• Steel and Composite Structures
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• 제47권2호
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• pp.289-296
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• 2023

The failure of a thin-walled tube was studied in this paper based on three failure models. Both proportional and non-proportional loading paths were applied. Proportional loading consisted of combined tension-torsion. Cyclic non-proportional loading was also applied. It was a circular out-of-phase axial-shear stress loading path. The third loading path was a combination of a constant internal pressure and a bending moment. The failure models under study were equivalent plastic strain, modified Mohr-Coulomb (Bai-Wierzbicki) and Tearing parameter models. The elasto-plastic analysis was conducted using J2 criterion and nonlinear kinematic hardening. The return mapping algorithm was employed to numerically solve the plastic flow relations. The effects of the hydrostatic stress on the plastic flow and the stress triaxiality parameter on the failure were discussed. Each failure model under study was utilized to predict failure. The failure loads obtained from each model were compared with each other. The equivalent plastic strain model was independent from the stress triaxiality parameter, and it predicted the highest failure load in the bending problem. The modified Mohr-Coulomb failure model predicted the lowest failure load for the range of the stress triaxiality parameter and Lode's angle.

• 제어로봇시스템학회논문지
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• 제17권12호
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• pp.1256-1265
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• 2011

Automated parking assist systems are being commercialized and rapidly spread in the market. In order to improve odometry accuracy, we proposed a practical odometry calibration scheme of Car-Like Mobile Robot (CLMR). However, there were some open problems in our prior work. For example, it was not clear whether the kinematic parameters always converged or not using the proposed calibration scheme. In addition, test driving had to be carried out "twice" without detailed explanation. This research aims to provide answers for the addressed questions though the convergence property analysis of the calibration scheme. In this paper, we evaluate on the effect of the kinematic parameter error on the odometry error at the final pose by numerical computation. The evaluation will show that the wheel diameter and tread of the CLMR can be calibrated by iterative test drives. In addition, the region of convergence in the parametric space will be discussed. Presented experimental results clearly showed that the proposed calibration scheme would be useful in practical applications.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집A
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• pp.268-273
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• 2000

Velocity-dependent increase in tonic stretch reflexes is one of the prominent characteristics of spasticity. It is very important to evaluate spasticity objectively and quantitatively before and after treatment for physicians. An accurate quantitative biomechanical evaluation for the spasticity which is caused by the disorder of central nervous system is made in this study. A sudden leg dropper which is designed to generate objective testing environment at every trial gives very effective environment for the test. Kinematic data are archived by the 3-dimensional motion analysis system($Elite^{(R)}$, B.T.S., Italy). Kinematic data are angle and angular velocity of lower limb joints, and length and lengthening velocity of lower limb muscle. A program is also developed to analyze the kinematic data of lower limb, contraction and relaxation length of muscles, and dynamic EMG data at the same tim. To evaluate spasticity quantitatively, total 31 parameters extracted from goniogram, EMG and muscle model are analyzed. Statistical analysis are made for bilateral correlations for all parameters. The described instrumentation and parameters to make quantitative and objective evaluation of spasticity shows good results.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1988년도 한국자동제어학술회의논문집(국내학술편); 한국전력공사연수원, 서울; 21-22 Oct. 1988
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• pp.511-517
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• 1988

Movement order program of robot operating program is generally made by teach-in method. Therefore in most cases it is sufficient as long as the robot system shows a reguired repeatability for the working conditions. But the trend in the robot application moves to the automatic generation of the working programs. A mathematical robot model similar to the reality is necessary for the analysis of the kinematic transformation of the robot system. The purposes of this paper are to make a better describing form and to suggest an automatic algorithm for kinematic parameter identification.

• 한국정밀공학회지
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• 제14권4호
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• pp.64-71
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• 1997

Objective of calibration is to find out the accurate kinematic relationships between robot joint angles and the position of the end-effector by estimating accurate model parameters defining the kinematic function. Estimating the model parameters requires measurement of the end-effector position at a number of different robot configurations. This paper studies the implication of measurement configurations in robot calibration. For selecting appropriate measurement configurations in robot calibration, an index is defined to measure the observability of the model parameters with respect to a set of robot configurations. It is found that, as the observability index of the selected measurement configurations increase the attribution of the position errors to the parameter errors becomes dominant while the effects of the measurement and unmodeled errors are less significant; consequently better estimation of parameter errors is expected. To demonstrate the implication of the observability measure in robot calibration, computer simulations are performed and their results are discussed.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1993년도 정기총회 및 추계학술대회 논문집 학회본부
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• pp.307-309
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• 1993

Robot's kinematic equation is not perfect. In this paper, a method for reducing the positioning error which comes from the imperfect robot kinematics is introduced. This method compensates the parameter of the kinematic equation using real positioning error. And the trajectories using these compensated parameterare compared with uncompensated ones.

