• Journal of the Korean Society of Marine Environment & Safety
• /
• v.19 no.6
• /
• pp.666-673
• /
• 2013

This paper proposes the performance evaluation test of attitude heading reference system (AHRS) suitable for small high speed autonomous underwater vehicle(AUV). Although IMU can provides the detail attitude information, it is sometime not suitable for small AUV with short operation time in view of price and the electrical power consumption. One of alternative for tactical grade IMU is the AHRS based micro-machined electro mechanical system(MEMS) which can overcome many problems that have inhibited the adoption of inertial system for small AUV such as cost and power consumption. A cost effective and small size AHRS which incorporates measurements from 3-axis MEMS gyroscopes, accelerometers, and 3-axis magnetometers has been developed to provide a complete attitude solution for AUV and the attitude calculation algorithm is derived based the coordinate transform equation and Kalman filter. The developed AHRS was validated through various performance tests as like the magnetometer calibration, operating experiments using land mobile vehicle and flight motion simulator (FMS). The test of magnetometer calibration shows the developed MEMS AHRS is robust to the external magent field change and the test with land vehicle proves the leveling error of developed MEMS AHRS is below $0.5^{\circ}/hr$. The results of FMS test shows the fact that AHRS provides the measurement with $0.5^{\circ}/hr$ error during 5 minutes operation time. These results of performance evaluation tests showed that the developed AHRS provides attitude information which error of roll and pitch are below $1^{\circ}$ and the error of yaw is below $5^{\circ}$ and satisfies the required specification. It is expected that developed AHRS can provide the precise attitude measurement under sea trial with real AUV.

• Current Research on Agriculture and Life Sciences
• /
• v.32 no.3
• /
• pp.159-163
• /
• 2014

Agricultural unmanned helicopters have become a new paradigm for aerial application. Yet, such agricultural helicopters require easy and affordable attitude control systems. Therefore, this study presents an affordable attitude measurement system using a DCM (direction cosine matrix) algorithm that would be applied to agricultural unmanned helicopters. An IMU using a low-cost MEMS and an algorithm to estimate the attitude of the helicopter were applied in a gimbals structure to evaluate the accuracy of the attitude measurements. The estimation errors in the attitude were determined in comparison with the true angles determined by absolute position encoders. The DCM algorithm and sensors showed an accuracy of about 1.1% for the roll and pitch angle estimation. However, the accuracy of the yaw angle estimation at 3.7% was relatively larger. Such errors may be due to the magnetic field of the stepping motor and encoder system. Notwithstanding, since the intrinsic behavior of the agricultural helicopter remains steady, the determination of attitude would be reliable and practical.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.40 no.12
• /
• pp.997-1003
• /
• 2016

This paper presents an application of adaptive algorithms for yaw moment distribution with electronic stability control (ESC) and active rear steering (ARS) in integrated chassis control (ICC). Integrated chassis control consists of upper- and lower-level controllers. In the upper-level controller, the control yaw moment is computed with sliding mode control required to stabilize a vehicle. In the lower-level controller, adaptive algorithms are applied to determine the required brake pressure of ESC and the necessary steering angle of ARS, in order to generate the control yaw moment. Simulation is performed using the vehicle simulation package CarSim to validate the proposed method.

• Journal of Advanced Navigation Technology
• /
• v.15 no.2
• /
• pp.181-188
• /
• 2011

A small UAVs(Unmaned Aerial Vehicles) have limited by the payload capacity which requires miniaturization of a navigation system. In this paper, the performance of the lightweight and small sized AHRS(Attitude Heading Reference System), which is self-developed, is evaluated at low acceleration environment. The designed AHRS adopts the commercial low-cost MEMS sensors. A quaternion-based attitude calculation method, which eliminates singularity with relatively simple algebra, is used. In an attitude correction algorithm, the Kalman filter is used with accelerometers and magnetometers combined. The fabricated AHRS is also evaluated with reference to a COTS(Commercial Off-The-Shelf) AHRS which reports a number of successful applications to a small UAVs. The test results show that the measurements from the fabricated AHRS provide proper attitude output data with acceptable amount of differences(horizontal axis 0.5$^{\circ}$, vertical axis 1.5$^{\circ}$) in test environment.

