• 전자공학회논문지T
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• 제35T권3호
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• pp.76-86
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• 1998

2관성 공진(TMS: Two-Mass Spring) 시스템은 비틀림 진동을 다루기 위하여 고려할 수 있는 가장 간단한 모델이다. 이러한 시스템은 비틀림 진동을 억제하며, 원하는 특성을 달성하기 위한 제어기 설계가 요구된다. 본 논문에서는 2관성 공진 시스템에 대하여 상태 피드백을 고려하고, 각 상태가 응답성능에 미치는 영향을 살펴본다. 이 결과와 상태 피드백의 이득을 이용하여 제어기의 설계 매개변수와 LQ 및 H/sub ∞/ 제어의 하중함수 결정에 대한 기본 지침을 제시한다.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2004년도 학술대회지
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• pp.271-276
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• 2004

In this paper. dynamic behavior of the cracked beam under a moving mass is presented using the finite element method (FEM). Model accuracy is improved with the following consideration: (1) FE model with Timoshenko beam element (2) Additional flexibility matrix due to crack presence (3) Interaction forces between the moving mass and supported beam. The Timoshenko bean model with a two-node finite element is constructed based on Guyan condensation that leads to the results of classical formulations. but in a simple and systematic manner. The cracked section is represented by local flexibility matrix connecting two unchanged beam segments and the crack as modeled a massless rotational spring. The inertia force due to the moving mass is also involved with gravity force equivalent to a moving load. The numerical tests for various mass levels. crack sizes. locations and boundary conditions were performed.

• 대한조선학회지
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• 제13권4호
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• pp.1-10
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• 1976

It is a well-known phenomenon that, in the case of vibrations of an elastic body in a fluid such as water, the presence of the surrounding fluid has the effect of lowering the natural frequencies of the vibration as compared with those in air or vacuum on account of the increased inertia, i.e. added mass. In this report, defining the mass increase factor as the ratio of added mass to vibration mass of the body in air, the author investigated the mass increased factor of an elastic plate vibrating in the fluid. It is assumed that the edges of the plate are simply supported, and that the surrounding fluid is an infinite ideal one. For the problem formulation the elliptical cylindrical coordinate system is adopted, so that a rectangular plate may be represented by a sheet degenerated from an elliptical cylinder. By virtue of the coordinate system adopted, plates which are chordwisely finite and lengthwisely contineous could directly be treated, but plates which are chordwisely finite in both directions could not be treated directly. For the latter, hence, plates which are chordwisely finite and lengthwisely semi-finite are investigated as an appropriate approximation. Some examples of the mass increase factor are numerically calculated for the fundamental mode and modes of zero or one nodal line in each direction with the range of the aspect ratio from 1 to 10 or more.

• 한국분무공학회지
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• 제1권1호
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• pp.63-75
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• 1996

The purpose of this study is to investigate the break-up characteristics by taking advantage of a two-phase coaxial nozzle. Air and water are utilized as working fluids and the mass ratio air/water has been controlled to characterize the atomization, diffusion and development of mixing process. By way of a photographic technique, conventional developing structures and diffusion angles have been analyzed systematically with variations of mass ratios. The turbulent flow components of the atomized particles were measured by a two channel LDV system and the data were treated by an on-lined measurement equipment. According to the photographic results the spreading angles decreased because the axial inertia moment was relatively higher than the lateral one with respect to the increase of mass ratio. It is found the jet flow diffuses linearly in a certain limit region while the atomizing characteristics, in terms of the distributions of particle diameters did not show particular differences. It may be expected that these fundamental results can be used as reference data in studying the atomization, breakup and diffusions.

• 전기학회논문지
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• 제56권4호
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• pp.730-738
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• 2007

As well known when the linear machine is operated between two points repeatedly under positioning control, there are various positioning error at the moment of zero speed owing to the non-linear disturbance like as unpredictable friction force. To remove this positioning error, a simple least order disturbance observer is introduced and is actually implemented in this study. Due to this simple algorithm the over-all machine system can be modified to simple arbitrary given one-mass load without any disturbance. So, the total construction process for positioning control system is much easier than old one. Moreover, to generate a proper effective position profile with the limited actual machine force, a very powerful on-line mass identification algorithm using the load force estimator is presented. In the proposed mass identification algorithm, the exact load mass can be calculated during only one moving stage under a normally generated position profile. All presented algorithm is verified with experimental result with commercial linear servo machine system.

