• Title, Summary, Keyword: Gravity Potential Model

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Three-axis Attitude Control for Flexible Spacecraft by Lyapunov Approach under Gravity Potential

  • Bang, Hyo-Choong;Lee, Kwang-Hyun;Lim, Hyung-Chul
    • International Journal of Aeronautical and Space Sciences
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    • v.4 no.1
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    • pp.99-109
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    • 2003
  • Attitude control law synthesis for the three-axis attitude maneuver of a flexible spacecraft model is presented in this study. The basic idea is motivated by previous works for the extension into a more general case. The new case includes gravitational gradient torque which has significant effect on a wide range of low earth orbit missions. As the first step, the fully nonlinear dynamic equations of motion are derived including gravitational gradient. The control law design based upon the Lyapunov approach is attempted. The Lyapunov function consists of a weighted combination of system kinetic and potential energy. Then, a set of stabilizing control law is derived from the basic Lyapunov stability theory. The new control law is therefore in a general form partially validating the previous work in some sense.

A Model Development of Injury Prevention for Application in the Semiconductor Industry (반도체 산업에서의 재해 예방 모델 개발)

  • Yoon, Yong-Gu;Hong, Sung-Man;Park, Peom
    • Journal of the Korea Safety Management & Science
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    • v.4 no.3
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    • pp.1-11
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    • 2002
  • It has been Management for stabilize Enterprise-Management for Economic demand for to Productivity, Automation, customer satisfaction, Especially Semiconductor-Industry has been, potential-risk in working to factory to machine equipment, all kinds of utility, gas, chemical, electronic, Fire. This study of basic-purpose has Research Different From as Follow to analysis and Solution For semiconductor product Factory of a actual point Data and specific-gravity to Relation for company-Injury. 1. It has been try to Injury-Tendency and cause-Analysis for our County-Manufacture-Occupation. 2, Semiconductor Injury of Actual-condition in Enforcement for problem and Analysis that Injury Problem has occupated it Submitted to Solution for ordinary Injury theory View to point Solve at for New Model has applicated to that nilem for processed to Solution.

Nonlinear Control of an Electromagnetic Levitation System Using High-gain Observers for Mmagnetic Bearing Wheels (고이득 관측기를 이용한 자기 베어링 휠용 자기 부상 시스템의 비선형 제어)

  • Choi, Ho-Lim;Shin, Hee-Sub;Koo, Min-Sung;Lim, Jong-Tae;Kim, Yong-Min
    • Journal of Institute of Control, Robotics and Systems
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    • v.15 no.6
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    • pp.573-580
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    • 2009
  • In this paper, we develop a functional test model for magnetic bearing wheels. The functional test model is an electromagnetic levitation system that has three degree of freedom, which consists of one axial suspension from gravity and two axes gimbaling capability to small angels. A nonlinear controller with high-gain observers is proposed and the real-time experiment results show that the rotor is accurately levitated at the desired position and well-balanced, which is a suitable result for the potential use an magnetic bearing wheels. Also, the proposed scheme exhibits better performance when it is compared with the conventional PID control method.

A Study of Collision Characteristics in differential sedimentation according to variation of Ionic Strength, Zeta Potential and Particle Size (이온화세기, 제타전위, 입자크기에 따른 속도차 침전에서의 입자간 충돌특성에 관한 연구)

  • Han, Moo Young;Dock Ko, Seok;Park, Chung Hyun
    • Journal of Korean Society of Water and Wastewater
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    • v.12 no.1
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    • pp.81-87
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    • 1998
  • The possibility of collision of two particles slowly settling one after another in water can be described using the collision efficiency factor in differential sedimentation (${\alpha}_{DS}$). ${\alpha}_{DS}$ was found to be a function of several parameters particle size, particle size ratio, Hamaker constant, density of liquid and particle, gravity acceleration. Previous researches were limited to the case when there is no electric repulsion assuming that the suspension is destabilized. In this paper, ${\alpha}_{DS}$ is calculated for the stabilized condition. The relative trajectory of two particles are calculated including hydrodynamics, attraction and repulsion forces. Ionic strength and surface potential significantly affect the collision possibility of two settling particles. Depending on the surface potential and ionic strength, ${\alpha}_{DS}$ value is divided into three regions; stable, unstable and transition zone. ${\alpha}_{DS}$ increases as the ionic strength increases, and as the surface charge decreases. This result can be used to model both destabilized and stabilized suspension incorporating the collision efficiency factors of the other coagulant mechanisms such as fluid shear and Browian motion.

