• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2006년도 하계종합학술대회
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• pp.835-836
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• 2006

For non-contact structure vibration displacement measurement system, an algorithm for image processing using high speed CCD camera is introduced. The system sets the target to the structure, take picture using camera and image processing is performed to display the vibration data. The algorithm flow is basic preprocessing, projection data generation and curve fitting to find three crossing points for calibration or one center point in limited area.

• 한국정밀공학회지
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• 제27권9호
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• pp.43-51
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• 2010

Speed, accuracy and smoothness are the important properties of pan-tilt camera. In the case of a high ratio zoom lens system, low vibration characteristic is a crucial point in driving pan-tilt mechanism. In this paper, a novel micro-stepping controller with a function of reducing vibration was designed using field programmable gate arrays (FPGA) technology for high zoom ratio pan-tilt camera. The proposed variable reference current (VRC) control scheme reduces vibration decently and optimizing coil current in order to prevent the step motor from occurring missing steps. By employing VRC control scheme, the vibration in low speed could be significantly minimized. The proposed controller can also make very high speed of 378kpps micro-step driving, and increase maximum acceleration in motion profiles.

• Smart Structures and Systems
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• 제10권6호
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• pp.547-555
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• 2012

Measuring crack length in concrete fracture test is not a trivial problem due to high speed crack propagation. In this study, mechanoluminascent (ML) material, which emits visible light under stress condition, was employed to visualize crack propagation during concrete fracture test. Three-point bending test was conducted with a notched concrete beam specimen. The cracking images due to ML phenomenon were recorded by using a high speed camera as a function of time and external loadings. The experimental results successfully demonstrated the capability of ML material as a promising visualization tool for concrete crack propagation. In addition, an interesting cracking behavior of concrete bending fracture was observed in which the crack propagated fast while the load decreased slowly at early fracture stage.

• 한국생산제조학회지
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• 제23권1호
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• pp.21-26
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• 2014

An arrow produced by a manufacturing process is evaluated using the archer's paradox and the intensity of the impact point. The accuracy rate in particular is changed by the arrow's vibrational movement, which is called the archer's paradox. The archer's paradox occurs not only in the right, left, upward, and downward directions, but in all directions. The optimized value of the archer's paradox has not been studied yet. This paper proposes to measure the archer's paradox to determine its optimized value. Measuring the archer's paradox using a high-speed camera is expensive, and it is difficult to translate the result to a numerical value. However, the device for measuring the archer's paradox proposed in this paper is inexpensive, and the results are easy to convert to a numerical value. Therefore, this device is more suitable for optimization of the archer's paradox than a high-speed camera. In this paper, we propose to measure the size of the paradox using multiple frames, which can measure the position of an arrow moving at a speed of 300km/h to within millimeters. We calculate the size of the paradox experimentally using the measured location in each frame. This value is not an approximate value, but an accurate numerical value.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제10권9호
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• pp.4419-4441
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• 2016

A cause of vehicle accidents is the reduced visibility due to bad weather conditions such as fog. Therefore, an onboard vision system should take visibility detection into account. In this paper, we propose a simple and effective approach for measuring the visibility distance using a single camera placed onboard a moving vehicle. The proposed algorithm is controlled by a few parameters and mainly includes camera parameter estimation, region of interest (ROI) estimation and visibility computation. Thanks to the ROI extraction, the position of the inflection point may be measured in practice. Thus, combined with the estimated camera parameters, the visibility distance of the input foggy image can be computed with a single camera and just the presence of road and sky in the scene. To assess the accuracy of the proposed approach, a reference target based visibility detection method is also introduced. The comparative study and quantitative evaluation show that the proposed method can obtain good visibility detection results with relatively fast speed.

