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이경환(KyeongHwan Lee),심규진(KyuJin Shim),악바르 완다 알리(Wanda Ali Akbar),정한식(HanShik Chung),정효민(HyoMin Jeong) 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.11
Nowadays, study about hydrogen fuel which consist of hydrogen extraction and reforming processes, fuel cell equipment, and receptacle are flourishing allover the world. Currently, Korea hydrogen station is still underdeveloping. And also the most important part which is hydrogen compressor has not been developed. Snubber is one of the important parts in hydrogen compressing system. It is installed before and after reciprocating hydrogen compressor. Snubber has two functions. One is making down pulsation waveform. Because pressure hydrogen gas where is after passing through reciprocation compressor part has high pulsation waveform, so this waveform has to decline. And the other function is precipitating alien substances to outside. Normally, even if 99.99% hydrogen gas is still containing alien substance. Buffer is set up inside snubber and the waveform will hit buffer. This snubber study uses CFD.
FEATURES OF PRESSURES IN THE PIPE FITTED BETWEEN TWO SNUBBERS IN HYDROGEN COMPRESSING SYSTEM
Mohammad Rahman(라흐만),Kyeonghwan Lee(이경환),Suprianto Wobowo(위보워),Jusik Woo(우주식),Hanshik Chung(정효민),i Hk Chung(정한식) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.5
Compressing system is one of the most important processes in hydrogen gas handling: production, storage, distribution until using. High pulsation waveforms produced during hydrogen compression can be reduced by employing snubber in the system. There are some pipes to flow hydrogen between two snubbers. An experiment has been conducted to investigate the features of pressure in the pipe placed between snubbers in reciprocating compression system. In measuring amplitude FFT was done and pressure RMS values at input and output of one the pipe using data for 10, 20, 30, 50 and 60 ㎐ motor frequency of compressor operation. The pressure pulsation reductions are varied from 16.415~35.151% and corresponding pressure losses 0.007~0.759%.
들깨잎의 자동수확을 위한 잎몸 길이를 추정하는 근사형의 설계
조철현 ( Chul-hyun Jo ),이경환 ( Kyeonghwan Lee ) 한국농업기계학회 2020 한국농업기계학회 학술발표논문집 Vol.25 No.2
들깨잎의 수확은 보통 성장한 잎을 하나하나 손으로 채집하는 노동집약적이다. 이를 암로봇(arm robot)을 이용하여 자동수확하기 위해서는 작물 중 한 개체를 인식하고 그 개체에 달린 잎을 인식하여 수확할 잎을 선정하고 작물의 상단에서 뎁스카메라(depth carmera)를 이용하여 수확을 하기 위한 아랫잎을 보면 윗잎에 아랫잎의 잎자루 부분이 가려져서 보이지 않으며, 가려진 부분을 추정하여 잎몸의 길이를 계산하는 근사형을 설계한다. 근사형의 기준은 판매 가능한 크기로 성장한 윗자람 이나 병이 없는 것으로 형태가 변형되지 않은 보통상태에서 자란 잎으로 다량의 잎을 길이와 폭의 수치를 측정하고 잎 전체의 형태를 분류하여 근사형을 제시하였다. 제시된 근사형은 단일형이며 잎의 폭을 기준으로 잎의 길이를 계산해 주는 것으로 잎 크기가 제시되면 잎몸의 길이가 계산이 가능하게 된다. 근사형을 검증하기 위해 수확된 들깨잎의 폭을 입력하여 크기를 대조하여 계산치가 맞는지를 검사하여 +-3%오차를 기준으로 99%내에 값이 있음을 확인하였다. 이 근사형을 활용하여 암로봇을 이용한 자동수확장치의 알고리즘 설계에 적용할 예정이다.
우주식(Jusik Woo),이경환(Kyeonghwan Lee),위보워(Wi bowo),정한식(Hanshik Chung),정효민(Hyomin Jeong) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.5
In designing of condensers, the prediction of pressure drop is very important to predict the heat transfer coefficient. Modeling of two phase flow, inside a horizontal tube using CFD analysis is difficult with available two phase model in Fluent because of its changing flow patterns continuously. In this paper presents the CFD analysis of two phase flow of refrigerants inside a horizontal tube of 1.2m length three different inner model diameters of 0.085m, 0.0125m and 0.02141m, respectively, is carried out using 3D model under adiabatic condition. The considered refrigerants are R12 and R134a. The analysis is conducted at different temperatures and flow rates to evaluate the local frictional pressure drop. Using 3D model, average properties are obtained for each refrigerants. Obtained pressure drop data is compared with separated flow models available in literature.
