• Journal of the Korean Society of Manufacturing Process Engineers
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• v.20 no.9
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• pp.28-34
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• 2021

The Fourth Industrial Revolution has led to the development of drones for commercial and private applications. Therefore, the malfunction of drones has become a prominent problem. Failure mode and effect analysis was used in this study to analyze the primary cause of drone failure, and blade breakage was observed to have the highest frequency of failure. This was tested using a vibration sensor placed on drones along the breakage length of the blades. The data exhibited a significant increase in vibration within the drone body for blade fracture length. Principal component analysis was used to reduce the data dimension and classify the state with machine learning algorithms such as support vector machine, k-nearest neighbor, Gaussian naive Bayes, and random forest. The performance of machine learning was higher than 0.95 for the four algorithms in terms of accuracy, precision, recall, and f1-score. A follow-up study on failure prediction will be conducted based on the results of fault diagnosis.

• Journal of the Korean Association of Geographic Information Studies
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• v.26 no.4
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• pp.97-115
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• 2023

In recent years, the structure of the population has been changing rapidly, with a declining birthrate and aging population, and the inequality of population distribution is expanding. At this point, changes in population estimation methods are required, and more accurate estimates are needed at the subregional level. This study aims to estimate the population in 2040 at the 500m grid level by applying an explainable machine learning to Busan in order to respond to this need for a change in population estimation method. Comparing the results of population estimation by applying the explainable machine learning and the cohort component method, we found that the machine learning produces lower errors and is more applicable to estimating areas with large population changes. This is because machine learning can account for a combination of variables that are likely to affect demographic change. Overestimated population values in a declining population period are likely to cause problems in urban planning, such as inefficiency of investment and overinvestment in certain sectors, resulting in a decrease in quality in other sectors. Underestimated population values can also accelerate the shrinkage of cities and reduce the quality of life, so there is a need to develop appropriate population estimation methods and alternatives.

• Proceedings of the KIEE Conference
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• 1994.07a
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• pp.479-481
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• 1994

A direct vector control system of induction machine based determination of the spatial position of the airgap flux from the third harmonic component of the stator voltage is presented in this paper. The Rotor flux, necessary in direct vector control system, is estimated with the stator current and the airgap flux acquired from the third harmonic component of the stator voltage. And it will be used as an important information to implement the vector control system of the induction motor drive.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.05a
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• pp.535-539
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• 2001

In these days. the finite element method(FEM) is a very common method for not only a simple vibration analysis but also the optimization of structures. Since the finite element model may contain thousands of degree of freedom, the eigensolutions require extreme computing power, which will result in a serious time-consuming problem. Thus, many researchers have challenged to find more improved modeling techniques and calculating methods to overcome such problems. The Guyan reduction method and the substructure synthesis method are typical examples of such methods. Of the substructure synthesis method, the component mode synthesis method (CMS) is widely used for dynamic analysis of structure. In this study. for the efficient analysis of jet loom structure. Component Mode Synthesis was carried out. The results of the finite element program developed are compared with those of the commercial package program ANSYS for the validation of the program. The results obtained by the program showed a good agreement with those of ANSYS. The program will be further refined and verified by test to yield more accurate results.

• Journal of the Korean Society for Precision Engineering
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• v.20 no.8
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• pp.101-107
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• 2003

A new mechanical probe for 3-D feature measurement on coordinate measuring machines (CMMs) is presented. The probe is composed of the contact stylus and the three-component force sensor. With the stylus mounted on the force sensor, the probe can not only measure 3-D features, but also detect contact force acting on the stylus tip. Furthermore, the probing direction and the actual contact position can be determined by the relationship among three components of contact force to be detected. In this paper, transformation matrix representing the relationship between the external force acting on the stylus tip and the output voltages of measurement gauges is derived and calibrated. The prototype of probe is developed and its availability is investigated through the experimental setup for calibration test of the probe. A series of experimental results show that the proposed probe can be an effective means of improving the accuracy of touch probing on CMM.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 1999.10a
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• pp.307-314
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• 1999

By using AIP(Arc Ion Plating) of a physical vapor deposition for the first time in Korea a ceramic tool whose surface is coated single layeredly with TiN is developed. In addition, cutting resistance appearing in the process of finishing cut of hardened carbon tool steel, STC3 is studied. The principal and radial components of cutting resistance in those cutting conditions appear to be the same or similar, and the feed component is relatively small. The feed component is found to be in proportion to cutting width, and the radial component in proportion to cutting thickness. Owing to coating the cutting resistance of a TiN coated ceramic tool increases compared with that of a general ceramic tool.

• Journal of the Semiconductor & Display Technology
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• v.10 no.1
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• pp.113-118
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• 2011

This paper proposes computer visual inspection algorithms for PCB defects which are found in a manufacturing process. The proposed method can detect open circuit and short circuit on bare PCB without using any reference images. It performs adaptive threshold processing for the ROI (Region of Interest) of a target image, median filtering to remove noises, and then analyzes connected components of the binary image. In this paper, the connected components of circuit pattern are defined as 6 types. The proposed method classifies the connected components of the target image into 6 types, and determines an unclassified component as a defect of the circuit. The analysis of the original target image detects open circuits, while the analysis of the complement image finds short circuits. The machine vision inspection system is implemented using C language in an embedded Linux system for a high-speed real-time image processing. Experiment results show that the proposed algorithms are quite successful.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.9 no.5
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• pp.157-164
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• 2000

A machine tool generally has some serious stability problems in the form of tool chatter during the cutting process. Chatter vibration deteriorates the surface finish, reduce tool and machine life, accelerates machine tool system component wear, and may lead to an unacceptable noise sound in the working environment. In this study, the behavior of spectral density of AE signal and principal cutting force signal in order to monitor the chatter vibration in the cutting process has been investigated. From the results, the reliability of proposed monitoring method has been confirmed.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.10a
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• pp.1070-1073
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• 2004

This paper is on the development of a system for removing membranes which is designed exclusively for aircraft components. Membrane removal solution is a most critical issue in aerospace industries since a method of manufacturing the components tends to be changed from fabrication of many parts to cutting into one body. The cutting method inevitably produces a huge amount of chips and then membranes remain in the body. The membrane removal process, as a result, becomes an important issue since it is directly related to productivity. We tried to develop a new machine which will replace the conventional method that uses a handy tool. The machine has been designed for a cutting tool set to follow the unique shape of the slot in the body by a cam follower and cut the membrane automatically. The design has been checked by structural analysis: stress and vibration analysis. A prototype test has been finished. This paper summarizes a series of development process of the deburring machine and some design issues are discussed.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1995.10a
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• pp.1009-1012
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• 1995

This paper presents an example of the development of motor drives for machine tools. Machine tools need motor drives with high control precision and performance. We developed a motor drive system that meets these requirements. The converter, the one component of drive system, adopts modular structure and high DC-link voltage. The drive which consists rest part of drive system is developed based on TMS320C32 DSP and state-of-the-art circuit technology. In this paper each developed parts are described in terms of its structure, specification and features.