• 지구물리와물리탐사
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• 제16권4호
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• pp.225-233
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• 2013

효율적이고 객관적인 NMO 속도분석을 위해 사용되는 자동 속도분석의 정확성은 속도 빛띠의 속도 해상도에 많은 영향을 받는다. 본 연구에서는 고해상도 BDS (high-resolution Bootstrapped Differential Semblance)를 이용하여 속도 빛띠를 구성하고, 이를 이용하여 공통 중간점 모음 별로 병렬적으로 자동 속도분석을 수행하는 모듈을 개발하였다. 또한 이 고해상도 BDS를 이용하는 자동 속도분석 모듈의 속도분석 결과를 BDS (Bootstrapped Differential Semblance)를 이용한 자동 속도분석의 결과와 비교하였다. 수평층을 포함한 속도모델로부터 얻은 합성 탄성파 탐사자료를 생성하고 이를 이용하여 개발된 모듈을 검증한 결과 본 연구를 통해 개발된 모듈이 좀 더 정확한 속도를 추정하는 것을 확인하였다. 또한 현장자료에 개발된 모듈을 적용하여 이벤트의 연속성이 향상된 공통 중간점 겹쌓기 단면을 구할 수 있는 NMO 속도를 추정하였다.

• 제어로봇시스템학회논문지
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• 제19권12호
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• pp.1145-1151
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• 2013

Kinematic modeling is a prerequisite for motion planning and the control of mobile robots. In this paper, we proposed a new method of kinematic modeling for a type of mobile robot based on differential motion transformation. The differential motion implies a small translation and rotation in three-dimensional space in a small time interval. Thus, transformation of the differential motion gives the velocity relationship, i.e., Jacobian between two coordinate frames. Since the theory of the differential motion transformation is well-developed, it is useful for the systematic velocity kinematic modeling of mobile robots. In order to show the validity for application of the differential motion transformation, we obtained velocity kinematic models for a type of exemplar mobile robot including spherical ballbots.

• 로봇학회논문지
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• 제10권4호
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• pp.230-244
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• 2015

Continuous-path motion control such as resolved motion rate control requires online solving of the inverse differential kinematics for a robot. However, the solution space of the inverse differential kinematics related to Jacobian J is not well-established. In this paper, the solution space of inverse differential kinematics is analyzed through categorization of mapping conditions between joint velocities and end-effector velocity of a robot. If end-effector velocity is within the column space of J, the solution or the minimum norm solution is obtained. If it is not within the column space of J, an approximate solution by least-squares is obtained. Moreover, this paper introduces an improved mapping diagram showing orthogonality and mapping clearly between subspaces, and concrete examples numerically showing the concept of several subspaces. Finally, a solver and graphics user interface (GUI) for inverse differential kinematics are developed using MATLAB, and the solution of inverse differential kinematics using the GUI is demonstrated for a vertically articulated robot.

• Structural Engineering and Mechanics
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• 제62권1호
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• pp.65-77
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• 2017

The free vibration analysis of fluid conveying Timoshenko pipeline with different boundary conditions using Differential Transform Method (DTM) and Adomian Decomposition Method (ADM) has not been investigated by any of the studies in open literature so far. Natural frequencies, modes and critical fluid velocity of the pipelines on different supports are analyzed based on Timoshenko model by using DTM and ADM in this study. At first, the governing differential equations of motion of fluid conveying Timoshenko pipeline in free vibration are derived. Parameter for the nondimensionalized multiplication factor for the fluid velocity is incorporated into the equations of motion in order to investigate its effects on the natural frequencies. For solution, the terms are found directly from the analytical solution of the differential equation that describes the deformations of the cross-section according to Timoshenko beam theory. After the analytical solution, the efficient and easy mathematical techniques called DTM and ADM are used to solve the governing differential equations of the motion, respectively. The calculated natural frequencies of fluid conveying Timoshenko pipelines with various combinations of boundary conditions using DTM and ADM are tabulated in several tables and figures and are compared with the results of Analytical Method (ANM) where a very good agreement is observed. Finally, the critical fluid velocities are calculated for different boundary conditions and the first five mode shapes are presented in graphs.

• 한국산업정보학회논문지
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• 제24권5호
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• pp.121-127
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• 2019

본 논문에서는 물류창고, 제조업, 협업 로봇 등 다양한 애플리케이션에 활용되고 있는 비홀로노믹 제약을 가진 차동 바퀴형 모바일 로봇의 용이한 운용을 위한 로컬 속도 생성 제어 알고리즘을 제안한다. 기존의 차동 바퀴형 모바일 로봇 운용 방법은 운용자가 자신의 좌표계가 아닌 로봇의 좌표계를 기준으로 인지하고 로봇의 속도를 직접 생성해야 하였으며, 이로 인해 운용의 직관성이 낮아지고 업무의 효율 저하 및 사고 발생률이 증가하게 된다. 본 연구에서는 이를 개선하여 운용자가 자신의 좌표계를 기준으로 로봇을 운용할 수 있도록 한다. 제안하는 알고리즘은 실제 차동 바퀴형 모바일 로봇을 활용한 실험을 통하여 알고리즘의 효용성을 검증한다.

