• Transactions of the Korean Society of Mechanical Engineers B
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• v.39 no.2
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• pp.183-190
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• 2015

An ejector is a type of non-powered pump that is used to supply a secondary flow via the ejection of a primary flow. It is utilized in many industrial fields, and is used for fueling the vehicle because of less failures and simple structure. Since most of ejectors in industry are gas-to-gas and liquid to gas ejector, many research activities have been reported in optimization of gas ejector. On the other hand, the liquid ejector is also applied in many industry but few research has been reported. The liquid ejector occurs cavitation, and it causes damage of parts. Cavitation has bees observed at the nozzle throat at the specified pressure. In this study, a two-dimensional axisymmetric simulation of a liquid-liquid ejector was carried out using five different parameters. The angle of the nozzle plays an important role in the cavitation of a liquid ejector, and the performance characteristics of the flow ratio showed that an angle of $35^{\circ}$ was the most advantageous. The simulation results showed that the performance of the liquid ejector and the cavitation effect have to be considered simultaneously.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.7
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• pp.270-276
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• 2020

3D printing is an additive manufacturing technology that can produce complex shapes in a single process for a range of materials, such as polymers, ceramics, and metals. Recent 3D printing technology has developed to a level that enables the mass-production through an improvement of the printing speed and the continuous development of applicable materials. In this study, 3D printing technology using a laser was applied to manufacture a heat exchanger for an air compressor in a railway vehicle. First, the optimal design of the heat exchanger was carried out by focusing on weight reduction and compactness as a shape suitable for 3D printing. Based on the design derived, heat exchanger prototypes were made of AlSi10Mg alloy material by applying the SLM technique. Moreover, the manufactured prototypes were attached to an existing air compressor, and the heat exchange performance of the compressed air was tested. The test results of the 3D printed prototypes showed a heat exchange performance of approximately 80% and 85% at low and high-pressure, respectively, compared to the existing heat exchanger. From the 𝓔-NTU method results with an external cooling air condition similar to that of the existing heat exchanger, the calculated heat transfer amount of 3D printed parts showed similar performance compared to the existing heat exchanger. As a result, the 3D printed heat exchanger is lightweight with good performance.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.3
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• pp.209-214
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• 2017

Most of the present potential transformers of train vehicles are of the oil-type filled with insulating oil and are susceptible to problems such as explosion due to the increase in the internal pressure during train operation and poor reliability near the end of their life cycle. As a solution to this problem, it is necessary to develop a molded dry-type potential transformer with excellent pressure-resistance performance using insulating resin. In order to localize the product, the Korea Railroad Research Institute has been developing a molded dry-type potential transformer. As part of this research, it is necessary to analyze the vibration characteristics of the developed product and to check the transformer performance in a vibration environment. In this study, a resonance test and simulated long-term life test of the developed product were conducted according to the KS R 9144 and IEC 61373 standards, respectively, which are vibration test methods for railway vehicle parts. Their natural frequencies were analyzed by comparing the results of the numerical modal analysis and resonance test, in order to confirm their adherence to the standards. Also, the performance test after the simulated long-term life test confirmed that the operation of the developed transformer was not problematic even in a long-time vibration environment.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.2
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• pp.219-226
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• 2010

The stamping process is widely used in fabricating various sheet-parts for vehicle, airplane, and electronic devices due to its low processing cost and high productivity. Recently the use of thin sheets with corrugated structures has rapidly increased for the production of energy devices, e.g., heat exchangers and fuel cells. However, it is very difficult to make corrugated structures directly in the stamping process due to their geometrical complexity. To solve this problem, this paper proposes a multi-step stamping process with a combined heat treatment process: a sequence of the first stamping, heat treatment, and second stamping. By multi-stamping, we obtained successful results in fabricating very thin corrugated structures with thicknesses of $100{\mu}m$; these are applicable as part of a plate-type heat exchanger.

• Journal of IKEEE
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• v.24 no.2
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• pp.638-648
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• 2020

Currently, the method of user-follwoing in intelligent cooperative robots usually based in vision system and using Lidar is common and have excellent performance. But in the closed space of Corona 19, which spread worldwide in 2020, robots for cooperation with medical staff were insignificant. This is because Medical staff are all wearing protective clothing to prevent virus infection, which is not easy to apply with existing research techniques. Therefore, in order to solve these problems in this paper, the ultrasonic sensor is separated from the transmitting and receiving parts, and based on this, this paper propose that estimating the user's position and can actively follow and cooperate with people. However, the ultrasonic sensors were partially applied by improving the Median filter in order to reduce the error caused by the short circuit in communication between hard reflection and the number of light reflections, and the operation technology was improved by applying the curvature trajectory for smooth operation in a small area. Median filter reduced the error of degree and distance by 70%, vehicle running stability was verified through the training course such as 'S' and '8' in the result.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.06a
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• pp.263-268
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• 2000

