• 제어로봇시스템학회:학술대회논문집
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• 1993.10a
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• pp.34-39
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• 1993

Presented in this paper is a complete error covariance analysis for strapdown inertial navigation system(SDINS). We have found that in SDINS the cross-coupling terms in gyrocompass alignment errors can significantly influence the SDINS error propagation. Initial heading error has a close correlation with the east component of gyro bias erro, while initial level tilt errors are closely related to accelerometer bias errors. In addition, pseudo-state variables are introduced in covariance analysis for SDINS utilizing the characteristics of gyrocompass alignment errors. This approach simplifies the covariance analysis because it makes the initial error covariance matrix to a diagonal form. Thus a real implementation becomes easier. The approach is conformed by comparing the results for a simplified case with the covariance analysis obtained from the conventional SDINS error model.

• 제어로봇시스템학회:학술대회논문집
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• 1996.10b
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• pp.482-485
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• 1996

We design a homing guidance law based on the proportional navigation for the fast-rolling, single-axis control missiles and analyse the misdistance of the designed guidance system. The guidance law includes a compensation scheme which compensates for the phase-shift between the commanded and achieved acceleration which is peculiar to the fast rolling airframe with single-axis control. In the error analysis of the guidance system, we calculate the misdistance with respect to the target maneuver on the 3-dimensional space via direct simulations. Also, we conduct adjoint simulation on the 2-dimensional plane in case that phase-shift is perfectly compensated. Finally we approximate the linear time-varying dynamics of the missile with autopilot to a linear time-invarient system, and as a result we can find the misdistance as a closed-form.

• 제어로봇시스템학회:학술대회논문집
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• 1992.10a
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• pp.401-406
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• 1992

When a velocity-aided strapdown inertial navigation system is loaded into a torpedo subjected to an extraneous force by the current, odometer measurement errors occur seriously. In order to compensate for navigation errors induced by large odometer biases, the Kalman Filter with separate bias estimator is applied, which separately estimates an unknown bias, and corrects the state estimate produced by the bias-free Kalman Filter to reflect the effect of the bias estimate.

• Journal of Advanced Navigation Technology
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• v.15 no.4
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• pp.510-516
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• 2011

For using Global Navigation Satellite System(GNSS) in the civil aviation, it should satisfies the Required Navigation Performances(RNPs) which are defined by International Civil Aviation Organization(ICAO). RNP defines the required accuracy, integrity, availability, continuity of each flight procedure. In order to guarantee user's integrity, user's protection level has to be overestimated. On the other hand, for improving user's availability, user's protection level has to be estimated tightly. Therefore protection level should be estimated as tight as possible while it assuring the user's integrity. This paper describes the current integrity function of Korean WAD GNSS test bed, and predicts the availability performance of Korean WAD GNSS by simulation.

• Journal of the Korean Geophysical Society
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• v.9 no.4
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• pp.361-369
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• 2006

This study conducted an initialization test to decide dynamic position using AHRS IMU sensor, and derived attitude correction angles of vehicles against time through regression analysis. It was also found that the heading angle was stabilized with variation less than 1°after 60 seconds. Using these angles, this study carried out an experiment on the determination of dynamic position for each system in the open sky and in a semi-open sky. According to the results, in the open sky, DGPS alone systems were excellent in accuracy but poor in data acquisition, so the moving distance was around 12m. In DGPS/IMU combined system, accuracy and data acquisition were satisfactory and the moving distance was around 0.3m. In a semi-open sky, DGPS alone systems were excellent in accuracy in order of DGPS < FIMU < DGPS/IMU according to average and standard errors obtained with exclusion of places where data were not be obtained. The moving distance was the same as that in the open sky. For DGPS, when places where data were not obtainable were divided into Several block and they were compared, the maximum deviation from the trajectory was up to 41.5m in DGPS alone system, but it was less than 2.2m and average and standard errors were significantly improved in the combined system. When the navigation system was applied to surveys and the result was compared with position error 0.2mm under the guideline for digital map, it was possible to work on maps on a scale of up to 1 : 1,000.

• The Journal of the Korea institute of electronic communication sciences
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• v.8 no.1
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• pp.27-40
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• 2013

This study is about development of technology system for an advanced deep-sea unmanned underwater robot of S. Korea analysed by the application of scenario planning. It was developed a 6000m class next-generation deep-sea unmanned underwater vehicle(or robot, UUV) system, soonly ROV 'Hemire' and Depressor 'Henuvy' in 2006 at S. Korea and motion control, adaptive control algolithm, a work-space manipulator control algolithm, especially the underwater inertial-acoustic navigation system robust to initial errors and sensor failures. But there are remained matters on position tracking of the USBL, inertial-acoustic navigation system, attitude sensor, designed sonar sensors. So this study suggest the new idea for settle the matters and then this idea help the development of the underwater inertial-acoustic navigation system robust to initial errors and sensor failures, such as acoustic signal drop-out, by modifying the error covariance of the failed sonar signal when drop-out occurs. As a result, the future policy for deep-sea unmanned underwater robot of S. Korea is to further spur the development of new technology and more improvement of the technology level for deep-sea unmanned underwater robot system with indicator and imaginary wall as external device.

• Journal of Astronomy and Space Sciences
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• v.26 no.2
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• pp.199-210
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• 2009

Even though there are several Global Navigation Satellite Systems under development, only GPS and GLONASS are currently available for satellite positioning. In this study, GLONASS orbits were predicted from broadcast ephemeris using the 4th-order Runge-Kutta numerical integration. For accuracy validation, predicted orbits were compared with precise ephemeris. The RMS(Root Mean Square) and maximum 3-D errors were 14.3 km and 17.4 km for one-day predictions. In case of 7-day predictions, the RMS and maximum 3-D errors were 15.7 and 40.1 km, respectively. Also, the GLONASS satellite visibility predictions were compared with real observations, and they agree perfectly except for several epochs when the satellite signal was blocked by nearby buildings.

• Journal of the Korean Institute of Intelligent Systems
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• v.23 no.6
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• pp.505-510
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• 2013

In order to detect and identify the GPS clock anomaly in the Differential GPS real environment, this paper addresses a method for minimizing the measurement noise of reference receivers. It estimates the real measurement noise that removed the uncommon error source from pseudorange measurement to minimize the measurement noise. Based on the output of two reference receivers, it first removes the uncommon errors, then optimizes the measurement noise by applying the correction data. Finally, it detects and identifies the satellite clock anomaly using the minimized measurement noise. The method will increase the availability of current DGPS reference system.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.15 no.12
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• pp.2619-2625
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• 2011

The GPS technique widely used recently in car navigation system has two problems that are unavailability in urban canyons and inherent positional error rate. The one has been studied and solved in many literatures. However, the other still leads to incorrect locational information in some area, especially parallel roads. This paper proposes and implements a system to recognize lane of moving vehicle based on images obtained from in-vehicle networks or other devices. The proposed system utilizes a real-time image matching algorithm which determines the direction of moving vehicle in parallel section of road. It also employs a method for accuracy improvement. The results obtained from experimental test on real-time navigation show that the proposed systems works well and the accuracy increases.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.33 no.12
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• pp.61-67
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• 2005

This paper presents the carrier phase DGPS method providing a stable navigation solution under the condition of frequent blockage of the GPS signals. The proposed algorithm reject the channels having large errors using a clock bias drift and then calculated the more accurate solution. By investigating the relation between visible satellites` elevation and their clock bias drift, a proper threshold is set. Simulation shows that the presented result is as good as that of commercial system with real data.