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Development of Diagnosis Algorithm for Cam Wear of Paper Container Using Machine Learning
김설하(Seolha Kim),장재호(Jaeho Jang),주백석(Baeksuk Chu) Korean Society for Precision Engineering 2019 한국정밀공학회지 Vol.36 No.10
Recently, improvement of productivity of the paper cup forming machine has being conducted by increasing manufacturing speed. However, rapid manufacturing speed imposes high load on cams and cam followers. It accelerates wear and cracking, and increases paper cup failure. In this study, a failure diagnosis algorithm was suggested using vibration data measured from cam driving parts. Among various paper cup forming processes, a test bed imitating the bottom paper attaching process was manufactured. Accelerometers were installed on the test bed to collect data. To diagnose failure from measured data, the K-NN (K-Nearest Neighbor) classifier was used. To find a decision boundary between normal and abnormal state, learning data were collected from normal and abnormal state, and normal and abnormal cams. A few representative features such as mean and variance were selected and transformed to the relevant form for the classifier. Classification experiments were performed with the developed classifier and data gathered from the test bed. According to assigned K values, a successful classification result was obtained which means appropriate failure recognition.
An Automated Tracking System of Fine Dust Generating Spot for Building Dismantlement Sites
김설하(Seolha Kim),김민지(Minji Kim),정희윤(Heeyun Jung),주백석(Baeksuk Chu) Korean Society for Precision Engineering 2019 한국정밀공학회지 Vol.36 No.4
Water spraying work to prevent the dust from scattering during building dismantling operation has usually been done manually. Since it is very risky and often causes fatal accidents due to unexpected collapse, a few countries have adopted mechanical water spaying machines. However, these machines are still operated by human laborer, specifically in orienting the spraying direction, which induces low dust suppression efficiency. In this research, an automated fine dust tracking system was suggested to identify and track the dust generating position accurately. A GPS is installed on the secured body of the excavator which contains a crusher as an end-effector for building dismantlement. Assuming the position of the crusher is the dust generating spot, a forward kinematics analysis is performed to identify the crusher position from the body origin on which the GPS sensor is placed. With another GPS on the water-spraying robot, its relative position to the dust generating spot and its heading angle for tracking can be calculated consequently. Tracking experiments were conducted with a miniature excavator and a reduced size water spraying robot. The results showed a sufficient tracking performance enough to be applied to the water spaying machines.
다품종 종이용기의 고속 생산을 위한 고장 진단 시스템 개발
김설하(Seolha Kim),장재호(Jaeho Jang),주백석(Baeksuk Chu) 한국기계가공학회 2019 한국기계가공학회지 Vol.18 No.5
Recently, as demand for various paper containers has rapidly grown, it is inevitable that paper cup-forming machines have increased their manufacturing speed. However, the faster manufacturing speed naturally brings more frequent manufacturing failures, which decreases manufacturing efficiency. As such, it is necessary to develop a system that monitors the failures in real time and diagnoses the failure progress in advance. In this research, a paper cup-forming machine diagnosis system was developed. Three major failure targets, paper deviation, temperature failure, and abnormal vibration, which dominantly affect the manufacturing process when they occur, were monitored and diagnosed. To evaluate the developed diagnosis system, extensive experiments were performed with the actual data gathered from the paper cup-forming machine. Furthermore, the desired system validation was obtained. The proposed system is expected to anticipate and prevent serious promising failures in advance and lower the final defect rate considerably.
김설하(Seolha Kim),이청화(Cheonghwa Lee),주백석(Baeksuk Chu) Korean Society for Precision Engineering 2020 한국정밀공학회지 Vol.37 No.1
In this study, slip phenomenon that occurs during trajectory tracking motion of an omni-directional mobile robot based on Mecanum wheels was analyzed. Mecanum wheels which generate the omni-directionality to the mobile robot comprise a centered rim wheel and passive sub-rollers. In forward and backward motion, they function like usual wheels to enable rolling along the ground. However, in sideways motion, they create lateral motion of the mobile robot from the rotational actuation using their peculiar structural configuration, during which slip of the sub-rollers occurs. Unnecessary over-slip of the sub-rollers causes tracking errors of the mobile robot motion. To analyze the properties and reasons for the slip phenomenon, squared and circular trajectory tacking experiments were performed. From the experiments, it was observed that sideways motion generated respectively larger tracking errors than forward and backward motion. The geometric analysis regarding the tracking error generation was discussed using the Mecanum wheel structure. Finally, it was confirmed that suspension mechanism to provide four Mecanum wheels of the mobile robot with even reaction forces on the ground is necessary.
Optimal Design and Verification of a Water Spraying Robot for Dust Suppression
김설하(Seolha Kim),주백석(Baeksuk Chu) Korean Society for Precision Engineering 2020 한국정밀공학회지 Vol.37 No.10
In Korea, water spraying to suppress the dust during building dismantling operations has been done manually by human laborers, considered extremely dangerous since it often causes fatal accidents. Abroad, however, water spraying machines have been developed and used in construction sites instead of workers to prevent such serious industrial accidents. In this study, the first domestic water spraying machine is suggested. Since the spraying machine should have a novel dust tracking function, an optimal structure and mechanism should be designed to guarantee its motion performance. The motion for target tracking is achieved by the 2 DOF (Degrees of Freedom) structure comprising a linear and a rotary actuator. Then, the geometric analysis was performed to provide a sufficient kinematic workspace. Through the dynamic performance simulation, the optimal actuator capacities could be selected to generate an appropriate acceleration. The geometric and dynamic performance was evaluated by the extensive motion experiments. With this study, it is expected that an advanced water spraying machine can be developed only with domestic technologies to protect construction laborers from potentially dangerous accidents.
전산유체역학(CFD)을 통한 지중점적관수 장치에 따른 압력강하 분석
김정식(Jeongsik Kim),김필(Phil Kim),김설하(Seolha Kim),김진현(Jinhyun Kim),엄덕호(Dukho Um),이상훈(Sanghun Lee) 대한기계학회 2021 대한기계학회 춘추학술대회 Vol.2021 No.11
Watering crops inside the soil is more efficient in terms of water saving than outside watering. To resolve this problem, we use the drip irrigation system which is used the Drip irrigation pipe. This system can save water by evenly supplying water directly into the roots of the crops. To determine which shape has good pressure drop, this study compares the two commercial Drip irrigation pipe and analyzes experiment and computational values through CFD. For calculation through CFD, the shape of the Drip irrigation pipe was produced in CAD based on actual measurement and calculated through ANSYS. Experiment used a water pump and was measured every 20 kPa in the range from 100 to 400 kPa.. This paper reports the advantages and disadvantages of both Drip irrigation pipes.