• Journal of the Korea Convergence Society
• /
• v.8 no.12
• /
• pp.283-289
• /
• 2017

In this study, a general program has been developed to calculate the static design factor of a vehicle suspension system. The partial derivatives of Jacobians for constraint equations are calculated using the symbolic technique. In the commercial program, finite difference method is used to calculate the Jacobian matrix of Jacobian. But in this study, it is calculated by using the symbol calculation method to precisely consider it. The calculated Jacobian matrix for the system has proved its accuracy through the solution of the numerical example. A simulation was performed for a double wishbone suspension of a 1/4 vehicle. The result can be used to calculate the static design factor of the suspension, and also add a convergence module that can perform virtual tests.

• Journal of Astronomy and Space Sciences
• /
• v.8 no.1
• /
• pp.85-98
• /
• 1991

Geomagnetism was used to control the attitude of the small scientific satellite at low altitude in sun-synchronous orbit. First, we analyzed the telemetry data. The rotation state of the satellite, can be known from the magnitude and variations of the magnetic field which is measured from the 3 axis magnetometer. In axisymmetric case, it is possible to control the attitude of the satellite by changing the rotation velocity of each 3 axis. The algorithm and the program were developed to calculate the supply time of the current operating the magnetorquer. This attitude control can be applied when the satellite is in tumbling motion and after passive control is attained by the Gravity gradient boom.

• Journal of the Korea Institute of Military Science and Technology
• /
• v.11 no.6
• /
• pp.30-37
• /
• 2008

The ARS(Attitude Reference System) calculates an attitude of a vehicle using inertial angular rate sensors and acceleration sensors. The attitude error of ARS increases due to the integration of angular rate sensor output. To reduce the attitude error an acceleration of sensor is used similar to leveling method of INS(Inertial Navigation System). When an acceleration of vehicle is increased, it is difficult to calculate the attitude error using acceleration sensor output. In this paper the estimation method of acceleration due to the attitude error only is proposed. Two methods of the attitude calculation depending on vehicle dynamics and the integration method of these two methods are proposed. To verify its performance the monte carlo simulation is performed and shows that it bounds attitude error of ARS to reasonable level.

• Proceedings of the Korean Society of Computer Information Conference
• /
• 2014.01a
• /
• pp.481-482
• /
• 2014

본 논문에서는 잘못된 걸음걸이로 인해 생기는 다양한 질환들을 예방하고자 압력센서를 통해 걸음형태를 측정하여 블루투스 통신을 이용, 사용자가 스마트폰에서 실시간으로 확인 할 수 있게 하였고, 잘못된 자세를 인식 할 수 있도록 구현하였다. 이 시스템을 통하여 자신의 잘못된 보행 자세를 인지하고 바른 걸음을 할 수 있도록 도움을 주도록 하며 운동시에는 만보기와 칼로리를 계산하는 기능을 활용할 수 있다.

• The Bulletin of The Korean Astronomical Society
• /
• v.37 no.2
• /
• pp.191.2-191.2
• /
• 2012

저궤도 위성을 설계함에 있어 시스템 수준에서 수행하는 질량특성의 계산은 위성을 구성하는 각각의 구성품에 대한 정보를 종합하여 전체 시스템의 특성을 예측하는 작업이다. 질량특성에 대한 요구조건은 발사체로부터 설정되는데 요구조건 항목은 탑재체질량, 무게중심 그리고 관성모멘트에 관한 것이다 또한, 자세제어면에서 추력에 의한 토크에 따른 무게 중심 등이며 최근 위성의 고기동화 요구에 따라 기동요구조건 및 자세구동장치의 용량에 따라 결정된다. 특히 위성의 궤도형상 관성모멘트는 위성 동특성을 표시하므로 이를 사용하여 제어시뮬레이션을 수행하는 자세제어계에 주요 입력 데이터로 활용된다. 본 논문에서는 저궤도 위성의 질량특성 요구조건을 검증하기 위해 수행한 질량특성 예측과 질량특성 측정 시험에 대해서 기술하고자 한다.

• Journal of the Institute of Convergence Signal Processing
• /
• v.24 no.1
• /
• pp.15-20
• /
• 2023

In general, maintaining an incorrect sitting posture for a long time is widely known to adversely affect the spine. Recently, several researchers have been interested in the causal relationship between incorrect sitting posture and spinal diseases, and have been studying methods to precisely measure changes in sitting or standing posture to prevent spinal diseases. In previous studies, we have developed a sensor device capable of measuring real-time posture change, applied a momentum calculation algorithm to improve the accuracy of real-time posture change measurement, and verified the accuracy of the postural change measurement sensor. In this study, we developed a posture measurement and analysis device that considers changes in the center of body pressure through the developed sitting pressure measurement, and it confirmed the sensor as an auxiliary tool to increase the accuracy of posture correction training with improving the user's visual feedback.