• 한국군사과학기술학회지
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• 제9권1호
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• pp.5-12
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• 2006

This study describes an SDINS/GPS/ZUPT integration algorithm for land navigation systems. The SDINS error can be decoupled in two parts. The first part is the the Schuler component which does not depend on object motion parameters, and the other is the Non-Schuler part which depends on the product of object acceleration and azimuth error. Azimuth error causes SDINS error in proportion to the traversed distance. The proposed system consists of a GPS/SDINS integration system and an SDINS/ZUPT integration system, which are both realized by an indirect feedforward Kalman filter. The main difference between the two is whether the estimate includes the Non-Schuler error or not, which is decided by the measurement type. Consequently, subtracting GPS/SDINS outputs from SDINS/ZUPT outputs provide the Non-Schuler error information which can be applied to improving azimuth accuracy. Simulation results using the raw data obtained from a van test attest that the proposed SDINS/GPS/ZUPT system is capable of providing azimuth improvement.

• 한국측량학회지
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• 제37권2호
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• pp.71-79
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• 2019

Geolocation accuracy is one of the important factors in utilizing all weather available SAR satellite imagery. In this study, an error budget analysis was performed on key variables affecting on geolocation accuracy by generating KOMPSAT-5 simulation data. To perform the analysis, a Range-Doppler model was applied as a geometric model of the SAR imagery. The results show that the geolocation errors in satellite position and velocity are linearly related to the biases in the azimuth and range direction. With 0.03cm/s satellite velocity biases, the simulated errors were up to 0.054 pixels and 0.0047 pixels in the azimuth and range direction, and it implies that the geolocation accuracy is sensitive in the azimuth direction. Moreover, while the clock drift causes a geolocation error in the azimuth direction, a signal delay causes in the range direction. Monte-Carlo simulation analysis was performed to analyze the influence of multiple geometric error sources, and the simulated error was up to 3.02 pixels in the azimuth direction.

• 전기학회논문지
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• 제68권1호
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• pp.108-121
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• 2019

This paper presents the study results on the design of the correction filter to improve the azimuth error estimation of the high-speed guided missile launched from the warship after the transfer alignment. We theoretically proved that the transfer alignment performance is determined by the accuracy of the marine inertial navigation system and the observability of the attitude error state variable in the transfer alignment filter, and that most of navigation errors in high-speed guided missile are caused by azimuth error. In order to improve the azimuth estimation performance of the correction filter, the multiple adaptive estimation method and the adaptive filters adapting the measurement noise covariance or the process noise covariance are proposed. The azimuth estimation performance of the proposed adaptive filter and the existing Kalman filter are compared and analyzed each other for 8 different transfer alignment accuracy cases. As a result of comparison and analysis, it was confirmed that the adaptive filter adapting the process noise covariance has the best azimuth estimation performance. These results can be applied to the design of correction filters for high-speed guided missile.

• 제어로봇시스템학회논문지
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• 제20권2호
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• pp.149-156
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• 2014

A magnetic compass module must be calibrated accurately before use. Moreover, the calibration process must be performed taking into account any magnetic dip if the magnetic compass module has tilt angles. For this, a calibration method for a magnetic compass module is explained. Tilt error of the magnetic compass module is compensated using a biaxial accelerometer generally. The accelerometer error causes a tilt angle calculation error that gives rise to an azimuth calculation error. For error property analysis, error equations are derived and simulations are performed. In the simulation results, the accuracy of derived error equations is verified. If a biaxial magnetic compass module is used instead of a triaxial one, the magnetic dip and z-axis magnetic compass data must be estimated for tilt compensation. Lastly, estimation equations for the magnetic dip and z-axis magnetic compass data are derived, and the performance of the equations is verified based on a simulation.

• 조명전기설비학회논문지
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• 제19권8호
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• pp.1-7
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• 2005

본 논문에서는 편광소자를 이용하는 스펙클패턴 전단간섭법(shearography)에서 각각 90도의 위상천이를 가지는 4개의 스펙클 패턴을 얻고, 이로부터 스펙클패턴의 각 지점에서의 위상을 얻을 수 있는 방법을 설명하고, 제안된 방법에 사용되는 파장판의 방위각에 의한 위상오차를 Jones 행렬을 이용하여 분석하였다.

