• Journal of the Korean Society of Marine Environment & Safety
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• v.13 no.3
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• pp.229-234
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• 2007

Currently offshore fisheries are one of shrinking industries and fishermen are getting older. Moreover it is difficult to work fisheries for decreasing fishermen as the time goes. Two people per a boat work together at least for proper fisheries. If the unskilled fisherman boards on boat, it will make some troubles to speak each other and diminish the efficiency of working because one person should control the boat. So it need to study the remote control system for leasure and outboard engine that can control and work at the same time. The remote control system is consisted of engine, steering gear and forward reverse neutral gear controls. These three controls are made by position and speed control using DC motor, and microcontroller is used to control the engine speed and rudder angle. This system can be controled and worked alone and we tested the system at sea and confirmed that the system works properly.

• Journal of the Korean Institute of Intelligent Systems
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• v.22 no.6
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• pp.780-785
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• 2012

Wind energy is currently the fastest growing source of renewable energy used for electrical generation around the world. Generally, wind turbine systems are designed to be operated for twenty years long, Therefore, various faults in the wind turbine system inevitably occur during their long term period of operation. Especially, rotor shaft, gear-box and generator are installed inside of nacelle, furthermore, some cooling systems for normal operation of these devices are also required. If these cooing systems have failed in their operation, it is impossible for the entire system to be operated normally. In this work, IR(Infra Red) camera based fault detection system for the preventive detection of various cooling systems faults is proposed. To verify the applicability of the proposed system, physical implementation is embodied and various experiments are carried out.

• The Journal of the Acoustical Society of Korea
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• v.38 no.5
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• pp.543-548
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• 2019

The tonal signal caused by the machinery component of a vessel such as an engine, gearbox, and support elements, can be modeled as a sparse signal in the frequency domain. Recently, compressive sensing based techniques that recover an original signal using a small number of measurements in a short period of time, have been applied for the tonal frequency detection. These techniques, however, cannot avoid a basis mismatch error caused by the discretization of the frequency domain. In this paper, we propose a method to detect the tonal frequency with a small number of measurements in the continuous domain by using the atomic norm minimization technique. From the simulation results, we demonstrate that the proposed technique outperforms conventional methods in terms of the exact recovery ratio and mean square error.

• Journal of Broadcast Engineering
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• v.27 no.6
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• pp.885-896
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• 2022

Motor failure in manufacturing plays an important role in future A/S and reliability. Motor failure is detected by measuring sound, current, and vibration. For the data used in this paper, the sound of the car's side mirror motor gear box was used. Motor sound consists of three classes. Sound data is input to the network model through a conversion process through MelSpectrogram. In this paper, various methods were applied, such as data augmentation to improve the performance of classifying fault motors and various methods according to class imbalance were applied resampling, reweighting adjustment, change of loss function and representation learning and classification into two stages. In addition, the curriculum learning method and self-space learning method were compared through a total of five network models such as Bidirectional LSTM Attention, Convolutional Recurrent Neural Network, Multi-Head Attention, Bidirectional Temporal Convolution Network, and Convolution Neural Network, and the optimal configuration was found for motor sound classification.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.38 no.11
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• pp.915-924
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• 2014

In an aero gas-turbine engine, a surface air-oil heat exchanger (SAOHE) is used to cool the oil system for the gearboxes and electric generators. The SAOHE is installed inside the fan casing of the engine in order to dissipate the heat from the oil system into the bypass duct stream. The purpose of this study was to develop an effective numerical method for designing an SAOHE for an aero gas-turbine engine. A two-dimensional model using a porous medium was developed to evaluate the aero-thermal performance of the fins of the heat exchanger, and a one-dimensional flow and thermal network program was developed to save time and cost in the evaluation of the heat exchanger performance. Using this network program, the pressure drop and heat transfer performance of the heat exchanger were predicted, and the results were compared with two-dimensional computational fluid dynamics results and experiment data for validation.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.06a
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• pp.1096-1101
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• 2000

