• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.40 no.4
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• pp.300-308
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• 2012

In GPS/INS/barometer navigation system for UAV, two procedures were proposed in order to set three reference parameters for the pressure altitude of QNH or QFE settings, using the navigation data from on-board system alone. These procedures yield required the reference parameters through mathematical process with the altitude and the atmosphere properties measured for a short duration of flight, of which a special pattern is requested according to the selected procedure. Dependency only upon the on-board navigation data can eliminate a requirement for the atmospheric measurement system in the ground support system and can expand a flight boundary to a remote area where the ground support is not available. Especially the procedure with the regression method uses altitude and pressure but temperature to produce the three reference parameters. No need of temperature measurement for the pressure altitude system can simplify the on-board air data system.

• Journal of the Korean Institute of Intelligent Systems
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• v.13 no.2
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• pp.247-258
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• 2003

In this paper, we present a pen-shaped input device equipped with accelerometers and gyroscopes that measure inertial movements when a user writes on 2 or 3 dimensional space with the pen. The measurements from gyroscope are integrated once to find the attitude of the system and are used to compensate gravitational effect in the accelerations. Further, the compensated accelerations are integrated twice to yield the position of the system, whose basic concept stems from the field of inertial navigation. However, the accuracy of the position measurement significantly deteriorates with time due to the integrations involved in recovering the handwriting trajectory This problem is common in the inertial navigation system and is usually solved by the periodic or aperiodic calibration of the system with external reference sources or other information in the filed of inertial navigation. In the presented paper, the calibration of the position or velocity is performed on-line and off-line. In the on-line calibration stage, the complementary filter technique is used, where a Kalman filter plays an important role. In the off-line calibration stage, the constant component of the resultant navigational error of the system is removed using the velocity information and motion detection algorithm. The effectiveness and feasibility of the presented system is shown through the experimental results.

• Defense and Technology
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• no.7 s.245
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• pp.38-47
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• 1999

대기의 상태는 지역, 시간, 기상 조건 등에 따라 변하므로 고도를 계산하는데는 북반구 중위도 지방에서 관측된 기상자료 등을 기준으로 제정한 표준대기를 적용한다. 속도를 계산하는데 전압과 정압의 압력차로 정의하는 항공기용 대기속도계 차압표를 사용한다. 계산된 에어 데이터는 비행계기나 cockpit display에 표시되어 조종사에게 정보로 전달됨과 동시에 자동조종 장치, 관성항법 장치, 비행관리 시스템, 항공관리 트랜스폰더 등에 기초 자료로 공급된다

• Proceedings of the Optical Society of Korea Conference
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• 2003.07a
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• pp.272-273
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• 2003

링레이저 자이로스코프(Ring Laser Gyroscope-이하 RLG)는 비행기, 유도무기, 선박, 지상무기 등의 관성항법장치(Inertial Navigation System)에 사용되는 각속도 센서로서 항체의 위치와 자세 정보를 제공하는 핵심 구성품 중의 하나이다. 각속도 검출 원리는 삼각형 또는 사각형의 공진기에 He과 Ne을 혼합한 이득매질을 사용하여 서로 반대방향으로 회전하는 두 개의 레이저 빔을 발생시켜서 Sagnac 효과에 의해 외부의 회전 입력을 받을 때 서로 다른 광 경로의 차이로 인한 두 빔의 간섭으로 회전각을 검출한다. (중략)

• Journal of Advanced Marine Engineering and Technology
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• v.27 no.7
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• pp.914-920
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• 2003

In this paper, we deal with two drift compensation algorithms of acceleration sensor for measuring the galloping on power transmission line. Firstly, the block diagram of galloping measurement system is given and a galloping model is presented. Secondly, two compensation algorithms, a simple compensation and a period compensation, are proposed. A simple compensation algorithm uses the drifts of velocity and distance at fixed periods, so it is useful for constant drift case. Next, a period compensation algorithm can compensate a periodic drift. This algorithm uses the previous measured data and compensated data for constant period, where the period is obtained by FFT method. Lastly, the effectiveness of proposed algorithms is verified by comparing between two algorithms in simulation, and its characteristics and the drift error bound are shown, respectively.