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

• 한국정보기술학회 영문논문지
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• 제10권2호
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• pp.153-166
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• 2020

DDI(Display Driver IC) are used to drive numerous pixels that make up display. For stable driving of DDI, it is necessary to attach a protective film to shield electromagnetic waves. When the protective film is attached, defects often occur if the film is inclined or the center point is not aligned. In order to minimize such defects, an algorithm for correcting the center point and the inclined angle using camera image information is required. This technology detects the corner coordinates of the protective film by image processing in order to correct the positional defects where the protective film is attached. Corner point coordinates are detected using an algorithm, and center point position finds and correction values are calculated using the detected coordinates. LUT (Lookup Table) is used to quickly find out whether the angle is inclined or not. These algorithms were described by Verilog HDL. The method using the existing software requires a memory to store the entire image after processing one image. Since the method proposed in this paper is a method of scanning by adding a line buffer in one scan, it is possible to scan even if only a part of the image is saved after processing one image. Compared to those written in software language, the execution time is shortened, the speed is very fast, and the error is relatively small.

• 한국정밀공학회지
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• 제18권2호
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• pp.146-151
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• 2001

The effects of slant interface in the hybrid specimen on the dynamic crack propagation behavior have been investigated using dynamic photoelasticity. The dynamic photoelasticity with the aid of Cranz-Shardin type high speed camera system is utilized to record the dynamic stress field around the dynamically propagating inclined interface crack tip in the three point bending specimens. The dynamic load is applied by a hammer dropped from 0.08m high without initial velocity. The dynamic crack propagation velocities and dynamic stresses field around the interface crack tips are investigated. Theoretical dynamic isochromatic fringe loops are compared with the experimental reults. It is interesting to note that the crack propagating velocity becomes comparable to the Rayleigh wave speed of the soft material of a specimen when slant angle decreases.

• International Journal of Fluid Machinery and Systems
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• 제4권1호
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• pp.179-190
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• 2011

The swirling flow developing in Francis turbine draft tube under part load operation leads to pressure fluctuations usually in the range of 0.2 to 0.4 times the runner rotational frequency resulting from the so-called vortex breakdown. For low cavitation number, the flow features a cavitation vortex rope animated with precession motion. Under given conditions, these pressure fluctuations may lead to undesirable pressure fluctuations in the entire hydraulic system and also produce active power oscillations. For the upper part load range, between 0.7 and 0.85 times the best efficiency discharge, pressure fluctuations may appear in a higher frequency range of 2 to 4 times the runner rotational speed and feature modulations with vortex rope precession. It has been pointed out that for this particular operating point, the vortex rope features elliptical cross section and is animated of a self-rotation. This paper presents an experimental investigation focusing on this peculiar phenomenon, defined as the upper part load vortex rope. The experimental investigation is carried out on a high specific speed Francis turbine scale model installed on a test rig of the EPFL Laboratory for Hydraulic Machines. The selected operating point corresponds to a discharge of 0.83 times the best efficiency discharge. Observations of the cavitation vortex carried out with high speed camera have been recorded and synchronized with pressure fluctuations measurements at the draft tube cone. First, the vortex rope self rotation frequency is evidenced and the related frequency is deduced. Then, the influence of the sigma cavitation number on vortex rope shape and pressure fluctuations is presented. The waterfall diagram of the pressure fluctuations evidences resonance effects with the hydraulic circuit. The influence of outlet bubble cavitation and air injection is also investigated for low cavitation number. The time evolution of the vortex rope volume is compared with pressure fluctuations time evolution using image processing. Finally, the influence of the Froude number on the vortex rope shape and the associated pressure fluctuations is analyzed by varying the rotational speed.

• 한국음향학회지
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• 제18권2호
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• pp.66-76
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• 1999

본 논문은 스테레오 카메라를 대응점 문제가 발생하지 않을 만큼 병진 및 전진 이동시켜 고속으로 양안 시차 정보를 획득할 수 있다는 것을 제안한다. 병진 이동하는 스테레오 비전에 있어서 오차가 없고 신뢰성이 높은 시차 정보를 획득할 수 있다는 것과 전진 이동하는 스테레오 비전에 있어서는 통상의 스테레오 비전으로는 검출할 수 없는 수평성분을 획득할 수 있다는 것을 나타낸다. 또한 좌우 화상사이의 대응을 미리 한정하기 때문에 한정하지 않을 때에 비해 대응점이 밝고 작게 되므로 고속으로 스테레오 비전을 행할 수 있다. 그러나 전진 이동하는 스테레오 비전에 있어서 화상중심 부근과 폐색영역이 일치하면 바른 양안 시차 정보를 얻을 수 없는 문제가 있다.