• Journal of the Earthquake Engineering Society of Korea
• /
• v.3 no.2
• /
• pp.87-96
• /
• 1999

To analyze the dynamic behavior of structure, direct integration and mode superposition may be utilized in time domain analysis. As finite number of frequencies can give relatively exact solutions, mode superposition is preferable in analyzing structural behavior. In non-linear analysis, however, mode superposition is seldom used since time-varying element stiffness changes stiffness matrix, and the change of stiffness matrix leads to the change of essential constants - natural frequencies and mode shapes. In spite of these difficulties, there are some attempts to adopt mode superposition because of low cost compared to direct integration, but the result is not satisfactory. In this paper, a method using mode superposition in non-linear analysis is presented by separating local element stiffness from global stiffness matrix with the difference between linear and non-linear restoring forces to the external force vectors included. Moreover, the hysteresis model changing with the relative deformation in each floor makes it possible to analyze non-linear behavior of structure. The proposed algorithm is applied to shear beam model and the maximum displacement is compared with the result using direct integration method.

• Journal of the Korean Institute of Intelligent Systems
• /
• v.16 no.4
• /
• pp.506-511
• /
• 2006

This paper considers a method to design sliding mode observers for a class of uncertain systems using Linear Matrix Inequalities(LMI). In an LMI-based sliding mode observer design method for a class of uncertain systems the switching surface is set to be the difference between the observer and system output. In terms of LMIs, a necessary and sufficient condition is derived for the existence of a sliding-mode observer guaranteeing a stable sliding motion on the switching surface. The gain matrices of the sliding-mode observer are characterized using the solution of the LMI existence condition. The results are illustrated by an example.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.31 no.8A
• /
• pp.790-797
• /
• 2006

IEEE 802.16e specifies two different power saving modes(PSM). One is sleep mode and the other is idle mode. These modes are different in that whether a mobile node maintains its state information with the serving base station or not. This difference results in different efficiency in consuming battery power of a mobile terminal. Therefore, it becomes important to analyze the performance of each power saving mode considering the parameters affecting the power consumption. In this paper, we propose a performance modeling framework of sleep mode and idle mode in terms of power saving efficiency. The analytical results are verified by computer simulations that idle mode is superior to sleep mode in power consumption of mobile node.

• Journal of Advanced Navigation Technology
• /
• v.9 no.2
• /
• pp.185-192
• /
• 2005

The aim of this paper is to analyze handling qualities of tiltrotor aircraft(TR-S4) in helicopter flight mode including hovering and forward flight. Analysis of handling qualities is composed of aircraft response to control inputs that effect on stability and controllability. In short term response analysis, bandwidth is the critical parameter for small amplitude motions since it relates to the ability of a pilot to crisply start and stop maneuver. The handling qualities of TR-S4 in helicopter mode are analyzed with a SAS and an attitude controller and are satisfied level 1 in almost criteria with simulation of TR-S4 6-DOF nonlinear model.

• Journal of Aerospace System Engineering
• /
• v.16 no.4
• /
• pp.88-94
• /
• 2022

The vibration mode measurement test measures the natural vibration characteristics of the target specimen. The measured natural mode characteristics are compared with the numerical analysis result to verify the reliability of the numerical analysis. If necessary, it is used to supplement the numerical analysis model of the specimen used for the dynamic characteristic analysis. In this paper, the natural frequency and natural mode of the external fuel tank are respectively obtained through the vibration mode measurement test and the numerical analysis, using the finite element model. The results are compared to verify the reliability of the numerical analysis model of the external fuel tank to apply to the entire aircraft model. To measure the vibration mode of the test specimen, a bungee cord was used, to simulate the free boundary condition for the test specimen. And, 3-axis accelerometers were installed on the test specimen. The response characteristics of the test specimen were measured, by excitation with an impact hammer. As a result of the test, after performing the frequency response analysis on the response acceleration, the natural frequency of the test specimen and its vibration mode were confirmed. The reliability of the numerical analysis model was verified by comparing the frequency and vibration mode, obtained through the test and the numerical analysis.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.36 no.12
• /
• pp.1201-1206
• /
• 2008

This study is focused on the investigation of the modal characteristics of the preliminary models of science technology satellite-3 (STSAT-3). Prior to the final decision of the composite structure model, several candidate structure models have been developed so as to find the most qualified structures with respect to the satellite structure systems' requirements and then utilize the information achieved to a real design. The main structure is composed of fiber reinforced composite faced honeycomb sandwich panel whose modal characteristics are found and compared to each other by means of finite element numerical analyses. Results from the current study demonstrate that a rectangular box shape having supporting inner panel shows relatively higher fundamental mode frequencies than octagonal box shape and etc., and regardless of the structure model shape tested herein, the fundamental mode turns out lateral bending mode.

• Proceedings of the KIPE Conference
• /
• 2004.07b
• /
• pp.752-755
• /
• 2004

본 논문에서는 전력변환회로의 소신호 모델을 이용한 데드빗 전류모드제어기를 설계하였다. 소신호 모델을 이용함으로써 부스투, 벅, 벅-부스트 컨버터에 모두 적용 가능한 데드빗 전류모드제어기를 설계 가능하고, 설계한 제어기는 모든 시비율 동작 조건에서 안정함을 확인하였다. 16bit 마이크로컨트롤러인 80C196KC를 사용하여 설계된 디지털 제어기를 구현하고, 아날로그제어기를 이용한 전류모드 제어에서의 동작 조건에 따른 불안정성 문제를 해결할 수 있음을 실험을 통해 확인하였다.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.41 no.6
• /
• pp.448-457
• /
• 2013

This paper presents the design of an active flutter suppression system for flexible wing using sliding mode control method. The aerodynamic force generated by the motion of a flexible wing control surface is utilized as control force. For this purpose, aeroservoelastic model is formulated by blending aeroelastic model, control surface actuator model, and gust model. A sliding mode controller is designed for active flutter suppression on the aeroservoelastic model in conjunction with Kalman filter that estimates the system states based on the measured output. The performance of the designed controller is demonstrated via numerical simulation for the representative flexible wing model.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.7 no.3
• /
• pp.241-248
• /
• 1987

The theoretical backgrounds of the several methods were surveyed and reviewed to fin out the adequate one to determine equivalent modal damping values in solving the dynamic problem of soil-structure interaction by mode superposition method. Furthermore the rigorous damping matrix of equation of motion was obtained through component mode synthesis technique and used in direct integration of the equation. The analytical results by direct integration method were compared with those of mode superposition approach using the various sets of equivalent modal damping values calculated by the methods to be reviewed. Two types of superstructures and four kinds of subsurface conditions were considered and combined to make soil-structure coupled models. It was realized that dissipating energy method gives the equivalent modal damping values which lead the most similar results to direct integration ones. In case of fixed base, the responses of all methods except stiffness weighted approach are almost equal to those of direct integration method.

• Broadcasting and Media Magazine
• /
• v.7 no.3
• /
• pp.24-34
• /
• 2002

본 논문에서는 현재 ITU-T와 ISO에 의해서 공동으로 표준화 작업이 진행되고 있는 H.264 ｜ MPEG-4 Part 10표준의 주요 테스트 모델 사항들에 대해서 특징을 서술하고 그 기능을 설명하고자 한다. 대표적인 테스트 모델 사항으로서는 RD 최적화 및 변환을 이용한 부호 모드 결정 기법, 오류 내성을 가지는 부호 모드 결정 기법 등을 들 수 있다. 현재 대역폭 제어 및 고속 움직임 추정에 관한 사항들이 테스트 모델의 발전을 위한 주요 과제로 연구가 진행되고 있다.