• Journal of Institute of Control, Robotics and Systems
• /
• v.20 no.7
• /
• pp.695-700
• /
• 2014

In this paper, we utilize the CMG's momentum bias to control the roll/pitch attitude of the Quad-rotor. While the previous control approaches have used the thrust control approach, we design and add a new momentum controller (using CMG) in order to improve the transient response over the existing methods. The focal point of this paper is the design of a controller for a Quad-rotor's attitude using CMG. This leads to other tasks such as an identification of the model's parameters and mathematical nonlinear modeling. Then, the previous thrust controller is designed based on the linearized model. Finally, the overall system with our designed controller is implemented and tested in real time to show that the Quad-rotor is kept in a good balanced position faster than the traditional thrust-only control approach.

• Proceedings of the Korean Society of Laser Processing Conference
• /
• 2005.06a
• /
• pp.3-8
• /
• 2005

The robot systems are widely used in the welding manufacturing. The essential tasks to operate the welding robot are the acquisition of the position and/or shape of the parent metal. For the seam tracking or the robot automation, many kinds of contact and non-contact of the system which monitors the shape of the welding part is described. This system uses the line-type structured laser diode and the visual sensor. It includes the correction of radial distortion which is often found in the image from the camera with short focal length. Direct Linear Transformation (DLT) is used for the camera calibration. The three dimensional shape of the parent metal is obtained after simple linear transformation. Therefore, the system operates in real time. Some experiments are carried out to evaluate the performance of the developed system.

• Proceedings of the Korean Society of Broadcast Engineers Conference
• /
• 1998.06b
• /
• pp.141-146
• /
• 1998

Currently virtual studio has used the cromakey method in which an image is captured, and the blue portion of that image is replaced by a graphic image or a real image. The replaced image must be changed according to the camera motion. This paper proposes a novel method to extract camera parameters using the recognition of pentagonal patterns which are painted on the blue screen. The corresponding parameters are position, direction and focal length of the camera in the virtual studio. At first, pentagonal patterns are found using invariant features of the pentagon. Then, the projective transformation of two projected images and the camera parameters are calculated using the matched points. Simulation results indicate that camera parameters are more easily calculated compared to the conventional methods.

• Proceedings of the KSME Conference
• /
• 2004.04a
• /
• pp.1755-1760
• /
• 2004

The holographic velocimetry system has a significant potential for the measurements of three dimensional velocities of particles. In this study, orthogonal two-side holography system was developed to obtain three dimensional velocities and sizes of spray droplets. To get high quality of reconstructed images, singe-exposure holography at two time moments and two orthogonal sides was adopted instead of multi-exposure, single-side holography. From three dimensional positions of droplets determined by reconstruction and image processing system, the three dimensional velocities and sizes of each droplet was extracted using the PTV algorithm. To determine the position of particles in the optical axis, a new focusing parameter was introduced based on the correlation between two droplet images at the same distance. The measured results by holography system were compared with those by the PDPA.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.22 no.6
• /
• pp.637-642
• /
• 2002

An arc-shaped line array slit has been used for the laser generation of focused Lamb waves. The spatially expanded Nd:YAG pulse laser was illuminated through the arc-shaped line array slit on the surface of a sample plate to generate the Lamb waves of the same pattern as the slit. Then the generated Lamb waves were focused at the focal point of which distance from the slit position is dependent on the curvature of slit arc. The proposed method showed better spatial resolution than the conventional linear array slit in the detection of laser machined linear defect and drill machined circular defect on aluminum plates of 2mm thickness. Using the focused waves, we could detect the linear defect and the circular defect with the improvement of spatial resolution. The method can also be combined with the scanning mechanism to get an image just like by the scanning acoustic microscope(SAM).

• Korean Journal of Remote Sensing
• /
• v.25 no.3
• /
• pp.287-294
• /
• 2009

KOMPSAT-2 like other high-resolution satellites has the time and angle difference in the acquisition of the panchromatic (PAN) and multispectral (MS) images because the imaging systems have the offset of the charge coupled device combination in the focal plane. Due to the differences, high altitude and moving objects, such as clouds, have a different position between the PAN and MS images. Therefore, a mis-registration between the PAN and MS images occurs when a registration algorithm extracted matching points from these cloud objects. To overcome this problem, we proposed a new registration method. The main idea is to discard the matching points extracted from cloud boundaries by using an automatic thresholding technique and a classification technique on a distance disparity map of the matching points. The experimental result demonstrates the accuracy of the proposed method at ground region around cloud objects is higher than a general method which does not consider cloud objects. To evaluate the proposed method, we use KOMPSAT-2 cloudy images.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.13 no.5
• /
• pp.2414-2433
• /
• 2019

The aim of this paper is to design a 3D laser radar prototype based on laser triangulation. The mathematical model of distance sensitivity is deduced; a pixel-distance conversion formula is discussed and used to complete 3D scanning. The center position extraction algorithm of the spot is proposed, and the error of the linear laser, camera distortion and installation are corrected by using the proposed weighted average algorithm. Finally, the three-dimensional analytic computational algorithm is given to transform the measured distance into point cloud data. The experimental results show that this 3D laser radar can accomplish the 3D object scanning and the environment 3D reconstruction task. In addition, the experiment result proves that the product of the camera focal length and the baseline length is the key factor to influence measurement accuracy.

• Proceedings of the International Microelectronics And Packaging Society Conference
• /
• 2004.02a
• /
• pp.17-25
• /
• 2004

During the past few years, advances have been made in both in X-ray tube and detector technologies. The field of microfocus radioscopy has been established as an important testing process and has expanded into many new industrial applications that require quality control or process optimization. The first nanofocus and multifocus X-ray systems have become available with a focal spot of .5 micron. In the existing range of microfocus X-ray tubes, further improvements have been achieved as well, such as increased long term stability of intensity position constancy. Software, image processing and manipulation techniques have all progressed as well, allowing X-ray to become a formidable non-destructive inspection method for manufacturers in virtually every industry, especially those involved with Electronic Packaging and SMT.

• Journal of Korean Ophthalmic Optics Society
• /
• v.7 no.2
• /
• pp.197-202
• /
• 2002

In this paper, we want to help understanding about telecentric as introducing the concept of the system and researching the optical properties after we choose the designed profile projection lens. An analyzed optical system is F-number=2.8 and the first lens is used negative lens. Accordingly, we can know this system is compacter, because the front focal position is to the inside of the system and aperture stop is designed to the inside of the optical system. The field is about $21^{\circ}$. Since the entrance pupil is located the front focal point, we can certify the exit pupil is -49404.1mm, located on the infinite toward the object space. Therefore, the optical system is the form of 'image space telecentricity'.

• Publications of The Korean Astronomical Society
• /
• v.22 no.4
• /
• pp.201-209
• /
• 2007

We have preliminarily designed two infrared optical systems of the multi-purpose infrared camera system (MIRIS) which is the main payload of STSAT-3. Each optical system consists of a Cassegrain telescope, a field lens and a 1:1 re-imaging lens system that is essential for providing a cold stop. The Cassegrain telescope is identical for both of two infrared cameras, but the field correction lens and re-imaging lens system are different from each other because of different bands of wavelength. The effective aperture size is 100mm in diameter and the focal ratio is f/5. The total length of the optical system is 300mm and the position of the cold stop is 25mm from the detector focal plane. The RMS spot size is smaller than $40{\mu}m$ over the whole detector plane.