• Title/Summary/Keyword: mass moment of inertia

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Flapwise Bending Vibration of Rotating Timpshenko Beams with Concentrated Mass and Mass Moment of Inertia (집중 질량및 관성 모멘트를 갖는 회전하는 티모센코 보의 면외굽힘 진동)

  • 박정훈;유홍희
    • Journal of KSNVE
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    • v.8 no.2
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    • pp.353-360
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    • 1998
  • In this paper, a modeling method for the bending vibration analysis of rotating Timoshenko beams with concentrated mass and mass moment of inertia is presented. The shear and rotary inertia effects become critical for the accurate estimation of the natural frequencies and mode shapes as the slenderness ratio decreases. The natural frequencies obtained by using the Timoshenko beam theory are lower than those by using the Euler beam theory. The critical angular speed, which does not exist only with the concentrated mass, exists with the concentrated mass moment of inertia.

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The Study on the Added Moment of Inertia of Two Dimensional Cylinder induced by the Torsional Vibration coupled with the Flexural Vibration (자유수면(自由水面)에서의 비틀림 수평(水平)굽힘의 연성진동(連成振動)을 하는 선체단면형(船體斷面形)의 이차원적(二次元的) 부가관성(附加慣性) Moment에 관(關)한 연구(硏究))

  • S.S.,Kim
    • Bulletin of the Society of Naval Architects of Korea
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    • v.7 no.2
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    • pp.3-18
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    • 1970
  • An investigation was made for the added mass moment of inertia induced by the rotational motion of the cylinder with hull section on water in order to obtain the information to estimate the natural frequency of the torsional vibration of ships. The special consideration to the effect of the draught upon the added mass moment of inertia is taken into account in the study. In this paper, the general expression for the added mass coefficients of moment of inertia of arbitary two dimensional forms induced by the torsional vibration, was derived by the author. Hence, the coefficients for these forms are represented as functions of parameters, the section area coefficient and draft beam ratio, from which the added mass coefficients for arbitrary forms can be obtained. The result was shown in a chart for estimation of the added mass moment of inertia induced by the torsional vibration, as first trial, for the convenience of practical use.

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Flapwise Bending Vibration of Rotating Timoshenko Beams with Concentrated Mass Moment of Inertia (집중 질량 및 관성모멘트를 갖는 회전하는 티모센코 보의 면외굽힘 진동)

  • 박정훈;유홍희
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 1997.10a
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    • pp.110-115
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    • 1997
  • A modeling method for the bending vibration analysis of rotating Timoshenko beams with concentrated mass and mass moment of inertia is presented. The shear and rotary inertia effects become critical for the accurate estimation of the natural frequencies and modeshapes as the slenderness ratio decreases. The effect of the concentrated mass and mass moment of inertia on the natural frequencies are also investigated with the modeling method.

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Calculation of Added Mass and Added Moment of Inertia for Chine Hull by Strip Method (단일배골형선(單一背骨型船)의 부가질량(附加質量) 및 부가관성(附加慣性)모우멘트의 일계산(一計算))

  • J.H.,Hwang;K.J.,Cho
    • Bulletin of the Society of Naval Architects of Korea
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    • v.5 no.2
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    • pp.45-50
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    • 1968
  • The added mass and the added moment of inertia of a hard chine hull for heave and pitch were calculated by strip method. For the $k_2$ coefficients, Hwang's values for the straight-framed sections were used and for $k_2$ coefficients Porter's values for ellipses were used in the calculation. Comparisons on added mass and added moment of inertia of hard chine hull with those of ordinary hull form were briefly discussed. The results of the calculation for hard Chine hull give greater valves than ordinary ships at zero Froude Number. Beam draft ratio seems to be much influenced on the added mass and added moment of inertia.

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A Study on Real-Time Inertia Estimation Method for STSAT-3 (과학기술위성 3호 실시간 관성모멘트 추정 기법 연구)

  • Kim, Kwangjin;Lee, Sangchul;Oh, Hwa-Suk
    • Journal of the Korean Society for Aviation and Aeronautics
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    • v.20 no.4
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    • pp.1-6
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    • 2012
  • The accurate information of mass properties is required for the precise control of the spacecraft. The mass properties, mass and inertia, are changeable by some reasons such as consumption of propellant, deployment of solar panel, sloshing, environmental effect, etc. The gyro-based attitude data including noise and bias reduces the control accuracy so it needs to be compensated for improvement. This paper introduces a real-time inertia estimation method for the attitude determination of STSAT-3, Korea Science Technology Satellite. In this method we first filter the gyro noise with the Extended Kalman Filter(EKF), and then estimate the moment of inertia by using the filtered data from the EKF based on the Recursive Least Square(RLS).