• Journal of Ocean Engineering and Technology
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• v.17 no.4
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• pp.73-80
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• 2003

This paper presents considerations on the results of the rotating arm test, which was carried out for assessment of an hybrid navigation system for a semi-autonomous underwater vehicle. The navigation system consists of an inertial measurement unit(IMU), an ultra-short baseline(USBL) acoustic navigation sensor and a doppler velocity log(DVL) accompanying a magnetic compass. A navigational systemmodel is derived to include the scale effect and bias errors of the DVL, of which the state equation composed of the navigation states and sensor parameters are 25 in the order. The extended Kalman filter was used to propagate the error covariance, The rotating arm tests were carried out in the Ocean Engineering Basin of KRISO, to generate circular motion. The hybrid underwater navigation system shows good tracking performance against the circular planar motion. Additionally this paper checked the effects of the sampling ratio of the navigation system and the possibility of the dead reckoning with the DVL and the magnetic compass to estimate the position of the vehicle.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.40 no.11
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• pp.997-1003
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• 2012

GNSS and ARS are the most common sensors in low-end UAVs. However, these sensors are vulnerable to built-in errors and cannot measure the body heading independently. The GNSS/INS cannot fully compensate the IMU errors in initial alignment process and rectilinear flights. For an unmanned helicopter, a magnetometer can be more useful than any other sensors to obtain heading information. However, the electric motor which drives small helicopter UAV keeps the magnetometer from reading the pure magnetotelluric vector. This paper shows the effects of electric motor on the magnetometer readings, and presents a method to compensate the effects. The results are verified with flight test data. The simulation and experimental results in this paper proves that aiding GNSS/INS with magnetometer increases observability and improves accuracy.

• Proceedings of the Korea Information Processing Society Conference
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• 2015.10a
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• pp.493-495
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• 2015

PDR은 일반적으로 IMU센서로 부터의 가속도와 각속도를 측정하여 보행자의 위치를 추적하는 시스템이다. IMU센서로부터 측정된 가속도와 각속도 값은 센서를 기준으로 하기 때문에 보행자가 인지하는 고정 좌표계와는 차이가 있다. 이를 해결하기 위해 회전행렬을 사용하며 이후 계속해서 측정되는 각속도를 통해 회전행렬을 업데이트 한다. 업데이트된 회전행렬을 통해 좌표계를 환산하고 환산된 좌표계의 가속도 값으로부터 보행자는 고정좌표계 기준으로 위치 추적이 가능하다. 하지만 회전행렬을 업데이트 하는 과정에서 센서의 세 축이 이상적으로 수직이 아니라면 업데이트 과정에서 각속도의 오차가 누적되고 이는 좌표계를 환산에 영향을 끼쳐 위치 및 속도 추적 정확성을 낮춘다. 물리적인 Bias가 PDR 시스템에 누적오차를 발생시킨다. 이에 제안하는 센서 축 편향 보정 알고리즘은 IMU 센서의 물리적 축 오차를 보정해주어 더 정확한 위치 추적을 가능하게 한다. 또한 Matlab을 통해 데이터를 분석하고 알고리즘의 필요성을 보인다.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.28 no.1
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• pp.73-82
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• 2010

TERCOM(TERrain COntour Matching), which is the one of the Terrain Referenced Navigation and used in the cruise missile navigation system, is still under development. In this study, the TERCOM based on area-based matching algorithm and extended Kalman filter is analysed through simulation. In area-based matching, the mean square difference (MSD) and cross-correlation matching algorithms are applied. The simulation supposes that the barometric altimeter, radar altimeter and SRTM DTM loaded on board. Also, it navigates along the square track for 545 seconds with the velocity of 1000km per hour. The MSD and cross-correlation matching algorithms show the standard deviation of position error of 99.6m and 34.3m, respectively. The correlation matching algorithm is appeared to be less sensitive than the MSD algorithm to the topographic undulation and the position accuracy of the both algorithms is extremely depends on the terrain. Therefore, it is necessary to develop an algorithm that is more sensitive to less terrain undulation for reliable terrain referenced navigation. Furthermore, studies on the determination of proper matching window size in long-term flight and the determination of the best terrain database resolution needed by the flight velocity and area should be conducted.

• Journal of Ocean Engineering and Technology
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• v.19 no.6 s.67
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• pp.78-85
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• 2005

Initial alignment and localization are important topics in inertial navigation systems, since misalignment and initial position error wholly propagate into the navigation systems and deteriorate the performance of the systems. This paper presents the error convergence characteristics of the hybrid navigation system for underwater vehicles initial position, which is based on an inertial measurement unit (IMU) accompanying a range sensor. This paper demonstrates the improvement on the navigational performance oj the hybrid system with the range information, especially focused on the convergence of the estimation of underwater vehicles initial position error. Simulations are performed with experimental data obtained from a rotating ann test with a fish model. The convergence speed and condition of the initial error removal for random initial position errors are examined with Monte Carlo simulation. In addition, numerical simulation is conducted with an AUV model in lawn-mowing survey mode to illustrate the error convergence of the hybrid navigation System for initial position error.