상태 흐름 방법을 기반으로 실내 환경에서 외발 자전거 형 이동 로봇을 위한 경로 추종 플랫폼 개발
첸티안 ( Tean Chen ),유헌종 ( Heonjong Yoo ),이경환 ( Kyeonghwan Lee ) 한국농업기계학회 2020 한국농업기계학회 학술발표논문집 Vol.25 No.2
Localization is one of the important method for autonomous indoor robots to recognize it’s own position. In general, navigation of mobile robots is conducted using camera, Lider and GPS. But in case of indoor environment, GPS is unavailable. In this presentation, an autonomous indoor mobile robot, that is, a shuttle robot used a state flow method via ROS network: MATLAB and Linux high-level computers, IMU sensor, and then was able to obtain the cartesian coordinate information of the unicycle type mobile robot. After setting the pre-determined time based on the length of the path in the State Flow block, a path planning which is able to execute the work effectively is established using state flow algorithm. The state flow block produces time-series data sets which represents linear and angular velocities signals. Depending on the numerical values of the signal, the left and right motor rotational speed should be calculated through mobile robot forward kinematics. Several cases are considered: Case I) indicated the linear velocity is set positive certain value, and angular velocity is zero, so that the corresponding mobile robot moves forward. Case II) says that the linear velocity is set positive certain value and angular velocity is set positive certain value, which means the mobile robot turns right. Case III) says that the linear velocity is set positive certain value and angular velocity is set negative certain value, which means the corresponding mobile robot turns left. Case IV) says that the linear velocity is set negative certain value and angular velocity is set zero, which indicates the mobile robot moves backward. The effectiveness of the methods is demonstrated through desktop based developed indoor mobile robot’s control results.
첸티안 ( Tean Chen ),조철현 ( Jo Chulhyun ),유헌종 ( Heonjong Yoo ),이경환 ( Kyeonghwan Lee ) 한국농업기계학회 2021 한국농업기계학회 학술발표논문집 Vol.26 No.1
In this presentation, the state flow method is utilized for path following indoor environment. Here, the novel voice recognition part is incorporated into path tracking problem using TCPIP communication. The two path following scenario was designed, and TCPIP receive block receives ASCII code from Android program. If the ASCII value is bigger than threshold value we set in the TCPIP receive block, the block itself chooses path 1, otherwise the block chooses path 2 in the real-time implementation. In order to implement the voice recognition based platform control, the Android program, MATLAB/SIMULINK program, Linux system are connected through ROS (Robot operating system) node connection. To summarize that, nodes are composed of three parts: the Android program, Linux system, MATLAB/SIMULINK program.
첸티안 ( Tean Chen ),조철현 ( Jo Chulhyun ),파블러 ( Pablo Vela ),유헌종 ( Heonjong Yoo ),이경환 ( Kyeonghwan Lee ) 한국농업기계학회 2021 한국농업기계학회 학술발표논문집 Vol.26 No.2
In an agricultural indoor environment like a greenhouse, it is hard to utilize GPS sensor for estimating mobile robot position. So odometry sensor i.g. encoder is needed for indoor agricultural robot localization. In a structured agricultural indoor environment, simultaneous localization and mapping method using multi-sensors such as Lidar, IMU, encoder to find a destination can be inefficient. we propose that encoder-based localization method based on a pre-built indoor environment map for efficient navigation of a 2-wheel agricultural indoor mobile robot. First, we constructed a 2D indoor map using Lidar and IMU data, and in the constructed map, for effective localization of the mobile robot, we divided the free space that the indoor mobile robot can navigate and the obstacles that interfere with the robot's moving in advance. And then to estimate the robot localization we adopt odometer increment model using encoder measurements of the indoor mobile robot. In order to evaluate the localization accuracy performance of our proposed method, we compared with the localization performance of the existing SLAM algorithms- LOAM, LeGo LOAM, A LOAM- for the position accuracy and odometry measurement accuracy with comparison to the position of the pre-built map. The position accuracy and odometry prediction accuracy of our proposed algorithm were evaluated as the average of 96.0% and 97.2% respectively. In the future, we will conduct further experiments in real agricultural indoor environments such as greenhouses.
첸티안 ( Tean Chen ),조철현 ( Jo Chulhyun ),파블러 ( Pablo Vela ),유헌종 ( Heonjong Yoo ),이경환 ( Kyeonghwan Lee ) 한국농업기계학회 2022 한국농업기계학회 학술발표논문집 Vol.27 No.1
Accurate shuttle vehicle localization in the indoor environment on a precise map enables the mobile robot to estimate its position and orientation while moving in the indoor environment more efficiently. Trajectory tracking control is one of the fundamental techniques influencing a mobile robot's autonomous driving performance. MATLAB and Linux are high-level computers to equip the Inertial Measurement Unit (IMU), Velodyne VLP-16 channels LiDAR, and Encoder Sensors with the mobile robot platform. The mobile robot controls using a Robot Operating System (ROS) enabled robot, setup parameters for the differential wheels, and visualizes sensor data in a ROS robot visualization tool. In this paper, our model presents a new path following a method that integrates the pure pursuit algorithm and the state flow algorithm using the ROS Simulink model. The path following algorithm that performs autonomous waypoint navigation and obstacle avoidance method successfully localized and tested indoor environment. The accuracy improvement is demonstrated through several experimental results.