• 제어로봇시스템학회논문지
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• 제22권9호
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• pp.723-732
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• 2016

This paper proposes an approach to fused navigation of an unmanned surface vehicle(USV) and to detection of the outlier or interference of global positioning system(GPS). The method fuses available sensor measurements through extended Kalman filter(EKF) to find the location and attitude of the USV. The method uses error covariance of EKF for detection of GPS outlier or interference. When outlier or interference of the GPS is detected, the method excludes GPS data from navigation process. The measurements to be fused for the navigation are GPS, acceleration, angular rate, magnetic field, linear velocity, range and bearing to acoustic beacons. The method is tested through simulated data and measurement data produced through ground navigation. The results show that the method detects GPS outlier or interference as well as the GPS recovery, which frees navigation from the problem of GPS abnormality.

• Journal of Astronomy and Space Sciences
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• 제35권4호
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• pp.287-293
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• 2018

This paper presents a satellite relative navigation strategy for formation flying, which chooses an appropriate navigation algorithm according to the operating environment. Not only global positioning system (GPS) measurements, but laser measurements can also be utilized to determine the relative positions of satellites. Laser data is used solely or together with GPS measurements. Numerical simulations were conducted to compare the relative navigation algorithm using only laser data and laser data combined with GPS data. If an accurate direction of laser pointing is estimated, the relative position of satellites can be determined using only laser measurements. If not, the combined algorithm has better performance, and is irrelevant to the precision of the relative angle data between two satellites in spherical coordinates. Within 10 km relative distance between satellites, relative navigation using double difference GPS data makes more precise relative position estimation results. If the simulation results are applied to the relative navigation strategy, the proper algorithm can be chosen, and the relative position of satellites can be estimated precisely in changing mission environments.

• 한국항공우주학회지
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• 제46권7호
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• pp.592-601
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• 2018

군용항공기에 장착되는 전자 장비 중 하나인 항공장착물 GPS/INS 통합항법장치는 투하전에는 항공기 날개에 가려 GPS 위성 신호의 직접적인 수신이 불가능하므로 항공기로부터 GPS 항법 데이터를 전달 받아 필터 통합에 이용하고, 투하 후에는 안테나를 통해 직접 수신한 GPS 정보를 이용하여 통합 항법을 수행한다. 이때, 무선을 이용하여 GPS 항법데이터를 전송할 경우 항공기의 별다른 개조 없이 구형 항공기에서도 운용이 가능하다. 그러나 항공기의 항법데이터가 무선을 통해 장착물의 통합항법필터에 전달되기까지 지연이 발생하게 되며, 이는 GPS 측정치와 INS 정보의 시각동기에 영향을 미쳐 통합항법 성능에 영향을 미치게 된다. 이에 본 논문에서는 무선을 통하여 GPS 데이터를 수신하는 항공장착물의 GPS/INS 통합항법시스템을 구현할 때 발생할 수 있는 생성 및 전송지연의 영향을 분석하고 이를 보상하는 알고리즘을 제안하였다.

• Journal of Astronomy and Space Sciences
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• 제23권3호
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• pp.259-268
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• 2006

우주 공간에서 GPS 수신기의 사용은 지구저궤도에서 일반화가 되었다. 최근 대부분의 위성은 위성 위치를 찾기 위한 항법 해로써 GPS 수신기를 사용한다. 그러나, GPS 수신기로부터 직접 획득한 항법 해의 정확도는 지도 제작과 같은 위성 활용에서 충분하지가 않다. 정밀궤도결정과 같은 후처리 개념이 위성 위치 정확도를 향상시키기 위해서 위성 자료 처리에 최근 적용되고 있다. 정밀궤도결정은 GPS 수신기의 항법 해가 아닌 원시 측정 자료를 사용한다. 원시 측정 자료의 성능은 GPS 수신기의 원시 측정 자료 정확도 및 추적 루프 알고리듬에 의해서 결정된다. 이 논문에서는 원시 측정 자료의 성능을 평가할 수 있는 기법을 제안하였다. GPS 수신기의 항법 해와 정밀궤도결정의 항법 해를 얻기 위한 지구저궤도위성의 시험 환경 및 절차를 기술하였다. 추가로, GPS수신기의 항법 해, 원시 측정 자료, 정밀궤도결정의 항법 해에 대한 정확도를 분석하였다. 제안된 기법은 일반적인 저궤도 위성에 적용 가능하다.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2006년도 International Symposium on GPS/GNSS Vol.1
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• pp.337-342
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• 2006

The use of GPS receiver at outer space becomes common in low earth orbit. The KOrea Multi-Purpose SATellite-1 (KOMPSAT-1) which was launched in December 1999 has used GPS receiver's navigation solution to perform the Orbit Determination (OD) in the ground. At the circumstance of using only one ground station, the Orbit Determination using GPS receiver is good method. Because the accuracy of navigation solution acquiring directly from GPS receiver is not enough in satellite application such as map generation, post-processing concepts such as the Precise Orbit Determination (POD) are applied to satellite data processing to improve satellite position accuracy. The POD uses GPS receiver's raw measurement data instead of GPS receiver's navigation solution. The KOrea Multi- Purpose SATellite-2 (KOMPSAT-2) system newly uses the POD technique for large scale map generation. The satellite was launched in the end of July 2006. The satellite sends high resolution images in panchromatic band and multi-spectral bands to the ground. The satellite system uses GPS receivers as source of time synchronization and command reference in the satellite, provider of navigation solution for the OD, and provider of raw measurement data for the POD. In this paper, mechanical configuration and operations of the GPS receiver will be presented. The GPS data characteristics of the satellite such as time synchronization, command reference, the OD using GPS receiver's navigation solution, and the POD using GPS receiver's raw measurement data will be presented and analyzed. The enhancement of performance compared with it of the previous satellite will also be analyzed.

