• The KSFM Journal of Fluid Machinery
• /
• v.6 no.4 s.21
• /
• pp.29-37
• /
• 2003

This study was undertaken to verify the effect of flow coefficient when a globe control valve was attached by different type of fitting. The valve flow coefficient is usually determined by measuring the flow rate and the pressure drop with the connection of straight pipe through the valve. The effect of different fitting that is mounted on the downstream of the valve is studied. Four types of fittings and three distances between the valve and a downstream fitting are compared parametrically to investigate the effect on the flow coefficient of it. Measured flow coefficient and numerically predicted value by using computational fluid dynamics were compared in detail. It is concluded that the flow coefficient is reduced if the fitting is attached after a valve, but the effect of different type of fitting is not crucial.

• Journal of Institute of Control, Robotics and Systems
• /
• v.12 no.3
• /
• pp.300-306
• /
• 2006

In this paper an error analysis of 3-dimensional GNSS attitude determination system is given. The attitude error covariance matrix is derived and analyzed. It implies that attitude errors are affected by the baseline length and configuration, the satellites numbers and geometry, receiver measurement noises and the nominal attitude of the vehicle. By defining Euler Angle Dilution Of Precision (EADOP) which is analogous to GDOP, roll, pitch and yaw errors can be efficiently analyzed. However the expression of the attitude error is too complex to get some intuitions. Therefore with a commonly adopted assumption, new expressions for attitude error are derived. The formulas are easy to compute and represent the attitude error as a function of the nominal attitude of a vehicle, the baseline configuration and the receiver noise. Using the formula, the accuracy of the attitude can be analytically predicted without the computer simulations. Applications to some widely used configurations reveal the effectiveness of the proposed method.

• Proceedings of the KIEE Conference
• /
• 1997.07b
• /
• pp.542-544
• /
• 1997

The analysis of distribution line faults is essential to the proper protections in the power system. A high impedance fault does not make enough current to cause conventional protective devices. In this paper, Fractal dimensions are estimated for distinction between normal status and fault status in the power system. Application of the concepts of the fractal geometry to analyze chaotic properties of high impedance fault current was described. In addition, to analyze variation of fault current and normal current on phase plane, embedding state variables are reconstructed from 1 dimensional time series.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.24 no.6 s.177
• /
• pp.1520-1528
• /
• 2000

This study presents a method for determining bearing stiffness and damping coefficients of air-lubricated slider bearing, and shows influences of air-bearing surface geometry(recess depth, crown an d pivot location) on flying attitude and dynamic characteristics. To derive the dynamic lubrication equation, the perturbation method is applied to the generalized lubrication equation which based on linearized Boltzmann equation. The generalized lubrication equation and the dynamic lubrication equation are converted to a control volume formulation, and then, the static and dynamic pressure distributions are calculated by finite difference method. The recess depth and crown of the slider show significantly influence on flying attitude and dynamic characteristics comparing with those of pivot location.

• 한국정보디스플레이학회:학술대회논문집
• /
• 2003.07a
• /
• pp.1147-1150
• /
• 2003

When a braun tube becomes wider, one of the major problems to be experienced is the non-uniform coating along the four diagonal directions on its surface. This non-uniformity in the coating thickness has a deep relation with the fluid flow on the surface of a braun tube. In order to control the fluid flow properly, we install the plate to block fluid flow at the corner of a braun tube. In the present study, we investigate the effects of the geometry of plate to control the fluid flow and coating uniformity and determine the optimal shape of plate to improve the quality of coating uniformity.

• 제어로봇시스템학회:학술대회논문집
• /
• 2001.10a
• /
• pp.63.3-63
• /
• 2001

Inspection and shape measurement of three-dimensional objects are widely needed in industries for quality monitoring and control. In this paper, we propose a three dimensional volume reconstruction method, which is an iterative method and as uniform and simulated algebraic reconstruction technique (USART). In this method, two or more x-ray images projected from different views are needed, and also the geometry of the imaging system need to be a priori identified well. That is to say, the relative locations between the x-ray source, imaging plane and the object should be determined exactly by calibration. To achieve this, we propose a series of coordinate calibration methods of the x-ray imaging system using grid pattern images. Some experimental results of these calibrations is presented and discussed in detail ...

• 제어로봇시스템학회:학술대회논문집
• /
• 2002.10a
• /
• pp.41.4-41
• /
• 2002

In this paper we deal with visual servoing that can control a robot arm with a camera using information of images only, without estimating 3D position and rotation of the robot arm. Here it is assumed that the robot arm is calibrated and the camera is uncalibrated. Here we consider two coordinate systems, the world coordinate system and the camera coordinate one and we use a pinhole camera model as the camera one. First of all, the essential notion can be show, that is, epipolar geometry, epipole, epipolar equation, and epipolar constrain. And these plays an important role in designing visual servoing in the later chapters. Statement of the problem is giver. Provided two a priori...

• 제어로봇시스템학회:학술대회논문집
• /
• 2002.10a
• /
• pp.97.4-97
• /
• 2002

1. Introduction Pose estimation of a three dimensional object has been studied in robot vision area, and it is needed in a number of industrial applications such as process monitoring and control, assembly and PCB inspection. In this research, we propose a new pose estimation method based on principal axes analysis. Here, it is assumed that the locations of x-ray source and the image plane are predetermined and the object geometry is known. To this end, we define a dispersion matrix of an object, which is a discrete form of inertia matrix of the object. It can be determined here from a set of x-ray images, at least three images are required. Then, the pose information is obtained fro...

• 제어로봇시스템학회:학술대회논문집
• /
• 1991.10a
• /
• pp.252-257
• /
• 1991

This paper proposed that the eddy-current measurement method can be used a means of in-process measuring the hardening depth in Laser surface treatment process. Also, this paper deal with the numerical analysis of magnetic flux distribution and experimental result of measurement. In Laser heat treatment process of steels, a thin layer of the substrate is rapidly heated to austenitizing temperature and subsequently cooled at a very fast rate due to the self-quenching by heat conduction into the bulk body, to produce a martensite structure which have low magnetic permeability. The eddy-current measurement method depends on the properties of material to be measured such as electric conductivity, magnetic permeability and geometry. In this paper, the hardening depth was measured by detecting relevant magnetic permeability changes caused by heat treatment of steels.

• Journal of computational fluids engineering
• /
• v.6 no.3
• /
• pp.27-31
• /
• 2001

For rapid and abrupt control of a missile in supersonic flight, side jet on a missile body is found to be a useful device as evidenced by recent missile development at several nations. The magnitude of the side jet and the duration of it decide the level of control of such a missile system. In this paper, the aerodynamic characteristics of the side jet device itself are examined in terms of key parameters such as the side jet nozzle geometry, the chamber pressure and temperature. Specifically attention is paid to the effect of the chamber shape between the straight nozzle and the bent nozzle by 90 degrees on the nozzle flow properties. The thrust magnitudes are compared between the two shapes. Whether the way the nozzle is bent at the joint affects the nozzle performance is also investigated. Effects of the length and the divergence angle of the nozzle on the thrust are also quantified among three different side jet nozzles.