• 제목/요약/키워드: Point mass model

검색결과 293건 처리시간 0.032초

Dubins 곡선을 이용한 항공기 3자유도 질점 모델의 3차원 경로계획 및 유도 (3-Dimensional Path Planning and Guidance using the Dubins Curve for an 3-DOF Point-mass Aircraft Model)

  • 오수헌;하철수;강승은;목지현;고상호;이용원
    • 한국항공운항학회지
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    • 제24권1호
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    • pp.1-9
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    • 2016
  • In this paper, we integrate three degree of freedom(3DOF) point-mass model for aircraft and three-dimensional path generation algorithms using dubins curve and nonlinear path tracking law. Through this integration, we apply the path generation algorithm to the path planning, and verify tracking performance and feasibility of using the aircraft 3DOF point-mass model for air traffic management. The accuracy of modeling 6DOF aircraft is more accurate than that of 3DOF model, but the complexity of the calculation would be raised, in turn the rate of computation is more likely to be slow due to the increase of degree of freedom. These obstacles make the 6DOF model difficult to be applied to simulation requiring real-time path planning. Therefore, the 3DOF point-mass model is also sufficient for simulation, and real-time path planning is possible because complexity can be reduced, compared to those of the 6DOF. Dubins curve used for generating the optimal path has advantage of being directly available to apply path planning. However, we use the algorithm which extends 2D path to 3D path since dubins curve handles the two dimensional path problems. Control law for the path tracking uses the nonlinear path tracking laws. Then we present these concomitant simulation results.

집중질량 라인모델을 이용한 Steel Lazy Wave Riser의 비선형 동적 해석 (Nonlinear Dynamic Analysis of Steel Lazy Wave Riser using Lumped Mass Line Model)

  • 오승훈;정재환;박병원;권용주;정동호
    • 한국해양공학회지
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    • 제33권5호
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    • pp.400-410
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    • 2019
  • In this study, the numerical code for the 3D nonlinear dynamic analysis of an SLWR (Steel Lazy Wave Riser) was developed using the lumped mass line model in a FORTRAN environment. Because the lumped mass line model is an explicit method, there is no matrix operation. Thus, the numerical algorithm is simple and fast. In the lumped mass line model, the equations of motion for the riser were derived by applying the various forces acting on each node of the line. The applied forces at the node of the riser consisted of the tension, shear force due to the bending moment, gravitational force, buoyancy force, riser/ground contact force, and hydrodynamic force based on the Morison equation. Time integration was carried out using a Runge-Kutta fourth-order method, which is known to be stable and accurate. To validate the accuracy of the developed numerical code, simulations using the commercial software OrcaFlex were carried out simultaneously and compared with the results of the developed numerical code. To understand the nonlinear dynamic characteristics of an SLWR, dynamic simulations of SLWRs excited at the hang-off point and of SLWRs in regular waves were carried out. From the results of these dynamic simulations, the displacements at the maximum bending moments at important points of the design, like the hang-off point, sagging point, hogging points, and touch-down point, were observed and analyzed.

비선형 상태공간 모델을 위한 Point-Mass Filter 연구 (A Study on the Point-Mass Filter for Nonlinear State-Space Models)

  • 최영권
    • 산업기술연구
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    • 제43권1호
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    • pp.57-62
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    • 2023
  • In this review, we introduce the non-parametric Bayesian filtering algorithm known as the point-mass filter (PMF) and discuss recent studies related to it. PMF realizes Bayesian filtering by placing a deterministic grid on the state space and calculating the probability density at each grid point. PMF is known for its robustness and high accuracy compared to other nonparametric Bayesian filtering algorithms due to its uniform sampling. However, a drawback of PMF is its inherently high computational complexity in the prediction phase. In this review, we aim to understand the principles of the PMF algorithm and the reasons for the high computational complexity, and summarize recent research efforts to overcome this challenge. We hope that this review contributes to encouraging the consideration of PMF applications for various systems.

