• 로봇학회논문지
• /
• 제19권1호
• /
• pp.23-30
• /
• 2024

This paper studies a GPS error filtering method that takes into account the continuity of the ongoing path to enhance the safety of autonomous agricultural mobile robots. Real-Time Kinematic Global Positioning System (RTK-GPS) is increasingly utilized for robot position evaluation in outdoor environments due to its significantly higher reliability compared to conventional GPS systems. However, in orchard environments, the robot's current position obtained from RTK-GPS information can become unstable due to unknown disturbances like orchard canopies. This problem can potentially lead to navigation errors and path deviations during the robot's movement. These issues can be resolved by filtering out GPS information that deviates from the continuity of the waypoints traversed, based on the robot's assessment of its current path. The contributions of this paper is as follows. 1) The method based on the previous waypoints of the traveled path to determine the current position and trajectory. 2) GPS filtering method based on deviations from the determined path. 3) Finally, verification of the navigation errors between the method applying the error filter and the method not applying the error filter.

• 제어로봇시스템학회논문지
• /
• 제6권11호
• /
• pp.1039-1044
• /
• 2000

In this paper, the error caused by the measurement delay in INS/GPS integrated systems with Kalman filtering is defined and analyzed through the analytical method and the simulation. It is proved that the error of measurement delay causes not only the position error but also the estimate error of the x-axis accelerometer bias when a vehicle turns. And the estimation method of the delay time and the compensation method using an extrapolation method are presented. The performance of the compensation method is shown by the analytic method and the simulation.

• International Journal of Aeronautical and Space Sciences
• /
• 제13권4호
• /
• pp.499-506
• /
• 2012

In this paper, a dynamic modeling for the velocity and position information of a single frequency stand-alone GPS(Global Positioning System) receiver is described. In static condition, the position error dynamic model is identified as a first/second order transfer function, and the velocity error model is identified as a band-limited Gaussian white noise via non-parametric method of a PSD(Power Spectrum Density) estimation in continuous time domain. A Kalman filter is proposed considering both correlated/white measurements noise based on identified GPS error model. The performance of the proposed Kalman filtering method is verified via numerical simulation.

• 제어로봇시스템학회논문지
• /
• 제14권8호
• /
• pp.727-732
• /
• 2008

In this paper, the state-space representation of generalized complimentary filter is proposed. Complementary filter has the suitable structure to merge information from sensors whose frequency regions are complementary. First, the basic concept and structure of complementary filter is introduced. And then the structure of the generalized filter and its state-space representation are proposed. The state-space representation of complementary filter is able to design the complementary filter by applying modern filtering techniques like Kalman filter and $H_{\infty}$ filter. To show the usability of the proposed state-space representation, the design of Inertial Navigation System(INS) vertical channel damping loop using Global Positioning System(GPS) is described. The proposed GPS/INS damping loop lends the structure of Baro/INS(Barometer/INS) vertical channel damping loop that is an application of complementary filter. GPS altitude error has the non-stationary statistics although GPS offers navigation information which is insensitive to time and place. Therefore, $H_{\infty}$ filtering technique is selected for adding robustness to the loop. First, the state-space representation of GPS/INS damping loop is acquired. And next the weighted $H_{\infty}$ norm proposed in order to suitably consider characteristics of sensor errors is used for getting filter gains. Simulation results show that the proposed filter provides better performance than the conventional vertical channel loop design schemes even when error statistics are unknown.

• 제어로봇시스템학회논문지
• /
• 제7권12호
• /
• pp.1015-1023
• /
• 2001

error behaviour can be considered as a linear combination of low amplitude random noise and abrupt jumps. The reason of jump appearance can be explained by the semi-shading effects(buildings, trees), jamming, high dynamic of vehicle and so on. This study describes the stand-alone GPS error jump smoothing algorithm which is developed based on the scalar adaptive filter. The algorithm consists of the coarse jump smoothing and the fine jump smoothing. On the coarse smoothing step, GPS velocities or position differences are used as the measurement for the scalar adaptive filter. The purpose of adaptive filter is to smooth the jump errors. The coarse positions are detennined by the integration of smoothed velocities. On the fine smoothing step, the differences between GPS positions and the coarse positions are smoothed by another scalar adaptive filter. The reason of fine smoothing is based on the facts that smoothing accuracy depends on the variance ofusefuJ signa\. The coarse smoothing which deal with the difference of positions provides the rough error removing. So the coarse smoothed velocities can have much more low amplitude than the raw ones. The fine smoothing procedure provides high quality of filtering process. Simulation results show the efficiency of proposed scheme.

• 제어로봇시스템학회:학술대회논문집
• /
• 제어로봇시스템학회 2004년도 ICCAS
• /
• pp.1949-1952
• /
• 2004

GPS is widely used for outdoor positioning in many applications. But it is not suitable for positioning in an obstacle environment such as urban area, tunnels and so on, due to variable signal level. So new technology of the positioning is required to provide the consistent error level regardless of any changes in any environment. Abrupt changes of GPS signal can be detected by various fault detection and isolation methods. Conventional FDI (Fault Detection and Isolation) methods are categorized into two approaches. One approach is the snapshot method that uses measurements only at present step. The other approach is the filtering method that uses measurements stacked from previous step to present step. The FDI result of the snapshot method can be considered reliable independently with previous results and the FDI result of the filtering method is more reliable and detection time is a little longer. Therefore combining approach of two methods is proposed for increasing FDI performance in this paper. Three approaches that are the snapshot method, the filtering method and the combining method are compared to show the probability of correct FDI in simulations. The combining approach presents best result of FDI among them and shows the consistent accuracy irrespective of any changes in outdoor environment.