In machine tools, often a gearbox is installed to control the rotating speed of spindle, which sometimes generates problems of noise and vibration due to errors in tooth-meshing. In this study, the characteristics of, noise and vibration of given gearbox for a machine tool are analyzed experimentally. From the measurement, it was observed that the tooth-meshing component of the sound pressure level from the gearbox took its maximum at a specific operational speed. Therefore, the main content of this study is to investigate the reason why the above mentioned characteristics are observed. By investigating the natural frequencies of the components in gearbox, it was found that the natural frequencies of the rotating gear-shaft and gearbox for twisting mode were closely related to the first and second peak of sound pressure levels respectively. Thereform, in this study, those relations were identified by the impact test of rotating gear-shaft and-gearbox. In addition, we inserted the rubber between housing and bed, and analyze the effect of the rubber insertion on noise reduction by Operational Deflection Shapes.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.5
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• pp.507-515
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• 2015

This study was conducted to develop and verify a torque application device for use in a mechanical power-circulation test rig for 5.5 MW wind turbine gearboxes. The design and analysis of the torque application device was conducted. In addition, the torsional stiffness of the test rig was calculated using the rotational angle measurements for each of the components. The calculated stiffness of the test rig was $231.13kN{\cdot}m/rad$ for a clockwise torque application. The rated torque can be applied when the stiffness of the gearbox is greater than $1,064,400kN{\cdot}m/rad$ for a clockwise torque application. Because of the limited rotational angle of the test rig, the potential application of the rated torque is determined according to the torsional stiffness of the test gearbox.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.19 no.7
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• pp.52-59
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• 2020

Automatic tool changers (ATCs) can be divided into drum and chain types. Drum-type ATCs contain a magazine, where the tools are mounted, and a cam gearbox, which swaps the tools via roller gear and grooved plate cams. Drum-type ATCs are advantageous in that the operating time for the tool magazine is more rapid than that of chain-type ATCs and the length of the unit is shorter. Thus, drum-type ATCs can be fabricated into various shapes and forms depending on the number of tools and the magazine size in accordance with machining center requirements and consumer demand. In particular, the price competitiveness of a machining center with a drum-type ATC is higher, while drum-type ATCs are more rigid with fewer parts, possibly reducing the need for regular servicing. This study aims to verify the structural stability and design validity of the magazine base, which is the main structure of a drum-type ATC, using finite element analysis. This study kinematically verifies the specifications of the selected drive motor and reducer and assessed the design of the cam gearbox. It also conducts a structural analysis of the roller camp, which is the core component of the cam gearbox, based on the results of the kinetodynamic analysis, thus validating the structural design.

• Journal of Energy Engineering
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• v.23 no.1
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• pp.46-57
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• 2014

This study analyzes whether the value-added structure of Korean wind power industry exhibits a virtuous cycle through the value chain(VC) within wind power firms and the value system(VS) among the wind power industries, using a regression analysis based on a survey about Korean wind power companies. According to the VC, the government's R&D support is analyzed to have contributed to an increase in the R&D investments of the wind power companies. An increase in corporates' R&D investments has led to an increase in corporates' R&D outputs, and in turn, induced a remarkable increase in the amounts of production. But an increase in production has not led to a decrease in the costs of production, not resulting in an increase in profit rates per sales amount. In addition, while an increase in profit rates is analyzed to have contributed to an increase in production, this did not induce further investments in corporate's R&D. The virtuous cycle of the value chain in Korean wind power firms is, therefore, analyzed to be weak. Next, the VS is analyzed by dividing the whole chain into the system group including rotor blades, gear boxes, and power generators, and the structure group, such as towers. Two groups are analyzed to have mutually positive effects in the processes of the government's support for corporates' R&D, corporates' investment in R&D, R&D outputs, and profit rates per sales amount. Such mutual positive effects are, however, not found in the processes of the amounts of production and the costs of production. These results demonstrates that the value system of Korean wind power industry is not completed. This study has a policy implication to need further efforts to create the virtuous cycle in the VC and VS of Korean wind power industry.