• 한국소음진동공학회논문집
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• 제26권3호
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• pp.281-289
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• 2016

In this paper, a new dynamic model for modal analysis of a rotating cantilever beam with a tip-mass is developed. The nonlinear strain such as von Karman type and the corresponding linearized stress are used to consider the geometric nonlinearity, and Euler-Bernoulli beam theory is applied in the present model. The nonlinear equations of motion and the associated boundary conditions which include the inertia of the tip-mass are derived through Hamilton's principle. In order to investigate modal characteristics of the present model, the linearized equations of motion in the neighborhood of the equilibrium position are obtained by using perturbation technique to the nonlinear equations. Since the effect of the tip-mass is considered to the boundary condition of the flexible beam, weak forms are used to discretize the linearized equations. Compared with equations related to stiffening effect due to centrifugal force of the present and the previous model, the present model predicts the dynamic characteristic more precisely than the another model. As a result, the difference of natural frequencies loci between two models become larger as the rotating speed increases. In addition, we observed that the mode veering phenomenon occurs at the certain rotating speed.

• 대한전기학회논문지:시스템및제어부문D
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• 제49권1호
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• pp.18-25
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• 2000

In the two-mass servo system driving a load through a flexible shaft, a shaft torsional vibration is often generated. PI controller has been generally used is speed control of such system because of the simplicity of structure and related theory. This paper presents the inertia ratio of the PI servo control system which can be designed by using optimal pole assignment method is fixed. Therefore, it's difficult to obtain the desired control characteristics for different systems only by PI control algorithm. To solve this problems the two-mass speed control system with PID controller is designed by using pole assignment method and an optimum PID parameters are derived by evaluating ITAE(Integral of time multiplied by the absolute error) performance index. But this design method has some problems due to a trade-off between the fast command following property and the attenuation of disturbances and vibrations. In this paper, 2-DOF PID control method which satisfies the command following property, the reduction of overshoot and the property of disturbance rejection at the same time is proposed. This is a practical speed controller using the desired value filter and the feedforward gain. From several simulations, it's clarified that the proposed 2-DOF PID controller is useful for the two-mass system, in comparison with the conventional PID controller.

• 한국생산제조학회지
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• 제21권1호
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• pp.182-189
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• 2012

This study suggests a dynamic design process for deciding properly design parameters of a mass-spring type Wave Energy Converter (WEC) to achieve sufficient energy conversion from wave to power generator. The WEC mechanism, in this research, consists of a rigid sprung body, a platform, suspension springs and dampers. The rigid sprung body is supported on the platform via springs and dampers and vibrates translationally in the heave direction under wave excitation. At last the resulting heave motion of the sprung body is transmitted to rotating motion of the electric generator by rack and pinion, and transmission gears. For the purpose of vibration analysis, the WEC mechanism has been simply modelled as a mass-spring-damper system under harmonic base excitation. Its maximum displacement transmissibility and steady state response can be determined by using elementary vibration theory if the harmonic ocean wave data were provided. With the vibration analysis results, the suggested dynamic design process of WEC can determine all the design parameters of the WEC mechanism, such as sprung body mass, suspension spring constant, and damping coefficient that can give sufficient relative displacement transmissibility and the associated inertia moment to drive the electric generator and transmission gears.

• Structural Engineering and Mechanics
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• 제54권6호
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• pp.1217-1244
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• 2015

In this research a theoretical and numerical study on a bridge damage detection procedure is presented based on vibration measurements collected from a set of accelerometers. This method, referred to as "Adjoint Variable Method", is a sensitivity-based finite element model updating method. The approach relies on minimizing a penalty function, which usually consists of the errors between the measured quantities and the corresponding predictions attained from the model. Moving mass is an interactive model and includes inertia effects between the model and mass. This interactive model is a time varying system and the proposed method is capable of detecting damage in this variable system. Robustness of the proposed method is illustrated by correct detection of the location and extension of predetermined single, multiple and random damages in all ranges of speed and mass ratio of moving vehicle. A comparative study on common sensitivity and the proposed method confirms its efficiency and performance improvement in sensitivity-based damage detection methods. In addition various possible sources of error, including the effects of measurement noise and initial assumption error in stability of method are also discussed.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1995년도 추계학술대회 논문집
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• pp.337-341
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• 1995

This paper presents a robust control scheme using a multilayer network for the robot manipulator operating under the sea which has large uncertainties such as the buoyancy and the added mass/moment of inertia. The multilayer neural network acts as a compensator of the conventional sliding mode controller to maintain the control performance when the initial assumptions of uncertainty bounds are not valid. By the computer simulation results, the proposed control scheme dose not effectively compensate large uncertainties, but also reduces the steady stare error of the conventional sliding mode controller.