaturated alkene (vinyl) group into the PLLA, and the powdered vinyl–PLLA (v-PLLA) was co-polymerized with liquid methyl methacrylate (MMA) to form biodegradable bone cement. Biodegradation of the bone cement was simulated by prolonged immersion in phosphate-buffered saline (pH 7.4). Degradation of cement specimens that contained v-PLLA was slower than cement that contained only unmodified PLLA. This result indicated that the initial fixation period of the v-PLLA-containing bone cement was sufficiently long to allow for the ingrowth of bone into the cement mantle, which was confirmed by scanning electron microscopic examination of v-PLLA-containing bone cement that was implanted into the femurs of rabbits. We conclude that the biomechanical properties of v-PLLA-containing bone cement make this material suitable for clinical applications such as THA.
국내 지하철 정비 사업장의 근골격계질환 실태조사에 관한 연구
김철홍,권영준,백승렬,손경일,Kim, Cheol-Hong,Gwon, Yeong-Jun,Baek, Seung-Ryeol,Son, Gyeong-Il 대한인간공학회 2004 大韓人間工學會誌 Vol.23 No.3
A research project was conducted to study work-related musculoskeletal disorders (MSDs) at subway train repair plant in Korea. The project was consisted of 4 main parts; education on the topics of MSDs for all workers, symptom survey, medical check-up, investigation of MSD risk factors. The result of symptom survey showed that 95.2% of the respondents complained pains on at least one part of the body. After cross-sectional analysis of various information and risk factors, 86.8% of respondents were considered as active health surveillance level 1 that require continuous monitoring on their symptoms and working conditions. And 57.1% of the respondents were considered as active health surveillance level 2 that needed medical check-ups for proper medical treatment. The analysis of occupational risk factors revealed that handling of heavy object (46.15%) and repeated awkward postures (46.15%) were two most contributing risk factors for the on-set of MSD at this work site followed by static strain (7.7%), and vibration and impact (3.8%). Medical examination was performed by an industrial medicine MD on 156 workers those considered as active health surveillance level 2. The result showed that 35 workers (20.7%) were considered as MSD patient group at severe level, and 68.6 workers (68.6%) were considered as moderate group and 18 workers (10.6%) were considered minor or normal group those have no symptom.