Biodynamic Characteristics of Korean Male in Twenties-Mass, Center of Mass and Moment of Inertia Characteristics of Body Segments (한국인 20대 청년 인체분절의 관성특성에 관한 연구)

  • 이영신;임현균;김철중
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.18 no.8
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    • pp.1952-1966
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    • 1994
  • The body segment parameters of twelve young male Korean were measured to compare with the results of foreign cadaver studies. A human body was assumed to have fourteen body segments. The mass of each segment was measured with a water immersion test and the mass center of a segment was determined on the balance platform by changing postures. In the case of Korean, because of the difference in body proportion, the mass center of whole-body is located further from the distal end of head(Korean : 44.9% vs. Caucasian : 41.2%), and the mass center of each segment also located in different proportional locations. The existing regression equations, which can estimate segment mass based upon the anthropometric dimensions, estimates segment mass (the mass of shank) for Korean with 13% error. Therefore, it is not recommended to estimate the mass, and the moment of inertia of body segment of Korean based on the existing equations. However, the density information of body constituents was similar enough to apply it to Korean density. It was validated by the comparison between the results of the direct immersion method and 3-dimensional volume reconstruction of segment form the cross sectional images of CT-scan. The average body density measured form twelve subjects was $1.035{\;}kg/m^3$ and showed deceasing trendency.

A method to determine moment of inertia properties of an arbitrary shape body by modal testing (모우드 측정을 이용한 관성 모우멘트 도출)

  • 박윤식;정경렬;홍성욱;전혁수;이종원
    • 제어로봇시스템학회:학술대회논문집
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    • 1986.10a
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    • pp.102-107
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    • 1986
  • This paper presents a new idea to obtain moment of inertia values of an arbitrary shape body by applying inverse modal transformation technique. A multiaxes inertia pendulum apparatus was designed to measure 6 rigid body modes of a test body. A software was developed to calculate inertia properties as well as the location of center of gravity and total mass of the test body from the measured modal data. The developed method was applied to a simple body of which the inertia properties are known then the obtained values were compared with the known values.

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On the Influence of the Moment of Inertia of Gas on the Galactic Rotation Curves

  • Portnov, Yuriy A.
    • Journal of Astronomy and Space Sciences
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    • v.39 no.3
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    • pp.99-108
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    • 2022
  • There are two models that explain the rotation curves of galaxies: dark matter, which gives the missing contribution to the gravitational potential of the standard theory of gravity, and modified theories of gravity, according to which the gravitational potential is created by ordinary visible mass. Both models have some disadvantages. The article offers a new look at the problem of galactic rotation curves. The author suggests that the moment of inertia creates an additional gravitational potential along with the mass. The numerical simulation carried out on the example of fourteen galaxies confirms the validity of such an assumption. This approach makes it possible to explain the constancy of gas velocities outside the galactic disk without involving the hypothesis of the existence of dark matter. At the same time, the proposed approach lacks the disadvantages of modified theories of gravity, where the gravitational potential is created only by the mass of visible matter.

An Adaptive and Robust Controller for the Undersea Robot Manipulator

  • Young-Sik kim;Park, Hyeung-Sik
    • International Journal of Precision Engineering and Manufacturing
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    • v.4 no.2
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    • pp.13-22
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    • 2003
  • To coordinate the robot manipulator along the desired trajectory, the exact model of the dynamics is required. The added mass and added moment of inertia, buoyancy, drag force, and friction mainly affect the dynamics of the undersea robot manipulator, and they are quite complex and unknown. In this reason. the exact model of the undersea robot manipulator is difficult to obtain. In this paper, instead of having efforts to get the exact model of the robot dynamics, a control-based approach was performed. We modeled the dynamics of the undersea robot manipulator whose parameters are unknown, and then applied a proposed direct adaptive and robust control, which is different from previous studies. The unknown added mass, and added moment of inertia, drag force and friction are estimated by the direct adaptive control scheme, and the drag force which is dominant disturbance is compensated by the robust control. Also, stability of the proposed control scheme is analyzed.

Influence of Elastic Restraints and Tip Mass at Free End on stability of Leipholz Column (Leipholz 기둥의 안정성에 미치는 자유단의 탄성구속과 말단질량의 영향)

  • 윤한익;박일주;진종태;김영수
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 1996.04a
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    • pp.309-315
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    • 1996
  • An analysis is presented on the stability of elastic cantilever column subjected to uniformly distributed follower forces as to the influence of the elastic restraints and a tip mass at the free end. The elastic restraints are formed by both the translational and the rotatory springs. For this purpose, the governing equations and boundary conditions are derived by using Hamilton's principle, and the critical flutter loads and frequencies are obtained from the numerical evaluation of the eigenvalue functions of this elastic system. The added tip mass increases as a whole the critical flutter load in this system, but the presence of its moment of inertia of mass has a destabilizing effect. The existence of the translational and rotatory spring at the free end increases the critical flutter load of the elastic cantilever column. Nevertheless their effects on the critical flutter load are not uniform because of their coupling. The translational spring restraining the end of cantilever column decreases the critical flutter load by coupling with a large value of tip mass, while by coupling with the moment of inertia of tip mass its effect on the critical flutter load is contrary. The rotatory spring restraining the free end of cantilever column increases the critical flutter load by coupling with the tip mass, but decreases it by coupling with the moment of inertia of tip mass.

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