• Journal of the Optical Society of Korea
• /
• 제3권2호
• /
• pp.80-85
• /
• 1999

We propose and demonstrate a new scheme for suppression of output distortion in an open-loop gyroscope employing an erbium-doped fiber amplifier/source (FAS). In addition to the main modulation for the rotation rate measurement, a small auxiliary modulation at a different frequency is used to extract an error signal, which is necessary for keeping the quasi-dc component of the feedback signal power at a constant level for varying rotation rate. By active tracking of the optimum modulation condition using this two-frequency modulation scheme, we obtain stable gyro output with suppressed distortion as well as stable FAS characteristics. We also calculate the distortion in the gyro response due to the feedback effect, from which we estimate the FAS gyro output distortion due to the residual ac feedback effect when the dc feedback effect is removed by the proposed scheme. The measured residual deviation agrees reasonably with the estimation.

• Journal of Computational Design and Engineering
• /
• 제1권1호
• /
• pp.1-12
• /
• 2014

In this paper, we propose a new method of reconstructing the hand models for individuals, which include the link structure models, the homologous skin surface models and the homologous tetrahedral mesh models in a reference posture. As for the link structure model, the local coordinate system related to each link consists of the joint rotation center and the axes of joint rotation, which can be estimated based on the trajectories of optimal markers on the relative skin surface region of the subject obtained from the motion capture system. The skin surface model is defined as a three-dimensional triangular mesh, obtained by deforming a template mesh so as to fit the landmark vertices to the relative marker positions obtained motion capture system. In this process, anatomical dimensions for the subject, manually measured by a caliper, are also used as the deformation constraints.

• 천문학회보
• /
• 제36권1호
• /
• pp.86.1-86.1
• /
• 2011

Most astrophysical systems are turbulent and magnetized. Magnetic field plays an important role in the dynamics of ISM and influence all of properties of astrophysical system. Information of magnetic field is very important to understand properties of astrophysical systems. For example, one way to obtain information of magnetic field is to use Rotation Measure. Mean strength of the magnetic field along the line of sight can be estimated from RM/DM. (where RM is rotation measure, DM is dispersion measure) For the estimation of magnetic field strength using RM/DM, the correlation between density and magnetic field is very important. When there is no correlation between density and magnetic field the relation gives exact mean magnetic field strength. But, if the correlation is positive, it overestimates the magnetic field strength, while if the correlation is negative, it underestimate the strength. We calculate correlation between density and magnetic field in compressible MHD turbulence.

• 한국철도학회:학술대회논문집
• /
• 한국철도학회 2008년도 추계학술대회 논문집
• /
• pp.673-678
• /
• 2008

In crushed service areas of Metro railway lines, there are problems such as the buildup discontent, the irregular operation time and rotation of rolling stocks, caused by frequently occurred train delay. Train delay is affected by operation conditions or infrastructure capacities such as train schedule, line capacity, car rotation plan, shunting movements at origin and destination, and also by transport demand characteristics. Furthermore, a delay produce another delays and spread over the following trains. So it is not easy to build up a protection and recovery plan. In this research, we conduct experimental analysis study based on the real metro data, and as a result, present the relation between the traffic demand and the dwell time. And finally, propose future research themes for improving the operation efficiency of metro railways.

• 로봇학회논문지
• /
• 제14권1호
• /
• pp.14-21
• /
• 2019

In the ground environment, mobile robot research uses sensors such as GPS and optical cameras to localize surrounding landmarks and to estimate the position of the robot. However, an underwater environment restricts the use of sensors such as optical cameras and GPS. Also, unlike the ground environment, it is difficult to make a continuous observation of landmarks for location estimation. So, in underwater research, artificial markers are installed to generate a strong and lasting landmark. When artificial markers are acquired with an underwater sonar sensor, different types of noise are caused in the underwater sonar image. This noise is one of the factors that reduces object detection performance. This paper aims to improve object detection performance through distortion and rotation augmentation of training data. Object detection is detected using a Faster R-CNN.