CMA-ES를 활용한 수정질점탄도모델의 탄도수정계수 설정기법 (Fitting Coefficient Setting Method for the Modified Point Mass Trajectory Model Using CMA-ES)

  • 안세일;이교복;강태형
    • 한국군사과학기술학회지
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    • 제19권1호
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    • pp.95-104
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    • 2016
  • To make a firing table of artillery with trajectory simulation, a precise trajectory model which corresponds with real firing test is required. Recent 4-DOF modified point mass trajectory model is considered accurate as a theoretical model, but fitting coefficients are used in calculation to match with real firing test results. In this paper, modified point mass trajectory model is presented and method of setting ballistic coefficient is introduced by applying optimization algorithms. After comparing two different algorithms, Particle Swarm Optimization and Covariance Matrix Adaptation - Evolutionary Strategy, we found that using CMA-ES algorithm gives fine optimization result. This fitting coefficient setting method can be used to make trajectory simulation which is required for development of new projectiles in the future.

Wobbling Mass를 고려한 인체 진동 모텔의 개발 (Development of Human Body Vibration Model Including Wobbling Mass)

  • 김영은;백광현;최준희
    • 한국자동차공학회논문집
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    • 제10권2호
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    • pp.193-200
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    • 2002
  • Simple spring-damper-mass models have been widely used to investigate whole-body vortical biodynamic response characteristics of the seated vehicle driver. Most previous models have not considered the effect of wobbling masses; i.e. heart, lungs, liver, intestine, etc. In this study, 4 -DOF seated driver model including one non-rigid mass representing wobbling visceral mass, 5-DOF model including intestine, and 10-DOF model including five lumbar vertebral masses were proposed. The model parameters were identified by a combinatorial optimization technique. simulated annealing method. The objective function was chosen as the sum of error between model response of seat-to-head transmissibility and driving point mechanical impedance and those of experimental data for subjects seated erect without backrest support. The model response showed a good agreement with the experimental response characteristics. Using a 10-DOF model, calculated resonance frequency of lumbar spine at 4Hz was matched well with experimental results of Panjabi et al.

구조 특성을 반영한 인간형 로봇을 위한 실시간 CoM/ZMP 궤적 변환 방법 (Real-Time CoM/ZMP Trajectory Transformation Method for Humanoid Robots Considering Structure Characteristics)

  • 홍석민
    • 한국항행학회논문지
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    • 제21권1호
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    • pp.132-137
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    • 2017
  • 본 논문에서는 로봇의 구조나 보행 상황을 반영해 하나의 보행 패턴을 다른 보행 패턴으로 변환하게 해주는 영모멘트 점 (ZMP; zero moment point)와 질량 중심 (CoM; center of mass)의 실시간 변환 방법을 제안한다. 일반적으로 휴머노이드 로봇은 높이와 질량과 같은 자체적인 구조 특성을 가지고 있다. 이러한 구조적 특성으로 인해 인간 또는 휴머노이드 로봇으로부터 측정되거나 생성되어진 CoM / ZMP 보행 패턴을 다른 로봇에 직접 적용하는 것은 어렵다. 이를 위하여 간단한 휴머노이드 로봇 모델인 cart-table model을 사용해 보폭의 길이, 보행 시간, CoM 높이 변화에 따라 보행 패턴의 특성을 분석한다. 그러한 분석으로부터 변환 방정식을 유도하고 시뮬레이션을 통해 제안된 방법을 검증한다.

