• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.43 no.7
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• pp.609-618
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• 2015

This paper discusses the attitude determination of the CNUSAIL-1 cube-satellite. The primary mission of the CNUSAIL-1 is sail deployment and operation in low Earth orbit, and the secondary mission is to look into influence of the sail deployment on satellite attitude and orbit. The attitude determination strategy is proposed depending on three mission phases, and its performance and applicability are verified through numerical simulations. This study considers the following sensors: Sun sensors and a three-axis magnetometer as attitude reference sensors, and a three-axis MEMS gyroscope as an inertial attitude sensor. Because sensors used for cube satellites have relatively low performances and worse noise characteristics, an Extended Kalman filter (EKF) is applied to attitude determination. Additionally, it has the merits to deal with the Gaussian noises and to predict the attitude even with no measurements from reference attitude sensors, especially in the eclipse of the cube satellite. The performance of the EKF is compared to a deterministic attitude determination technique, QUEST(QUaternion ESTimation).

• Journal of Institute of Control, Robotics and Systems
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• v.18 no.1
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• pp.54-61
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• 2012

In this paper, the pose estimation method for the satellite GTB (Ground Test Bed) using vision/MEMS IMU (Inertial Measurement Unit) integrated system is presented. The GTB for verifying a satellite system on the ground is similar to the mobile robot having thrusters and a reaction wheel as actuators and floating on the floor by compressed air. The EKF (Extended Kalman Filter) is also used for fusion of MEMS IMU and vision system that consists of a single camera and infrared LEDs that is ceiling landmarks. The fusion filter generally utilizes the position of feature points from the image as measurement. However, this method can cause position error due to the bias of MEMS IMU when the camera image is not obtained if the bias is not properly estimated through the filter. Therefore, it is proposed that the fusion method which uses the position of feature points and the velocity of the camera determined from optical flow of feature points. It is verified by experiments that the performance of the proposed method is robust to the bias of IMU compared to the method that uses only the position of feature points.

• Journal of Advanced Navigation Technology
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• v.25 no.1
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• pp.68-77
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• 2021

In this paper, a GPS/MEMS IMU integrated navigation receiver module capable of operating in a high dynamic environment is designed and fabricated, and the results is confirmed. The designed module is composed of RF receiver unit, inertial measurement unit, signal processing unit, correlator, and navigation S/W. The RF receiver performs the functions of low noise amplification, frequency conversion, filtering, and automatic gain control. The inertial measurement unit collects measurement data from a MEMS class IMU applied with a 3-axis gyroscope, accelerometer, and geomagnetic sensor. In addition, it provides an interface to transmit to the navigation S/W. The signal processing unit and the correlator is implemented with FPGA logic to perform filtering and corrrelation value calculation. Navigation S/W is implemented using the internal CPU of the FPGA. The size of the manufactured module is 95.0×85.0×.12.5mm, the weight is 110g, and the navigation accuracy performance within the specification is confirmed in an environment of 1200m/s and acceleration of 10g.

• Proceedings of the KIEE Conference
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• 2004.05a
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• pp.120-122
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• 2004

Wearable input device that can make free-space typewriting possible is introduced. We named this device as $SCURRY^{TM}$. To measure the angular velocity of hand and the acceleration rates at the ends of fingers, we buried MEMS inertial sensors in this keyboard. We processed sensor signals to get the information on hand movement and finger-click motion. With this signal processing, apparent finger movements were depicted over the virtual keyboard shown on output device of a target computing system. In this paper, a finger-click recognition method is proposed to improve the recognition performance for finger clicking of $SCURRY^{TM}$. The proposed method is composed of three parts including feature extraction part, valid click part, and cross-talk avoidance part. The experiments were conducted to verify the effectiveness and efficiency of the proposed algorithms.

• Journal of Advanced Navigation Technology
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• v.23 no.3
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• pp.228-236
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• 2019

Recently, multi-sensor integration techniques have been actively studied to obtain reliable and accurate navigation solution in GPS (Global Positioning System)-denied harsh environments such as urban canyons, tunnels, and underground roads. In this paper, we propose a low-cost ultrasonic-speedometer utilizing the characteristics of the ultrasonic propagation. An efficient integrated INS (inertial navigation system)/ultrasonic-speedometer navigation system is also proposed to improve the accuracy of positioning in GPS-denied environments. To evaluate the proposed system, car experiments with field-collected measurements were performed. By the experiment results, it was confirmed that the proposed INS/ultrasonic-speedometer system bounds the positioning error growth effectively even though GPS signal is blocked more than 10 seconds and a low-cost MEMS IMU (micro electro mechanical systems inertial measurement unit) is utilized.

• Current Industrial and Technological Trends in Aerospace
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• v.5 no.2
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• pp.58-66
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• 2007

지상, 항공 및 우주를 이동하는 모든 물체는 반드시 자신의 자세를 결정하기 위해서 여러 가지 센서들을 장착하여 그 신호를 이용해서 자동 항법, 유도 및 제어를 수행한다. 이때, 동역학 특성이 빠른 시스템들은 반드시 각속도를 측정할 수 있어야 하는데 이를 해결하는 장비가 자이로인 것이다. 본 논문에서는 다양한 자이로를 소개하며 그 원리와 성능 그리고 적용 분야에 이르기까지 현황을 집중 분석하고 특히 세계적인 자이로 개발업체를 소개하면서 그 업체가 보유하고 있는 제품들을 일부 소개한다. 자이로는 초창기 김벌 시스템을 이용한 관성원리를 적용한 것부터 시작하여 현재는 광학 시스템을 적용한 RLG 및 FOG 자이로가 많은 분야에서 사용되고 있고, 최근 새롭게 부각되어 개발을 시작하고 있는 MEMS 자이로가 있는데 아직 우주 비행체 분야에서는 적용되지 못하고 있다. 그리고, 자이로의 큰 범주로 다루어지지는 않지만 자기력을 이용해서 회전체인 로터와 고정체인 플랫폼 사이에 기계식 접촉이 전혀 없는 새로운 시스템인 ESG 자이로도 일부 상용으로 생산되고 있다. 현재까지는 기계식 자이로의 정밀도 및 안정성이 광학식 자이로보다 우수하여 많이 사용되고 있지만 최근의 개발 추세로 보면 곧 광학식 자이로의 강세가 두드러질 것으로 보인다.