• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.10a
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• pp.175-175
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• 2003

• Journal of Institute of Control, Robotics and Systems
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• v.17 no.2
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• pp.157-163
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• 2011

This paper proposes a hybrid image stabilizing system which uses both optical image stabilizing system based on EKF (Extended Kalman Filter) and digital image stabilization based on SURF (Speeded Up Robust Feature). Though image information is one of the most efficient data for object recognition, it is susceptible to noise which results from internal vibration as well as external factors. The blurred image obtained by the camera mounted on a robot makes it difficult for the robot to recognize its environment. The proposed system estimates shaking angle through EKF based on the information from inclinometer and gyro sensor to stabilize the image. In addition, extracting the feature points around rotation axis using SURF which is robust to change in scale or rotation enhances processing speed by removing unnecessary operations using Hessian matrix. The experimental results using the proposed hybrid system shows its effectiveness in extended frequency range.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.8
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• pp.1577-1585
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• 2011

This paper proposes a posture stabilization control algorithm for a wheeled mobile robot using hybrid visual servo control method with a position based and an image based visual servoing (PBVS and IBVS). To overcome chattering phenomena which were shown in the previous researches using a simple switching function based on a threshold, the proposed hybrid visual servo control law introduces the fusion function based on a blending function. Then, the chattering problem and rapid motion of the mobile robot can be eliminated. Also, we consider the nonlinearity of the wheeled mobile robot unlike the previous visual servo control laws using linear control methods to improve the performances of the visual servo control law. The proposed posture stabilization control law using hybrid visual servoing is verified by a theoretical analysis and simulation and experimental results.

• Proceedings of the Korea Institute of Convergence Signal Processing
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• 2000.08a
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• pp.285-288
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• 2000

본 논문에서는 카메라 플랫홈의 흔들림 등으로 인한 외부 영향으로 출렁이는 비디오를 전자적으로 안정화시키는 방법을 제안한다. LOG operator〔1〕을 이용하여 특징점을 잡고 그 특징점을 중심으로 일정크기의 subblock에 대해서만 correlation을 구한다. Least Square를 이용하여 모션 파라메타를 측정하고 모션 보상을 행하는데 현재의 영상을 기준 좌표계로 변환하고 명암값 보간을 하게된다. 이 때 기존 연구에서 많이 사용한 bilinear 보간법의 단점인 대비가 첨예한 곳에서의 averaging 효과를 없애기 위해 본 연구에서는 대비가 첨예한 곳에서는 nearest neighbor 보간을 사용하고 그렇지 않은 곳에서는 bilinear 보간을 사용하는 hybrid한 방법을 채택하였다. 그 결과 사람이 카메라를 손에 들고 움직일 때 생기는 출렁이는 비디오에 대해 대부분의 카메라 움직임을 안정화시킬 수 있었다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.47 no.10
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• pp.720-727
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• 2019

Resonating thermal lags of solid fuel with heat transfer oscillations generated by boundary layer oscillation is the primary mechanism of the occurrence of the LFI (Low Frequency Combustion Instability) in hybrid rocket combustion. This study was experimentally attempted to confirm that how the boundary layer was perturbed and led to the LFI. Special attention was also made on oxidizer swirl injection to investigate the contribution to combustion stabilization. Also the overall behavior of fluctuating boundary layer flow and the occurrence of the LFI was monitored as swirl intensity increased. Fluctuating boundary layer was successfully monitored by the captured image and POD (Proper Orthogonal Decomposition) analysis. In the results, oscillating boundary layer became stabilized as the swirl intensity increases. And the coupling strength between high frequency p', q' diminished and periodical amplification of RI (Rayleigh Index) with similar frequency band of thermal lag was also decreased. Thus, results confirmed that oscillating axial boundary layer triggered by periodic coupling of high frequency p', q' is the primary mechanism to excite thermal resonance with thermal lag characteristics of solid fuel.