Environmental Factors in a Realistic 3D Fishing-Net Simulation

  • Yoon, Joseph;Kim, Young-Bong
    • International Journal of Contents
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    • 제10권3호
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    • pp.84-89
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    • 2014
  • The mass-spring model has been typically employed in physical-based simulators for clothes or patches. The mass-spring model frequently utilizes equal mass and the gravity factor. The model structure of masses supports a shape applicable to fishing nets. Therefore, to create a simulation model of a fishing net, we consider the mass-spring model and adopt the tidal-current and buoyancy effects in underwater environments. These additional factors lead to a more realistic visualization of fishing-net simulations. In this paper, we propose a new mass-spring model for a fishing-net and a method to simplify the calculation equations for a real-time simulation of a fishing-net model. Our 3D mass-spring model presents a mesh-structure similar to a typical mass-spring model except that each intersection point can have different masses. The motion of each mass is calculated periodically considering additional dynamics. To reduce the calculation time, we attempt to simplify the mathematical equations that include the effect of the tidal-current and buoyancy. Through this research, we expect to achieve a real-time and realistic simulation for the fishing net.

질량 변화에 따른 Lumped Mass Beam Model의 이론적 동특성 규명 (Theoretical Approach; Identification of Dynamic Characteristics for Lumped Mass Beam Model due to Changes of Mass)

  • 누룰파와지;윤지현;강귀현;이정윤;오재응
    • 한국소음진동공학회:학술대회논문집
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    • 한국소음진동공학회 2008년도 춘계학술대회논문집
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    • pp.389-392
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    • 2008
  • This paper predicts the changes of natural frequencies due to the changes of mass at different point mass stations by using iterative calculation Transfer Matrices Method for different boundary conditions of a single beam structure (fixed-free and fixed-fixed beam). Firstly, the first three natural frequencies of an original beam are obtained using Transfer Matrices Method to verify the accuracy of the obtained results. The results are then compared with the exact solutions before purposely changing the parameter of mass. Both beams are modeled as discrete continuous systems with six-lumped-mass system. A single beam is broken down into a point mass and a massless beam which represent a single station and expressed in matrix form. The assembled matrices are used to determine the value of natural frequencies using numerical interpolation method corresponding to their mode number by manipulating some elements in the assembled matrix.

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계류된 수중 유연구조물의 설계 및 시뮬레이션 도구 개발 (Design and Simulation Tools for Moored Underwater Flexible Structures)

  • 이춘우;이지훈;최무열;이건호
    • 한국수산과학회지
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    • 제43권2호
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    • pp.159-168
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    • 2010
  • This paper presents a mathematical model and simulation method for investigating the performance of set net systems and fish cage systems influenced by currents and waves. Both systems consist of netting, mooring ropes, a floating collar and sinkers. The netting and ropes were considered flexible structures and the floating collar was considered an elastic structure. Both were modeled on a mass-spring model. The structures were divided into finite elements and mass points were placed at the mid-point of each element, and the mass points were connected by mass-less springs. Each mass point was subjected to external and internal forces and the total force was calculated at every integration step. An implicit integration scheme was used to solve the nonlinear dynamic system. The computation method was applied to dynamic simulation of actual systems simultaneously influenced by currents and waves in order to evaluate their practicality. The simulation results improved our understanding of the behavior of the structure and provided valuable information concerning the optimized design of set net and fish cage systems exposed to an open ocean environment.

Variable Selection in Linear Random Effects Models for Normal Data

  • Kim, Hea-Jung
    • Journal of the Korean Statistical Society
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    • 제27권4호
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    • pp.407-420
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    • 1998
  • This paper is concerned with selecting covariates to be included in building linear random effects models designed to analyze clustered response normal data. It is based on a Bayesian approach, intended to propose and develop a procedure that uses probabilistic considerations for selecting premising subsets of covariates. The approach reformulates the linear random effects model in a hierarchical normal and point mass mixture model by introducing a set of latent variables that will be used to identify subset choices. The hierarchical model is flexible to easily accommodate sign constraints in the number of regression coefficients. Utilizing Gibbs sampler, the appropriate posterior probability of each subset of covariates is obtained. Thus, In this procedure, the most promising subset of covariates can be identified as that with highest posterior probability. The procedure is illustrated through a simulation study.

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