• 제어로봇시스템학회논문지
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• 제21권5호
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• pp.490-495
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• 2015

As flying robots are becoming popular, there are increased needs to use themforsuch purposes as parcel delivery, serving in restaurants, and stage performances. To control flying robots such as quad copters, localization is essential. In order to properly position flying robots, many techniques are in development, including IR (infra-red)-based systemswhich catch markers on a flying robot in order that it can position itself. However, this technique demonstrates only short coverage. Furthermore, localization from inertial sensors diverges as time passes. For this reason, this paper suggests a TWR (two-way ranging) based positioning technique. Despite the weaknesses in currently available TWR system, this paper suggests a self-positioning and outlier detection technique in order to provide reliable position information with a faster update rate. The self-positioning system sends a shorter message which reduces wireless traffic. By detecting and removing outlier measurements, a positioning result with better accuracy is acquired. Finally, this paper shows that the suggesting system detects outlierssequentially from less than half the number of anchors in localization system according to the degree of outlier in measurement and the noise level. By performing an outlier algorithm, better positioning accuracy is acquired as shown in the experimental result.

• 로봇학회논문지
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• 제8권2호
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• pp.129-135
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• 2013

In this paper, a high precision outdoor positioning system is newly proposed using multiple GPS receivers based on the Extended Kalman Filter (EKF). Typically, the GPS signal has the instantaneous errors that degrade the positioning seriously. Using the multiple GPS receivers instead of an expensive DGPS receiver, the positioning reliability and accuracy are improved in this research as a low cost solution. To incorporate the small displacement, an INS data have been tightly coupled to the GPS data, which has the inherit disadvantage of the cumulative error occurring over time. To achieve a stabilized and accurate positioning system, the multiple GPS receiver data are fused with the INS data through the EKF process. Through real navigation experiments of an outdoor mobile robot, the performance of the proposed system has been verified to be accurate comparable to DGPS system with a lower cost.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제13권1호
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• pp.69-85
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• 2019

BeiDou navigation satellite system (BDS) is one of the four main types of global navigation satellite systems. The current system has been widely used by the military and by the aerospace, transportation, and marine fields, among others. However, challenges still remain in the BeiDou system, which requires rapid responses for delay-sensitive devices. A differential positioning algorithm called the data center-based differential positioning (DCDP) method is widely used to avoid the influence of errors. In this method, the positioning information of multiple base stations is uploaded to the data center, and the positioning errors are calculated uniformly by the data center based on the minimum variance or a weighted average algorithm. However, the DCDP method has high delay and overload risk. To solve these problems, this paper introduces edge computing to relieve pressure on the data center. Instead of transmitting the positioning information to the data center, a novel method called edge computing-based differential positioning (ECDP) chooses the nearest reference station to perform edge computing and transmits the difference value to the mobile receiver directly. Simulation results and experiments demonstrate that the performance of the ECDP outperforms that of the DCDP method. The delay of the ECDP method is about 500ms less than that of the DCDP method. Moreover, in the range of allowable burst error, the median of the positioning accuracy of the ECDP method is 0.7923m while that of the DCDP method is 0.8028m.

• 한국정밀공학회지
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• 제25권10호
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• pp.122-129
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• 2008

This paper deals with precise positioning of a high-speed positioning stage without inducing residual vibration by using an input shaping technique. Input shaping is well known to be a very effective tool for suppressing the residual vibration of flexible structures. However, the ordinary input shaping for positioning stages is designated mostly for velocity regulation, not for the residual vibration at the target position. The main difficulties in implementing input shaping along with precise positioning are the time delay caused by the servo system characteristics and the s-curve feature often employed in some motor controllers. This paper analyzes the dynamic responses of a single-mode-dominate stage system subjected to input shaping. A theoretical model is developed io investigate the nature of system. In order to overcome the difficulty, this paper proposes an improved input shaper based on modified command profile generation. The proposed method is proved effective through experiments and simulations.

• 한국측량학회지
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• 제32권6호
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• pp.599-606
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• 2014

Since the accuracy of Global Positioning System (GPS)-based vehicle positioning system is significantly degraded or does not work appropriately in the urban canyon, the integration techniques of GPS with Inertial Navigation System (INS) have intensively been developed to improve the continuity and reliability of positioning. However, its accuracy is degraded as INS errors are not properly corrected due to the GPS signal blockage. Recently, the image-based positioning techniques have been started to apply for the vehicle positioning for the advanced in processing techniques as well as the increased the number of cars installing the camera. In this study, Single Photo Resection (SPR), which calculates the camera exterior orientation parameters using the Ground Control Points (GCPs,) has been integrated with the INS/GPS for continuous and stable positioning. The INS/GPS/SPR integration was implemented in both of a loosely and a tightly coupled modes, based on the Extended Kalman Filter (EKF). In order to analyze the performance of INS/SPR integration during the GPS outage, the simulation tests were conducted with a consideration of factors affecting SPR performance. The results demonstrate that the accuracy of INS/SPR integration is depended on magnitudes of the GCP errors and SPR processing intervals. Additionally, the simulation results suggest some required conditions to achieve accurate and continuous positioning, used the INS/SPR integration.