• Journal of applied mathematics & informatics
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• 제41권2호
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• pp.401-411
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• 2023

The effects of longitudinal velocity dusty fluid flow in a weak magnetic field are investigated in this paper. An external uniform magnetic field parallel to the flow of dusty fluid influences the flow of dusty fluid. Besides that, the problem under investigation is completely defined in terms of identifying parameters such as longitudinal velocity (u), Hartmann number (M), dust particle interactions β, stock resistance γ, Reynolds number (Re) and magnetic Reynolds number (Rm). While using suitable transformations of resemblance, The governing partial differential equations are transformed into a system of ordinary differential equations. The Hankel Transformation is used to solve these equations numerically. The effects of representing parameters on the fluid phase and particle phase velocity flow are investigated in this analysis. The magnitude of the fluid particle is reduced significantly. The result indicates the magnitude of the particle reduced significantly. Although some of our numerical solutions agree with some of the available results in the literature review, other results differs because of the effect of the introduced magnetic field.

• 지구물리와물리탐사
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• 제13권1호
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• pp.31-39
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• 2010

자동속도분석의 목적은 대용량 탄성파탐사자료로부터 정확한 속도를 효율적으로 추출하는 것이다. 본 연구에서는 bootstrapped differential semblance (BDS) 방법과 몬테카를로 역산법을 이용하여 효율적인 자동속도분석 알고리듬을 개발하였다. 자동속도분석을 통해 보다 정확한 결과를 계산하기 위하여 우리가 개발된 알고리듬에서는 일반적인 셈블런스보다 높은 속도해상도를 제공하는 BDS를 일관성 측정법으로 사용한다. 게다가, 개발된 자동속도분석 알고리듬의 처리시간을 줄이고, 효율성을 증가시키기 위해 조건적으로 초기속도모델을 결정하는 단계를 추가하였다. 그리고 잘못된 피크값을 피킹하는 문제를 방지하기 위해서 새로운 RMS 속도제약조건을 선택적으로 사용하였다. 개발된 자동속도분석 모듈의 성능을 시험하기 위해서 합성탄성파탐사자료와 동해에서 취득한 현장자료에 개발된 모듈을 적용하였다. 본 연구에서 개발원 알고리듬을 통해 얻은 속도결과를 적용하여 안든 중합단면들은 일관된 반사이벤트들과 NMO보정 결과의 질이 향상된 것을 보여준다. 더욱이, 개발원 알고리듬은 구간속도제약조건을 확인하면서 구간속도를 먼저 구하고 이를 이용하여 RMS 속도를 계산하기 예문에, 지질학적으로 타당한 구간속도를 구할 수 있다. 또한, 구간속도의 경계등이 중합단면도에서 나타나는 반사이벤트들과 잘 부합된다.

• Journal of Mechanical Science and Technology
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• 제18권10호
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• pp.1782-1798
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• 2004

A numerical study of a natural convection in a rectangular cavity with the low-Reynolds-number differential stress and flux model is presented. The primary emphasis of the study is placed on the investigation of the accuracy and numerical stability of the low-Reynolds-number differential stress and flux model for a natural convection problem. The turbulence model considered in the study is that developed by Peeters and Henkes (1992) and further refined by Dol and Hanjalic (2001), and this model is applied to the prediction of a natural convection in a rectangular cavity together with the two-layer model, the shear stress transport model and the time-scale bound ν$^2$- f model, all with an algebraic heat flux model. The computed results are compared with the experimental data commonly used for the validation of the turbulence models. It is shown that the low-Reynolds-number differential stress and flux model predicts well the mean velocity and temperature, the vertical velocity fluctuation, the Reynolds shear stress, the horizontal turbulent heat flux, the local Nusselt number and the wall shear stress, but slightly under-predicts the vertical turbulent heat flux. The performance of the ν$^2$- f model is comparable to that of the low-Reynolds-number differential stress and flux model except for the over-prediction of the horizontal turbulent heat flux. The two-layer model predicts poorly the mean vertical velocity component and under-predicts the wall shear stress and the local Nusselt number. The shear stress transport model predicts well the mean velocity, but the general performance of the shear stress transport model is nearly the same as that of the two-layer model, under-predicting the local Nusselt number and the turbulent quantities.

• Advances in concrete construction
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• 제9권1호
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• pp.103-113
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• 2020

This paper deal with the critical fluid velocity response of nanocomposite pipe conveying fluid based on numerical method. The pressure of fluid is obtained based on perturbation method. The motion equations are derived based on classical shell theory, energy method and Hamilton's principle. The shell is reinforced by nanoparticles and the distribution of them are functionally graded (FG). The mixture rule is applied for obtaining the equivalent material properties of the structure. Differential quadrature method (DQM) is utilized for solution of the motion equations in order to obtain the critical fluid velocity. The effects of different parameters such asCNT nanoparticles volume percent, boundary conditions, thickness to radius ratios, length to radius ratios and internal fluid are presented on the critical fluid velocity response structure. The results show that with increasing the CNT nanoparticles, the critical fluid velocity is increased. In addition, FGX distribution of nanoparticles is the best choice for reinforcement.

• 대한임베디드공학회논문지
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• 제17권2호
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• pp.123-128
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• 2022

This paper proposes a mobile robot platform for education that can experiment with various autonomous driving algorithms such as obstacle avoidance and path planning. The platform consists of a robot module and a remote controller module, both of which are based on the Arduino Nano 33 IoT embedded board. The robot module is designed as a differential drive type using two encoder motors, and the speed of the motor is controlled using PID control. In the case of the remote controller module, a command to control the robot platform is received with a 2-axis joystick input, and an elliptical grid mapping technique is used to convert the joystick input into a linear and angular velocity command of the robot. WiFi and Zigbee are used for communication between the robot module and the remote controller module. The proposed robot platform was tested by measuring and comparing the linear velocity and angular velocity of the actual robot according to the linear velocity and angular velocity commands of the robot generated by the input of the joystick.