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Stability and parameters influence study of fully balanced hoist vertical ship lift

  • Cheng, Xionghao;Shi, Duanwei;Li, Hongxiang;Xia, Re;Zhang, Yang;Zhou, Ji
    • Structural Engineering and Mechanics
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    • v.66 no.5
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    • pp.583-594
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    • 2018
  • A theoretical formulation based on the linearized potential theory, the Descartes' rule and the extremum optimization method is presented to calculate the critical distance of lifting points of the fully balanced hoist vertical ship lift, and to study pitching stability of the ship lift. The overturning torque of the ship chamber is proposed based on the Housner theory. A seven-free-degree dynamic model of the ship lift based on the Lagrange equation of the second kind is then established, including the ship chamber, the wire rope, the gravity counterweights and the liquid in the ship chamber. Subsequently, an eigenvalue equation is obtained with the coefficient matrix of the dynamic equations, and a key coefficient is analyzed by innovative use of the minimum optimization method for a stability criterion. Also, an extensive influence of the structural parameters contains the gravity counterweight wire rope stiffness, synchronous shaft stiffness, lifting height and hoists radius on the critical distance of lifting points is numerically analyzed. With the Runge-Kutta method, the four primary dynamical responses of the ship lift are investigated to demonstrate the accuracy/reliability of the result from the theoretical formulation. It is revealed that the critical distance of lifting points decreases with increasing the synchronous shaft stiffness, while increases with rising the other three structural parameters. Moreover, the theoretical formulation is more applicable than the previous criterions to design the layout of the fully balanced hoist vertical ship lift for the ensuring of the stability.

A Study on Geoid Model Development Method in Philipphines (필리핀 지오이드모델의 개발방안 연구)

  • Lee, Suk-Bae;Pena, Bonifasio Dela
    • Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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    • v.27 no.6
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    • pp.699-710
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    • 2009
  • If a country has her geoid model, it could be determine accurate orthometric height because the geoid model could provide continuous equi-gravity potential surface. And it is possible to improve the coordinates accuracy of national control points through geodetic network adjustment considering geoidal heights. This study aims to find the best way to develop geoid model in Philippines which have similar topographic conditions as like Malaysia and Indonesia in Eastsouth asia. So, in this study, it is surveyed the general theories of geoid determination and development cases of geoid model in Asia and it is computed that the geoidal heights and gravity anomalies by spherical harmonic analysis using EGM2008, the latest earth geopotential model. The results show that first, the development of gravimetric geoid model based on airborne gravimetry is needed and second, about 200 GPS surveying data at national benchmark is needed. It is concluded that it is the most reasonable way to develop the hybrid geoid model through fitting geometric geoid by GPS/leveling data to gravimetric geoid. Also, it is proposed that four band spherical Fast fourier transformation(FFT) method for evaluation of Stokes integration and remove and restore technique using EGM2008 and SRTM for calculation of gravimetric geoid model and least square collocation algorithm for calculation of hybrid geoid model.

Numerical evaluation of buried composite and steel pipe structures under the effects of gravity

  • Toh, William;Tan, Long Bin;Tse, Kwong Ming;Raju, Karthikayen;Lee, Heow Pueh;Tan, Vincent Beng Chye
    • Steel and Composite Structures
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    • v.26 no.1
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    • pp.55-66
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    • 2018
  • In this paper, the response of an underground fibreglass reinforced plastic (FRP) composite pipe system subjected to realistic loading scenarios that may be experienced by an actual buried pipeline is investigated. The model replicates an arbitrary site with a length of buried pipeline, passing through a $90^{\circ}$ bend and into a valve pit. Various loading conditions, which include effects of pipe pressurization, differences in response between stainless steel and fibreglass composite pipes and severe loss of bed-soil support are studied. In addition to pipe response, the resulting soil stresses and ground settlement are also analysed. Furthermore, the locations of potential leakage and burst have also been identified by evaluating the contact pressures at the joints and by comparing stresses to the pipe hoop and axial failure strengths.

