• 한국항공우주학회지
• /
• 제31권4호
• /
• pp.8-15
• /
• 2003

본 연구는 적분 방정식과 반복 "오차-수정" 개념을 이용하는 Takanashi의 이론에 기초한 초음속 실용적인 설계방법의 개발 결과로서, 형상의 수정량은 목표 압력분포와 설계대상의 압력분포와의 차를 경계조건으로 이용해 LSP 방정식을 풀므로써 계산되어진다. 이 연구에서는 Green의 정리를 이용하여 편미방정식 형태의 LSP 방정식을 적분방정식으로 변환하여 계산하는 방법을 이용하고 있다. 여기서는 Isolated wing과 wign-nacelles 두가지 경우의 설계를 예로 들었다.

• 대한기계학회논문집
• /
• 제14권3호
• /
• pp.526-533
• /
• 1990

본 연구에서는 단일 캠 구동기구의 안정성 해석을 위한 효율적인 방법이 제시 되고, 수치실험을 통하여 검증되었다. 우선 단일 캠 구동기구를 묘사하는 비선형 방 정식이 유도되고, 동안정성에 관여하는 변수들이 무차원화되어 도입된다. 유도된 방 정식은 캠 축의 입력각에 대하여 선형화되고, 선형화된 방정식에 조화균형법(harmonic balance method)을 적용하여 동안정성 해석을 수행하였다.

• Wind and Structures
• /
• 제28권2호
• /
• pp.89-97
• /
• 2019

The non-linear equations governing wind-induced internal pressures for a two-compartment building with background leakage are linearized based on some reasonable assumptions. The explicit admittance functions for both building compartments are derived, and the equivalent damping coefficients of the coupling internal pressure system are iteratively obtained. The RMS values of the internal pressure coefficients calculated from the non-linear equations and linearized equations are compared. Results indicate that the linearized equations generally have good calculation precision when the porosity ratio is less than 20%. Parameters are analyzed on the explicit admittance functions. Results show that the peaks of the internal pressure in the compartment without an external opening (Compartment 2) are higher than that in the compartment with an external opening (Compartment 1) at lower Helmholtz frequency. By contrast, the resonance peak of the internal pressure in compartment 2 is lower than that in compartment 1 at higher Helmholtz frequencies.

• 전기의세계
• /
• 제22권4호
• /
• pp.11-16
• /
• 1973

This paper presents an optimum control of the field resistance for the self-excited DC shunt generator to keep a constant terminal voltage in case of the load change or the torque variation in the system. The non-linearity of the system is linearized by applying the small signal technique and the linearized equation is solved by the maximum principle with the digital computer. The optimal control value of the field resistance for the step error of the generator output voltage is obtained and the transient voltage characteristics in the system are investigated.

• 대한공업교육학회지
• /
• 제30권2호
• /
• pp.115-122
• /
• 2005

For an analysis of dynamic behavior in carbon nanotube(CNT) which is widely used as micro and nano-sensors, an electrostatic force of CNT was investigated. For larger gaps in between sensor and electrode the van der Waals force can be ignored. The boundary condition in the CNT was assumed to clamped-clamped case at both ends. In this paper electrostatic force is expressed as linear equation along deflection using Taylor series. The first and second terms(${\zeta}_0$ and ${\zeta}_1$) of the linear equation are analyzed. Based on the simulation results nondimensional number ${\Phi}_0$ and ${\Phi}_1$ which came from ${\zeta}_0$ and ${\zeta}_1$ were decreased according to the increment of the gap. Reduction ratio of the second term ${\zeta}_1$ is increased up to 99% along to the increment of the gap. The higher order terms can be ignored and therefore, electrostatic force can be expressed using the first two terms of the linear equation. This results play an important role in analyzing the nonlinear dynamic behavior of the CNT as well as the pull-in voltage of simply supported switches.

• 대한기계학회논문집A
• /
• 제21권7호
• /
• pp.1106-1115
• /
• 1997

A method of obtaining a control input to reduce residual vibration was developed for nonlinear time-varying systems moving along pre-determined two dimensional paths. First, the nonlinear system equation was solved with nominal input then linearized by nominal response which is defined at equilibrium point. Next an additional input can be obtained by solving the linearized equation that should satisfied the required boundary conditions. Residual vibration reduction was experimentally verified by applying the control input, which is sum of nominal and additional input, to a moving pendulum whose length is varying time.

• 한국정밀공학회지
• /
• 제6권1호
• /
• pp.33-44
• /
• 1989

A controller disign method is proposed for multivariable nonlinear stochastic systems with hard nonlinearities such as Coulomb friction, backlash and saturation. In order to take the nonlinearities into account statistical linearization techniques are used. And multi- variable pole placement techniques are applied to design controller for the statistically linearized multivariable systems. The basic concept of the controller design method is to solve two coupled equations, characteristic equation and Lyapunov equation, simultaneously and iteratively for statistically linearized multivariable stochastic systems. An aircraft with saturation serves as a design example. The design example illustrates the influence of nonlinear effects. The results of the analysis are compared to Monte Carlo simulation to test their accuracy.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2005년도 춘계학술대회논문집
• /
• pp.983-986
• /
• 2005

Free vibration characteristics of a curved pipe conveying fluid is studied when the pipe is clamped at both ends. Using the perturbation method, the non-linear governing equations divided into two parts; the steady state non-linear equilibrium equations and the linearized equations of motion in the neighborhood of the equilibrium position. The natural frequencies are computed from the linearized equations of motion. In this study, the equilibrium positions are determined by two types of equations, i.e., (1) the non-linear equations, and (2) the equations obtained by neglecting the non-linear terms. The natural frequencies obtained from the non-linear equilibrium equations are compared to those obtained from the linearized equilibrium equations. From the results, as the fluid velocity increases, the equilibrium position should be determined from the nonlinear equations for the vibration analysis of the curved pipe conveying fluid.

• 전력전자학회논문지
• /
• 제19권6호
• /
• pp.530-537
• /
• 2014

A controller design method for a battery-energy storage system using a linearized battery model is presented in this paper. The suggested linear battery model is expressed with open-circuit voltage having three relaxation filters and a linear output equation. A method to obtain on-line resistance and maximum available power is also presented. The battery state of charge information is obtained by Kalman filter, and its performance is verified by FTP75 driving cycles. The controller for power converter is designed and experimented with a 250 V battery pack. The proposed control method is simple and easy to apply to a real system.

• 대한전기학회논문지
• /
• 제39권8호
• /
• pp.792-804
• /
• 1990

This paper describes an efficient optimization algorithm by calculating sensitivity function for power system stabilization. In power system, the dynamic performance of exciter, governor etc. following a disturbance can be presented by a nonlinear differential equation. Since a nonlinear equation can be linearized for small disturbances, the state equation is expressed by a system matrix with system parameters. The objective function for power system operation will be related to the system parameter and the initial state at the optimal control condition for control or stabilization. The object function sensitivity to the system parameter can be considered to be effective in selecting the optimal parameter of the system.