• Journal of Positioning, Navigation, and Timing
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• 제6권3호
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• pp.95-104
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• 2017

Positioning signals transmitted by Global Positioning System (GPS) satellites located at approximately 20,000 km height is very weak. For the reason, GPS signals are vulnerable to intentional jamming and unintentional disturbance. Recently, the number of jamming has been increased significantly all over the world. For the applications where continuous and reliable positioning is required when GPS jammers are activated, other positioning systems are strongly required. In this work, a set of Time Division Multiple Access (TDMA)-based transmitters and receivers utilizing Universal Software Radio Peripheral (USRP) and GNU Radio are designed and implemented. To eliminate the undesirable effects of GPS jamming, a frequency band which does not overlap L band is utilized. To demonstrate the accuracy of the proposed method, an experiment was performed.

• 한국통신학회논문지
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• 제35권1C호
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• pp.130-137
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• 2010

본 논문에서는 상향 실내음향측위를 위한 자체발성음으로서 휘파람소리, 손가락딱소리, 박수소리의 시간 및 주파수영역, 상관 및 전력스펙트럼밀도, 최대지연시간, 최대주파수, 대역폭 분석을 통해 여러 자체발성음의 측위음원으로서의 적합성을 판단한다. 그리고 자체발성음의 도달지연시간차에 기반을 둔 실내측위시스템을 설계하고 그 성능을 평가한다. 자체발성음 분석과 측위성능평가를 위해 여성과 남성 각 50명씩, 총 100명의 자체발성음 데이터베이스를 구축해 활용하였다.

• 한국지리정보학회지
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• 제6권4호
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• pp.51-58
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• 2003

GPS를 대표로 하는 위성측위시스템은 GIS 데이터베이스 구축을 위한 데이터 취득에 있어서 중요한 역할을 하고 있다. 또한 최근의 위성측위 기술의 발전은 보다 빠르고 쉽고 경제적인 방법으로 대상물의 정확한 위치 정보의 취득을 가능하게 하였다. 그러나 도시공간 환경에 있어서는 수많은 도시공간 구조물들로 인해 측위위성과 수신기 사이의 시통이 제한됨으로써 정확한 GIS 데이터베이스 구축에 필요한 신뢰성 있는 위치정보 취득이 곤란하게 된다. 또한 대부분의 GIS 데이터 생성과 갱신의 소요가 도시공간을 중심으로 이루어지고 있음을 고려할 때, 이와 같은 도시공간에서의 위성측위를 통한 위치정보 취득의 곤란은, 정확하고 신속함을 필요로 하는 GIS 데이터 취득에 심각한 문제를 야기하게 된다. 따라서, 본 연구에서는 실제 도시공간에의 위치정보 취득을 위한 위성측위 환경을 평가하기 위해 차량측정장치를 사용하여 실제 도시공간을 대상으로 현장 실험을 수행하였다. 본 연구를 통하여 기존의 GPS 만을 이용한 위성측위 방식에서는 위치정보 데이터 취득에 한계성이 있다는 것을 파악할 수 있었으며, 이 결과는 향후 새로운 보완 측위 기술 연구분야에서 유용한 기초자료로서 활용될 수 있을 것으로 사료된다.

• 한국정보통신학회논문지
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• 제21권10호
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• pp.1917-1922
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• 2017

WPS는 현실세계에 산재한 무선 신호를 활용하여 측위를 수행한다. 측위 위치의 무선 신호 정보를 수집하여 radio map을 구성하는 구축단계, 구성된 정보와 수집된 무선 신호를 비교하는 측위 단계로 나누어진다. WPS는 측위 시 수집된 신호에 변화가 나타날 경우 측위 정확도의 하락을 가지고 온다. PDR은 관성 센서들을 활용하여 보행자의 걸음걸이 수, 이동거리, 방향을 분석하여 최종 이동지를 분석하는 시스템이다. WPS의 측위 결과가 두 개 이상의 위치로 나타날 경우 측위 정확도의 문제로 판단할 수 있다. 몇몇의 조건에서 문제가 발생하게 된다. 본 논문에서는 앞서 언급한 문제점이 발생하는 상황에 대하여 분석하고 이를 PDR을 통해서 보정하는 시스템에 대하여 제안한다. 이 복합측위를 적용할 경우 WPS에 문제가 발생할 경우에도 측위 정확도를 유지하거나 향상 시킬 수 있을 것으로 사료된다.

• International Journal of Precision Engineering and Manufacturing
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• 제8권2호
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• pp.32-37
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• 2007

This paper proposes a dual-mode ultra precision positioning system for machine tools and measuring machines. The objective was to position a machine table with a picometer order of resolution, i.e., pico-positioning. A twist-roller friction drive (TFD) was used in coarse-mode positioning. The TFD, which was driven by an AC servomotor, is a kind of lead screw in mechanical terms, and several centimeters of machine table movement was controlled with a nanometer order of positioning resolution. To eliminate lateral vibration caused by the TFD, an active aerostatic coupling driven by piezoelectric actuators was inserted between the TFD and the machine table. This active aerostatic coupling was also applied as a feed drive device for fine-mode positioning; in the fine mode, the positioning resolution was 50 pm. Factors influencing pico-positioning, such as how noise from displacement sensors and vibrations in the aerostatic guideway affect positioning resolution, are discussed.