In this paper, a new indirect feedback active noise control (ANC) scheme based on the fundamental frequency estimation is proposed for systems with a harmonic noise. When reference signals necessary for feedforward ANC configuration is difficult to obtain, the conventional ANC algorithms for multi-tonal noise do not measure the reference signals but generate them with the estimated frequencies. However, the beating phenomena, in which certain frequency components of the noise vanish intermittently, may make the adaptive frequency estimation difficult. The confusion in the estimated frequencies due to the beating phenomena makes the generated reference signals worthless. The proposed algorithm consists of two parts. The first part is a reference generator using the fundamental frequency estimation and the second one is the conventional feedforward control. We propose the fundamental frequency estimation algorithm using decision rules, which is insensitive to the beating phenomena. In addition, the proposed fundamental frequency estimation algorithm has good tracking capability and lower variance of frequency estimation error than that of the conventional cascade ANF method. We are also able to control all interested modes of the noise, even which cannot be estimated by the conventional frequency estimation method because of the poor SIN ratio. We verify the performance of the proposed ANC method through simulations for the measured cabin noise of a passenger ship and the measured time-varying engine booming noise of a passenger vehicle.

• Journal of the Korea Convergence Society
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• v.9 no.9
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• pp.31-39
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• 2018

In this paper, we proposed a license plate detection method based on contour extraction that adapts to environmental changes. The proposed method extracts contour lines using DoG (Difference of Gaussian) to remove unnecessary noise parts in the contour extraction process. Binarization was applied in ugly outline images, and erosion and dilation operations were used to emphasize the contour of the character part. Then, only the outline of the ratio of the characters of the plate was extracted through the ratio of the width and height of the characters. And the case where the outline is the longest is estimated by estimating the characters of the license plate. For the experiment, we applied 130 image data to license plate on the front of the vehicle, oblique environment, and environment images with various backgrounds. I also experimented with motorcycle images of different license plate patterns. Experimental results showed that the detection rate of the oblique image was 93% and that of the various background environment was 70% in the motorcycle image but 98% in the front image.

• Journal of KSNVE
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• v.10 no.6
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• pp.1059-1066
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• 2000

In this paper. a new indirect feedback active noise control (ANC) scheme barred on the fundamental frequency estimation is proposed for systems with a harmonic noise. When reference signals necessary for feedforward ANC configuration are difficult to obtain, the conventional ANC algorithms for multi-tonal noise do not measure the reference signals but generate them with the estimated frequencies.$^{(4)}$ However, the beating phenomena, in which certain frequency components of the noise vanish intermittently, may make the adaptive frequency estimation difficult. The confusion in the estimated frequencies due to the beating phenomena makes the generated reference signals worthless. The proposed algorithm consists of two parts. The first part is a reference generator using the fundamental frequency estimation and the second one is the conventional feedforward control. We propose the fundamental frequency estimation algorithm using decision rules. which is insensitive to the beating phenomena. In addition, the proposed fundamental frequency estimation algorithm has good tracking capability and lower variance of frequency estimation error than that of the conventional cascade ANF method.$^{(4)}$ We are also able to control all interested modes of the noise, even which cannot be estimated by the conventional frequency estimation method because of the poor S/N ratio. We verify the performance of the proposed ANC method through simulations for the measured cabin noise of a passenger ship and the measured time-varying engine booming noise of a passenger vehicle.

• Journal of the Korean Magnetics Society
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• v.25 no.6
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• pp.189-197
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• 2015

As enforced the regulation of fuel efficiency, the electrification of automotive components in internal combustion vehicle has been applied instead of hydraulic pressure. A typical example of such parts is the EPS (electric power steering), and it is applied to most automotive at present. In electric power steering system, the core component is motor. The reduction of cogging torque and torque ripple is required to improve steering feeling and reduce NVH (Noise Vibration Harshness) in EPS. Generally the skewed design of stator or rotor is applied in order to reduce cogging torque and torque ripple. This paper propose the design and analysis methodology of Brusheless PMSM (Permanent Magnet Synchronous Motor) which is applied to skewed stator. The proposed methodology is as follows: First Intial Design PMSM with skewed stator for EPS, Second Optimal design using RSM (Response surface method), Third Performance Analysis such as Phase Back EMF, Inductance, Load torque using FEA (Finite Element Method). Finally, the reliability of proposed design methodology will be verified through the experiments of prototype sample.

• Journal of Digital Convergence
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• v.14 no.12
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• pp.73-84
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• 2016

The purpose of this study is to examine the global value chain of the global automotive industry to investigate the success factors through the example of the value chain of Hyundai Motor. It looks at the value chain of the well-known Korean automaker, Hyundai Motor, to find success factors with cases. It examines the process to build the supply chain of Hyundai Motor to analyze what impact it has on the growth of Hyundai Motor to look closely at the vertical division of labor of vehicle parts manufacturers. Korea's automobile industry has been expanding cooperation between two sectors as a multifunctional promotion focusing on electronic communications technology in machinery and technology center. Through introducing the nation's first vertical integration in the sector, Hyundai Motor has secured competitiveness of cost reduction and prestige car production. Hyundai Motor has operated and established factories in the United States, India, Turkey, the Czech Republic, Russia, and Brazil. Hyundai Motor operates 51 affiliates, such as Hyundai Mobis, by restructuring, mergers and acquisitions, and building their own vertical division of labor around it. Hyundai Motor has been overcoming dependence on foreign modules businesses and maintaining the supply value chain around Hyundai Mobis.