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Monitoring QZSS CLAS-based VRS-RTK Positioning Performance
Cheolsoon Lim,Yebin Lee,Yunho Cha,Byungwoon Park,Sul-Gee Park,Sanghyun Park 사단법인 항법시스템학회 2022 Journal of Positioning, Navigation, and Timing Vol.11 No.4
The Centimeter Level Augmentation Service (CLAS) is the Precise Point Positioning (PPP) – Real Time Kinematic (RTK) correction service utilizing the Quasi-Zenith Satellite System (QZSS) L6 (1278.65 MHz) signal to broadcast the Global Navigation Satellite System (GNSS) error corrections. Compact State-Space Representation (CSSR) corrections for mitigating GNSS measurement error sources such as satellite orbit, clock, code and phase biases, tropospheric error, ionospheric error are estimated from the ground segment of QZSS CLAS using the code and carrier-phase measurements collected in the Japan’s GNSS Earth Observation Network (GEONET). Since the CLAS service begun on November 1, 2018, users with dedicated receivers can perform cm-level precise positioning using CSSR corrections. In this paper, CLAS-based VRS-RTK performance evaluation was performed using Global Positioning System (GPS) observables collected from the refence station, TSK2, located in Japan. As a result of performing GPS-only RTK positioning using the open-source software CLASLIB and RTKLIB, it took about 15 minutes to resolve the carrier-phase ambiguities, and the RTK fix rate was only about 41%. Also, the Root Mean Squares (RMS) values of position errors (fixed only) are about 4cm horizontally and 7 cm vertically.
파티션 비트맵을 이용한 메모리 효율적인 리눅스 파티션 스케줄러
권철순(Cheolsoon Kwon),조현우(Hyunwoo Joe),김덕수(Duksoo Kim),김형신(Hyungshin Kim) 한국정보과학회 2014 정보과학회 컴퓨팅의 실제 논문지 Vol.20 No.9
독립적인 전자 장비들을 모듈화하여 하나로 통합한 시스템에 탑재되는 운영체제는 안정성 보장을 위해 파티셔닝 기술을 갖추어야 한다. 기존 운영체제에 파티셔닝 기술을 접목하기 위해서는 기존 스케줄러를 파티션 스케줄러로 확장해야한다. 특히 낮은 성능과 적은 메모리를 사용하는 우주용 시스템과 같은 임베디드 시스템에 적용하기 위해서는 스케줄러 확장시 성능적인 측면뿐만 아니라 메모리적인 측면도 고려해야한다. 본 논문에서는 파티션 비트맵을 이용한 메모리 효율적인 리눅스 파티션 스케줄러를 제안한다. 제안한 파티션 스케줄러는 구현시 적은 양의 메모리 공간을 요구하며 적은 파티션 전환 오버헤드가 발생한다. 또한 프로토타입을 LEON 4 프로세서 보드에 구현하였다. 성능평가를 통해 결과 정확성과 파티션 전환 오버헤드, 그리고 구현시 요구되는 메모리 공간 및 추가되는 소스코드의 양을 확인하였다. The operating systems in the system architecture, which is integrated several applications and modular electronic devices in the same computing device, demand partitioning technology for safety. Thus, operation system requires partition scheduler for partition scheduling. When we design partition scheduler in embedded system, which has small memory and low performance, such as space system, we must consider not only performance but also memory. In this paper, we introduces a linux-based memory efficient partition scheduler using partition bitmap. This partition scheduler demands small memory space and produce low partition switching overhead. The prototype was executed on a LEON4 processor, which is the Next Generation Multicore Processor (NGMP) in the space sector. In evaluation, this prototype shows accuracy, additional memory space and low partition switching overhead.