• 한국인터넷방송통신학회논문지
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• 제22권6호
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• pp.137-141
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• 2022

지자기를 측정하여 방위각을 추정하는 방법은 매우 오래전부터 사용되어 왔다. 그러나 실내외의 금속 구조물 때문에 지자기에 외란이 발생하여 추정된 방위각에 오차가 발생하는 경우가 많다. 이를 보정하기 위한 연구가 많이 진행되어 왔지만 오차를 줄이는데 한계가 있다. 본 논문에서는 측정된 지자기 센서 값을 LSTM 구조의 신경망에 적용하여 방위각을 추정하는 방법을 제안한다. 신경망을 학습시키기 위해서는 데이터의 사전 처리가 매우 중요하며, 본 논문에서는 스마트폰에 내장된 가속도 센서와 자이로 센서, 지자기 센서를 이용하여 데이터를 수집하고, EKF를 사용하여 지자기 센서 값을 균등하게 샘플링하는 방법으로 학습 데이터를 생성하였다. 4개의 은닉층을 사용하여 평균 방위각 추정 오차가 0.9도인 결과를 얻었다.

• 대한전기학회논문지:시스템및제어부문D
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• 제51권6호
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• pp.221-227
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• 2002

In this paper, the system model for the compensation of the low-cost personal navigation system is derived and the error compensation method using GPS is also proposed. WNS(Walking Navigation System) is a kind of personal navigation system using the number of a walk, stride and azimuth. Because the accuracy of these variables determines the navigation performance, computational methods have been investigated. The step is detected using the walking patterns, stride is determined by neural network and azimuth is calculated with gyro output. The neural network filters off unnecessary motions. However, the error compensation method is needed, because the error of navigation information increases with time. In this paper, the accumulated error due to the step detection error, stride error and gyro bias is compensated by the integrating with GPS. Loosely coupled Kalman filter is used for the integration of WNS and GPS. It is shown by simulation that the error is bounded even though GPS signal is blocked.

• Journal of Advanced Marine Engineering and Technology
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• 제38권2호
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• pp.188-194
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• 2014

Recently, indoor localization systems based on wireless sensor networks have received a great deal of attention because they help achieve high accuracy in position determination by using various algorithms. In order to minimize the error in the estimated azimuth that can occur owing to sensor drift and recursive calculation in these algorithms, we propose a novel relative azimuth estimation algorithm. The advantages of the proposed technique in an indoor environment are that an improved weight average filter is used to effectively reduce impulse noise from the raw data acquired from nodes with inherent errors and a rotational displacement algorithm is applied to obtain a precise relative azimuth without using additional sensors, which can be affected by electromagnetic noise. Results from simulations show that the proposed filter reduces the impulse noise, and the acquired estimation error does not accumulate with time by using proposed algorithm.

• 전기학회논문지
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• 제68권1호
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• pp.122-128
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• 2019

This paper describe the method for maintaining initial azimuth of tactical grade IMU. The proposed method uses the zero velocity update (ZUPT) algorithm based on Kalman filter and the azimuth information previously obtained through transfer alignment. ZUPT technique can estimate and correct navigation attitude errors using the observed velocity error without the need of other sensors. Also, ZUPT combined pre-obtained azimuth information allows to maintain initial azimuth for tactical grade IMU. We verify the performance improvement of the proposed azimuth maintaining method by simulation and test.

• 조명전기설비학회논문지
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• 제23권10호
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• pp.1-6
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• 2009

본 논문에서는 변형 삼각간섭계에서 발생하는 파장판의 불완전성, 파장판의 방위각, 그리고 선형편광기의 방위각 오차로 인한 홀로그램의 위상오차를 유도하고, 이러한 위상오차가 포함된 홀로그램을 시뮬레이션을 통해 복원해 봄으로써 복원영상에 대하여 변형 삼각간섭계의 위상오차가 미치는 영향을 분석하였다.