• 한국정밀공학회지
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• 제16권8호
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• pp.186-192
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• 1999

This paper introduces a study of a method for the forward kinematic analysis, which finds the 6 DOF motions and velocities from the given six cylinder lengths in the Stewart platform. From the viewpoints of kinematics, the solution for the inverse kinematic is easily found by using the vectors of the links which are composed of the joint coordinates in base and plate frames, to act contrary to the serial manipulator, but forward kinematic is difficult because of the nonlinearity and complexity of the Stewart platform dynamic equation with the multi-solutions. Hence we, first in this study, introduce the linear estimator using the Luenberger's observer, and the estimator using the nonlinear measured model for the forward kinematic solutions. But it is difficult to find the parameter of the design for the estimation gain or to select the estimation gain and the constant steady state error exists. So this study suggests the estimator with the estimation gain to be learned by the neural network with the structure of multi-perceptron and the learning method using back propagation and shows the estimation performance using the simulation.

• 한국방재학회 논문집
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• 제10권4호
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• pp.95-104
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• 2010

저류함수법은 한국의 홍수예경보시스템에서 가장 널리 사용되고 있는 강우-유출 모형 중 하나이다. 본 연구에서는 저류함수법의 매개변수를 운동파모형과 비교하여 물리적 의미를 고찰하고 국내 하천유역에서의 일반적인 적용방법을 도모하고자 한다. 두 모형의 기본적인 방정식을 이론적으로 비교한 결과 저류함수법에서 저류량과 비선형관계인 유출량의 멱승을 나타내는 P와 운동파모형에서 유출수심과 비선형관계를 보이는 단위폭당 유량의 멱승을 나타내는 p가 동일하다고 볼 수 있었다. 또한, 저류함수법에서 저류상수와 지체시간을 나타내는 K와 $T_l$은 운동파모형에서 유역특성상수를 나타내는 k, 유역면적 그리고 Hack의 법칙의 계수를 이용하여 관계식을 제시할 수 있었다. 이와 함께 한국에서의 저류함수법의 일반적인 적용을 위해 K와 $T_l$에 관한 매개변수 추정을 위한 식을 제안할 수 있었다. 이러한 관계식은 국내 전국에 산재한 17개의 댐지점에서의 101개의 호우사상으로부터 얻어졌다. 이들 관계식은 운동파 모형의 매개변수와 국내 하천유역에 대해 새롭게 발전된 형태로 얻어진 Hack의 법칙에 기초하여 결정될 수 있었다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 1998년도 춘계학술대회논문집; 용평리조트 타워콘도, 21-22 May 1998
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• pp.40-44
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• 1998

In this paper, a kinematic and dynamic model for an excavator is presented. A graphic user interface program for kinematic-dynamic analysis for the excavator is developed. To predict the stiffness and damping properties of the joint between the vehicle and the track, a parameter study is executed. Using the predicted joint stiffness and damping, the jerk simulation for the excavator is reproduced. Simulation results are compared with the test results to confirm the validity of the simulation model.

• 한국CDE학회논문집
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• 제15권3호
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• pp.212-221
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• 2010

Proposed in the paper is a methodology to generate kinematic template for 3D JIG models. Recently, according to increase of the rate of automatic facility in manufacturing system, the 3D manufacturing and verification research and development have been issued. So, unlike in the past, moving 3D facilities are very various like JIGs, turn table, AS/RS worked in the automated manufacturing industry. Because 3D mesh models are used in these kinds of 3D simulation, users have to define the kinematic information manually. This 3D mesh data doesn't have parametric information and design history of the 3D model unlike the design level data. So, it is lighter than 3D design level data and more efficient to render on the 3D virtual manufacturing environment. But, when user wants to find a common axis located between the links, the parameter information of the model has to reconstruct for defining kinematic construction. It takes a long time and very repetitive to define an axis and makes a joint using 3D mesh data and it is non-intuitive task for user. This paper proposed template model that provides kinematic information of the JIG. This model is kinds of a state diagram to describe a relation between links. So, this model can be used for a kinematic template to the JIG which has a same mechanism. The template model has to be registered in the template library to use in the future, after user made the model of the specific type of the 3D JIG model.