• Journal of Positioning, Navigation, and Timing
• /
• 제2권1호
• /
• pp.81-89
• /
• 2013

Many of the current visual odometry algorithms suffer from some extreme limitations such as requiring a high amount of computation time, complex algorithms, and not working in urban environments. In this paper, we present an approach that can solve all the above problems using a single camera. Using a planar motion assumption and Ackermann's principle of motion, we construct the vehicle's motion model as a circular planar motion (2DOF). Then, we adopt a 1-point method to improve the Ransac algorithm and the relative motion estimation. In the Ransac algorithm, we use a 1-point method to generate the hypothesis and then adopt the Levenberg-Marquardt method to minimize the geometric error function and verify inliers. In motion estimation, we combine the 1-point method with a simple least-square minimization solution to handle cases in which only a few feature points are present. The 1-point method is the key to speed up our visual odometry application to real-time systems. Finally, a Bundle Adjustment algorithm is adopted to refine the pose estimation. The results on real datasets in urban dynamic environments demonstrate the effectiveness of our proposed algorithm.

• Smart Structures and Systems
• /
• 제9권3호
• /
• pp.273-286
• /
• 2012

As civil structures are exposed to various external loads, it is essential to assess the structural condition, especially the structural displacement, in every moment. Therefore, a visually servoed paired structured light system was proposed in the previous study. The proposed system is composed of two screens facing with each other, each with a camera, a screen, and one or two lasers controlled by a 2-DOF manipulator. The 6-DOF displacement can be calculated from the positions of three projected laser beams and the rotation angles of the manipulators. In the estimation process, one of well-known iterative methods such as Newton-Raphson or extended Kalman filter (EKF) was used for each measurement. Although the proposed system with the aforementioned algorithms estimates the displacement with high accuracy, it takes relatively long computation time. Therefore, an incremental displacement estimation (IDE) algorithm which updates the previously estimated displacement based on the difference between the previous and the current observed data is newly proposed. To validate the performance of the proposed algorithm, simulations and experiments are performed. The results show that the proposed algorithm significantly reduces the computation time with the same level of accuracy compared to the EKF with multiple iterations.

• 한국항공우주학회지
• /
• 제38권7호
• /
• pp.693-701
• /
• 2010

본 논문에서는 스테레오 카메라 시스템을 이용하여 헬멧의 자세 및 위치를 추정하는 알고리즘을 제안한다. 본 논문에서 구축한 시스템은 두 대의 CCD카메라와 헬멧 그리고 적외선 LED, 영상편집 보드로 구성된다. 이 중 15개의 적외선 LED는 헬멧에 서로 다른 길이로 삼각형 패턴으로 고정되어, 헬멧의 자세 및 위치를 결정하기 위한 특징점이 된다. 본 논문에서 제안한 알고리즘은 특징점 추출, 투영 재구성, 모델 인덱싱 과정으로 구성되며, 단위 쿼터니언(UQ, Unit Quaternion)을 이용하여 자세 및 위치를 추정한다. UQ를 이용하여 회전행렬를 구하면, 회전 행렬이 유니터리 행렬(Unitary Matrix)이 되는 것을 보장할 수 있다. 제안된 알고리즘은 시뮬레이션과 실제 실험 데이터를 이용하여 그 성능을 검증하였다.

• 한국군사과학기술학회지
• /
• 제19권2호
• /
• pp.155-162
• /
• 2016

TASS(Towed Array Sonar System) is a sonar system which tows the sensor array behind a platform. Array shape is generally assumed to be a straight line. But the array shape is often distorted by oceanic current or platform maneuvering which causes the performance loss of signal processing method like beamforming. So array shape estimation methods are needed. Typically the method based on Kalman filter using heading sensor is used. In practice, the measurement is corrupted by biases which are caused by rotation of the tow cable, varying magnetic fields and slowly varying stresses in the mechanical construction. Although they can't be calibrated but can be estimated. In this paper, we suggest the array shape estimation method based on Kalman filter compensating the sensor biases.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2001년도 추계학술대회논문집 II
• /
• pp.1166-1171
• /
• 2001

The method for output disturbance estimation is proposed. In this method, output disturbance is estimated from the closed loop system dynamics using the output and control input signals. In the closed-loop output-disturbance estimator, precise system identification is required to reduce estimation error. The realization of estimator was done by the DSP board (DSPl103), and disturbance estimation in various environments was performed： change of rotation speed, media feature and spindle motor with (or without) auto-ball balancing system (ABS). From these experiments, the disturbance characteristics of ODD under various conditions are analyzed, and the desirable servo loop configuration based these results is proposed.