• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.35 no.4
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• pp.295-301
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• 2007

The aeroelastic characteristics of a wing with control surface freeplay are investigated. The transonic small disturbance equation is used for unsteady aerodynamic forces in subsonic/transonic region. The fictitious mass method is introduced to apply a modal approach to nonlinear structural models. Nonlinear aeroelastic time responses are calculated by the coupled time integration method. Using these methods, an efficient aeroelastic analysis is achieved for aerodynamic and structural nonlinearities simultaneously. The effects of the aerodynamic nonlinearity, initial flap amplitude, and freeplay magnitude in aeroelastic characteristics are investigated in this study.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.35 no.11
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• pp.999-1005
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• 2007

In case of an abnormal condition of control surface, the real-time estimation of aerodynamic derivatives are required for the reconfigurable control system to be flight for missions or return to the head office. The goal of this paper is to represent a technique of fault detection to the control surface as a base research to the fault tolerant control system for safety improvement of UAV. The real-time system identification for the fault detection to the control surface was applied with the recursive Fourier Transform and verified through the HILS and flight test. The failures of the control surface are detected by comparing the control derivatives in fault condition with the normal condition. As a result from the flight test, we have confirmed that the control derivatives of fault condition less than about 50% in the normal condition.

• International Journal of Aeronautical and Space Sciences
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• v.13 no.3
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• pp.361-368
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• 2012

This paper presents an approach on the design of a nonlinear controller to track a reference velocity for an air-breathing supersonic vehicle. The nonlinear control scheme involves an adaptation of propulsive and aerodynamic characteristics in the equations of motion. In this paper, the coefficients of given thrust and drag functions are estimated and they are used to approximate the equations of motion under varying flight conditions. The form of the function of propulsive thrust is extracted from a thrust database which is given by preliminary engine input/output performance analysis. The aerodynamic drag is approximated as a function of angle of attack and fin deflection. The nonlinear controller, designed by using the approximated nonlinear control model equations, provides engine fuel supply command to follow the desired velocity varying with time. On the other hand, the stabilization of altitude, separated from the velocity control scheme, is done by a classical altitude hold autopilot design. Finally, several simulations are performed in order to demonstrate the relevance of the controller design regarding the vehicle.

• Journal of Korea Multimedia Society
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• v.21 no.6
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• pp.698-704
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• 2018

When the new ammunition is designed, it is necessary to confirm in advance how long the target distance is depends on the shape and weight of the designed ammunition. Therefore we can use commercial software such as PRODAS to predict the target distance in the design stage. This commercial software has aerodynamic data for various ammunition shape and calculates the target range by calculating the kinetic equations of the ammunition using the aerodynamic data most similar to the designed ammunition. The ammunition for predicting the target distance through software such as PRODAS is a non-guided ammunition that has no control after launch but the glide type ammunition is guided and control ammunition. So it is predicts the state of ammunition after the launch. A new type of simulator is needed to analyze the maximum range and to verify the onboard guided and control algorithm. The simulator constructed in this paper is an optimized simulator for glide type ammunition. Unlike unmanned aircraft and guided missiles. The rotation characteristics of the ammunition are considered and the navigation initialization algorithm is applied. The constructed simulator confirmed the performance by performing maximum range analysis of glide type ammunition.

• Journal of Institute of Control, Robotics and Systems
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• v.11 no.1
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• pp.58-66
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• 2005

Usual human gait can be modeled as continual impact phenomenon that happens due to the topological change of the kinematic structure of the two feet. The human being adapts his own control algorithm to minimize the ill effect due to the collision with the environment. In order to operate a Humanoid robot like the human being, it is necessary to understand the physics of the impact and to derive an analytical model of the impact. In this paper, specially, we focus on impact analysis of the kicking motion in playing soccer. At the instant of impact, the external impulse exerted on the ball by the foot is an important property. Initially, we introduce the complete external impulse model of the lower-extremity of the human body and analyze the external impulses for several kicking postures of the lower-extremity. Secondly, a trajectory-planning algorithm of a ball, in which the initial velocity and the launch angle of the ball are calculated for a desired trajectory of the ball, will be introduced. The aerodynamic effect such as drag force and lift force is also considered. We carry out numerical simulation and experimentation to verify the effectiveness of the proposed analytical methodology.