불순물에 의한 유압저하를 고려한 스트레이너 설계 수법 개발
김철순(Cheolsoon Kim),송호성(Hosung Song),최종윤(Jongyun Choi),박정일(Jungil Park),김민철(Mincheol Kim) 한국자동차공학회 2019 한국자동차공학회 학술대회 및 전시회 Vol.2019 No.11
In the transmission, ATF is supplied to the oil pump through the strainer, and the hydraulic pressure generated from the oil pump is supplied to each component of the transmission through the control valve. The strainer serves to maintain the suction performance of fluid and functions as a filter that captures contamination from the inside of transmission. In order to maintain these two functions, the strainer is designed in consideration of the position of the inlet and the pressure loss generated inside the strainer. Currently, pressure loss after contamination capture depends on experimentation. In this study, we developed a strainer design method that can predict hydraulic pressure drop due to contamination accumulation. The model which improved the inhalation performance of the strainer using this method was proposed and compared with the experiment, the validity was confirmed.
기선 거리에 따른 VRS와 FKP 방식의 Network RTK 사용자 성능 비교
임철순 ( Cheolsoon Lim ),박병운 ( Byungwoon Park ) 한국항행학회 2020 韓國航行學會論文誌 Vol.24 No.6
본 논문에서는 기선 거리에 따른 VRS (virtual reference station)와 FKP (flächen korrektur parameter) 방식의 Network RTK (real time kinematics) 사용자 성능을 비교 분석하였다. 이를 위해 현재 국토지리정보원에서 운영 중인 VRS 및 FKP 서비스를 통해 기선 거리 별 보정정보를 취득하여 상용 수신기에 적용한 후, RTK 수행 결과를 측정치 영역과 위치 영역에서 각각 분석하였다. VRS의 경우, 사용자가 기선 거리가 증가함에 따라 발생하는 공간이격 오차를 보상하지 못하므로 전반적인 RTK 성능이 저하되는 것을 확인하였다. 반면, FKP는 VRS와 달리 전리층 및 비전리층 오차의 구배를 이용하여 사용자와 기준국 간 측정치의 공간이격 오차를 보상하므로 기선 거리 약 130 km 수준까지는 기선 거리 증가하더라도 VRS에 비해 안정적인 RTK 성능을 보여주었지만, 150 km이상의 장기저선의 경우에는 FKP 보정정보의 성능 감소로 인해 미지정수 오결정 등의 문제가 발생하였다. In this paper, the performances of virtual reference station (VRS) and flächen korrektur parameter (FKP) based Network real time kinematics (RTK) according to baseline length were compared and analyzed. We applied the VRS and FKP corrections for each baseline length obtained from National Geographic Information Institute Network RTK services to an FKP-supported commercial receiver and analyzed the RTK results in the range and position domains. In the case of VRS, RTK performance was degraded due to the spatial error, which increase in proportion of the baseline length. On the other hand, FKP compensates for spatial errors by using the gradients of dispersive and non-dispersive errors, so it showed stable RTK performance compared to VRS even if the baseline length increases up to 130 km. However, in the case of long baseline of 150 km or more, integer ambiguities were incorrectly fixed due to the decrease in the performance of the FKP corrections.
김철순(Cheolsoon Kim),정길조(Giljo Jung),박진수(Jinsu Park),최종윤(Jongyun Choi),최윤석(Yoonseok Choi) 한국자동차공학회 2016 한국자동차공학회 학술대회 및 전시회 Vol.2016 No.11
Recently, exhaust emission regulation have become more stringent as a result of increased environmental issue and high-fuel-efficient vehicles are needed from customers. As one of the solutions, adoption of idle stop device has been increasing on vehicle. In case of the idle stop device with electric oil pump, it is needed to minimize the time delay by rapidly raising hydraulic pressure. In this study, considering shape of the hydraulic circuit in sub control valve, the method using CFD was developed to improve the hydraulic response for idle stop device with electric oil pump. Through this method, it could predict the location and size of the air pocket, and confirmed that the air pocket cause the delay of hydraulic pressure increase. As a result, it is possible to propose the sub control valve which is minimized the delay of hydraulic pressure.