Demand Characteristics and Analysis of Changes in Spatial Accessibility of Public Sports Facilities (공공체육시설 수요특성 및 공간적 접근성 분석)

  • Kim, Seong-Hee;Kim, Yong-Jin
    • The Journal of the Korea Contents Association
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    • v.17 no.7
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    • pp.283-293
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    • 2017
  • This study analyzed the actual conditions of use of public sports facilities and characteristics of the users of the facilities through surveys and measured the spatial imbalance of the public sports facilities currently supplied by using gravity potential model. This study also suggests evaluation criteria that may be considered for efficient location selection by examining the change of accessibility to the facilities that meet the needs of users in the future. As the results of the questionnaire survey, unlike current usage, the users hoped for badminton, weight training and swimming. And we could confirm the demand for the expansion of the multi - purpose indoor gym which can carry out such activities in the areas. As the result of the analysis on the difference in accessibility of the public sports facility, there were some large variations in the regions. It was found that a balanced supply of facilities was needed in terms of equity. In particular, when analyzing by considering the population estimates of 2025, It is analyzed that the accessibility will be reduced to about 60% compared to that of 2015. In addition, it is evaluated as the best alternative in terms of overall efficiency that the location of the facilities should be in Munsan area where population growth is expected in the future.

Compression of Terrain Data using Integer Wavelet Transform (IWT) and Application on Gravity Terrain Correction (정수웨이블릿변환(IWT)을 이용한 지형 자료의 압축 및 정밀 지형 효과 계산을 위한 활용 방법 고찰)

  • Chung, Hojoon;Lee, Heuisoon;Oh, Seokhoon;Park, Gyesoon;Rim, Hyoungrea
    • Journal of the Korean earth science society
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    • v.34 no.1
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    • pp.69-80
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    • 2013
  • Terrain data is one of important basic data in various areas of Earth science. Recently, finer DEM data is available, which necessary to develop a method that deals with such huge data efficiently. This study was conducted on the lossless compression of DEM data and efficient partial reconstruction of terrain information from compressed data. In this study, we compressed the wavelet coefficients of DEM, obtained from integer wavelet transform (IWT) by entropy encoding. CDF (Cohen-Daubechies-Feauveau) 3.5 wavelet showed the best compression ratio of about 45.4% and the optimum decomposition level was 3. Results also showed that a small region of terrain could be restored from the inverse wavelet transform with a part of the wavelet coefficients that are related to such region instead of whole reconstruction. We discussed the potential applications of the terrain data compression for precise gravity terrain correction.

Analysis on Wood Quality, Geometry Factor, and Their Effects on Lathe Check of Samama (Anthocephalus macrophyllus) Veneer

  • Cahyono, Tekat Dwi;Wahyudi, Imam;Priadi, Trisna;Febrianto, Fauzi;Bahtiar, Effendi Tri;Novriyanti, Eka
    • Journal of the Korean Wood Science and Technology
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    • v.44 no.6
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    • pp.828-841
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    • 2016
  • Relatively little information is available regarding the correlation between wood and veneer quality, especially for Samama wood, an endemic wood species in eastern Indonesia. This study addresses the quality of 8 years old Samama wood and its effect on the veneer quality. Samama wood quality was determined by evaluating its specific gravity, moisture content, fiber dimensions, and microfibril angle from pith toward bark. Meanwhile, veneer quality was assessed by examining veneer thickness and lathe check characteristics. Geometry factor model was constructed to elaborate the quantities of lathe check from pith toward bark. Results show that fair variations of veneer thickness, ranging from 1.5 mm to 3.0 mm, could be obtained from Samama wood. The quantity, depth, and length of lathe check were noticeably decreasing toward bark. Further, in the same manufacturing process, geometry factor was determined as the dominant factor over other wood properties in affecting the frequency of lathe checks from pith towards bark. These facts should be put into consideration in producing veneer from Samama wood. Moreover, these results enlighten the potential of Samama wood as plywood and other excellent veneer-based products.