• Journal of the Korea Institute of Military Science and Technology
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• v.10 no.2
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• pp.188-197
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• 2007

Active flow control, in the form of steady and unsteady momentum injection via jet blowing was studied. A jet was obtained by pressing a plenum inside the airfoil and ejecting flow out of a thin slot. The normal and drag forces were measured with leading edge or trailing edge blowing Jet and compared with the results obtained with no blowing. The blowing jet has been shown to improve the aerodynamic performance of the airfoil. The steady jet proved more effective than pulsating jet in these experimental conditions. Furthermore for the case of leading edge steady blowing jet, the alleviation of non-linearity in the normal force curve slope can be seen at higher angles of attack. No effective trailing edge jet was observed in this highly separated flow. This shows that the stall control is highly depends on the characteristics of the boundary layer near the jet slot.

• Wind and Structures
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• v.35 no.3
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• pp.193-211
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• 2022

The present study focuses on aerodynamic parameters behaviors and control on the single and double side setback building models at the buildings mid-height. The study is conducted by computational fluid dynamics (CFD) simulation. This study estimates the face wise pressure coefficient on single side setback buildings with a setback range of 20%-50% and double side setback buildings with setbacks ranging from 10%-25%. The polynomial fitted graphs from CFD data predict the Cp on different setback model faces within permissible limit ±13% error. The efficient model obtained according to the minimum drag, lift, and moment consideration for along and across wind conditions. The study guides the building tributary area doesn't control the drag, lift, and moment on setback type buildings. The setback distance takes a crucial role in that. The 20% double side setback model is highly efficient to regulate the moment for both along and across wind conditions. It reduces 17.5% compared to the 20% single side setback and 14% moment compared to the 10% double side setback models. The double side setback building is more efficient to control 4.2% moment than the single side setback building

• Journal of the Korea Institute of Military Science and Technology
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• v.11 no.2
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• pp.144-151
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• 2008

An experimental study has been conducted to investigate the effects of circular damage hole on the characteristics of airfoil performance. The damage on a wing created from a hit by anti-air artillery was modeled as a circular hole. Force balance measurements and static pressure measurements on the wing surface were carried out for the cases of having damage holes of 10% chord size at quarter chord and/or half chord positions. All experiments were conducted at Reynolds number of $2.85\times10^5$ based on the chord length. The surface pressure data show big pressure alterations near the circular damage holes. This abnormal surface pressure distribution produces shear stress that could lead to the acceleration of the structural degradation of the wing around the circular damage hole. However, in spite of the existence of circular damage holes, the measured force data indicated the only a slight decrease in lift accompanied by increase in drag compared to the results of undamaged one. The influence of damage hole on the aerodynamic performance was increased as the location of damage moved to the leading edge. The effect on the control force was insignificant when the damaged size was not large.

• Journal of the Korean Society of Propulsion Engineers
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• v.8 no.1
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• pp.70-80
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• 2004

This study proposes a development result for the 1-kW class small wind turbine system, which is applicable to relatively low wind speed regions like Korea and has the variable pitch control mechanism. In the aerodynamic design of the wind turbine blade, parametric studies were carried out to determine an optimum aerodynamic configuration which is not only more efficient at low wind speed but whose diameter is not much larger than similar class other blades. A light composite structure, which can endure effectively various loads, was newly designed. In order to evaluate the structural design of the composite blade, the structural analysis was peformed by the finite element method. Moreover both structural safety and stability were verified through the full- scale structural test.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11b
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• pp.914-920
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• 2002

Nonlinear flow-induced vibration characteristics of a generic missile wing (or control surface) are investigated in this study. The wing model has freeplay structural nonlinearity at its pitch axis. Nonlinear aerodynamic flows with unsteady shock waves are considered in the transonic flow region. To practically consider the effects of freeplay structural nonlinearity, the fictitious mass method (FMM) is applied to structural vibration analysis based on a finite element method (FEM). A computational fluid dynamics (CFD) technique is used for computing the nonlinear unsteady aerodynamics of all-movable wings. The aerodynamic analysis is based on the efficient transonic small-disturbance aerodynamic equations of motion using the potential-flow theory. To solve the nonlinear aeroelastic governing equations including the freeplay effect, a modal-based computational structural dynamic (CSD) analysis technique based on fictitious mass method (FMM) is used in time-domain. In addition, CSD and unsteady CFD techniques are simultaneously coupled to give accurate computational results. Various aeroelastic computations have been performed for a generic missile wing model. Linear and nonlinear aeroelastic computations have been conducted and the characteristics of flow-induced vibration are introduced.