• 제어로봇시스템학회:학술대회논문집
• /
• 제어로봇시스템학회 2003년도 ICCAS
• /
• pp.984-989
• /
• 2003

The integrated global position system (GPS) and inertial navigation system (INS) has been considered as a cost-effective way of providing an accurate and reliable navigation system for civil and military system. Even the integration of a navigation sensor as a supporting device requires the development of non-traditional approaches and algorithms. The objective of this paper is to assess the feasibility of integrated with GPS and INS information, to provide the navigation capability for long term accuracy of the integrated system. Advanced algorithms are used to integrate the GPS and INS sensor data. That is fuzzy inference system based Weighted Extended Kalman Filter(FWEKF) algorithm INS signal corrections to provided an accurate navigation system of the integrated GPS and INS. Repeatedly, these include INS error, calculated platform corrections using GPS outputs, velocity corrections, position correction and error model estimation for prediction. Therefore, the paper introduces the newly developed technology which is aimed at achieving high accuracy results with integrated system. Finally, in this paper are given the results of simulation tests of the integrated system and the results show very good performance

• International Journal of Aeronautical and Space Sciences
• /
• 제2권1호
• /
• pp.67-77
• /
• 2001

In recent navigation system, the profitable solution is to integrate the GPS and Stapdwon INS (SDINS) system and its integration allows compensation for shortcomings of each system. This paper describes the hardware preparation and presents the test results obtained from the automobile test of the developed system. The automobile tests was conducted with two kinds of inertial sensors and GPS receivers : short range and middle range test, to verify and evaluate the performance of the integrated navigation system. The reference of position is given by the Differential GPS(DGPS) which has cm-level accuracy to compare the accuracy of system. Kalman filtering is used for integrating GPS and SDINS and this filter effectively allows the long-term stability of GPS to correct and decrease the time deviation error of SDINS.

• 대한전자공학회논문지TC
• /
• 제44권4호
• /
• pp.88-94
• /
• 2007

본 논문은 GPS 수신기에서 간섭 제거를 통한 성능 개선을 목적으로 3 차원 배열 안테나를 이용한 DOA ( Direction Of Arrival ) 추정과 빔 형성 성능 분석에 관한 것이다. GPS 수신기에 배열 안테나를 이용하면 신호 도래 방향의 DOA 를 추정한 후, 공간 필터링을 이용하여 원하는 방향으로 주빔과 널을 형성하므로서 재머 ( jammer ) 신호를 제거할 수 있으므로 시스템의 성능을 높힐 수 있게된다. 본 논문에서는 5 가지의 3 차원 배열 안테나 구조를 제안한 후 도래 신호의 DOA 를 추정키위한 MUSIC 알고리즘을 적용할 경우 추정 오차 및 빔 형성의 성능을 제시하였다. DOA 성능 분석을 위하여 DOA 추정 오차를 계산하였으며 빔 형성 성능 분석을 BER 을 사용하였다. 특히 빔 형성 성능 분석에서는 다양한 jammer 전력과 GPS 신호의 존재 및 각도 퍼짐등을 고려하였다. 컴퓨터 시뮬레이션의 결과 제안된 3차원 배열 안테나에서 Curved (B) 7-element 안테나가 DOA 추정, 추정 오차 및 BER 특성과 각도 퍼짐에서 다른 배열 안테나보다 우수한 특성을 얻을 수 있었다.

• 대한토목학회논문집
• /
• 제26권5D호
• /
• pp.731-738
• /
• 2006

교통 혼잡이 증가하면서, 경로에 대한 교통정보, 특히 실시간 구간통행시간에 대한 사람들의 관심이 증대되고 있다. 본 논문은 GPS Probe를 통해 구간통행시간을 산출했던 최기주(1998) 등의 후속 연구로써, 도시부에서 구간 통행시간을 산출하기 위해 택시를 GPS Probe로 활용하였다. 택시는 GPS Probe로 활용되기 위한 매우 좋은 수단이지만, 승객의 승하차시간 등 주행과 관계없는 불필요한 데이터가 포함되게 된다. 따라서 본 논문에서는 도시부에서 Taxi GPS를 통해 교통정보를 생성할 경우 주행과 관계없는 정보를 실시간으로 검지하여 제거하는 휴리스틱한 이상치 제거 알고리즘을 개발하였다. 평가를 위해 서울시 주요 간선축에서 번호판 조사를 실시하였으며 알고리즘을 적용한 통행시간과 비교하였다. 이상치 제거 알고리즘을 적용한 결과, 약 70%의 이상치가 제거되었으며, 실측 통행시간과의 상대 오차가 73.7%로 향상된 것으로 나타났다. 따라서 본 알고리즘을 이용할 경우 Taxi GPS를 통해 신뢰할 수 있는 실시간 교통정보를 생성할 수 있을 것으로 판단된다.