• 전기학회논문지
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• 제66권9호
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• pp.1409-1415
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• 2017

The navigation and EDR(Event Data Recorder) have a different roles but also a lot of similar or common functions and elements. A representative element is a GPS. The GPS of navigation is a more higher than the that of EDR in performance. The high performance GPS has a very short initialization time and more accurate than the GPS of EDR. And the informations of OBD(On Board Diagnostics) is able to be shared in navigation and EDR. But these inter-working product between the navigation and EDR has been not yet shown. So, this paper is aimed to show how to interwork in two devices. We utilize USB bulk communication in two devices for inter-working. It is very simple ways and it could interwork in GPS, event video and ODB II data. It could be effective in cost competence and convenience. These was implemented by hardware and software and proved by the standard test.

• Journal of Astronomy and Space Sciences
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• 제22권3호
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• pp.243-248
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• 2005

NORAD Two Line Element (TLE) is very useful to simplify the ground station antenna pointing and mission operations. When a satellite operations facility has the capability to determine NORAD type TLE which is independent of NORAD, it is important to analyze the applicable tracking data arcs for obtaining the best possible orbit. The applicable tracking data arcs for NORAD independent TLE orbit determination of the KOMPSAT-1 using GPS navigation solutions was analyzed for the best possible orbit determination and propagation results. Data spans of the GPS navigation solutions from 1 day to 5 days were used for TLE orbit determination and the results were used as Initial orbit for SGP4 orbit propagation. The operational orbit determination results using KOMPSAT-1 Mission Analysis and Planning System(MAPS) were used as references for the comparisons. The best-matched orbit determination was obtained when 3 days of GPS navigation solutions were used. The resulting 4 days of orbit propagation results were within 2 km of the KOMPSAI-1 MAPS results.

• 한국군사과학기술학회지
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• 제2권2호
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• pp.186-196
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• 1999

The CPS provides data with long-term stability independent of passed time and the INS provides high-rate data with short-term stability. By integrating these complementary systems, a highly accurate navigation system can be achieved. In this paper, a loosely-coupled GPS/INS integration system is designed. It is a simple structure and is easy to implement and preserves independent navigation capability of GPS and INS. The integration system consists of a NCU, an IMU, a GPS receiver, and a monitoring system. The navigation algorithm in the NCU is designed under the multi-tasking environment based on a real-time kernel system and the monitoring system is designed using the Visual C++. The integrated Kalman filter is designed as a feedback formed 15-state filter, in which the states are position errors, velocity errors, attitude errors and sensor bias errors. The van test result shows that the integrated system provides more accurate navigation solution then the inertial or the GPS-alone navigation system.

• Journal of Astronomy and Space Sciences
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• 제33권1호
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• pp.45-54
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• 2016

This study developed an approach for improving Carrier-phase Differential Global Positioning System (CDGPS) based realtime satellite relative navigation by applying laser baseline measurement data. The robustness against the space operational environment was considered, and a Synthetic Wavelength Interferometer (SWI) algorithm based on a femtosecond laser measurement model was developed. The phase differences between two laser wavelengths were combined to measure precise distance. Generated laser data were used to improve estimation accuracy for the float ambiguity of CDGPS data. Relative navigation simulations in real-time were performed using the extended Kalman filter algorithm. The GPS and laser-combined relative navigation accuracy was compared with GPS-only relative navigation solutions to determine the impact of laser data on relative navigation. In numerical simulations, the success rate of integer ambiguity resolution increased when laser data was added to GPS data. The relative navigational errors also improved five-fold and two-fold, relative to the GPS-only error, for 250 m and 5 km initial relative distances, respectively. The methodology developed in this study is suitable for application to future satellite formation-flying missions.

• 한국항해학회지
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• 제24권4호
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• pp.219-226
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• 2000

Ship's position data obtaining method is one of the very important factor in navigation. Nowadays, GPS(Global Positioning System) using the earth orbiting satellites are equipped and operated for the position finding. Because it provides more precise position information than other equipments and is very convenient for navigator. In this study, it is designed to develop the GPS simulator for everybody being able to practise the GPS operating skill like as navigation planning, navigation calculating etc. And also, it can be operated with personal computer without real GPS receiver. This simulation system is based on the real GPS receiver and built by the visual basic 5.0 program. And it displays the ship's position and navigating information and plots the ship's moving track on the screen in real time according as initial setup data-main engine's rpm, rudder angle, departure position and waypoint.